Journal of Experimental Marine Biology and Ecology, 2015
Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-of... more Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-off from agriculture and forestry has increased the number of large-scale and chronic impacts affecting coastal and estuarine systems. The need to assess cumulative impacts is a major motivation for the current desire of managers and ecologists to define ecosystem “health” and “stress”. A number of univariate metrics have been proposed to monitor health, including indicator species, indicator ratios and diversity or contaminant metrics. Alternatively, multivariate methods can be used to test for changes in community structure due to stress. In this study we developed Multivariate Models using statistical ordination techniques to identify key stressors affecting the ‘health’ of estuarine macrofaunal communities. Macrofaunal and associated environmental samples were collected across 75 sites from within Tauranga Harbour, a large estuary located on New Zealand’s North Island. The harbour receives discharges from urbanized, industrial, agricultural and horticultural catchments. Distance-based linear modelling identified sediments, nutrients and heavy metals as key ‘stressors’ affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The multivariate models were found to be more sensitive to changing environmental health than simple univariate measures (abundance, species richness, evenness and Shannon-Wiener diversity) along an anthropogenic stress gradient. This multivariate approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state. Ultimately, such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat change and should enable long term degradative change from multiple disturbances to be assessed.
Abstract. Before-After Control Impact (BACI) sampling designs are commonly used in environmental ... more Abstract. Before-After Control Impact (BACI) sampling designs are commonly used in environmental impact assessment and are considered themost effective for detecting changes due to anthropogenic disturbances. These designs handle local spatial variability through randomized placement of samples into a treatment stratum and a control stratum. When a contaminant disperses with distance from a point source it is suggested that a ‘gradient’ design will be more sensitive to change than randomized
placement of samples. This requires allocating samples according to distance, rather than by random placement within randomly placed blocks. In this paper gradient versus random sampling designs were compared using data from an oil field in the North Sea. The gradient sampling design was more powerful than a randomized CI sampling design.
Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a usefu... more Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a useful way of providing strong empirical evidence of natural or anthropogenic disturbance. Gradient designs for environmental assessment are sensitive to change for point source data, enabling the scale of the effects of a disturbance to be readily identified. If the spatial scale that is sampled fromthe point source is adequate, problems of selecting control sites can be avoided. However, sources of spatial variation in macrobenthic communities, which are not related to the impact, can confound the use of gradient designs. This can occur if the natural spatial structure overlaps that of the gradient and cannot be identified either as a location or environmental covariable. The ability to detect point source impacts using a gradient design against natural spatial variability was tested using benthic macrofaunal data collected from Manukau Harbour, New Zealand. Treated sewage wastewater is discharged into the north-west area of the Manukau Harbour. Sandflats in the vicinity of the outfall are also subject to physical disturbance from wind-waves and strong tides. Ordination techniques and the testing of apriori predictions were used to try and separate the relative effects of organic and physical disturbance on the benthic communities. While the occurrence of other environmental disturbances along a gradient of anthropogenic disturbancemakes interpretation of community pattern more difficult, the use of a gradient sampling layout, ordination analysis and the testing of a priori predictions enabled impacts of the anthropogenic and natural environmental disturbances to be interpreted. Gradient designs, therefore, provide a method of assessing complex impacts that operate over broad spatial and temporal scales.
ABSTRACT: Broad-scale anthropogenic disturbances that reduce the density of epifauna and
homogen... more ABSTRACT: Broad-scale anthropogenic disturbances that reduce the density of epifauna and
homogenise surficial sediments can have important consequences for seafloor biodiversity. We inves-
tigated the habitat structure and macrofaunal diversity of relatively simple soft-sediment habitats
over a number of spatial scales (cm to km) to identify the role of habitat structure in influencing mac-
robenthic diversity and to assess the validity of using habitat structure as a surrogate measure for bio-
diversity. We sampled 10 locations with differences in habitat structure using a sampling design that
nested macrobenthic core samples within videoed transects of the seafloor. This allowed us to deter-
mine relationships between observable habitat structure and macrobenthic diversity at a number of
spatial scales. We characterised elements of habitat structure based on direct counts of surficial sedi-
ment characteristics and the presence of other immobile features, many of which were biogenic in
origin. We also used multivariate measures (the relative multivariate dispersion, the mean and range
of the Bray-Curtis dissimilarity along the transects) to characterise habitat structure at the transect
scale. We developed regression models based on measures of habitat structure that explained 74 to
86% of the variance in macrobenthic diversity. This result suggests that removal of habitat structure
in relatively low-structure soft-sediment systems will significantly decrease their biodiversity, and
consequently that of the wider marine ecosystem.
Journal of Experimental Marine Biology and Ecology, 2002
The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common
i... more The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common
in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be
influenced by suspended sediment loads. We conducted a laboratory experiment to determine the
effect of short-term elevations in turbidity levels, such as those commonly recorded during storms,
on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a
3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment
load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold
suspended sediment concentration, and Atrina physiological condition at the end of this experiment
was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after
exposure to elevated levels for only 3 days. The field survey and transplant experiment provided
empirical evidence of a strong, negative effect of increasing suspended sediment flux on the
physiological condition of Atrina. We suggest that relationships between the physiological condition
of suspension feeders and sediment settling flux could provide a link between sediment inputs, which
commonly occur as a result of catchment runoff during rainfall events, and the ecological health of
estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural
distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale
functional and structural effects on benthic communities in estuarine and coastal areas with high rates
of sedimentation.
Sediment run-off from land has been recognised as a threat to the biodiversity of shal-
low estu... more Sediment run-off from land has been recognised as a threat to the biodiversity of shal-
low estuarine and coastal areas. Extreme rainfall events can cause flooding and landslides, which
may result in rapid deposition of fine terrigenous sediments and have serious impacts on benthic
communities. We designed a field experiment to study the response of intertidal benthos to such
depositions of terrigenous clay. The experiment was conducted at 2 contrasting intertidal sites: a
sheltered muddy sand habitat and an exposed sand habitat influenced by wind waves. Terrigenous
clay (50% water content) was deposited in replicated experimental plots (2 m diameter) at each site
in layers 0, 3, 6 or 9 cm thick. The initial response of the resident macrofauna and subsequent
recolonisation was monitored over a period of 408 d. Physical and chemical properties of the experi-
mental plots and wave climate at each site were also measured. The experiment demonstrated highly
deleterious effects of catastrophic terrigenous clay deposition on estuarine macrobenthic communi-
ties. At both sites following clay deposition, the numbers of individuals were reduced by more than
50% after 3 d and by more than 90% after 10 d, irrespective of clay thickness. Mud crabs Helice
crassa were the only animals able to emerge through the clay layer. They also exhibited elevated
densities in clay treatments over the course of the experiment. After 28 d, a storm occurred (maximum
wave height 0.4 m, period = 6 s) which dispersed the clay deposits at the exposed sandy site.
Recolonisation of the surficial sediments was rapid at the exposed site following this wind-wave dis-
turbance. However, deeper-dwelling animals such as large bivalves had not recovered to levels
observed in the control plots by the end of the experiment. At the more sheltered muddy sand site,
the clay deposition resulted in long-lasting habitat change; Although the clay was gradually broken
up and re-colonised by small crabs and surface dwelling macrofauna, recovery was still incomplete
408 d after deposition. The results emphasise the role of wind-wave disturbance and transport of
sediments and macrofauna with bedload, and the importance of bioturbation by crabs as facilitators
of macrobenthic recovery after disturbance.
There is a growing threat of habitat change in estuarine and coastal regions, yet there
are few ... more There is a growing threat of habitat change in estuarine and coastal regions, yet there
are few models that enable ecologists and resource managers to forecast the response of macrofaunal
species to long-term changes in sediment type. This study details a novel strategy that enabled us to
rapidly collect data on macrofaunal densities and sediment characteristics by sampling mud-to-sand
transition zones in 19 estuaries. Species-specific models that predict probability of occurrence rela-
tive to sediment mud content were developed for 13 common macrofaunal species. However, the
roles played by many macrofaunal species are influenced by density, not just occurrence. Over broad
spatial scales, the constraint an environmental variable places on density can be represented by the
upper (or lower) limit on density. Thus, the distribution of maximum density along the gradient from
mud to sand was modelled as another indicator of a species’ preference. Both the maximum and min-
imum values for number of taxa, number of individuals, Shannon-Wiener diversity and taxonomic
distinctness were also modelled. For most variables, good models (r2
> 0.6) were developed. The mod-
els developed for the different species exhibited a wide variety of functional forms, highlighting the
potential variation in response to habitat change even for closely related species with similar natural
history characteristics. Probability-of-occurrence models and maximum-density models for a specific
species also varied in functional form, emphasising that changes in both occurrence and density need
to be considered when predicting likely responses to changes in habitat.
In New Zealand, one species of mangrove, Avicennia marina var. australasica, forms a
characteri... more In New Zealand, one species of mangrove, Avicennia marina var. australasica, forms a
characteristic and often an extensive feature of the tidal mudflats of harbours and estuaries. Within
their natural range, mangroves have generally increased in abundance in New Zealand over the last
100 yr in response to increased sedimentation associated with concurrent changes in catchment land
use. However, little information is available about the ecological consequences of changes in the ex-
tent of mangrove habitats under varying sedimentation regimes. We therefore conducted a study to
determine the effects of high sedimentation rates on mangrove plant communities and associated ben-
thic community composition. We selected an estuary that is experiencing high rates of sedimentation
(as high as 23 mm yr–1
) and associated increases in mangrove area. We recorded clear differences in
both plant and benthic communities along a gradient of decreasing sedimentation. Mangrove archi-
tecture (such as height and density of plants) and health (as measured by chlorophyll a fluorescence)
were linked to high mud content of the sediment and elevated sedimentation patterns. Mangrove
plants at the upper landward sites, characterised by a high percentage of mud and high total nutrients
(total phosphorus [TP] and total nitrogen [TN]) and organic content, were taller than those at the sea-
ward sites and had a larger number of pneumatophores as well as the greatest number of new
seedlings. However, benthic macrofaunal diversity and abundance within the mangrove habitats were
lower than expected, and clear functional differences were found between habitats with differing sed-
imentation patterns. Sites with high sedimentation rates had lower numbers of suspension feeders, low
macrobenthic diversity, and were dominated by deposit-feeding polychaetes and oligochaetes. The
diversity and density of benthic macrofaunal communities was, however, lower than that of sandflat
communities for both mangrove habitats and adjacent intertidal mudflats in these sheltered areas,
suggesting a response to the increased silt/clay from sedimentation rather than to the mangroves
themselves. Our study demonstrates the potential for functional and structural effects on benthic
communities on a larger spatial scale in estuarine areas experiencing high rates of sedimentation.
Journal of Experimental Marine Biology and Ecology, 2008
Using modern computer based search engines we were able to assemble, review, and document the ris... more Using modern computer based search engines we were able to assemble, review, and document the rise of
the concept of scale in benthic ecology. In the early literature the term appears to have been most commonly
used to verbally qualify a result as being found at a particular spatial scale. However we document a shift
from verbal expression to quantitative methods that explicitly incorporate scale into the design of the study.
Examples include the development of nested multi-scale studies and experiments conducted over large
spatio-temporal scales at the level of estuary or region. We also review novel methods for assessing scale
effects in benthic ecosystems. First, gradient or correlative study designs have been developed in order to
assess spatial and temporal heterogeneity in benthic ecosystems. These designs involve the careful selection
of study site locations along gradients, or recommend nesting small-scale experiments within a broad-scale
correlative framework. Secondly, we briefly assess the development of statistical analytical techniques to
analyze spatial data and formal mathematical techniques for scaling functional relationships.We believe that
the design and analytical advances identified in this review provide a framework for ecologists to address
pressing large-scale questions.
ABSTRACT: This review paper identifies the main effects of oil and gas drilling waste on benthic
... more ABSTRACT: This review paper identifies the main effects of oil and gas drilling waste on benthic
environments. We identified 26 papers and technical reports that surveyed sediment samples from
72 production or exploration platform sites to assess the zone of influence of sediment contamina-
tion and biological effects on benthic communities. While oil-based fluids are now rarely used in
the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time
scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as
determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based
fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abun-
dance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in
benthic species diversity, abundance and alterations to community structure. Functional changes
included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In
general, this review demonstrates a loss of benthic biodiversity and suspension-feeding commu-
nities due to oil exploration and production and the potential for large-scale effects on sensitive
communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities
are identified.
Research on ecosystem services has grown exponentially during the last decade. Historically, many... more Research on ecosystem services has grown exponentially during the last decade. Historically, many studies of marine and coastal ecosystem services (MCES) were specific to commercial fisheries or focused on single habitats such as mangroves, coastal wetlands and coral reefs. International and regional policy requirements have identified the need for spatially explicit MCES information at regional scales. In many marine regions, however, the absence of necessary information on the spatial distribution of ecological components remains a significant data gap that can prevent future progress on mapping MCES. As part of a recently funded multidisciplinary program, we have developed frameworks to quantify, spatially map and determine the ‘total economic value’ of MCES for multiple habitat types. The research is being conducted within a case study embayment at the top of the South Island of New Zealand. We have used data-driven and principles-based approaches to map both functional habitats...
There is a growing need to predict ecological responses to long-term habitat change. However, sta... more There is a growing need to predict ecological responses to long-term habitat change. However, statistical models for marine soft-substratum ecosystems are limited, and consequently there is a need for the development of such models. In order to assess the utility of statistical model- ling approaches for predicting likely changes in species distributions under varying environmental conditions, we tested the utility of logistic modelling and classification approaches. We successfully developed models relating the presence/absence of common intertidal macrofauna to changing envi- ronmental variables such as sediment characteristics, depth/elevation, tidal currents and wind-wave (i.e. wind-generated wave activity) disturbance. The final model for each species contained between 1 and 6 variables, where the percentage correctly predicted was moderate to high, ranging from 59 to 97%. We were also able to identify relationships between higher level variables such as estuary type, basin mor...
Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-of... more Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-off from agriculture and forestry has increased the number of large-scale and chronic impacts affecting coastal and estuarine systems. The need to assess cumulative impacts is a major motivation for the current desire of managers and ecologists to define ecosystem “health” and “stress”. A number of univariate metrics have been proposed to monitor health, including indicator species, indicator ratios and diversity or contaminant metrics. Alternatively, multivariate methods can be used to test for changes in community structure due to stress. In this study we developed Multivariate Models using statistical ordination techniques to identify key stressors affecting the ‘health’ of estuarine macrofaunal communities. Macrofaunal and associated environmental samples were collected across 75 sites from within Tauranga Harbour, a large estuary located on New Zealand’s North Island. The harbour receives discharges from urbanized, industrial, agricultural and horticultural catchments. Distance-based linear modelling identified sediments, nutrients and heavy metals as key ‘stressors’ affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The multivariate models were found to be more sensitive to changing environmental health than simple univariate measures (abundance, species richness, evenness and Shannon-Wiener diversity) along an anthropogenic stress gradient. This multivariate approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state. Ultimately, such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat change and should enable long term degradative change from multiple disturbances to be assessed.
Research on ecosystem services has grown exponentially during the last decade. Historically, most... more Research on ecosystem services has grown exponentially during the last decade. Historically, most studies of marine and coastal ecosystem services (MCES) were specific to commercial fisheries or focused on single habitats such as mangroves, coastal wetlands and coral reefs. International and regional policy requirements have identified the need for spatially explicit MCES information at regional scales. In many marine regions, however, the absence of necessary information on the spatial distribution of ecological components remains a significant data gap that can prevent future progress on mapping MCES. As part of a recently funded multidisciplinary program, we have developed frameworks to quantify, spatially map and determine the ‘total economic value’ of MCES for multiple habitat types in Nelson Bays. We have used data-driven and principles-based approaches to map both functional habitats and associated ecosystem services for provisioning, regulating and supporting functions and a...
Journal of Experimental Marine Biology and Ecology, 2015
Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-of... more Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-off from agriculture and forestry has increased the number of large-scale and chronic impacts affecting coastal and estuarine systems. The need to assess cumulative impacts is a major motivation for the current desire of managers and ecologists to define ecosystem “health” and “stress”. A number of univariate metrics have been proposed to monitor health, including indicator species, indicator ratios and diversity or contaminant metrics. Alternatively, multivariate methods can be used to test for changes in community structure due to stress. In this study we developed Multivariate Models using statistical ordination techniques to identify key stressors affecting the ‘health’ of estuarine macrofaunal communities. Macrofaunal and associated environmental samples were collected across 75 sites from within Tauranga Harbour, a large estuary located on New Zealand’s North Island. The harbour receives discharges from urbanized, industrial, agricultural and horticultural catchments. Distance-based linear modelling identified sediments, nutrients and heavy metals as key ‘stressors’ affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The multivariate models were found to be more sensitive to changing environmental health than simple univariate measures (abundance, species richness, evenness and Shannon-Wiener diversity) along an anthropogenic stress gradient. This multivariate approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state. Ultimately, such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat change and should enable long term degradative change from multiple disturbances to be assessed.
Abstract. Before-After Control Impact (BACI) sampling designs are commonly used in environmental ... more Abstract. Before-After Control Impact (BACI) sampling designs are commonly used in environmental impact assessment and are considered themost effective for detecting changes due to anthropogenic disturbances. These designs handle local spatial variability through randomized placement of samples into a treatment stratum and a control stratum. When a contaminant disperses with distance from a point source it is suggested that a ‘gradient’ design will be more sensitive to change than randomized
placement of samples. This requires allocating samples according to distance, rather than by random placement within randomly placed blocks. In this paper gradient versus random sampling designs were compared using data from an oil field in the North Sea. The gradient sampling design was more powerful than a randomized CI sampling design.
Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a usefu... more Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a useful way of providing strong empirical evidence of natural or anthropogenic disturbance. Gradient designs for environmental assessment are sensitive to change for point source data, enabling the scale of the effects of a disturbance to be readily identified. If the spatial scale that is sampled fromthe point source is adequate, problems of selecting control sites can be avoided. However, sources of spatial variation in macrobenthic communities, which are not related to the impact, can confound the use of gradient designs. This can occur if the natural spatial structure overlaps that of the gradient and cannot be identified either as a location or environmental covariable. The ability to detect point source impacts using a gradient design against natural spatial variability was tested using benthic macrofaunal data collected from Manukau Harbour, New Zealand. Treated sewage wastewater is discharged into the north-west area of the Manukau Harbour. Sandflats in the vicinity of the outfall are also subject to physical disturbance from wind-waves and strong tides. Ordination techniques and the testing of apriori predictions were used to try and separate the relative effects of organic and physical disturbance on the benthic communities. While the occurrence of other environmental disturbances along a gradient of anthropogenic disturbancemakes interpretation of community pattern more difficult, the use of a gradient sampling layout, ordination analysis and the testing of a priori predictions enabled impacts of the anthropogenic and natural environmental disturbances to be interpreted. Gradient designs, therefore, provide a method of assessing complex impacts that operate over broad spatial and temporal scales.
ABSTRACT: Broad-scale anthropogenic disturbances that reduce the density of epifauna and
homogen... more ABSTRACT: Broad-scale anthropogenic disturbances that reduce the density of epifauna and
homogenise surficial sediments can have important consequences for seafloor biodiversity. We inves-
tigated the habitat structure and macrofaunal diversity of relatively simple soft-sediment habitats
over a number of spatial scales (cm to km) to identify the role of habitat structure in influencing mac-
robenthic diversity and to assess the validity of using habitat structure as a surrogate measure for bio-
diversity. We sampled 10 locations with differences in habitat structure using a sampling design that
nested macrobenthic core samples within videoed transects of the seafloor. This allowed us to deter-
mine relationships between observable habitat structure and macrobenthic diversity at a number of
spatial scales. We characterised elements of habitat structure based on direct counts of surficial sedi-
ment characteristics and the presence of other immobile features, many of which were biogenic in
origin. We also used multivariate measures (the relative multivariate dispersion, the mean and range
of the Bray-Curtis dissimilarity along the transects) to characterise habitat structure at the transect
scale. We developed regression models based on measures of habitat structure that explained 74 to
86% of the variance in macrobenthic diversity. This result suggests that removal of habitat structure
in relatively low-structure soft-sediment systems will significantly decrease their biodiversity, and
consequently that of the wider marine ecosystem.
Journal of Experimental Marine Biology and Ecology, 2002
The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common
i... more The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common
in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be
influenced by suspended sediment loads. We conducted a laboratory experiment to determine the
effect of short-term elevations in turbidity levels, such as those commonly recorded during storms,
on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a
3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment
load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold
suspended sediment concentration, and Atrina physiological condition at the end of this experiment
was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after
exposure to elevated levels for only 3 days. The field survey and transplant experiment provided
empirical evidence of a strong, negative effect of increasing suspended sediment flux on the
physiological condition of Atrina. We suggest that relationships between the physiological condition
of suspension feeders and sediment settling flux could provide a link between sediment inputs, which
commonly occur as a result of catchment runoff during rainfall events, and the ecological health of
estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural
distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale
functional and structural effects on benthic communities in estuarine and coastal areas with high rates
of sedimentation.
Sediment run-off from land has been recognised as a threat to the biodiversity of shal-
low estu... more Sediment run-off from land has been recognised as a threat to the biodiversity of shal-
low estuarine and coastal areas. Extreme rainfall events can cause flooding and landslides, which
may result in rapid deposition of fine terrigenous sediments and have serious impacts on benthic
communities. We designed a field experiment to study the response of intertidal benthos to such
depositions of terrigenous clay. The experiment was conducted at 2 contrasting intertidal sites: a
sheltered muddy sand habitat and an exposed sand habitat influenced by wind waves. Terrigenous
clay (50% water content) was deposited in replicated experimental plots (2 m diameter) at each site
in layers 0, 3, 6 or 9 cm thick. The initial response of the resident macrofauna and subsequent
recolonisation was monitored over a period of 408 d. Physical and chemical properties of the experi-
mental plots and wave climate at each site were also measured. The experiment demonstrated highly
deleterious effects of catastrophic terrigenous clay deposition on estuarine macrobenthic communi-
ties. At both sites following clay deposition, the numbers of individuals were reduced by more than
50% after 3 d and by more than 90% after 10 d, irrespective of clay thickness. Mud crabs Helice
crassa were the only animals able to emerge through the clay layer. They also exhibited elevated
densities in clay treatments over the course of the experiment. After 28 d, a storm occurred (maximum
wave height 0.4 m, period = 6 s) which dispersed the clay deposits at the exposed sandy site.
Recolonisation of the surficial sediments was rapid at the exposed site following this wind-wave dis-
turbance. However, deeper-dwelling animals such as large bivalves had not recovered to levels
observed in the control plots by the end of the experiment. At the more sheltered muddy sand site,
the clay deposition resulted in long-lasting habitat change; Although the clay was gradually broken
up and re-colonised by small crabs and surface dwelling macrofauna, recovery was still incomplete
408 d after deposition. The results emphasise the role of wind-wave disturbance and transport of
sediments and macrofauna with bedload, and the importance of bioturbation by crabs as facilitators
of macrobenthic recovery after disturbance.
There is a growing threat of habitat change in estuarine and coastal regions, yet there
are few ... more There is a growing threat of habitat change in estuarine and coastal regions, yet there
are few models that enable ecologists and resource managers to forecast the response of macrofaunal
species to long-term changes in sediment type. This study details a novel strategy that enabled us to
rapidly collect data on macrofaunal densities and sediment characteristics by sampling mud-to-sand
transition zones in 19 estuaries. Species-specific models that predict probability of occurrence rela-
tive to sediment mud content were developed for 13 common macrofaunal species. However, the
roles played by many macrofaunal species are influenced by density, not just occurrence. Over broad
spatial scales, the constraint an environmental variable places on density can be represented by the
upper (or lower) limit on density. Thus, the distribution of maximum density along the gradient from
mud to sand was modelled as another indicator of a species’ preference. Both the maximum and min-
imum values for number of taxa, number of individuals, Shannon-Wiener diversity and taxonomic
distinctness were also modelled. For most variables, good models (r2
> 0.6) were developed. The mod-
els developed for the different species exhibited a wide variety of functional forms, highlighting the
potential variation in response to habitat change even for closely related species with similar natural
history characteristics. Probability-of-occurrence models and maximum-density models for a specific
species also varied in functional form, emphasising that changes in both occurrence and density need
to be considered when predicting likely responses to changes in habitat.
In New Zealand, one species of mangrove, Avicennia marina var. australasica, forms a
characteri... more In New Zealand, one species of mangrove, Avicennia marina var. australasica, forms a
characteristic and often an extensive feature of the tidal mudflats of harbours and estuaries. Within
their natural range, mangroves have generally increased in abundance in New Zealand over the last
100 yr in response to increased sedimentation associated with concurrent changes in catchment land
use. However, little information is available about the ecological consequences of changes in the ex-
tent of mangrove habitats under varying sedimentation regimes. We therefore conducted a study to
determine the effects of high sedimentation rates on mangrove plant communities and associated ben-
thic community composition. We selected an estuary that is experiencing high rates of sedimentation
(as high as 23 mm yr–1
) and associated increases in mangrove area. We recorded clear differences in
both plant and benthic communities along a gradient of decreasing sedimentation. Mangrove archi-
tecture (such as height and density of plants) and health (as measured by chlorophyll a fluorescence)
were linked to high mud content of the sediment and elevated sedimentation patterns. Mangrove
plants at the upper landward sites, characterised by a high percentage of mud and high total nutrients
(total phosphorus [TP] and total nitrogen [TN]) and organic content, were taller than those at the sea-
ward sites and had a larger number of pneumatophores as well as the greatest number of new
seedlings. However, benthic macrofaunal diversity and abundance within the mangrove habitats were
lower than expected, and clear functional differences were found between habitats with differing sed-
imentation patterns. Sites with high sedimentation rates had lower numbers of suspension feeders, low
macrobenthic diversity, and were dominated by deposit-feeding polychaetes and oligochaetes. The
diversity and density of benthic macrofaunal communities was, however, lower than that of sandflat
communities for both mangrove habitats and adjacent intertidal mudflats in these sheltered areas,
suggesting a response to the increased silt/clay from sedimentation rather than to the mangroves
themselves. Our study demonstrates the potential for functional and structural effects on benthic
communities on a larger spatial scale in estuarine areas experiencing high rates of sedimentation.
Journal of Experimental Marine Biology and Ecology, 2008
Using modern computer based search engines we were able to assemble, review, and document the ris... more Using modern computer based search engines we were able to assemble, review, and document the rise of
the concept of scale in benthic ecology. In the early literature the term appears to have been most commonly
used to verbally qualify a result as being found at a particular spatial scale. However we document a shift
from verbal expression to quantitative methods that explicitly incorporate scale into the design of the study.
Examples include the development of nested multi-scale studies and experiments conducted over large
spatio-temporal scales at the level of estuary or region. We also review novel methods for assessing scale
effects in benthic ecosystems. First, gradient or correlative study designs have been developed in order to
assess spatial and temporal heterogeneity in benthic ecosystems. These designs involve the careful selection
of study site locations along gradients, or recommend nesting small-scale experiments within a broad-scale
correlative framework. Secondly, we briefly assess the development of statistical analytical techniques to
analyze spatial data and formal mathematical techniques for scaling functional relationships.We believe that
the design and analytical advances identified in this review provide a framework for ecologists to address
pressing large-scale questions.
ABSTRACT: This review paper identifies the main effects of oil and gas drilling waste on benthic
... more ABSTRACT: This review paper identifies the main effects of oil and gas drilling waste on benthic
environments. We identified 26 papers and technical reports that surveyed sediment samples from
72 production or exploration platform sites to assess the zone of influence of sediment contamina-
tion and biological effects on benthic communities. While oil-based fluids are now rarely used in
the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time
scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as
determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based
fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abun-
dance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in
benthic species diversity, abundance and alterations to community structure. Functional changes
included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In
general, this review demonstrates a loss of benthic biodiversity and suspension-feeding commu-
nities due to oil exploration and production and the potential for large-scale effects on sensitive
communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities
are identified.
Research on ecosystem services has grown exponentially during the last decade. Historically, many... more Research on ecosystem services has grown exponentially during the last decade. Historically, many studies of marine and coastal ecosystem services (MCES) were specific to commercial fisheries or focused on single habitats such as mangroves, coastal wetlands and coral reefs. International and regional policy requirements have identified the need for spatially explicit MCES information at regional scales. In many marine regions, however, the absence of necessary information on the spatial distribution of ecological components remains a significant data gap that can prevent future progress on mapping MCES. As part of a recently funded multidisciplinary program, we have developed frameworks to quantify, spatially map and determine the ‘total economic value’ of MCES for multiple habitat types. The research is being conducted within a case study embayment at the top of the South Island of New Zealand. We have used data-driven and principles-based approaches to map both functional habitats...
There is a growing need to predict ecological responses to long-term habitat change. However, sta... more There is a growing need to predict ecological responses to long-term habitat change. However, statistical models for marine soft-substratum ecosystems are limited, and consequently there is a need for the development of such models. In order to assess the utility of statistical model- ling approaches for predicting likely changes in species distributions under varying environmental conditions, we tested the utility of logistic modelling and classification approaches. We successfully developed models relating the presence/absence of common intertidal macrofauna to changing envi- ronmental variables such as sediment characteristics, depth/elevation, tidal currents and wind-wave (i.e. wind-generated wave activity) disturbance. The final model for each species contained between 1 and 6 variables, where the percentage correctly predicted was moderate to high, ranging from 59 to 97%. We were also able to identify relationships between higher level variables such as estuary type, basin mor...
Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-of... more Increasing population pressure, urbanization of the coastal zone and nutrient and sediment run-off from agriculture and forestry has increased the number of large-scale and chronic impacts affecting coastal and estuarine systems. The need to assess cumulative impacts is a major motivation for the current desire of managers and ecologists to define ecosystem “health” and “stress”. A number of univariate metrics have been proposed to monitor health, including indicator species, indicator ratios and diversity or contaminant metrics. Alternatively, multivariate methods can be used to test for changes in community structure due to stress. In this study we developed Multivariate Models using statistical ordination techniques to identify key stressors affecting the ‘health’ of estuarine macrofaunal communities. Macrofaunal and associated environmental samples were collected across 75 sites from within Tauranga Harbour, a large estuary located on New Zealand’s North Island. The harbour receives discharges from urbanized, industrial, agricultural and horticultural catchments. Distance-based linear modelling identified sediments, nutrients and heavy metals as key ‘stressors’ affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The multivariate models were found to be more sensitive to changing environmental health than simple univariate measures (abundance, species richness, evenness and Shannon-Wiener diversity) along an anthropogenic stress gradient. This multivariate approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state. Ultimately, such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat change and should enable long term degradative change from multiple disturbances to be assessed.
Research on ecosystem services has grown exponentially during the last decade. Historically, most... more Research on ecosystem services has grown exponentially during the last decade. Historically, most studies of marine and coastal ecosystem services (MCES) were specific to commercial fisheries or focused on single habitats such as mangroves, coastal wetlands and coral reefs. International and regional policy requirements have identified the need for spatially explicit MCES information at regional scales. In many marine regions, however, the absence of necessary information on the spatial distribution of ecological components remains a significant data gap that can prevent future progress on mapping MCES. As part of a recently funded multidisciplinary program, we have developed frameworks to quantify, spatially map and determine the ‘total economic value’ of MCES for multiple habitat types in Nelson Bays. We have used data-driven and principles-based approaches to map both functional habitats and associated ecosystem services for provisioning, regulating and supporting functions and a...
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placement of samples. This requires allocating samples according to distance, rather than by random placement within randomly placed blocks. In this paper gradient versus random sampling designs were compared using data from an oil field in the North Sea. The gradient sampling design was more powerful than a randomized CI sampling design.
homogenise surficial sediments can have important consequences for seafloor biodiversity. We inves-
tigated the habitat structure and macrofaunal diversity of relatively simple soft-sediment habitats
over a number of spatial scales (cm to km) to identify the role of habitat structure in influencing mac-
robenthic diversity and to assess the validity of using habitat structure as a surrogate measure for bio-
diversity. We sampled 10 locations with differences in habitat structure using a sampling design that
nested macrobenthic core samples within videoed transects of the seafloor. This allowed us to deter-
mine relationships between observable habitat structure and macrobenthic diversity at a number of
spatial scales. We characterised elements of habitat structure based on direct counts of surficial sedi-
ment characteristics and the presence of other immobile features, many of which were biogenic in
origin. We also used multivariate measures (the relative multivariate dispersion, the mean and range
of the Bray-Curtis dissimilarity along the transects) to characterise habitat structure at the transect
scale. We developed regression models based on measures of habitat structure that explained 74 to
86% of the variance in macrobenthic diversity. This result suggests that removal of habitat structure
in relatively low-structure soft-sediment systems will significantly decrease their biodiversity, and
consequently that of the wider marine ecosystem.
in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be
influenced by suspended sediment loads. We conducted a laboratory experiment to determine the
effect of short-term elevations in turbidity levels, such as those commonly recorded during storms,
on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a
3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment
load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold
suspended sediment concentration, and Atrina physiological condition at the end of this experiment
was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after
exposure to elevated levels for only 3 days. The field survey and transplant experiment provided
empirical evidence of a strong, negative effect of increasing suspended sediment flux on the
physiological condition of Atrina. We suggest that relationships between the physiological condition
of suspension feeders and sediment settling flux could provide a link between sediment inputs, which
commonly occur as a result of catchment runoff during rainfall events, and the ecological health of
estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural
distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale
functional and structural effects on benthic communities in estuarine and coastal areas with high rates
of sedimentation.
low estuarine and coastal areas. Extreme rainfall events can cause flooding and landslides, which
may result in rapid deposition of fine terrigenous sediments and have serious impacts on benthic
communities. We designed a field experiment to study the response of intertidal benthos to such
depositions of terrigenous clay. The experiment was conducted at 2 contrasting intertidal sites: a
sheltered muddy sand habitat and an exposed sand habitat influenced by wind waves. Terrigenous
clay (50% water content) was deposited in replicated experimental plots (2 m diameter) at each site
in layers 0, 3, 6 or 9 cm thick. The initial response of the resident macrofauna and subsequent
recolonisation was monitored over a period of 408 d. Physical and chemical properties of the experi-
mental plots and wave climate at each site were also measured. The experiment demonstrated highly
deleterious effects of catastrophic terrigenous clay deposition on estuarine macrobenthic communi-
ties. At both sites following clay deposition, the numbers of individuals were reduced by more than
50% after 3 d and by more than 90% after 10 d, irrespective of clay thickness. Mud crabs Helice
crassa were the only animals able to emerge through the clay layer. They also exhibited elevated
densities in clay treatments over the course of the experiment. After 28 d, a storm occurred (maximum
wave height 0.4 m, period = 6 s) which dispersed the clay deposits at the exposed sandy site.
Recolonisation of the surficial sediments was rapid at the exposed site following this wind-wave dis-
turbance. However, deeper-dwelling animals such as large bivalves had not recovered to levels
observed in the control plots by the end of the experiment. At the more sheltered muddy sand site,
the clay deposition resulted in long-lasting habitat change; Although the clay was gradually broken
up and re-colonised by small crabs and surface dwelling macrofauna, recovery was still incomplete
408 d after deposition. The results emphasise the role of wind-wave disturbance and transport of
sediments and macrofauna with bedload, and the importance of bioturbation by crabs as facilitators
of macrobenthic recovery after disturbance.
are few models that enable ecologists and resource managers to forecast the response of macrofaunal
species to long-term changes in sediment type. This study details a novel strategy that enabled us to
rapidly collect data on macrofaunal densities and sediment characteristics by sampling mud-to-sand
transition zones in 19 estuaries. Species-specific models that predict probability of occurrence rela-
tive to sediment mud content were developed for 13 common macrofaunal species. However, the
roles played by many macrofaunal species are influenced by density, not just occurrence. Over broad
spatial scales, the constraint an environmental variable places on density can be represented by the
upper (or lower) limit on density. Thus, the distribution of maximum density along the gradient from
mud to sand was modelled as another indicator of a species’ preference. Both the maximum and min-
imum values for number of taxa, number of individuals, Shannon-Wiener diversity and taxonomic
distinctness were also modelled. For most variables, good models (r2
> 0.6) were developed. The mod-
els developed for the different species exhibited a wide variety of functional forms, highlighting the
potential variation in response to habitat change even for closely related species with similar natural
history characteristics. Probability-of-occurrence models and maximum-density models for a specific
species also varied in functional form, emphasising that changes in both occurrence and density need
to be considered when predicting likely responses to changes in habitat.
characteristic and often an extensive feature of the tidal mudflats of harbours and estuaries. Within
their natural range, mangroves have generally increased in abundance in New Zealand over the last
100 yr in response to increased sedimentation associated with concurrent changes in catchment land
use. However, little information is available about the ecological consequences of changes in the ex-
tent of mangrove habitats under varying sedimentation regimes. We therefore conducted a study to
determine the effects of high sedimentation rates on mangrove plant communities and associated ben-
thic community composition. We selected an estuary that is experiencing high rates of sedimentation
(as high as 23 mm yr–1
) and associated increases in mangrove area. We recorded clear differences in
both plant and benthic communities along a gradient of decreasing sedimentation. Mangrove archi-
tecture (such as height and density of plants) and health (as measured by chlorophyll a fluorescence)
were linked to high mud content of the sediment and elevated sedimentation patterns. Mangrove
plants at the upper landward sites, characterised by a high percentage of mud and high total nutrients
(total phosphorus [TP] and total nitrogen [TN]) and organic content, were taller than those at the sea-
ward sites and had a larger number of pneumatophores as well as the greatest number of new
seedlings. However, benthic macrofaunal diversity and abundance within the mangrove habitats were
lower than expected, and clear functional differences were found between habitats with differing sed-
imentation patterns. Sites with high sedimentation rates had lower numbers of suspension feeders, low
macrobenthic diversity, and were dominated by deposit-feeding polychaetes and oligochaetes. The
diversity and density of benthic macrofaunal communities was, however, lower than that of sandflat
communities for both mangrove habitats and adjacent intertidal mudflats in these sheltered areas,
suggesting a response to the increased silt/clay from sedimentation rather than to the mangroves
themselves. Our study demonstrates the potential for functional and structural effects on benthic
communities on a larger spatial scale in estuarine areas experiencing high rates of sedimentation.
the concept of scale in benthic ecology. In the early literature the term appears to have been most commonly
used to verbally qualify a result as being found at a particular spatial scale. However we document a shift
from verbal expression to quantitative methods that explicitly incorporate scale into the design of the study.
Examples include the development of nested multi-scale studies and experiments conducted over large
spatio-temporal scales at the level of estuary or region. We also review novel methods for assessing scale
effects in benthic ecosystems. First, gradient or correlative study designs have been developed in order to
assess spatial and temporal heterogeneity in benthic ecosystems. These designs involve the careful selection
of study site locations along gradients, or recommend nesting small-scale experiments within a broad-scale
correlative framework. Secondly, we briefly assess the development of statistical analytical techniques to
analyze spatial data and formal mathematical techniques for scaling functional relationships.We believe that
the design and analytical advances identified in this review provide a framework for ecologists to address
pressing large-scale questions.
environments. We identified 26 papers and technical reports that surveyed sediment samples from
72 production or exploration platform sites to assess the zone of influence of sediment contamina-
tion and biological effects on benthic communities. While oil-based fluids are now rarely used in
the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time
scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as
determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based
fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abun-
dance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in
benthic species diversity, abundance and alterations to community structure. Functional changes
included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In
general, this review demonstrates a loss of benthic biodiversity and suspension-feeding commu-
nities due to oil exploration and production and the potential for large-scale effects on sensitive
communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities
are identified.
placement of samples. This requires allocating samples according to distance, rather than by random placement within randomly placed blocks. In this paper gradient versus random sampling designs were compared using data from an oil field in the North Sea. The gradient sampling design was more powerful than a randomized CI sampling design.
homogenise surficial sediments can have important consequences for seafloor biodiversity. We inves-
tigated the habitat structure and macrofaunal diversity of relatively simple soft-sediment habitats
over a number of spatial scales (cm to km) to identify the role of habitat structure in influencing mac-
robenthic diversity and to assess the validity of using habitat structure as a surrogate measure for bio-
diversity. We sampled 10 locations with differences in habitat structure using a sampling design that
nested macrobenthic core samples within videoed transects of the seafloor. This allowed us to deter-
mine relationships between observable habitat structure and macrobenthic diversity at a number of
spatial scales. We characterised elements of habitat structure based on direct counts of surficial sedi-
ment characteristics and the presence of other immobile features, many of which were biogenic in
origin. We also used multivariate measures (the relative multivariate dispersion, the mean and range
of the Bray-Curtis dissimilarity along the transects) to characterise habitat structure at the transect
scale. We developed regression models based on measures of habitat structure that explained 74 to
86% of the variance in macrobenthic diversity. This result suggests that removal of habitat structure
in relatively low-structure soft-sediment systems will significantly decrease their biodiversity, and
consequently that of the wider marine ecosystem.
in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be
influenced by suspended sediment loads. We conducted a laboratory experiment to determine the
effect of short-term elevations in turbidity levels, such as those commonly recorded during storms,
on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a
3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment
load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold
suspended sediment concentration, and Atrina physiological condition at the end of this experiment
was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after
exposure to elevated levels for only 3 days. The field survey and transplant experiment provided
empirical evidence of a strong, negative effect of increasing suspended sediment flux on the
physiological condition of Atrina. We suggest that relationships between the physiological condition
of suspension feeders and sediment settling flux could provide a link between sediment inputs, which
commonly occur as a result of catchment runoff during rainfall events, and the ecological health of
estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural
distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale
functional and structural effects on benthic communities in estuarine and coastal areas with high rates
of sedimentation.
low estuarine and coastal areas. Extreme rainfall events can cause flooding and landslides, which
may result in rapid deposition of fine terrigenous sediments and have serious impacts on benthic
communities. We designed a field experiment to study the response of intertidal benthos to such
depositions of terrigenous clay. The experiment was conducted at 2 contrasting intertidal sites: a
sheltered muddy sand habitat and an exposed sand habitat influenced by wind waves. Terrigenous
clay (50% water content) was deposited in replicated experimental plots (2 m diameter) at each site
in layers 0, 3, 6 or 9 cm thick. The initial response of the resident macrofauna and subsequent
recolonisation was monitored over a period of 408 d. Physical and chemical properties of the experi-
mental plots and wave climate at each site were also measured. The experiment demonstrated highly
deleterious effects of catastrophic terrigenous clay deposition on estuarine macrobenthic communi-
ties. At both sites following clay deposition, the numbers of individuals were reduced by more than
50% after 3 d and by more than 90% after 10 d, irrespective of clay thickness. Mud crabs Helice
crassa were the only animals able to emerge through the clay layer. They also exhibited elevated
densities in clay treatments over the course of the experiment. After 28 d, a storm occurred (maximum
wave height 0.4 m, period = 6 s) which dispersed the clay deposits at the exposed sandy site.
Recolonisation of the surficial sediments was rapid at the exposed site following this wind-wave dis-
turbance. However, deeper-dwelling animals such as large bivalves had not recovered to levels
observed in the control plots by the end of the experiment. At the more sheltered muddy sand site,
the clay deposition resulted in long-lasting habitat change; Although the clay was gradually broken
up and re-colonised by small crabs and surface dwelling macrofauna, recovery was still incomplete
408 d after deposition. The results emphasise the role of wind-wave disturbance and transport of
sediments and macrofauna with bedload, and the importance of bioturbation by crabs as facilitators
of macrobenthic recovery after disturbance.
are few models that enable ecologists and resource managers to forecast the response of macrofaunal
species to long-term changes in sediment type. This study details a novel strategy that enabled us to
rapidly collect data on macrofaunal densities and sediment characteristics by sampling mud-to-sand
transition zones in 19 estuaries. Species-specific models that predict probability of occurrence rela-
tive to sediment mud content were developed for 13 common macrofaunal species. However, the
roles played by many macrofaunal species are influenced by density, not just occurrence. Over broad
spatial scales, the constraint an environmental variable places on density can be represented by the
upper (or lower) limit on density. Thus, the distribution of maximum density along the gradient from
mud to sand was modelled as another indicator of a species’ preference. Both the maximum and min-
imum values for number of taxa, number of individuals, Shannon-Wiener diversity and taxonomic
distinctness were also modelled. For most variables, good models (r2
> 0.6) were developed. The mod-
els developed for the different species exhibited a wide variety of functional forms, highlighting the
potential variation in response to habitat change even for closely related species with similar natural
history characteristics. Probability-of-occurrence models and maximum-density models for a specific
species also varied in functional form, emphasising that changes in both occurrence and density need
to be considered when predicting likely responses to changes in habitat.
characteristic and often an extensive feature of the tidal mudflats of harbours and estuaries. Within
their natural range, mangroves have generally increased in abundance in New Zealand over the last
100 yr in response to increased sedimentation associated with concurrent changes in catchment land
use. However, little information is available about the ecological consequences of changes in the ex-
tent of mangrove habitats under varying sedimentation regimes. We therefore conducted a study to
determine the effects of high sedimentation rates on mangrove plant communities and associated ben-
thic community composition. We selected an estuary that is experiencing high rates of sedimentation
(as high as 23 mm yr–1
) and associated increases in mangrove area. We recorded clear differences in
both plant and benthic communities along a gradient of decreasing sedimentation. Mangrove archi-
tecture (such as height and density of plants) and health (as measured by chlorophyll a fluorescence)
were linked to high mud content of the sediment and elevated sedimentation patterns. Mangrove
plants at the upper landward sites, characterised by a high percentage of mud and high total nutrients
(total phosphorus [TP] and total nitrogen [TN]) and organic content, were taller than those at the sea-
ward sites and had a larger number of pneumatophores as well as the greatest number of new
seedlings. However, benthic macrofaunal diversity and abundance within the mangrove habitats were
lower than expected, and clear functional differences were found between habitats with differing sed-
imentation patterns. Sites with high sedimentation rates had lower numbers of suspension feeders, low
macrobenthic diversity, and were dominated by deposit-feeding polychaetes and oligochaetes. The
diversity and density of benthic macrofaunal communities was, however, lower than that of sandflat
communities for both mangrove habitats and adjacent intertidal mudflats in these sheltered areas,
suggesting a response to the increased silt/clay from sedimentation rather than to the mangroves
themselves. Our study demonstrates the potential for functional and structural effects on benthic
communities on a larger spatial scale in estuarine areas experiencing high rates of sedimentation.
the concept of scale in benthic ecology. In the early literature the term appears to have been most commonly
used to verbally qualify a result as being found at a particular spatial scale. However we document a shift
from verbal expression to quantitative methods that explicitly incorporate scale into the design of the study.
Examples include the development of nested multi-scale studies and experiments conducted over large
spatio-temporal scales at the level of estuary or region. We also review novel methods for assessing scale
effects in benthic ecosystems. First, gradient or correlative study designs have been developed in order to
assess spatial and temporal heterogeneity in benthic ecosystems. These designs involve the careful selection
of study site locations along gradients, or recommend nesting small-scale experiments within a broad-scale
correlative framework. Secondly, we briefly assess the development of statistical analytical techniques to
analyze spatial data and formal mathematical techniques for scaling functional relationships.We believe that
the design and analytical advances identified in this review provide a framework for ecologists to address
pressing large-scale questions.
environments. We identified 26 papers and technical reports that surveyed sediment samples from
72 production or exploration platform sites to assess the zone of influence of sediment contamina-
tion and biological effects on benthic communities. While oil-based fluids are now rarely used in
the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time
scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as
determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based
fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abun-
dance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in
benthic species diversity, abundance and alterations to community structure. Functional changes
included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In
general, this review demonstrates a loss of benthic biodiversity and suspension-feeding commu-
nities due to oil exploration and production and the potential for large-scale effects on sensitive
communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities
are identified.