Host-associated microbial communities play a fundamental role in the life of eukaryotic hosts. It... more Host-associated microbial communities play a fundamental role in the life of eukaryotic hosts. It is increasingly argued that hosts and their microbiota must be studied together as 'holobionts' to better understand the effects of environmental stressors on host functioning. Disruptions of host-microbiota interactions by environmental stressors can negatively affect host performance and survival. Substantial ecological impacts are likely when the affected hosts are habitat-forming species (e.g., trees, kelps) that underpin local biodiversity. In marine systems, coastal urbanisation via the addition of artificial structures is a major source of stress to habitat formers, but its effect on their associated microbial communities is unknown. We characterised kelp-associated microbial communities in two of the most common and abundant artificial structures in Sydney Harbour-pier-pilings and seawalls-and in neighbouring natural rocky reefs. The kelp is the dominant habitat-forming ...
Habitat structure influences the diversity and distribution of organisms, potentially affecting t... more Habitat structure influences the diversity and distribution of organisms, potentially affecting their response to disturbances by either affecting their 'susceptibility' or through the provision of resources that can mitigate impacts of disturbances. Chemical disturbances due to contamination are associated with decreases in diversity and functioning of systems and are also likely to increase due to coastal urbanisation. Understanding how habitat structure interacts with contaminants is essential to predict and therefore manage such effects, minimising their consequences to marine systems. Here, we manipulated two structurally different habitats and exposed them to different types of contaminants. The effects of contamination and habitat structure interacted, affecting species richness. More complex experimental habitats were colonized by a greater diversity of organisms than the less complex habitats. These differences disappeared, however, when habitats were exposed to contaminants, suggesting that contaminants can override effects of habitats structure at small spatial scales. These results provide insight into the complex ways that habitat structure and contamination interact and the need to incorporate evidence of biotic responses from individual disturbances to multiple stressors. Such effects need to be taken into account when designing and planning management and conservation strategies to natural systems.
Global seascapes are increasingly modified to support high levels of human activity in the coasta... more Global seascapes are increasingly modified to support high levels of human activity in the coastal zone. Modifications include the addition of defense structures and boating infrastructure, such as seawalls and marinas that replace natural habitats. Artificial structures support different macrofaunal communities to those found on natural rocky shores; however, little is known about differences in microbial community structure or function in urban seascapes. Understanding how artificial constructions in marine environments influence microbial communities is important as these assemblages contribute to many basic ecological processes. In this study, the bacterial communities of intertidal biofilms were compared between artificial structures (seawalls) and natural habitats (rocky shores) within Sydney Harbour. Plots were cleared on each type of habitat at eight locations. After 3 weeks the newly formed biofilm was sampled and the 16S rRNA gene sequenced using the Illumina Miseq platform. To account for differences in orientation and substrate material between seawalls and rocky shores that might have influenced our survey, we also deployed recruitment blocks next to the habitats at all locations for 3 weeks and then sampled and sequenced their microbial communities. Intertidal bacterial community structure sampled from plots differed between seawalls and rocky shores, but when substrate material, age and orientation were kept constant (with recruitment blocks) then bacterial communities were similar in composition and structure among habitats. This suggests that changes in bacterial communities on seawalls are not related to environmental differences between locations, but may be related to other intrinsic factors that differ between the habitats such as orientation, complexity, or predation. This is one of the first comparisons of intertidal microbial communities on natural and artificial surfaces and illustrates substantial ecological differences with potential consequences for biofilm function and the recruitment of macrofauna.
DESCRIPTION This poster presentation discussed the limitations of the current assessment approach... more DESCRIPTION This poster presentation discussed the limitations of the current assessment approaches and how multiple stressors at large scales can be better evaluated in ecological risk assessments to inform the development of more efficient and preventive management policies based on adaptive management in the future. It is envisaged that the integration of new and emerging tools such as 'Big Data', ecological modelling with a future risk assessment paradigm will make this achievable.
Globally the coastal zone is suffering the collateral damage from continuing urban development an... more Globally the coastal zone is suffering the collateral damage from continuing urban development and construction, expanding resource sectors, increasing population, regulation to river flow, and on-going land change and degradation. While protection of natural coastal habitat is recommended, balancing conservation with human services is now the challenge for managers. Marine infrastructure such as seawalls, marinas and offshore platforms is increasingly used to support and provide services, but has primarily been designed for engineering purposes without consideration of the ecological consequences. Increasingly developments are seeking alternatives to hard engineering and a range of ecological solutions has begun to replace or be incorporated into marine and coastal infrastructure. But too often, hard engineering remains the primary strategy because the tools for managers to implement ecological solutions are either lacking or not supported by policy and stakeholders. Here we outline critical research needs for marine urban development and emerging strategies that seek to mitigate the impacts of marine infrastructure. We present case studies to highlight the strategic direction necessary to support management decisions internationally.
Australia’s coastal zone is suffering the collateral damage from continuing urban development and... more Australia’s coastal zone is suffering the collateral damage from continuing urban development and construction, expanding resource sectors, increasing population, regulation to river flow, and on-going land change and degradation. The global community is already watching Australia manage future development and industrial growth, particularly adjacent to a significant marine ecosystem, the Great Barrier Reef. While protection of natural coastal habitat is recommended, balancing conservation with human services is now the challenge for managers. Here we outline critical research needs for marine urban development and emerging engineering strategies that seek to mitigate impacts. We provide the strategic direction necessary to support management decisions for the protection of Australia’s coastal zone.
The magnitude and direction of direct and indirect effects of disturbances can be context-depende... more The magnitude and direction of direct and indirect effects of disturbances can be context-dependent, with the matrix (surrounding habitat) in which populations are embedded either mitigating or worsening the impacts of disturbances. Chemical disturbances are particularly harmful and can affect organisms directly or indirectly. We used bleach, a common stressor in marine systems, to test hypotheses about direct and indirect effects of anthropogenic disturbances on intertidal grazers and the influence of the surrounding macro-algal matrix on such effects. We manipulated the contaminant, food (biofilm) and surrounding macro-algal matrix. Fewer limpets were found in contaminated areas. Bleach had a strong direct negative effect on limpets and caused a reduction in biofilm food, indirectly affecting limpets. This effect was strongest in the presence of macro-algal matrix. Anthropogenic disturbances can have major consequences via direct and indirect effects on key interacting species. We...
The CNAAA is the only Brazilian Nuclear Power Plant. Discharge from the cooling water system flow... more The CNAAA is the only Brazilian Nuclear Power Plant. Discharge from the cooling water system flows into the Ilha Grande Bay (SE, Brazil). Water temperature at the surface, chlorine level and current velocity were higher at the discharge than at the intake area. Diversity, evenness, richness and density were higher in control sites than in discharge site, mainly in the surface transect. Mycale microsigmatosa was considered a negative bioindicator and Haliclona sp.1 was considered a positive bioindicator for the discharge impact. The impact of the discharge of the CNAAA cooling system on the sponge community of Ilha Grande Bay was great, mainly due to high temperature. However, this impact is stronger at the surface than on the bottom and restricted to the vicinity of the discharge area.
ABSTRACT Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical ... more ABSTRACT Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical functions, such as primary and secondary productivity, are, however, increasingly threatened by a range of anthropogenic stressors. Although the extent of the threat of contamination is large and has been increasing, pollution is one of the least-studied stressors in ecology.We did a systematic review and critical synthesis of the effects of contaminants on marine and estuarine ecosystem functioning. No other stressors besides toxic chemicals were included in this review.We identified 264 relevant studies across a range of contaminants. Toxic contaminants generally altered marine ecosystem functioning by reducing productivity and increasing respiration. Effects varied, however, according to the type of contaminant and the component(s) of the system studied (e.g. particular trophic levels, functional groups or taxonomic groups). Toxicity studies that included a measure of ecosystem function were strongly biased towards planktonic communities in contrast to studies of biodiversity, which have been dominated by work on soft-sediment communities. Toxicant studies that included measures of ecosystem function rarely included a measure of biodiversity and rarely interpreted their findings within an ecosystem function context.Studies that included multiple components of an ecosystem, that is more than one functional group of organisms, were more likely to find no effect of contamination, possibly due to ecological interactions. Studies that suffered from unclear or flawed methodology were more likely to find a significant impact of contaminants on some endpoints of ecosystem functioning than studies with appropriate designs.Synthesis and applications. Up to 70% of studies found negative impacts of contaminants on primary production. Toxic contaminants therefore have the potential to greatly affect the ecosystem services and benefits provided by these systems. Our findings will help managers and policymakers to determine whether contaminants are affecting both biodiversity and ecosystem functioning in a given context, therefore helping to prioritize areas for remediation. There is still, however, much to understand about the relationships between biological diversity and ecosystem functioning. Our understanding of chemical contaminant effects will remain patchy until direct measures of both variables are undertaken within multiple ecosystems. We therefore recommend the adoption of functional endpoints, such as productivity and respiration, in ecological studies, routine toxicological studies and ecological risk assessment.
Understanding the effects of environmental change on the distribution and abundance of strongly i... more Understanding the effects of environmental change on the distribution and abundance of strongly interacting organisms, such as intertidal macroalgae and their grazers, needs a thorough knowledge of their underpinning ecological relationships. Control of grazer-plant interactions is bi-directional on northwestern European coasts: grazing by limpets structures populations of macroalgae, while macroalgae provide habitat and food for limpets. Scottish shores dominated by the macroalga Fucus vesiculosus support lower densities and larger sizes of limpets Patella vulgata than shores with less Fucus. These patterns may be due to differences in inter-size-class competitive interactions of limpets among shores with different covers of Fucus. To examine this model, densities of small and large limpets were manipulated in plots with and without Fucus. Amounts of biofilm were measured in each plot. The presence of Fucus increased survival but hindered growth of small (15 mm TL) limpets, which were negatively affected by the presence of large limpets (31 mm TL). In contrast, large limpets were not affected by the presence of Fucus or of small limpets. This suggests the occurrence of asymmetric intersize-class competition, which was influenced by the presence of macroalgae. Macroalgae and increased densities of limpets did not influence amounts of biofilm. Our findings highlight the role of interactions among organisms in generating ecological responses to environmental change.
Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the pote... more Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the potentially impacted site and multiple reference sites are sampled through time, before and after the impact. Often, however, the lack of information regarding the potential overall impact, the lack of knowledge about the environment in many regions worldwide, budgets constraints and the increasing dimensions of human activities compromise the reliability of the impact assessment. We evaluated the impact, if any, and its extent of a nuclear power plant effluent on sessile epibiota assemblages using a suitable and feasible sampling design with no 'before' data and budget and logistic constraints. Assemblages were sampled at multiple times and at increasing distances from the point of the discharge of the effluent. There was a clear and localized effect of the power plant effluent (up to 100 m from the point of the discharge). However, depending on the time of the year, the impact reaches up to 600 m. We found a significantly lower richness of taxa in the Effluent site when compared to other sites. Furthermore, at all times, the variability of assemblages near the discharge was also smaller than in other sites. Although the sampling design used here (in particular the number of replicates) did not allow an unambiguously evaluation of the full extent of the impact in relation to its intensity and temporal variability, the multiple temporal and spatial scales used allowed the detection of some differences in the intensity of the impact, depending on the time of sampling. Our findings greatly contribute to increase the knowledge on the effects of multiple stressors caused by the effluent of a power plant and also have important implications for management strategies and conservation ecology, in general.
Transplantation of artificial panels between a polluted and an unpolluted site was used to evalua... more Transplantation of artificial panels between a polluted and an unpolluted site was used to evaluate eutrophication effects on the development of fouling communities in Ilha Grande Bay, SE Brazil. Organic pollution changed the relative dominance of species in the fouling communities of transplanted panels, although, their richness, evenness, and specific composition did not change. The chlorophyte Ulva sp. occurred only in the polluted site and in panels transplanted to it, whereas the bryozoan Aetea lingulata was found only in the unpolluted site and in panels transplanted to this site. These species are therefore good pollution indicators. The best pollution indicators, however, were amphipods and Spionidae polychaetes which formed mucous tubes. These groups had significantly higher values of percent cover (p<0.0001) in the polluted site and in panels transferred to it. The dominance shift is the first evidence that more meaningful changes can occur in the structure of fouling communities on a long-term scale.
Journal of Experimental Marine Biology and Ecology, 2010
Most knowledge of the effects of metals on benthic organisms comes from laboratory studies with s... more Most knowledge of the effects of metals on benthic organisms comes from laboratory studies with subsequent extrapolation to field scenarios. Here, we critically reviewed studies on effects of metals on aquatic organisms, with an emphasis on marine systems to determine the "real" state of our current knowledge about effect of metals on assemblages. These studies include experiments in the laboratory and/or micro-and meso-cosms and those done in the field. Laboratory studies have shown lethal and sub-lethal effects of metals on organisms. There is, however, little evidence that these effects occur in natural environments. Conditions in the laboratory are very different from those in natural habitats. It is sensible, then, to assume that organisms may respond differently under field conditions, but how representative laboratory studies are of field conditions is rarely tested. In contrast, many field studies use patterns to infer processes, without any experimental verification. Of the descriptive papers reviewed here, nearly 50% found differences in the assemblages between contaminated and reference areas. Often, however, the differences were definitely not attributable or could not be unambiguously attributed to the presence of metals, because most of the studies lacked proper controls and/or appropriate temporal or spatial replication. Relatively few experimental studies in the field found clear effects. Where they were found experimentally, differences were generally decreased abundances of populations of some species or reduced diversity of species. Indirect ecological interactions can also occur, where abundances of a superior competitor are reduced by metals, leading to increases in abundances of other species. Properly designed experimental field studies are needed to evaluate the effects of metals on organisms and/or assemblages in natural habitats. This is essential for developing realistic environmental guidelines and managerial strategies for protecting aquatic habitats.
Biofilms are sensitive to environmental conditions. Impacts of contaminants on 2 assemblages are ... more Biofilms are sensitive to environmental conditions. Impacts of contaminants on 2 assemblages are often investigated in laboratories or in meso-cosms. Such experiments are rarely representative of effects of contaminants on biofilms under natural conditions. Studies in 4 real field situations, with enough power to detect impacts, are necessary to develop better understanding of the effects of contaminants on ecological processes. Metals are a common 6 estuarine contaminant and can cause disturbances to the assemblages. Using a new technique to experimentally deliver contaminants to micro-algal assemblages, we tested hypotheses about 8 the effects of zinc on micro-algal biofilm growing on settlement panels in subtidal and intertidal habitats. Control panels deployed for one month in each habitat had significantly 10 greater amounts of biofilm than those exposed to zinc. After three months of deployment, results varied with location. The observed effects on the biofilm did not, however, cause 12 significant changes in the fouling assemblages that developed on the panels.
Host-associated microbial communities play a fundamental role in the life of eukaryotic hosts. It... more Host-associated microbial communities play a fundamental role in the life of eukaryotic hosts. It is increasingly argued that hosts and their microbiota must be studied together as 'holobionts' to better understand the effects of environmental stressors on host functioning. Disruptions of host-microbiota interactions by environmental stressors can negatively affect host performance and survival. Substantial ecological impacts are likely when the affected hosts are habitat-forming species (e.g., trees, kelps) that underpin local biodiversity. In marine systems, coastal urbanisation via the addition of artificial structures is a major source of stress to habitat formers, but its effect on their associated microbial communities is unknown. We characterised kelp-associated microbial communities in two of the most common and abundant artificial structures in Sydney Harbour-pier-pilings and seawalls-and in neighbouring natural rocky reefs. The kelp is the dominant habitat-forming ...
Habitat structure influences the diversity and distribution of organisms, potentially affecting t... more Habitat structure influences the diversity and distribution of organisms, potentially affecting their response to disturbances by either affecting their 'susceptibility' or through the provision of resources that can mitigate impacts of disturbances. Chemical disturbances due to contamination are associated with decreases in diversity and functioning of systems and are also likely to increase due to coastal urbanisation. Understanding how habitat structure interacts with contaminants is essential to predict and therefore manage such effects, minimising their consequences to marine systems. Here, we manipulated two structurally different habitats and exposed them to different types of contaminants. The effects of contamination and habitat structure interacted, affecting species richness. More complex experimental habitats were colonized by a greater diversity of organisms than the less complex habitats. These differences disappeared, however, when habitats were exposed to contaminants, suggesting that contaminants can override effects of habitats structure at small spatial scales. These results provide insight into the complex ways that habitat structure and contamination interact and the need to incorporate evidence of biotic responses from individual disturbances to multiple stressors. Such effects need to be taken into account when designing and planning management and conservation strategies to natural systems.
Global seascapes are increasingly modified to support high levels of human activity in the coasta... more Global seascapes are increasingly modified to support high levels of human activity in the coastal zone. Modifications include the addition of defense structures and boating infrastructure, such as seawalls and marinas that replace natural habitats. Artificial structures support different macrofaunal communities to those found on natural rocky shores; however, little is known about differences in microbial community structure or function in urban seascapes. Understanding how artificial constructions in marine environments influence microbial communities is important as these assemblages contribute to many basic ecological processes. In this study, the bacterial communities of intertidal biofilms were compared between artificial structures (seawalls) and natural habitats (rocky shores) within Sydney Harbour. Plots were cleared on each type of habitat at eight locations. After 3 weeks the newly formed biofilm was sampled and the 16S rRNA gene sequenced using the Illumina Miseq platform. To account for differences in orientation and substrate material between seawalls and rocky shores that might have influenced our survey, we also deployed recruitment blocks next to the habitats at all locations for 3 weeks and then sampled and sequenced their microbial communities. Intertidal bacterial community structure sampled from plots differed between seawalls and rocky shores, but when substrate material, age and orientation were kept constant (with recruitment blocks) then bacterial communities were similar in composition and structure among habitats. This suggests that changes in bacterial communities on seawalls are not related to environmental differences between locations, but may be related to other intrinsic factors that differ between the habitats such as orientation, complexity, or predation. This is one of the first comparisons of intertidal microbial communities on natural and artificial surfaces and illustrates substantial ecological differences with potential consequences for biofilm function and the recruitment of macrofauna.
DESCRIPTION This poster presentation discussed the limitations of the current assessment approach... more DESCRIPTION This poster presentation discussed the limitations of the current assessment approaches and how multiple stressors at large scales can be better evaluated in ecological risk assessments to inform the development of more efficient and preventive management policies based on adaptive management in the future. It is envisaged that the integration of new and emerging tools such as 'Big Data', ecological modelling with a future risk assessment paradigm will make this achievable.
Globally the coastal zone is suffering the collateral damage from continuing urban development an... more Globally the coastal zone is suffering the collateral damage from continuing urban development and construction, expanding resource sectors, increasing population, regulation to river flow, and on-going land change and degradation. While protection of natural coastal habitat is recommended, balancing conservation with human services is now the challenge for managers. Marine infrastructure such as seawalls, marinas and offshore platforms is increasingly used to support and provide services, but has primarily been designed for engineering purposes without consideration of the ecological consequences. Increasingly developments are seeking alternatives to hard engineering and a range of ecological solutions has begun to replace or be incorporated into marine and coastal infrastructure. But too often, hard engineering remains the primary strategy because the tools for managers to implement ecological solutions are either lacking or not supported by policy and stakeholders. Here we outline critical research needs for marine urban development and emerging strategies that seek to mitigate the impacts of marine infrastructure. We present case studies to highlight the strategic direction necessary to support management decisions internationally.
Australia’s coastal zone is suffering the collateral damage from continuing urban development and... more Australia’s coastal zone is suffering the collateral damage from continuing urban development and construction, expanding resource sectors, increasing population, regulation to river flow, and on-going land change and degradation. The global community is already watching Australia manage future development and industrial growth, particularly adjacent to a significant marine ecosystem, the Great Barrier Reef. While protection of natural coastal habitat is recommended, balancing conservation with human services is now the challenge for managers. Here we outline critical research needs for marine urban development and emerging engineering strategies that seek to mitigate impacts. We provide the strategic direction necessary to support management decisions for the protection of Australia’s coastal zone.
The magnitude and direction of direct and indirect effects of disturbances can be context-depende... more The magnitude and direction of direct and indirect effects of disturbances can be context-dependent, with the matrix (surrounding habitat) in which populations are embedded either mitigating or worsening the impacts of disturbances. Chemical disturbances are particularly harmful and can affect organisms directly or indirectly. We used bleach, a common stressor in marine systems, to test hypotheses about direct and indirect effects of anthropogenic disturbances on intertidal grazers and the influence of the surrounding macro-algal matrix on such effects. We manipulated the contaminant, food (biofilm) and surrounding macro-algal matrix. Fewer limpets were found in contaminated areas. Bleach had a strong direct negative effect on limpets and caused a reduction in biofilm food, indirectly affecting limpets. This effect was strongest in the presence of macro-algal matrix. Anthropogenic disturbances can have major consequences via direct and indirect effects on key interacting species. We...
The CNAAA is the only Brazilian Nuclear Power Plant. Discharge from the cooling water system flow... more The CNAAA is the only Brazilian Nuclear Power Plant. Discharge from the cooling water system flows into the Ilha Grande Bay (SE, Brazil). Water temperature at the surface, chlorine level and current velocity were higher at the discharge than at the intake area. Diversity, evenness, richness and density were higher in control sites than in discharge site, mainly in the surface transect. Mycale microsigmatosa was considered a negative bioindicator and Haliclona sp.1 was considered a positive bioindicator for the discharge impact. The impact of the discharge of the CNAAA cooling system on the sponge community of Ilha Grande Bay was great, mainly due to high temperature. However, this impact is stronger at the surface than on the bottom and restricted to the vicinity of the discharge area.
ABSTRACT Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical ... more ABSTRACT Ecosystem functioning underpins the ecosystem services upon which humans rely. Critical functions, such as primary and secondary productivity, are, however, increasingly threatened by a range of anthropogenic stressors. Although the extent of the threat of contamination is large and has been increasing, pollution is one of the least-studied stressors in ecology.We did a systematic review and critical synthesis of the effects of contaminants on marine and estuarine ecosystem functioning. No other stressors besides toxic chemicals were included in this review.We identified 264 relevant studies across a range of contaminants. Toxic contaminants generally altered marine ecosystem functioning by reducing productivity and increasing respiration. Effects varied, however, according to the type of contaminant and the component(s) of the system studied (e.g. particular trophic levels, functional groups or taxonomic groups). Toxicity studies that included a measure of ecosystem function were strongly biased towards planktonic communities in contrast to studies of biodiversity, which have been dominated by work on soft-sediment communities. Toxicant studies that included measures of ecosystem function rarely included a measure of biodiversity and rarely interpreted their findings within an ecosystem function context.Studies that included multiple components of an ecosystem, that is more than one functional group of organisms, were more likely to find no effect of contamination, possibly due to ecological interactions. Studies that suffered from unclear or flawed methodology were more likely to find a significant impact of contaminants on some endpoints of ecosystem functioning than studies with appropriate designs.Synthesis and applications. Up to 70% of studies found negative impacts of contaminants on primary production. Toxic contaminants therefore have the potential to greatly affect the ecosystem services and benefits provided by these systems. Our findings will help managers and policymakers to determine whether contaminants are affecting both biodiversity and ecosystem functioning in a given context, therefore helping to prioritize areas for remediation. There is still, however, much to understand about the relationships between biological diversity and ecosystem functioning. Our understanding of chemical contaminant effects will remain patchy until direct measures of both variables are undertaken within multiple ecosystems. We therefore recommend the adoption of functional endpoints, such as productivity and respiration, in ecological studies, routine toxicological studies and ecological risk assessment.
Understanding the effects of environmental change on the distribution and abundance of strongly i... more Understanding the effects of environmental change on the distribution and abundance of strongly interacting organisms, such as intertidal macroalgae and their grazers, needs a thorough knowledge of their underpinning ecological relationships. Control of grazer-plant interactions is bi-directional on northwestern European coasts: grazing by limpets structures populations of macroalgae, while macroalgae provide habitat and food for limpets. Scottish shores dominated by the macroalga Fucus vesiculosus support lower densities and larger sizes of limpets Patella vulgata than shores with less Fucus. These patterns may be due to differences in inter-size-class competitive interactions of limpets among shores with different covers of Fucus. To examine this model, densities of small and large limpets were manipulated in plots with and without Fucus. Amounts of biofilm were measured in each plot. The presence of Fucus increased survival but hindered growth of small (15 mm TL) limpets, which were negatively affected by the presence of large limpets (31 mm TL). In contrast, large limpets were not affected by the presence of Fucus or of small limpets. This suggests the occurrence of asymmetric intersize-class competition, which was influenced by the presence of macroalgae. Macroalgae and increased densities of limpets did not influence amounts of biofilm. Our findings highlight the role of interactions among organisms in generating ecological responses to environmental change.
Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the pote... more Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the potentially impacted site and multiple reference sites are sampled through time, before and after the impact. Often, however, the lack of information regarding the potential overall impact, the lack of knowledge about the environment in many regions worldwide, budgets constraints and the increasing dimensions of human activities compromise the reliability of the impact assessment. We evaluated the impact, if any, and its extent of a nuclear power plant effluent on sessile epibiota assemblages using a suitable and feasible sampling design with no 'before' data and budget and logistic constraints. Assemblages were sampled at multiple times and at increasing distances from the point of the discharge of the effluent. There was a clear and localized effect of the power plant effluent (up to 100 m from the point of the discharge). However, depending on the time of the year, the impact reaches up to 600 m. We found a significantly lower richness of taxa in the Effluent site when compared to other sites. Furthermore, at all times, the variability of assemblages near the discharge was also smaller than in other sites. Although the sampling design used here (in particular the number of replicates) did not allow an unambiguously evaluation of the full extent of the impact in relation to its intensity and temporal variability, the multiple temporal and spatial scales used allowed the detection of some differences in the intensity of the impact, depending on the time of sampling. Our findings greatly contribute to increase the knowledge on the effects of multiple stressors caused by the effluent of a power plant and also have important implications for management strategies and conservation ecology, in general.
Transplantation of artificial panels between a polluted and an unpolluted site was used to evalua... more Transplantation of artificial panels between a polluted and an unpolluted site was used to evaluate eutrophication effects on the development of fouling communities in Ilha Grande Bay, SE Brazil. Organic pollution changed the relative dominance of species in the fouling communities of transplanted panels, although, their richness, evenness, and specific composition did not change. The chlorophyte Ulva sp. occurred only in the polluted site and in panels transplanted to it, whereas the bryozoan Aetea lingulata was found only in the unpolluted site and in panels transplanted to this site. These species are therefore good pollution indicators. The best pollution indicators, however, were amphipods and Spionidae polychaetes which formed mucous tubes. These groups had significantly higher values of percent cover (p<0.0001) in the polluted site and in panels transferred to it. The dominance shift is the first evidence that more meaningful changes can occur in the structure of fouling communities on a long-term scale.
Journal of Experimental Marine Biology and Ecology, 2010
Most knowledge of the effects of metals on benthic organisms comes from laboratory studies with s... more Most knowledge of the effects of metals on benthic organisms comes from laboratory studies with subsequent extrapolation to field scenarios. Here, we critically reviewed studies on effects of metals on aquatic organisms, with an emphasis on marine systems to determine the "real" state of our current knowledge about effect of metals on assemblages. These studies include experiments in the laboratory and/or micro-and meso-cosms and those done in the field. Laboratory studies have shown lethal and sub-lethal effects of metals on organisms. There is, however, little evidence that these effects occur in natural environments. Conditions in the laboratory are very different from those in natural habitats. It is sensible, then, to assume that organisms may respond differently under field conditions, but how representative laboratory studies are of field conditions is rarely tested. In contrast, many field studies use patterns to infer processes, without any experimental verification. Of the descriptive papers reviewed here, nearly 50% found differences in the assemblages between contaminated and reference areas. Often, however, the differences were definitely not attributable or could not be unambiguously attributed to the presence of metals, because most of the studies lacked proper controls and/or appropriate temporal or spatial replication. Relatively few experimental studies in the field found clear effects. Where they were found experimentally, differences were generally decreased abundances of populations of some species or reduced diversity of species. Indirect ecological interactions can also occur, where abundances of a superior competitor are reduced by metals, leading to increases in abundances of other species. Properly designed experimental field studies are needed to evaluate the effects of metals on organisms and/or assemblages in natural habitats. This is essential for developing realistic environmental guidelines and managerial strategies for protecting aquatic habitats.
Biofilms are sensitive to environmental conditions. Impacts of contaminants on 2 assemblages are ... more Biofilms are sensitive to environmental conditions. Impacts of contaminants on 2 assemblages are often investigated in laboratories or in meso-cosms. Such experiments are rarely representative of effects of contaminants on biofilms under natural conditions. Studies in 4 real field situations, with enough power to detect impacts, are necessary to develop better understanding of the effects of contaminants on ecological processes. Metals are a common 6 estuarine contaminant and can cause disturbances to the assemblages. Using a new technique to experimentally deliver contaminants to micro-algal assemblages, we tested hypotheses about 8 the effects of zinc on micro-algal biofilm growing on settlement panels in subtidal and intertidal habitats. Control panels deployed for one month in each habitat had significantly 10 greater amounts of biofilm than those exposed to zinc. After three months of deployment, results varied with location. The observed effects on the biofilm did not, however, cause 12 significant changes in the fouling assemblages that developed on the panels.
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Papers by Mariana Mayer-Pinto