Our knowledge of the effects of consumer species loss on ecosystem functioning is limited by a pa... more Our knowledge of the effects of consumer species loss on ecosystem functioning is limited by a paucity of manipulative field studies, particularly those that incorporate inter-trophic effects. Further, given the ongoing transformation of natural habitats by anthropogenic activities, studies should assess the relative importance of biodiversity for ecosystem processes across different environmental contexts by including multiple habitat types. We tested the context-dependency of the effects of consumer species loss by conducting a 15-month field experiment in two habitats (mussel beds and rock pools) on a temperate rocky shore, focussing on the responses of algal assemblages following the single and combined removals of key gastropod grazers (Patella vulgata, P. ulyssiponensis, Littorina littorea and Gibbula umbilicalis). In both habitats, the removal of limpets resulted in a larger increase in macroalgal richness than that of either L. littorea or G. umbilicalis. Further, by the end of the study, macroalgal cover and richness were greater following the removal of multiple grazer species compared to single species removals. Despite substantial differences in physical properties and the structure of benthic assemblages between mussel beds and rock pools, the effects of grazer loss on macroalgal cover, richness, evenness and assemblage structure were remarkably consistent across both habitats. There was, however, a transient habitat-dependent effect of grazer removal on macroalgal assemblage structure that emerged after three months, which was replaced by non-interactive effects of grazer removal and habitat after 15 months. This study shows that the effects of the loss of key consumers may transcend large abiotic and biotic differences between habitats in rocky intertidal systems. While it is clear that consumer diversity is a primary driver of ecosystem functioning, determining its relative importance across multiple contexts is necessary to understand the consequences of consumer species loss against a background of environmental change.
To understand the consequences of biodiversity loss, it is necessary to test how biodiversity–eco... more To understand the consequences of biodiversity loss, it is necessary to test how biodiversity–ecosystem functioning relationships may vary with predicted environmental change. In particular, our understanding will be advanced by studies addressing the interactive effects of multiple stressors on the role of biodiversity across trophic levels. Predicted increases in wave disturbance and ocean warming, together with climate-driven range shifts of key consumer species, are likely to have profound impacts on the dynamics of coastal marine communities. We tested whether wave action and temperature modified the effects of gastropod grazer diversity (Patella vulgata, Littorina littorea, and Gibbula umbilicalis) on algal assemblages in experimental rock pools. The presence or absence of L. littorea appeared to drive changes in microalgal and macroalgal biomass and macroalgal assemblage structure. Macroalgal biomass also decreased with increasing grazer species richness, but only when wave action was enhanced. Further, independently of grazer diversity, wave action and temperature had interactive effects on macroalgal assemblage structure. Warming also led to a reversal of grazer–macroalgal interaction strengths from negative to positive, but only when there was no wave action. Our results show that hydrodynamic disturbance can exacerbate the effects of changing consumer diversity, and may also disrupt the influence of other environmental stressors on key consumer–resource interactions. These findings suggest that the combined effects of anticipated abiotic and biotic change on the functioning of coastal marine ecosystems, although difficult to predict, may be substantial.
Journal of Experimental Marine Biology and Ecology, 2014
The consequences of biodiversity loss in the face of environmental change remain difficult to pre... more The consequences of biodiversity loss in the face of environmental change remain difficult to predict, given the complexity of interactions among species and the context-dependency of their functional roles within ecosystems. Predictions may be enhanced by studies testing how the interactive effects of species loss from different functional groups vary with important environmental drivers. On rocky shores, limpets and barnacles are recognised as key grazers and ecosystem engineers, respectively. Despite the large body of research examining the combined effects of limpet and barnacle removal, it is unclear how their relative importance varies according to wave exposure, which is a dominant force structuring intertidal communities. We tested the responses of algal communities to the removal of limpets and barnacles on three sheltered and three wave-exposed rocky shores on the north coast of Ireland. Limpet removal resulted in a relative increase in microalgal biomass on a single sheltered shore only, but led to the enhanced accumulation of ephemeral macroalgae on two sheltered shores and one exposed shore. On average, independently of wave exposure or shore, ephemeral macroalgae increased in response to limpet removal, but only when barnacles were removed. On two sheltered shores and one exposed shore, however, barnacles facilitated the establishment of fucoid macroalgae following limpet removal. Therefore, at the scale of this study, variability among individual shores was more important than wave exposure per se in determining the effect of limpet removal and its interaction with that of barnacles. Overall, these findings demonstrate that the interactive effects of losing key species from different functional groups may not vary predictably according to dominant environmental factors.
Commercially reared broiler chickens are commonly supplied with drinking water through lines of n... more Commercially reared broiler chickens are commonly supplied with drinking water through lines of nipple drinkers that are positioned above the birds' heads to avoid water leaking and spoiling the litter underfoot. This means that the birds have to peck upwards to obtain water, an action that is very different from the 'scoop' action of natural drinking seen when birds drink from troughs or puddles.
In this study we investigate the welfare implications of this unnatural drinking behaviour imposed by nipple drinkers. We show 1) that chickens have no apparent aversion to the taste of tap water, 2) that they prefer bell drinkers and troughs over nipple drinkers, 3) that the stereotyped 'scoop' action is seen even when birds are drinking from bowls of different heights, 4) that chickens have a strong preference for drinking from nipples that are lower rather than higher and, 5) that when offered a choice between bowls and nipples of the same height, the chickens are indifferent to the method of water presentation.
We conclude that the height at which water is presented to chickens is more important to them than whether they can drink with the natural 'scoop' action. While this might suggest that chicken welfare could be improved by lowering the drinker lines, wet litter causes welfare issues of its own through its effect on hock burn and pododermatitis.
We suggest that drinker systems should be designed so that both aspects of welfare (birds able to drink in their preferred way and clean litter) are possible.
The island of Rodrigues, Mauritius, has recently been established as a producer for the expanding... more The island of Rodrigues, Mauritius, has recently been established as a producer for the expanding beche-demer industry and there is a critical requirement for information concerning its resident holothurian populations. The current study aimed to provide baseline data regarding the distribution of holothurian species inhabiting its shallow lagoon. During July and August 2006, a total of 1,678 holothurians were recorded at 41 survey sites (7,380 m2 ), representing six aspidochirotid, one apodid and one dendrochirotid species. It was estimated that 48.3 million holothurians inhabited the lagoon. The most dominant and widespread species was Holothuria atra (71.68% of individuals). The next most common species were H. leucospilota, Stichopus chloronotus and Synapta maculata (11.08%, 10.85% and 5.24%). The exploited species Actinopyga mauritiana was rarely observed (0.66%). Differences between lagoon region and habitat type were examined. Species distributions were heterogeneous, and three areas have been distinguished for their abundant holothurian fauna. The northeast region harboured high mean densities of H. leucospilota, Stichopus chloronotus and Synapta maculata (0.233, 0.367 and 0.106 m-2 ) and exhibited significantly higher species diversity (H’ = 0.638) than other regions. The highest overall mean densities were found close to shore at the western end of the island, comprising predominantly H. atra (maximum 0.728 m-2 ). Species distributions were strongly related to the measured percentage cover of vegetation, as well as that of sediment. Overall density was significantly greater at vegetation sites than coral/rubble and sediment sites (0.354, 0.177 and 0.193 m-2 ) and diversity was significantly lower at sediment sites than coral/rubble and vegetation sites (0.116, 0.482 and 0.470). Diversity correlated positively with percentage cover of macroalgae and rubble, and negatively with percentage cover of sediment. There were few clear patterns in length for different species. H. atra displayed a negative relationship between length and population density, and length was significantly greater at coral/rubble sites than sediment and vegetation sites (18.98, 15.72 and 14.47 cm). Substratum and shelter associations of holothurian species closely reflected site habitat characteristics. H. atra and H. leucospilota were primarily associated with sediment substrata, and Stichopus chloronotus and Synapta maculata were associated with rubble substrata. Individuals of H. leucospilota and Synapta maculata were frequently under cover (55.5%), whereas H. atra, Stichopus chloronotus and other species were mostly uncovered (90.3%). Recommendations for sustainable management of holothurian resources are proposed.
Our knowledge of the effects of consumer species loss on ecosystem functioning is limited by a pa... more Our knowledge of the effects of consumer species loss on ecosystem functioning is limited by a paucity of manipulative field studies, particularly those that incorporate inter-trophic effects. Further, given the ongoing transformation of natural habitats by anthropogenic activities, studies should assess the relative importance of biodiversity for ecosystem processes across different environmental contexts by including multiple habitat types. We tested the context-dependency of the effects of consumer species loss by conducting a 15-month field experiment in two habitats (mussel beds and rock pools) on a temperate rocky shore, focussing on the responses of algal assemblages following the single and combined removals of key gastropod grazers (Patella vulgata, P. ulyssiponensis, Littorina littorea and Gibbula umbilicalis). In both habitats, the removal of limpets resulted in a larger increase in macroalgal richness than that of either L. littorea or G. umbilicalis. Further, by the end of the study, macroalgal cover and richness were greater following the removal of multiple grazer species compared to single species removals. Despite substantial differences in physical properties and the structure of benthic assemblages between mussel beds and rock pools, the effects of grazer loss on macroalgal cover, richness, evenness and assemblage structure were remarkably consistent across both habitats. There was, however, a transient habitat-dependent effect of grazer removal on macroalgal assemblage structure that emerged after three months, which was replaced by non-interactive effects of grazer removal and habitat after 15 months. This study shows that the effects of the loss of key consumers may transcend large abiotic and biotic differences between habitats in rocky intertidal systems. While it is clear that consumer diversity is a primary driver of ecosystem functioning, determining its relative importance across multiple contexts is necessary to understand the consequences of consumer species loss against a background of environmental change.
To understand the consequences of biodiversity loss, it is necessary to test how biodiversity–eco... more To understand the consequences of biodiversity loss, it is necessary to test how biodiversity–ecosystem functioning relationships may vary with predicted environmental change. In particular, our understanding will be advanced by studies addressing the interactive effects of multiple stressors on the role of biodiversity across trophic levels. Predicted increases in wave disturbance and ocean warming, together with climate-driven range shifts of key consumer species, are likely to have profound impacts on the dynamics of coastal marine communities. We tested whether wave action and temperature modified the effects of gastropod grazer diversity (Patella vulgata, Littorina littorea, and Gibbula umbilicalis) on algal assemblages in experimental rock pools. The presence or absence of L. littorea appeared to drive changes in microalgal and macroalgal biomass and macroalgal assemblage structure. Macroalgal biomass also decreased with increasing grazer species richness, but only when wave action was enhanced. Further, independently of grazer diversity, wave action and temperature had interactive effects on macroalgal assemblage structure. Warming also led to a reversal of grazer–macroalgal interaction strengths from negative to positive, but only when there was no wave action. Our results show that hydrodynamic disturbance can exacerbate the effects of changing consumer diversity, and may also disrupt the influence of other environmental stressors on key consumer–resource interactions. These findings suggest that the combined effects of anticipated abiotic and biotic change on the functioning of coastal marine ecosystems, although difficult to predict, may be substantial.
Journal of Experimental Marine Biology and Ecology, 2014
The consequences of biodiversity loss in the face of environmental change remain difficult to pre... more The consequences of biodiversity loss in the face of environmental change remain difficult to predict, given the complexity of interactions among species and the context-dependency of their functional roles within ecosystems. Predictions may be enhanced by studies testing how the interactive effects of species loss from different functional groups vary with important environmental drivers. On rocky shores, limpets and barnacles are recognised as key grazers and ecosystem engineers, respectively. Despite the large body of research examining the combined effects of limpet and barnacle removal, it is unclear how their relative importance varies according to wave exposure, which is a dominant force structuring intertidal communities. We tested the responses of algal communities to the removal of limpets and barnacles on three sheltered and three wave-exposed rocky shores on the north coast of Ireland. Limpet removal resulted in a relative increase in microalgal biomass on a single sheltered shore only, but led to the enhanced accumulation of ephemeral macroalgae on two sheltered shores and one exposed shore. On average, independently of wave exposure or shore, ephemeral macroalgae increased in response to limpet removal, but only when barnacles were removed. On two sheltered shores and one exposed shore, however, barnacles facilitated the establishment of fucoid macroalgae following limpet removal. Therefore, at the scale of this study, variability among individual shores was more important than wave exposure per se in determining the effect of limpet removal and its interaction with that of barnacles. Overall, these findings demonstrate that the interactive effects of losing key species from different functional groups may not vary predictably according to dominant environmental factors.
Commercially reared broiler chickens are commonly supplied with drinking water through lines of n... more Commercially reared broiler chickens are commonly supplied with drinking water through lines of nipple drinkers that are positioned above the birds' heads to avoid water leaking and spoiling the litter underfoot. This means that the birds have to peck upwards to obtain water, an action that is very different from the 'scoop' action of natural drinking seen when birds drink from troughs or puddles.
In this study we investigate the welfare implications of this unnatural drinking behaviour imposed by nipple drinkers. We show 1) that chickens have no apparent aversion to the taste of tap water, 2) that they prefer bell drinkers and troughs over nipple drinkers, 3) that the stereotyped 'scoop' action is seen even when birds are drinking from bowls of different heights, 4) that chickens have a strong preference for drinking from nipples that are lower rather than higher and, 5) that when offered a choice between bowls and nipples of the same height, the chickens are indifferent to the method of water presentation.
We conclude that the height at which water is presented to chickens is more important to them than whether they can drink with the natural 'scoop' action. While this might suggest that chicken welfare could be improved by lowering the drinker lines, wet litter causes welfare issues of its own through its effect on hock burn and pododermatitis.
We suggest that drinker systems should be designed so that both aspects of welfare (birds able to drink in their preferred way and clean litter) are possible.
The island of Rodrigues, Mauritius, has recently been established as a producer for the expanding... more The island of Rodrigues, Mauritius, has recently been established as a producer for the expanding beche-demer industry and there is a critical requirement for information concerning its resident holothurian populations. The current study aimed to provide baseline data regarding the distribution of holothurian species inhabiting its shallow lagoon. During July and August 2006, a total of 1,678 holothurians were recorded at 41 survey sites (7,380 m2 ), representing six aspidochirotid, one apodid and one dendrochirotid species. It was estimated that 48.3 million holothurians inhabited the lagoon. The most dominant and widespread species was Holothuria atra (71.68% of individuals). The next most common species were H. leucospilota, Stichopus chloronotus and Synapta maculata (11.08%, 10.85% and 5.24%). The exploited species Actinopyga mauritiana was rarely observed (0.66%). Differences between lagoon region and habitat type were examined. Species distributions were heterogeneous, and three areas have been distinguished for their abundant holothurian fauna. The northeast region harboured high mean densities of H. leucospilota, Stichopus chloronotus and Synapta maculata (0.233, 0.367 and 0.106 m-2 ) and exhibited significantly higher species diversity (H’ = 0.638) than other regions. The highest overall mean densities were found close to shore at the western end of the island, comprising predominantly H. atra (maximum 0.728 m-2 ). Species distributions were strongly related to the measured percentage cover of vegetation, as well as that of sediment. Overall density was significantly greater at vegetation sites than coral/rubble and sediment sites (0.354, 0.177 and 0.193 m-2 ) and diversity was significantly lower at sediment sites than coral/rubble and vegetation sites (0.116, 0.482 and 0.470). Diversity correlated positively with percentage cover of macroalgae and rubble, and negatively with percentage cover of sediment. There were few clear patterns in length for different species. H. atra displayed a negative relationship between length and population density, and length was significantly greater at coral/rubble sites than sediment and vegetation sites (18.98, 15.72 and 14.47 cm). Substratum and shelter associations of holothurian species closely reflected site habitat characteristics. H. atra and H. leucospilota were primarily associated with sediment substrata, and Stichopus chloronotus and Synapta maculata were associated with rubble substrata. Individuals of H. leucospilota and Synapta maculata were frequently under cover (55.5%), whereas H. atra, Stichopus chloronotus and other species were mostly uncovered (90.3%). Recommendations for sustainable management of holothurian resources are proposed.
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Read More: http://www.esajournals.org/doi/abs/10.1890/14-0577.1
In this study we investigate the welfare implications of this unnatural drinking behaviour imposed by nipple drinkers. We show 1) that chickens have no apparent aversion to the taste of tap water, 2) that they prefer bell drinkers and troughs over nipple drinkers, 3) that the stereotyped 'scoop' action is seen even when birds are drinking from bowls of different heights, 4) that chickens have a strong preference for drinking from nipples that are lower rather than higher and, 5) that when offered a choice between bowls and nipples of the same height, the chickens are indifferent to the method of water presentation.
We conclude that the height at which water is presented to chickens is more important to them than whether they can drink with the natural 'scoop' action. While this might suggest that chicken welfare could be improved by lowering the drinker lines, wet litter causes welfare issues of its own through its effect on hock burn and pododermatitis.
We suggest that drinker systems should be designed so that both aspects of welfare (birds able to drink in their preferred way and clean litter) are possible.
Read More: http://www.esajournals.org/doi/abs/10.1890/14-0577.1
In this study we investigate the welfare implications of this unnatural drinking behaviour imposed by nipple drinkers. We show 1) that chickens have no apparent aversion to the taste of tap water, 2) that they prefer bell drinkers and troughs over nipple drinkers, 3) that the stereotyped 'scoop' action is seen even when birds are drinking from bowls of different heights, 4) that chickens have a strong preference for drinking from nipples that are lower rather than higher and, 5) that when offered a choice between bowls and nipples of the same height, the chickens are indifferent to the method of water presentation.
We conclude that the height at which water is presented to chickens is more important to them than whether they can drink with the natural 'scoop' action. While this might suggest that chicken welfare could be improved by lowering the drinker lines, wet litter causes welfare issues of its own through its effect on hock burn and pododermatitis.
We suggest that drinker systems should be designed so that both aspects of welfare (birds able to drink in their preferred way and clean litter) are possible.