Although small starfish may exert significant grazing effects on hard substrata, quantification of these effects has been difficult because of methodological limitations. Previously, caging small starfish for field experiments has failed...
moreAlthough small starfish may exert significant grazing effects on hard substrata, quantification of these effects has been difficult because of methodological limitations. Previously, caging small starfish for field experiments has failed because animals can escape through cage meshes and confounding effects may arise as the starfish can feed on organisms growing on the fences themselves, rather than the surface under investigation. Here, we investigated the efficiency of alternative barrier methods, such as antifouling paint and sticky barriers, for shorter-term experimental manipulation of the herbivorous starfish Parvulastra exigua. Laboratory and field manipulations tested the hypotheses that barriers are efficient in retaining starfish within plots and that the chemical repellent of the barriers does not affect the normal functioning of starfish. The results showed that the sticky barrier did not deter P. exigua, but antifouling paint retained greater numbers of individuals with...
Community ecology has traditionally assumed that the distribution of species is mainly influenced by environmental processes. There is, however, growing evidence that environmental (habitat characteristics and biotic interactions) and...
moreCommunity ecology has traditionally assumed that the distribution of species is mainly influenced by environmental processes. There is, however, growing evidence that environmental (habitat characteristics and biotic interactions) and spatial processes (factors that affect a local assemblage regardless of environmental conditions - typically related to dispersal and movement of species) interactively shape biological assemblages. A metacommunity, which is a set of local assemblages connected by dispersal of individuals, is spatial in nature and can be used as a straightforward approach for investigating the interactive and independent effects of both environmental and spatial processes. Here, we examined (i) how environmental and spatial processes affect the metacommunity organization of marine macroinvertebrates inhabiting the intertidal sediments of a biodiverse coastal ecosystem; (ii) whether the influence of these processes is constant through time or is affected by extreme weat...
It is well known that grazing gastropods, notably limpets, have a structuring effect on rocky shore ecology. The findings to establish this knowledge came from exclusion experiments, often using fences necessitating complex procedural...
moreIt is well known that grazing gastropods, notably limpets, have a structuring effect on rocky shore ecology. The findings to establish this knowledge came from exclusion experiments, often using fences necessitating complex procedural controls. Barriers of anti-fouling copper paint (AP) have been shown to be an effective way to control densities of species in intertidal rocky shores. This method may produce fewer confounding effects than traditional methods of exclosure such as fences/cages and, consequently, is seen as a better solution for excluding grazing molluscs. Nevertheless, the potential artefacts arising from AP as a barrier system are not fully quantified. To better understand the biological impacts of AP and also determine its applicability in field studies, we first determined if using AP as a fence to enclose limpets led to elevated copper levels in test animals. Then, we tested short-term effects of AP on the tenacity, foraging behaviour, grazing pressure and body mass of the limpet Cellana tramoserica in its natural environment over a representative experimental period. AP barriers increased copper concentrations tenfold in C. tramoserica, but this did not affect any of the response variables measured under natural conditions. Overall, our results showed that AP is not as deleterious to limpets as reported from laboratory studies and this supports its use as an effective cageless method to manipulate densities of species on rocky shores in a short time scale.
1.Understanding site fidelity is important in animal ecology, but evidence is lacking that this behaviour is due to an animal choosing a specific location. To discern site selection behaviour it is necessary to consider the spatial...
more1.Understanding site fidelity is important in animal ecology, but evidence is lacking that this behaviour is due to an animal choosing a specific location. To discern site selection behaviour it is necessary to consider the spatial distribution of habitats that animals can occupy within a landscape. Tracking animals and defining clear habitat boundaries, however, is often difficult. 2.We use in situ habitat distribution data and animal movement simulations to investigate behavioural choice in site fidelity patterns. We resolved the difficulty of gathering data by working with intertidal rock pool systems, which are of manageable size and where boundaries are easy to define. Movements of the intertidal starfish Parvulastra exigua were quantified to test the hypotheses that (1) this species displays fidelity to a particular rock pool and that (2) rock pool fidelity is due to site selection behaviour. Observed patterns of individuals (n=10 starfish) returning to a previously occupied r...
Although the ecology of molluscan grazers on intertidal rocky shores is very well documented, there are other abundant grazers, such as herbivorous starfish, that can modify the structure of benthic assemblages yet whose behaviour is...
moreAlthough the ecology of molluscan grazers on intertidal rocky shores is very well documented, there are other abundant grazers, such as herbivorous starfish, that can modify the structure of benthic assemblages yet whose behaviour is poorly understood. The feeding habits of asteroids suggest that they are opportunistic feeders foraging on a broad range of available resources. The reasons for the variation in the food types consumed are not clear. We investigated the feeding habits of the intertidal herbivorous starfish Parvulastra exigua with respect to the temporal and spatial distribution of food and tidal cycles in two populations. We predicted that food choice by P. exigua would be a function of food abundance and that foraging would be independent of tidal cycle. The results showed that this starfish forages on a narrow range of algal food resources, with an apparent selection for microalgae. Foraging during high and low tide was variable across locations; however, most individuals from both populations foraged during any tidal period. These results indicate that P. exigua forages on the same food consumed by many other intertidal grazers, indicating the potential for competition for resources. Grazing on biofilm by P. exigua may play an important role in modifying the structure of algal assemblages on rocky shores by potentially preventing the growth of macroalgae.
Background/Question/Methods Copper is an essential micro-nutrient for plants, though at higher concentrations it causes chloroplast dysfunction and inhibits photosynthesis. Due to their close contact with their environment, unicellular...
moreBackground/Question/Methods Copper is an essential micro-nutrient for plants, though at higher concentrations it causes chloroplast dysfunction and inhibits photosynthesis. Due to their close contact with their environment, unicellular algae are thought to be particularly sensitive to Cu exposure. While brown algae tend to dominate heavy-metal contaminated habitats, little is known about the effect of copper on micro-algal community structure. Additionally, despite it being widely acknowledged that historical contingencies such as land-use legacies and species arrival order affect biodiversity assessment, the effect of disturbance history remains underexplored. This project had two objectives: (1) understand how copper contamination affects micro-algae type and abundance and (2) determine how historical contaminations may interact with other factors. For the first objective, micro-algal assemblages were developed on PVC settlement plates surrounded by copper anti-fouling paint. For ...
This paper presents tests of a model of wound-induced defence in herbaceous plants. Many studies have reported both chemical changes in leaves and changes in the behaviour and/or physiology of herbivores as a result of wounding leaves....
moreThis paper presents tests of a model of wound-induced defence in herbaceous plants. Many studies have reported both chemical changes in leaves and changes in the behaviour and/or physiology of herbivores as a result of wounding leaves. These studies and others have led to the development of various models to explain wound-induced effects both in terms of plant response and
The field of eco-engineering has burgeoned in recent years in response to the proliferation of artificial structures. Adding water-retaining features to seawalls has been successful in increasing biodiversity relative to the surrounding...
moreThe field of eco-engineering has burgeoned in recent years in response to the proliferation of artificial structures. Adding water-retaining features to seawalls has been successful in increasing biodiversity relative to the surrounding structure. Artificial rock pools may not, however, completely mimic natural rock pools. Here, we compared natural colonisation, through dispersal and recruitment, of intertidal mobile species to water-retaining flowerpots on seawalls with that into rock pools. This represents the more usual 'passive' approach to eco-engineering where features are built to enhance biodiversity and are allowed to colonise naturally, as opposed to seeding or transplanting organisms to features. While flowerpots supported some mobile species not found on the seawall, other species common on natural shores did not recruit to flowerpots. Thus, in a second experiment we tested the effectiveness of an 'active' approach through transplanting mobile organisms t...
AbstractCopper based paints are used to prevent fouling on the hulls of ships. The widely documented effect of copper on hull assemblages may be primarily due to direct effects on the invertebrates themselves or indirect effects from...
moreAbstractCopper based paints are used to prevent fouling on the hulls of ships. The widely documented effect of copper on hull assemblages may be primarily due to direct effects on the invertebrates themselves or indirect effects from copper absorbed into the microbial biofilm before settlement has commenced. Artificial units of habitat were exposed to varied regimes of copper to examine (1) the photosynthetic efficiency and pigments of early-colonising biofilms, and (2) subsequent macroinvertebrate assemblage change in response to the different regimes of copper. Macroinvertebrate assemblages were found to be less sensitive to the direct effects of copper than indirect effects as delivered through biofilms that have been historically exposed to copper, with some species more tolerant than others. This raises further concern for the efficacy of copper as a universal antifoulant on the hulls of ships, which may continue to assist the invasion of copper-tolerant invertebrate species.
Herbivory is an important ecological process controlling community structure and function in almost all ecosystems. The effects of herbivores on algal assemblages depend primarily on consumer and algal traits, but the strength of this...
moreHerbivory is an important ecological process controlling community structure and function in almost all ecosystems. The effects of herbivores on algal assemblages depend primarily on consumer and algal traits, but the strength of this interaction is contingent on physical and biological processes. Marine herbivory is particularly intense, where grazers can remove around 70% of primary production. Present understanding of marine herbivory is largely based on well-studied groups including herbivorous fishes, gastropods, crustaceans and sea urchins. Herbivory in other marine taxa is poorly understood, but nonetheless important. For instance, grazing by starfish has the potential to strongly affect algal assemblages. Most starfish feed by extruding their stomach and digesting their food externally. This feeding mechanism is distinctive and complex, and evolutionarily advantageous as it allows individuals to explore many different food sources. Variation in the feeding habits of herbivorous starfish is intriguing because some species are very specialised whereas others are more generalist, and the reasons for those variations are not well understood. Some herbivorous starfish are obligate herbivores while others vary from herbivory to carnivory between life stages or between populations within the same species. The question that then arises is how well we are able to predict grazing pressure from complex feeding habits on benthic systems? This review provides a synthesis of herbivory in starfish showing that: the majority of species forage on microalgae and soft tissue macroalgae; fidelity to an algal diet appears to be related to the size of individuals; and, feeding habits are likely to change with variation in food availability. Directions for future studies on the biology and ecology of herbivorous starfish are suggested to better understand variation in species feeding behaviour. Elucidating the mechanisms that contribute to variation in the behaviour of herbivorous starfish is crucial to predict the effects that these species exert on the structure of marine benthic communities. The influence of omnivorous species also warrants more detailed study. Such investigations are important in the context of climate change, given the potential for species invasions associated with range expansions.
The construction of artificial structures in the marine environment is increasing globally. Eco-engineering aims to mitigate the negative ecological impacts of built infrastructure through designing structures to be multifunctional,...
moreThe construction of artificial structures in the marine environment is increasing globally. Eco-engineering aims to mitigate the negative ecological impacts of built infrastructure through designing structures to be multifunctional, benefiting both humans and nature. To date, the focus of eco-engineering has largely been on benefits for benthic invertebrates and algae. Here, the potential effect of eco-engineered habitats designed for benthic species on fish was investigated. Eco-engineered habitats (" flowerpots ") were added to an intertidal seawall in Sydney Harbour, Australia. Responses of fish assemblages to the added habitats were quantified at two spatial scales; large (among seawalls) and small (within a seawall). Data were collected during high tide using cameras attached to the seawall to observe pelagic and benthic fish. At the larger spatial scale, herbivores, planktivores, and invertebrate predators were generally more abundant at the seawall with the added flowerpots, although results were temporally variable. At the smaller spatial scale, certain benthic species were more abundant around flowerpots than at the adjacent control areas of seawall, although there was no general pattern of differences in species density and trophic group abundance of pelagic fish between areas of the seawall with or without added habitats. Although we did not find consistent, statistically significant findings throughout our study, the field of research to improve fish habitat within human-use constraints is promising and important, although it is in its early stages (it is experimental and requires a lot of trial and error).
Copper based paints are used to prevent fouling on the hulls of ships. The widely documented effect of copper on hull assemblages may be primarily due to direct effects on the invertebrates themselves or indirect effects from copper...
moreCopper based paints are used to prevent fouling on the hulls of ships. The widely documented effect of copper on hull assemblages may be primarily due to direct effects on the invertebrates themselves or indirect effects from copper absorbed into the microbial biofilm before settlement has commenced. Artificial units of habitat were exposed to varied regimes of copper to examine (1) the photosynthetic efficiency and pigments of early-colonising biofilms, and (2) subsequent macroinvertebrate assemblage change in response to the different regimes of copper. Macroinvertebrate assemblages were found to be less sensitive to the direct effects of copper than indirect effects as delivered through biofilms that have been historically exposed to copper, with some species more tolerant than others. This raises further concern for the efficacy of copper as a universal antifoulant on the hulls of ships, which may continue to assist the invasion of copper-tolerant invertebrate species.
The construction of artificial structures in the marine environment is increasing globally. Eco-engineering aims to mitigate the negative ecological impacts of built infrastructure through designing structures to be multifunctional,...
moreThe construction of artificial structures in the marine environment is increasing globally. Eco-engineering aims to mitigate the negative ecological impacts of built infrastructure through designing structures to be multifunctional, benefiting both humans and nature. To date, the focus of eco-engineering has largely been on benefits for benthic invertebrates and algae. Here, the potential effect of eco-engineered habitats designed for benthic species on fish was investigated. Eco-engineered habitats (" flowerpots ") were added to an intertidal seawall in Sydney Harbour, Australia. Responses of fish assemblages to the added habitats were quantified at two spatial scales; large (among seawalls) and small (within a seawall). Data were collected during high tide using cameras attached to the seawall to observe pelagic and benthic fish. At the larger spatial scale, herbivores, planktivores, and invertebrate predators were generally more abundant at the seawall with the added flowerpots, although results were temporally variable. At the smaller spatial scale, certain benthic species were more abundant around flowerpots than at the adjacent control areas of seawall, although there was no general pattern of differences in species density and trophic group abundance of pelagic fish between areas of the seawall with or without added habitats. Although we did not find consistent, statistically significant findings throughout our study, the field of research to improve fish habitat within human-use constraints is promising and important, although it is in its early stages (it is experimental and requires a lot of trial and error).
Climate change is predicted to lead to more extreme weather events, including changes to storm frequency, intensity and location. Yet the ecological responses to storms are incompletely understood for sandy shorelines, the globe's longest...
moreClimate change is predicted to lead to more extreme weather events, including changes to storm frequency, intensity and location. Yet the ecological responses to storms are incompletely understood for sandy shorelines, the globe's longest land-ocean interface. Here we document how storms of different magnitude impacted the invertebrate assemblages on a tidal flat in Brazil. We specifically tested the relationships between wave energy and spatial heterogeneity, both for habitat properties (habitat heterogeneity) and fauna (β-diversity), predicting that larger storms redistribute sediments and hence lead to spatially less variable faunal assemblages. The sediment matrix tended to become less heterogeneous across the flat after high-energy wave events, whereas β-diversity increased after storms. This higher β-diversity was primarily driven by species losses. Significantly fewer species at a significantly lower density occurred within days to weeks after storms. Negative density and biomass responses to storm events were most prominent in crustaceans. Invertebrate assemblages appeared to recover within a short time (weeks to months) after storms, highlighting that most species typical of sedimentary shorelines are, to some degree, resilient to short-term changes in wave energy. Given that storm frequency and intensity are predicted to change in the coming decades, identifying properties that determine resilience and recovery of ecosystems constitute a research priority for sedimentary shorelines and beyond.
The availability of suitable microhabitats has emerged as a key requirement for maximising species diversity gains from ecological engineering of coastal habitats. This includes intertidal boulder field habitat, which is threatened by...
moreThe availability of suitable microhabitats has emerged as a key requirement for maximising species diversity gains from ecological engineering of coastal habitats. This includes intertidal boulder field habitat, which is threatened by increasing urbanisation. We examined faunal use of microhabitats offered by natural intertidal boulders on two continents, South Africa and Australia, and then used artificial boulders to test possible mechanisms driving the observed patterns. Gaps often occur between the undersides of boulders and the substratum on which they lie. Substrata underneath boulders are generally uneven, so gaps can occur anywhere along the boulder undersurface, but gaps are generally larger near the edges of naturally-occurring boulders. Boulder edges were found to provide a microhabitat that had greater densities of almost all macrofauna than closer to the centre of boulder undersides. To test the model that microhabitat use of boulder edges reflects their larger gap sizes (relative to boulder centres), artificial boulders were constructed with the underside surface either flat, or with a gap underneath mimicking the mean size of the gap normally found only under boulder edges (when their average shape is considered among numerous naturally-occurring boulders). Artificial boulders were deployed intertidally for seven weeks, and macrofaunal colonisation was compared (a) between flat boulders and those with gaps, and (b) between edges and centres. Five times more macrofauna colonised boulders with artificial gaps, while no effect of proximity to edges was found when the gap-width was controlled for. The size of gaps under boulders appears to be an important microhabitat feature that can explain a widespread distributional pattern in the diverse assemblages of boulder fields. Such gaps are clearly used by numerous species, including some that are rare or commercially important. Provision and augmentation of this microhabitat should be considered for any ecological engineering project that involves intertidal or subtidal boulders.
Understanding how species respond to the environment in terms of population attributes (e.g. abundance, growth, mortality, fecundity, and productivity) is essential to protect ecologically and economically important species. Nevertheless,...
moreUnderstanding how species respond to the environment in terms of population attributes (e.g. abundance, growth, mortality, fecundity, and productivity) is essential to protect ecologically and economically important species. Nevertheless, responses of macrobenthic populations to environmental features are overlooked due to the need of consecutive samplings and time-consuming measurements. We examined the population dynamics of the filter-feeding bivalve Anomalocardia brasiliana on a tidal flat over the course of one year to investigate the hypothesis that, as accepted for macrobenthic communities, populations inhabiting environments with low hydrodynamic conditions such as tidal flat should have higher attributes than populations inhabiting more energetic habitats (i.e. areas more influenced by wave energy such as reflective and intermediate beaches). This would be expected because the harsh conditions of more energetic habitats force organisms to divert more energy towards maintenance, resulting in lower population attributes.We found that A. brasiliana showed moderate growth and secondary production at the study area. Moreover the recruitment period was restricted to a few months. A comparison with previous studies showed that, contrary to expected, A. brasiliana populations from areas with low hydrodynamic conditions have lower abundance, growth, recruitment and turnover rate. It is likely that morphodynamic characteristics recorded in these environments, such as larger periods of air exposure and lower water circulation, may affect food conditions for filter-feeding species and increase competition. In addition, these characteristics may negatively affect macrobenthic species by enhancing eutrophication processes and anoxia. Overall, our results suggest that models accepted and applied at the macrobenthic community level might not be directly extended to A. brasiliana populations
The availability of suitable microhabitats has emerged as a key requirement for maximising species diversity gains from ecological engineering of coastal habitats. This includes intertidal boulder field habitat, which is threatened by...
moreThe availability of suitable microhabitats has emerged as a key requirement for maximising species diversity gains from ecological engineering of coastal habitats. This includes intertidal boulder field habitat, which is threatened by increasing urbanisation. We examined faunal use of microhabitats offered by natural intertidal boulders on two continents, South Africa and Australia, and then used artificial boulders to test possible mechanisms driving the observed patterns. Gaps often occur between the undersides of boulders and the substratum on which they lie. Substrata underneath boulders are generally uneven, so gaps can occur anywhere along the boulder undersurface, but gaps are generally larger near the edges of naturally-occurring boulders. Boulder edges were found to provide a microhabitat that had greater densities of almost all macrofauna than closer to the centre of boulder undersides. To test the model that microhabitat use of boulder edges reflects their larger gap sizes (relative to boulder centres), artificial boulders were constructed with the underside surface either flat, or with a gap underneath mimicking the mean size of the gap normally found only under boulder edges (when their average shape is considered among numerous naturally-occurring boulders). Artificial boulders were deployed intertidally for seven weeks, and macrofaunal colonisation was compared (a) between flat boulders and those with gaps, and (b) between edges and centres. Five times more macrofauna colonised boulders with artificial gaps, while no effect of proximity to edges was found when the gap-width was controlled for. The size of gaps under boulders appears to be an important microhabitat feature that can explain a widespread distributional pattern in the diverse assemblages of boulder fields. Such gaps are clearly used by numerous species, including some that are rare or commercially important. Provision and augmentation of this microhabitat should be considered for any ecological engineering project that involves intertidal or subtidal boulders
While the consequences of bioinvasions are becoming clearer, our understanding of the environmental and ecological factors driving them is limited due to the complexity of the invasion process. Invasion success can be considered to be...
moreWhile the consequences of bioinvasions are becoming clearer, our understanding of the environmental and ecological factors driving them is limited due to the complexity of the invasion process. Invasion success can be considered to be influenced by characteristics of the receiving assemblage (habitat, food, community interactions) and disturbances. Studies on the effects of the receiving assemblage have typically focused on a single or small subset of species, rather than on complex, multitrophic assemblages. We used an experimental assemblage consisting of more than 30 taxa from multiple trophic levels to evaluate the importance of the presence of this community and disturbance on colonisation by a generalist invader. To achieve this, we compared colonisation between a disturbed and undisturbed community. In addition, we evaluated the effects of the presence of organic matter of a different source (simulating a disturbance event affecting different habitats) on colonisation. A model generalist invader, the isopod Cirolana harfordi, was introduced to patches of oyster beds with (1) undisturbed (live) assemblages, (2) disturbed assemblages, (3) organic matter (using organic matter of a different source), or (4) no assemblage or organic matter. Our results indicated that the presence of an assemblage (disturbed or not) fostered colonisation; however, colonisation was less successful when the assemblage was undisturbed. Results also indicate that for a disturbance event to affect the colonisation of C. harfordi, it has to directly affect the invaded assemblage. These results add to the understanding of the factors driving invasions, which is important to design management strategies.
Patchy distributions within landscapes may be caused by migration in response to different types of habitat patches. Intertidal boulder fields are landscapes in which boulders are discrete habitat patches, often with chitons attached to...
morePatchy distributions within landscapes may be caused by migration in response to different types of habitat patches. Intertidal boulder fields are landscapes in which boulders are discrete habitat patches, often with chitons attached to their under-surfaces. Chiton densities and associations with patch edges differed between boulders overlying coarse-versus fine-sediment types, with greater densities occurring over fine sediments. We tested whether adult migration caused between-boulder distributions by measuring immigration and emigration following experimental replacement of coarse sediments with fine sediment under boulders. We also assessed whether the manipulations altered chiton positions relative to patch edges, and large-scale generality was tested by including data from two continents. The manipulations did not influence the association of chitons with edges or amounts of emigration, but chitons did display positive density-dependent immigration that mirrored their distributional patterns, indicating the importance of immigration. Strikingly , all results were consistent between continents despite involving different species and even genera of chitons. By using boulder fields as a small-scale, easily manipulated landscape, we show that, even in sedentary organisms, patchy distributions within landscapes can be caused by migration alone, without the need to invoke mortality or larval recruitment.
www.elsevier.nl/locate/jembe Spatial and temporal variation in settlement and recruitment of the intertidal barnacle Semibalanus balanoides (L.) (Crustacea: Cirripedia) over a European scale a, b b c d
A key challenge for ecologists is to quantify, explain and predict the ecology and behaviour of animals from knowledge of their basic physiology. Compared to our knowledge of many other types of distribution and behaviour, and how these...
moreA key challenge for ecologists is to quantify, explain and predict the ecology and behaviour of animals from knowledge of their basic physiology. Compared to our knowledge of many other types of distribution and behaviour, and how these are linked to individual function, we have a poor level of understanding of the causal basis for orientation behaviours. Most explanations for patterns of animal orientation assume that animals will modify their exposure to environmental factors by altering their orientation. We used a keystone grazer on rocky shores, the limpet Cellana tramoserica, to test this idea. Manipulative experiments were done to evaluate whether orientation during emersion affected limpet desiccation or body temperature. Body temperature was determined from infrared thermography, a technique that minimises disturbance to the test organism. No causal relationships were found between orientation and (i) level of desiccation and (ii) their body temperature. These results add to the growing knowledge that responses to desiccation and thermal stress may be less important in modifying the behaviour of intertidal organisms than previously supposed and that thermoregulation does not always reflect patterns of animal orientation. Much of what we understand about orientation comes from studies of animals able to modify orientation over very short time scales. Our data suggests that for animals whose location is less flexible, orientation decisions may have less to do with responses to environmental factors and more to do with structural habitat properties or intrinsic individual attributes. Therefore we suggest future studies into processes affecting orientation must include organisms with differing levels of behavioural plasticity.
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...
moreHabitat 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.
On most intertidal rocky shores, marine filamentous cyanobacteria Oscillatoriales are important components of natural biofilms. Some studies have already suggested the nutritional importance of benthic cyanobacteria for intertidal...
moreOn most intertidal rocky shores, marine filamentous cyanobacteria Oscillatoriales are important components of natural biofilms. Some studies have already suggested the nutritional importance of benthic cyanobacteria for intertidal grazers; however, due to the complex nature and technical difficulties of observing and manipulating biofilm in situ, questions related to the relationship between what is available and what is actually consumed and assimilated by intertidal grazers remain unanswered. An alternative approach could be to use an isolated benthic cyanobacterial strain and grow it on surfaces resembling natural rocky shores under controlled laboratory conditions. Researchers can then test hypotheses about feeding behaviours and nutritional implications of grazers feeding on a monospecific biofilm. In this study a procedure to grow a blue-green cyanobacterial biofilm on experimental sandstone units (ESUs) was developed. Evidence of this growth is demonstrated using two established techniques in the analysis of chlorophyll a (Chl a) as a proxy for biomass. Destructive (spectrophotometric) and non-invasive (spectrometric) methods were used to measure the photosynthetic pigment in the benthic filamentous blue-green cyanobacterium Geitlerinema sp. strain CS-897 in a 26-day experiment. Amounts of Chl a were assessed every two days and a continuous and significant growth was observed through time (values ranging from 0.20 µg cm-2 on day 0 to a maximum of 1.10 µg cm-2 on day 20). A strong linear relationship (R2 = 0.87) was found between the spectrophotometric measurements of Chl a and the index NIR/red (R750/R672) obtained from reflectance spectrometry, providing for the first time evidence for the attachment and growth of a mono specific cyanobacterial biofilm on sterilised ESUs under controlled laboratory conditions. The linear regression equation obtained from this relationship can then be used to assess non-destructively the amount of food provided and consumed by key intertidal grazers in future manipulative feeding experiments. These results provide a platform for further studies focusing on the nutritional ecology and feeding behaviour of intertidal grazers. The development of experimental and controlled monospecific and/or mixed benthic biofilms has the potential for new mechanistic insights into key ecological processes dependent on the nutritional choices of benthic grazers.
Loss of marine habitats due to urbanisation has been met with growing research efforts to mitigate ecological impacts through eco-engineering. Research in this area has focused on scientific and engineering outcomes, not considering that...
moreLoss of marine habitats due to urbanisation has been met with growing research efforts to mitigate ecological impacts through eco-engineering. Research in this area has focused on scientific and engineering outcomes, not considering that seawalls are a socially-driven insertion into the environment. Further, management concerns when employing eco-engineering projects include public opinion regarding the aesthetic value of enhanced structures. It is therefore important for ecologists working in urban systems to understand how the public connects with the environment. Here, we used surveys to quantify perceptions of marine environmental issues and attitudes towards an example of eco-engineering research from Sydney Harbour, Australia. We also evaluated the effect of disclosing the costs of enhancing seawalls to participants regarding their support for the initiative. Results showed there was high support for applied management to improve biodiversity. This result is promising for the implementation of future eco-engineering projects. Understanding social values towards our coastlines and new conservation initiatives will provide end users with the tools to optimise coastal management plans. In summary, consideration of public values in urban conservation is essential for effective management.
It is widely accepted that global warming will adversely affect ecological communities. As ecosystems are simultaneously exposed to other anthropogenic influences, it is important to address the effects of climate change in the context of...
moreIt is widely accepted that global warming will adversely affect ecological communities. As ecosystems are simultaneously exposed to other anthropogenic influences, it is important to address the effects of climate change in the context of many stressors. Nutrient enrichment might offset some of the energy demands that warming can exert on organisms by stimulating growth at the base of the food web. It is important to know whether indirect effects of warming will be as ecologically significant as direct physiological effects. Declining body size is increasingly viewed as a universal response to warming, with the potential to alter trophic interactions. To address these issues, we used an outdoor array of marine mesocosms to examine the impacts of warming, nutrient enrichment, and altered top predator body size on a community comprised of the predator (shore crab Carcinus maenas), various grazing detritivores (amphipods) and algal resources. Warming increased mortality rates of crabs, but had no effect on their moulting rates. Nutrient enrichment and warming had near diametrically-opposed effects on the assemblage, confirming that the ecological effects of these two stressors can cancel each other out. This suggests that nutrient enriched systems might act as an energy refuge to populations of species under metabolic constraints due to warming. While there was a strong difference in assemblages between mesocosms containing crabs compared to mesocosms without crabs, decreasing crab size had no detectable effect on the amphipod or algal assemblages. This suggests that in allometrically balanced communities the expected long-term effect of warming (declining body size) is not of similar ecological consequence to the direct physiological effects of warming, at least not over the six week duration of the experiment described here. More research is needed to determine the long-term effects of declining body size on the bioenergetic balance of natural communities. This article is protected by copyright. All rights reserved.
Page 1. MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Vol. 439: 169–180, 2011 doi: 10.3354/meps09307 Published October 20 INTRODUCTION Coastal areas are experiencing increasing levels of anthropogenic ...
... (2001), Hartnoll & Hawkins (1985), and Power (2000) for the Swedish, Isle of ... As well as influencing growth, the pattern of tidal rise and fall may influence mortality rates. ......
more... (2001), Hartnoll & Hawkins (1985), and Power (2000) for the Swedish, Isle of ... As well as influencing growth, the pattern of tidal rise and fall may influence mortality rates. ... Another important factor influencing community dynamics on Swedish shores is the occurrence of sea ice. ...
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... have limited detailed taxonomic studies in intertidal habitats (but see Potts 1980, Whit-ton & Potts 1982, Nagarkar & Williams 1999). ... Sea-sonal and spatial variation in food resources could...
more... have limited detailed taxonomic studies in intertidal habitats (but see Potts 1980, Whit-ton & Potts 1982, Nagarkar & Williams 1999). ... Sea-sonal and spatial variation in food resources could clearly have important implications for population dynamics and life history strategies of ...