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Richard B Taylor - One of the best experts on this subject based on the ideXlab platform.
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trophic cascade in a seaweed Epifauna fish food chain
Marine Ecology Progress Series, 2010Co-Authors: Emma M Newcombe, Richard B TaylorAbstract:Trophic cascades have been described in many ecosystems where predation on a herbi- vore affects biomass or productivity of primary producers. While trophic cascades can be particularly strong on rocky reefs, the majority of studies are restricted to sea urchin herbivores despite the pres- ence of numerous other grazers. The present study examines the potential for predation by small fishes on New Zealand rocky reefs to suppress small invertebrate grazers (Epifauna) living on brown seaweeds, with cascading effects on host seaweeds and their epiphytic algae. A trophic cascade was identified in experiments run in outdoor mesocosms. When Epifaunal densities were reduced either artificially or by fish predation, seaweeds were more fouled, but less damaged, than where Epifaunal populations flourished. These experimental findings were not fully consistent with patterns observed at field sites with varying fish densities. Variation in Epifaunal taxonomic structure and seaweed palatability potentially dampened the cascading effect of fish predation on Epifauna. Trophic cas- cades with non-urchin herbivores warrant further study, with a combination of laboratory and field work necessary to understand systems in which herbivores are difficult to manipulate.
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density biomass and productivity of animals in four subtidal rocky reef habitats the importance of small mobile invertebrates
Marine Ecology Progress Series, 1998Co-Authors: Richard B TaylorAbstract:Density, biomass and productivity of animals >0.5 mm were estimated in 4 shallow subtidal rocky reef habitats in temperate northeastern New Zealand. The main objective was to determine the relative contributions of mobile Epifauna (0 5-10 mm) and megafauna (> 10 mm) to the flux of materials on the reef. The habitats surveyed were (1) Carpophyllum plumosuln var. capillifolium forest (Phaeophyceae: Fucales), (2) Ecklonia radiata forest (Phaeophyceae: Laminariales), (3) urchin barrens, and (4) articulated coralline algal turf flats. Epifauna comprised >99.5% of individuals in each habitat. Epifauna dominated biomass (>8ti':11) in the finely structured C~rpophyllum forest and turf flats, where they contributed >g?% of total secondary product~vity. Although lower in the other 2 habitats, the Epifauna1 contribution to total secondary product~vity was still -78":) on the scale of the entire reef. These results show that Epifauna are major contributors to the flux of materials in rocky reef habitats, and should therefore be included in trophic models of these systems. Consumption by fish could only account for -26% of Epifaunal product~on, with the fate of the remainder unknown. Estimated annual secondary productivity within the Carpophyllum torest and turf flats habltats (100 to 115 g AFDW in-' yr-') was hlgher than literature values for a range of soft sediment habitats, and was exceeded only by 2 other hard-bottom communities.
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excretory products of mobile Epifauna as a nitrogen source for seaweeds
Limnology and Oceanography, 1998Co-Authors: Richard B Taylor, Alwyn T V ReesAbstract:The potential for excretory products of mobile Epifauna to be a source of nitrogen for seaweeds was investigated for the fucalean alga Carpophyllum plumosum var. capillifolium at Matheson Bay, northeastern New Zealand. The Epifauna excreted an average of 1.5-2.1 times as much nitrogen as the plants were using. A comparison of rates at which the plants took up ammonium with turnover rates of water in the bed indicated that the plants could derive, on average, up to 79% of the nitrogen they required for growth from ammonium excreted by Epifauna. This value was estimated under the assumption that ammonium excreted by Epifauna was instantaneously diluted into the water mass surrounding the entire bed. In nature, the availability of ammonium to the individual host seaweed should be greater owing to hydrological processes that restrict water flow around the plant.
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Seasonal variation in assemblages of mobile Epifauna inhabiting three subtidal brown seaweeds in northeastern New Zealand
Hydrobiologia, 1997Co-Authors: Richard B TaylorAbstract:Seasonal variation in densities of mobile Epifauna associated with three species of subtidal brown seaweeds (Phaeophyta) was investigated over 2–3 years in northeastern New Zealand. There was strong seasonal variation in the total number of individuals per plant wet weight for Epifauna inhabiting two fucalean seaweeds of the genus Carpophyllum, with Epifaunal densities roughly tracking solar irradiance. In contrast, Epifaunal densities on the laminarian Ecklonia radiata peaked during autumn/winter in the first two years of sampling, and during spring in the third, showing no predictable seasonal pattern of abundance. Few individual Epifaunal taxa showed clear seasonal abundance patterns, even on the Carpophyllum spp. The composition of the Epifaunal assemblage on each seaweed species was fairly constant over time.
Alistair G B Poore - One of the best experts on this subject based on the ideXlab platform.
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biomonitors and the assessment of ecological impacts distribution of herbivorous Epifauna in contaminated macroalgal beds
Environmental Pollution, 2008Co-Authors: David A Roberts, Emma L Johnston, Alistair G B PooreAbstract:We determined metal contents of co-occurring algae Padina crassa and Sargassum sp. in Port Jackson (Australia), and relationships between metal levels and the abundance of Epifaunal amphipods. Copper, lead and zinc concentrations were amongst the highest yet recorded in these algae. Copper, manganese and lead concentrations were far greater in P. crassa than Sargassum sp., possibly due to the low growth of P. crassa in proximity to contaminated sediments. However, in manipulative experiments the proximity of algae to sediments did not explain these differences. The abundance of herbivorous amphipods correlated negatively with the copper content of P. crassa, but not with the lower concentrations in Sargassum sp. The greater contamination of P. crassa led to patchy distributions of metals in algal beds and recolonisation experiments showed Sargassum sp. acts as a refuge from contaminants for Epifauna. The contamination of macroalgae may pose threats to Epifauna in harbours around the world.
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contamination of marine biogenic habitats and effects upon associated Epifauna
Marine Pollution Bulletin, 2008Co-Authors: David A Roberts, Emma L Johnston, Alistair G B PooreAbstract:Habitat-forming organisms are frequently used as biomonitors in marine environments due to a widespread ability to accumulate toxic contaminants. Few studies, however, have considered the consequences of these accumulated contaminants on the abundant and diverse fauna associated with these habitats. In this review, we summarize research which has investigated the contamination of biogenic habitats (including seagrasses, macroalgae, ascidians, sponges and bivalve reefs) and the impact of this contamination on the habitat use, feeding behaviour and survival of associated Epifauna. In many cases, ecological impacts upon Epifauna are not simply predicted by levels of contamination in their habitat, but are determined by the foraging, feeding and reproductive behaviours of the inhabiting organisms. Thus, a thorough understanding of these ecological processes is essential in order to understand the effects of contaminants upon Epifaunal communities. The scope of biomonitoring studies which assess the contamination of biogenic habitats should be expanded to include an assessment of potential effects upon associated Epifauna. When combined with manipulative field experiments such an approach would greatly assist in our understanding of indirect effects of contaminants in these important benthic habitats.
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field and laboratory simulations of storm water pulses behavioural avoidance by marine Epifauna
Environmental Pollution, 2008Co-Authors: David A Roberts, Emma L Johnston, Stefanie Muller, Alistair G B PooreAbstract:Epifaunal communities associated with macroalgae were exposed to storm water pulses using a custom made irrigation system. Treatments included Millipore® freshwater, freshwater spiked with trace metals and seawater controls to allow for the relative importance of freshwater inundation, trace metals and increased flow to be determined. Experimental pulses created conditions similar to those that occur following real storm water events. Brief storm water pulses reduced the abundance of amphipods and gastropods. Freshwater was the causative agent as there were no additional effects of trace metals on the assemblages. Laboratory assays indicated that neither direct nor latent mortality was likely following experimental pulses and that Epifauna readily avoid storm water. Indirect effects upon Epifauna through salinity-induced changes to algal habitats were not found in field recolonisation experiments. Results demonstrate the importance of examining the effects of pulsed contaminants under realistic exposure conditions and the need to consider ecologically relevant endpoints.
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mbaci sampling of an episodic disturbance stormwater effects on algal Epifauna
Marine Environmental Research, 2007Co-Authors: David A Roberts, Alistair G B Poore, Emma L JohnstonAbstract:Abstract Whilst it has been well established that stormwater and associated contaminants negatively impact the quality of recipient waters, the ecological effects of individual stormwater pulses in marine environments are relatively unknown. In this study, the impacts of stormwater outfalls upon water quality and Epifaunal invertebrates inhabiting the alga Sargassum linearifolium are assessed through an MBACI sampling program. Water quality and the abundance of mobile algal Epifauna were recorded at three control sites and three impact sites every 10–12 weeks during dry weather and opportunistically within 24 h of large rain events (>50 ml rainfall in 24 h) and again 4 d after the rain event. Sampling took place during two periods over two separate years and this included four large rainfall events. Following rainfall, salinity dropped rapidly at impact sites close to stormwater outfalls, whilst turbidity increased. Declines in salinity at control sites were slight and turbidity did not differ to ‘before’ periods. The abundance of Epifaunal gastropods and polychaetes were reduced at impact sites 24 h after rain events, but not control sites. The abundance of copepods, amphipods and ostracods, however, were reduced at both control and impact sites for up to 4 d following rainfall. Reductions of these taxonomic groups could not be attributed to stormwater outfalls. Whilst short-term impacts of stormwater runoff were identified for some faunal groups, impacts were not identified for the majority. Instead, effects were harbour-wide (i.e. at control and impact sites), probably in response to the physical disturbance of heavy seas associated with large rain events.
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ecological consequences of copper contamination in macroalgae effects on Epifauna and associated herbivores
Environmental Toxicology and Chemistry, 2006Co-Authors: David A Roberts, Alistair G B Poore, Emma L JohnstonAbstract:Many contaminants of the marine environment are able to chelate to sediments, bind within organic matrices, or be accumulated by organisms such as invertebrates and macroalgae. Marine macroalgae are recognized as effective and efficient bioaccumulators of heavy metals and are sometimes used as bioindicators. Macroalgae support abundant and diverse communities of mobile invertebrates that play key roles in temperate marine environments. However, the potential ecological consequences of the contamination of algae on associated Epifauna are yet to be considered. In this study, the brown alga Sargassum linearifolium was experimentally spiked with copper to assess the effects of contamination on Epifaunal invertebrates in both field and laboratory assays. Copper contamination greatly reduced the colonization of a variety of Epifaunal taxa in the field. Laboratory assays further examined the effects of contaminated macroalgae on habitat preferences, feeding rates, survivorship, and growth in the herbivorous amphipod Peramphithoe parmerong. Adult P. parmerong were less likely to select spiked macroalgae in short-term habitat preference assays and consumed spiked algae at lower rates in feeding assays. In a longer-term (30-d) experiment, survivorship of juvenile amphipods was reduced by up to 75% by contaminated macroalgae, but no effects on the growth of survivors was observed. Heavy metal contamination of macroalgae is a widespread phenomenon that has the potential for substantial negative consequences for associated invertebrate fauna. This issue warrants further investigation by marine ecotoxicologists.
R G Cole - One of the best experts on this subject based on the ideXlab platform.
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mobile Epifauna on subtidal brown seaweeds in northeastern new zealand
Marine Ecology Progress Series, 1994Co-Authors: R B Taylor, R G ColeAbstract:This paper examines the distribution and abundance of mobile Epifauna > 1 mm inhabiting 10 species of subtidal brown seaweeds (Phaeophyceae) in northeastern New Zealand. Cammarid amphipods and isopods were the most abundant animals captured, while a diverse group of gastropods was also present at lower densities F~nely structured seaweeds such as Carpophyllum plumosum var. capillifolium and Cystophora retroflexa tended to support far more animals (up to 2000 ind. per 100 g algal wet wt) than did coarsely structured seaweeds. Comparison of Epifaunas among C. plurnosum growth forms of varying thallus width indicated that this pattern was due to the morphology of the plants rather than differences in their internal composition. There was a trend for isopods with tubular body shapes to live on algal species with narrow fronds, and for dorso-ventrally flattened isopods to live on algae with wide fronds. Most of the seaweed species held Epifaunal assemblages that were distinct from one another in multivariate space, but the individual Epifaunal taxa were generally not strongly host-plant specific, w ~ t h most occurring on more than 1 algal species. I t is suggested that most of the Epifauna have a weak relationship with their host plant. Epifaunal dens~ties on Ecklonia r a d ~ a t a peaked at 6 m depth, and declined with increasing depth.
Karema J Warr - One of the best experts on this subject based on the ideXlab platform.
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impacts of trawling disturbance on the trophic structure of benthic invertebrate communities
Marine Ecology Progress Series, 2001Co-Authors: Simon Jennings, Nicholas Polunin, John K. Pinnegar, Karema J WarrAbstract:Bottom trawling causes chronic and widespread disturbance to the seabed in shallow shelf seas and could lead to changes in the trophic structure and function of benthic communities, with important implications for the processing of primary production and the wider functioning of the marine ecosystem. We studied the effects of bottom trawling on the trophic structure of infaunal and Epifaunal benthic communities in 2 regions (Silver Pit and Hills) of the central North Sea. Within each region, we quantified long-term (over 5 yr) differences in trawling disturbance at a series of sites (using sightings data from fishery protection flights), and related this to differences in the biomass and trophic structure of the benthic community. There were 27- and 10-fold differences in levels of beam trawl disturbance among the Silver Pit and Hills sites respectively, and we estimated that the frequency with which the entire area of the sites was trawled ranged from 0.2 to 6.5 times yr -1 in the Silver Pit and 0.2 to 2.3 times yr -1 in the Hills. The impacts of fishing were most pronounced in the Sil- ver Pit region, where the range of trawling disturbance was greater. Infaunal and Epifaunal biomass decreased significantly with trawling disturbance. Within the infauna, there were highly significant decreases in the biomass of bivalves and spatangoids (burrowing sea-urchins) but no significant change in polychaetes. Relationships between trophic level (estimated using nitrogen stable isotope composition, δ 15 N) and body mass (as log2 size classes) were rarely significant, implying that the larger individuals in this community did not consistently prey on the smaller ones. For Epifauna, the relationships were significant, but the slopes or intercepts of the fitted linear regressions were not significantly related to trawling disturbance. Moreover, mean δ 15 N of the sampled infaunal and epi- faunal communities were remarkably consistent across sites and not significantly related to trawling disturbance. Our results suggest that chronic trawling disturbance led to dramatic reductions in the biomass of infauna and Epifauna, but these reductions were not reflected in changes to the mean trophic level of the community, or the relationships between the trophic levels of different sizes of Epifauna. The trophic structure of intensively trawled benthic invertebrate communities may be a robust feature of this marine ecosystem, thus ensuring the efficient processing of production within those animals that have sufficiently high intrinsic rates of population increase to withstand the levels of mortality imposed by trawling.
David A Roberts - One of the best experts on this subject based on the ideXlab platform.
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biomonitors and the assessment of ecological impacts distribution of herbivorous Epifauna in contaminated macroalgal beds
Environmental Pollution, 2008Co-Authors: David A Roberts, Emma L Johnston, Alistair G B PooreAbstract:We determined metal contents of co-occurring algae Padina crassa and Sargassum sp. in Port Jackson (Australia), and relationships between metal levels and the abundance of Epifaunal amphipods. Copper, lead and zinc concentrations were amongst the highest yet recorded in these algae. Copper, manganese and lead concentrations were far greater in P. crassa than Sargassum sp., possibly due to the low growth of P. crassa in proximity to contaminated sediments. However, in manipulative experiments the proximity of algae to sediments did not explain these differences. The abundance of herbivorous amphipods correlated negatively with the copper content of P. crassa, but not with the lower concentrations in Sargassum sp. The greater contamination of P. crassa led to patchy distributions of metals in algal beds and recolonisation experiments showed Sargassum sp. acts as a refuge from contaminants for Epifauna. The contamination of macroalgae may pose threats to Epifauna in harbours around the world.
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contamination of marine biogenic habitats and effects upon associated Epifauna
Marine Pollution Bulletin, 2008Co-Authors: David A Roberts, Emma L Johnston, Alistair G B PooreAbstract:Habitat-forming organisms are frequently used as biomonitors in marine environments due to a widespread ability to accumulate toxic contaminants. Few studies, however, have considered the consequences of these accumulated contaminants on the abundant and diverse fauna associated with these habitats. In this review, we summarize research which has investigated the contamination of biogenic habitats (including seagrasses, macroalgae, ascidians, sponges and bivalve reefs) and the impact of this contamination on the habitat use, feeding behaviour and survival of associated Epifauna. In many cases, ecological impacts upon Epifauna are not simply predicted by levels of contamination in their habitat, but are determined by the foraging, feeding and reproductive behaviours of the inhabiting organisms. Thus, a thorough understanding of these ecological processes is essential in order to understand the effects of contaminants upon Epifaunal communities. The scope of biomonitoring studies which assess the contamination of biogenic habitats should be expanded to include an assessment of potential effects upon associated Epifauna. When combined with manipulative field experiments such an approach would greatly assist in our understanding of indirect effects of contaminants in these important benthic habitats.
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field and laboratory simulations of storm water pulses behavioural avoidance by marine Epifauna
Environmental Pollution, 2008Co-Authors: David A Roberts, Emma L Johnston, Stefanie Muller, Alistair G B PooreAbstract:Epifaunal communities associated with macroalgae were exposed to storm water pulses using a custom made irrigation system. Treatments included Millipore® freshwater, freshwater spiked with trace metals and seawater controls to allow for the relative importance of freshwater inundation, trace metals and increased flow to be determined. Experimental pulses created conditions similar to those that occur following real storm water events. Brief storm water pulses reduced the abundance of amphipods and gastropods. Freshwater was the causative agent as there were no additional effects of trace metals on the assemblages. Laboratory assays indicated that neither direct nor latent mortality was likely following experimental pulses and that Epifauna readily avoid storm water. Indirect effects upon Epifauna through salinity-induced changes to algal habitats were not found in field recolonisation experiments. Results demonstrate the importance of examining the effects of pulsed contaminants under realistic exposure conditions and the need to consider ecologically relevant endpoints.
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mbaci sampling of an episodic disturbance stormwater effects on algal Epifauna
Marine Environmental Research, 2007Co-Authors: David A Roberts, Alistair G B Poore, Emma L JohnstonAbstract:Abstract Whilst it has been well established that stormwater and associated contaminants negatively impact the quality of recipient waters, the ecological effects of individual stormwater pulses in marine environments are relatively unknown. In this study, the impacts of stormwater outfalls upon water quality and Epifaunal invertebrates inhabiting the alga Sargassum linearifolium are assessed through an MBACI sampling program. Water quality and the abundance of mobile algal Epifauna were recorded at three control sites and three impact sites every 10–12 weeks during dry weather and opportunistically within 24 h of large rain events (>50 ml rainfall in 24 h) and again 4 d after the rain event. Sampling took place during two periods over two separate years and this included four large rainfall events. Following rainfall, salinity dropped rapidly at impact sites close to stormwater outfalls, whilst turbidity increased. Declines in salinity at control sites were slight and turbidity did not differ to ‘before’ periods. The abundance of Epifaunal gastropods and polychaetes were reduced at impact sites 24 h after rain events, but not control sites. The abundance of copepods, amphipods and ostracods, however, were reduced at both control and impact sites for up to 4 d following rainfall. Reductions of these taxonomic groups could not be attributed to stormwater outfalls. Whilst short-term impacts of stormwater runoff were identified for some faunal groups, impacts were not identified for the majority. Instead, effects were harbour-wide (i.e. at control and impact sites), probably in response to the physical disturbance of heavy seas associated with large rain events.
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ecological consequences of copper contamination in macroalgae effects on Epifauna and associated herbivores
Environmental Toxicology and Chemistry, 2006Co-Authors: David A Roberts, Alistair G B Poore, Emma L JohnstonAbstract:Many contaminants of the marine environment are able to chelate to sediments, bind within organic matrices, or be accumulated by organisms such as invertebrates and macroalgae. Marine macroalgae are recognized as effective and efficient bioaccumulators of heavy metals and are sometimes used as bioindicators. Macroalgae support abundant and diverse communities of mobile invertebrates that play key roles in temperate marine environments. However, the potential ecological consequences of the contamination of algae on associated Epifauna are yet to be considered. In this study, the brown alga Sargassum linearifolium was experimentally spiked with copper to assess the effects of contamination on Epifaunal invertebrates in both field and laboratory assays. Copper contamination greatly reduced the colonization of a variety of Epifaunal taxa in the field. Laboratory assays further examined the effects of contaminated macroalgae on habitat preferences, feeding rates, survivorship, and growth in the herbivorous amphipod Peramphithoe parmerong. Adult P. parmerong were less likely to select spiked macroalgae in short-term habitat preference assays and consumed spiked algae at lower rates in feeding assays. In a longer-term (30-d) experiment, survivorship of juvenile amphipods was reduced by up to 75% by contaminated macroalgae, but no effects on the growth of survivors was observed. Heavy metal contamination of macroalgae is a widespread phenomenon that has the potential for substantial negative consequences for associated invertebrate fauna. This issue warrants further investigation by marine ecotoxicologists.