Showing papers by "Gary A. Kendrick published in 2010"

Decreasing resilience of kelp beds along a latitudinal temperature gradient: potential implications for a warmer future

Abstract: Successful mitigation of negative effects of global warming will depend on understanding the link between physiological and ecological responses of key species. We show that while metabolic adjustment may assist Australasian kelp beds to persist and maintain abundance in warmer waters, it also reduces the physiological responsiveness of kelps to perturbation, and suppresses canopy recovery from disturbances by reducing the ecological performance of kelp recruits. This provides a warning not to rely solely on inventories of distribution and abundance to evaluate ecosystem function. The erosion of resilience is mediated by a shift in adult-juvenile interactions from competitive under cool to facilitative under warm conditions, supporting the prediction that positive interactions may become increasingly important in a warmer future. Kelp beds may remain intact but with a lower threshold for where additional impacts (e.g., extreme storms or reduced water quality) will lead to persistent loss of habitat and ecological function.

Combining environmental gradients to explain and predict the structure of demersal fish distributions

Abstract: Aim Species distribution modelling was used to investigate relationships between benthic environmental variables and patterns of demersal fish species distributions using fish occurrence data collected from spatially sparse point sampling. Our goals were to determine: (1) the relative importance of different environmental variables, (2) whether accurate predictions can be developed from these models, and (3) how a comparison of the models against known species ecology can be used to assess model relevance and to provide further insights that could drive future studies of these species. Location The Recherche Archipelago, southern Western Australia. Methods Fish distribution data were collected using baited remote underwater video systems (BRUVS): environmental characteristics (substrate type, macroalgal type and presence of sessile biota) were derived from the video footage; and water depth was measured with a depth sounder. Two species distribution modelling techniques were used to explore and quantify the contribution of environmental characteristics to distribution models of 10 temperate marine fish species. Results Substrate type (reef, sand, cobble) was the most influential variable, and water depth and macroalgal type influenced the probable occurrence of species even over the same substrate type. The probable occurrences of all but one fish species were predicted very successfully, with observed presences being predicted correctly with accuracies > 76%. These predictions were possible due to strong associations between these species and benthic features recorded in this study (substrate type, depth and macroalgal type). Main conclusions The results demonstrate that the combined influence of multiple environmental gradients must be considered to further develop our understanding of how the environment structures demersal fish distributions. The species distribution models not only agreed with the known ecology of the species examined in detail, but also provided more information on the strength of each environmental attribute and interactions between attributes. These interactions may have previously been misinterpreted as, for example, a depth-driven response. Additional drivers of distribution that were previously not considered, such as the presence of macroalgae, were also found to have influence. This information thus provides a better description of a species’ niche, which is of value to both species management and conservation.

Benthic assemblage composition on subtidal reefs along a latitudinal gradient in Western Australia

Abstract: At regional scales, the distribution of species and the structure of assemblages vary with latitude within many marine and terrestrial systems. The oligotrophic coastal waters of Western Australia (WA) support highly speciose and endemic assemblages, yet spatial patterns in benthic structure are currently poorly known. We examined benthic assemblage composition along a latitudinal gradient of 28.5–33.5°S and a depth gradient of 14–62 m, on subtidal reefs in warm-temperate WA. We surveyed benthos using a remotely triggered digital stills camera. In total, we sampled macroalgae and sessile invertebrates at 201 sites spread across four locations. Percent cover of coarse taxonomic groups and dominant species was estimated from over 2000 photoquadrat samples. We recorded significant differences in benthic assemblage composition between locations, and along depth gradients within each location. However, the magnitude of change with depth was not consistent between locations, and shifts in assemblage composition along the depth gradients were not as pronounced as expected. The percent cover of all dominant benthic groupings differed between locations, and several key taxa, such as the kelp Scytothalia dorycarpa, brown foliose macroalgae, hard corals and sponges, changed predictably along the latitudinal gradient. Our study adopted a coarse taxonomic, but assemblage-wide, approach to describing macrobenthic assemblages, and clear differences between locations and depths were detected. The surveys have provided baseline data on broad scale ecosystem structure against which to detect future ecological change.

Turban snails as habitat for foliose algae: contrasting geographical patterns in species richness

Abstract: Understanding patterns of species richness is a major goal for ecologists, especially in space-limited habitats where many organisms live on top of others (epibiosis, e.g. by algae growing on gastropods in marine environments). We tested the hypotheses that species richness of epiflora on the gastropod Turbo torquatus would not differ between regions withsimilarlyrichalgalfloras,andthatepifloralrichnesswouldincreasewithincreasinggastropodsize.Macroalgalfloras of Hamelin Bay(HB), Marmion (M),Jurien Bay(JB)and Kalbarri (K),Western Australia, ranged from,20 to40species reef � 1 (JB ¼HB ¼MK).EpifloraonsmallT.torquatus(shellareao150cm 2 )didnotdifferamongregionsbutepifloral richness increased with increasing basibiont size. Large T. torquatus (4150cm 2 ) were only found in Hamelin Bay and Marmion, where epifloral richness differed substantially. Epifloral richness was positively related to basibiont size in Marmion but not in Hamelin Bay. However, densities of patellid limpets on large T. torquatus were ,4� higher in Hamelin Bay than in Marmion, implying that limpet grazing suppresses epifloral richness. Epifloral richness on turbinids is not simply associated with regional species pools or gastropod size; rather, biological interactions at the scale of individual basibionts apparently govern broad scale patterns of epibiosis.

The effect of kelp bed disturbance on the abundance and feeding behaviour of fishes on high-relief reefs

Abstract: On high-relief reefs, research has shown that the abundance and diversity of non-cryptic fishes is greater in kelp beds cleared of their canopy compared to those left intact. Greater abundance may be caused by an increase in the availability of food resources associated with damaged kelp, exposed understory algae and newly colonised turfing algae. We investigate the effect of a disturbance to the kelp canopy on two response variables, the abundance and feeding behaviour of six common non-cryptic fish species. We found that Kyphosus sydneyanus (herbivore) and Notolabrus parilus (generalist carnivore) move preferentially into 1-month old clearance plots to feed, whereas Kyphosus cornelii and Odax cyanomelas only graze in these plots incidentally. Kyphosus sydneyanus responded with greater abundance and feeding rate in 1-month old clearance plots that were dominated by the microscopic filamentous brown alga, Hincksia mitchelliae. Small-scale disturbances that remove kelps from kelp canopies result in a shift...