Showing papers by "Gary A. Kendrick published in 2009"

Accelerating loss of seagrasses across the globe threatens coastal ecosystems

Abstract: Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km(2) yr(-1) since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr(-1) before 1940 to 7% yr(-1) since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth.

Effects of protection from fishing on the lengths of targeted and non-targeted fish species at the Houtman Abrolhos Islands, Western Australia

Abstract: The effects of fishing and protection on the length of targeted and non-targeted warm- temperate and tropical reef fishes were studied using baited remote underwater stereo-video cameras at the Houtman Abrolhos Islands, Western Australia. Video images were obtained from inside a marine protected area (MPA) and from 3 replicate fished locations within each of 3 island groups. The effects of protection on the lengths of 6 targeted and 4 non-targeted fish species were examined. Five of the 6 targeted fish species were larger inside MPAs than in areas open to fishing (Choerodon rubescens, Lethrinus miniatus, Lethrinus nebulosus, Pagrus auratus and Plectropomus leopardus). Targeted species were, on average, 48 mm (10%) larger inside MPAs than in areas open to fishing. The vast majority of the individuals of C. rubescens, P. auratus and P. leopardus recorded were smaller than their minimum legal size for first capture. For non-targeted species, only 1 of the 4, Coris auricularis, showed an effect of protection, with the mean length of individuals reduced by 85 mm (33%) inside MPAs relative to areas open to fishing. This study demonstrated clear effects of protection from fishing on the size structure of populations of common warm-temperate and tropical reef fishes.

Characterisation of polymorphic microsatellite markers in the widespread Australian seagrass, Posidonia Australis Hook. F. (Posidoniaceae), with cross-amplification in the sympatric P. Sinuosa

Abstract: We developed 10 polymorphic microsatellite markers in the Australian seagrass Posidonia australis Hook. f. Markers were screened for their ability to detect within- and among-population genetic structure and variation. The markers showed a range in levels of polymorphism from fixed differences between the two sampled seagrass meadows to high levels of heterozygosity. These markers will be used to estimate gene flow across the species range, characterise the mating system through paternity analysis and pollen dispersal, characterise the nature and extent of clonality, and determine the genetic differentiation of local seagrass meadows to provide information on where to source local genetic provenance material for seagrass restoration projects. Seven of the 10 loci also amplified in the sympatric P. sinuosa and will be useful in future studies in population genetics and hybridisation.

Historical and contemporary influence of the Leeuwin Current on the marine biota of the southwestern Australian Continental Shelf and the Recherche Archipelago

Abstract: The influence of the Leeuwin Current on the marine biota of the southern continental shelf of Western Australia is investigated by incorporating geological, oceanographic and evolutionary contexts. The effect of this seasonal current was found to have had an influence for approximately 40 million years as inferred from palaeontological evidence. The effect has been observed despite significant variation in the southward movement of the Leeuwin Current, sea level fluctuations, continental climate and the northward movement of the Australian continent. The marine flora and fauna of the Recherche Archipelago demonstrated the scale of the Leeuwin’s reach with macroalgae, demersal fish, molluscs and other invertebrates having greater affinity with the southern temperate flora and fauna, with a small percentage of subtropical species transported eastward on the Leeuwin Current. A more detailed comparison of benthic macroalgal assemblages indicated significant differences between the Recherche, the southern temperate flora in South Australia at Isles of St Francis and the southwestern flora at Hamelin Bay, near Cape Leeuwin. These macroalgal assemblages were characterized by multiple species differences among the regions but also very high local species turnover (alpha diversity) among locations within each region. The relatively warm water and low seasonal variability in sea temperatures associated with the winter flow of the Leeuwin Current may have played a major role in the persistence of warm water species on the southern coast and the high species turnover we have observed over 18 degrees of longitude. The Leeuwin Current has played a major but not an exclusive role in the evolution and persistence of this flora as well as the species richness and endemism of other marine organisms along the southern coast of Western Australia.

Marine Climate Change in Australia: impacts and adaptation responses: 2009 report card

Abstract: This Report Card summarises present knowledge on marine climate change impacts and identifies knowledge gaps and adaptation responses in Australia. It was produced by an author team representing 35 universities and organisations, a project team from the CSIRO Climate Adaptation National Research Flagship, and a steering group comprising representatives from the sponsor organisations [National Climate Change and Adaptation Research Facility (NCCARF); CSIRO Climate Adaptation National Research Flagship; and the Australian Climate Change Science Program (ACCSP)].

Global warming is eroding the resilience of kelp beds

Abstract: Global warming’s effect on the phenology and distribution of biota threatens the preservation of biodiversity and ecosystem services worldwide. A critical element for conservation success in the future is understanding the link between physiological and ecological responses of key species to multiple concurrent environmental changes. Current evidence for how ocean temperature affects the biota in socio-economically important marine habitats is scant, correlative and provides little causal information on likely synergistic effects of multiple perturbations. Here, we use a comparative experimental approach to demonstrate that, in Australasian kelp beds, physiological adjustment to maintain abundance in a warm ocean climate reduces the ecological competency of juvenile kelp, and that this suppresses the capacity for canopy recovery from physical disturbances of increasing intensity. The implied erosion of resilience is mediated by a shift in adult-juvenile interactions from competitive under cool (benign) to facilitative under warm (adverse) conditions. This supports recent theoretical predictions that positive interactions among organisms will become increasingly important to the maintenance of ecological function in a warmer future. These results demonstrate that, rather than gradually shifting range boundaries pole-ward, the commonly predicted response to global warming, patterns of abundance may be maintained through physiological adjustment while the underlying ecological processes change. The combined effect of ocean warming and increasing disturbances from extreme events will therefore bring kelp beds closer to a threshold where persistent loss of habitat and ecological function will occur if they are subjected to additional stressors (e.g., reduced water quality). Climate Change: Global Risks, Challenges and Decisions IOP Publishing IOP Conf. Series: Earth and Environmental Science 6 (2009) 312008 doi:10.1088/1755-1307/6/1/312008