Coral larval ecology and biogeography in a warming ocean

Woolsey, Erika S. (2014) Coral larval ecology and biogeography in a warming ocean. PhD thesis, James Cook University.

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Abstract

The distribution and diversity of species is changing in response to global climate change, particularly increased temperature. However, the specific response, both within and among species, is often dependent on geographical location. For instance, the greatest negative effects of global warming are predicted to occur in the tropics because lowlatitude species tend to have a narrower range of thermal tolerance when compared with higher latitude species. Corals are expected to be at a particularly high risk from increased temperatures because thermal anomalies as little as 1°C above average annual summer maximums can cause mass bleaching in adult coral assemblages. Raised temperatures are also deleterious to coral larvae (the dispersive life stage), which are crucial for recruitment and replenishment of coral populations. However, studies into the effects of temperature on these early life stages have so far been limited to single locations and upper thermal limits. In addition, the effects of reduced temperature are also rarely examined. Therefore, the aims of my PhD were to 1) determine thermal tolerance breadths for the development and survival of coral larvae 2) assess the extent to which this tolerance varies across space and among species 3) test whether differences between adult coral assemblages across a dispersal barrier can be predicted by species traits, in particular larval traits including the rate of development and mode of larval nutrition. To address these aims, I combined small-scale larval experiments at three sites along the east coast of Australia, and large-scale biogeographical analyses. My major findings were that 1) raised temperatures increased the proportion of abnormal embryos, increased the rate of larval development and decreased larval lifespan, 2) lowered temperatures reduced the rate of development but did not affect larval lifespan 3) in relation to local ambients, upper thermal thresholds were greater in coral larvae from higher latitudes 4) the rate of larval development was the best predictor for the differences in assemblage structure between the Great Barrier Reef and Lord Howe Island, with coral cover at Lord Howe Island overwhelmingly dominated by species which brood larvae that are ready to settle on release. Although local temperature ranges projected by the end of the century exceed the thermal tolerance breadths at most locations, rising temperatures pose a greater threat to low-latitude coral populations because of their narrower range of thermal tolerance. Furthermore, the effects of ocean warming are likely to vary among species. In particular, species with larvae that develop quickly may be pre-adapted to survive changing climates because they are better colonisers and therefore have a greater potential to expand their range size to track suitable climate.

Item ID: 40732
Item Type: Thesis (PhD)
Keywords: biogeography; climate change; climatic factors; cold tolerance; coral ecology; coral reef ecology; coral reefs; corals; development; dispersal; global warming; Great Barrier Reef; larvae; larval ecology; Lizard Island; Lord Howe Island; marine ecology; ocean warming; One Tree Island; Queensland; self-fertilization; thermal tolerance
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 2: Woolsey, Erika S., Byrne, Maria, and Baird, Andrew H. (2013) The effects of temperature on embryonic development and larval survival in two scleractinian corals. Marine Ecology Progress Series, 493. pp. 179-184.

Chapter 3: Woolsey, Erika (2012) Self-fertilization suppresses thermal tolerance in embryos of reef-building coral. In: Proceedings of the 12th International Coral Reef Symposium, pp. 1-4. From: 12th International Coral Reef Symposium, 9-13 July 2012, Cairns, QLD, Australia.

Appendix I: Woolsey, Erika, Bainbridge, Scott J., Kingsford, Michael J., and Byrne, Maria (2012) Impacts of cyclone Hamish at One Tree Reef: integrating environmental and benthic habitat data. Marine Biology, 159 (4). pp. 793-803.

Appendix I: Woolsey, E., Byrne, M., Webster, J.M., Williams, S., Pizarro, O., Thornborough, K., Davies, P., Beaman, Robin, and Bridge, Thomas (2013) Ophiopsila pantherina beds on subaqueous dunes off the Great Barrier Reef. In: Johnson, Criag, (ed.) Echinoderms in a Changing World. Taylor & Francis, London, pp. 175-179.

Other publications:

Schmidt-Roach, Sebastian, Miller, Karen J., Woolsey, Erika, Gerlach, Gabriele, and Baird, Andrew H. (2012) Broadcast spawning by Pocillopora species on the Great Barrier Reef. PLoS ONE, 7 (12). e50847.

Schneider, Kenneth, Silverman, Jacob, Woolsey, Erika, Eriksson, Hampus, Byrne, Maria, and Caldeira, Ken (2011) Potential influence of sea cucumbers on coral reef CaCO3 budget: a case study at One Tree Reef. Journal of Geophysical Research: biogeosciences, 116. G04032-G04032.

Webster, Jody M., Beaman, Robin J., Bridge, Thomas, Davies, Peter, Byrne, Maria, Williams, Stefan, Manning, Phil, Pizarro, Oscar, Thornborough, Kate, Woolsey, Erika, Thomas, Alex, and Tudhope, Sandy (2008) From corals to canyons: the Great Barrier Reef margin. EOS, 89 (24). pp. 217-218.

Date Deposited: 14 Oct 2015 03:50
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050101 Ecological Impacts of Climate Change @ 34%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 33%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060808 Invertebrate Biology @ 33%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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