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 November 13, 2012.

Below is a guest post (her first!) by Dr Emily Darling, about one of the 17 chapters of her PhD dissertation:

The ongoing loss of coral cover and flattening of reef architecture is leading to dramatic and drastic changes for coral reef ecosystems. But not all reef-building corals are affected in the same way. We know that some species are winners and others are losers – but which ones, and why? Corals are the backbone of tropical reefs – identifying changes in their species diversity and composition can help scientists and managers understand what future reefs will look like, and the function and services that reefs can continue to provide.

The biggest hurdle to understanding changes in coral communities is that there are hundreds of different species of scleractinian corals (and a lot of them look alike and are tricky to identify!) We wanted to find a way to simplify the remarkable diversity of scleractinian corals. Classic work in ecology suggests there may only be a few ways that organisms ‘make a living’ in order to survive, grow and reproduce. These fundamental characteristics (and their trade-offs) describe an organism’s life history. With this in mind, we looked for major life histories of reef-building corals.

Where did we look? We headed for the scientific literature and pulled together bits and pieces of data from published articles, taxonomic descriptions and species identification guidebooks on 11 different species characteristics for reef corals all over the world.

We found evidence for up to four major ‘lifestyles’ of reef corals, which we called competitive, stress-tolerant, weedy, and generalist. Each life history has unique characteristics that can allow species to cope with different environments.

  • Competitive corals can grow fast and create canopies that overtop slower growing corals – these corals do really well in good conditions, but not so well when the going gets tough, such as in harsher environments or after disturbances like hurricanes or coral bleaching.
  • Stress-tolerant corals employ a different strategy by growing slowly and living a long time – these species also seem to cope better with harsher environments, like less light on deeper reefs.
  • Weedy corals ‘live fast and die young’ – these are smaller corals that produce baby corals by a type of reproduction called brooding – this might help these pioneer species quickly colonize space that opens up after disturbances.
  • And finally a handful of species have a ‘grab bag’ of characteristics and share features in common with all three of the other groups – we called these corals ‘generalists’.