Climate change impacts on seabed dwellers

The diversity of seabed-dwelling animals means that this group includes animals with low, moderate, and high vulnerability to climate change. Benthic invertebrates (animals that live on the seabed) share a high sensitivity to increasing sea temperature. Particular types also have a moderate sensitivity to changes in ocean circulation, storm and flood events and ocean chemistry.

As well as corals, the Great Barrier Reef is home to an enormous number of other animals that live on the sea floor. These include molluscs (such as clams), worms, sponges, starfish and sea cucumbers, shrimps and sea squirts – as well as many others. These seabed dwellers are varied and abundant both on reefs and the soft-bottom habitats between reefs.

The seabed dwellers of the Great Barrier Reef perform numerous important ecological roles, and many are commercially important for fisheries.

Rising sea temperature

The effects of rising sea temperatures will vary a great deal among invertebrate species. Animals known to be sensitive to warm temperatures include sponges, sea squirts, molluscs and polychaete worms. Water temperatures affect key aspects of animal physiology, including metabolic rate and timing of reproduction.

Changes to basic functioning of animals due to temperature will affect the survival and reproductive success of certain species, with unpredictable ecological consequences. Predicted increases in extremes of water temperature are also likely to affect the survival of adults and larvae of several species. Highly mobile species such as squids and crabs are likely to be able to escape higher-than-normal temperatures. Immobile creatures, such as sponges and giant clams will be more at risk.

Changes to ocean circulation

Any changes to ocean currents will have profound effects on the benthic invertebrates of the Great Barrier Reef. One key reason for this is that many seabed dwellers begin their lives floating as plankton in the open ocean, before they settle into a final home. Changes to the currents that move these planktonic larvae around the Reef would affect their dispersal to new homes, as well as their access to food in the ocean. For example, larvae could be dispersed to unsuitable habitats for settlement, reducing their rate of survival.

Ocean acidification

All marine creatures that secrete calcium carbonate (limestone) skeletons are sensitive to ocean acidification. Amongst the seabed dwellers, this includes many molluscs, echinoderms (such as starfish), crustaceans, and tiny sand-building creatures known as foraminiferans.

Predicted changes in ocean acidity (pH) will reduce the ability of these creatures to build their shells and skeletons. These sorts of changes will shift the ecological balance on the Great Barrier Reef, with unpredictable but potentially profound consequences. The reduced production of limestone skeletons from benthic invertebrates (such as foraminiferans) will also reduce the supply of new sediments to coral cays and other reef features as the sea level rises.