Posted on November 6, 2009
As climate change results in warmer, more acidic waters, all marine life is affected. Recent studies have determined that the effect of climate change on marine animals that have a calcium carbonate skeleton like corals, shellfish and pteropods will be severe, with the possible loss, for example, of many coral reefs by 2100. The effect of climate change for many marine animals, like sponges, is simply not known.
Sponges filter and clean the water, provide shelter for commercially important species like juvenile lobsters, and are eaten by many fish and turtles. There are over 8,000 species of sponges living in our oceans, from polar to tropical waters, form the abyss to the intertidal zone. All sponges are sessile, mostly living on hard bottom substrate like rock. Some species are boring sponges, able to bore into the shells of clams, scallops and other shellfish. Over time this weakens the shell, eventually killing the shellfish. The rate of sponge boring may increase as shells get weaker due to climate change, negatively impacting shellfish populations worldwide and shellfish farmers who commercially grow mussels, clams and scallops.
A study by Blue Ocean Institute and Stony Brook University, New York, is examining whether the growth and boring rates of a common boring sponge, Cliona celata, will increase as our oceans become warmer and more acidic (lower pH). We are testing four treatments that differ in pH and temperature based on today’s values and the predicted values for 2100: 1) current temperature and pH, 2) current temperature and low pH; 3) high temperature and current pH; and 4) high temperature and low pH.
Normally in the wild, sponge larvae would attach to scallop shells but in this study we are using small “adult” sponges, which are secured onto scallop shells using rubber bands. Once the sponge has attached to the shell, the rubber band is removed. Preliminary results are very interesting. After 1 month, attachment is nearly 100% for sponges at current (today’s) pH regardless of water temperature. However, only two-thirds of sponges in the more acidic water treatments (lower/future pH) have attached. This suggests that at least for sponge attachment, pH has a greater impact than water temperature, probably through stressing the sponges. This study will run for a few more months to fully determine the impact of climate change on a temperate (cool water) sponge species.
Tropical sponges, such as those that live on coral reefs, may also be affected by warmer, more acidic water. To test this I’m off to Jamaica next week, courtesy of the Disney Worldwide Conservation Fund, to determine the effects of climate change on coral reef sponges. I’ll be posting regular blogs detailing the experiment and results, so stay tuned.