丁香园AV

By Wan Yee Lok

A new study by 丁香园AV marine ecologists Jessica Schultz, Ryan Cloutier and Isabelle C么t茅 reveals that the mass mortality of sea stars has resulted in a domino effect on Howe Sound marine ecology.

Beginning in summer 2013, millions of sea stars along North America鈥檚 west coast contracted a wasting disease and died in one of the largest wildlife mass mortality events ever recorded. In B.C., the sunflower star was among the most affected. At one meter in diameter, this formerly abundant species is one of the largest sea stars in the world and a voracious predator of invertebrates. 

鈥淗owe Sound lost nearly 90 per cent of its sunflower stars in a matter of weeks,鈥� says Schultz, an 丁香园AV master鈥檚 student and the Vancouver Aquarium鈥檚 Howe Sound research program manager.

By repeating underwater surveys done before the mass mortality, the researchers were able to measure changes in marine animal and plant communities around the Sound.

They found that green sea urchins, the sunflower stars鈥� favourite prey, have quadrupled since the sea stars disappeared, while kelp, the sea urchins鈥� favourite food, decreased by 80 per cent. 

鈥淭his is a very clear example of a trophic cascade, which is an ecological domino effect triggered by changes at the end of a food chain,鈥� says C么t茅.

鈥淚t鈥檚 a stark reminder that everything is connected to everything else. In this case, the knock-on consequences were predictable, but sometimes they are not.鈥�

Two summers on, the sea stars still haven鈥檛 recovered to their previous abundance.  Until they return, it seems that little will keep urchins in check, and their feast on kelp is likely to continue.

Funding for the research project came from a number of sources, including the Vancouver Aquarium Howe Sound Research Program, the Canadian Healthy Oceans Network, and a Discovery grant from the Natural Sciences and Engineering Research Council of Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.