October 1, 2013 — A pair of recent studies show how marine ecosystems are changing as ocean temperatures rise, and that these changes are happening more quickly than expected.
NOAA Fisheries scientists recently worked on two eye-opening investigations into how marine ecosystems are responding as ocean temperatures rise. The first, a meta-analysis of earlier studies, found that marine species are shifting their distribution in response to climate change much faster than expected. The second study zooms in for a closer look at a specific case: the Gulf of Maine, where the food web is shifting in ways that may make it harder for once-great stocks of Atlantic cod to recover from overfishing.
Together these two studies offer a compound view onto what’s happening in the ocean, and they highlight the challenges ahead. As the climate changes, it is more important than ever that we fish sustainably, monitor ocean conditions over time, and consider how our actions affect not just individual species but entire ecosystems as well.
Species are Shifting Towards the Poles
The meta-analysis, published last month in Nature Climate Change, marked the first time scientists set out to compile all previous studies on how marine life is responding to climate change. One common response is range shift—species are moving toward the poles in order to stay cool as things heat up. Ranges are shifting both on land and at sea. The surprising result of this study was that ocean species are marching forward an average of ten times faster than species on land.
"That’s happening across the board," said Frank Schwing, a NOAA Oceanographer who was among the authors of the study. "For all taxa we looked at and no matter where the organisms were in the food web, we consistently found positive results."
In addition to range shifts, the timing of seasonal events such as migrations and spring blooms is also changing. But as species shift in space and time, they’re not all moving together, and this can disrupt the food web.
Many species time their reproductive and migratory cycles around their prey—think of whales migrating to their Arctic feeding grounds in summer, or of young salmon hitting the ocean just as seasonal upwelling brings nutrients to the surface. “When these patterns are disrupted,” said Schwing, “we see mass strandings, starvation, and poor reproductive success.” Events like this have always occurred periodically, such as during El Niño years when the Pacific is unusually warm. This study suggests that such events may occur more frequently in the future.
Read the full story at NOAA Fisheries