Readership Survey
Study by U of G ecologist shows threat posed by fishing on marine ecosystems
BY ANDREW VOWLES
A “forest” threatened by overfishing? A new study involving a recently arrived U of G ecologist suggests that agencies and environmental groups hoping to preserve coastal marine ecosystems called kelp forests need to focus far more on the effects of fishing than the impact of pollution.
Controlling fishing may be up to 10 times more effective than pollution mitigation in preserving undersea kelp forests such as those growing around the California Channel Islands between Santa Barbara and Los Angeles, says Prof. Karl Cottenie, Integrative Biology.
The study results appear in a paper published last month in Science by Cottenie and two researchers from the National Center for Ecological Analysis and Synthesis (NCEAS) and the University of California, Santa Barbara.
Cottenie used his academic background in ecology and statistics to analyze data collected during the past quarter-century from around three of the eight islands in the southern California chain.
Understanding the relative impacts of fishing and pollution is important for making decisions about measures from controlling particular activities to preserving areas as nature reserves, he explains.
The research team looked at the abundance of almost 50 species of fish and invertebrates in this area, as well as satellite-derived estimates of amounts of algae, the base of the food chain. They found that fishing accounted for up to 10 times as much variation in numbers of different creatures as did runoff from agriculture, industry or municipal waste water.
Kelp, or seaweed, forms the “trees” of so-called kelp forests attached to the rocky sea floor of shallow coastal waters. These under-water forests, rarely deeper than about 40 metres, are found along both North American coastlines and around the world.
They include some of the world's fastest-growing plants; one kelp species in southern California grows up to 30 centimetres a day. The forest is a complex ecosystem of plants, invertebrates such as sea urchins and starfish, and various species of fish.
The researchers found that overfishing of top predators, including lobster, whelks and rockfish, could allow their prey species to overgraze the plants, effectively threatening the base of the food chain. That overfishing turned out to be a much greater threat than pollution from the nearby mainland.
Cottenie says the study lends support to plans to expand Channel Islands National Park. The nature reserve covers almost 250,000 acres, half of them underwater. One of his co-authors at the NCEAS has played a key role in planning for that marine reserve.
Cottenie spent more than two years in a post-doc position at the NCEAS before coming to Guelph last summer. Earlier he had studied ecology and statistics at the Catholic University of Leuven in his native Belgium.
“It was a perfect match for me,” he says of this project, which involved analyzing piles of data on numerous species, environments and other variables. “To connect them, you need more complicated statistical techniques.”
In another paper in press, the trio discusses their unexpected finding that the kelp forest showed no signs of the effects of global warming. The islands occupy the boundary between areas of warm- and cold-water upwelling (partly explaining the incredible diversity of the forest).
“There was a fear that this boundary would move further north,” he says, adding that the area needs further study.
A third paper in the works will discuss optimum design for kelp forest nature reserves. Comparing kelp forest food webs in two national reserve sites with those in unprotected spots, Cottenie was able to trace differences in these ecosystems directly to the effects of fishing. “There was a clear difference in the community structures.”
How applicable are their results to similar ecosystems in other parts of the world?
“A lot of things are so context-dependent,” he says. “I think this result for the kelp forest will be quite generalizable across the region, but we don't know.”
Here at Guelph, Cottenie plans to use the California research for further studies of dynamics of ecological communities. He's also preparing to study everything from temporary pools in the U of G Arboretum to potholes in Manitoba. “I'm out to understand the world.”
He belongs to Ecology @ Guelph, a new research group of about 40 faculty and 100 graduate students from six departments across campus. It's one of the largest ecology research groups in Canada.
