2008 Annual Report
Gulf of Maine Research Institute
Spotlight on Science

Understanding Calanus, a tiny organism with a big role in the food web

Stories about ocean life often focus on large, well-known fish and mammals, but researchers at the Gulf of Maine Research Institute (GMRI) and the University of Maine (UMaine) know that understanding microscopic organisms is key to understanding the ecosystem as a whole.

Herring, mackerel, northern right whales, and other species in the Gulf of Maine rely on a type of zooplankton called Calanus finmarchicus as a major food source. Any changes in abundance of Calanus over time could have significant effects on the ecosystem as a whole. Scientists Jeffrey Runge and Andrew Pershing, who are both jointly appointed by GMRI and UMaine, are leading an effort to study the abundance of Calanus in coastal waters, how climate change might impact the population, and the subsequent potential impact on the Gulf of Maine food web.

Two unique research projects are advancing knowledge toward these questions.

UMaine and GMRI have been conducting a zooplankton survey every summer for the past three years with support from the Maine Department of Marine Resources and the National Science Foundation. The survey is an effort to characterize the transition between near-shore and off-shore oceanic conditions. High abundance of zooplankton is mostly found at least three miles off-shore, where whales are most often sighted. Understanding where the dynamic transition line is between these near- and off-shore conditions—and what factors may cause it to shift—can provide insight into where whales are likely to be found. This is of particular interest to the lobster industry, which is making efforts to avoid whale entanglements in their traps in near-shore waters.

Nick Record, Research Associate in Pershing’s Ecosystem Modeling lab, and Rebecca Jones, Research Associate in Runge’s Biological Oceanography lab, are working on the survey.

“Some near-shore coastal areas such as Cape Cod Bay and the Bay of Fundy provide seasonal habitat for whales,” said Record. “This project will provide insight into how those areas differ from the coast of Maine. It will also identify physical influences that could shift the boundary line between near- and off-shore conditions.”

Record and Jones are looking at locations where the concentrations of zooplankton are high enough to be a potential feeding area for whales. For three summers, they spent 10-14 days at sea, collecting data from Portsmouth to just beyond Mount Desert Island. First, Jones lowers a ring net to the seafloor to collect a sample of plankton that she brings back to the lab to count (shown in first photo on right). In the same location, Record lowers down a laser optical plankton counter, which measures every object that passes through (center image on right). This data is combined to determine whether the plankton is evenly distributed or concentrated in layers at different depths (third image on right). Updates from these survey trips are posted at www.seascapemodeling.org.

A second project Jones worked on was a five-year cooperative partnership with fishermen focused on coastal ecosystem monitoring in the Gulf of Maine. Funded by the Northeast Consortium, she worked with fishermen to monitor seasonal changes in the zooplankton community. For the first phase of the project, she went with Portsmouth fishermen every two weeks to two sites—one near-shore, one off-shore—to take zooplankton samples with a mesh ring net and analyze them back in the lab. The second phase included five sites, and for this portion, fishermen from both Portsmouth and Gloucester were trained to collect samples on their own. The chart below shows zooplankton species composition over time at Jeffreys Ledge. This fine-scale research is being used by ecosystem modelers and other researchers to analyze the zooplankton community in the Gulf of Maine ecosystem and how it differs from other regions.

“One of the most interesting parts of the study was looking at the changes in the Calanus community during periods of flooding,” said Jones. “The influx of fresh water seemed to have a significant impact. But the most important outcome of this research is providing baseline data on seasonal patterns of zooplankton, and opening the door to new research questions on Calanus abundance and the potential impacts of climate change.”

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