By Lisa Duchene, SeafoodSource contributing editor
Published on 09 October, 2012
In Wilkinson’s Basin, an area in the Gulf of Maine east of Boston, University of Maine marine scientist Jeffrey Runge is looking for a fat-rich copepod called Calanus finmarchicus. Herring eat these teeny animals, a type of zooplankton.
Since herring are critical lobster bait — and a key forage fish for Gulf of Maine fisheries — calanus are quite important to the lobster market.
Runge, a biological oceanographer based at the Gulf of Maine Research Institute, hopes to see huge numbers of calanus, which spends its winters in the depths of Wilkinson’s Basin, feeding historically productive fishing areas like Jeffreys Ledge and Georges Bank.
But he may instead find a drop. This spring, another scientist reported a five-fold plunge in the amount of Gulf of Maine phytoplankton in 2007, arguing it is a result of record rainfalls and climate change. Rather than a blip, the phytoplankton drop has been sustained.
“A five-fold decrease is pretty important,” says Runge. “[For] reductions like this that are sustained, [we’ve] got to wonder if that influences the system’s carrying capacity.”
If Runge’s work shows a drop in calanus, it will be a sign that this plummet at the base of the food web is affecting other species. Phytoplankton, known as primary producers, convert the sun’s energy into food for all other life in the Gulf of Maine. Fish and shellfish abundance rely on primary production.
While collecting data in the Gulf of Maine, William Balch — a senior research scientist at Bigelow Laboratory for Ocean Sciences in West Boothbay Harbor, Maine — noticed plumes of dissolved organic matter showing up offshore. Washed out from rivers, such plumes typically stay relatively close to shore. Balch also noticed low-salinity water far out at sea.
Those two clues hinted that something very unusual is underway in the Gulf of Maine, so Balch and his team went looking for answers. The result was a paper published March 29 in the scientific journal, Marine Ecology Progress Series.
“We’re looking at absolutely enormous changes that occurred,” says Balch, who analyzed ocean measurements taken between September 1998 and December 2010 in a West-East line from Portland, Maine, east to Yarmouth, Nova Scotia.