Phytoplankton bloom in the Gulf of Alaska Credit: NASA
Results from the longest running cruise by researchers at the University of Alaska/Fairbanks this year showed the largest concentrations of phytoplankton ever seen in nearly 25 years of sampling in the northern Gulf of Alaska.
A massive bloom of phytoplankton, the base of marine food webs, m was spotted from May through September along the Seward Line, a transect of survey stations starting at the mouth of Resurrection Bay, continuing south to the outer edge of the continental shelf and running from the Copper River to beyond Middleton Island, and from Kodiak’s Albatross Bank to offshore waters.
“We’ve never seen this kind of concentration of the phytoplankton in the system.”
Russ Hopcroft is Chair of the Dept. of Oceanography at UAF’s College of Fisheries and Ocean Sciences
The researchers use chlorophyll, the green pigment found in plants, as an indicator of phytoplankton abundance .
“It is the peak production in this system that the whole biology of the Gulf kind of cascades off of, that big infusion of energy and matter into it. Normally the shelf kind of lights up in terms of algal concentration briefly and sporadically. But this past year, the whole shelf was lit up with high chlorophyll for several weeks continuously, which means that there should have been lots of food available for the things that feed upon the plankton, the fish that feed upon that and then the bigger fish, marine mammals and seabirds that use them.”
Alaska’s cooler weather this spring and summer plus extra rain provided fresh water at the ocean surface helps phytoplankton remain closer to the light and build up higher concentrations.
“In the Gulf, because it’s such a seasonal environment, several of the main species rely on this bloom to grow rapidly and store fat up in their bodies, just like bears do. And then they descend deep in the ocean to wait for the following spring to start their life cycle when they lay eggs. And those babies swim up toward the surface and start the whole process over again.”
Hopcroft said it should translate to a lot of energy into the Gulf system.
“I think our expectation would be that the success of animals released into the Gulf system this year will be higher than what we’ve seen during some of these warmer periods. One would hope that we would see that translate into recruitment of various types of fisheries in the next couple of years.”