Researchers from NOAA’s Pacific Marine Environmental Laboratory (PMEL) and University of Alaska Fairbanks (UAF) have departed on the NOAA ship Ronald H. Brown to survey ocean chemistry and its connections to the base of the food web in the Gulf of Alaska.
“This cruise offers the unique opportunity for data to be collected throughout the Gulf of Alaska,”said Dr. Jessica Cross, chief scientist for this expedition, “This will be the first broad scale, comprehensive survey in this area.”
Ocean acidification is the decrease in pH and carbonate ions in seawater due to an increased amount of carbon dioxide in the atmosphere, a portion of which ultimately ends up in the ocean. High latitude, cold waters like those in the Gulf of Alaska can hold more carbon dioxide, making them vulnerable to the effects of ocean acidification. To understand ocean acidification, scientists on board will measure the carbonate chemistry of Alaskan waters, including the amount of carbon dioxide and carbonate ions in the water. The carbonate ion is a building block for organisms with shells or skeletons like plankton (microscopic plants or animals), crabs and corals. One of the microscopic organisms found in these waters is the pteropod, a sea snail, which commercial fish species, such as salmon feed on.
“Scientists can see the impacts of current day carbon conditions on the shells of pteropods by measuring the dissolution of their shells,” Dr. Shallin Busch, a Research Ecologist at the NOAA Ocean Acidification Program and Northwest Fisheries Science Center explains.
The team from University of Alaska will be looking at the distribution of pteropods and other microscopic plants (phytoplankton) and animals (zooplankton) during the survey. Zooplankton in Alaskan waters support many fisheries, including salmon harvested in Alaskan waters and waters off the U.S. West Coast. Salmon populations from both regions live in Alaska’s ocean waters for part of their life cycle. Animals such as sea birds and mammals also eat zooplankton Scientists continue to collect plankton in some parts of the Gulf of Alaska to understand how their distribution is affected by climate, but they have not collected such data from the entire Gulf in decades.
“By looking at much bigger expanses of these waters, we might see a relationship between the distribution of these organisms and the chemistry or physical properties of the water,” said Dr. Russell Hopcroft, professor at the University of Alaska. “This could allow us to see big patterns in composition or abundance of organisms and the chemistry of the water in which they are found.”
“This is the first time that broad-scale sampling to characterize the carbonate landscape in the Gulf of Alaska will be done, and it is really exciting that the cruise will simultaneously quantitatively sample plankton We need broad-scale biological monitoring to go along with the carbonate chemistry sampling to understand how ocean acidification may change ecosystems, ” said Dr. Busch. “We still don’t have enough information to know exactly which organisms are sensitive to shifts in ocean chemistry in Alaskan waters, but by collecting this data set now we will be able to look back at a future date and see what has changed and determine what good indicators of change may be.”
Another aspect of the cruise is to look forward. The chemical data collected on this cruise, particularly in waters in the eastern Gulf, will be used to refine models to predict carbonate chemistry shifts in this region.
“There are important invertebrate fisheries such as bottom-dwelling geoducks, razor clams, and a crabs in the Eastern Gulf of Alaska,” said Dr. Samantha Siedlecki, a research scientist at JISAO, “and we don’t have a good idea of the chemistry in this area.”
The data collected on this cruise will allow scientists at University of Washington’s Joint Institute for the Study of the Atmosphere and Ocean (JISAO) to make more accurate predictions of future conditions of the Gulf of Alaska.
“Alaska has a rich tradition of using a truly integrated research approach to study ecosystems,” said Dr. Cross, “The multidisciplinary approach on this survey will give us a comprehensive chemical to biological perspective across a large area of the Gulf of Alaska. This cruise is an exciting opportunity and we hope to see this kind of approach become a standard in the future.”