Among the biologists onboard the NOAA Ship Ronald H. Brown are Dr. Jonna Engström-Öst and Dr. Olivier Glippa from the Novia University of Applied Sciences in Finland. As we mentioned in another post, one of the zooplankton groups being examined on this cruise is copepods, small crustaceans of the subclass Copepoda. Jonna and Olivier are focusing on three copepod species: Calanus pacificus, Calanus marshallae and Eucalanus bungii. These copepods are sampled during our net tows and are highly ecologically important because they provide a link between microalgae and zooplankton-eating fish, especially herring and young salmon. As phytoplankton form the base of the ocean’s food web, zooplankton such as copepods form the second level—still vitally important for the flow of energy within our oceans and a key source of food for many commercially important fish stocks. Before now, Jonna and Olivier have studied copepods in the Baltic Sea and the Atlantic Ocean, and this cruise gives them the opportunity to expand their research into the Pacific!
On the ship, Jonna and Olivier collect plankton at night, because as we mentioned before, many zooplankton spend each day migrating up and down in the water column, staying in deeper, darker water during the day to hide from predators, and moving to the surface at night to feed on phytoplankton. From the sample, Jonna and Olivier pick females who are carrying eggs, which they incubate for 12 hours in order to determine the number of eggs these females release. Other copepods are frozen at -80˚C to conduct further studies back on land. When Jonna and Olivier return to land, they’ll analyze the frozen ones for oxidative stress, an indicator of how rising ocean temperatures and acidification are stressing the copepods. Lab studies have shown that acidifying oceans cause the copepods to release fewer eggs, and that rising temperatures can limit their growth. Jonna and Olivier want to see if these effects are also evident in the oceans; they will also be investigating how pH is going to affect the copepods in the years to come.
In the net tows, our copepod experts have seen some incredible diversity, certainly more than anyone was expecting! Check them out in the photo set that Olivier put together.
Author: Spencer Showalter