Let's get Sampling!

North of Havana, Cuba, the sampling is officially underway! 

One goal of this first leg is to better understand the oceanography around Cuba, especially the northern and western regions. For hydrographic modelers in the U.S. working in the Gulf of Mexico and Straits of Florida, this region is of great interest since access to empirical data from around Cuba has been lacking and these waters are tightly connected to surrounding U.S. waters. One way to visualize this connectivity is through the deployment of satellite-tracked surface drifting buoys ("drifters"). Like a high-tech message in a bottle, the drifter floats along with ocean currents periodically communicating its position and other data such as temperature to passing satellites.

Research Associate Akihiro Shiroza deploys a drifter off of the Nancy Foster in 2015

The image below shows the paths of some drifters deployed off of the Yucatan in Mexico in 2006. As you can see, not all of them ended up in the same place. Some ended up in the Gulf of Mexico, one returned to the Caribbean south of Cuba and the other ended up in the Atlantic following the Gulf Stream! This illustrates how fish spawned in similar areas can end up very far from each other.

Drifter trajectories from a larval study in 2006. Each color represents one drifter. Open circles are start points and stars are end points.

Over the first week of sampling we were able to collect lots of physical data - information about currents, temperature, and salinity - as well as biological samples. These biological, or plankton, samples included tuna larvae and possibly even a couple of bluefin tuna larvae (though, of course, we need to confirm these identifications with genetics once we return to the lab!). These physical and biological data were collected from areas of upwelling to the west of Havana and on the eastern end of Guanahacabibes Peninsula (western-most point of Cuba) and also from a mesoscale eddy located on the western side of the Loop Current.

Plankton collected on NF-16-02. From top left to bottom right: Amphipod, larval anglerfish (Ceratioidei), larval blackfin tunas (Thunnus atlanticus), larval squid, larval lobster, larval lionfish (Pterois volitans)

Areas of upwelling are very important for life in the ocean as the deeper waters that are flowing up to the surface bring with them lots of nutrients. Once these nutrients reach a depth where sunlight can penetrate, they are taken up by phytoplankton to help them grow and reproduce and, thus, primary productivity is increased. These areas of increased productivity are great for zooplankters that eat the phytoplankton. And, in turn, as zooplankton (such as copepods) grow and reproduce, these areas become great for larval fish that each the copepods. Those increases in nutrients move right up the food chain! 

Collecting plankton is hard work! Top: Ofelia, Atsushi, and Aki rinse down the net. Middle: Lulu and Raul prepare the sample for sorting by rinsing out the cod end (grey PVC with holes). Bottom: Lulu and Estrella diligently sort through the plankton, pulling out any fish species of interest.

Mesoscale eddies are also significant oceanographic features for very similar reasons. The dynamic flow patterns associated with eddies include areas of upwelling. In addition to the upwelling, the recirculating nature of the eddy currents can sometimes retain weak-swimming plankton within the eddy feature, and, therefore, near those areas of increased productivity. Mesoscale eddies are found throughout all of the world’s oceans and since the advent of satellite techniques that allow us to observe the ocean over large spatial and temporal scales scientists have begun to recognize that eddies may be critical to much life in the ocean. Our work on eddies on this cruise has just begun……stay tuned for much more in depth sampling of mesoscale eddies on leg 2!