Big fish eat little fish, little fish (and big whales!) eat zooplankton (tiny shrimp-like creatures, small gelatinous animals, fish larvae…), and these zooplankton eat phytoplankton, the “plants” of the oceans. Floating in every single drop of water of the sunlit oceans, phytoplankton algae communities are at the base of the marine food web. How are these essential organisms affected by the different monsoon regimes?
To answer this question, we are collecting samples for biological and chemical analysis, in addition to the physical measurements acquired with the various instruments deployed.
Our versatile tool for this is called a CTD, measuring real-time Conductivity (from which we get salinity), Temperature, Depth, as well as other parameters like dissolved oxygen and phytoplankton fluorescence throughout the water column, with sampling bottles arranged in a rosette shape all around it. At the click of a button, we remotely close the bottles at particular depths, capturing water and bringing it back onboard. When the CTD rosette comes back on deck, the next step typically involves a few hours of water filtration and preservation! Transported with dry ice at -80°C back to our lab, we will sequence fragments of phytoplankton DNA and count cells. Our Indian collaborators from NIO Visakhapatnam will measure nutrients, pigments, organic carbon, and suspended matter in the water. These advanced techniques will offer a glimpse of the phytoplankton abundances and diversity at different depths and conditions, helping us understand distributions of these tiny yet vital organisms in the Bay of Bengal. C.P. & G.J.