The Nancy Foster Chronicles: Today we feature the mighty coccolithopore and Josue Millan from UPR

Good Morning! Greetings from the Virgin Islands! Now that you have caught your breath from the beautiful sunrise pic above...
Today we will learn about another scientist on board during leg 1: Josué G. Millán!

Josue Millan and his filtration apparatus

Josué is a graduate student in the Biological Oceanography program at the University of Puerto Rico at Mayaguez (UPRM) in the Department of Marine Sciences. His goal is to collect phytoplankton samples, especifically coccolithophores! Coccolithopores are single-celled algae.

Josué tells us that "these tiny organisms have had a great impact on Earth’s history ever since life appeared and spread in the oceans. Coccolithophores are among the most important planktonic communities in the ocean since the late Triassic (250-200Ma). They are nano-sized unicellular golden-brown algae ubiquitously distributed in the oceans where they distinguish themselves from other important phytoplankton communities (such as diatoms and dinoflagellates) by the production of distinctively shaped calcareous structures called "coccoliths."

Coccolitophores and ocean chemistry

“When coccolithophores photosynthesize or construct coccolith plates they change the capacity of oceans to sequester atmospheric CO2 mediating the alkalinity potential of the oceans (aka "C pump"). Massive blooms of coccolithophores can change Earth’s climate by mediating the albedo of oceans and promoting cloud formation by producing DMS, a cloud condensation nuclei. Also as autotrophic organisms, they are essential components to sustain the oceanic food webs. Taking all this into consideration, studying their species composition and abundance in the ocean is of great importance to understand their ecology and interactions with local, regional and global physical and chemical parameters. The dynamics of the coccolithophore community across the tropics is poorly understood and this opportunity, on board the RV Nancy Foster, offers a great location to learn about them.

Coccolitophores are well known for producing blooms over the surface layer of the oceans in the higher latitudes (closer to the Poles) that can be seen even from space, a phenomenon sometimes named "milky water." But way out here in the tropics due to the amount of radiation received from the sun and the low nutrient content of the Caribbean Surface Water, coccolithophores develop better in deeper waters. This characteristic makes it impossible to use of satellites to study their behavior and ecological impact using satellites. “

Collecting water from CTD bottle

At each station, Josué collects and filters a lot of water! He explains us that he collects: “up to 4 L of water from the CTD’s a) surface bottle, b) the chlorophyll maximum and lastly c) deeper than the chlorophyll max peak (sometimes near 200 m in depth!). I filter the water using very specialized and very small filters (0.8 µm Millipore N-Cellulose filters to be specific). These samples will be analyzed back in the lab with a polarized light microscope for ‘standing crops’ (dry biomass) to determine the abundance of coccolithophores. Afterwards, the samples will be examined under a Scanning Electron Microscope (SEM) to assign a species identification and collect additional morphometrics (length, diameter, etc). This information in addition to the abiotic parameters (nutrients, O2,, temperature, etc.) will help us to characterize their ecological settings and better understand their role in this tropical ecosystem.

Here are some more cocoolitophores collected from the southern waters off Puerto Rico that Josue photographed and shared with us!