Featured Scientist: Karen Selph

Karen in the lab-van whispering to the flow cytometer!

Hello blog, today Dr. Karen Selph from the University of Hawaii at Manoa shares some of her expert insight into the nutrient-limited world! Karen shared with the blog just a few of the multiple experiments she carried out while on board the NOAA Ship Nancy Foster during NF1704 as part of our NOAA RESTORE project. Karen’s main focus was collecting phytoplankton to analyze with a “flow cytometer” – a machine that tells us how many phytoplankton are out there and gives us a rough idea of their types.

In addition, she measured water column light levels used for photosynthesis by phytoplankton with a photosynthetically-active radiation (PAR) sensor that was attached to the CTD rosette. Karen shared with the blog: "The 6 casts that we performed will yield invaluable information on the light regime during the cruise." 

"The nutrient limiting phytoplankton growth in the Gulf of Mexico is nitrogen.  Nitrogen has many forms, and most phytoplankton can only use reduced inorganic forms (e.g., nitrate (NO₃), ammonium (NH₄)).  However, some phytoplankton can use nitrogen gas (N₂), which is in abundant supply.  This is quite a trick, as the chemistry involved is anaerobic (no or low oxygen) and phytoplankton produce oxygen! 

Karen and Lucy carry out one of the PAR casts

On this cruise, we collected many samples to figure out which of the larger nitrogen-fixing organisms that might be present – in particular, Trichodesmium (usually a bane to those who study zooplankton, as it can clog their nets!!).   Additionally, to assess the base line N-isotopic value for Trichodesmium, we collected samples for stable nitrogen isotope analyses.  We even analyzed a sample of Sargassum to figure out its isotopic signature with respect to the other nitrogen-fixing players in the GOM.  Once we get back to the lab, we will also examine our samples under the microscope looking for the presence of other nitrogen-fixers – some diatoms and other species harbor symbionts capable of this remarkable feat!"

The dynamic duo, Tom and Karen processed hundreds of samples during the survey

Shaun, Karen's travel companion, makes some new friends

Featured Scientist: Catalina "Cati" Mena Oliver

Although we are starting to sample in the eastern Caribbean, today's blog features a 'leg 2' participant: Cati! 

Picoplankton and the microbial food web (from Johnson and Lin, 2009)

Processing plankton samples

Catalina Mena Oliver (Cati) joined us in Cozumel back in May to specifically sample picoplankton during Leg 2. Catalina is a PhD student from the Spanish Institute of Oceanography (Oceanographic Centre of  Baleares - Larval Ecology Group), and she is developing her Doctoral Thesis studying the base of the planktonic food web with special interest in the bacterioplankton communities (picoplankton). 

Dynamic oceanographic currents of the western MED
(Balbin et al 2014)

Picophytoplankton (~0.2 to 2 µm) are the smallest autotrophic organisms on Earth and in stratified oligotrophic regions (like the Mediterranean and the Caribbean) can be a key component as biomass source. During our survey we aim to link the community of primary producers to eddy structures, since these communities can be highly influenced by mesoscale dynamics and by changes in resource supply. The phytoplankton size structure and the relative contribution of the different phytoplankton size fractions in terms of carbon biomass strongly affect the carbon transfer and the ecosystem functioning.

Cati shares her research with the science team

Cati shared with our blog: “I am very grateful to FORCES Lab from SEFSC-NOAA to give me the opportunity to participate in the Nancy Foster survey and I hope we could continue this collaboration in the future. The results obtained will help us to assess if the ecosystem is supported by a microbial food web, dominated by the picophytoplankton fraction, which might be crucial as food source not only for bluefin tuna larval ecology but also for other many species”.
We enjoyed to have Cati aboard and hope that she will sail again with us! We look forward to sharing her results in the future with you our loyal reader! 

Trying on the safety suit! (Cati is a LOBSTER)