Saturday, May 24, 2014

Food on the Table

Just like phytoplankton, Joselynn Wallace (Univ. of Rhode Island)
 is taking advantage of the sun.

L to R:  Kathryn Ferguson
Maribel Albarran (RTC-SFSU),
and Andrew Shellenbach
(Western Univ.).
I want to start this post by saying thank you again for keeping up with our adventures. We all enjoy receiving feedback from interested citizens. Please feel free to continue sending me your comments and questions. The scientists on board are excited to know that you are interested in our science, and our day-to-day activities.

Hannah Glover (UW/NOAA-PMEL),
Rachel Vander Giessen (UW-APL)
and Keith Shadle (R/V Melville) are
deploying the "iron" fish to collect water.
By now, you should have an idea of our daily routines at sea.  I would like to shift toward explaining more of the "what and why" of our research, and the scientific objectives of this research cruise. My primary scientific responsibility (which I share with my fellow teacher-at-sea) is providing the team with an estimate of phytoplankton biomass. We do this by collecting water samples from the depths of interest on specific pore-sized filters.  These filters are subsequently analyzed for the concentration of the primary photosynthetic pigment - chlorophyll a.  When conducting oceanographic studies, scientists need to accurately estimate the planktonic biomass in their water samples. A large amount of phytoplankton biomass per unit volume of water means that there's a lot of primary producers or "food" within a sampling area to support the growth of animals at higher levels of the marine food chain.  In other words,  I am responsible for providing an estimate of the concentration of the photosynthetic biomass in the waters we are studying. These photosynthetic organisms convert inorganic carbon into organic carbon (the biomass of algae) by utilizing the sun's energy, and thus are called photoautotrophs,..they are the base of the marine food chain.

Scientists like Julia Matheson
of Western Univ., try to work out when
there's a break in sampling
Phytoplankton biomass  is not easy to measure in the field, and requires specialized instrumentation to both accurately and precisely quantify this important base measure.  Being at sea, we use chlorophyll as a proxy to estimate phytoplankton mass and measure this concentration with a fluorometer. Though the amount of chlorophyll in phytoplankton cells can vary depending on physiological conditions, this has been the standard measure of phytoplankton biomass for the past 60 to 70 years in oceanographic studies World-wide.  It is quick, relatively simple, and provides us with a good estimate for which to plan experiments and further studies. Therefore, high concentrations of chlorophyll mean that there is a high concentration of phytoplankton biomass in the water.  This ultimately provides us with a picture of how much food is "on the table."  The next time you are at the beach or near a lake, take a look at the color of the water.  Clear water generally contains very little biomass, whereas greenish or brownish water has lots of microalgae growing in it.  You can make a quick visual comparison of the biomass in different places using your eyes.  Generally speaking, the darker water supports a 'larger', or more productive food web, ultimately supporting more fish at the top of the aquatic food chain.

Joselynn Wallace (Univ. of Rhode
Island) shows off the artistically designed
styrofoam head thatwill eventually
be sent to the depths of the Pacific,
to be shrunken by the water's pressure.
Our experiments require a relatively large amount of biomass so that we can more accurately measure important biological parameters like photosynthetic efficiency and the lipid content of the phytoplankton cells.  Lipids are water insoluble molecules that are used by phytoplankton as rich energy reserves or structural components (e.g., membranes) depending on whether they are neutral or polar lipids, respectively.  Different growth conditions of the algae influence what types of compounds the cells make, such as essential fatty acids such as Omega-3--which are  found in fish.  However, the fish cannot make these Omega-3 fatty acids; they must obtain them from their diet, and ultimately  phytoplankton.
Lipids are fats that are utilized as stored energy.  When phytoplankton are eaten by zooplankton (microscopic drifting animals), energy is transferred.  Large zooplankton such as krill, are later eaten by larger organisms such as fish and humpback whales.  Energy is required by organisms to reproduce. If phytoplankton are not able to make these lipids, then zooplankton and other organisms in a food web will be adversely affected.

Chris Ikdea of RTC-SFSU is gearing up for his second acidification experiment.
One of the major questions we are testing is how will lowered seawater pH (in other words higher acidity) affect the production of Omega-3 fatty acids? If production is affected, it will alter the overall nutrition of food webs. Phytoplankton may become less (or perhaps more) nutritious to their zooplankton predators.  They won't receive the quality of nutrition they once had.  How will the total amount and composition of food change?  How might fisheries be affected by changes in the base of the food web--the phytoplankton?    How might this affect the food on your table?  Important and yet to be answered questions!

Today, the ship's store was open.  Only three
cruises remain for the "Salty Ship" before
she is retired.
So as you can see, my job is to let the scientists know how much 'planktonic food' is in the water we are using for our deck-board experiments.  If there is very little biomass in the water, the next question is why?  Are there insufficient inorganic dissolved nutrients (nitrogen, phosphate, silicate, iron) in the water to support the growth of the phytoplankton, is the water being too deeply mixed by the wind so there is insufficient sunlight for them to photosynthesize, or perhaps the relatively level of acidity (as measured by pH) is affecting the growth or physiology of the phytoplankton? These are some of the questions we are attempting to answer during this scientific mission.

We are now headed toward Newport, Oregon.  The sun is out, and most of us are done for the day.  We have started a new multi-day deckboard experiment, and look forward collecting more data.  The lab is quiet as we get ready for a new day!

The scientists aboard are glad to hear that you are following us.  Please continue to check in.  You can also follow me on Twitter: @SoCalCostello.

A picture from home.


  1. Vitamin B is major for phytoplankton, what is the source for this nutrient?

    1. Some can make it, others cannot. Not all need it. In some areas near shore, there may be limiting amounts of Vitamin B available.