Flow Imaging Microscopy Blog

Imaging particle analysis helps phytoplankton diversity studies

Joaquim_GoesJoaquim Goes is a Research Professor at Columbia University in the Department of Marine Biology and Paleo Environment at Lamont-Doherty Earth Observatory. He’s a biological oceanographer with interests spanning from phytoplankton cellular biochemistry to large-scale oceanographic processes. A recent example of his work is from the Arabian Sea, where he began observing massive outbreaks of algal blooms during the winter monsoon. Goes and his colleagues, in collaboration with a team of scientists in India, were able to report that these blooms were taxonomically unlike any bloom species reported before and that their appearance every year was causing a loss of phytoplankton diversity. With the help of shipboard and laboratory experiments, they were able to find out that the spread of low oxygen into the upper sun lit layers of the Arabian Sea was causing these blooms.

Goes recently took part in a cruise sponsored jointly by NASA and NOAA. The primary purpose of the expedition was to validate data being collected by the ocean color satellite Visible Infrared Imaging Radiometer Suite (VIIRS) which measures the color of the sea.  The group included research teams from NASA, NOAA, NRL, JRC (ISPRA) and several other university laboratories that are involved in measurements of the optical properties of sea water. Goes explained that the data collected will be used to validate ocean color based on bio-optical and biogeochemical data being routinely disseminated by NASA and NOAA to the research community all over the world. VIIRS is a relatively new ocean color sensor and it is essential that the data relating to chlorophyll, phytoplankton productivity etc. generated from VIIRS are of the highest quality and consistent with its predecessor ocean color sensors SeaWiFS and MODIS-Aqua.  This consistency in the data sets is an absolute necessity to monitor how biological processes in the oceans are responding to the warming of our planet and climate change.

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Researchers onboard the R/V Nancy Foster

Apart from using ocean color data for estimating chlorophyll and primary productivity in the sea, methods are being developed to discriminate the major phytoplankton groups and their size spectra using satellite ocean color data.  These methods are still in their early stages of development, but validating the collected data will require adequate shipboard datasets of phytoplankton taxonomy and size structure.  Conventional microscopic methods continue to pose the perennial problem of undersampling says Goes. Microscopic identification and enumeration of phytoplankton species in seawater is a very tedious and time consuming process. This is where instruments suited to aquatic research like the FlowCam dynamic imaging particle analysis system can help mitigate this chronic undersampling situation.

Onboard NOAA’s oceanographic research vessel, the R/V Nancy Foster, Goes used the FlowCam to take continuous measurements of phytoplankton size distribution and species composition along the entire cruise track.  The availability of this data at such high spatial resolution is unprecedented, and will make it possible to capture the diversity of phytoplankton in different water masses along the cruise track.

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FlowCam image collage file showing Diatom abundance

During the cruise, the R/V Nancy Foster transacted the Gulf Stream and on each of these occasions the FlowCam was able to capture in real-time, the amazing diversity of phytoplankton across the entire breadth of the Gulf Stream. Closer to the coast on the western margin of the Gulf Stream, the FlowCam revealed phytoplankton communities extremely rich in diatoms. 

The NASA cruise was 12 days and during that time the FlowCam was connected to the ship's underway system and was continuously sampling and taking measurements every 20 minutes. This method generated a very large amount of phytoplankton data that will help the team study the diversity of the species in these different locations.

Goes mentions that a topic that has gained considerable attention in the last two to three years is assessing how much carbon we have in our oceans. In the oceans, phytoplankton are the only group of organisms that are capable of drawing down the CO2 from the atmosphere. They are also important to the food chain; it is for this reason understanding the size and distribution of particles is of considerable relevance to assessing the role of phytoplankton in the oceans carbon cycle and in climate change studies. Assessing the carbon storage capacity of terrestrial and ocean systems are essential to understanding and managing carbon. Many of the open ocean and coastal waters related studies of the carbon storage capacity are called “blue carbon” projects and are now being carried out by many countries around the world as we assess our collective carbon footprint. 

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Topics: Marine Research, User Spotlight, Harmful Algal Blooms, Aquatic Research