Plankton Samples
You may have begun to notice that there are several methods of sampling plankton. Each technique is used several times a day at the sampling stations. The baby bongo nets collect the same type plankton as the large bongos. The primary difference is that the samples from the baby bongos are preserved in ethanol, rather than formalin. Chief Scientist David Richardson explained that ethanol is being used more and more as a preservative because the solution allows scientists to test specimens’ genetics. Studying the genetics of plankton samples gives researchers a greater understanding of the ocean’s biodiversity. Genetics seeks to understand the process of trait inheritance from parents to offspring, including the molecular structure and function of genes, gene behavior in the context of a cell or organism, gene distribution, and variation and change in populations.
The big bongos use formalin to preserve plankton samples. Formalin has been used by scientists for decades, mainly because the preservative makes it easier for labs to study the samples. Today’s scientists continue to use formalin because it lets them compare their most recent sampling data to that from years ago. This presents a clearer picture of how marine environments have or have not changed.
Every so often, we use smaller mesh nets for the baby bongos which can catch the smallest of zooplanktons. The specimens from these special bongo nets are sent to CMarZ which stands for Census of Marine Zooplankton. CMarZ are scientists and students interested in zooplankton from around the world who are working toward a taxonomically comprehensive assessment of biodiversity of animal plankton throughout the world ocean. CMarZ samples are also preserved in ethanol. The goal of this organization is to produce a global assessment of marine zooplankton biodiversity, including accurate and complete information on species diversity, biomass, biogeographical distribution, and genetic diversity. [Source — Census of Marine Zooplankton]. Their website is incredible! They have images galleries of living plankton and new species that have been discovered by CMarZ scientists.
Another interesting project that Chief Scientist David Richardson shared with me is the Census of Marine Life. The Census of Marine Life was a 10-year international effort that assessed the diversity (how many different kinds), distribution (where they live), and abundance (how many) of marine life—a task never before attempted on this scale. During their 10 years of discovery, Census scientists found and formally described more than 1,200 new marine species. [Source —Census of Marine Life] The census has a webpage devoted to resources for educators and the public. Contents include videos and images galleries, maps and visualizations, a global marine life database, and links to many other resources.
It is incredibly important that we have institutes like CMarZ, the Census of Marin Life, and the Sea Fisheries Institute in Poland where samples from our EcoMon Survey are sent. Most plankton are so small that you see them best through a microscope. At the lab in Poland, scientists remove the fish and eggs from all samples, as well as select invertebrates. These specimens are sent back to U.S. where the data is entered into models. The information is used to help form fishing regulations. This division of NOAA is called the National Marine Fisheries Service, or NOAA Fisheries. NOAA Fisheries is responsible for the stewardship of the nation’s ocean resources and their habitat. The organization provide vital services for the nation: productive and sustainable fisheries, safe sources of seafood, the recovery and conservation of protected resources, and healthy ecosystems—all backed by sound science and an ecosystem-based approach to management. [Source —NOAA Fisheries]
Vertical CTD Cast
In addition to collecting plankton samples, we periodically conduct vertical CTD casts. This is a standard oceanographic sampling technique that tells scientists about dissolved inorganic carbon, ocean water nutrients, the levels of chlorophyll, and other biological and chemical parameters.
The instrument is a cluster of sensors which measure conductivity, temperature, and pressure. Depth measurements are derived from measurement of hydrostatic pressure, and salinity is measured from electrical conductivity. Sensors are arranged inside a metal or resin housing, the material used for the housing determining the depth to which the CTD can be lowered. From the information gathered during CTD casts, researchers can investigate how factors of the ocean are related as well as the variation of organisms that live in the ocean.
Here’s how a vertical CTD cast works. First, the scientists select a location of interest (one of the stations for the leg of the survey). The ship travels to that position and stays as close to the same spot as possible depending on the weather as the CTD rosette is lowered through the water, usually to within a few meters of the bottom, then raised back to the ship. By lowering the CTD close to the bottom, then moving the ship while cycling the package up and down only through the bottom few hundred meters, a far greater density of data can be obtained. This technique was dubbed a CTD cast and has proven to be an efficient and effective method for mapping and sampling hydrothermal plumes. [Source —NOAA]
During the vertical CTD cast, I am in charge of collecting water samples from specified Niskin bottles on the rosette. The Niskin bottles collected water at different levels: surface water, maximum depth, and the chlorophyll maximum where the greatest amount of plankton are usually found. I take the collected seawater to the lab where a mechanism filters the water, leaving only the remainder plankton. The plankton from the water contains chlorophyll which a lab back on land tests to determine the amount of chlorophyll at different water depths. This gives researchers insight about the marine environment in certain geographic locations at certain times of the year.