On August 30, 2010 the graduate research methods class left the Savannah State University creek side dock to embark on a CTD cruise. A CTD is an essential oceanographic tool used to measure various water parameters such as Conductivity, Temperature and Depth of sea water.
The CTD can be considered as a device designed to take vital signs of the ocean and house a multitude of sensors which can measure a host of water characteristics at different water depths. The CTD can also record data continuously both vertically as it descends through the water column and horizontally at different depths as it is pulled behind a boat. Information recorded by the sensors on the CTD are electronically sent via a data cable to an on-board computer system (laptop).
One major goal of this research trip was to deploy the CTD and record temperature, conductivity (salinity), density, depth, fluorescence, PAR (Photosynthetic Active Radiation), and oxygen saturation. This information was continuously gathered as the CTD was lowered into the water column to a depth of 1 m above the bottom.
The exercise was structured so that every student had an opportunity to have hands on experience on deploying the CTD, operating the laptop program and retrieving the recorder. One drawback of this device was that it was necessary to have “sea legs” to deploy the recorder without causing damage to the sensors. In rough or choppy waters this may be impossible unless a crane or some other mechanical deployment device was used.
We recorded GPS coordinates to mark the locations of CTD deployment. This is a very important step to perform especially when recording along various transects. The data collection went without any glitches and we obtained a good data set. My part in data analysis was to investigate the photosynthetic component in the water column. Photosynthetic cells in pelagic plants (1-70 µm) such as phytoplankton absorb sunlight to produce necessary sugars required for life, during this process they emit a type of radiation known as fluorescence. The intensity of fluorescence emitted by these plants is recorded by the CTD as it descends through the water column. The fluorescence intensity data sent back to the laptop can therefore give an indication of the abundance and vertical distribution of phytoplankton in the water column. Fluorescence (phytoplankton abundance) was maximum (35.8293 mg/m³) at a depth of 1 m, was lowest between 3 and 6 m, but increased near the bottom at 8 m. These results suggest that there were three layers within the water column that differed in the abundance of phytoplankton, with the lowest abundances occurring in the middle of the water column.
The second part of this activity was to obtain grab samples of benthic substrate by deploying a Ponar grab.
The Ponar grab was very light weight and easy to handle. It was so easy to handle that J.J. slung it out as if she was playing a game of horseshoe! Of course as far as she appeared to throw it—it some how ended up going off 2 inches from the stern of the boat.
Not all Ponar pulls resulted in sediment grabs. There were a few areas that seem to have rocky outcrops or compacted sediments that the grab could not penetrate.
The first couple of tries with the Ponar grab were quite successful! We got a healthy serving of sediments and other benthic organisms which were immediately placed in ziploc bags and kept in a secure place for future analysis.
If you want to get a taste of the lab research experience (with a hint of Island music in the background) simply click on this link: Enjoy!!!!!!!!
If you want to get a taste of the lab research experience (with a hint of Island music in the background) simply click on this link: Enjoy!!!!!!!!
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