At 0600 October 3, the Oceanographic Problem Solving (OPS) Class set sail for a 13 hour oceanographic research cruise to western Long Island Sound aboard the R/V SEAWOLF. OPS is a required course of all second-year Master’s students at MSRC. The purpose of the course is to undertake a semester-long, field-oriented research program that answers an hypothesis developed by the class relating to a marine environmental concern of public interest. The cruise, as described below by the class, was designed to assist in answering this year’s question.
The purpose of this year’s Oceanic Problem Solving (OPS) class is to study hypoxia in western Long Island Sound. We are particularly interested in determining whether the hypoxic event that occurred earlier this year was unusual in its timing, onset rate, and forcing functions. Furthermore, we will determine whether the sewage bypass caused by the blackout on August 14th had an effect on the region that experienced hypoxia.
Part of our approach involved field sampling aboard the R/V SEAWOLF on October 3rd. We performed 30 sediment grabs at 15 stations along the east-west axis of Long Island Sound. One of the grabs from each station will be used to determine the abundance and species composition of macro/meiofauna. We hypothesize that the diversity of macro/meiofauna follows an oxygen gradient along the sound. The other grab will be examined for grain size, silver, Clostridium spores, stable carbon isotopes, and silica. We hypothesize that silver and Clostridium spores, which function as sewage tracers, are found in higher concentrations in areas affected by the blackout-induced sewage bypass. Moreover, the stable carbon isotopes and silica will reveal the relative importance of terrestrially-derived organic matter (i.e., sewage) versus marine-derived organic matter (i.e., phytoplankton blooms) in this year’s hypoxic event. The conductivity-temperature-depth (CTD) measurements we took at each station will provide additional information about the water column.
In addition to the sediment grabs and CTD casts, we took two box cores of the sediments. The western core, in the vicinity of Execution Rock, was located in a region that experiences chronic hypoxia, while the eastern core was taken from a mid-sound location, north of Port Jefferson Harbor, where hypoxia occurs less commonly. The layers of sediment in a core preserve historical records of processes that occurred in the water column. We plan to examine organic carbon content, Clostridium, and silica content from each core to determine whether there are differences between the two sites.
The class plans to spend the rest of the semester analyzing data. The presentation and photos are below.
The OPS 2003 class set out to investigate whether a raw sewage bypass during the August 14, 2003 blackout caused the 2003 hypoxic/anoxic event in Long Island Sound. To investigate the hypothesis, the class conducted one research cruise covering the length of the eastern sound. On the cruise, 17 samples of the bottom sediments were taken from the eastern sound for analysis. Back in the lab, the class decided to test for the following parameters: clostridium perfringens, silver, carbon isotopes, macrofauna diversity and abundance, biogenic silica, grain size, and sedimentation rates. As the class worked through the analyses, each person learned new analytical techniques and how to operate in a group environment. With each analysis, the class also learned more about the extent and effects of sewage input into Long Island Sound. As the semester came to a close, the OPS class presented their findings in a seminar on December 12, 2003. Images presented here are snapshots from that presentation. The entire presentation can be viewed in the Slide Gallery.
At the presentation, the class presented a brief summary of how seasonal hypoxia develops, a detailed history of hypoxia in Long Island Sound, results from our lab analyses, a mass balance model, and final conclusions. Upon the completion of the lab analysis, consideration of tides, analysis of chlorophyll-a satellite imagery data, and the construction of a mass balance model, the class came to some interesting conclusions. We concluded that the sewage bypass event contributed to this year’s hypoxic event but was not the main cause. The system was already poised towards hypoxic conditions. Under those conditions, the class believes that other factors including tidal influences, primary production, and the intensity of stratification may have also been important contributions to 2003’s hypoxic event.