To see the full report and the student publications, go to this web page and click on "Boston University Marine Program Undergraduate Studies on Oyster Pond"
During the summer of 2002 we jointly supervised two undergraduate students in a National Science Foundation training program, directed by Professor Ivan Valiela of the Boston University Marine Program, designed to provide research experience for undergraduates. These students, Stacy Barron (Bowdoin College), and Carolyn Weber (Cornell College), conducted experiments on nutrient limitation and salinity in Oyster Pond. the students also conducted 3 transects along four stations in Oyster Pond, where they measured chlorophyll, inorganic nitrogen (N) and phosphorous (P) concentrations, and salinity at 3 depths, as well as secchi depth, light, and dissolved oxygen.
Nutrients are now generally recognized as the largest pollution problem for coastal rivers and bays. In the United States, two-thirds of these ecosystems are moderately to severely degraded by nutrients. One symptom is excessive growth of phytoplankton, which are the microscopic, photosynthetic organisms (mostly algae, but also some types of bacteria) that make up the base of the food chain. While nutrients are defined as things that nourish, and are therefore often viewed as good things, too much of a good thing is clearly deleterious, just as eating too much food can cause obesity and a host of health problems. Excessive growth of phytoplankton causes the water to become murky, can give off odors, can lead to lost of high-quality bottom habitat such as seagrass beds, and lead to oxygen depletion in the water, with death of fish and other animals. Coastal marine ecosystems vary in their sensitivity to nutrients, and many other factors interact with nutrients to control the growth of phytoplankton, including light, mixing of the water, and grazing various kinds of animals. For many ecosystems, adding more nutrients will increase phytoplankton and plant growth, but the response can be amplified or damped by these other controlling factors.
For coastal marine ecosystems of moderate to high salinity (greater than about 10 parts per thousand of 0/00), nitrogen is generally the nutrient most limiting to production. In contrast, freshwater lakes of moderate to high productivity are generally more phosphorus (P) limited. However, there have been relatively few studies to determine whether nitrogen or phosphorus is more limiting in brackish coastal ecosystems with intermediate salinities in the range of Oyster Pond (2.3 ppm during June-August 2002). In Oyster Pond, two previous studies found that neither N nor P additions affected phytoplankton growth, but both of these experiments were conducted in October, and the pond might react differently during summer months.
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then I learned from him that he had seen quite a large number of dead herring along the beach east of the Trunk River. He showed me the location where he said he had counted seventy or so.
To my amazement the young man was right. Freshly dead herring about 3 inches in length were scattered all along the shore as though they had been washed up by a wave and left there. I estimated in a ten foot strip there were some 25 or more dead herring (Figure 2). I did not survey the beach beyond this one area. Two blackback gulls east of our area were feeding along the shore - perhaps on young herring. I thanked the young man and told him that it was a mystery why the herring had died. |
Later that day with dead herring still on my mind I returned to the Trunk River at 4:45 pm and took a water sample. Herring were still heading for the Sound. Weater temperature was 26 degrees C; salinity was 3 ppt. But hereby hangs a tale. I had been in the habit of tasting the water sample to check saltiness. But with this one my nose said no. It smelled strongly of hydrogen sulfide - the rotten-egg smell. Talking to Bill Kerfoot, longtime board member of OPET, he suggested that the H20 odor might have also meant low oxygen which could have caused the death of the herring - in other words anoxia.
SOMETHING TO THINK ABOUT! November 21, 2002 |
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