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Boston Harbor
by Molly Friedensohn and Evan McNamara
History
Boston Harbor and the Islands were formed hundreds of years ago out of stones and boulders left over from glacial till. There are over thirty Islands in the Boston harbor, some only visible at the lowest of tides, others as large as 200 acres. For 25 years now the islands have been part of the State Park known as the Boston Harbor National Recreation Area. The areas are both public and private with popular tourist islands including Block Island, George's Island, and Thompson's Island.
In the early 1970s and 1980s Massachusetts sewage was dumped directly into the Boston Harbor causing an environmental disaster. Several species of fish, plants and animals were dying due to the overwhelming amount of pollution in the water. It came to a point where swimming in the harbor was considered dangerous and prohibited.
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Boston has made great progress and with a $4 billion dollar cleanup of the harbor. Massachusetts is working to bring the water back up to the highest of standards. The health of the harbor is tracked by measuring bacteria, algae, and water clarity. Other tests involving dissolved oxygen, water temperature, nutrients, sunlight and salinity help us get a good idea of the cleanliness of our harbor's waters. There are also several studies a year on the toxic contamination of fish and shellfish along with the health of the animal communities that live on the bottom of the Harbor in order to track the condition of the wildlife in our area.
The MWRA, a group, which assesses the water quality of the Boston Harbor, has found the quality to be quite good in recent years. Water clarity has been excellent along with extremely low bacteria counts. Oxygen levels are high, ranging from 8.8 milligram per liter to 9.7 milligram per liter (state standard of 5 milligrams per liter). The wildlife is also coming back with more fishes in the harbor and higher spawning rates in the local areas. Although some of the pollution's destruction may be irreversible, the Boston Harbor is well on its way back to having a healthy and lively marine life.
Boston Harbor Boat Trip
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We set off from Marina Bay in Quincy with a brief trip ahead of us to the outer Boston Harbor Islands. As we traveled past Thompson Island and the newly landscaped Spectacle Island, with Deer Island directly to the North, we headed due East to Calf Island and Middle Brewster Island. We moved slowly between Calf and Little Calf Islands and found a calm patch of water in front of the Brewsters with almost 60' beneath our bow. We were approximately at 42-20 Lat.N. and 70-53 Long.W. The Herring and Black Back Gulls were everywhere and we could see the luminescence of the colorful ctenophores floating at the surface even in the bright sun.
We used the depth finder on the boat to help us monitor the bottom depth and we prepared our lines and cords of our testing equipment to accommodate good interval ranges.
- While heading to one of the testing sites the group began a plankton tow along the surface of the water. Using 3 nets with various mesh sizes, we intended to get a good size range of the microscopic life in the upper reaches of the water column. As we rinsed the nets after a few minutes of towing at 2-3 knots and collected the samples,
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we could see the containers buzzing with activity. Along with the macroscopic moon jellies, we were sure to find plenty of copepods, crab larvae, and other invertebrate larvae. As it was getting late in the fall, we found only very few barnacle and mollusk larvae. The holoplanktonic copepods were still plentiful, and some nearly 2 mm long.
- We proceeded to use our TI calculators and our Vernier LabPros to carry out some of the basics of water sampling testing. We wanted to get a vertical profile of the water column and we used the temperature probe to record the temperature at 1 meter intervals. We found there to be little difference in the temperatures, all within the 13-14 degree Celsius temperature range from top to bottom. The relatively shallow depth, 10' tidal range, and the lack of a thermocline in this well-mixed environment all hinted at our results.
-Our third task involved a Lamotte water sampler to obtain water samples at various depths. We collected samples primarily from the surface, 8m, and 16 meters. We used the LabPro and dissolved oxygen probe to measure the DO on site, we measured the pH, and recorded again the temperature with the probe. We also brought back fixed samples, with Hach powder pillows, to practice and check the DO levels with basic titration methods. Our intention was to also take each sample and run a chlorophyll analysis back at the lab.
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- We measured the salinity for each of the samples using both a plastic Aquarium gauge and a refractometer. Again we saw consistent results throughout the water column as we found the salinity hovering close to 32 ppt.
We also demonstrated the use of the Secchi disc to test the clarity of the water. We carefully lowered the black and white disk and continued to let it descend until we were unable to see it. Once it was out of our range of vision, we raised it until we could once again see it at depth and we recorded the depth with the marked intervals on the sounding line.
