[During September and October 1997 a rapid sequence of email messages flowed among people on the massbird list. It all started out with an innocent question by Jim Barton asking whether anyone knew of any concentrations of Greater Scaup in the larger Massachusetts Bay region, since he knew that the numbers had quite disappeared in Boston Harbor. Soon the discussion turned to the question of when the scaup had disappeared, why, and where they were now.
Several people suggested that a cleaner harbor, due to the construction of MWRA's new secondary sewage treatment plant at Deer Island, was perhaps responsible for lower numbers of scaup, whereas others immediately protested that such a clean-up could only result in more birds, not less. There were also discussions of water clarity and salinity as affected by the activities at Deer Island. I passed most of the correspondence on to Maury Hall, and disseminated his response via massbird. Here is a reprint of Maury's response.]
TASL data clearly indicate a substantial decrease since 1980. In my conversations with Dr. John S. Barclay (University of Connecticut at Storrs) he noted a virtual collapse of Greater Scaup in Connecticut. Anecdotal reports from Narrangansett Bay also indicate sharp drops. Barclay has found very high concentrations of contaminants (metals and organics) in their tissue. He believes they may be more sensitive than other waterfowl species to these chemicals and as a result have suffered reduced reproduction. His research is ongoing. (See Scaupnet)
The last time I talked with Barclay he noted that there was another potential threat. Over the past several years, Zebra Mussels have taken over the Great Lakes and provide an abundant food source for the scaup. As a result, scaup tend to linger longer into the fall/winter than they once did. While there, they are being hunted very heavily by the Canadians who have much more relaxed bag limits than hunters in the US. I would like to verify this.
A third potential cause for reduced numbers in the harbor may be the Blizzard of '78. There is anecdotal information from lobstermen that the sediments in outer Quincy Bay were changed dramatically as a result of the storm. Mussel beds were supposedly buried under inches of silt and fine sand. Historically, there had been huge concentrations of eider, scaup and scoter in those waters, but they disappeared in the late '70s. No mussels: no birds. A similar phenomena may have occurred after the Halloween storm of '91. TASL data shows that from 1980 to 1991 most of the eider in the harbor were found off Deer Island. Now they are found throughout the southern harbor, wherever there are mussel beds. The Halloween storm had the highest storm surge of any event since the Blizzard of '78 and MWRA data shows it impacted tremendously the sediments and bottom fauna in the harbor. I can only assume that mussel beds off Deer Island were buried or torn up. Again, fewer mussels: fewer birds. In any case, the decrease in scaup numbers is at least regional. Changes in Boston Harbor alone aren't likely to bring them back in the numbers once observed.
Very little good historical data exists about bird concentra tions in the harbor. The 17-year TASL database is by far the best. The harbor clean-up has received so much publicity that people assumed there was no life in the harbor prior to the clean-up and when they saw anything they assumed it must be a result of the clean-up. Seals, porpoises, starfish, cormorants, jellyfish, striped bass and mergansers have been reported as indicating improvement in the harbor. Unfortunately for such reports, all were in the harbor throughout the last several decades and in some cases in higher abundances.
Seals have increased along the coast since the late '70s when an epidemic killed off a high percentage of the animals. Passage of the Marine Mammal protection Act in the '70s provided further protection. TASL data indicates that the peak seal concentrations in the harbor were in 1987-'89 when 50 seals were being observed at haul-out sites in the Quincy area in the wake of the Nut Island wastewater discharge. I believe there are currently 50 or so seals that can be found at haul-out sites at the outer harbor islands. These are the seals we see routinely in the embayments and inner harbor. If they are the same wintering population as were observed in Quincy, it would be interesting to know why they moved farther east. Disturbance? Shooting by fisherman? More food?
Porpoises Not much is known about porpoises, especially in Boston Harbor. In the late seventies a friend who fished off Hull routinely reported small pods in the outer harbor in the spring. The first indication they moved into the harbor in any numbers was in 1992, when they would come into the inner harbor to feed on the fish stunned by the blasting for the third harbor tunnel. In the spring of 1995 large numbers ( as high as 40) were seen off the Coast Guard station in the North End. Coincidentally, 1995 was a very good year for river herring moving into the Charles River. Cormorants were abundant at the same location. 1996 and 1997 were so-so years for the herring and fewer cormorants and fewer porpoises (maxima of 2 and 4, respectively) were seen on my daily censuses.
Water clarity in the harbor appears to be determined mainly by resuspended sediment particles and phytoplankton (algae) concentrations. Unfortunately, the data base does not allow for good comparisons before and after the cessation of sludge discharge. We know that the Nut Island sludge discharge at the tip of Long Island was visible from boats in the area and it is now gone. The Deer Island sludge could really never be distinguished from the effluent solids with which it was discharged (75% of the particles were effluent). The sludge was heavier and appears to have dropped relatively quickly to the sediments whereas the effluent solids were lighter and stayed in suspension longer. To see improved water clarity away from the immediate vicinity of the discharge is unlikely. Since sludge really never got into the inner harbor except by sediment creeping , improvements in water quality in the inner harbor due to the cessation of sludge discharge is really reaching for an effect that I don't believe is there.
Actually water clarity during the summer of 1997, as measured by MWRA's routine harbor-wide surveys, was well below the average of the previous three years. Dry, sunny weather appears to increase algae growth and decrease clarity.
Improvements in the health of winter flounder (i.e., reductions in liver tumors) began with fish spawned in the mid 1980s (1983-1986). Presumably, this was due to the banning of pesticides (DDT and chlordane) and PCBs. More recent reductions in the incidence of liver disease in flounder collected off Deer Island may be linked to the sludge cessation. However, the fish collected for these studies have been younger than pre-1991 fish. Younger fish have had less exposure to contaminants, and therefore are usually less diseased. We can't be absolutely sure these improvements are due to the cessation of sludge discharge.
What we do know is the catch per unit of effort in a ten-year study of flounder off Deer Island has decreased dramatically since sludge discharge stopped. To some degree this follows the general decline of flounder throughout the region due to overfishing. However, we collect flounder from Broad Sound, Massachusetts Bay, Nantasket and Cape Cod Bay and have no problem getting the 50 fish we need. At Deer Island we trawl for 2 hours and get only 20 to 30 fish. In the late '80s you could easily get 100 fish in an hour.
We know that mud worms ate the sludge. After spawning in April, flounder eat voraciously for weeks (they do not eat while spawning). In April and May the flounder pigged out on the worms. Now there are no mud worms and flounder stomachs are found to be mainly empty or partially filled with colonial hydroids which have only half the calories of the worm. A similar phenomena occurred at the New York Bight when sludge ceased to be dumped there. As much as we don't like to admit it, the sewage we discharge has provided a food source for many of the animals we associate with a healthy harbor.
One reason why the waters of Boston Harbor were never as polluted as people thought (the sediments were and are a mess) and were able to support an abundant and highly diverse fauna was the rapid flushing of the harbor. The tidal currents off Deer Island are supposedly second only to the currents around Provincetown in their flushing capacity. Fresh water is rapidly mixed with ocean water and flushed out of the harbor, with many of the pollutants in tow. Salinity differences between Massachusetts Bay and the harbor are quite small. Relocation of the discharge should have no impact on the salinity of the offshore waters. The slightly higher salinity in the harbor after relocation should have no impact on where waterfowl are found. Changes in food availability will.
The key to marine food chains is phytoplankton production. The Deer and Nut Island effluents provide an abundant food source for the plankton in the form of ammonia (the by-product of human wastes). Removing this rich source of food may reduce phytoplankton concentrations and in turn reduce the harbor's carrying capacity for fish and birds. MWRA staff scientists continue to collect information to help us understand whatever happens.
Maury Hall
Maury is co-organizer and data-compiler for the TASL winter censuses. He is employed by the Massachusetts Water Resources Authority (MWRA) as staff biologist.
last updated: 11/2/1997
url: http://www.gis.net/~szendeh/tworms.htm