1996 Citizens Report: Nasketucket Bay, Little Bay, Fairhaven
Embayment: Nasketucket Bay, Little Bay
Embayment and Watershed Characteristic
Nasketucket Bay is among the largest of Buzzards Bay embayments monitored. It has the third greatest amount of salt marsh of any Buzzards Bay embayment and eelgrass habitat is widespread throughout except in the uppermost portion of the Bay, known as Little Bay. There is little residential development in the Little Bay watershed, whereas the greater Nasketucket Bay watershed has far more residential land use, especially along Sconticut Neck. More than a quarter of the watershed is under some type of agricultural use, the third highest in Buzzards Bay, which dominates nitrogen loading to the bay. The abundance of lands in agricultural and residential use, have left only 38% of the watershed in forest, which puts Nasketucket Bay among the lowest third in this category.Little Bay is a rainfall conditional closure site due to elevated fecal coliform loading from rain runoff. There are good shellfish resources in this area and the town of Fairhaven and Massachusetts Division of Marine Fisheries have identified priority stormwater discharge sites on Sconticut Neck and Little Bay for remediation.
Water Quality monitoring
A large fraction of nitrogen loading to Nasketucket Bay arrives through Little Bay, and most of the nitrogen to Little Bay arrives via the Nasketucket River. That loading, plus the poorer flushing in Little Bay, result in poorer water quality there. River stations NR1, NR2 (Rt. 6, not shown), and NR3 (railroad bed, not shown) were monitored for nitrogen on 4 dates in 1993 (the only year that nitrogen was measured here). Station NR1 closest to the bay, had salinities ranging from 21-29 ppt, NR3, next upstream, had salinities between 4 and 12 ppt, and station NR2, most upstream, had salinities below 2 ppt. What is most interesting about the results of this survey was that there was a large spike of inorganic nitrogen midstream at station NR3, suggesting a large nitrogen source down gradient of Route 6. Concentrations of dissolved inorganic nitrogen concentrations approached a remarkably high 100 micromolar (=1.4 ppm)-- a value very high for a Buzzards Bay stream.Eutrophication Index scores
Eutrophication Index scores in Little Bay for 1993 to 1995 were 42, 43, and 59 respectively, only fair scores. The apparent improvements in water quality were largely driven by a big reduction in inorganic nitrogen levels in 1995 together with improvements in the amount of chlorophyll and organic nitrogen in the water. Some possible explanations for this decline in inorganic nitrogen was that a large corn field in the watershed was converted to a soccer field and park in the Spring of 1994, the Weeden Road area (just a few hundred feet from the bay) was sewered in the Fall of 1993, and a nursery along the Nasketucket River changed its management practices somewhat. We presume that the soccer field received considerably less or no fertilizer applications, and that there was a sizable dropoff in overland runoff of inorganic nitrogen from all these sources..
Oxygen concentrations were monitored in all four years. While both sites LT1 and LT2 were monitored in 1994 and 1995, only site LT1 was monitored in 1992, and only site LT2 was monitored in 1993. However because oxygen saturation values were very similar at both sites both in 1994 and 1995, we do not believe the use the 1992 or 1993 to be problematic. In general, oxygen concentrations were typically above 80% saturation at both sites, but in 1992, most oxygen saturation values were below 70%, with one observation at 33%. This suggests water quality in that estuary may have been worse in that year. The results from station NR1 were quite different with the average of the lowest 1/3 saturation values hovering around only 45% saturation.
As might be expected the outer bay station at West Island (WI1) had better water quality, with very high oxygen saturation values, but in the two years of nutrient monitoring (1994 and 1995), other measures of water quality were not as good at WI1, and this station had a eutrophication Index Score of only 59 points, suggesting only fair water quality.
Nitrogen Management needs
In 1994, the Buzzards Bay NEP estimated that farm animals account for 46% of the nitrogen load to the upper reaches of Nasketucket Bay (including Sconticut Neck), and other cropland and nurseries account for an additional 16%. Residential inputs account for only 20% of inputs. These estimates for farm animals were based on 1500 animal units, (which equals 1000 dairy cows). Even with these loads, the Project estimated that existing nitrogen loading to Nasketucket Bay as a whole was well below recommended limits. However, because of apparent eutrophic conditions in Little Bay, the Project recommended a separate nitrogen management strategy for the Little Bay subwatershed area (which is more dominated by agricultural inputs). Last year, the Town of Fairhaven gathered the necessary land use data for the development of a management strategy for Little Bay, and this summer the Buzzards Bay NEP is funding a flushing study to establish nitrogen loading limits for Little Bay. The results of these two initiatives will enable the town to develop a comprehensive nitrogen management strategy for Little Bay. The Nasketucket River should also be resampled in 1996 to better identify nitrogen sources and determine whether a decline in nitrogen concentrations has occurred.Back