1996 Citizens Report: Quissett Harbor, Falmouth
Embayment: Quissett Harbor
Embayment and Watershed Characteristic
Quissett Harbor has the smallest drainage basin of all those embayments studied. A golf course together with the residential land account for most of the land within the basin, and the watershed is among the least forested, and the basin has a modest buildout capacity. Individual parcels are large so the total number of housing units in this small watershed is low, and this together with a low yearly average occupancy rate minimizes septic loadings. Fertilizer loadings from golf course were estimated to account for a third of the embayment loadings. Shellfish resources are fair and eelgrass covers less than a third of the bay.
Water Quality monitoring
Due to lack of volunteers and accessibility, oxygen concentrations were not monitored in outer Quissett, but were monitored in the inner portion of the embayment. These inner embayment oxygen concentrations were high compared to most embayments, but the outer embayment values would probably have been even higher than shown, which were among the best sites monitored. The inner embayment oxygen values were used to calculate outer embayment eutrophication Index scores (see centerfold map), therefore the outer embayment Eutrophication Index scores represent a worst case condition (oxygen represents 25% of the Eutrophication Score).The Eutrophication Index showed a dip to only fair water quality in 1994 in the inner harbor.
This decline was due to considerably elevated levels of dissolved organic nitrogen together with
lesser increases in particulate nitrogen and phytoplankton pigments. We do not have an
explanation for the cause of these changes. Interestingly total nitrogen in the outer harbor was
consistently low, typical of offshore Buzzards Bay waters. For example, in 1993, mean total
nitrogen concentration near the mouth of the embayment were only 0.21 ppm, whereas
concentrations in the inner embayment were still a modest 0.39 ppm. In 1994, however, total
nitrogen concentrations at the inner bay station skyrocketed to 0.63 ppm. It is worth noting that
only one station (monitored 4 times a summer for nutrients) is used as the bases for the
Eutrophication Index, and the wide fluctuation on summertime averages of some parameters may
reflect this small "sample size".
Eutrophication Index scores
Nitrogen Management needs
The Buzzards Bay NEP estimated that residential land accounts for slightly less than 40% of the nitrogen inputs to the Bay, followed closely by fertilizer use on the golf course. Quisett Harbor is among the deeper, better flushed embayments in Buzzards Bay. Consequently it has a relatively high loading limit, even with an "Outstanding Resource Water" designation (ORW- the most stringent coastal water quality designation). Because existing loading is only 4% of recommended limits, and will be only 7% of recommended loading in the future, nitrogen management action is not recommended for this watershed, but it may be worthwhile to determine if there are opportunities for improving fertilizing practices on the golf course.Back