Delivered at 2003 Boston Harbor Islands Science Symposium
The waters of Boston Harbor surround most of the islands of the Boston Harbor Island national park area. Water quality in the Harbor has shown improvements since wastewater discharges to the Harbor were ended in September 2000. The purpose of this paper is to present some of these improvements.
One of the largest improvements has been a decrease in concentrations of nitrogen (N) and phosphorus (P) in the Harbor water-column; N and P are the two nutrients most responsible for “eutrophication” (or over-enrichment) of coastal aquatic systems. Average concentrations of N and P have decreased by about one-half, and over most of the Harbor area.
The Harbor has also shown a decrease in quantities of suspended microscopic algae (or phytoplankton). Quantities of phytoplankton (measured as concentrations of chlorophyll) have decreased by about one-third. The decrease has been observed mainly in summer, and in the North Harbor.
The Harbor has also shown an increase in water clarity. Clarity averaged over the Harbor as a whole has increased by about one-tenth. The increase has been greatest during summer, and in the North Harbor.
We have also seen a small but statistically significant increase in bottom-water dissolved oxygen (DO). DO has also increased by about one-tenth for the Harbor as a whole, again mainly in the North Harbor.