Figure 6-24 Long-term trend in summer (July-September) mean, minimum, and maximum DO in the Arthur Kill (RF1-02030104003). Source: USEPA STORET.

now nesting in portions of the harbor core area where they had been absent for decades (primarily because of bioaccumulation of DDT), have rapidly become so numerous as to be considered a nuisance by boaters and fishermen. Ten percent of the East Coast population of the federally endangered peregrine falcon is located in the Hudson-Raritan estuary metropolitan area (HEP, 1996).

Fish-eating bird populations have thrived despite the fact that sluggish circulation and urban runoff and municipal and industrial wasteloads characterize these waterways (HydroQual, 1991). The Arthur Kill waterway is possibly one of the sites of poorest water quality in New York Harbor. Summer mean DO concentrations in the Arthur Kill, ranging from less than 1 mg/L to about 3 mg/L from 1940 to the mid-1970s, however, steadily improved during the 1970s to concentrations above 5 mg/L by the mid-1980s (Figure 6-24) (Keller et al., 1991; O'Shea and Brosnan, 1997). Average summer concentrations of DO at Shooters Island in the Kill Van Kull further reflect this trend of improvements, increasing from 30 percent in 1974 to near 60 percent saturation in 1995 (O'Shea and Brosnan, 1997). Improvements in DO concentrations, as well as habitat protection efforts by the New York City Audubon Society, may have contributed to the success of populations of herons that feed on pollutionintolerant young fish in the Arthur Kill and its associated tidal creeks and wetlands. A 1988-1989 census of wading bird breeding populations indicated approximately 900 to 1,200 pairs of breeding herons, egrets, and ibises that constitute possibly the largest colonial waterbird rookery complex in New York State (Trust for Public Lands, 1990).

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