Water quality gradients and trends in New York Harbor

New York Harbor is a complex of interconnected waterways that have supported the rapid development of a thriving megacity and metropolitan region. The water quality of New York, a partner city in the World Harbour Project, is a reflection of the combined impacts of this metropolitan region. Water quality health and trends were assessed between 1996–2017in 9 different reporting regions using publicly available data. Analyses of New York Harbor water quality reveal strong persistent geographic gradients and long-term trends in improving water quality. Data was synthesized for five indicators throughout the New York harbor region including: total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), chlorophyll a (chla), and water clarity (secchi disk depth). The health of the waterways surrounding New York City was evaluated and graded on a 0%–100% scale and displayed using a ’stoplight color scheme’. The best water quality in the region evaluated was in the area of the most exchange with the Atlantic Ocean in the Lower Bay near the harbor entrance. Conversely, the most degraded water quality was in the areas of lowest water exchange in dead end canals (Newtown Creek and Flushing Bay) and Jamaica Bay. The Hudson River, East River, Upper Bay, Newark Bay, and Raritan Bay had intermediate water quality. High nutrient levels (TN and TP) were observed throughout New York Harbor, but water clarity, DO and chla levels were variable. Overall, there were improving trends in many water quality parameters over the time period of our study, especially TN. Data used in this analysis can be used as a resource for environmental managers, educators and students to explore health of New York Harbor and its associated waterways. This analysis may be seen as a model for other important and threatened harbors and waterways including partner cities in the World Harbour Project by providing a comparable method for assessing and communicating water quality health.