Temporal and spatial variations of water quality in the Newark Bay Estuary

Abstract

Long-term (summer 2015–2018 and short-term (summer 2018) water quality monitoring was performed to understand spatial and temporal variations of surface water quality in the Newark Bay Estuary, as well as the Upper New York Bay, parts of the Hudson-Raritan Estuary in the New York–New Jersey metropolitan area. Electrical conductivity (EC), pH, temperature, and dissolved oxygen (DO) were measured in the field, while dissolved nitrate, phosphate, and ammonia concentrations were determined in the laboratory. Long-term and short-term water quality monitoring data consistently indicated that nutrients are significantly elevated in the Hackensack River most likely due to sewage effluent from a major sewage treatment plant. Dissolved oxygen levels were sufficiently high in most parts of the estuaries, whereas the Hackensack River showed a sign of hypoxia. Nutrients in the estuaries showed significant temporal variations typically by 2 to 3-fold during the 1-month short-term monitoring period, and were correlated with EC, DO or pH. The effects of combined sewer overflows (CSOs) during wet weather on the water quality of Newark Bay appeared uncertain except for ammonia, but long-term effects of CSOs need to be further investigated because nutrients from CSOs can accumulate in bottom sediments and be remobilized. Frequent water quality monitoring is necessary to better understand the impact of human activities on temporal variations of nutrients in urban estuaries and to efficiently protect coastal ecosystems.