The East River tidal strait, New York City, New York, a high-nutrient, low-chlorophyll coastal system

Yaqin Li,Mark S Dixon,Gary H Wikfors,Shannon L Meseck

doi:10.1007/s40071-018-0189-2

Abstract

The East River tidal strait, located between New York Harbor and Western Long Island Sound, is characterized by high suspended silt concentrations with low organic content kept in suspension by intense tidal currents. Inorganic nutrients, including nitrate, nitrite, ammonia, and phosphate, were high even during the summer. Dissolved inorganic nitrogen (DIN) concentrations generally were above 20 µM and did not likely limit phytoplankton growth. Despite high nutrient concentrations, median chlorophyll a concentration was only 1.53 µg l−1, making the East River tidal strait a high-nutrient, low-chlorophyll (HNLC) area, likely a result of suspended silt blocking light penetration into the surface water. There were times at which the ratio of mixed layer to depth of the euphotic zone was generally greater than what has been suggested for phytoplankton to produce net primary production. The high-nutrient East River tidal strait is likely one of the sources of nutrients fueling summer phytoplankton production and consequent hypoxia in the Western Long Island Sound as silt settles from surface water in the lower turbulence conditions of the western narrows of Long Island Sound, thereby allowing light penetration and subsequent consumption of dissolved nutrients by phytoplankton.

Highlights

The East River tidal strait is a water body with a length of about 25 km connecting New York Harbor to the east to Western Long Island Sound to the west (Fig. 1); it is not a true river
Our results suggest that phytoplankton were at times not able to achieve net primary production despite high nutrient availability because of low light penetration
The highly turbid condition was attributable to inorganic matter, as the chlorophyll level at the site was fairly low with a median value of 1.53 lg l-1

Summary

Introduction

The East River tidal strait (referred to as the ‘East River’ in some references and maps) is a water body with a length of about 25 km connecting New York Harbor to the east to Western Long Island Sound to the west (Fig. 1); it is not a true river. The East River tidal strait is divided into upper and lower sections by the Hell Gate sill where the tidal flow is restricted through a narrow passage (Marmer 1935). The upper East River tidal strait, from the Hell Gate to Willets Point near Western Long Island Sound, * 13.5 km in length, is shallower and wider than Hell Gate. The lower East River tidal strait, * 12 km, from Hell Gate to the Battery.

Methods

Results

Conclusion