Photos of the Long Island Sound

Research & Monitoring

2004 Research Project Descriptions

A Biological-Physical Numerical Simulation Model for the Investigation, Prediction and Management of Oxygen Production and Consumption in Long Island Sound: Data analysis and model formulation

Dr. Nicole Goebel and Dr. James Kremer, University of Connecticut
Dr. Chris Edwards, University of California at Santa Cruz

The objective of this project was to develop a simple and accurate ecosystem model of oxygen dynamics in Long Island Sound. Unlike other models, the primary productivity component of this model was corroborated with site-specific measurements of oxygen production and consumption. The focus of these rate measurements on processes directly driving oxygen changes are especially suited to the simulation of the relationship among nitrogen loading, eutrophication, and hypoxia. Rates of primary production are fundamental to predictions of phytoplankton stocks, and primary production and phytoplankton stocks are directly related to predications of oxygen production and consumption. This model will help improve understanding of the processes that contribute to hypoxia in Long Island Sound. The results of this study suggest that simplifying the model to four state variables—nitrogen, phytoplankton, benthic organic matter and oxygen—can accurately describe primary productivity in LIS as well as similar ecosystems. However, the model does not perform as well in describing oxygen consumption in the LIS water column. On average, oxygen consumption measured in LIS was 2-10 times that predicted in the model. Further investigation on the balance between oxygen consumption and production suggests an additional carbon source or oxygen sink in LIS. Incorporation of these missing sources and/or sinks into the biophysical–physical LIS model could lead to a simple, accurate, and practical model for managing hypoxia in LIS.
Final Report Summary
Final Report

Published paper: Goebel, N.L., and J.N. Kremer. 2007. Temporal and spatial variability of photosynthetic parameters and community respiration in Long Island Sound. Marine Ecology Progress Series. Vol. 329 (Jan. 2007): 23-42.

Natural Isotopic Tracers for Anthropogenic Nitrogen in Long Island Sound

Dr. Mark Altabet, University of Massachusetts
Dr. Johan Varekamp, Wesleyan University

The objective of this project is to quantify the impact of anthropogenic nitrogen loading to Long Island Sound with respect to natural sources. Innovative geochemical tools called isotopic tracers will be used to characterize the nitrogen sources to the Sound. This approach permits the assessment of the actual contribution of anthropogenic nitrogen to Long Island Sound’s nitrogen inventory. These results will help improve our understanding of the relationship between anthropogenic nitrogen loading and eutrophication.
Final Report Summary
Final Report

Food Webs in Long Island Sound: Review, Synthesis and Potential Applications

Dr. Roman Zajac, University of New Haven
Mr. Dave Simpson, CT Department of Energy and Environmental Protection

The objective of this project is to develop conceptual and quantitative food web models for different habitats in Long Island Sound. Using these models, the researchers will assess the critical food web components in each habitat type and identify data gaps in the present understanding of major food web components and their potential interactions. These models can be used to develop simulations and analyses to evaluate the impacts of management decisions on food webs and ecosystem dynamics in Long Island Sound.
Final Report Summary
Final Report

Application of Remote Sensing Technologies for the Delineation and Assessment of Coastal Marshes and their Constituent Species Set

Dr. Daniel Civco, University of Connecticut
Dr. Martha Gilmore, Wesleyan University

The objective of this project is to identify and delineate coastal marshes around Long Island Sound and distinguish various types of marsh vegetation using moderate and high resolution remote sensing satellite imagery coupled with in situ radiometry and other field data collection. The researchers will identify and inventory the current extent and condition of the Sound’s coastal marshes and develop a cost-effective way to track changes in the condition of wetlands over time. These datasets and protocols can help provide coastal resource managers, municipal officials and researchers with baseline information for current land management and for long-term monitoring of habitat changes.
Final Report Summary
Final Report

Published Paper: Martha S. Gilmore, Emily H. Wilson, Nels Barrett, Daniel L. Civco, Sandy Prisloe, James D. Hurd, and Cary Chadwick. Integrating multi-temporal spectral and structural information to map wetland vegetation in a lower Connecticut River tidal marsh. Remote Sensing of Environment 112 (2008): 4048–4060

Understanding the Role of Nutrient Enrichment in Tidal Marsh Loss in Long Island Sound

Investigator: Dr. Shimon Anisfeld, Yale University

The objective of this project is to test the hypothesis that excessive loading of nutrients (nitrogen or phosphorus) plays a role in causing tidal marsh loss. Tidal marsh loss due to drowning (i.e., loss of elevation relative to sea level and conversion of vegetated marsh to mudflat) has been observed in recent years in Long Island Sound, primarily in the western Sound. However, the mechanisms and causes of this marsh loss are poorly understood. The results of this research will help ascertain if nutrient loading is a factor in tidal marsh loss and, if so, identify which nutrient is likely responsible.
Final Report Summary
Final Report

Published papers:

  • Shimon Anisfeld and Troy D. Hill. Fertilization effects on elevation change and below-ground carbon balance in a Long Island Sound tidal marsh.Estuaries and Coasts. (2012): 35:201-211.
  • Shimon Anisfeld,Troy D. Hill, and Donald R. Cahoon. Elevation dynamics in a restore versus a submerging salt marsh in Long Island Sound. Estuarine, Coastal and Shelf Science. Volume 170. (5 March 2016): 145-154.

Temporal and Spatial Changes in Copper Speciation and Toxic Metal Concentrations in Long Island Sound: Effect of changes in water temperature and dissolved oxygen levels

Investigator: Dr. Sergio Sañudo-Wilhelmy, Stony Brook University

The objective of this project is to establish the chemical speciation and vertical profiles of dissolved and particulate toxic metals in the water column in Long Island Sound. Dissolved metals undergo many changes in the estuarine environment, and this research will provide valuable information regarding the temporal and spatial variations in the chemical speciation of dissolved copper in the Sound. This research will also provide resource managers with critical information regarding the distribution of toxic metals both in the water column and throughout Long Island Sound. These factors are important for evaluating the health of Long Island Sound and examining the bioavailability of metals in the water column. This research also may support future ecotoxicology studies in the Sound.
Final Report Summary
Final Report

Assessment of the Effects of Bottom Water Temperature and Chemical Conditions, Sediment Temperature, and Sedimentary Organic Matter (Type and Amount) on Release of Sulfide and Ammonia from Sediments in Long Island Sound: A laboratory study

Dr. Carmela Cuomo, University of New Haven
Dr. Paul Bartholomew, Superb Technical

The objective of this project is to collect data on the release of sulfide and ammonia from sediments exposed to an array of environmental conditions. The researchers will conduct a series of laboratory experiments in which sediment collected from western Long Island Sound will be exposed to conditions that are representative of the spring, summer and fall. Previous studies have demonstrated that exposure to hydrogen sulfide and ammonia, in the presence of elevated water temperatures, can cause significant weakness and mortality in lobsters. This research will examine the fluxes of ammonia and sulfide from the sediments and any associated changes in bottom water dissolved oxygen levels, relative to certain environmental variables. These data will aid in the understanding of the development and abatement of seasonal hypoxic conditions in the western Sound and the role that sediment organic matter and sediment oxygen demand play in such events.
Final Report Summary

Nitrogen attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches

Thor E. Smith, US Geological Survey
Andrew E. Laursen, Ryerson University
Jeffrey R. Deacon, US Geological Survey

The Connecticut River is a significant source of nitrogen to Long Island Sound, where high nitrogen loads cause seasonal hypoxia. To respond to this problem with effective strategies for reducing nitrogen loads in the Connecticut River, it is important to determine the rate and location of nitrogen loss during downstream transport to the Sound. Recent research has investigated the sources and transport of nitrogen in the Connecticut River basin, but the extent to which nitrogen is lost during transport remains unclear. The objective of this study, therefore, was to assess the degree and variability of nitrogen attenuation in the Connecticut River by making measurements in two reaches of the river during two different seasonal flow regimes (spring and summer). In this study, the methods of mass balance and N2 measurements were used independently to estimate the rates of in-stream nitrogen loss. A mass balance on nitrogen inputs and output for two study reaches (55 km southern reach and 66 km northern reach) at spring high flow (April 2005) and at summer low flow (August 2005) was computed on the basis of total nitrogen concentrations and measured river discharges in the Connecticut River and its tributaries. In a 10.3 km subreach of the northern reach, concentrations of dissolved N2 were also measured during summer low flow and compared to modeled N2 concentrations to determine the measured “excess” N2 that indicates denitrification. Mass balance results showed no in-stream nitrogen loss in either reach during April, and no nitrogen loss in the southern reach during August. In the northern reach during August, however, nitrogen output was 18% less than the total nitrogen inputs to the reach. N2 sampling results gave an estimated rate of N2 production that would remove 3.3% of the nitrogen load in the river over the 10.3 km northern subreach. The nitrogen losses measured in the northern reach in August may represent an approximate upper limit for nitrogen attenuation in the Connecticut River because denitrification processes are most active during warm summer temperatures and because the study was performed during the annual low-flow period when total nitrogen loads are small.

Published paper: T. E. Smith, A.E. Laursen, and J.R. Deacon. Nitrogen attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches. (2008):  Biogeochemistry, v. 87, no. 3, p. 311-323

This investigation is funded through the EPA’s Regional Applied Research Effort (RARE) program.

Long Island Sound Ferry Monitoring

Investigator: Daniel L. Codiga, Graduate School of Oceanography, University of Rhode Island

The objective was to monitor eastern Long Island Sound water quality by collecting oceanographic measurements from a ferry that transits between New London, CT and Orient Point, NY eight times daily. Measured quantities include water velocity profiles and near-surface water properties (temperature, salinity and chlorophyll fluorescence. Other objectives include: creating gridded data projects (GDPs) that are suitable for convenient use by modelers to calibrate, validate, and constrain outputs of water quality models and underlying hydrodynamic models; exploiting the unique sampling characteristics of the velocity measurements to separate the tidal and non-tidal components of the circulation; using the water property measurements to characterize the spatial and temporal variations in near-surface temperatures, salinity, and chlorophyll fluorescence; and maintain a public display in the passenger area of the ferry, includjng presentation of real-time data and explanatory posters to raise awareness and appreciation for LIS and scientific issues underlying its water quality management.
Final Report SummaryFinal Report

Published paper: Daniel Codiga and Dirk A Aurin. 31 October 2006., Residual circulation in eastern Long Island Sound: Observed transverse-vertical structure and exchange transport, Continental Shelf Digest (available on-line at 27 (2007): 103–116

This investigation was funded through the Long Island Sound Study enhanced monitoring funds.

Gridded Data Products (GDPs) are available at

Ferry Based Marine and Atmospheric Observing System

Investigator: Robert E. Wilson, Marine Sciences Research Center, School of Marine and Atmospheric Sciences, Stony Brook University

The primary goals of this project were the development of a ferry-based observing system for LIS and the maintenance of a year-round sampling program along a transect in the central Sound. The main observations considered here include surface meteorology and water column current structure. There are two components of this observation system: the data acquisition system and the data handling system. Secondary project goals included: 1) obtaining refined estimates for LIS basin-wide seasonal cycle budgets of heat, mass and salt, 2) development of a multi-decade retrospective time series of LIS surface fluxes that could provide a framework for interpreting modern ferry observations, and 3) obtaining a description of the variability in estuarine exchange flow entering the central Sound.
Final Report Summary
Final Report

Data retrieval and descriptions of instruments are provided on the project website:

Published paper: R. E, Wilson, R.L. Swanson, and H.A. Crowley. Perspectives on long-term variations in hypoxic conditions in Western Long Island Sound, Journal of Geophysical Research, (2008)

This investigation was funded through Long Island Sound Study enhanced monitoring funds.

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