A Connecticut Department of Energy & Environmental Protection and University of Connecticut Partnership
Long Island Sound Sentinel Monitoring for Climate Change Program

Long Island Sound Sentinels


I. Definition of ‘Sentinel’

A Long Island Sound climate change sentinel is a measurable variable (whether an abiotic factor, a system, process, or species) in the Long Island Sound estuarine or coastal ecosystems that is likely to be affected by climate change and that can be monitored.

II. Ideal Attributes

The indicators that will be the most effective sentinels of climate change ideally will possess all of the following attributes:

  • They can be measured at multiple sites, so that comparison between sites can be made;
  • The climate change signal for the indicator can be distinguished from natural variations or anthropogenic stressors with the appropriate sampling resolution;
  • For biological indicators, they are:
    • representative of regional biological communities, processes, ecosystems and/or
    • a species at the edge of its range (fringe) or in a habitat that is limited
  • They have an existing or potential data record that would allow comparison of historic, current, and future conditions
  • They can be measured and studied feasibly with respect to cost and available technology (or new technology can be developed in order to support their measurement).

The term “indicator” as used here is consistent with EPA’s Climate Ready Estuaries program (see Appendix A for a Glossary of Terms and List of Abbreviations).

III. Approved Sentinels for Long Island Sound

The following table is the list of approved sentinels and associated indicators that are or can be measured in an attempt to detect change brought about by climate change. The database contains information about data related to this specific list of sentinels.



Water Quality & Quantity

Hypoxia in LIS and embayments

  • Dissolved oxygen
  • Duration of hypoxia
  • Area affected and severity
  • Wind speed and direction

Changes in groundwater quality and quantity

  • Salinity
  • Groundwater elevation
  • Water temperature

Human pathogens

  • Abundance of specific pathogen (i.e., enterococci)

Shellfish bed (commercial/recreational) closures (human/economic impacts)

  • #bed closures
  • Duration of closures/year


  • pH
  • Thickness of crustacean shells = some species develop thinner shells (oysters, clams, mussels), others develop thicker shells (crabs, shrimp, lobster)

Turbidity of water column (abiotic reduction of light penetration)

  • Turbidity (not secchi)
  • Sediment accumulation rates

Harmful algae blooms (HAB)

  • Cell counts (with species ID); algal toxins
  • Blue mussels quickly accumulate HAB cells and are deployed in cages for two weeks

Pelagic/Benthic Systems and Associated Species

Distribution and abundance of aquatic invasive species or new occurrences, particularly from a shellfish production and natural resources perspective

  • Invasive species – distribution and abundance

Composition, abundance of benthic (shallow and deep) fauna

  • LIS benthic index (under development by Robert Whitlach @ UConn)
  • REMOTS benthic camera

Phytoplankton species composition and abundance

  • Chlorophyll a
  • Nutrients
  • HPLC and microscopy & species identification analysis
  • Biogenic silica (POM)

Zooplankton species composition and abundance

  • Annual biomass
  • Species composition
  • Species identification analysis

Finfish (distribution and abundance)

  • Trend analyses (similarity coefficient regression) of survey catch data
  • Correlation of adaptation group abundance and individual species

Benthic macroalgae

  • Species specific studies

Hard substrate subtidal communities

  • Distribution and abundance of shallow water suspension feeders; macroalgae; foraminifera

Fisheries of Long Island Sound and Associated River Systems


  • Lobster larval abundance from fisheries independent monitoring; Catch per unit effort
  • Indices from fishery monitoring
  • Neoparamoeba distribution in water column;
  • Temperature effects – analysis of catch distribution in LIS Trawl Survey and LIS commercial catch.  Assay to measure heat shock protein

All shellfish (clams, mussels, oysters, scallops)

  • pH
  • Alkalinity
  • CO2 concentrations

Eastern Oysters (shellfish): changes in populations due to Dermo or MSX; ocean acidification, potentially invasive species that are predatory or compete for resources

  • Dermo and Haplosporidium which causes MSX
  • pH changes effects on calcification

Northern quahog (shellfish): changes in populations are due to disease (QPX), ocean acidification, potentially invasive species that are predatory or compete for resources

  • % infected clams/area (disease prevalence & intensity)
  • Range changes in parasites

Bay scallops (shellfish): Changes in populations due to habitat loss (eelgrass): ocean acidification,

  • Distribution and abundance of shellfish and habitat (eelgrass)

Is there a change in finfish pathogen abundance and occurrence.

  • Proportion of population infected with the pathogen or annual index of mortalities directly attributable to this disease (difficult)
  • Parasite prevalence, abundance, seasonality, location, pathology: including but not limited to: LironecaLernanthropus, Lernaeenichus

Diadromous fish

  • Trend analyses (similarity coefficient /regression) of survey catch data; correlation of adaptation group abundance and individual species, with LIS temperature data
  • NY would only see changes to timing, more applicable in CT 

Coastal habitats and associated species/systems

Is there evidence of inundation of tidal flats? Are hard clam landings declining in association with decreases in the area of tidal flats? 

  • Hard clam landings from monitoring
  • Bushels or bag-counts (CT) per yr, catch-per-unit-effort (CPUE)
  • Acres of tidal flats
  • Density per acre 
  • Shellfish harvest closures/yr
  • Recruitment

Salt marshes and associated species

  • Change in low:high marsh ratio
  • Elevation (Surface elevation tables - SET’s); mē, by veg type; transects;
  • Extent of Phragmites
  • Chronology of marsh elevation and accretion (SETs & Pb210)

Brackish and freshwater tidal marshes and associated species

  • mē by marsh type;
  • Transects in marshes;
  • Spring freshet (measure freshwater inflow)

Coastal forests, shrublands, grasslands

  • Invasive species distribution and abundance;
  • Veg transects/plots;
  • Species composition;
  • Changes in timing of plant blooms

Sea Cliffs/Bluffs and Escarpments (Primarily NY)

  • mē lost (possibly using aerial photos)

Unvegetated nearshore submerged and intertidal, habitats (mudflats, sandflats, rocky intertidal)

  • mē lost

Barrier beaches/islands

  • USGS Coastal Vulnerability Index (CVI)
Changes to marsh birds, colonial nesting birds, shorebirds, waterfowl
  • Changes in bird population abundance, fecundity, number of nest sites
  • Loss of coastal habitats
  • Potential loss of SAV and other food sources


  • Abundance of particular species of insects

Distribution and Abundance of Terrestrial Invasive species (plant and animal)

  • Distribution and abundance of new invasive species

Eelgrass (Zostera marina) and organisms that depend on eelgrass habitat/food

  • Secchi depth (light penetration)
  • Eelgrass distribution
  • Salinity

SAV (other than eelgrass)

  • Secchi depth (light penetration)
  • SAV abundance and distribution
  • Salinity
  • Temperature
  • pH

Marine mammals & sea turtles

  • Distribution


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