Brackish Subtidal Aquatic Bed

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System
Estuarine
Subsystem
Estuarine Subtidal
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
S3S4
Vulnerable in New York, or Apparently Secure - Vulnerable to disappearing from New York (but not currently imperiled), with relatively few populations or locations, few individuals, and/or restricted range; or uncommon but not rare in New York; may be rare in some parts of the state; possibly some cause for long-term concern due to declines or other factors. More information is needed to assign either S3 or S4.
Global Conservation Status Rank
G4
Apparently Secure globally - Uncommon in the world but not rare; usually widespread, but may be rare in some parts of its range; possibly some cause for long-term concern due to declines or other factors.
Contents
  1. Summary
  2. Conservation and Management
  3. Range
  4. Identification Comments
  5. Classification
  6. Additional Resources
  7. About This Guide

Summary

Did you know?

One of the common plants in brackish subtidal aquatic beds are coontails (Ceratophyllum spp.). The name originates from the shape of their leaves and branches, which resemble the tail of a raccoon. Their flowers have tiny green scales, and are located at the leaf base. Male and female flowers develop separately on the same plant. The male flowers occur in pairs on opposite sides of the stem while the female flowers are solitary.

State Ranking Justification

There are probably far fewer than 50 occurrences statewide. Very few documented occurrences have good viability and very few are protected on public land or private conservation land. This community is restricted to brackish portions of estuaries in the state. The current trend of this community is probably stable to declining slightly due to moderate threats that include alteration of the natural hydrology and invasive species.

Short-term Trends

The number of brackish subtidal aquatic beds in New York have probably remained stable in recent decades. The quality of the water in tidal rivers, and thus their associated brackish subtidal aquatic bed communities, has probably improved in recent decades.

Long-term Trends

The number of brackish tidal marshes in New York probably declined substantially from historical numbers as a result of shoreline development and river channel dredging.

Conservation and Management

Threats

The brackish subtidal aquatic beds on the Hudson River are recovering from several hundred years of pollution, shoreline development, dredging, commercial shipping, recreational overuse, invasive species, etc. Smaller brackish subtidal aquatic beds on tidal rivers on Long Island have had similar impacts, but at a smaller scale. Although water chestnut (Trapa natans) is a serious threat to freshwater subtidal aquatic beds, large patches are not generally located within the brackish portions of the Hudson River.

Conservation Strategies and Management Practices

Maintain tidal regime in coves cut off from the Hudson River by railroad tracks. Control and remove invasive exotic species, such as water chestnut (Trapa natans).

Development and Mitigation Considerations

Development activities that involve the manipulation of the river substrate (e.g., dredging, installing submerged structures, etc.) should be avoided in areas where mudflats naturally occur. Marinas adjacent to mudflats should use buoys to direct boat traffic away from these shallow areas.

Inventory Needs

Review subtidal aquatic vegetation (SAV) maps and data collected by partner organizations, and incorporate this information into the New York Natural Heritage database. Resurvey and update occurrences with records greater than 10 years old.

Research Needs

Research the effects of invasive exotic plants and animals on brackish subtidal aquatic beds.

Rare Species

  • Najas muenscheri (Hudson River Water Nymph) (guide)

Range

New York State Distribution

The range of this community primarily corresponds to the brackish tidal range of the Hudson River (i.e., from between New Hamburg/Poughkeepsie downstream about 25 miles to Hastings-on-Hudson), and perhaps within the brackish tidal range of the smaller tidal rivers of Long Island.

Global Distribution

This community occurs along the Atlantic coast from Maine to Virginia and possibly to South Carolina.

Best Places to See

  • Hudson River National Estuarine Research Reserve (Rockland County)
  • Tallman Mountain State Park (Rockland County)

Identification Comments

General Description

Brackish subtidal aquatic beds are continuously flooded aquatic communities, characterized by rooted aquatic vegetation. The water salinity values range from 0.5 to 18 parts per thousand (ppt), and the water depth at low tide is typically less than 2 m (6 feet). Plant species may include sago pondweed (Stuckenia pectinata), widgeon grass (Ruppia maritima), coontail (Ceratophyllum demersum), and naiad (Najas guadalupensis).

Characters Most Useful for Identification

A brackish aquatic community of continuously flooded substrates with rooted aquatic vegetation and water salinity values in the range of 0.5 to 18 ppt. The water depth at low tide is typically less than 2 m (6 feet).

Elevation Range

Known examples of this community have been found at elevations between -3 feet and -1 feet.

Best Time to See

The aquatic plants that are characteristic of brackish subtidal aquatic beds are best observed during the growing season.

Classification

International Vegetation Classification Associations

This New York natural community encompasses all or part of the concept of the following International Vegetation Classification (IVC) natural community associations. These are often described at finer resolution than New York's natural communities. The IVC is developed and maintained by NatureServe.

  • Sago Pondweed - Claspingleaf Pondweed - (Horned Pondweed) Tidal Marsh (CEGL006027)

NatureServe Ecological Systems

This New York natural community falls into the following ecological system(s). Ecological systems are often described at a coarser resolution than New York's natural communities and tend to represent clusters of associations found in similar environments. The ecological systems project is developed and maintained by NatureServe.

Characteristic Species

  • Emergent aquatics

    • Ruppia maritima (widgeon-grass, ditch-grass)

  • Submerged aquatics

    • Ceratophyllum demersum (common coon-tail)
    • Elodea nuttallii (Nuttall's waterweed)
    • Najas guadalupensis (Guadalupe water-nymph, Guadalupe naiad)
    • Stuckenia pectinata (Sago pondweed)
    • Zannichellia palustris (horned pondweed)

Similar Ecological Communities

  • Brackish intertidal mudflats (guide)
    Brackish intertidal mudflats are in intertidal zones (flooded tidally, and exposed at low tide) and are charactertized by low-growing rosette-leaved aquatic plant species. Brackish subtidal aquatic bed communities are in subtidal zones (flooded continuously).
  • Brackish intertidal shore
    Brackish intertidal shore communities occur along intertidal rocky or gravelly shores, and are not continuously flooded. Brackish subtidal aquatic bed communities are in subtidal zones (flooded continuously).
  • Freshwater subtidal aquatic bed
    Freshwater subtidal aquatic beds are continuously flooded and charactertized by rooted aquatic plant species, but the water salinity values are less than 0.5 ppt. Brackish subtidal aquatic beds have salinity values that range from 0.5 to 18 ppt. Freshwater tidal communities are located upstream from brackish tidal communities.
  • Marine eelgrass meadow (guide)
    Marine eelgrass meadows are subtidal communities that have salinity values greater than 18 ppt, whereas brackish subtidal aquatic beds have salinity values that are lower (0.5 to 18 ppt).

Vegetation

Emergent aquatics
0%
Submerged aquatics
0%

Percent cover

This figure helps visualize the structure and "look" or "feel" of a typical Brackish Subtidal Aquatic Bed. Each bar represents the amount of "coverage" for all the species growing at that height. Because layers overlap (shrubs may grow under trees, for example), the shaded regions can add up to more than 100%.

Additional Resources

References

Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero (editors). 2014. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke’s Ecological Communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY. https://www.nynhp.org/ecological-communities/

Edinger, Gregory J., D.J. Evans, Shane Gebauer, Timothy G. Howard, David M. Hunt, and Adele M. Olivero (editors). 2002. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke's Ecological Communities of New York State. (Draft for review). New York Natural Heritage Program, New York State Department of Environmental Conservation. Albany, NY. 136 pp.

Kiviat, Erik and Gretchen Stevens. 2001. Biodiversity assessment manual for the Hudson River Estuary Corridor. New York State Department of Environmental Conservation. Albany, NY.

Macomber, R.T. and D. Allen. 1979. The New Jersey submersed aquatic vegetation distribution atlas final report. Prepared for the New Jersey Department of Env. Protection, Division of Coastal Resources, Bureau of Coastal Planning and Development. Trenton, New Jersey.

Metzler, K. and R. Rosza. 1982. Vegetation of fresh and brackish tidal marshes in Connecticut. Newsletter of the Connecticut Botanical Society 10(1): 1-3.

Muenscher, W.C. 1937. VII. Aquatic vegetation of the Lower Hudson area. 1936. Biological Survey. 11:231-248.

New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.

Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.

Senerchia-Nardone, P., A. Reilly, and M.M. Holland. 1985. Comparison of vascular plant zonation at Iona Island Marsh (Hudson River Estuary) and Lord's Cove Marsh (Connecticut River Estuary). In: Polgar Fellowship Reports of the Hudson River National Estuarine Sanctuary Program 1985. J.C. Cooper, Editor. Hudson River Foundation, New York, New York.

Links

About This Guide

This guide was authored by: Gregory J. Edinger

Information for this guide was last updated on: April 6, 2021

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Brackish subtidal aquatic bed. Available from: https://guides.nynhp.org/brackish-subtidal-aquatic-bed/. Accessed December 8, 2023.