Brackish tidal marshes are river-associated estuarine environments found upstream from salt marshes. The water salinity values of brackish tidal marshes change frequently due to the tidal influence. Salinities may be similar to freshwater tidal marshes (around .05% or less) at low tide, and similar to the ocean (3% or more) during the highest tide. The species composition of brackish tidal marshes is a combination of species characteristic of salt and freshwater tidal marshes due to this factor. Areas with the highest water salinity values are the least diverse.
There are probably less than a dozen occurrences statewide. A few documented occurrences have good viability and a few are protected on public land or private conservation land. This community is restricted to brackish portions of estuaries in the state, and includes a few moderately sized, good quality examples. The current trend of this community is probably declining slightly due to moderate threats that include alteration of the natural hydrology and invasive species. Reed grass (Phragmites australis ssp. australis) appears to be a particular threat to this community.
The number of brackish tidal marshes in New York have probably remained stable in recent decades due to wetland protectection regulations. However, the condition and size of a few occurrences may have declined due to invasive species, such as purple loosestrife and reed grass.
The number of brackish tidal marshes in New York has probably declined substantially from historical numbers as a result of shoreline development (e.g., railroads) and river channel dredging.
The main threats to this community are shoreline development (e.g., railroad tracks that impede or alter tidal flow) and invasion of exotic species, such as reed grass (Phragmites australis ssp. australis), purple loosestrife (Lythrum salicaria), and Japanese knotweed (Reynoutria japonica var. japonica). Reed grass appears to be a particular threat to this community. A lesser threat is chemical run-off from railroad maintenance or accidental spill. Dredging of shipping lanes may also pose a threat by reducing water quality, or decreasing area due to deposition of dredge spoils.
Maintain the natural tidal regime in marshes that have been cut off from the Hudson River by the railroad tracks. Control and remove invasive exotic species, such as purple loosestrife and especially reed grass.
Strive to minimize or eliminate hardened shorelines and maintain low-sloped shorelines within the tidal zone. Maintain functional connectivity between the river and bays with marshes to enable full tidal flushing during each tidal cycle. For example, barriers such as railway causeways should have numerous culverts to allow sufficient hydrologic connectivity.
Review tidal marsh 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 the effects of invasive exotic plants on brackish tidal marshes.
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). It also occurs within the brackish tidal range of the smaller tidal rivers of Long Island (e.g., Carmans and Nissequogue rivers).
This community occurs along the Atlantic coast from Maine to Virginia and possibly to South Carolina.
Brackish tidal marsh communities occur where water salinity levels are between 0.5 to 18 parts per thousand (ppt) and water is less than 2 m (6 feet) at high tide. The vegetation is very dense, dominated by graminoid species, and is made up of a mix of salt marsh and freshwater tidal marsh species. Characteristic species include narrowleaf cattail (Typha angustifolia), crimsoneyed rose mallow (Hibiscus moscheutos), seaside goldenrod (Solidago sempervirens), saltmarsh fleabane (Pluchea odorata), and various bulrushes (Schoenoplectus spp., Bolboschoenus spp.). Brackish tidal marshes that are dominated by reedgrass (Phragmites australis ssp. australis) as a result of anthropogenic disturbance are classified as cultural communities (e.g., estuarine impoundment mash, estuarine dredge spoil). Brackish marshes that have had the tidal influence restricted may be classified as a palustrine cultural community, such as reedgrass/purple loosestrife marsh.
A brackish marsh community made up of a mix of salt marsh and freshwater tidal marsh species dominated by tall graminoids. Water salinity values range from 0.5 to 18 ppt and water depth is less than 2 m (6 feet).
A variety of showy wildflowers bloom in brackish tidal marshes throughout the summer, including crimsoneyed rose mallow (Hibiscus moscheutos), seaside goldenrod (Solidago sempervirens), and saltmarsh fleabane (Pluchea odorata).
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.
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.
Hibiscus moscheutos ssp. moscheutos (swamp rose-mallow)
Solidago sempervirens (northern seaside goldenrod)
Bolboschoenus robustus (sea-coast bulrush)
Impatiens capensis (spotted jewelweed, spotted touch-me-not)
Iris pseudacorus (yellow iris)
Nuphar advena ssp. advena (intertidal yellow pond-lily, intertidal spatter-dock)
Peltandra virginica (green arrow-arum, tuckahoe)
Pontederia cordata (pickerelweed)
Sagittaria latifolia (common arrowhead)
Schoenoplectus americanus (chair-maker's bulrush)
Schoenoplectus tabernaemontani (soft-stemmed bulrush)
Thelypteris palustris var. pubescens (marsh fern)
Typha angustifolia (narrow-leaved cat-tail)
Zizania aquatica var. aquatica (southern wild-rice)
This figure helps visualize the structure and "look" or "feel" of a typical Brackish Tidal Marsh. 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%.
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.
MacDonald, Dana and Gregory Edinger. 2000. Identification of reference wetlands on Long Island, New York. Final report prepared for the Environmental Protection Agency, Wetland Grant CD992436-01. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 106 pp. plus appendices.
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.
Information for this guide was last updated on: April 22, 2021
Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Brackish tidal marsh. Available from: https://guides.nynhp.org/brackish-tidal-marsh/. Accessed February 5, 2023.