Marine Rocky Intertidal

Marine rocky intertidal (close up) with Forbes sea star on Fishers Island
Gregory J. Edinger

Marine Intertidal
State Protection
Not Listed
Not listed or protected by New York State.
Federal Protection
Not Listed
State Conservation Status Rank
Critically Imperiled in New York (most likely) - Conservation status is uncertain, but most likely especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines. More information is needed to assign a firm conservation status.
Global Conservation Status Rank
Secure globally - Common in the world; widespread and abundant (but may be rare in some parts of its range).


Did you know?

Organisms of marine rocky intertidal environments are adapted to survive under particularly dynamic conditions. The organisms (e.g., algae, sea stars, barnacles, mussels) of this community are exposed to moisture changes, temperature extremes, wave energy, and water salinity changes. For example, as the water recedes during low tide, pools remain in the low spots of the rocky substrate. The organisms that spend low tide within these pools face heat and desiccation stress as the water warms from the sun and evaporates, concentrating the salt levels to a level higher than that of the ocean. Following a heavy rain, however, the water salinity of the tide pools may become close to that of freshwater.

State Ranking Justification

There are an estimated 10 to 20 extant occurrences statewide. A few documented occurrences have good viability, but the level of protection of most occurrences is uncertain. This community has a very limited distribution in the state and is restricted to the portions of the state that have rocky ocean shorelines. There are at least three large, high quality examples (Fishers Island, Plum Island, and Montauk Point). The current trend of this community is probably stable in the short term, but may decline slightly in the future due to moderate threats that include alteration of the natural shoreline, invasive species, and sea level rise.

Short-term Trends

The number and acreage of marine rocky intertidal communities in New York have probably remained stable in recent decades as a result of coastal protection regulations, although some examples may be reduced in size by the spread of non-native invasive marine algae.

Long-term Trends

The number and acreage of marine rocky intertidal communities in New York has probably declined moderately from historical numbers likely correlated to the alteration of the ocean shoreline by development.

Conservation and Management


The primary threat to marine rocky intertidal communities is the spread of invasive marine species. Non-native marine algae include Green Fleece (Codium fragile) and Devil's Tongue Weed (Grateloupia turuturu). Invasive marine fauna include European Green Crab (Carcinus maenas), Asian Shore Crab (Hemigrapsus sanguineus), and Common Periwinkle (Littorina littorea). Sea level rise and increasing ocean temperatures In addition, marine rocky intertidal communty occurrences are threatened by trampling, shoreline development, pollution run-off from upland areas, and trash dumping. Ocean derived pollution may threaten marine rocky intertidal communities. Over-collecting of tidal pool fauna may be a minor threat at a few sites.

Conservation Strategies and Management Practices

Where practical, establish and maintain a natural shoreline buffer to reduce storm-water, pollution, and nutrient run-off, while simultaneously capturing sediments before they reach the rocky shore. Buffer width should take into account the erodibility of the surrounding soils, slope steepness, and current land use. Avoid habitat alteration within the intertidal area and surrounding landscape. Restore sites affected by unnatural disturbance (e.g, remove obsolete sea walls and drain pipes in order to restore the natural tidal regime). Prevent the spread of invasive exotic species into the intertidal area through appropriate direct management.

Development and Mitigation Considerations

When considering development activities, minimize actions that will change what water carries and how water travels to the rocky shore. Water traveling over-the-ground as run-off usually carries an abundance of silt, clay, and other particulates during (and often after) a construction project. While still suspended in the water, these particulates make it difficult for aquatic animals to find food; after settling to the bottom, these particulates bury small plants and animals and alter the natural functions of the community in many other ways. Development activities near this community type should strive to minimize particulate-laden run-off into this community. Water traveling on the ground or seeping through the ground also carries dissolved minerals and chemicals. Fertilizers, detergents, and other chemicals that increase the nutrient levels in tidal areas. Herbicides and pesticides often travel far from where they are applied and have lasting effects on the quality of the natural community.

Inventory Needs

Survey for occurrences statewide to advance documentation and classification of marine rocky intertidal areas. A statewide review of marine rocky intertidal communities is desirable. Minimally, revisit sites with records older than ten years, and ideally collect plot data for all occurrences across littoral zones. Continue searching for large sites in good condition (A- to AB-ranked).

Research Needs

Research the influence that sea level rise has on the structure and composition of marine rocky intertidal areas. Research is needed to determine the distribution and invasiveness of Codium fragile and other non-native organisms to this community. Research composition of marine rocky intertidal areas statewide in order to characterize floral and faunal variations across the littoral gradient.

Rare Species

  • Charadrius melodus (Piping Plover) (guide)
  • Egretta thula (Snowy Egret) (guide)
  • Plantago maritima var. juncoides (Seaside Plantain) (guide)


New York State Distribution

This community is restricted to the rocky ocean shores in Bronx, Westchester, and Suffolk counties. The largest examples are found on Fishers Island, Nappeague Bay, and Plum Island.

Global Distribution

The marine rocky intertidal community occurs along the Atlantic coast from New York to Labrador.

Best Places to See

  • Montauk Point State Park (Suffolk County)
  • Hither Hills State Park (Suffolk County)

Identification Comments

General Description

A community inhabiting rocky shores that are washed by rough, high-energy ocean waves. Characteristic organisms are attached marine algae, mussels, sea stars, urchins, and barnacles that can withstand the impact of the waves and periodic desiccation. The community is typically rich in species. Attached organisms usually cover more than 60% of the substrate, especially at the lower intertidal zone. Characteristic marine algae attached to the rocks include knotted wrack (Ascophyllum nodosum), rockweeds (Fucus vesiculosis, F. spiralis), Irish moss (Chondrus crispus), green seaweed (Blidingia minima), hollow green weeds (Enteromorpha prolifera, E. intestinalis), sea lettuce (Ulva lactuca), green fleece (Codium fragile), filamentous green algae (Rhizoclonium tortuosum, R. riparium), red algae (Hildenbrandia sp.), and red tubed weed (Polysiphonia lanosa). Characteristic marine invertebrates include common blue mussel (Mytilus edulis), northern rock barnacle (Balanus balanoides), common periwinkle (Littorina littorea), rough periwinkle (Littorina saxatilis), little gray barnacle (Chthamalus fragilis), oyster drill (Urosalpinx cinerea), and Atlantic dogwinkle (Nucella lapillus). Tidal pools may include ribbed mussel (Geukensia demissa), Forbes' sea star (Asterias forbesi), eastern mudsnail (Ilyanassa obsoleta), hermit crabs (Pagurus spp.), and eastern oyster (Crassostrea virginica).

Characters Most Useful for Identification

A rocky intertidal shoreline exposed to high-energy wave action. Often 60% or more of the rocky substrate is covered with attached organisms, such as algae, mussels, barnacles, sea stars, and other invertebrates. At low tide, rocky intertidal communities have isolated tide pools that contain algae and animals, which are trapped until the next high tide.

Elevation Range

Known examples of this community have been found at elevations between -4 feet and 17 feet.

Best Time to See

Rocky marine intertidal communities can be observed throughout the year, but during the warm months, when the water is warm enough for wading, this community is particularly pleasant and interesting to explore. At low tide, isolated tide pools remain in the low spots of the rock, and a variety of algae, invertebrate animals, and fish can be easily observed.

Marine Rocky Intertidal Images


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.

  • Yellow Tang - Black Tang Tidal Algal Nonvascular Vegetation (CEGL006341)

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

  • Submerged aquatics

    • Ascophyllum nodosum
    • Blidingia minima
    • Chondrus crispus
    • Codium fragile
    • Enteromorpha intestinalis
    • Enteromorpha prolifera
    • Fucus spiralis
    • Fucus vesiculosis
    • Hildenbrandia spp.
    • Polysiphonia lanosa
    • Rhizoclonium ripariumn
    • Rhizoclonium tortuosum
    • Ulva lactuca

Similar Ecological Communities

  • Brackish intertidal mudflats (guide)
    Unlike marine rocky intertidal communities, which have high-energy wave action and rocky substrates, brackish intertidal mudflats are characterized by quiet waters, unconsolidated soils, and lower water salinity values. Marine rocky intertidal communities are flooded tidally with full-strength ocean water, which is higher in salt content.
  • Brackish intertidal shore
    Brackish intertidal shore communities occur on rocky substrate, but they are not exposed to the high-energy wave action of marine rocky intertidal communities, and they are flooded tidally with water that is brackish (ranging from 0.5 to 18 ppt). Marine rocky intertidal communities are flooded tidally with full-strength ocean water, which is higher in salt content.
  • Marine eelgrass meadow (guide)
    Unlike marine eelgrass meadows, which are characterized by quiet waters and unconsolidated sandy to sandy loam soils, marine rocky intertidal communities have high-energy wave action, occur on rocky substrates, and are dominated by marine algae, not eelgrass.
  • Marine intertidal gravel/sand beach (guide)
    Marine intertidal gravel/sand beaches have sand or gravel substrates that are well-drained at low tide and they are largely unvegetated. Whereas, marine rocky intertidal communities occur on rocky shores that are washed by rough, high-energy ocean waves and dominated by attached marine algae and marine fauna.
  • Marine intertidal mudflats (guide)
    Unlike marine rocky intertidal communities, which have high-energy wave action and rocky substrates, marine intertidal mudflats are characterized by quiet waters and unconsolidated soils. Marine intertidal mudflats occur on fine silt or sand that is rich in organic material. They are exposed at low tide, and have a diverse array of invertebrates that provide important fuel for migrating and breeding shorebirds.
  • Maritime beach (guide)
    While both communities can occur on rocky substrate along the ocean shoreline, marine rocky intertidal communities are washed by rough, high-energy ocean waves and are dominated by attached marine algae and fauna. They are exposed at low tide and extend inland to the limit of mean high tide. Whereas, maritime beaches are very sparsely vegetated, or unvegetated, terrestrial communities that are located in a band just above this tidal limit and the substrate is more often sand.


Submerged aquatics

Percent cover

This figure helps visualize the structure and "look" or "feel" of a typical Marine Rocky Intertidal. 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


Brown, B. 1993. A classification system of marine and estuarine habitats in Maine: An ecosystem approach to habitats. Part 1: benthic habitats. First iteration. Maine Natural Areas Program. Department of Economic and Community Development. Augusta, ME.

Conard, H.S. 1935. The plant associations of central Long Island. American Midland Naturalist 16:433-515.

Day, C.H. 1987. Life on Intertidal Rocks. Nature Study Guild, Rochester, New York.

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.

Edinger, G. J., E. S. Runnells, and T. G. Howard. 2019. Montauk Point, Marine Rocky Intertidal Monitoring, Year One 2018 Baseline Results. New York Natural Heritage Program, Albany, NY.

Gosner, K.L. 1978. A Field Guide to the Atlantic Seashore. Peterson Field Guides. Houghton Mifflin Company, New York, New York.

Kunstler, D. and P. Capainolo. 1987. Huckleberry Island: Premier waterbird colony of western Long Island. Kingbird 37:178-188.

New York Natural Heritage Program. 2024. 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.

Schlesinger, M.D., E.L. White, S.M. Young, G.J. Edinger, K.A. Perkins, N. Schoppmann, and D. Parry. 2016. Biodiversity Inventory of Plum Island, New York. New York Natural Heritage Program, Albany, New York, and SUNY College of Environmental Science and Forestry, Syracuse, NY.

Weiss, H.M. 1995. Marine Animals of Southern New England and New York: Identification keys to common nearshore and shallow water macrofauna. Bulletin 115. State Geological and Natural History Survey of Connecticut. Department of Environmental Protection, Hartford, CT.

White, S.K. (ed.). 2003. Life Between the Tides: marine plants and animals of the northeast. Tilbury House Publishers, Gardiner, ME.


About This Guide

Information for this guide was last updated on: December 12, 2023

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Marine rocky intertidal. Available from: Accessed June 23, 2024.