National Park Service

Northeast Temperate Network (NETN)

atmospheric deposition and stress

Life History

Rocky intertidal habitat lies between the high and low tide marks, and it is regularly covered and uncovered by the advance and retreat of the tides. Because they are repeatedly exposed to air and tossed to-and-fro by the incessant action of waves when they are underwater, the plants and animals that call this zone home must be hardy and adaptable. Even with the challenges rocky intertidal habitats propose for life there, they are still teeming with a high biodiversity of organisms that have adapted to unique niche zones. The rocks create a fairly stable foundation for the seaweeds and animals that have evolved to depend on this seemingly harsh environment. During low tide, small pools form between the rocks. Here, organisms like crabs, snails, mussels and barnacles, and a variety of seaweeds  are able to thrive, and many species of seabirds visit these ever replenishing pools-of-plenty for a meal. When the tide comes in, larger animals like fish and lobsters are able to take advantage of the shelter and food these rocky settings provide. Other common species found in this habitat include chitons, sea urchins, grazing snails, sea stars, hermit crabs, and sea anemones. Species tend to be arranged spatially in the distinct and dynamic zones created by tidal height, wave exposure, temperature, light, nutrients, salinity, predation, and a whole host of other factors. Differentiated zones in a rocky intertidal environment include the splash zone, which is almost always exposed to air and thus is colonized by only few species; the higher intertidal zone, exposed to air for long periods of time; the mid-intertidal zone, exposed to air for only short periods of time; and the lower intertidal zone, which is exposed only during the lowest tides.

Importance & Issues

jefferson salamanderRocky intertidal zones provide habitat and food for marine and terrestrial organisms and these communities, in turn, provide important economic, scientific, educational, and recreational value for humans.  Intertidal habitats in New England represent some of the best studied ecological communities, in part because the dominant species are large and grow rapidly, and the strong zonation across small spatial scales is attractive for field manipulations.  It is widely recognized that these communities are shaped both by natural abiotic (e.g. dessication) and biotic factors (e.g. competition and predation).  However, these communities are also affected by a variety of anthropogenic stressors including climate change, invasive species, pollution, and trampling.  While the ecological consequences of some of these stressors (e.g. some invasive species) are known for short-term, within-year experiments, their effects are largely unknown over longer time periods.


The Rocky Intertidal Monitoring Protocol has defined 20 target species or species groups to monitor and will correlate changes in species abundance with changes in environmental stress.

Monitoring Objective

An objective of this protocol is to monitor changes in densities of target species in fixed plots over time (both seasonal and annual).  Because intertidal species in Acadia NP and Boston Harbor Islands are patchy or heterogeneous over small spatial scales (pers. obs.) and because logistics will limit the number of samples that can be taken at any given site, fixed plots will be monitored rather than random points. 


Last Updated: December 30, 2016 Contact Webmaster