Northeast Marine Introduced Species (NEMIS) - Print Edition

Introduced Species of Concern in the Northeast

Introduced Species Not Easily Seen or Indentified

This list identifies groups of introduced organisms that are not easily seen with the naked eye or that live near the coast but not in the water. The small size of an organism does not mean that they do not cause problems. Some introduced species are parasites and disease-causes organisms that affect native species and those in aquaculture. Others become pests by overgrowing native specie species and fouling hulls of ships, docks and piers. Some species becomes "weeds" and require maintenance while others are abundant, but have not been studied to understand their impact. And some, although beautiful to look at, compete with native waterfowl and eat submerged aquatic vegetation, affecting species that live in the vegetation.

These include:

  • Pathogens and Viruses: Disease-causing organisms in bivalves (oysters and clams) that require microscopic examination for identification.
  • Phytoplankton (such as diatoms and dinoflagellates): Some phytoplankton may form long brown strings but are generally seen only with microscopes.
  • Roundworms and flatworms: Some are parasites that affect eels and other animals. Others are predators in the subtidal area.
  • Hydrozoans (hydroids): Small anemone-like animals that form colonies and may foul water pipes and marinas
  • Amphipods (small crustaceans): May be found in the intertidal (called sand hoppers) and subtidal environment where there feed on detritus and small animals. Amphipods can be quite abundant for short periods of time, but introduced species are difficult to distinguish from native species.
  • Isopods (flattened crustaceans): Look like sow bugs, live in the subtidal and intertidal habitats (the intertidal species may reach 3 cm).
  • Insects: Represent several families and are found near the shore or intertidally with the most common being the earwig.
  • Bryozoans: Small animals with tentacles that form upright and encrusting colonies that may be seen in the field, although identification requires magnification of the small individual zooids (animals). These may be significant fouling organisms.
  • Red alga: Introduced species may be very abundant, but are difficult to identify in the field.
  • Seaside plants: Represent several genera with the most common being sea poppies, pepper grass or pepperweed, and Phragmites.
  • Fish: Although not fully established, invasive species of fish, e.g. the lion fish are appearing in Long Island Sound and further north in greater abundances each year.
  • Birds: For example, the mute swan is damaging submerged aquatic vegetation and competing with local waterfowl.