Example 8: Characterization of Ecological Receptors

Example 8: Characterization of Ecological Receptors - Winter Flounder

The winter flounder is a coastal demersal species with a primary range in cold-temperate boreal waters.

Winter flounder occur at depths from the intertidal to 150 m and on hard or soft mud, clay, sand, or

pebble bottoms of bays, estuaries, and coastal waters (Bigelow and Schroeder 1953). Perlmutter (1947)

suggested the existence of many discrete local stocks based on several key observations: demersal eggs,

nondispersive larvae, juvenile phases, and complete lack of adult mixing with other stocks.

Winter flounder spawn in most estuaries from Chesapeake Bay through the Gulf of Maine from

midwinter to early spring (Azarovitz 1982). It is believed that winter flounder return to the same

spawning location year after year (NMFS 1986). Winter flounder eggs are demersal and adhesive, and

therefore the spawning and nursery areas for the species should coincide.

In areas north of Cape Cod, winter flounder remain in bays and harbors year-round, moving into deeper

holes and channels during the warmest weather (Azarovitz 1982).

Winter flounder feed by sight near the bottom. For example, Pearcy (1962) showed that fish fed in a dark

room did not eat until zooplankton died and sank to the bottom. Field observations confirmed that feeding

occurs during the day. These organisms are clearly bottom dwellers who spend significant portions of

their lives in close contact with sediments.

It is also significant that winter flounder eat bottom-dwelling organisms because the consumption of

these organisms provides another potential exposure pathway. Several investigators (Pearcy 1962;

MacPhee 1969; Frame 1972) noted that they are omnivorous, opportunistic feeders, and prey upon

polychaete worms, amphipod and isopod crustaceans, pelecypods, and plant material.

Note that this example continues with assessing risk to winter flounder. The risk assessment should

similarly address other selected receptors such as a representative benthic organism(e.g., softshell clams)

or water-column organisms which may concentrate COCs from suspended sediments.

Assessment and Measurement End Points

What are Assessment and Measurement End Points?

An assessment end point is an explicit expression of the actual environmental

value to be protected (USEPA 1992a) during the management of the dredged

materials. The term applies only to ecological risk assessment. The environmental

values most commonly refer to valuable ecological resources that:

a. Are critical to the normal functioning of an ecosystem such as a diverse

benthic community structure.

b. Provide critical resources such as a fishery or sensitive habitat.

c. Are perceived as valuable by humans such as endangered species.

Chapter 2 Problem Formulation