Intertidal and Shallow Subtidal Populations Sample Clauses

Intertidal and Shallow Subtidal Populations. Intertidal regions of Port Xxxxxx are subject to a large degree of natural variability. Organisms living there must be tolerant of extreme seasonal changes in temperature, light, and salinity, although shallow subtidal communities are influenced to a lesser extent. Intertidal and shallow subtidal zones are subject to contaminants transported from the land by runoff and from chemicals or debris that float or are contained in marine surface waters. Organisms in these zones may live in the sediments (e.g., worms and clams), move around at the surface of the sediments (e.g., crabs and small crustaceans), attach to or move over rocky substrates (e.g., algae, mussels, limpets, snails and barnacles), or associate with other plants and animals (e.g., small snails living in beds of intertidal algae). Intertidal and shallow subtidal invertebrates make up a substantial proportion of the diet of sea stars, fishes, birds, and sea otters. The types of organisms that are found in the intertidal zone depend on the substrate. Although the majority of the coastline in Port Xxxxxx is rocky, large mudflats and gravelly beaches occur in the Port. Mudflats and the adjacent shallow subtidal regions, which are most extensive at the head of the Port, support small invertebrates in the sediment. Polychaete worms, the clam Macoma balthica, large numbers of harpacticoid copepods, and cumaceans are common in these areas (Xxxxx et al., 1976; Xxxxx and Xxxxxx, 1980; Xxxxx and Xxxx, 1980; Xxxx et al., 1979; Xxxxx and Xxxxxx-Xxxxxxxx, 1988; Xxxxx et al., 1990; Xxxxx and Xxxxxxxxx, 1995b). Water held within the silty sediments of mudflats maintains a high salinity throughout the year, which protects sediment-dwelling organisms from exposure to low-salinity water in the summer (Xxxxx et al., 1976; Xxxxxx and Xxxxx, 1977). Diatoms and filamentous green algae grow along the mud surface. This growth increases in the spring and is fed on by harpacticoid copepods and other invertebrates (Xxxxx et al., 1976; Xxxxxx and Xxxxx, 1977). Shallow subtidal sediments contain mostly polychaete worms and clams (Axinopsida and Macoma spp.) (Xxxx et al., 1979; Xxxxx and Xxxxxx-Xxxxxxxx, 1988; Xxxxx and Xxxxxxxxx, 1996a). The rocky shoreline ranges from rock outcroppings and steep rocky beaches to shallow broken rock, cobble, or gravel beaches. A variety of marine plants such as rockweed (Fucus distichus) attach to the rocky substrate, providing shelter for a variety of intertidal animals (XxXxx and Xxxxxx, 1...