No abstract

The burrowing behavior of three polychaete species, Nereis virens Sars, Glycera dibranchiata Ehlers and Nephtys caeca Fabricius, was examined after variable exposure periods (7, 14, 21 and 28 d) to sediment contaminated with a cadmium concentration of about 40 mg kg−1 (dry weight). Most comparisons of burrowing times and rates between exposed and unexposed worms were not statistically significant. Those that were significant were relatively minor, e.g., a maximum reduction in burrowing time of 6.3 s, and probably would have little ecological relevance. The feeding behavior of G. dibranchiata on the polychaete Euzonus mucronata was not affected by a 28‐d exposure to cadmium‐contaminated sediment. Uptake of cadmium varied among the three species. After 28 d of exposure, cadmium body burdens were highest for N. virens (319mg kg−1), intermediate for G. dibranchiata (120 mg kg−1) and lowest for N. caeca (39 mg kg−1). This potential for bioaccumulation and survival in cadmium‐contaminated sediment indicates that some polychaete species like N. virens may be an amplified source of cadmium for their crustacean, fish and avian predators.

The abundance of nearly one-quarter of the world's shorebird species is declining. At the same time, the number of non-native species in coastal ecosystems is increasing rapidly. In some cases, non-native species may affect negatively the abundance and diversity of shorebird prey species. We conducted an experimental study of the effects of the introduced European green crab (Carcinus maenas) on prey consumption by wintering Dunlin (Calidris alpina) in a central California estuary. We placed green crabs and Dunlin sequentially in field enclosures and measured changes in density of benthic invertebrate prey (e.g. polychaetes and small clams), Dunlin biomass, and gut contents of both Dunlin and crabs and observed foraging behavior of Dunlin. Green crabs significantly affected Dunlin foraging success through both direct and indirect multitrophic linkages. In enclosures with high densities of green crabs, crab foraging reduced the availability of polychaetes, and Dunlin consumed significantly fewer polychaetes compared with Dunlin in enclosures without crabs. High densities of green crabs were also associated with increased availability of small clams. Dunlin consumed significantly more small clams compared with Dunlin in enclosures without crabs. In our literature survey of studies of effects of non-native invasive species on shorebirds, we found three prior experiments that addressed the effect of non-native invasive species on shorebirds. Results of two of these studies showed positive direct effects of non-native invertebrates on shorebirds, 1 showed negative direct effects of a non-native plant on shorebirds through habitat conversion, and none showed indirect effects of non-native invertebrates. We suggest future management of shorebirds explicitly examine how non-native marine species, particularly invertebrates, directly and indirectly affect shorebirds.