Variation in the abundance and distribution ci zooplankton is an inherent characteristic ci pelagic marine ecosystems. In this chapter, we discuss how patterns of abundance and distribution &JC affected by the life cycle characteristics c:I some rl the predominant macrowoplankton west c::l the Antarctic Peninsula.Because ci the importance of Antarctic krill, EuphausitJ Sllptrba. within this region, some aspects ci its ecoiolY ~ given special .uentian. Of particular relevance to rum:nt hypotheses is the association of krill and sea icc , and new evidence is presented for winter habilal Icgreg_tion between adult and larval Slages. Subsequent discussion focuses 00 strategies for winter survival, and variation in recruilmenl. Finally, we discuss the effects of abiotic facton such as frontal shifts, and biotic factors such as food composition, as they ~late to abundance and distribution ci zooplankton .

No abstract

No abstract

SUMMARY A recent model for olfactory foraging by procellariiform seabirds suggests that these birds use biogenic sulfur compounds to locate productive areas for foraging in the southern oceans. The present study refines a simple approach to test birds' responses to odors on land and extends our knowledge to a northern species, the Leach's storm-petrel (Oceanodroma leucorhoa). Rather than working at sea, we tested the behavioral response to dimethyl sulfide (DMS) at night in breeding colonies on Kent Island, New Brunswick,Canada. Birds were presented with either 5 ml DMS (100 μmol l–1 concentration) or control (water) solutions from a platform 1.5 m in height positioned in a flyway 10 m from a breeding colony. We also tested birds' responses to cod liver oil, a well-established olfactory attractant of procellariiforms foraging at sea. Leach's storm-petrels approached DMS presentations nearly twice as frequently as they approached controls. We next compared the distribution of approaches against a Poisson process to test for evidence of social cueing. We found that approaches to DMS were significantly clustered. By contrast, the distribution of approaches did not depart significantly from a Poisson distribution for either cod liver oil or control presentations. Taken together, these results suggest that Leach's storm-petrels can smell DMS and potentially use it as a foraging cue. The results are consistent with the hypothesis that the detection of biogenic sulfur compounds in combination with other cues assists birds in locating foraging hotspots.

No abstract