Abstract
The upper‐layer net‐zooplankton community in Prince William Sound, Alaska, is characterized by strong seasonality. Abundance and wet‐weight biomass in the upper 50 m drop to fewer than 100 individuals and 10 mg m −3 in February before rebounding to 5000 individuals and 600 mg m −3 in June. Copepods dominate in all months, but are augmented by other prominent taxa, particularly pteropods and larvaceans during the late spring, summer and fall. The small copepods Pseudocalanus , Acartia and Oithona are common. Though much less abundant, larger calanoids like Neocalanus , Calanus and Metridia contribute substantially to the biomass in spring and early summer. Meroplankters like barnacle nauplii are also occasionally very abundant. Neocalanus , Calanus and Pseudocalanus all exhibit ontogenetic vertical displacement of populations when stage 5 copepodites (C5) leave the surface in late May and early June for deep water. This seasonality has implications for food‐webs supporting juvenile pink salmon ( Oncorhynchus gorbuscha ) and Pacific herring ( Clupea pallasi ) in Prince William Sound.