The seasonal occurrence of Neocalanus cristatus,Neocalanus plumchrus,and Eucalanus bungii over the shelf of the northern Gulf of Alaska

Field collections of zooplankton from the northern Gulf of Alaska demonstrate that the large oceanic copepods Neocalanus cristatus, N. plumchrus, and Eucalanus bungii are seasonal members of shelf and coastal zooplankton communities. They account for more than 25% of the net zooplankton biomass (0.333 mm) during the spring and summer months.The presence, absence, and subsequent reappearance of these copepods over the shelf is apparently related to their seasonal shifts in vertical distributions and to a persistent pattern of onshore Ekman transport. During periods when these copepods occur in the surface water of the bordering deep ocean (late autumn to summer) they are swept shoreward over the shelf. During times when they occur below the Ekman layer, they are generally absent from the shelf.The ecological significance of this seasonally introduced biomass is discussed in terms of what is understood about these species from studies elsewhere in the North Pacific Ocean.