Seasonal resource partitioning patterns of marine calanoid copepods: Species interactions

Abstract

Acartia hudsonica (Pinhey) and Temora longicornis (O.F. Muller) differ in many ways, but they exhibit similar feeding patterns. The quantity of spheres ingested by each species decreased seasonally (fall-summer) and was significantly less in the presence of other species. The food niche width of each species was largest in the fall but decreased and overlapped completely in early summer. These results suggest that Acartia hudsonica and Temora longicornis are more sensitive than Pseudocalanus sp. to temporal variation of the food environment. The niche width of these species was affected both by species interactions and by food levels, with Acartia hudsonica being more sensitive to species interactions. Individuals of Pseudocalanus sp. do not respond to seasonal (February–June) changes of the food environment. This is reflected in the narrow food niche width which did not change on a seasonal basis. The average amount of food ingested varied little on a seasonal basis, but increased significantly in the presence of other species. Species interactions with Temora longicornis and Acartia hudsonica as well as food levels affected niche width and the between phenotype component of niche width.