Diurnal and Seasonal Changes in Distribution of Two Planktonic Ostracods, Conchoecia elegans and Conchoecia alata minor

Abstract

Diurnal and seasonal changes in the distributions of two planktonic ostracods, Conchoecia elegans Sars and C. alata minor McHardy, have been considered in relation to changes in the temperature, salinity, oxygen concentration, and subsurface light in Indian Arm, British Columbia. Both species occurred frequently throughout the water column except near the surface. There is the suggestion (reinforced by data from other B.C. inlets) of an upper temperature limit for C. alata minor, which is lower than for C. elegans. Salinity and dissolved oxygen environments appear to have been similar for the two species. An upinlet displacement of both species-populations which took place in the early months of the year could possibly have been initiated by water which had intruded into the depths of Indian Arm. The vertical distributions of the two species showed statistically significant changes which varied with time of day, season, and geographic position. It was not possible to show that the depth of daylight distribution was strongly related to the penetration of light.