Plant and animal carotenoid pigments were isolated from the guts of the copepods Calanus pacificus and Clausocalanus sp, and the cladocerans Evadne spp. by high performance Liquid chromatography. Measured carotenoid concentrations were converted to eshmates of class-specific phytoplankton biomass and total microzooplankton biomass In the zooplankton diets. Different pigments were present in the guts at dfferent times of day and night and the tllnmg of peak gut fullness var~ed between species. In C. pacificus, pigment concentrat~ons were highest during the period from evening twilight to midnight. Evadne spp. exhibited a midnight peak In gut pigmentation. Clausocalanus sp. contained elevated levels of pigments between midnight and noon. The gut contents of C. pacificus and Evadne spp. were dominated by animal carbon when phytoplankton biomass and productivity were relatively low, and by algal carbon when phytoplankton biomass and productivity were high. Clausocalanus sp. did not follow this pattern. Our observations are consistent with the hypothesis that carnivory may represent an important mode of feeding among small zooplankton and, further, that the diets of some species of zooplankton vary in response to quantitative and qualitative attributes of the food environment.

Latitudinal variations in the megascale (103 km) distribution of biological properties are described in relation to water column structure between 60° and 7°N in the eastern North Atlantic Ocean. Stations were occupied along a meridional transect of stations at 20°W in August‐September, 1988, during the third leg of the National Oceanic and Atmospheric Administration Global Change Expedition. An additional transect to the south (38°N to 7°N) was occupied to extend the total range of latitudinal observations. Chlorophyll a concentrations were highest in the northern latitudes (<2.51 mg m−3) , decreasing to >0.2 mg m−3 in the vicintiy of the subtropical gyre, south of 40°N. The nitracline was associated with a shoaling of the pycnocline in the northern latitudes. At 7°N, high chlorophyll concentrations (approximately 0.5 mg m−3), and enhanced primary productivity (375.5 mg C m−2 d−1) were associated with a lens of fresh Amazon River Water. Primary productivity rates were variable throughout the transect, ranging from 646.10 mg C m−2 d−1 to 138.26 mg C m−2 d−1. Productivity maxima were located south of Iceland, at 46°N (646.10 mg C m−2 d−1) and in the vicinity of the Azores Front at 35°N (259.85 mg C m−2 d−1). Latitudinal distributions of primary productivity corresponded closely to a model of productivity along a transect at 40°N by Yentsch (1990).