Climate and Chlorophyll a: Long-Term Trends in the Central North Pacific Ocean.

Since 1968 a significant increase in total chlorophyll a in the water column during the summer in the central North Pacific Ocean has been observed. A concomitant increase in winter winds and a decrease in sea surface temperature suggest that long-period fluctuations in atmospheric characteristics have changed the carrying capacity of the central Pacific epipelagic ecosystem.

Recurrent Groups of Diatom Species in the North Pacific.

Associations of planktonic diatom species in four epipelagic environments of the North Pacific have been defined using a recurrent group analysis. The distribution of the groups was related to the physical habitats. Within conservative environments the species associations appear relatively permanent, undergoing minor fluctuations in composition and distribution, which may be related to the annual hydrographic cycle. Within the non-conservative environments, species associations appear to redevelop each year, and their composition must depend upon the introduction of seed cells from adjacent environments. Multiple regression analysis was used to examine the relation of the biomass of each recurrent group to selected environmental parameters. The regressions were dominated by hydrographic parameters, emphasizing the importance of surface circulation patterns in the ocean for the creation and maintenance of species associations. The increased importance of the depths parameters during the summer suggests that differential responses to vertical gradients in the environmental may result in the segregation of species groups within any one habitat.