Patterns of Phytoplankton Production Around the Galapagos Islands

Abstract

For the highly productive regions of the world’s oceans, it is the pattern of physical processes that to a large extent determines the character and richness of the ecosystem. It has long been recognized that the ocean waters around islands are inherently more productive than waters far removed from land (Gilmartin and Revel- ante, 1974; Barber and Chavez, 1983). This increased productivity, which is often referred to in the literature as the Island Mass Effect (Doty and Oguri, 1956) depends primarily on the supply of nutrients to the euphotic zone brought about by enhanced vertical mixing around islands. Localized upwelling on the downstream sides of islands (LaFond and LaFond, 1971), topographically induced upwelling (Houvenaghel, 1978), the formation of island wakes (White, 1973), wind driven coastal or equatorial upwelling and tidal mixing (Kogelschatz et al., 1985) are some of the mechanisms that can produce vertical mixing around islands. Although the mechanisms may differ, the end result is often the same; an increase in the vertical transport of nutrients to the surface waters supporting enhanced levels of phytoplankton biomass and primary production.