Item

Abstract

Biogeochemical processes in the ocean are (to a large extent) regulated by the
physico-chemical characteristics of the microenvironment where the processes
occur. In the pelagic, phytoplankton, bacteria and small grazers interact and
regulate the productivity in response to environmental variables like temperature,
salinity or availability of nutrients and trace elements. Hot spots of metabolic
activities are found in aggregates of microalgae or e.g. in planktonic
foraminifera or radiolaria harbouring microalgal symbionts. Also, during the
continuous export ofbiomass (e.g. dead or dying phytoplankton, faecal material
and other organic debris) from the euphotic zone of the ocean, ca. 0.5-5 mm
large aggregates (marine snow) are formed that are rapidly mineralised during
their journey to the sea floor. In the open ocean, recycling of carbon and other
essential elements thus mainly takes place in the water column, while only
refractory material reaches the seafloor, where it is slowly degraded and buried.
The deep sea sediment is thus a major sink for carbon on a global scale.