The role of grazing in nutrient-rich areas of the open sea
- Univ. of Washington, Seattle (United States)
No single factor accounts fully for the persistently low phytoplankton stocks in the nutrient-rich areas of the open sea. However, grazing plays the necessary role of consuming phytoplankton produced in excess of losses due to physical processes and sinking. Without grazing, even if specific growth rate of the phytoplankton is less than optimal for the prevailing light and temperature conditions, as might be so under limitation by a trace nutrient such as Fe, the phytoplankton stock would still accumulate with attendant depletion of nutrients. Observations during spring and summer in the open subarctic Pacific argue against limitation of phytoplankton growth to the point where phytoplankton stock could not increase in the absence of grazing. An ecosystem process model of the phytoplankton-grazer interaction suggests that two processes - grazing control of phytoplankton stock and preferential utilization of NH{sub 4} by the phytoplankton - are sufficient to explain the continuously low phytoplankton stock and high concentrations of macronutrients. However, the grazing control may be exerted on a phytoplankton assemblage structured by Fe limitation. In particular, the intrinsic growth rates of potentially fast-growing diatoms seem to be depressed in the open subarctic Pacific. These conditions probably apply to two other nutrient-rich areas of the open sea, the Pacific equatorial upwelling region and the subantarctic circumpolar ocean, although in the latter region light limitation of phytoplankton growth may be more severe and silica limitation may influence the specific composition of the phytoplankton assemblage.
- OSTI ID:
- 7250615
- Journal Information:
- Limnology and Oceanography; (United States), Vol. 36:8; ISSN 0024-3590
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
29 ENERGY PLANNING
POLICY AND ECONOMY
PACIFIC OCEAN
BIOGEOCHEMISTRY
PHYTOPLANKTON
PRODUCTIVITY
AMMONIUM COMPOUNDS
CARBON SINKS
GROWTH
IRON
NUTRIENTS
SILICON OXIDES
UPWELLING
AQUATIC ORGANISMS
CHALCOGENIDES
CHEMISTRY
ELEMENTS
GEOCHEMISTRY
METALS
OXIDES
OXYGEN COMPOUNDS
PLANKTON
PLANTS
SEAS
SILICON COMPOUNDS
SINKS
SURFACE WATERS
TRANSITION ELEMENTS
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)
560300 - Chemicals Metabolism & Toxicology
290301 - Energy Planning & Policy- Environment
Health
& Safety- Regional & Global Environmental Aspects- (1992-)