Hypotheses to explain high-nutrient conditions in the open sea

Journal Article · Sun Dec 01 04:00:00 EST 1991 · Limnology and Oceanography; (United States)

DOI:https://doi.org/10.4319/lo.1991.36.8.1578· OSTI ID:7222174

Cullen, J J ^[1]

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1. Dalhousie Univ., Halifax, Nova Scotia (Canada)

Ocean high-nutrient, low-chlorophyll waters are characterized principally by the persistence of major nutrients at the sea surface. This condition indicates control of autotrophic production by something other than NO{sub 3} or PO{sub 4}, but the nature of this control is at present unresolved. The range of hypotheses to explain the high-nutrient condition is illustrated by the grazing hypothesis (specific growth rates of phytoplankton are maximal and environmental stability allows development of a balanced food web that maintains low standing crops of phytoplankton) and the iron hypothesis (standing crop of plankton is constrained by availability of Fe: if more Fe were available, the standing crop of phytoplankton would increase and NO{sub 3} would be depleted, despite grazing). The iron hypothesis has been examined experimentally in the subarctic and equatorial Pacific and in Antarctic waters. In each environment, Fe enrichment enhanced the field yield of phytoplankton and that enrichment of high-nutrient waters with Fe would change the species composition of phytoplankton and food-web interactions, thereby enhancing utilization of NO{sub 3}. The magnitude of this enhancement cannot be predicted with confidence.

• OSTI ID: 7222174
• Journal Information: Limnology and Oceanography; (United States), Journal Name: Limnology and Oceanography; (United States) Vol. 36:8; ISSN LIOCA; ISSN 0024-3590
• Country of Publication: United States
• Language: English

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