Temperature regulation of nitrate uptake: a novel hypothesis about nitrate uptake and reduction in cool-water diatoms

Article Abstract:

It has been hypothesized that increase in nonnutritional nitrate uptake is in proportion to the imbalance between light energy harvesting and imbalance . This novel hypothesis relating to temperature regulation in nitrate uptake and reduction in cool-water diatoms has been tested by studies of nitrate uptake kinetics and of direct short-term temperature manipulation of field diatom-dominated populations from Delaware and Chesapeake Bays at fall and spring bloom times. Absolute rates of nitrate uptake by a Rhizoselenia-dominated population did not seem to saturate even at concentrations of 180 microM-N. A negative relationship existed between short-term temperature shifts and nitrate uptake, but a positive one was found between short-term temperature shifts and ammonium ion and urea uptake. If a significant fraction of nitrate uptake is regulated by nonnutritional mechanisms in cells, and if a part of nitrogen reduced by that means is later released as nitrite, ammonium or dissolved organic nitrogen, estimates of new production based only on nitrate uptake might be seriously skewed.

United States, Physiological aspects, Chesapeake Bay, Oceanographic research, Temperature, Delaware Bay

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Rhizosolenia mats: an overlooked source of silica production in the open sea

Article Abstract:

Rhizosolenia mats, an overlooked source of silica production in the open sea of the North Pacific, are discussed as investigated both west and east of the Hawaiian Islands. Mats were collected from the upper 25 m of the water column twice each day. Mat abundance at 6 depths was recorded using flowmeter-equipped frames going a known distance through the water. It appears that silicic acid uptake in mats is not restricted to on stage of their migration. The mats may significantly contribute to global silica production.

Hawaii, Silica, Marine biology, Silicon dioxide

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Enhancement of new production in the northeast subarctic Pacific Ocean during negative North Pacific index events

Article Abstract:

Time-series surface nitrate data from 1965-1990 from the northeast subarctic Pacific has been used in a study of interannual variability of atmospheric and oceanic conditions in relation to new production. Topics include differences in surface nitrate, increases in export production, sedimenting particulate organic nitrogen, formulation of a simple ecosystem model, and the relationship between increase in f-ratio, phytoplankton community structure, and changes in the North Pacific index.

El Nino, El Nino Current, Marine productivity

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