Charles Osterberg

Nutrient and Plankton Ecology of the Columbia River Estuary

Monthly samples of nutrients, phytoplankton and zooplankton were taken in the Columbia River estuary over a period of 16 months in order to determine distribution with season and salinity, and interrelationships between plankton and nutrients. Nitrate and phosphate levels in the river water entering the estuary are high in the winter and show depletion during the summer. Silicate levels are high in the river water at all seasons. During the summer up—welling season nitrate and phosphate levels in the entering ocean water are high. Although nutrient levels in the estuary generally show a linear relationship with salinity, nutrients tend to be enriched in the bottom waters of the central part of the estuary. The estuarine phytoplankton is primarily composed of freshwater species, and probably represents a downstream extension of the river flora. Linear regression analysis indicates a strong correlation between phytoplankton abundance and solar radiation. The estuary zooplankton is composed of fresh water, oligohaline and polyhaline forms. Eurytemora affinis, an oligohaline form, is the major zooplankter, reaching population densities of 100,000/m3 or more. Regression analysis indicates a strong correlation between abundance of freshwater zooplankter and river temperature. Regression analysis indicates close correlation between phosphate levels and Eurytemora abundance. This indicates a strong potential for zooplankton regeneration of phosphate necessary for phytoplankton growth.

Chromium-51 in Sea Water: Chemistry

Chromium-SI introduced into the Pacific Ocean from the Columbia River remains in the hexavalent state. Analysis of this radionuclide in sea water by hydroxide coprecipitation with iron is best accomplished if the chromium-51 is first reduced to the trivalent state.

Chromium-51 as a Radioactive Tracer of Columbia River Water at Sea.

The plume of the Columbia River was followed 350 kilometers to sea by measurement of its chromium-51 content. This radioactive tag, introduced into the river by nuclear reactors at Hanford, Washington, promises to provide a useful oceanographic tool for determining rates of transport and mixing, and for identifying plume waters in the presence of other sources of fresh water.

NATURAL AND ARTIFICIAL RADIONUCLIDES IN SEAFOODS AND MARINE PROTEIN CONCENTRATES.

The concentrations of various radionuclides in seafoods have been measured, and the results indicate that if marine protein concentrates are used as human food the 210Pb–210Po pair may become the principal source of the skeletal radiation dose.

Radioactivity: Detection of Gamma-Ray Emission in Sediments in situ

A probe for measuring emission of γ-rays in sediments in situ in water depths to about 35 meters was used to measure radioactivity in the Columbia River estuary and Oregon coastal areas. This technique offers some advantage over methods in which sediment samples are collected at sea and returned to the laboratory for radioanalysis.