Herbert Curl

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.

Spectral Absorption of Solar Radiation in Alpine Snowfields

We measured penetration of solar radiation into snow at various times of the year with a spectral radiometer. We found that light absorption obeys a y = axn law where n varies from 0.71 to 2.10. The absorption coefficient n decreases with increasing snow density. The 1% of surface value of total energy occurs at a snow depth of approximately 18 cm in winter, increasing to a maximum of 110 cm in late summer when snow density is near its maximum. Penetration of 0.1% of the surface radiation is shown to coincide with the approximate date and depth of snow pack for the first spring bloom of snow algae, implying that increasing light penetration may initiate germination of overwintering stages.

Primary production measurements in the north coastal waters of South America

Measurements of surface light intensity, water transparency and concentration of chlorophyll a were made in the northern coastal waters of South America during October and November 1958. Phytoplankton collections were made simultaneously. The highest gross production rates were encountered in the Gulf of Cariaco (3·75 g C/m2/day), over the Cariaco Trench (2·30 g C/m2/day), in Lake Maracaibo (1·23 g C/m2/day) and the Gulf of Venezuela (1·20 g C/m2/day). Upwelling appears to be the source of nutrients for production in the Gulfs of Cariaco and Venezuela. This relationship is less well established over the Cariaco Trench. High silt concentrations limit light for photosynthetic production in the Gulf of Darien, at the mouth of the Magdalena River and to the east of Margarita Island. Phytoplankton reduces materially the light available for photosynthesis in Lake Maracaibo.