There has been increasing concern about effects of petroleum hydrocarbons and their derivatives on the highly productive North Sea waters. This study reports on possible effects of Ekofisk crude oil on planktonic communities enclosed in medium-scale controlled ecosystems. A 5-mm layer of oil was added to 1 of 2 parallel bags filled before the diatom bloom started in March, and the development followed for 4 wk. Population sizes of bacteria, algae, and zooplankton were estimated; chlorophyll a, mineral nutrients and hydrocarbons were analysed, and primary productivity was measured. In the oil-polluted bag, growth of diatoms and copepods was inhibited, while planktonic bacteria, choanoflagellates and tintinnid ciliates increased. Phosphate probably lim~ted the growth of both algae and bacteria, and was rapidly reduced to very low levels in the bags. The measured concentration of petroleum hydrocarbons and alteration products avcraqed 470 pg I-'. This level may be considered acutely toxic to diatoms. The reasons for the bacterial developn~ents observed, their role in hydrocarbon mineralization, and the predominance of flagellates and tintinnid ciliates are discussed. It is concluded that results from bag experiments may provide important clues to fate and effects of oil pollution at sea.
Enclosed ecosystem experiments with marine plankton were carried out in Rosfjord, Nonuay, March-April, 1979. We report results from studies on planktonic bacteria in natural communities and cultures of phytoplankton contained in l -m diameter flexible plastic bags, and compare these to observations in the surrounding sea. Emphasis was on organotrophic bacteria and their diversity dynamics, particularly in relation to phytoplankton. Five previously isolated strains of bacteria were followed by immunofluorescent staining on membrane filters, and the populations of chromobacteria, bdellovibrios and luminescent bacteria were assayed by specific methods. Secondary productivity of total bacterial populations was estimated from growth rate measurements in filtered seawater and compared to net primary production. Possibly, as much as one third of the net production was ultimately consumed by the bacteria. The highly dynamic state of organotrophic bacterial populations and diversity in the sea are demonstrated, and the roles of substrate quality and concentrations and of potential bacterial grazers in population regulation are discussed.
A strain-specific antibody to Pseudomonas fluorescens was used to develop two enzyme-linked immunosorbent assays: a sandwich and a competitive assay. Both assay types could be used to perform rapid and sensitive detection of the target organism in extracts of sediment samples.
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