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The trophic relationships between suspended marine bacteria and the suspension-feeders Mytilus edulis and Artemia salina

University of British Columbia

The trophic relationships, in terms of growth efficiencies, between suspended marine bacteria and the suspension feeders, the blue mussel, Mytilus edulis and the brine shrimp, Artemia salina, were established. Mytilus edulis could not be supported on suspended bacteria. The growth efficiency of A.salina was dependent upon both the concentration of bacteria in the culture provided as a food source and on the size of the brine shrimp. At concentrations less than 1.5 X 10⁶ cells/ml, young shrimp, less than 1 mm in length, died within a few days (zero growth efficiency). Correspondingly, low filtering rates (less than 1 ml/hour/organism) and low consumption rates (less than 0.1 μg/hour/organism) were observed for these organisms at such low concentrations. For brine shrimp greater in length than 1.0 mm, a bacterial concentration of 2.5 X 10⁶ cells/ml was required before positive growth efficiencies were obtained. As the food concentration increased beyond this concentration, growth efficiencies steadily increased. An upper limit for the concentration of bacterial cells that could be converted into the biomass of A.salina was not detected; the growth efficiencies continued to increase to a maximum of 60% as the bacterial concentrations supplied increased to 10⁷ cells/ml. The growth efficiencies were maximal when Artemia salina obtained a length of 2.5 mm, at which time the highest consumption rates and growth rates were also observed. Growth efficiencies for organisms larger or smaller than 2.5 mm were lower, Bacterial densities, expressed in terms of both cells per ml and the amount of ATP per ml, supported from various types of organic substrates, were determined under varying inorganic nutrient and oxygen regimes. The substrates studied included the seaweeds, Ulva lactuca and Fucus vesiculosus, and the vascular plants, Zostera marina and wood chips. Under nutrient-rich conditions (30 μM NO₃⁻,6.0 μM PO₄⁻³), bacterial densities supported from 1 g (dry weight) of Ulva lactuca reached a maximum of 2 X 10⁷ cells/ml or 12 X 10⁻³ μg ATP/ml. Based on the established trophic relationships, it was calculated that the amount of suspended bacteria per gram dry weight of substrate grown under these conditions can sustain a maximum weight of 46 μg of Artemia salina or adult brine shrimp.

Text

2010-04-21

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http://hdl.handle.net/2429/23974

Oceanography

University of British Columbia

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