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Abstract
Heat dissipation and oxygen uptake of the soft shell clam Mya arenaria were measured during long term experiments. Clams from both intertidal and subtidal habitats all exhibited a conspicuous alternating pattern of either high or very low metabolic activity, with an up to 23-fold difference between the two rates.
The heat dissipation of intertidal clams from Loves Cove, Maine was 1–3 µW during low activity, and 11–41 µW at high activity. These clams spent 9-61%of the measured interval at a high heat dissipation. The alternating pattern in heat dissipation of intertidal clams did not demonstrate a distinct relation to the tidal pattern.
The oxygen uptake of intertidal clams from Lagten Beach, Denmark during low and high activity was 1–8 µmol O2 g-1 h-1 and 23–28 µmol O2 g-1 h1, respectively, with the active periods lasting 60–81% of the total measured interval. Subtidal clams from Sebbersund, Denmark showed an oxygen uptake during low activity of 8–34 µmol O2 g-1 h-1 , while the oxygen uptake during high activity was 32–124 µmol O2 g-1 h-1 , lasting 31–61%of the measured interval. The temporal variations in oxygen uptake of intertidal and subtidal M. arenaria were also found at decreased oxygen tensions, with periods without detectable oxygen uptake. M. arenaria from Legten Beach showed a decrease in oxygen uptake at decreasing ambient oxygen tensions, which became pronounced below 78 mm Hg, while M. arenaria from Sebbersund showed a uniform oxygen uptake down to 39 mmHg, below which oxygen uptake also declined rapidly.
It is argued that care should be taken when assuming constant metabolic activity of M. arenaria in predictive models of ecosystem energy flow.