Burrowing activity inMercenaria mercenaria(L.) andSpisula solidissima(Dillwyn) as a function of temperature and dissolved oxygen

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Abstract
Burrowing activity was utilized as a measure of the ability of the hard shell clam (Mercenaria mercenaria) and the Atlantic surf clam (Spisula solidissima) to cope with extremes of temperature and dissolved oxygen. Clams were removed from clean sand substrate and the progress of reburial timed. Experiments were conducted in a once through circulating seawater system in which temperatures were maintained at selected (?T) increments above ambient levels. Results of the thermal experiments indicated a zone of optimum activity, above and below which burrowing declined with changing temperature. Thermal optima, upper limits of activity, and burrowing rates were found to be species specific. Long‐term effects of dissolved oxygen concentration on burrowing were determined using an apparatus constructed to remove oxygen from seawater and reaerate in controlled increments. Ability of M. mercenaria to burrow, when exposed to oxygen impoverished conditions (less than one milligram of oxygen per liter of seawater) for up to three weeks, was not severely or permanently impaired. Species specific responses to temperature and dissolved oxygen are discussed in relation to habitat and geographic distribution of the clams.