The effect of salinity change on the oxygen consumption and swimming activity of the high-shore rockpool copepod Tigriopus brevicornis

Abstract

Tigriopus brevicornis is the dominant member of the fauna in high-shore rockpools (above the mean high water of spring tides) that are subject to extreme environmental variation especially in salinity due to infrequent tidal inundation. The present study was designed to assess the effect of large-scale salinity change on the rate of oxygen consumption and levels of activity. Measurements of the rates of oxygen consumption ( V O 2 ) of T. brevicornis in response to simulated changes in salinity (of a magnitude that had previously been recorded in high-shore rock pools inhabited by T. brevicornis) were carried out using closed respirometry. Activity levels of T. brevicornis during exposure to three different salinities (10, 33 and 90 psu) were assessed by means of video image analysis. The study showed that T. brevicornis exhibits a reduction in activity and in oxygen consumption when exposed to higher salinities. However, individuals exposed to low salinities showed elevated rates of oxygen consumption without an associated increase in activity. The present study indicates that animals living in high-shore rockpools may incur a considerable energetic cost, due to the rapid and large-scale environmental changes that are characteristic of this habitat.