Science Serving Maryland's Coasts

Rosaura Chapina, University of Texas El Paso

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Oxygen consumption by Neomysis americana under realistic summer temperatures and salinity conditions

The mysid, Neomysis americana, inhabits shallow shelf waters and estuaries of the western Atlantic coast and plays a critical role in nutrient cycling and food web dynamics in these ecosystems. Despite their importance in these ecosystems, much of their spatial ecology and habitat requirements remain unknown. In Chesapeake Bay tributaries, previous research has shown that summer water temperatures can approach the lethal upper limit for N. americana. In this study, oxygen consumption rate (µg/min) of N. americana from the Patuxent River, a tributary of the Chesapeake Bay, USA, were measured experimentally as an indicator of metabolic stress under realistic temperature and salinity conditions. Mysids were incubated in a fully factorial design comprising three temperature (22, 26, 29°C) and salinity (2, 8, 16 ppt) treatments. The experimental design evaluated sex-specific responses as well as diel differences in oxygen consumption while accounting for mass-specific changes in oxygen consumption rate. Oxygen consumption rates were higher during the day for females and at low temperature (=22°C) and high salinity conditions (=16 ppt). There was no difference in oxygen consumption rate between males and females, but there was an interaction between temperature and salinity during both day and night incubations. Oxygen consumption was depressed at the lowest salinities in the 29°C treatment and in the highest salinities in the 22°C treatment (oxygen consumption rates peaked under intermediate conditions). This study indicates that the metabolic response of N. americana to temperature and salinity conditions is complex and that oxygen consumption rates can vary 3-4 fold within a realistic range of summer temperature and salinity conditions. These results also suggest that oxygen consumption rates should be only one of several indicators used to examine patterns of metabolic stress in N. americana in the wild.