Effects of Hypoxia and Co-Stressors on Early Life-Stages of Estuarine Fishes: Examples from NE USA Estuaries

Estuarine finfish are often subjected to natural and anthropogenic environmental stressors.  In addition to hypoxia, fish may experience temperature extremes and elevated levels of CO₂ and contaminants that, acting singly or in combination, can impair the health of these inshore residents.  The early life-stages of fish are especially vulnerable due to their limited physiological scope and mobility to counter or avoid these stressors.  We have been conducting multi-factor experiments intended to quantify the separate and joint effects of hypoxia, thermal extremes, coastal acidification, and contaminants on three taxa with distinct life histories, ecologies, and positions in the inshore community – Atlantic and shortnose sturgeons (Acipenser oxyrinchus and A. brevirostrum), winter flounder (Pseudopleuronectes americanus), and Atlantic tomcod (Microgadus tomcod).  Each species was/is being experimentally challenged by exposures to contaminants (PCBs, dioxin), elevated CO₂, and/or thermal extremes, then subjected to mild-to-acute hypoxia and scored for sublethal responses including activity level and prey consumption rate.  Results from 2015 studies on sturgeons showed lower activity and consumption by larvae at decreasing DO levels (short-term exposures to low DO down to 2 mg O₂/L) and interactive effects.  Experiments with tomcod (contaminants-temperature-hypoxia) and winter flounder (CO₂-hypoxia) are underway and will also be summarized.