Gene expression and DNA methylation changes in response to hypoxia in toxicant-adapted Atlantic killifish ().

Coastal fish populations are threatened by multiple anthropogenic impacts, including the accumulation of industrial contaminants and the increasing frequency of hypoxia. Some populations of the Atlantic killifish (), like those in New Bedford Harbor (NBH), Massachusetts, have evolved a resistance to dioxin-like polychlorinated biphenyls (PCBs) that may influence their ability to cope with secondary stressors. To address this question, we compared hepatic gene expression and DNA methylation patterns in response to mild or severe hypoxia in killifish from NBH and Scorton Creek (SC), a reference population from a relatively pristine environment.

High PCO2 does not alter the thermal plasticity of developing Pacific herring embryos during a marine heatwave.

Forage fish tend to respond strongly to environmental variability and therefore may be particularly sensitive to marine climate stressors. We used controlled laboratory experiments to assess the vulnerability of Pacific herring (Clupea pallasii) embryos to the combined effects of high partial pressure of carbon dioxide (PCO2) and a simulated marine heatwave. The two PCO2 treatments reflected current conditions (∼550 µatm) and a future extreme level (∼2300 µatm).

Are long-term growth responses to elevated pCO2 sex-specific in fish?

Whether marine fish will grow differently in future high pCO2 environments remains surprisingly uncertain. Long-term and whole-life cycle effects are particularly unknown, because such experiments are logistically challenging, space demanding, exclude long-lived species, and require controlled, restricted feeding regimes-otherwise increased consumption could mask potential growth effects. Here, we report on repeated, long-term, food-controlled experiments to rear large populations (>4,000 individuals total) of the experimental model and ecologically important forage fish Menidia menidia (Atlantic silverside) under contrasting temperature (17°, 24°, and 28°C) and pCO2 conditions (450 vs.

Diel and tidal pCO × O fluctuations provide physiological refuge to early life stages of a coastal forage fish.

Coastal ecosystems experience substantial natural fluctuations in pCO and dissolved oxygen (DO) conditions on diel, tidal, seasonal and interannual timescales. Rising carbon dioxide emissions and anthropogenic nutrient input are expected to increase these pCO and DO cycles in severity and duration of acidification and hypoxia. How coastal marine organisms respond to natural pCO × DO variability and future climate change remains largely unknown.

High sensitivity of a keystone forage fish to elevated CO and temperature.

Sand lances of the genus are keystone forage fish in coastal ecosystems across the northern hemisphere. Because they directly support populations of higher trophic organisms such as whales, seabirds or tuna, the current lack of empirical data and, therefore, understanding about the climate sensitivity of sand lances represent a serious knowledge gap. Sand lances could be particularly susceptible to ocean warming and acidification because, in contrast to other tested fish species, they reproduce during boreal winter months, and their offspring develop slowly under relatively low and stable CO conditions.

A quantitative genetic approach to assess the evolutionary potential of a coastal marine fish to ocean acidification.

Assessing the potential of marine organisms to adapt genetically to increasing oceanic CO2 levels requires proxies such as heritability of fitness-related traits under ocean acidification (OA). We applied a quantitative genetic method to derive the first heritability estimate of survival under elevated CO2 conditions in a metazoan. Specifically, we reared offspring, selected from a wild coastal fish population (Atlantic silverside, Menidia menidia), at high CO2 conditions (∼2300 μatm) from fertilization to 15 days posthatch, which significantly reduced survival compared to controls.