ABSTRACT. New England coastal and adjacent Nova Scotia shelfwaters have a reduced buffering capacity because of significant freshwater input, making the region's waters potentially more vulnerable to coastal acidification. Nutrient loading and heavy precipitation events further acidify the region's poorly buffered coastal waters. Despite the apparent vulnerability of these waters, and fisheries' and mariculture's significant dependence on calcifying species, the community lacks the ability to confidently predict how the region's ecosystems will respond to continued ocean and coastal acidification. Here, we discuss ocean and coastal acidification processes specific to New England coastal and Nova Scotia shelf waters and review current understanding of the biological consequences most relevant to the region. We also identify key research and monitoring needs to be addressed and highlight existing capacities that should be leveraged to advance a regional understanding of ocean and coastal acidification.

Abstract. The limited available evidence about effects on marine fishes of high CO2 and associated acidification of oceans suggests that effects will differ across species, be subtle, and may interact with other stressors. This report is on the responses of an array of early life history features of summer flounder (Paralichthys dentatus), an ecologically and economically important flatfish of the inshore and nearshore waters of the Mid-Atlantic Bight (USA), to experimental manipulation of CO2 levels. Relative survival of summer flounder embryos in local ambient conditions (775 μatm pCO2, 7.8 pH) was reduced to 48% when maintained at intermediate experimental conditions (1808 μatm pCO2, 7.5 pH), and to 16% when maintained at the most elevated CO2 treatment (4714 ppm pCO2, 7.1 pH). This pattern of reduced survival of embryos at high-CO2 levels at constant temperature was consistent among offspring of three females used as experimental subjects. No reduction in survival with CO2 was observed for larvae during the first four weeks of larval life (experiment ended at 28 d post-hatching (dph) when larvae were initiating metamorphosis). Estimates of sizes, shapes, and developmental status of larvae based on images of live larvae showed larvae were initially longer and faster growing when reared at intermediate- and high-CO2 levels. This pattern of longer larvae – but with less energy reserves at hatching – was expressed through the first half of the larval period (14 dph). Larvae from the highest-CO2 conditions initiated metamorphosis at earlier ages and smaller sizes than those from intermediate- and ambient-CO2 conditions. Tissue damage was evident in larvae as early as 7 dph from both elevated-CO2 levels. Damage included dilation of liver sinusoids and veins, focal hyperplasia on the epithelium, and separation of the trunk muscle bundles. Cranio-facial features changed with CO2 levels in an age-dependent manner. Skeletal elements of larvae from ambient-CO2 environments were comparable or smaller than those from elevated-CO2 environments when younger (7 and 14 dph) but were larger at developmental stage at older ages (21 to 28 dph), a result consistent with the accelerated size-development trajectory of larvae at higher-CO2 environments based on analysis of external features. The degree of alterations in the survival, growth, and development of early life stages of summer flounder due to elevated-CO2 levels suggests that this species will be increasingly challenged by future ocean acidification. Further experimental studies on marine fishes and comparative analyses among those studies are warranted in order to identify the species, life stages, ecologies, and responses likely to be most sensitive to increased levels of CO2 and acidity in future ocean waters. A strategy is proposed for achieving these goals.

Fish behavior can be altered by contaminants. There is an extensive literature on laboratory behavioral assays, with many chemicals impairing feeding or predator avoidance. However, there is not extensive work on fishes that live in contaminated environments. Therefore, we then review our recent research on feeding and trophic relations of populations from contaminated estuaries compared with relatively unpolluted sites. The mummichog Fundulus heteroclitus, is a non-migratory fish; those from more contaminated areas are poor predators and slower to capture active prey (grass shrimp, Palaemonetes pugio). In the field, they consume much detritus and sediment, which is not nutritious. They are less active than fish from cleaner sites and more vulnerable to predation. They have altered thyroid glands and neurotransmitter levels, which may underlie altered behaviors. Fish from the reference site kept in tanks with sediment and food from the polluted site showed bioaccumulation and reduced prey capture after two months, although fish from the polluted site did not show significant improvement when maintained in a clean environment. Poor nutrition and predator avoidance may be responsible for their being smaller and having a shorter life span than reference fish. Bluefish Pomatomus saltatrix, are a marine species in which the young-of-the-year spend their first summer in estuaries. We found bioaccumulation of contaminants and reduced activity, schooling, and feeding in young-of-the-year bluefish from a relatively unpolluted site that were fed prey fish from a contaminated site. They also had altered thyroid glands and neuro-transmitter levels. Many field-caught specimens had empty stomachs, which is rare in this species. In the fall, when they migrate back out to the ocean, they are smaller, slower, and more likely to starve or to be eaten than those that spent their summer in cleaner estuaries.

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