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In North America, studies regarding effects of CO2-induced low pH in bivalve aquaculture are largely restricted to the US Pacific coast. Studies on species from the northwest Atlantic are lacking. Furthermore, information on the roles of intergenerational exposure and biological sex in bivalve responses to low pH, particularly in an aquaculture-specific context, is scant. We tested if short-term (1 month) exposure to CO2-induced reductions in pHNBS affected the reproductive development of male and female eastern oysters (Crassostrea virginica) during hatchery-specific reproductive conditioning and whether maternal and/or paternal exposure influenced larval responses. Reduced pH (7.5–7.7) increased the rate of reproductive development in both males and females. There was no indication of intergenerational effects; adult pH conditions did not affect early larval development. In contrast, low pH conditions experienced by gametes during spawning, fertilization, and embryo incubation (48 h) resulted in higher larval survival (+6–8% from control), reduced shell height (−2 to 3 µm), and increased deformities (abnormal shell shape; +3–5%). We suggest that local adaptation to acidic land runoff may account for the positive effects of low pH observed in this study. Bioeconomic assessments are now needed to understand the implications of reduced pH on aquaculture operations in these regions of Atlantic Canada. [ABSTRACT FROM AUTHOR]

The impact of simulated seawater acidification and warming conditions on specimens of the mussel Mytilus galloprovincialis locally adapted to very distinct, widely separated sites in the Mediterranean Sea (Tunisia) and Atlantic Sea (Galicia, NW Spain) was evaluated in relation to key behavioural and eco-physiological parameters. Over the 2-month exposure to the experimental conditions, mussels were fed optimally to ensure that there are no synergistic interactions between climate change drivers and energetic status of the individuals. In general, regardless of origin (Atlantic or Mediterranean), the mussels were rather resilient to acidification for most of the parameters considered and they were able to grow in strongly acidified seawater through an increased feeding activity. However, shell strength decreased (40%) consistently in both mussel populations held in moderately and highly acidified seawater. The observed reduction in shell strength was not explained by slight alterations in organic matter, shell thickness or aragonite:calcite ratio. The combined effects of high acidification and warming on the key response of byssus strength caused a strong decline in mussel performance, although only in Galician mussels, in which the valve opening time decreased sharply as well as condition index (soft tissue state) and shell growth. By contrast, the observed negative effect of highly acidified scenario on the strength of Tunisian mussel shells was (partly but not totally) counterbalanced by the higher seawater temperature. Eco-physiological and behavioural interactions in mussels in relation to climate change are complex, and future scenarios for the ecology of the species and also the feasibility of cultivating them in Atlantic and Mediterranean zones are discussed. [ABSTRACT FROM AUTHOR]

This study aims at better understanding of the physiological changes that occur during the winter months in Eastern oysters (Crassostrea virginica) living at their northernmost distributional limit (48°N). It was conducted in northeastern New Brunswick, Canada (47°49'N, 64°46'W). Oysters were held in Vexar® bags on the bottom of a bay and collected before (December) and during (January-April) the ice-cover period. Winter mortality was <5%. A significant decrease in the concentration of lipids stored in the digestive gland (from 42.0 to 22.5mg/g wet tissue) indicated that the animals had access to oxygen, probably through minimal shell openings. Proteins were also used, although less heavily (decrease from 68.0 to 59.1mg/g wet tissue), leading to an accumulation of ammonia in the intrapallial fluid (up to 0.83 μM), which is modest considering the length of time the animals lived as almost closed systems. In contrast, carbohydrates appear to play a minor role in winter energetics. Low pH values of intrapallial fluid were noted in late winter (c. 7.0) as compared with those measured at the onset of winter and in spring (c. 7.7). The animals used more energy substrates in late than in early winter, which might be partly related to the necessity to intensify detoxification mechanisms as toxic metabolites accumulate. Despite the fact that oysters do not filter-feed at temperatures <0 °C, the mass of the digestive gland increased by a factor of 1.5 during early winter, presumably as the result of nutrient transfer from other tissues. The ability of C. virginica to use energy-rich substrates and to minimize the accumulation of catabolic byproducts could partly explain the ability of the species to survive prolonged subzero conditions. [ABSTRACT FROM AUTHOR]

Temperature affects nearly all biological rates and consequently is fundamental to individual development time and timing of phenological events. One example is the duration of the pelagic larval stage of mussels, which is crucial for determining the magnitude and timing of recruitment, as well as population dispersal patterns. Understanding the impact of temperature on the rate of larval development is key to predicting the timing of settlement and optimizing mussel seed collection. Advising mussel farmers on Prince Edward Island about the ideal timing for collector deployment is one of the goals of the Mussel Monitoring Program (MMP). In this study we examine the relationship between the phenology of larval development based on MMP data, and satellite measurements of sea surface temperature. The analyses indicated that the first day of the year on which 1 0 - 2 0% of the pool of mussel larvae reached 250 mm could be predicted using the thermal integral measure growing degree-days. While this finding confirmed the importance of temperature for mussel larval phenology, the effect of other environmental variables such as phytoplankton quantity and quality cannot be dismissed. [ABSTRACT FROM AUTHOR]