Posts Tagged 'multiple factors'



Negative effects of diurnal changes in acidification and hypoxia on early-life stage estuarine fishes

Estuaries serve as important nursery habitats for various species of early-life stage fish, but can experience cooccurring acidification and hypoxia that can vary diurnally in intensity. This study examines the effects of acidification (pH 7.2–7.4) and hypoxia (dissolved oxygen (DO) ~ 2–4 mg L−1) as individual and combined stressors on four fitness metrics for three species of forage fish endemic to the U.S. East Coast: Menidia menidia, Menidia beryllina, and Cyprinodon variegatus. Additionally, the impacts of various durations of exposure to these two stressors was also assessed to explore the sensitivity threshold for larval fishes under environmentally-representative conditions. C. variegatus was resistant to chronic low pH, while M. menidia and M. beryllina experienced significantly reduced survival and hatch time, respectively. Exposure to hypoxia resulted in reduced hatch success of both Menidia species, as well as diminished survival of M. beryllina larvae. Diurnal exposure to low pH and low DO for 4 or 8 h did not alter survival of M. beryllina, although 8 or 12 h of daily exposure through the 10 days posthatch significantly depressed larval size. In contrast, M. menidia experienced significant declines in survival for all intervals of diel cycling hypoxia and acidification (4–12 h). Exposure to 12-h diurnal hypoxia generally elicited negative effects equal to, or of greater severity, than chronic exposure to low DO at the same levels despite significantly higher mean DO exposure concentrations. This evidences a substantial biological cost to adapting to changing DO levels, and implicates diurnal cycling of DO as a significant threat to fish larvae in estuaries. Larval responses to hypoxia, and to a lesser extent acidification, in this study on both continuous and diurnal timescales indicate that estuarine conditions throughout the spawning and postspawn periods could adversely affect stocks of these fish, with diverse implications for the remainder of the food web.

Continue reading ‘Negative effects of diurnal changes in acidification and hypoxia on early-life stage estuarine fishes’

Resilience of oxygen consumption rates in the juvenile blue crab Callinectes sapidus to future predicted increases in environmental temperature and pCO2 in the Mesohaline Chesapeake Bay

Quantifying the physiological impact of environmental stressors on living organisms is critical to predicting the response of any given species to future climate scenarios. Oxygen consumption rates (μmol/g/min) were measured to examine the physiological response of the juvenile blue crab Callinectes sapidus from the Chesapeake Bay (Patuxent River, Maryland) to elevated temperature and dissolved carbon dioxide in water (pCO2) reflective of projected future climate scenarios. Treatment levels were selected to represent current conditions in the Chesapeake Bay (26°C and 800 μatm) and conditions predicted to occur by the year 2100 (31°C and 8,000 μatm). Crabs were exposed in a factorial design to these conditions throughout two successive molts (approximately 30 days). At the end of the exposure, the oxygen consumption rates of individual crabs were determined over at least a 10-h period using a flow-through respiration chamber equipped with optical oxygen electrodes. No significant effect of temperature or pCO2 on oxygen consumption was observed, suggesting the absence of a respiratory impact of these two climate stressors on juvenile blue crabs. Oxygen consumption rates were also determined for crabs that experienced a rapid increase in temperature without prior acclimation. The oxygen consumption rate of crabs may have acclimated to increased temperature during the 30-day exposure period before respiratory measurement. This potential acclimation, combined with high individual variability, and a relatively small difference in temperature treatments are likely the cause for the lack of a statistically significant difference in mean oxygen consumption rates by temperature in the core experiment. The results of this study suggest that the blue crab may be quite resilient to future climate stressors and underscore the need for species-specific studies to quantify the effects of climate change on estuarine crustaceans.

Continue reading ‘Resilience of oxygen consumption rates in the juvenile blue crab Callinectes sapidus to future predicted increases in environmental temperature and pCO2 in the Mesohaline Chesapeake Bay’

Effects of thermal stress and ocean acidification on the expression of the retrotransposon steamer in the softshell Mya arenaria

The softshell Mya arenaria is an ecologically and commercially important bivalve mollusc that develops a fatal cancer known as disseminated neoplasia or hemocyte leukemia. This cancer, like many human cancers, involves the master control gene of apoptosis, p53. This gene is also known to interact with retrotransposons, and a growing body of evidence suggests that p53 actually controls retrotransposon expression and subsequently oncogenesis. The recent description of a retrotransposon (i.e., Steamer) in adult M. arenaria and its potential involvement in the oncogenesis of hemocyte leukemia has been suggested. Juvenile clams, previously shown not to develop hemocyte leukemia, were exposed to climate-related changes in seawater temperature and pH predicted for the year 2100. All juvenile softshells do express the retrotransposon Steamer. When juvenile clams are exposed to predicted climate-related changes in temperature and pH in the Gulf of Maine, it significantly induces Steamer expression, specifically in treatments where clams were exposed to low pH. For juvenile individuals of M. arenaria and potentially other bivalves, Steamer may be a candidate biomarker for exposure to ocean acidification conditions.

Continue reading ‘Effects of thermal stress and ocean acidification on the expression of the retrotransposon steamer in the softshell Mya arenaria’

Effects of temperature and ocean acidification on the extrapallial fluid pH, calcification rate, and condition factor of the king scallop Pecten maximus

Increasing anthropogenic carbon dioxide is predicted to cause declines in ocean pH and calcium carbonate saturation state over the coming centuries, making it potentially harder for marine calcifiers to build their shells and skeletons. One mechanism of resilience to ocean acidification is an organism’s ability to regulate pH and, thus, calcium carbonate saturation state, at its site of calcification. This mechanism has received detailed study in scleractinian corals but is relatively understudied in other taxonomic groups that are vulnerable to ocean acidification, such as bivalves. Here, the results of a 74-day controlled laboratory experiment investigating the impact of ocean acidification on the extrapallial fluid (EPF; the bivalve calcifying fluid) pH, calcification rate, and condition factor of the king scallop Pecten maximus at their average spring and summer temperatures (362 ppm/9.0°C, 454 ppm/12.3°C; 860 ppm/9.0°C, 946 ppm/12.3°C; 2,639 ppm/8.9°C, 2,750 ppm/12.1°C) are presented. Scallop EPF pH was lower than seawater pH in all treatments and declined with increasing pCO2 under the spring temperature (9°C) but was uncorrelated with pCO2 under the summer temperature (12°C). Furthermore, king scallop calcification rate and EPF pH were inversely correlated at 9°C and uncorrelated at 12°C. This inverse correlation between EPF pH and scallop calcification rate, combined with the observation that scallop EPF pH is consistently lower than seawater pH, suggests that pH regulation is not the sole mechanism by which scallops concentrate carbonate ions for calcification within their EPF. Calcification trends contrasted most other published studies on bivalves, increasing with ocean acidification under spring temperature and exhibiting no response to ocean acidification under summer temperature. Scallop condition factor exhibited no response to ocean acidification under spring temperature but increased with ocean acidification under summer temperature—exactly the opposite of their calcification response to ocean acidification. These results suggest that king scallops are relatively resilient to CO2-induced ocean acidification, but that their allocation of resources between tissue and shell production in response to this stressor varies seasonally.

Continue reading ‘Effects of temperature and ocean acidification on the extrapallial fluid pH, calcification rate, and condition factor of the king scallop Pecten maximus’

Elevated CO2 and food ration affect growth but not the size-based hierarchy of a reef fish

Under projected levels of ocean acidification, shifts in energetic demands and food availability could interact to effect the growth and development of marine organisms. Changes to individual growth rates could then flow on to influence emergent properties of social groups, particularly in species that form size-based hierarchies. To test the potential interactive effects of (1) food availability, (2) elevated CO2 during juvenile development, and (3) parental experience of elevated CO2 on the growth, condition and size-based hierarchy of juvenile fish, we reared orange clownfish (Amphiprion percula) for 50 days post-hatching in a fully orthogonal design. Development in elevated CO2 reduced standard length and weight of juveniles, by 9% and 11% respectively, compared to ambient. Development under low food availability reduced length and weight of juveniles by 7% and 15% respectively, compared to high food. Parental exposure to elevated CO2 restored the length of juveniles to that of controls, but it did not restore weight, resulting in juveniles from elevated CO2 parents exhibiting 33% lower body condition when reared in elevated CO2. The body size ratios (relative size of a fish from the rank above) within juvenile groups were not affected by any treatment, suggesting relative robustness of group-level structure despite alterations in individual size and condition. This study demonstrates that both food availability and elevated CO2 can influence the physical attributes of juvenile reef fish, but these changes may not disrupt the emergent group structure of this social species, at least amongst juveniles.

Continue reading ‘Elevated CO2 and food ration affect growth but not the size-based hierarchy of a reef fish’

Seabream larval physiology under ocean warming and acidification

The vulnerability of early fish stages represents a critical bottleneck for fish recruitment; therefore, it is essential to understand how climate change affects their physiology for more sustainable management of fisheries. Here, we investigated the effects of warming (OW; +4 °C) and acidification (OA; ΔpH = 0.5) on the heart and oxygen consumption rates, metabolic enzymatic machinery—namely citrate synthase (CS), lactate dehydrogenase (LDH), and ß-hydroxyacyl CoA dehydrogenase (HOAD), of seabream (Sparus aurata) larvae (fifteen days after hatch). Oxygen consumption and heart rates showed a significant increase with rising temperature, but decreased with pCO2. Results revealed a significant increase of LDH activity with OW and a significant decrease of the aerobic potential (CS and HOAD activity) of larvae with OA. In contrast, under OA, the activity levels of the enzyme LDH and the LDH:CS ratio indicated an enhancement of anaerobic pathways. Although such a short-term metabolic strategy may eventually sustain the basic costs of maintenance, it might not be adequate under the future chronic ocean conditions. Given that the potential for adaptation to new forthcoming conditions is yet experimentally unaccounted for this species, future research is essential to accurately predict the physiological performance of this commercially important species under future ocean conditions. View Full-Text

Continue reading ‘Seabream larval physiology under ocean warming and acidification’

Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal

Highlights

• Investigation of optimized culture conditions in temperature, salinity, and pH for mysid mass-culture and development as a laboratory model

• Identification of strong correlations between growth parameter and 20E level in environmental fluctuations

• Measurement of maternal effects of environmental fluctuations on second generation

Abstract

Mysids are experimental models and are among the most important food items for animals in aquaria and that support fisheries, and even for humans, but information on their performance in controlled culture systems is still limited. We reared the marine mysid Neomysis awatschensis in a controlled laboratory system, and measured its growth, 20–hydroxyecdysone (20E) levels, molting, and survival in response to environmental fluctuations in temperature, pH, and salinity, and inferred their potential associations based on annual field sampling. The 20E levels were significantly elevated during the postnauplioid stages, and even higher levels of 20E were maintained in the adult stages than in the nauplioid stages. Values of growth parameters (i.e. total length and the lengths of the antennal scale, expod, endopod, and telson) and 20E levels were higher during a 40-day period at 25 °C than at other temperatures, with shorter intermolt intervals, although morality was also increased. Among the surviving mysids, the number of newly hatched juveniles produced was higher for females exposed to 20 °C than that in other groups. Relatively higher growth and survival rates were measured at salinities over 25 practical salinity, while lower salinities under 15 practical salinity significantly reduced growth and survival. The number of newly hatched juveniles was lower at salinities under 15 practical salinity compared to those over 20 practical salinity. Overall, low temperature and salinity reduced mysid reproduction and the maintenance of the second generation. In the case of pH variation (pH of 7.0–8.0), there were no significant effects on growth and the number of newly hatched juveniles, although the survival rate was slightly lower and the 20E level fluctuated at a pH of 7.0. We believe that these associations between growth and environmental conditions can provide crucial information for optimizing mass mysid culture for experimental and ecotoxicological usage in the laboratory.

Continue reading ‘Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal’


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Ocean acidification in the IPCC AR5 WG II

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