Posts Tagged 'mortality'

Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)

Ocean acidification, the ongoing decline of surface ocean pH and [CO32-] due to absorption of surplus atmospheric CO2, has far-reaching consequences for marine biota, especially calcifiers. Among these are teleost fishes, which internally calcify otoliths, critical elements of the inner ear and vestibular system. There is evidence in the literature that ocean acidification increases otolith size and alters shape, perhaps impacting otic mechanics and thus sensory perception. However, existing analyses of otolith morphological responses to ocean acidification are limited to 2-dimensional morphometrics and shape analysis. Here, we reared larval Clark’s anemonefish, Amphiprion clarkii (Bennett, 1830), in various seawater pH treatments analogous to future ocean scenarios in a 3x-replicated experimental design. Upon settlement, we removed all otoliths from each individual fish and analyzed them for treatment effects on morphometrics including area, perimeter, and circularity; further, we used scanning electron microscopy to screen otoliths visually for evidence of treatment effects on lateral development, surface roughness, and vaterite replacement. Our results corroborate those of other experiments with other taxa that observed otolith growth with elevated pCO2, and provide evidence that lateral development and surface roughness increased as well; we observed at least one of these effects in all otolith types. Finally, we review previous work investigating ocean acidification impacts on otolith morphology and hypotheses concerning function, placing our observations in context. These impacts may have consequences teleost fitness in the near-future ocean.

Continue reading ‘Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)’

Juvenile rockfish show resilience to CO2-acidification and hypoxia across multiple biological scales

California’s coastal ecosystems are forecasted to undergo shifting ocean conditions due to climate change, some of which may negatively impact recreational and commercial fish populations. To understand if fish populations have the capacity to respond to multiple stressors, it is critical to examine interactive effects across multiple biological scales, from cellular metabolism to species interactions. This study examined the effects of CO2-acidification and hypoxia on two naturally co-occurring species, juvenile rockfish (genus Sebastes) and a known predator, cabezon (Scorpaenichthys marmoratus). Fishes were exposed to two PCO2 levels at two dissolved oxygen (DO) levels: ~600 (ambient) and ~1600 (high) μatm PCO2 and 8.0 (normoxic) and 4.5 mg l−1 DO (hypoxic) and assessments of cellular metabolism, prey behavior and predation mortality rates were quantified after 1 and 3 weeks. Physiologically, rockfish showed acute alterations in cellular metabolic enzyme activity after 1 week of acclimation to elevated PCO2 and hypoxia that were not evident in cabezon. Alterations in rockfish energy metabolism were driven by increases in anaerobic LDH activity, and adjustments in enzyme activity ratios of cytochrome c oxidase and citrate synthase and LDH:CS. Correlated changes in rockfish behavior were also apparent after 1 week of acclimation to elevated PCO2 and hypoxia. Exploration behavior increased in rockfish exposed to elevated PCO2 and spatial analysis of activity indicated short-term interference with anti-predator responses. Predation rate after 1 week increased with elevated PCO2; however, no mortality was observed under the multiple-stressor treatment suggesting negative effects on cabezon predators. Most noteworthy, metabolic and behavioral changes were moderately compensated after 3 weeks of acclimation, and predation mortality rates also decreased suggesting that these rockfish may be resilient to changes in environmental stressors predicted by climate models. Linking physiological and behavioral responses to multiple stressors is vital to understand impacts on populations and community dynamics.

Continue reading ‘Juvenile rockfish show resilience to CO2-acidification and hypoxia across multiple biological scales’

Effects of high pCO2 on the northern krill Thysanoessa inermis in relation to carbonate chemistry of its collection area, Rijpfjorden

Polar oceans are predicted to be the first marine environments affected by ocean acidification (OA). Thysanoessa inermis is one of the most abundant krill species in northern waters of the Atlantic and a key species in the food web of this ecosystem. Yet, we know very little about potential OA effects on this species. We studied the effects of elevated pCO2 on T. inermis in a laboratory experiment by exposing individuals for 11 weeks to low and high pCO2 (450 and 1200 µatm, respectively, n = 12 per pCO2 treatment). Survival, growth, and moulting frequency was monitored during the experiment, and feeding and oxygen consumption rates (n = 3–5 per pCO2 treatment) were measured at the end of the experiment. No significant effects of high pCO2 on survival, growth, moulting, oxygen consumption, and feeding rate were observed, indicating that T. inermis is tolerant to predicted high OA levels. We also explored physical and chemical properties of waters near the collection area of krill, Rijpfjorden (Svalbard 80° North) during the polar summer (July–August). In situ measurements showed large temperature and salinity gradients from surface to bottom and pCO2 and pH ranged, respectively, 161–417 µatm and 7.99–8.37. Even though substantial spatial variability in pCO2 could be observed, krill in this area is not confronted yet with the investigated high pCO2 levels.

Continue reading ‘Effects of high pCO2 on the northern krill Thysanoessa inermis in relation to carbonate chemistry of its collection area, Rijpfjorden’

High pCO2 levels affect metabolic rate, but not feeding behavior and fitness, of farmed giant mussel Choromytilus chorus

Benthic habitats such as intertidal areas, sandy or rocky shores, upwelling zones, and estuaries are characterized by variable environmental conditions. This high variability of environmental stressors such as temperature, salinity, and pH/ pCO2 levels have been shown to impose restrictions on organismal performance. The giant mussel Choromytilus chorus forms intertidal and subtidal mussel beds in estuarine zones associated with fjords occurring in southern Chile and is an important aquacultural resource in Patagonia. In this study, we estimated the sensitivity of physiological traits and energy balance of C. chorus juveniles exposed to 3 pCO2 treatments (500, 750, and 1200 µatm) for 30 d. Results showed that in acidified, high pCO2 conditions, C. chorus juveniles had increased metabolic rates; however, other physiological traits (clearance and ingestion rates, ammonia excretion, absorption efficiency, growth rate, biomass production, net calcification, and dissolution rates) were not affected. These results suggest that when subjected to acidification, the adaptive response of C. chorus triggers tradeoffs among physiological traits that favor sustained feeding and growth in order to combat increased metabolic stress. As has been reported for other marine organisms, chronic exposure to variable pH/ pCO2 in their native habitats, such as estuarine zones, could explain the differential acclimatization capacity of giant mussels to cope with the increase in pCO2. Additionally, the fact that the mussels did not suffer from mortality indicates that increased pCO2 levels may have chronic, but not lethal, effects on this species under these experimental conditions.

Continue reading ‘High pCO2 levels affect metabolic rate, but not feeding behavior and fitness, of farmed giant mussel Choromytilus chorus’

Effect of carbon dioxide-induced water acidification and seasonality on the physiology of the sea-bob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae)

Climate changes are altering the chemistry of the oceans, and knowing their effects on the biology of animals is urgent. Since the physiological responses of crustaceans may be different given the seasons of the year, this work evaluated the synergistic effect of ocean acidification and seasonality on the physiology of the sea-bob shrimp, Xiphopenaeus kroyeri. Experimental groups were exposed for 5 days to two levels of pH, representing present-day mean ambient conditions (pH 8.0) and distant-future conditions (pH 7.3) during the summer and winter. Metabolism, nitrogen excretion, energy type and storage were determined, respectively, by oxygen consumption, ammonia excretion, atomic ratio O/N and hepatosomatic index. The reduction of pH resulted in a decrease of about 30% in the X. kroyeri metabolism during the summer and winter. Nitrogen excretion (reduction of 40%) and hepatosomatic index (increase of 120%) showed to be altered in animals exposed to reduced pH only throughout summer. Regardless of pH and seasons of the year, animals use mainly proteins as energy substrate and they do not show mortality. The increase of the hepatosomatic index, indicator of the accumulation of energy reserves, associated with metabolism reduction, suggests the suppression of activities that demand energy expenditure. The consequences of the physiological alterations observed may include decreases in growth and reproduction rate and displacement of populations to more appropriate conditions. The results might be associated with a set of factors resulting from the exposure to reduced pH, the synergy between pH and temperature, but also with a pattern of different physiological responses that may occur according to seasonality.

Continue reading ‘Effect of carbon dioxide-induced water acidification and seasonality on the physiology of the sea-bob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae)’

Physiological resilience of a temperate soft coral to ocean warming and acidification

Atmospheric concentration of carbon dioxide (CO 2 ) is increasing at an unprecedented rate and subsequently leading to ocean acidification. Concomitantly, ocean warming is intensifying, leading to serious and predictable biological impairments over marine biota. Reef-building corals have proven to be very vulnerable to climate change, but little is known about the resilience of non-reef-building species. In this study, we investigated the effects of ocean warming and acidification on the antioxidant enzyme activity (CAT—catalase, and GST—glutathione S-transferase), lipid peroxidation (using malondialdehyde, MDA—levels as a biomarker) and heat shock response (HSP70/HSC70 content) of the octocoral Veretillum cynomorium. After 60 days of acclimation, no mortalities were registered in all treatments. Moreover, CAT and GST activities, as well as MDA levels, did not change significantly under warming and/or acidification. Heat shock response was significantly enhanced under warming, but high CO2 did not have a significant effect. Contrasting to many of their tropical coral-reef relatives, our findings suggest that temperate shallow-living octocorals may be able to physiologically withstand future conditions of increased temperature and acidification.

Continue reading ‘Physiological resilience of a temperate soft coral to ocean warming and acidification’

Effects of ocean acidification and salinity variations on the physiology of osmoregulating and osmoconforming crustaceans

Survival, osmoregulatory pattern, oxygen consumption, energy spent on metabolism, ammonia excretion, type of oxidized energy substrate, and hepatosomatic index were evaluated in decapods (an osmoregulating crab, Callinectes danae, and an osmoconforming seabob shrimp, Xiphopenaeus kroyeri) exposed to carbon dioxide-induced water acidification (pH 7.3, control pH 8.0) and different salinities (20, 25, 30, 35, and 40‰) for 3 days. Compared to the animals kept at controlled pH, exposure to reduced pH resulted in the loss of osmoregulatory capacity in C. danae at all salinities, except for some hyporegulation at 40‰, and reduced oxygen consumption and ammonia excretion at 20 and 40‰. Xiphopenaeus kroyeri remained an osmoconformer in all evaluated conditions, except for some hyporegulation at 40‰, and when exposed to the reduced pH, it presented changes in oxygen consumption at all salinities and reductions in ammonia excretion at 20 and 35‰ compared to the control animals. Both species use protein as the main energy substrate and decrease the hepatosomatic index when exposed to reduced pH relative to the control. The observed changes may be associated with changes in the activity of enzymes related to osmoregulation, the use of amino acids as osmotic effectors of cell volume control and recovery, and the Bohr effect, and, because the gills are multifunctional organs related to osmoregulation, the changes may be related to acid–base control, nitrogen excretion, and respiration, with a change in one of these functions bringing about changes in the others.

Continue reading ‘Effects of ocean acidification and salinity variations on the physiology of osmoregulating and osmoconforming crustaceans’

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Ocean acidification in the IPCC AR5 WG II

OUP book