Posts Tagged 'temperature'

Southern Ocean pteropods at risk from ocean warming and acidification

Early life stages of marine calcifiers are particularly vulnerable to climate change. In the Southern Ocean aragonite undersaturation events and areas of rapid warming already occur and are predicted to increase in extent. Here, we present the first study to successfully hatch the polar pteropod Limacina helicina antarctica and observe the potential impact of exposure to increased temperature and aragonite undersaturation resulting from ocean acidification (OA) on the early life stage survival and shell morphology. High larval mortality (up to 39%) was observed in individuals exposed to perturbed conditions. Warming and OA induced extensive shell malformation and dissolution, respectively, increasing shell fragility. Furthermore, shell growth decreased, with variation between treatments and exposure time. Our results demonstrate that short-term exposure through passing through hotspots of OA and warming poses a serious threat to pteropod recruitment and long-term population viability.

Continue reading ‘Southern Ocean pteropods at risk from ocean warming and acidification’

Competitive interactions moderate the effects of elevated temperature and atmospheric CO2 on the health and functioning of oysters

Global increases in sea temperatures and atmospheric concentrations of CO2 may affect the health of calcifying shellfish. Little is known, however, about how competitive interactions within and between species may influence how species respond to multiple stressors. We experimentally assessed separate and combined effects of temperature (12 or 16°C) and atmospheric CO2 concentrations (400 and 1000 ppm) on the health and biological functioning of native (Ostrea edulis) and invasive (Crassostrea gigas) oysters held alone and in intraspecific or interspecific mixtures. We found evidence of reduced phagocytosis under elevated CO2 and, when combined with increased temperature, a reduction in the number of circulating haemocytes. Generally, C. gigas showed lower respiration rates relative to O. edulis when the species were in intraspecific or interspecific mixtures. In contrast, O. edulis showed a higher respiration rate relative to C. gigas when held in an interspecific mixture and exhibited lower clearance rates when held in intraspecific or interspecific mixtures. Overall, clearance rates of C. gigas were consistently greater than those of O. edulis. Collectively, our findings indicate that a species’ ability to adapt metabolic processes to environmental conditions can be modified by biotic context and may make some species (here, C. gigas) competitively superior and less vulnerable to future climatic scenarios at local scales. If these conclusions are generic, the relative role of species interactions, and other biotic parameters, in altering the outcomes of climate change will require much greater research emphasis.

Continue reading ‘Competitive interactions moderate the effects of elevated temperature and atmospheric CO2 on the health and functioning of oysters’

Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)

Highlights

• Atmospheric and water conditions/contaminants influence animal physiology status.
• Scarcely studied multi-stressor effects were extricated via full-factorial design.
• Warming stimulated mercury accumulation, but was offset by acidification.
• Co-occurring acidification countered oxidative stress elicited by other stressors.
• Enhanced mitigation pathways or chemical dynamics may underpin stressor antagonism.

Abstract

Increases in carbon dioxide (CO2) and other greenhouse gases emissions are changing ocean temperature and carbonate chemistry (warming and acidification, respectively). Moreover, the simultaneous occurrence of highly toxic and persistent contaminants, such as methylmercury, will play a key role in further shaping the ecophysiology of marine organisms. Despite recent studies reporting mostly additive interactions between contaminant and climate change effects, the consequences of multi-stressor exposure are still largely unknown. Here we disentangled how Argyrosomus regius physiology will be affected by future stressors, by analysing organ-dependent mercury (Hg) accumulation (gills, liver and muscle) within isolated/combined warming (ΔT = 4 °C) and acidification (ΔpCO2 = 1100 μatm) scenarios, as well as direct deleterious effects and phenotypic stress response over multi-stressor contexts. After 30 days of exposure, although no mortalities were observed in any treatments, Hg concentration was enhanced under warming conditions, especially in the liver. On the other hand, elevated CO2 decreased Hg accumulation and consistently elicited a dampening effect on warming and contamination-elicited oxidative stress (catalase, superoxide dismutase and glutathione-S-transferase activities) and heat shock responses. Thus, potentially unpinned on CO2-promoted protein removal and ionic equilibrium between hydrogen and reactive oxygen species, we found that co-occurring acidification decreased heavy metal accumulation and contributed to physiological homeostasis. Although this indicates that fish can be physiologically capable of withstanding future ocean conditions, additional experiments are needed to fully understand the biochemical repercussions of interactive stressors (additive, synergistic or antagonistic).

Continue reading ‘Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)’

Effects of pH and temperature on egg hatching success of the marine planktonic copepod, Calanus finmarchicus

Calanus finmarchicus is a predominant planktonic copepod in the northern North Atlantic Ocean, where it is a fundamental link in the transfer of energy from phytoplankton to fish. Here, we investigate whether ocean acidification at present-day and future levels will cause a significant decrease in the egg hatching success (HS) of C. finmarchicus in the Gulf of Maine. Eggs spawned by female C. finmarchicus collected from the coastal Gulf of Maine were incubated in seawater acidified by addition of CO2 to selected pH levels at 3.5 °C (in a single experiment), 6 °C and 14–15 °C (in multiple experiments). HS was unaffected by pH between 6.58 and 8.0 at 3.5 and 6 °C, and between 7.1 and 8.0 when incubated at 15 °C. A significant interactive effect between temperature and pH on HS was found using a two-way ANOVA of the data from experiments at 6 °C and 14–15 °C, temperatures that are experienced in summer in the Gulf of Maine. HS of eggs spawned from C. finmarchicus females immediately after capture from a coastal station was significantly reduced at pH ≤ 7.0 when incubated at 14–15 °C, although HS of eggs collected from well-fed females in the laboratory in water from the Damariscotta Estuary was not significantly reduced at pH levels as low as 6.6 at 15 °C. This finding is consistent with the hypothesis that parental history and possibly maternal provisioning can influence capability of eggs to adjust to lower pH environments. While an interaction between pH and temperatures experienced by C. finmarchicus at the southern edge of its biogeographic range was observed, the pH at which this interaction occurred is substantially lower than pH levels predicted for the surface ocean over the surface ocean.

Continue reading ‘Effects of pH and temperature on egg hatching success of the marine planktonic copepod, Calanus finmarchicus’

Reproductive and trans-generational effect of ocean acidification and warming on the coral Stylophora pistillata in the Gulf of Aqaba

Global warming is threatening 75 % of the world’s coral reefs. The reproduction of corals is a driver for the development of the whole reef ecosystem. Then, it is essential to better understand the transgenerational mechanisms in the response of parents and offspring to elevated temperature and lowered pH. Colonies of Stylophora pistillata from the Gulf of Aqaba during their reproduction period were exposed to a 4°C increase in temperature and a pH of 7.6 for 36 days, then a 6°C increase for six days. Planulae were counted on seven consecutive nights, two times during the experiment period. Physiological characteristics of adult and planulae were assessed on four and five sampling points respectively, as well as the behaviour of the planulae through their incubation. Results show no effect of OWA on the reproduction, parents, and planulae physiology. They suggest that the natural resistance of corals in the Gulf of Aqaba is transmitted from parent to offspring. Data on planulae quantity, survival, settlement, and metabolism provides additional and useful information to understand the biology of this coral, specially in its early-life stage. This study’s outcome is adding evidences of the future development of corals reefs in this region, unlike several other tropical reefs in the world.

Continue reading ‘Reproductive and trans-generational effect of ocean acidification and warming on the coral Stylophora pistillata in the Gulf of Aqaba’

Dietary Zn and the subsequent organotropism in fish: no influence of food quality, frequency of feeding and environmental conditions (pH and temperature)

Trophic transfer of Zn in fish is affected by the type of food and environmental variables such as temperature. However, there is still a lack of knowledge regarding the effects of such factors on Zn organotropism. For this reason, a series of experimental studies have investigated how the distribution and the concentration of Zn is affected by some environmentally-relevant factors (food quality, food availability, water pH, and temperature) in turbot Scophthalmus maximus using radiotracer techniques. In three different experiments, Zn distribution in seven body compartments of juvenile turbot and the calculation of Zn concentration index (IC) for each compartment were compared. Its distribution as well as its concentration in the body compartments of juvenile turbots were not affected by the experimental conditions tested. This apparent consistency in the Zn organotropism can be explained by the ability of the fish to maintain Zn homeostasis at non-toxic Zn concentrations in their diet. These results are important to better understand the trophic transfer of Zn in fish under realistic environmental conditions.

Continue reading ‘Dietary Zn and the subsequent organotropism in fish: no influence of food quality, frequency of feeding and environmental conditions (pH and temperature)’

Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage

In future global change scenarios the surface ocean will experience continuous acidification and rising temperatures. While effects of both stressors on marine, benthic communities are fairly well studied, consequences of the interaction of both factors remain largely unknown. We performed a short-term microcosm experiment exposing a soft-bottom community from an intertidal flat in the Westerscheldt estuary to two levels of seawater pH (ambient pHT = 7.9, reduced pHT = 7.5) and temperature (10 °C ambient and 13 °C elevated temperature) in a crossed design. After 8 weeks, meiobenthic community structure and nematode staining ratios, as a proxy for mortality, were compared between treatments and structural changes were related to the prevailing abiotic conditions in the respective treatments (pore water pHT, sediment grain size, total organic matter content, total organic carbon and nitrogen content, phytopigment concentrations and carbonate concentration). Pore water pHT profiles were significantly altered by pH and temperature manipulations and the combination of elevated temperature and reduced pH intensified the already more acidic porewater below the oxic zone. Meiofauna community composition was significantly affected by the combination of reduced pH and elevated temperature resulting in increased densities of predatory Platyhelminthes, reduced densities of Copepoda and Nauplii and complete absence of Gastrotricha compared to the experimental control. Furthermore, nematode staining ratio was elevated when seawater pH was reduced pointing towards reduced degradation rates of dead nematode bodies. The observed synergistic interactions of pH and temperature on meiobenthic communities and abiotic sediment characteristics underline the importance of multistressor experiments when addressing impacts of global change on the marine environment.

Continue reading ‘Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage’


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Ocean acidification in the IPCC AR5 WG II

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