Posts Tagged 'multiple factors'

Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors

While early life-stage marine bivalves are vulnerable to ocean acidification, effects over successive generations are poorly characterized. The objective of this work was to assess the transgenerational effects of ocean acidification on two species of North Atlantic bivalve shellfish, Mercenaria mercenaria and Argopecten irradians. Adults of both species were subjected to high and low pCO2 conditions during gametogenesis. Resultant larvae were exposed to low and ambient pH conditions in addition to multiple, additional stressors including thermal stress, food-limitation, and exposure to a harmful alga. There were no indications of transgenerational acclimation to ocean acidification during experiments. Offspring of elevated pCO2-treatment adults were significantly more vulnerable to acidification as well as the additional stressors. Our results suggest that clams and scallops are unlikely to acclimate to ocean acidification over short time scales and that as coastal oceans continue to acidify, negative effects on these populations may become compounded and more severe.

Continue reading ‘Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors’

Sponge bioerosion on changing reefs: ocean warming poses physiological constraints to the success of a photosymbiotic excavating sponge

Excavating sponges are prominent bioeroders on coral reefs that in comparison to other benthic organisms may suffer less or may even benefit from warmer, more acidic and more eutrophic waters. Here, the photosymbiotic excavating sponge Cliona orientalis from the Great Barrier Reef was subjected to a prolonged simulation of both global and local environmental change: future seawater temperature, partial pressure of carbon dioxide (as for 2100 summer conditions under “business-as-usual” emissions), and diet supplementation with particulate organics. The individual and combined effects of the three factors on the bioerosion rates, metabolic oxygen and carbon flux, biomass change and survival of the sponge were monitored over the height of summer. Diet supplementation accelerated bioerosion rates. Acidification alone did not have a strong effect on total bioerosion or survival rates, yet it co-occurred with reduced heterotrophy. Warming above 30 °C (+2.7 °C above the local maximum monthly mean) caused extensive bleaching, lower bioerosion, and prevailing mortality, overriding the other factors and suggesting a strong metabolic dependence of the sponge on its resident symbionts. The growth, bioerosion capacity and likelihood of survival of C. orientalis and similar photosymbiotic excavating sponges could be substantially reduced rather than increased on end-of-the-century reefs under “business-as-usual” emission profiles.

Continue reading ‘Sponge bioerosion on changing reefs: ocean warming poses physiological constraints to the success of a photosymbiotic excavating sponge’

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios

Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios’

Divergent responses in growth and nutritional quality of coastal macroalgae to the combination of increased pCO2 and nutrients

Highlights

  • Growth rates and tissue quality of two common macroalgal species were assessed under conditions of high pCO2 and nutrient loading under monoculture and biculture.
  • Ephemeral macroalgae exhibited significant increases in growth under high pCO2 and high nutrients.
  • Growth rates of perennial macroalgae were unaffected by environmental treatments.
  • Tissue quality of both species increased via decreases in C:N when nutrients were increased.
  • Biculture appears to impact resource acquisition of perennial macroalgae as evidence of higher tissue C:N when compared to monoculture tissue.

Abstract

Coastal ecosystems are subjected to global and local environmental stressors, including increased atmospheric carbon dioxide (CO2) (and subsequent ocean acidification) and nutrient loading. Here, we tested how two common macroalgal species in the Northwest Atlantic (Ulva spp. and Fucus vesiculosus Linneaus) respond to the combination of increased CO2 and nutrient loading. We utilized two levels of pCO2 with two levels of nutrients in a full factorial design, testing the growth rates and tissue quality of Ulva and Fucus grown for 21 days in monoculture and biculture. We found that the opportunistic, fast-growing Ulva exhibited increased growth rates under high pCO2 and high nutrients, with growth rates increasing three-fold above Ulva grown in ambient pCO2 and ambient nutrients. By contrast, Fucus growth rates were not impacted by either environmental factor. Both species exhibited a decline in carbon to nitrogen ratios (C:N) with elevated nutrients, but pCO2 concentration did not alter tissue quality in either species. Species grown in biculture exhibited similar growth rates to those in monoculture conditions, but Fucus C:N increased significantly when grown with Ulva, indicating an effect of the presence of Ulva on Fucus. Our results suggest that the combination of ocean acidification and nutrients will enhance abundance of opportunistic algal species in coastal systems and will likely drive macroalgal community shifts, based on species-specific responses to future conditions.

Continue reading ‘Divergent responses in growth and nutritional quality of coastal macroalgae to the combination of increased pCO2 and nutrients’

Metabolic response and thermal tolerance of green abalone juveniles (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia

Highlights

  • Assessment of the impacts of hypoxia and hypercapnia on thermal tolerance
  • Hypoxia induced a downshift in critical temperature.
  • Hypercapnia did not affect thermal tolerance.
  • Both drivers combined prompted a stronger narrowing of thermal tolerance.
  • Warming stress induced protein degradation under all experimental conditions.


Abstract

With ongoing climate change, rising ocean temperature is usually accompanied by falling oxygen levels (hypoxia) and increasing CO2 concentration (hypercapnia). Both drivers may impose constraints on physiological mechanisms that define thermal limits resulting in increased vulnerability towards warming in marine ectotherms. The present study aimed to detect differences in thermal tolerance by investigating the underlying metabolic responses in the green abalone (Haliotis fulgens) under conditions of hypoxia and hypercapnia. Juvenile abalones were exposed to a temperature ramp (+ 3 °C day− 1) under hypoxia (50% air saturation) and hypercapnia (~ 1000 μatm pCO2), both individually and in combination. Impacts on energy metabolism were assessed by analyzing whole animal respiration rates and metabolic profiles of gills and hepatopancreas via 1H NMR spectroscopy. While hypercapnia had a minor impact on the results of the temperature treatment, hypoxia strongly increased the vulnerability to warming, indicated by respiration rates falling below values expected from an exponential increase and by the onset of anaerobic metabolism suggesting a downward shift of the upper critical temperature. Warming under combined hypoxia and hypercapnia elicited a severe change in metabolism involving a strong accumulation of amino acids, osmolytes and anaerobic end products at intermediate temperatures, followed by declining concentrations at warmer temperatures. This matched the limited capacity to increase metabolic rate, loss of attachment and mortality observed under these conditions suggesting a strong narrowing of the thermal window. In all cases, the accumulation of free amino acids identified proteins as a significant energy source during warming stress.

Continue reading ‘Metabolic response and thermal tolerance of green abalone juveniles (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia’

Low recruitment due to altered settlement substrata as primary constraint for coral communities under ocean acidification

The future of coral reefs under increasing CO2 depends on their capacity to recover from disturbances. To predict the recovery potential of coral communities that are fully acclimatized to elevated CO2, we compared the relative success of coral recruitment and later life stages at two volcanic CO2 seeps and adjacent control sites in Papua New Guinea. Our field experiments showed that the effects of ocean acidification (OA) on coral recruitment rates were up to an order of magnitude greater than the effects on the survival and growth of established corals. Settlement rates, recruit and juvenile densities were best predicted by the presence of crustose coralline algae, as opposed to the direct effects of seawater CO2. Offspring from high CO2 acclimatized parents had similarly impaired settlement rates as offspring from control parents. For most coral taxa, field data showed no evidence of cumulative and compounding detrimental effects of high CO2 on successive life stages, and three taxa showed improved adult performance at high CO2 that compensated for their low recruitment rates. Our data suggest that severely declining capacity for reefs to recover, due to altered settlement substrata and reduced coral recruitment, is likely to become a dominant mechanism of how OA will alter coral reefs.

Continue reading ‘Low recruitment due to altered settlement substrata as primary constraint for coral communities under ocean acidification’

The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages

Highlights

  • Higher seawater temperature did not effect meiofaunal abundance.
  • Lower seawater pH did reduce meiofaunal abundance and species richness.
  • Nematode assemblages showed increased dominance under a future OW/OA scenario.


Abstract

Climate change due to increased anthropogenic CO2 in the atmosphere is causing an increase in seawater temperatures referred to as ocean warming and a decrease in seawater pH, referred to as ocean acidification. The meiofauna play an important role in the ecology of marine ecosystems and the functions they provide. Using microcosms, meiofaunal assemblages were exposed to two temperatures (15 and 19 °C) and two pHs (pCO2 of 400 and 1000 ppm), both individually and in combination, for a period of 90 days. The hypothesis that increased temperature will increase meiofaunal abundance was not supported. The hypothesis that a reduced pH will reduce meiofaunal abundance and species richness was supported. The combination of future conditions of temperature and pH (19 °C and pCO2 of 1000 ppm) did not affect overall abundance but the structure of the nematode assemblage changed becoming dominated by a few opportunistic species.

Continue reading ‘The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages’


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Ocean acidification in the IPCC AR5 WG II

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