Posts Tagged 'mortality'

Investigating the collective effect of two ocean acidification adaptation strategies on juvenile clams (Venerupis philippinarum)

Anthropogenic CO2 emissions have altered Earth’s climate system at an unprecedented rate, causing global climate change and ocean acidification. Surface ocean pH has increased by 26% since the industrial era and is predicted to increase another 100% by 2100. Additional stress from abrupt changes in carbonate chemistry in conjunction with other natural and anthropogenic impacts may push populations over critical thresholds. Bivalves are particularly vulnerable to the impacts of acidification during early life-history stages. Two substrate additives, shell hash and macrophytes, have been proposed as potential ocean acidification adaptation strategies for bivalves but there is limited research into their effectiveness. This study uses a split plot design to examine four different combinations of the two substratum treatments on juvenile Venerupis philippinarum settlement, survival, and growth and on local water chemistry at Fidalgo Bay and Skokomish Delta, Washington. Results show no macrophyte or shell hash treatment effect on V. philippinarum settlement or survival. A significant macrophyte treatment effect was detected on clam growth, with mean length higher when macrophytes were absent regardless of the presence or absence of shell hash. Additionally, the macrophyte treatment appeared to have an opposite effect on pH than was anticipated, where pH was higher outside of macrophyte beds than inside. Although these results do not support the use of either treatment as an ocean acidification adaptation strategy, the mixed results reported in the literature for both treatments highlight the nascent nature of this research. As atmospheric CO2 concentrations continue to increase, there is an exigent need for additional studies to determine the specific conditions under which these strategies might help produce conditions conducive to settlement, growth, and survival of bivalves and other calcifying organisms. Such research could help guide local adaptation actions, especially among resource-dependent communities that rely on sustainable fisheries for their health and well-being.

Continue reading ‘Investigating the collective effect of two ocean acidification adaptation strategies on juvenile clams (Venerupis philippinarum)’

Impact of climate change on the ontogenetic development of ‘solar-powered’ sea slugs

Solar-powered animals are particularly susceptible to climate change because photosynthesis brings major risks to animals under environmental stress. Although some groups have been widely studied (e.g. corals), little information is available on how other less charismatic photosynthetic animals (e.g. sea slugs) will respond to future ocean conditions. This study is the first to evaluate the impact of future ocean conditions on the fitness of tropical photosynthetic sacoglossan sea slugs throughout different life stages. Adults of Elysia clarki were exposed (30 d) to conditions simulating present-day and predicted scenarios of ocean acidification (ΔpH = 0.4) and warming (+4°C). Egg masses were incubated under the same conditions as adult broodstock until 15 d after metamorphosis. Exposure to ocean acidification and warming scenarios led to a significant decrease in the number of spawned egg masses and in their membrane thickness. Moreover, a significant decrease in the volume of embryo capsules was accompanied by an increase in embryo volume. These findings suggest that sea slugs shifted their energy allocation towards embryo quality rather than to structures that confer protection from environmental challenges. Climate change-related stress significantly reduced the survival and length of veligers and increased the incidence of deformities, but did not affect chloroplast acquisition by juvenile slugs. The lower reproductive output of adults and the adverse impacts on early life stages recorded under future ocean conditions allows us to anticipate negative consequences for the recruitment of these sea slugs’ populations in the oceans of tomorrow.

Continue reading ‘Impact of climate change on the ontogenetic development of ‘solar-powered’ sea slugs’

Resilience of the larval slipper limpet Crepidula onyx to direct and indirect-diet effects of ocean acidification

Ocean acidification (OA) is known to directly impact larval physiology and development of many marine organisms. OA also affects the nutritional quality and palatability of algae, which are principal food sources for many types of planktonic larvae. This potential indirect effect of OA via trophic interactions, however, has not been fully explored. In this study, veligers of Crepidula onyx were exposed to different pH levels representing the ambient (as control) and low pH values (pH 7.7 and pH 7.3) for 14 days, and were fed with Isochrysis galbana cultured at these three respective pHs. pH, diet, nor their interactions had no effect on larval mortality. Decrease in pH alone had a significant effect on growth rate and shell size. Structural changes (increased porosity) in larval shells were also observed in the low pH treatments. Interactions between acidification and reduced diet quality promoted earlier settlement. Unlike other calcifying molluscs, this population of slipper limpets introduced to Hong Kong in 1960s appeared to be resilient to OA and decreased algal nutritional value. If this robustness observed in the laboratory applies to the field, competition with native invertebrates may intensify and this non-native snail could flourish in acidified coastal ecosystems.

Continue reading ‘Resilience of the larval slipper limpet Crepidula onyx to direct and indirect-diet effects of ocean acidification’

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’

Future marine ecosystem drivers, biodiversity, and fisheries maximum catch potential in Pacific Island countries and territories under climate change

Highlights

  • Under the RCP 8.5 scenario, tropical Pacific temperature will rise by ≥ 3 °C by 2100.
  • This is accompanied by declines in dissolved oxygen, pH, and net primary production.
  • This will lead to local extinctions of up to 80% of marine species in some regions.
  • 9 of 17 Pacific Island entities experience ≥ 50% declines in maximum catch potential.
  • Impacts can be greatly reduced by mitigation measures under the RCP 2.6 scenario.


Abstract

The increase in anthropogenic CO2 emissions over the last century has modified oceanic conditions, affecting marine ecosystems and the goods and services that they provide to society. Pacific Island countries and territories are highly vulnerable to these changes because of their strong dependence on ocean resources, high level of exposure to climate effects, and low adaptive capacity. Projections of mid-to-late 21st century changes in sea surface temperature (SST), dissolved oxygen, pH, and net primary productivity (NPP) were synthesized across the tropical Western Pacific under strong climate mitigation and business-as-usual scenarios. These projections were used to model impacts on marine biodiversity and potential fisheries catches. Results were consistent across three climate models, indicating that SST will rise by ≥ 3 °C, surface dissolved oxygen will decline by ≥ 0.01 ml L−1, pH will drop by ≥ 0.3, and NPP will decrease by 0.5 g m−2 d−1 across much of the region by 2100 under the business-as-usual scenario. These changes were associated with rates of local species extinction of > 50% in many regions as fishes and invertebrates decreased in abundance or migrated to regions with conditions more suitable to their bio-climate envelope. Maximum potential catch (MCP) was projected to decrease by > 50% across many areas, with the largest impacts in the western Pacific warm pool. Climate change scenarios that included strong mitigation resulted in substantial reductions of MCP losses, with the area where MCP losses exceeded 50% reduced from 74.4% of the region under business-as-usual to 36.0% of the region under the strong mitigation scenario.

Continue reading ‘Future marine ecosystem drivers, biodiversity, and fisheries maximum catch potential in Pacific Island countries and territories under climate change’

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’


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Ocean acidification in the IPCC AR5 WG II

OUP book