Posts Tagged 'mortality'

Photosynthesis and mineralogy of Jania rubens at low pH/high pCO2: a future perspective

Highlights

• Calcifying red algae may show species-specific response to ocean acidification (OA).
• Photosynthesis and mineralogy (biosphere) were assessed after a three-week transplant.
• Field carbon chemistry (hydrosphere) and irradiance (atmosphere) were also considered.
• Photosynthesis decreased while calcification was maintained under future pH conditions.
• The calcifying Jania rubens may survive but reducing the fitness under OA.

Abstract

Corallinales (Rhodophyta) are high Mg-calcite macroalgae and are considered among the most vulnerable organisms to ocean acidification (OA). These sensitive species play fundamental roles in coastal systems as food source and settlement promoters as well as being involved in reef stabilization, and water carbonate balance. At present only a few studies are focused on erect calcifying macroalgae under low pH/high pCO2 and the contrasting results make difficult to predict the ecological consequences of the OA on the coralline algae. In this paper the physiological reasons behind the resistance of Jania rubens, one of the most common calcareous species, to changing ocean pH are analysed. In particular, we studied the photosynthetic and mineralogical response of J. rubens after a three-week transplant in a natural CO2 vent system. The overall results showed that J. rubens could be able to survive under predicted pH conditions even though with a reduced fitness; nevertheless physiological limits prevent the growth and survival of the species at pH 6.7. At low pH (i.e. pH 7.5), the maximum and effective PSII efficiency decreased even if the increase of Rubisco expression suggests a compensation effort of the species to cope with the decreased light-driven products. In these circumstances, a pH-driven bleaching phenomenon was also observed. Even though the photosynthesis decreased at low pH, J. rubens maintained unchanged the mineralogical composition and the carbonate content in the cell wall, suggesting that the calcification process may also have a physiological relevance in addition to a structural and/or a protective role. Further studies will confirm the hypotheses on the functional and evolutionary role of the calcification process in coralline algae and on the ecological consequences of the community composition changes under high pCO2 oceans.

Continue reading ‘Photosynthesis and mineralogy of Jania rubens at low pH/high pCO2: a future perspective’

Ocean acidification but not warming alters sex determination in the Sydney rock oyster, Saccostrea glomerata

Whether sex determination of marine organisms can be altered by ocean acidification and warming during this century remains a significant, unanswered question. Here, we show that exposure of the protandric hermaphrodite oyster, Saccostrea glomerata to ocean acidification, but not warming, alters sex determination resulting in changes in sex ratios. After just one reproductive cycle there were 16% more females than males. The rate of gametogenesis, gonad area, fecundity, shell length, extracellular pH and survival decreased in response to ocean acidification. Warming as a sole stressor slightly increased the rate of gametogenesis, gonad area and fecundity, but this increase was masked by the impact of ocean acidification at a level predicted for this century. Alterations to sex determination, sex ratios and reproductive capacity will have flow on effects to reduce larval supply and population size of oysters and potentially other marine organisms.

Continue reading ‘Ocean acidification but not warming alters sex determination in the Sydney rock oyster, Saccostrea glomerata’

Long-term exposure to acidification disrupts reproduction in a marine invertebrate

Climate change research is advancing to more complex and more comprehensive studies that include long-term experiments, multiple life-history stages, multi-population, and multi-trait approaches. We used a population of the barnacle Balanus improvisus known to be sensitive to short-term acidification to determine its potential for long-term acclimation to acidification. We reared laboratory-bred individuals (as singles or pairs), and field-collected assemblages of barnacles, at pH 8.1 and 7.5 (≈ 400 and 1600 μatm pCO2 respectively) for up to 16 months. Acidification caused strong mortality and reduced growth rates. Acidification suppressed respiration rates and induced a higher feeding activity of barnacles after 6 months, but this suppression of respiration rate was absent after 15 months. Laboratory-bred barnacles developed mature gonads only when they were held in pairs, but nonetheless failed to produce fertilized embryos. Field-collected barnacles reared in the laboratory for 8 months at the same pH’s developed mature gonads, but only those in pH 8.1 produced viable embryos and larvae. Because survivors of long-term acidification were not capable of reproducing, this demonstrates that B. improvisus can only partially acclimate to long-term acidification. This represents a clear and significant bottleneck in the ontogeny of this barnacle population that may limit its potential to persist in a future ocean.

Continue reading ‘Long-term exposure to acidification disrupts reproduction in a marine invertebrate’

Physiological stress response associated with elevated CO2 and dissolved iron in a phytoplankton community dominated by the coccolithophore Emiliania huxleyi

We exposed a natural phytoplankton community to combined present (390 µatm, low carbon [LC]) and future CO2 levels predicted for the year 2100 (900 µatm, high carbon [HC]), and ambient (4.5 nM, -DFB [desferoxamine B]) and high (12 nM, +DFB) dissolved iron (dFe) levels, for 25 d in mesocosms. We report on the physiological response of the community dominated by the coccolithophore Emiliania huxleyi. The community structure shifted on Day 10, leading to 2 different phases (1 and 2), i.e. before and after Day 10, respectively. We focussed on the massive bloom of E. huxleyi that developed in Phase 2, in the LC+DFB treatment. In high dFe conditions, pigments and photosynthetic parameters increased compared to the control (LC-DFB). Cell death was only detected during the community shift (Days 10-12) and mostly increased in the presence of high CO2. The accumulation of reactive oxygen species (ROS) decreased under high dFe, pointing to an efficient, rather than a stressed, metabolism. DNA lesions, caused by excess irradiance, were minimised under high Fe. E. huxleyi is known for its low Fe requirements for growth. However, we demonstrate that Fe is essential to E. huxleyi for DNA repair and ROS management, and to maintain optimal functioning of the photosynthetic machinery, with implications for carbon cycling and future ecosystem functioning.

Continue reading ‘Physiological stress response associated with elevated CO2 and dissolved iron in a phytoplankton community dominated by the coccolithophore Emiliania huxleyi’

What is the best endpoint for assessing environmental risk associated with acidification caused by CO2 enrichment using mussels?

Highlights

• The paper uses three endpoints to analyze the impacts of CO2 enrichment on mussels.
• The results showed significant effects on the mussels associated with low pH values.
• The increase in pCO2 was strongly correlated with the increase of certain metals.
• LMS and embryo-larval assays provide sensitive results of ocean acidification.

Abstract

Carbon capture and storage is a technology that has been widely determined to be one of the best choices for the short-term reduction of atmospheric CO2 emissions. The aim of this study was to analyze the effects of CO2 enrichment in the ocean on the mussel species Mytilus galloprovincialis using three different endpoints: mortality, embryo-larval development, and neutral red retention time assays (NRRT). Acute effects were found to be associated with a pH values of 6.0 while citotoxity effects and embryo-larval development were associated with a pH value of 7.0. The NRRT assay and embryo-larval development can be recommended as good endpoints for assessing the environmental risk associated with acidification by CO2 enrichment because they provide sensitive responses on the effects of changes in seawater pH on mussels in a short period of time. Moreover, this study may support policymakers in finding appropriate solutions for the conservation of marine ecosystems.

Continue reading ‘What is the best endpoint for assessing environmental risk associated with acidification caused by CO2 enrichment using mussels?’

Growth performance and survival of larval Atlantic herring, under the combined effects of elevated temperatures and CO2

In the coming decades, environmental change like warming and acidification will affect life in the ocean. While data on single stressor effects on fish are accumulating rapidly, we still know relatively little about interactive effects of multiple drivers. Of particular concern in this context are the early life stages of fish, for which direct effects of increased CO2 on growth and development have been observed. Whether these effects are further modified by elevated temperature was investigated here for the larvae of Atlantic herring (Clupea harengus), a commercially important fish species. Over a period of 32 days, larval survival, growth in size and weight, and instantaneous growth rate were assessed in a crossed experimental design of two temperatures (10°C and 12°C) with two CO2 levels (400 μatm and 900 μatm CO2) at food levels mimicking natural levels using natural prey. Elevated temperature alone led to increased swimming activity, as well as decreased survival and instantaneous growth rate (Gi). The comparatively high sensitivity to elevated temperature in this study may have been influenced by low food levels offered to the larvae. Larval size, Gi and swimming activity were not affected by CO2, indicating tolerance of this species to projected “end of the century” CO2 levels. A synergistic effect of elevated temperature and CO2 was found for larval weight, where no effect of elevated CO2 concentrations was detected in the 12°C treatment, but a negative CO2 effect was found in the 10°C treatment. Contrasting CO2 effects were found for survival between the two temperatures. Under ambient CO2 conditions survival was increased at 12°C compared to 10°C. In general, CO2 effects were minor and considered negligible compared to the effect of temperature under these mimicked natural food conditions. These findings emphasize the need to include biotic factors such as energy supply via prey availability in future studies on interactive effects of multiple stressors.

Continue reading ‘Growth performance and survival of larval Atlantic herring, under the combined effects of elevated temperatures and CO2’

Transgenerational responses of a gammarid amphipod to ocean acidification: effects on reproductive traits, mate detection and metabolism

Ocean acidification (OA) poses a global threat to marine biodiversity. The rise in atmospheric carbon dioxide (CO2) concentration, resulting from anthropogenic activities, is responsible for the increase in the dissolved state of this gas in the oceans. The consequent changes in pH and seawater carbonate chemistry are responsible for the disruption of several biological processes (e.g. impairing survival and the maintenance of fitness-enhancing, physiological and behavioural, mechanisms) in certain marine groups. Disruption at the individual level, can originate negative cascading effects at higher levels of biological organization (i.e. populations and communities), which in turn can alter the underlying dynamics that control an ecosystem’s structure and overall function. Current theories suggest that marine organisms might be able to maintain their performance in future OA conditions, either through acclimation or through evolutionary adaptation. Surprisingly, the effects of prolonged high-CO2 exposure in crustaceans are still poorly known. The present dissertation investigates, for the first time, the transgenerational effects (i.e. over two generations) of ocean acidification in the physiology, behaviour (e.g. male mate-attraction) and reproductive traits (e.g. female investment, fecundity, mate-guarding and embryonic development) of the gammarid amphipod Gammarus locusta. Significant effects of ocean acidification were found for most reproductive traits. Although OA may initially stimulate female investment, transgenerational exposure led to an overall reduction in egg number and fecundity. The duration of mate-guarding behaviours was also diminished under high-CO2 exposure. Individuals from the second generation (F1) exhibited metabolic depression (i.e. reduced oxygen consumption rates), and males also displayed a reduced ability to accurately identify and track the origin of female scent cues, thus hinting at a possible disruption of chemosensory abilities. Overall, negative transgenerational (i.e. parental) effects were observed for all reproductive traits, as well as survival, in the acidified lineage. The present findings suggest that exposure to a future ocean acidification scenario will likely lead to a reduction in the fitness of the natural populations of G. locusta.

Continue reading ‘Transgenerational responses of a gammarid amphipod to ocean acidification: effects on reproductive traits, mate detection and metabolism’


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Ocean acidification in the IPCC AR5 WG II

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