Posts Tagged 'respiration'

Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation

Crustose coralline algae (CCA) are vital to coral reefs worldwide, providing structural integrity and inducing the settlement of important invertebrate larvae. CCA are known to be impacted by changes in their environment, both during early development and adulthood. However, long-term studies on either life history stage are lacking in the literature, therefore not allowing time to explore the acclimatory or potential adaptive responses of CCA to future global change scenarios. Here, we exposed a widely distributed, slow growing, species of CCA, Sporolithon cf. durum, to elevated temperature and pCO2 for five months and their first set of offspring (F1) for eleven weeks. Survival, reproductive output, and metabolic rate were measured in adult S. cf. durum, and survival and growth were measured in the F1 generation. Adult S. cf. durum experienced 0% mortality across treatments and reduced their O2 production after five months exposure to global stressors, indicating a possible expression of plasticity. In contrast, the combined stressors of elevated temperature and pCO2 resulted in 50% higher mortality and 61% lower growth on germlings. On the other hand, under the independent elevated pCO2 treatment, germling growth was higher than all other treatments. These results show the robustness and plasticity of S. cf. durum adults, indicating the potential for them to acclimate to increased temperature and pCO2. However, the germlings of this species are highly sensitive to global stressors and this could negatively impact this species in future oceans, and ultimately the structure and stability of coral reefs.

Continue reading ‘Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation’

Response of the red algae Pyropia yezoensis grown at different light intensities to CO2-induced seawater acidification at different life cycle stages

Highlights

•Elevated CO2 enhanced conchocelis growth regardless of light intensity.

•Elevated CO2 enhanced thallus growth at high light but reduced it at low light.

•Elevated CO2 did not affect conchocelis respiration rate at either light intensity.

•Elevated CO2 increased thallus respiration rate at each light intensity.

Abstract

Increasing CO2 levels in the surface water of oceans are expected to decrease oceanic pH and lead to seawater acidification. The responses of macroalgaea to this acidification of coastal waters have been studied in detail; however, most reports have focused on the adult stage only, while ignoring other life cycle stages. In this study, the economically important seaweed species Pyropia yezoensis was cultured under two CO2 concentrations (ambient CO2: 400 μatm; elevated CO2: 1000 μatm) and two light intensities (low light intensity: 80 μmol photons m−2 s−1; and high light intensity: 240 μmol photons m−2 s−1). The effects on the growth and photosynthetic performance of P. yezoensis were explored at different life cycle stages. Relative growth rates were significantly elevated at the conchocelis stage under high light intensity and elevated CO2 concentration. Moreover, the Pmax of P. yezoensis was also increased under high light intensity. However, this positive effect inversed at the thallus stage. The relative growth rate, relative electron transport rate (rETR), and net photosynthetic rate decreased at the thallus stage in response to high CO2 concentration. Under low light intensity, elevated CO2 concentration significantly increased the relative growth rates of conchocelis and thallus stages. These were 269% and 45% higher at elevated CO2 concentration compared with ambient CO2 concentrations, respectively. The Chl a and phycoerythrin levels were also higher under elevated CO2 level at the conchocelis stage. However, the rETR for the thallus stage was elevated under low light. This suggests that seawater acidification could positively affect algae at low light conditions (especially at the conchocelis stage). Different growth stages of P. yezoensis may respond differently to seawater acidification and changes of light intensity. Thalli growth stage, stocking density, and seawater depth should be considered in different areas to optimize the primary production of macroalgae.

Continue reading ‘Response of the red algae Pyropia yezoensis grown at different light intensities to CO2-induced seawater acidification at different life cycle stages’

Seasonal variability of the CO2 system in a large coastal plain estuary

The Chesapeake Bay, a large coastal plain estuary, has been studied extensively in terms of its water quality, and yet, comparatively less is known about its carbonate system. Here we present discrete observations of dissolved inorganic carbon (DIC) and total alkalinity from four seasonal cruises in 2016–2017. These new observations are used to characterize the regional CO2 system and to construct a DIC budget of the mainstem. In all seasons, elevated DIC concentrations were observed at the mouth of the bay associated with inflowing Atlantic Ocean waters, while minimum concentrations of DIC were associated with fresher waters at the head of the bay. Significant spatial variability of the partial pressure of CO2 was observed throughout the mainstem, with net uptake of atmospheric CO2 during each season in the upper mainstem and weak seasonal outgassing of CO2 near the outflow to the Atlantic Ocean. During the time frame of this study, the Chesapeake Bay mainstem was (1) net autotrophic in the mixed layer (net community production of 0.31‐mol C m−2 ·year−1 ) and net heterotrophic throughout the water column (net community production of −0.48‐mol C m−2 ·year−1), (2) a sink of 0.38‐mol C m−2 ·year−1 for atmospheric CO2, and (3) significantly seasonally and spatially variable with respect to biologically driven changes in DIC.

Continue reading ‘Seasonal variability of the CO2 system in a large coastal plain estuary’

Nutrient enrichment regulates the growth and physiological responses of Saccharina japonica to ocean acidification

Environmental changes, such as ocean acidification and eutrophication, have created threats to kelp mariculture. In this study, the growth, photosynthesis, respiration and nutrient composition of Saccharina japonica were evaluated at different levels of pCO2 (400 and 800 μL L−1) and nutrients (nutrient-enriched and non-enriched seawater). Elevated pCO2 decreased the relative growth rate (RGR), net photosynthetic rate and contents of tissue carbon and tissue nitrogen under non-enriched nutrient conditions, but it had no significant effect on these parameters under nutrient-enriched conditions. The dark respiration rate was positively affected by elevated pCO2 regardless of the nutrient conditions. However, the C:N was unaffected by elevated pCO2 at both nutrient levels. These results implied that ocean acidification could reduce the production and nutrient contents in the tissues of S. japonica, which was associated with nutrient conditions.

Continue reading ‘Nutrient enrichment regulates the growth and physiological responses of Saccharina japonica to ocean acidification’

Metabolic responses of subtropical microplankton after a simulated deep-water upwelling event suggest a possible dominance of mixotrophy under increasing CO2 levels

In the autumn of 2014, nine large mesocosms were deployed in the oligotrophic subtropical North-Atlantic coastal waters off Gran Canaria (Spain). Their deployment was designed to address the acidification effects of CO2 levels from 400 to 1,400 μatm, on a plankton community experiencing upwelling of nutrient-rich deep water. Among other parameters, chlorophyll a (chl-a), potential respiration (Φ), and biomass in terms of particulate protein (B) were measured in the microplankton community (0.7–50.0 μm) during an oligotrophic phase (Phase I), a phytoplankton-bloom phase (Phase II), and a post-bloom phase (Phase III). Here, we explore the use of the Φ/chl-a ratio in monitoring shifts in the microplankton community composition and its metabolism. Φ/chl-a values below 2.5 μL O2 h−1 (μg chl-a)−1 indicated a community dominated by photoautotrophs. When Φ/chl-a ranged higher, between 2.5 and 7.0 μL O2 h−1 (μg chl-a)−1, it indicated a mixed community of phytoplankton, microzooplankton and heterotrophic prokaryotes. When Φ/chl-a rose above 7.0 μL O2 h−1 (μg chl-a)−1, it indicated a community where microzooplankton proliferated (>10.0 μL O2 h−1 (μg chl-a)−1), because heterotrophic dinoflagellates bloomed. The first derivative of B, as a function of time (dB/dt), indicates the rate of protein build-up when positive and the rate of protein loss, when negative. It revealed that the maximum increase in particulate protein (biomass) occurred between 1 and 2 days before the chl-a peak. A day after this peak, the trough revealed the maximum net biomass loss. This analysis did not detect significant changes in particulate protein, neither in Phase I nor in Phase III. Integral analysis of Φ, chl-a and B, over the duration of each phase, for each mesocosm, reflected a positive relationship between Φ and pCO2 during Phase II [α = 230·10−5 μL O2 h−1 L−1 (μatm CO2)−1 (phase-day)−1, R2 = 0.30] and between chl-a and pCO2 during Phase III [α = 100·10−5 μg chl-a L−1 (μ atmCO2)−1 (phase-day)−1, R2 = 0.84]. At the end of Phase II, a harmful algal species (HAS), Vicicitus globosus, bloomed in the high pCO2 mesocosms. In these mesocosms, microzooplankton did not proliferate, and chl-a retention time in the water column increased. In these V. globosus-disrupted communities, the Φ/chl-a ratio [4.1 ± 1.5 μL O2 h−1 (μg chl-a)−1] was more similar to the Φ/chl-a ratio in a mixed plankton community than to a photoautotroph-dominated one.

Continue reading ‘Metabolic responses of subtropical microplankton after a simulated deep-water upwelling event suggest a possible dominance of mixotrophy under increasing CO2 levels’

Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies

Anthropogenic greenhouse gas emissions, including carbon dioxide, are causing an unprecedented rate of global warming. Carbon dioxide emissions are additionally causing ocean acidification; a process that decreases the pH and carbonate saturation state of seawater. Ocean acidification is particularly stressful for marine calcifiers; organisms that build calcium carbonate shells or skeletons. Marine bivalves build calcium carbonate shells that they use as a support for their growing tissues, and as protection from predation. Bivalves are osmoconformers, and have limited mobility, meaning that they are particularly susceptible to the impacts of thermal stress. Bivalve fisheries generate billions of dollars to the US economy in annual revenue, therefore understanding their response to these two global change stressors is crucial for helping the communities that rely on these fisheries plan for global change. The following studies explore the response of commercially important bivalve species to ocean acidification and warming.

Continue reading ‘Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies’

Beneficial effects of diel CO2 cycles on reef fish metabolic performance are diminished under elevated temperature

Highlights

•Coastal habitats and coral reefs often exhibit a diel cycle of pCO2.

•It is unknown how diel-cycling CO2 and temp affect metabolic traits in reef fishes.

•Traits measured were maximal/resting O2 uptake and factorial/absolute aerobic scope.

•Beneficial effect of diel-cycling CO2 on O2Rest and FAS diminished at high temp.

•Studies should use habitat-relevant CO2 cycles/temp to predict biological effects.

Abstract

Elevated CO2 levels have been shown to affect metabolic performance in some coral reef fishes. However, all studies to date have employed stable elevated CO2 levels, whereas reef habitats can experience substantial diel fluctuations in pCO2 ranging from ±50 to 600 μatm around the mean, fluctuations that are predicted to increase in magnitude by the end of the century. Additionally, past studies have often investigated the effect of elevated CO2 in isolation, despite the fact that ocean temperatures will increase in tandem with CO2 levels. Here, we tested the effects of stable (1000 μatm) versus diel-cycling (1000 ± 500 μatm) elevated CO2 conditions and elevated temperature (+2 °C) on metabolic traits of juvenile spiny damselfish, Acanthochromis polyacanthus. Resting oxygen uptake rates (O2) were higher in fish exposed to stable elevated CO2 conditions when compared to fish from stable control conditions, but were restored to control levels under diel CO2 fluctuations. However, the benefits of diel CO2 fluctuations were diminished at elevated temperature. Factorial aerobic scope showed a similar pattern, but neither maximal O2 nor absolute aerobic scope was affected by CO2 or temperature. Our results suggest that diel CO2 cycles can ameliorate the increased metabolic cost associated with elevated CO2, but elevated temperature diminishes the benefits of diel CO2 cycles. Thus, previous studies may have misestimated the effect of ocean acidification on the metabolic performance of reef fishes by not accounting for environmental CO2 fluctuations. Our findings provide novel insights into the interacting effects of diel CO2 fluctuations and temperature on the metabolic performance of reef fishes.

Continue reading ‘Beneficial effects of diel CO2 cycles on reef fish metabolic performance are diminished under elevated temperature’

Metabolic recovery and compensatory shell growth of juvenile Pacific geoduck Panopea generosa following short-term exposure to acidified seawater

While acute stressors can be detrimental, environmental stress conditioning can improve performance. To test the hypothesis that physiological status is altered by stress conditioning, we subjected juvenile Pacific geoduck, Panopea generosa, to repeated exposures of elevated pCO2 in a commercial hatchery setting followed by a period in ambient common garden. Respiration rate and shell length were measured for juvenile geoduck periodically throughout short-term repeated reciprocal exposure periods in ambient (~550 μatm) or elevated (~2400 μatm) pCO2 treatments and in common, ambient conditions, 5 months after exposure. Short-term exposure periods comprised an initial 10-day exposure followed by 14 days in ambient before a secondary 6-day reciprocal exposure. The initial exposure to elevated pCO2 significantly reduced respiration rate by 25% relative to ambient conditions, but no effect on shell growth was detected. Following 14 days in common garden, ambient conditions, reciprocal exposure to elevated or ambient pCO2 did not alter juvenile respiration rates, indicating ability for metabolic recovery under subsequent conditions. Shell growth was negatively affected during the reciprocal treatment in both exposure histories; however, clams exposed to the initial elevated pCO2 showed compensatory growth with 5.8% greater shell length (on average between the two secondary exposures) after 5 months in ambient conditions. Additionally, clams exposed to the secondary elevated pCO2 showed 52.4% increase in respiration rate after 5 months in ambient conditions. Early exposure to low pH appears to trigger carryover effects suggesting bioenergetic re-allocation facilitates growth compensation. Life stage-specific exposures to stress can determine when it may be especially detrimental, or advantageous, to apply stress conditioning for commercial production of this long-lived burrowing clam.

Continue reading ‘Metabolic recovery and compensatory shell growth of juvenile Pacific geoduck Panopea generosa following short-term exposure to acidified seawater’

The effects of elevated temperature and PCO2 on the energetics and haemolymph pH homeostasis of juveniles of the European lobster, Homarus gammarus

Regulation of extracellular acid–base balance, while maintaining energy metabolism, is recognised as an important aspect when defining an organism’s sensitivity to environmental changes. This study investigated the haemolymph buffering capacity and energy metabolism (oxygen consumption, haemolymph [l-lactate] and [protein]) in early benthic juveniles (carapace length <40 mm) of the European lobster, Homarus gammarus, exposed to elevated temperature and PCO2. At 13°C, H. gammarus juveniles were able to fully compensate for acid–base disturbances caused by the exposure to elevated seawater PCO2 at levels associated with ocean acidification and carbon dioxide capture and storage (CCS) leakage scenarios, via haemolymph [HCO3−] regulation. However, metabolic rate remained constant and food consumption decreased under elevated PCO2, indicating reduced energy availability. Juveniles at 17°C showed no ability to actively compensate haemolymph pH, resulting in decreased haemolymph pH particularly under CCS conditions. Early benthic juvenile lobsters at 17°C were not able to increase energy intake to offset increased energy demand and therefore appear to be unable to respond to acid–base disturbances due to increased PCO2 at elevated temperature. Analysis of haemolymph metabolites suggests that, even under control conditions, juveniles were energetically limited. They exhibited high haemolymph [l-lactate], indicating recourse to anaerobic metabolism. Low haemolymph [protein] was linked to minimal non-bicarbonate buffering and reduced oxygen transport capacity. We discuss these results in the context of potential impacts of ongoing ocean change and CCS leakage scenarios on the development of juvenile H. gammarus and future lobster populations and stocks.

Continue reading ‘The effects of elevated temperature and PCO2 on the energetics and haemolymph pH homeostasis of juveniles of the European lobster, Homarus gammarus’

Adjustments in fatty acid composition is a mechanism that can explain resilience to marine heatwaves and future ocean conditions in the habitat‐forming seaweed Phyllospora comosa (Labillardière) C.Agardh

Marine heatwaves are extreme events that can have profound and lasting impacts on marine species. Field observations have shown seaweeds to be highly susceptible to marine heatwaves, but the physiological drivers of this susceptibility are poorly understood. Furthermore, the effects of marine heatwaves in conjunction with ocean warming and acidification are yet to be investigated. To address this knowledge gap, we conducted a laboratory culture experiment in which we tested the growth and physiological responses of Phyllospora comosa juveniles from the southern extent of its range (43–31°S) to marine heatwaves, ocean warming and acidification. We used a ‘collapsed factorial design’ in which marine heatwaves were superimposed on current (today’s pH and temperature) and future (pH and temperature projected by 2100) ocean conditions. Responses were tested both during the heatwaves, and after a 7‐day recovery period. Heatwaves reduced net photosynthetic rates in both current and future conditions, while respiration rates were elevated under heatwaves in the current conditions only. Following the recovery period, there was little evidence of heatwaves having lasting negative effects on growth, photosynthesis or respiration. Exposure to heatwaves, future ocean conditions or both caused an increase in the degree of saturation of fatty acids. This adjustment may have counteracted negative effects of elevated temperatures by decreasing membrane fluidity, which increases at higher temperatures. Furthermore, P. comosa appeared to down‐regulate the energetically expensive carbon dioxide concentrating mechanism in the future conditions with a reduction in δ13C values detected in these treatments. Any saved energy arising from this down‐regulation was not invested in growth and was likely invested in the adjustment of fatty acid composition. This adjustment is a mechanism by which P. comosa and other seaweeds may tolerate the negative effects of ocean warming and marine heatwaves through benefits arising from ocean acidification.

Continue reading ‘Adjustments in fatty acid composition is a mechanism that can explain resilience to marine heatwaves and future ocean conditions in the habitat‐forming seaweed Phyllospora comosa (Labillardière) C.Agardh’


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Ocean acidification in the IPCC AR5 WG II

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