Posts Tagged 'respiration'

Local habitat influences on feeding and respiration of the intertidal mussels Perumytilus purpuratus exposed to increased pCO2 levels

Coastal ecosystems are exposed to changes in physical-chemical properties, such as those occurring in upwelling and freshwater-influenced areas. In these areas, inorganic carbon can influence seawater properties that may affect organisms and populations inhabiting benthic habitats such as the intertidal mussel Perumytilus purpuratus. Feeding and metabolic responses were measured in adult mussels from two geographic regions (central and southern Chile) and two local habitats (river-influenced and non-river-influenced) and three pCO2 levels (380, 750, and 1200 μatm pCO2 in seawater). The feeding rates of mussels tend to increase at high pCO2 levels in seawater; however this response was variable across regions and local habitats. In contrast, there was no difference in the respiratory rate of mussels between geographic areas, but there was a significant reduction of oxygen consumption at intermediate and high levels of pCO2. The results indicate that river-influenced organisms compensate for reductions in metabolic cost at elevated pCO2 levels by having their energy demands met, in contrast with non-river-influenced organisms. The lack of regional-scale variability in the physiological performance of mussels may indicate physiological homogeneity across populations and thus potential for local adaptation. However, the local-scale influences of river- and non-river-influenced habitats may counterbalance this regional response promoting intra-population variability and phenotypic plasticity in P. purpuratus. The plasticity may be an important mechanism that allows mussels to confront the challenges of projected ocean acidification scenarios.

Continue reading ‘Local habitat influences on feeding and respiration of the intertidal mussels Perumytilus purpuratus exposed to increased pCO2 levels’

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’

Responses of photosynthesis and CO2 concentrating mechanisms of marine crop Pyropia haitanensis thalli to large pH variations at different time scales

Highlights

• A pH of 4, 5, and 9 resulted in the death of Pyropia haitanensis thalli.
• A pH of 6 and 7 increased the growth of Pyropia haitanensis thalli.
• The CO2 concentrating mechanisms may play a role in intracellular pH homeostasis.
• Actual pH variation needs to be considered in relative studies.
Abstract

Wild and cultivated populations of Pyropia haitanensis have frequently experienced extremely low pH conditions in the last few decades. This could potentially threaten the development of the aquaculture of this economically important marine crop. To gain a broader perspective, we investigated the short- (4 h) and long- (7 days) term responses of CO2 concentrating mechanisms (CCMs) of P. haitanensis thalli to large variations in pH. Our study found that a pH of 4 and 5, which mimicked the decreased pH caused by acid rain, resulted in decreased photosynthesis and respiration while leading to the death of P. haitanensis thalli. Thus, acid rain would result in a decline in P. haitanensis production and threaten wild seaweed sources. However, a pH of 6 and 7 enhanced the growth of P. haitanensis thalli by > 30%, mainly because increased CO2 levels favored photosynthesis, while the algae need to effectively maintain intracellular pH homeostasis to support rapid growth rates. The contributions of extracellular carbonic anhydrases (eCAs) to photosynthetic rates remained at > 77% when pH ≥ 7, regardless of the treatment time. However, at pH 6, the contribution of eCAs to photosynthesis increased from 25% for a short-term treatment to 66% for a long-term treatment. Thus, except for work on carbon assimilation, this study proposes that the CCMs component involved in the movement and metabolism of inorganic carbon may play an important role in pH homeostasis. In addition, pH 9 also led to the death of P. haitanensis thalli, which is consistent with observations of the natural distribution of this algae and hints that P. haitanensis thalli prefer to use inorganic carbon via eCAs when pH ≥ 7. The present study suggested that the actual variation in pH experienced by marine organisms needs to be considered in the experimental design of related studies.

Continue reading ‘Responses of photosynthesis and CO2 concentrating mechanisms of marine crop Pyropia haitanensis thalli to large pH variations at different time scales’

Exposure to elevated pCO2 does not exacerbate reproductive suppression of Aurelia aurita jellyfish polyps in low oxygen environments

Eutrophication-induced hypoxia is one of the primary anthropogenic threats to coastal ecosystems. Under hypoxic conditions, a deficit of O2 and a surplus of CO2 will concurrently decrease pH, yet studies of hypoxia have seldom considered the potential interactions with elevated pCO2 (reduced pH). Previous studies on gelatinous organisms concluded that they are fairly robust to low oxygen and reduced pH conditions individually, yet the combination of stressors has only been examined for ephyrae. The goals of this study were to determine the individual and interactive effects of hypoxia and elevated pCO2 on the asexual reproduction and aerobic respiration rates of polyps of the scyphozoan Aurelia aurita during a manipulative experiment that ran for 36 d. pCO2 and pO2 were varied on a diel basis to closely mimic the diel conditions observed in the field. Exposure to low dissolved oxygen (DO) reduced asexual budding of polyps by ~50% relative to control conditions. Under hypoxic conditions, rates of respiration were elevated during an initial acclimation period (until Day 8), but respiration rates did not differ between DO levels under prolonged exposure. There was no significant effect of increased pCO2 on either asexual reproduction or aerobic respiration, suggesting that elevated pCO2 (reduced pH) did not exacerbate the negative reproductive effects of hypoxia on A. aurita polyps.

Continue reading ‘Exposure to elevated pCO2 does not exacerbate reproductive suppression of Aurelia aurita jellyfish polyps in low oxygen environments’

The regulation of coralline algal physiology, an in situ study of Corallina officinalis (Corallinales, Rhodophyta) (update)

Calcified macroalgae are critical components of marine ecosystems worldwide, but face considerable threat both from climate change (increasing water temperatures) and ocean acidification (decreasing ocean pH and carbonate saturation). It is thus fundamental to constrain the relationships between key abiotic stressors and the physiological processes that govern coralline algal growth and survival. Here we characterize the complex relationships between the abiotic environment of rock pool habitats and the physiology of the geniculate red coralline alga, Corallina officinalis (Corallinales, Rhodophyta). Paired assessment of irradiance, water temperature and carbonate chemistry, with C. officinalis net production (NP), respiration (R) and net calcification (NG) was performed in a south-western UK field site, at multiple temporal scales (seasonal, diurnal and tidal). Strong seasonality was observed in NP and night-time R, with a Pmax of 22.35 µmol DIC (g DW)−1 h−1, Ek of 300 µmol photons m−2 s−1 and R of 3.29 µmol DIC (g DW)−1 h−1 determined across the complete annual cycle. NP showed a significant exponential relationship with irradiance (R2 = 0.67), although was temperature dependent given ambient irradiance  > Ek for the majority of the annual cycle. Over tidal emersion periods, dynamics in NP highlighted the ability of C. officinalis to acquire inorganic carbon despite significant fluctuations in carbonate chemistry. Across all data, NG was highly predictable (R2 = 0.80) by irradiance, water temperature and carbonate chemistry, providing a NGmax of 3.94 µmol CaCO3 (g DW)−1 h−1 and Ek of 113 µmol photons m−2 s−1. Light NG showed strong seasonality and significant coupling to NP (R2 = 0.65) as opposed to rock pool water carbonate saturation. In contrast, the direction of dark NG (dissolution vs. precipitation) was strongly related to carbonate saturation, mimicking abiotic precipitation dynamics. Data demonstrated that C. officinalis is adapted to both long-term (seasonal) and short-term (tidal) variability in environmental stressors, although the balance between metabolic processes and the external environment may be significantly impacted by future climate change.

Continue reading ‘The regulation of coralline algal physiology, an in situ study of Corallina officinalis (Corallinales, Rhodophyta) (update)’

Combined effects of ocean acidification with morphology, water flow, and algal acclimation on metabolic rates of tropical coralline algae

Coral reefs are currently facing multiple stressors that threaten their health and function, including ocean acidification (OA). OA has been shown to negatively affect many reef calcifiers, such as coralline algae that provide many critical contributions to reef systems. Past studies have focused on how OA independently influences coralline algae, but more research is necessary as it is expected that the effects of OA on coralline algae will vary depending on many other factors. To better understand how algal morphology, water flow, and algal acclimation interact with OA to affect coralline algae, three studies were conducted in Moorea, French Polynesia, from June 2015 to July 2016. In January 2016, I tested the hypothesis that algal individuals with higher morphological complexity would exhibit faster metabolic rates under ambient pCO2 conditions, but would also demonstrate higher sensitivity to OA conditions. For three species of crustose coralline algae, Lithophyllum kotschyanum, Neogoniolithon frutescens, and Hydrolithon reinboldii, algal individuals with more complex morphologies demonstrated faster rates of calcification, photosynthesis, and respiration in the ambient pCO2 treatment than individuals with simpler morphological forms. There also appeared to be a relationship between morphology and sensitivity to OA conditions, with calcification rates negatively correlated with higher morphological complexity. In the summers of 2015 and 2016, I conducted three experiments examining the effects of water flow and OA on different morphologies of coralline algae to test the hypotheses that increased flow would enhance metabolic rates and mitigate the effects of OA, and that algae with more complex morphologies would be more responsive to increased water flow and more sensitive to OA conditions. A field experiment investigating the effects of water flow on Amphiroa fragilissima, L. kotschyanum, N. frutescens, and H. reinboldii detected enhanced rates of calcification, photosynthesis, and respiration with increased flow, and this relationship appeared to be the strongest for the crustose algal species with the highest structural complexity. A flume manipulation examining the combined effects of water flow and OA on A. fragilissima, L. kotschyanum, N. frutescens, H. reinboldii, and Porolithon onkodes suggested that coralline algal species with high structural complexity were the most sensitive to OA conditions. Finally, A. fragilissima and L. kotschyanum were maintained in different pCO2 and water flow conditions in a long-term mesocosm experiment, which indicated that flow was unable to mitigate the effects of OA on coralline algae. In the summer of 2016, I investigated the acclimation potential of A. fragilissima and L. kotschyanum to OA, and predicted that the original treatment conditions would induce phenotypic modifications that would influence algal responses to the end treatment. There were negative effects of long-term exposure of coralline algae to elevated pCO2 conditions on calcification and photosynthesis, though partial acclimation in calcification to OA was observed. The instantaneous exposure of elevated pCO2 had negative impacts on algal calcification, but had a nominal effect on photosynthesis. No effects of long-term or instantaneous exposure to elevated pCO2 were observed for respiration. The results of these studies indicate that the coralline algal response to OA conditions will likely be complex and depend on numerous factors including water flow, morphology, and acclimation potential. Therefore, it is critical that future studies further investigate the effects of these factors; specifically examining the mechanisms that underlie these responses in order to better predict the future of coralline algae and thus coral reef ecosystems in a more acidic ocean.

Continue reading ‘Combined effects of ocean acidification with morphology, water flow, and algal acclimation on metabolic rates of tropical coralline algae’

Differing responses of the estuarine bivalve Limecola balthica to lowered water pH caused by potential CO2 leaks from a sub-seabed storage site in the Baltic Sea: an experimental study

Highlights

  • CO2-induced seawater acidification affected behavioral and physiological traits of Limecola balthica from the Baltic Sea.
  • In response to hypercapnia, the bivalves approached the sediment surface and increased respiration rates.
  • Lower seawater pH reduced shell weight and growth, and increased soft tissue weight that places L. balthica in a unique position among marine invertebrates.

Abstract

Sub-Seabed CCS is regarded as a key technology for the reduction of CO2 emissions, but little is known about the mechanisms through which leakages from storage sites impact benthic species. In this study, the biological responses of the infaunal bivalve Limecola balthica to CO2-induced seawater acidification (pH 7.7, 7.0, and 6.3) were quantified in 56-day mesocosm experiments. Increased water acidity caused changes in behavioral and physiological traits, but even the most acidic conditions did not prove to be fatal. In response to hypercapnia, the bivalves approached the sediment surface and increased respiration rates. Lower seawater pH reduced shell weight and growth, while it simultaneously increased soft tissue weight; this places L. balthica in a somewhat unique position among marine invertebrates.

Continue reading ‘Differing responses of the estuarine bivalve Limecola balthica to lowered water pH caused by potential CO2 leaks from a sub-seabed storage site in the Baltic Sea: an experimental study’


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