Posts Tagged 'performance'

Using stable isotope analysis to determine the effects of ocean acidification and warming on trophic interactions in a maerl bed community

Ocean acidification and warming are likely to affect the structure and functioning of marine benthic communities. This study experimentally examined the effects of ocean acidification and warming on trophic interactions within a maerl bed community by using stable carbon and nitrogen isotope analysis. Two three‐month experiments were conducted in winter and summer seasons with four different combinations of pCO2 (ambient and elevated pCO2) and temperature (ambient and +3°C). Experimental assemblages were created in tanks held in the laboratory and were composed of calcareous (Lithothamnion corallioides) and fleshy algae (Rhodymenia ardissonei, Solieria chordalis, and Ulva sp.), gastropods (Gibbula magus and Jujubinus exasperatus), and sea urchins (Psammechinus miliaris). Our results showed higher seaweed availability for grazers in summer than winter. Therefore, grazers were able to adapt their diet seasonally. Increased pCO2 and temperature did not modify the trophic structure in winter, while shifts in the contribution of seaweed were found in summer. Combined acidification and warming increased the contribution of biofilm in gastropods diet in summer conditions. Psammechinus miliaris mostly consumed L. corallioides under ambient conditions, while the alga S. chordalis became the dominant food source under high pCO2 in summer. Predicted changes in pCO2 and temperature had complex effects on assemblage trophic structure. Direct effects of acidification and warming on seaweed metabolism may modify their abundance and biomass, affecting their availability for grazers. Climate change may also modify seaweeds’ nutritive value and their palatability for grazers. The grazers we investigated were able to change their diet in response to changes in algal assemblages, an advantage given that warming and acidification alter the composition of algal communities.

Continue reading ‘Using stable isotope analysis to determine the effects of ocean acidification and warming on trophic interactions in a maerl bed community’

Hypoxia and acidification, individually and in combination, disrupt herbivory and reduce survivorship of the gastropod, Lacuna vincta

Acidification and deoxygenation are two consequences of climate change that also co-occur in eutrophied coastal zones and can have deleterious effects on marine life. While the effects of hypoxia on marine herbivores have been well-studied, how ocean acidification combined with hypoxia affects herbivory is poorly understood. This study examined how herbivory and survival by the gastropod Lacuna vincta grazing on the macroalgae Ulva rigida was influenced by hypoxia and ocean acidification, alone and in combination, with and without food limitation. Experiments exposed L. vincta to a range of environmentally realistic dissolved oxygen (0.7 – 8 mg L–1) and pH (7.3 – 8.0 total scale) conditions for 3 – 72 h, with and without a starvation period and quantified herbivory and survival. While acidified conditions (pH < 7.4) reduced herbivory when combined with food limitation, low oxygen conditions (< 4 mg L–1) reduced herbivory and survival regardless of food supply. When L. vincta were starved and grazed in acidified conditions herbivory was additively reduced, whereas starvation and hypoxia synergistically reduced grazing rates. Overall, low oxygen had a more inhibitory effect on herbivory than low pH. Shorter exposure times (9, 6, and 3 h) were required to reduce grazing at lower DO levels (∼2.4, ∼1.6, and ∼0.7 mg L–1, respectively). Herbivory ceased entirely following a three-hour exposure to DO of 0.7 mg L–1 suggesting that episodes of diurnal hypoxia disrupt grazing by these gastropods. The suppression of herbivory in response to acidified and hypoxic conditions could create a positive feedback loop that promotes ‘green tides’ whereby reduced grazing facilitates the overgrowth of macroalgae that cause nocturnal acidification and hypoxia, further disrupting herbivory and promoting the growth of macroalgae. Such feedback loops could have broad implications for estuarine ecosystems where L. vincta is a dominant macroalgal grazer and will intensify as climate change accelerates.

Continue reading ‘Hypoxia and acidification, individually and in combination, disrupt herbivory and reduce survivorship of the gastropod, Lacuna vincta’

An extreme decline effect in ocean acidification ecology

Ocean acidification – deceasing oceanic pH resulting from the uptake of excess atmospheric CO2 – is expected to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fishes suggested that the direct effects of acidification on fish behaviour will be the most catastrophic. Recent studies documenting a lack of effect of experimental ocean acidification on fish behaviour, however, call this dire prediction into question. Here, we critically assess the past decade of ocean acidification research regarding direct effects on fish behaviour. Using a meta-analysis, we provide quantitative evidence that the research to date on this topic is strongly characterized by a phenomenon known as the “decline effect”, where large effects have all but disappeared over a decade. The decline effect in this field cannot be explained biologically, but is strongly associated with well-known biases to which the process of science is generally prone. We contend that ocean acidification does not have as much of a direct impact on fish behaviour as previously thought, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.

Continue reading ‘An extreme decline effect in ocean acidification ecology’

Environmentally-induced parental or developmental conditioning influences coral offspring ecological performance

The persistence of reef building corals is threatened by human-induced environmental change. Maintaining coral reefs into the future requires not only the survival of adults, but also the influx of recruits to promote genetic diversity and retain cover following adult mortality. Few studies examine the linkages among multiple life stages of corals, despite a growing knowledge of carryover effects in other systems. We provide a novel test of coral parental conditioning to ocean acidification (OA) and tracking of offspring for 6 months post-release to better understand parental or developmental priming impacts on the processes of offspring recruitment and growth. Coral planulation was tracked for 3 months following adult exposure to high pCO2 and offspring from the second month were reciprocally exposed to ambient and high pCO2 for an additional 6 months. Offspring of parents exposed to high pCO2 had greater settlement and survivorship immediately following release, retained survivorship benefits during 1 and 6 months of continued exposure, and further displayed growth benefits to at least 1 month post release. Enhanced performance of offspring from parents exposed to high conditions was maintained despite the survivorship in both treatments declining in continued exposure to OA. Conditioning of the adults while they brood their larvae, or developmental acclimation of the larvae inside the adult polyps, may provide a form of hormetic conditioning, or environmental priming that elicits stimulatory effects. Defining mechanisms of positive acclimatization, with potential implications for carry over effects, cross-generational plasticity, and multi-generational plasticity, is critical to better understanding ecological and evolutionary dynamics of corals under regimes of increasing environmental disturbance. Considering environmentally-induced parental or developmental legacies in ecological and evolutionary projections may better account for coral reef response to the chronic stress regimes characteristic of climate change.

Continue reading ‘Environmentally-induced parental or developmental conditioning influences coral offspring ecological performance’

Behavioural responses to predators in Mediterranean mussels (Mytilus galloprovincialis) are unaffected by elevated pCO2

Highlights

  • Tested effects of elevated CO2 on valve gaping responses to predator alarm cues in Mediterranean mussels.
  • Mussels reduced valve gaping in response to predator alarm cues; no change in valve movement activity.
  • Elevated CO2 had no effect on baseline behaviour nor responses to predator cues.
  • Behavioural responses to predator cues in bivalves appear robust to high CO2.

Abstract

Ocean acidification is expected to affect marine organisms in the near future. Furthermore, abrupt short-term fluctuations in seawater pCO2 characteristic of near-short coastal regions and high-density aquaculture sites currently have the potential to influence organismal and community functioning by altering animal behaviour. While anti-predator responses in fishes exposed to elevated pCO2 are well documented, such responses in benthic marine invertebrates are poorly studied. We used high frequency, non-invasive biosensors to test whether or not short term (3-week) exposure to elevated pCO2 could impact behavioural responses to the threat of predation in adult Mediterranean mussels from Galicia on the northwestern coast of Spain. Predator alarm cues (crushed conspecifics) resulted in a prolonged (1 h) reduction in the degree of valve opening (−20%) but had no clear effect on overall valve movement activity, while elevated pCO2 did not affect either response. Our results add to the increasing body of evidence suggesting that the effects of end-of-century pCO2 levels on marine animal behaviour are likely weak. Nonetheless, longer-term exposures spanning multiple generations are needed to better understand how ocean acidification might impact behavioural responses to predation in marine bivalves.

Continue reading ‘Behavioural responses to predators in Mediterranean mussels (Mytilus galloprovincialis) are unaffected by elevated pCO2’

Experimental evidence of uncertain future of the keystone ragworm Hediste diversicolor (O.F. Müller, 1776) under climate change conditions

Highlights

  • Temperature enhances the impact of acidification on polychaetes survival and burrowing behavior.
  • Regardless the temperature, acidification results in a reduction on polychaetes feeding rate
  • Faster regeneration at the lowest temperature and less regenerated chaetigers at lower pH levels
  • Climate change induced oxidative stress in H. diversicolor
  • Polychaetes metabolic capacity was enhanced in stressed organisms, with no expenditure of energy reserves.

Abstract

It is currently assumed that climate change related factors pose severe challenges to biodiversity maintenance. This paper assesses the multi-stressor effects of elevated temperature (15 °C as control, 25 °C as elevated) and CO2 levels (pH 8.1 as control, 7.5 and 7.0 representing acidifying conditions) on the physiological (survival, and regenerative capacity), behavioral (feeding and burrowing activities), and biochemical changes (metabolic capacity, oxidative status and biotransformation mechanisms) experienced by the keystone polychaete Hediste diversicolor. Temperature rise enlarged the adverse effect of marine acidification on the survival of H. diversicolor, delayed the beginning of the excavation activity, enhancing the negative effects that pH decrease had in the burrowing behavior of this polychaete. Additionally, regardless of the temperature, exposure of H. diversicolor to acidification results in a reduction in the feeding rate. It is the first time that this decreased feeding capacity is found related to seawater acidification in this species. The healing of the wound and the blastemal formation were retarded due to these two climatic factors which hinder the regenerative process of polychaetes. These vital physiological functions of H. diversicolor can be related to the oxidative stress induced by climate change conditions since free radicals overproduced will impair cells functioning affecting species biochemical and physiological performance, including feeding, and tissue regeneration. The present results also demonstrated that although polychaete’s metabolic capacity was enhanced under stress conditions, organisms were still able to increase or maintain their energy reserves. Our findings are of major environmental relevance considering that predicted climate change conditions will affect species vital and ecological and physiological capacities. These can be translated into shrinking not only at the individual and population level but also in microbial and endofaunal diversities, in the detritus processing in estuaries and biogeochemical cycles at the ecosystem level. Thus the conservation of H. diversicolor populations is vital for the normal functioning of estuarine mudflat ecosystems.

Continue reading ‘Experimental evidence of uncertain future of the keystone ragworm Hediste diversicolor (O.F. Müller, 1776) under climate change conditions’

Growth, biochemical, antioxidants, metabolic enzymes and hemocytes population of the shrimp Litopenaeus vannamei exposed to acidified seawater

Highlights

• CO2 driven ocean acidification (CDOA) might inhibit the growth of L. vannamei.

• CDOA will inhibit the biochemical, chitin and minerals in L. vannamei.

• CDOA will produce oxidative and metabolic stress in L. vannamei.

• CDOA can reduce the hemocytes level in L. vannamei.

Abstract

Acidification in the marine environment has become a global issue that creates serious threats to marine organisms. In the present study, we evaluated the effect of CO2 driven acidification on the shrimp Litopenaeus vannamei post-larvae (PL). L. vannamei PL were exposed to six different CO2 driven acidified seawater, such as pH 8.20 (control), pH 7.8 (IPCC-predicted ocean pH by 2100), 7.6, 7.4, 7.2 and 7.0 with corresponding pCO2 level of 380.66, 557.53, 878.55, 1355.48, 2129.46, and 3312.12 μatm for seven weeks. At the end of the acidification experiment, results revealed that survival, growth, feed index, biochemical constitutes, chitin, minerals (Na, K, and Ca), and hemocyte populations of shrimps were found to be significantly decreased in CO2 driven acidified seawater which indicates the negative impacts of acidified seawater on these parameters in L. vannamei. Further, the level of antioxidants, lipid peroxidation, and metabolic enzymes were significantly higher in the muscle of shrimps exposed to acidified seawater suggests that the L. vannamei under oxidative stress and metabolic stress. Among these various acidified seawater experiment, pH 7.6 to 7.0 produced a significantly adverse effect on shrimps. Hence, the present study concluded that the elevated level of seawater acidification can produce harmful effects on L. vannamei PL which leads to potential threats to shrimp species in the marine environment.

Continue reading ‘Growth, biochemical, antioxidants, metabolic enzymes and hemocytes population of the shrimp Litopenaeus vannamei exposed to acidified seawater’

Predator populations differ in their foraging responses to acute seawater acidification

Local adaptation can cause predator populations to vary in traits and their effects on prey, but few studies have tested whether divergent predator populations respond differently to acute environmental stressors. We tested how Nucella dogwhelks from 3 populations with natural exposure to distinct environmental regimes in the California Current System altered consumption of mussel prey (Mytilus californianus) in ambient (pH 8.0, 429 µatm partial pressure of CO2 [pCO2]) and acidified (pH 7.6, 1032 µatm pCO2) seawater. Overall, experimental acidification increased the variation in consumption time observed among populations. We found reduced consumption time for the population that experienced more frequent exposure to low pH conditions in nature but not for populations with less prior exposure. Exposure to acidification also altered the individual components of consumption time—search time and handling time—depending on source population. These results indicate that impaired predator performance is not a universal response to acidification, that predation responses to acute acidification can be population specific, and that individual population responses may relate to prior exposure. Our study highlights how population-specific responses to climate change can lead to differences in ecological effects that may restructure prey communities at local scales.

Continue reading ‘Predator populations differ in their foraging responses to acute seawater acidification’

Ocean acidification alters the responses of invertebrates to wound-activated infochemicals produced by epiphytes of the seagrass Posidonia oceanica

Highlights

• First time evaluation of the effect of infochemicals produced at two pH by the epiphytic community and by selected diatoms.

• O.A. alters the fine-tuned chemical cross-talks between seagrass epiphytes and associated invertebrates.

• Algae play their roles at different concentrations and convey different messages to associated animal communities.

• O.A. has consequences on the structure of associated communities and food webs of seagrass ecosystems.

Abstract

Ocean acidification (OA) influences the production of volatile organic compounds (VOCs) by seagrass leaves and their associated epiphytes. We hypothesize that the perception of “odour” produced by seagrass leaf epiphytes will change with seawater acidification, affecting the behaviour of seagrass-associated invertebrates. To test this hypothesis, we collected epiphytes from leaves of Posidonia oceanica growing at two pH conditions (7.7 and 8.1) and identified the most abundant genera of diatoms. We tested the VOCs produced at pH 8.1 by the epiphytic communities in toto, as well as those produced by selected diatoms, on various invertebrates. A complex set of species-specific and concentration-dependent chemotactic reactions was recorded, according to the pH of seawater. In particular, VOCs produced by individual diatoms triggered contrasting reactions in invertebrates, depending on the pH. The perception of epiphyte VOCs is likely to vary due to alteration of species ability to perceive and/or interpret chemical cues as infochemicals or due to changes in the structure of VOCs themselves. Thus, OA alters the fine-tuned chemical cross-talks between seagrass epiphytes and associated invertebrates, with potential consequences for the structure of communities and food webs of seagrass ecosystems.

Continue reading ‘Ocean acidification alters the responses of invertebrates to wound-activated infochemicals produced by epiphytes of the seagrass Posidonia oceanica’

Cuttlefish buoyancy in response to food availability and ocean acidification

Carbon dioxide concentration in the atmosphere is expected to continue rising by 2100, leading to a decrease in ocean pH in a process known as ocean acidification (OA). OA can have a direct impact on calcifying organisms, including on the cuttlebone of the common cuttlefish Sepia officinalis. Moreover, nutritional status has also been shown to affect the cuttlebone structure and potentially affect buoyancy. Here, we aimed to understand the combined effects of OA (980 μatm CO2) and food availability (fed vs. non-fed) on the buoyancy of cuttlefish newborns and respective cuttlebone weight/area ratio (as a proxy for calcification). Our results indicate that while OA elicited negative effects on hatching success, it did not negatively affect the cuttlebone weight/area ratio of the hatchlings—OA led to an increase in cuttlebone weight/area ratio of fed newborns (but not in unfed individuals). The proportion of “floating” (linked to buoyancy control loss) newborns was greatest under starvation, regardless of the CO2 treatment, and was associated with a drop in cuttlebone weight/area ratio. Besides showing that cuttlefish buoyancy is unequivocally affected by starvation, here, we also highlight the importance of nutritional condition to assess calcifying organisms’ responses to ocean acidification.

Continue reading ‘Cuttlefish buoyancy in response to food availability and ocean acidification’


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