Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time, we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation; however, the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats, such as sand and mud flats, seagrass beds, exposed and protected shorelines and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high or low oxygen and low or high CO2; varying pCO2 of 450 and 1300 µatm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allowed us to evaluate respiration responses of species of contrasting habitats to single and multiple stressors. Results show that respiratory responses were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will result in multiplicative effects and focus attention on alleviating hypoxia in the region.
Posts Tagged 'chordata'
Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)
Published 18 July 2018 Science ClosedTags: Baltic, biological response, chordata, crustaceans, echinoderms, laboratory, mollusks, multiple factors, North Atlantic, oxygen, physiology, respiration
Ocean acidification alters early successional coral reef communities and their rates of community metabolism
Published 31 May 2018 Science ClosedTags: algae, annelids, biological response, BRcommunity, calcification, chordata, corals, field, photosynthesis, primary production, respiration, South Pacific, vents
Ocean acidification is expected to alter community composition on coral reefs, but its effects on reef community metabolism are poorly understood. Here we document how early successional benthic coral reef communities change in situ along gradients of carbon dioxide (CO2), and the consequences of these changes on rates of community photosynthesis, respiration, and light and dark calcification. Ninety standardised benthic communities were grown on PVC tiles deployed at two shallow-water volcanic CO2 seeps and two adjacent control sites in Papua New Guinea. Along the CO2 gradient, both the upward facing phototrophic and the downward facing cryptic communities changed in their composition. Under ambient CO2, both communities were dominated by calcifying algae, but with increasing CO2 they were gradually replaced by non-calcifying algae (predominantly green filamentous algae, cyanobacteria and macroalgae, which increased from ~30% to ~80% cover). Responses were weaker in the invertebrate communities, however ascidians and tube-forming polychaetes declined with increasing CO2. Differences in the carbonate chemistry explained a far greater amount of change in communities than differences between the two reefs and successional changes from five to 13 months, suggesting community successions are established early and are under strong chemical control. As pH declined from 8.0 to 7.8, rates of gross photosynthesis and dark respiration of the 13-month old reef communities (upper and cryptic surfaces combined) significantly increased by 10% and 20%, respectively, in response to altered community composition. As a consequence, net production remained constant. Light and dark calcification rates both gradually declined by 20%, and low or negative daily net calcification rates were observed at an aragonite saturation state of <2.3. The study demonstrates that ocean acidification as predicted for the end of this century will strongly alter reef communities, and will significantly change rates of community metabolism.
Increased fitness of a key appendicularian zooplankton species under warmer, acidified seawater conditions
Published 10 January 2018 Science ClosedTags: abundance, biological response, chordata, field, laboratory, mesocosms, mortality, multiple factors, North Atlantic, otherprocess, reproduction, temperature, zooplankton
Ocean warming and acidification (OA) may alter the fitness of species in marine pelagic ecosystems through community effects or direct physiological impacts. We used the zooplanktonic appendicularian, Oikopleura dioica, to assess temperature and pH effects at mesocosm and microcosm scales. In mesocosms, both OA and warming positively impacted O. dioica abundance over successive generations. In microcosms, the positive impact of OA, was observed to result from increased fecundity. In contrast, increased pH, observed for example during phytoplankton blooms, reduced fecundity. Oocyte fertility and juvenile development were equivalent under all pH conditions, indicating that the positive effect of lower pH on O. dioica abundance was principally due to increased egg number. This effect was influenced by food quantity and quality, supporting possible improved digestion and assimilation at lowered pH. Higher temperature resulted in more rapid growth, faster maturation and earlier reproduction. Thus, increased temperature and reduced pH had significant positive impacts on O. dioica fitness through increased fecundity and shortened generation time, suggesting that predicted future ocean conditions may favour this zooplankton species.
Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios
Published 19 September 2017 Science ClosedTags: Baltic, biological response, chordata, crustaceans, echinoderms, laboratory, mollusks, multiple factors, North Atlantic, oxygen, physiology, respiration
Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios’
Natural acidification changes the timing and rate of succession, alters community structure, and increases homogeneity in marine biofouling communities
Published 7 August 2017 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, bryozoa, chemistry, chordata, community composition, field, Mediterranean, otherprocess, reproduction
Ocean acidification may have far-reaching consequences for marine community and ecosystem dynamics, but its full impacts remain poorly understood due to the difficulty of manipulating pCO2 at the ecosystem level to mimic realistic fluctuations that occur on a number of different timescales. It is especially unclear how quickly communities at various stages of development respond to intermediate-scale pCO2 change and, if high pCO2 is relieved mid-succession, whether past acidification effects persist, are reversed by alleviation of pCO2 stress, or are worsened by departures from prior high pCO2 conditions to which organisms had acclimatized. Here, we used reciprocal transplant experiments along a shallow water volcanic pCO2 gradient to assess the importance of the timing and duration of high pCO2 exposure (i.e. discrete events at different stages of successional development vs. continuous exposure) on patterns of colonization and succession in a benthic fouling community. We show that succession at the acidified site was initially delayed (less community change by eight weeks) but then caught up over the next four weeks. These changes in succession led to homogenization of communities maintained in or transplanted to acidified conditions, and altered community structure in ways that reflected both short- and longer-term acidification history. These community shifts are likely a result of interspecific variability in response to increased pCO2 and changes in species interactions. High pCO2 altered biofilm development, allowing serpulids to do best at the acidified site by the end of the experiment, although early (pre-transplant), negative effects of pCO2 on recruitment of these worms was still detectable. The ascidians Diplosoma sp. and Botryllus sp. settled later and were more tolerant to acidification. Overall, transient and persistent acidification-driven changes in the biofouling community, via both past and more recent exposure, could have important implications for ecosystem function and food web dynamics.
An integrated coral reef ecosystem model to support resource management under a changing climate
Published 20 January 2016 Science ClosedTags: abundance, algae, biological response, BRcommunity, chordata, community composition, communitymodeling, corals, fish, modeling, North Pacific, otherprocess, phytoplankton, policy, zooplankton
Millions of people rely on the ecosystem services provided by coral reefs, but sustaining these benefits requires an understanding of how reefs and their biotic communities are affected by local human-induced disturbances and global climate change. Ecosystem-based management that explicitly considers the indirect and cumulative effects of multiple disturbances has been recommended and adopted in policies in many places around the globe. Ecosystem models give insight into complex reef dynamics and their responses to multiple disturbances and are useful tools to support planning and implementation of ecosystem-based management. We adapted the Atlantis Ecosystem Model to incorporate key dynamics for a coral reef ecosystem around Guam in the tropical western Pacific. We used this model to quantify the effects of predicted climate and ocean changes and current levels of current land-based sources of pollution (LBSP) and fishing. We used the following six ecosystem metrics as indicators of ecosystem state, resilience and harvest potential: 1) ratio of calcifying to non-calcifying benthic groups, 2) trophic level of the community, 3) biomass of apex predators, 4) biomass of herbivorous fishes, 5) total biomass of living groups and 6) the end-to-start ratio of exploited fish groups. Simulation tests of the effects of each of the three drivers separately suggest that by mid-century climate change will have the largest overall effect on this suite of ecosystem metrics due to substantial negative effects on coral cover. The effects of fishing were also important, negatively influencing five out of the six metrics. Moreover, LBSP exacerbates this effect for all metrics but not quite as badly as would be expected under additive assumptions, although the magnitude of the effects of LBSP are sensitive to uncertainty associated with primary productivity. Over longer time spans (i.e., 65 year simulations), climate change impacts have a slight positive interaction with other drivers, generally meaning that declines in ecosystem metrics are not as steep as the sum of individual effects of the drivers. These analyses offer one way to quantify impacts and interactions of particular stressors in an ecosystem context and so provide guidance to managers. For example, the model showed that improving water quality, rather than prohibiting fishing, extended the timescales over which corals can maintain high abundance by at least 5–8 years. This result, in turn, provides more scope for corals to adapt or for resilient species to become established and for local and global management efforts to reduce or reverse stressors.
The impact of CO2 emissions on ‘nuisance’ marine species (video & text)
Published 6 November 2015 Science ClosedTags: algae, biological response, chordata, cnidaria, crustaceans, echinoderms, fish, mollusks, review
Anthropogenic CO2 emissions are being taken up from the atmosphere by the oceans, increasing the availability of dissolved inorganic carbon but reducing both the carbonate saturation and pH of seawater. This ocean acidification affects biological processes in a wide range of marine taxa. Here, we assess the likely responses of ‘nuisance’ species to ocean acidification, meaning those organisms that have undesirable effects from a human perspective. Based on a synthesis of evidence available to date, we predict increased growth and toxicity in harmful algal bloom species, and a significant increase in invasive algae in response to increased CO2 availability. Blooms of stinging jellyfish are also expected to increase since they are highly resilient to acidification. The effects of ocean acidification on invasive molluscs (eg, oyster drills), damaging echinoderms (eg, crown-of-thorns starfish), and a wide range of nuisance taxa will vary depending on species and location. In the USA, for example, the invasive crab Carcinus maenas is resilient to projected increases in CO2 and its impact on marine communities is expected to increase since it feeds on organisms that respond to ocean acidification with weaker defensive traits and lower recruitment. Conversely, the Red King Crab, Paralithodes camtschaticus, is adversely affected by acidification and so is expected to die back in the Barents Sea which it has invaded. Overall, we suspect that there will be an increase in nuisance species, as many have traits that are resilient to the combined warming and acidification caused by rising CO2 levels; region-specific assessments are needed to understand responses of nuisance species in local habitats. Finally, we highlight the need for targeted studies of the effects of global change on particularly harmful marine taxa such as the seaweed Caulerpa taxifolia, the starfish Asterias amurensis, several invasive ascidians, and the lionfish Pterois volitans.
Continue reading ‘The impact of CO2 emissions on ‘nuisance’ marine species (video & text)’
Acidification effects on biofouling communities: winners and losers
Published 29 January 2015 Science ClosedTags: abundance, algae, annelids, biogeochemistry, biological response, BRcommunity, chordata, community composition, laboratory, molecular biology, morphology, North Atlantic, otherprocess, porifera
How ocean acidification affects marine life is a major concern for science and society. However, its impacts on encrusting biofouling communities, that are both the initial colonizers of hard substrata and of great economic importance, are almost unknown. We showed that community composition changed significantly, from 92% spirorbids, 3% ascidians and 4% sponges initially to 47% spirorbids, 23% ascidians and 29% sponges after 100 days in acidified conditions (pH 7.7). In low pH, numbers of the spirorbid Neodexiospira pseudocorrugata were reduced ×5 compared to controls. The two ascidians present behaved differently with Aplidium sp. decreasing ×10 in pH 7.7, whereas Molgula sp. numbers were ×4 higher in low pH than controls. Calcareous sponge (Leucosolenia sp.) numbers increased ×2.5 in pH 7.7 over controls. The diatom and filamentous algal community was also more poorly developed in the low pH treatments compared to controls. Colonization of new surfaces likewise showed large decreases in spirorbid numbers, but numbers of sponges and Molgula sp. increased. Spirorbid losses appeared due to both recruitment failure and loss of existing tubes. Spirorbid tubes are comprised of a loose prismatic fabric of calcite crystals. Loss of tube materials appeared due to changes in the binding matrix and not crystal dissolution, as SEM analyses showed crystal surfaces were not pitted or dissolved in low pH conditions. Biofouling communities face dramatic future changes with reductions in groups with hard exposed exoskeletons and domination by soft-bodied ascidians and sponges.
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The effects of ocean acidification on Hawksbill sea turtles (Eretmochelys imbricata): an ecosystem approach
Published 10 April 2014 Newsletters and reports , Science ClosedTags: biological response, chordata
Hawksbill sea turtles (Eretmochelys imbricata) are listed as critically endangered by the International Union for Conservation of Nature (IUCN), with global populations demonstrating a decline of more than 80% over the past century (Troëng et al., 2005; Boden, 2008). Hawksbill sea turtles are one of the only vertebrate species that feed exclusively on sponges, relying on tropical coral reefs and their associated biodiversity for foraging grounds and shelter (Meylan, 1988; Eckert & Grobois, 2001). Coral reef ecosystems are directly threatened by ocean acidification, and may reach a point in the near future beyond which corals will no longer be the dominant benthic organisms (Hoegh-Guldberg et al., 2007; Veron, 2008). Species which supplement the hawksbill sea turtle’s diet may also be adversely affected due to their reliance on a high saturation state of aragonite and a stable pH, both of which will decline as emissions continue to rise (Kurihara, 2008). More research is needed on ecological and biological impacts of ocean acidification in order to understand how hawksbill sea turtles will respond or adapt to their changing environment.(…)
Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: an approach with mimics
Published 24 March 2014 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, bryozoa, chordata, cnidaria, community composition, crustaceans, field, Mediterranean, morphology, otherprocess, phanerogams, reproduction
Effects of ocean acidification (OA on the colonization/settlement pattern of the epibiont community of the leaves and rhizomesof the Mediterranean seagrass,Posidoniaoceanica, have been studied at volcanic CO2vents off Ischia (Italy), using “mimics”as artificial substrates. The experiments were conducted in shallowPosidoniastands (2-3 m depth), in three stations on the northand three on the south sides of the study area, distributed along a pH gradient. At each station, 4 rhizome mimics and 6 artificialleaves were collected every three months (Sept 2009-Sept 2010). The epibionts on both leaf and rhizome mimics showed clearchanges along the pH gradient; coralline algae and calcareous invertebrates (bryozoans, serpulid polychaetes and barnacles) weredominant at control stations but progressively disappeared at the most acidified stations. In these extremely low pH sites theassemblage was dominated by filamentous algae and non calcareous taxa such as hydroids and tunicates. Settlement pattern onthe artificial leaves and rhizome mimics over time showed a consistent distribution pattern along the pH gradient and highlightedthe peak of recruitment of the various organisms in different periods according to their life history.Posidoniamimics at theacidified station showed a poor and very simplified assemblage where calcifying epibionts seemed less competitive for space. Thisprofound difference in epiphyte communities in low pH conditions suggests cascading effects on the food web of the meadow and,consequently, on the functioning of the system.
Continue reading ‘Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: an approach with mimics’
Impact of ocean acidification and warming on the early ontogeny of a tropical shark
Published 11 February 2014 Science ClosedTags: biological response, chordata, growth, mortality, multiple factors, performance, physiology, reproduction, temperature
Sharks occupy high trophic levels in marine habitats and play a key role in the structure, function and health of marine ecosystems. Sharks are also one of the most threatened groups of marine animals worldwide, mostly due to overfishing and habitat degradation or loss. Although sharks have evolved to fill many ecological niches across a wide range of habitats, they have limited capability to rapidly adapt to human-induced changes in their environments. Until now, ocean acidification was not considered as a direct climate-related threat to elasmobranchs. In the present study we show, for the first time, that a long-term acclimation process of a tropical shark (Chiloscyllium punctatum) to the projected scenarios of ocean acidification (ΔpH 0.5) and warming (+4 °C) for 2100, elicited significant deleterious effects on juvenile shark’s fitness and survival. During embryogenesis, none of the parameters measured (survival, development time, yolk consumption and specific growth rate) was significantly affected by hypercapnia, with the exception of routine metabolic rates at intermediate and pre-hatching stages. However, temperature warming exposure significantly affected the embryos. The effects caused by environmental conditions, experienced throughout embryogenesis, seem to have been transmitted to the next developmental stages (juvenile sharks). This carry-over effect may play a critical role in the reductions in the fitness of sharks under climate change. Thus, it is critical to directly assess the risk and vulnerability of sharks to ocean acidification and global warming so that managers and policy-makers can proactively target the most endangered shark species.
Continue reading ‘Impact of ocean acidification and warming on the early ontogeny of a tropical shark’
