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.
Posts Tagged 'annelids'
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
Impact of ocean acidification on the biogeochemistry and meiofaunal assemblage of carbonate-rich sediments: results from core incubations (Bay of Villefranche, NW Mediterranean Sea)
Published 18 May 2018 Science ClosedTags: abundance, annelids, biogeochemistry, biological response, BRcommunity, chemistry, community composition, crustaceans, kinorhyncha, laboratory, Mediterranean, nematodes, otherprocess, physiology, platyhelminthes, prokaryotes, sediment, zooplankton
Highlights
• A sediment incubation experiment to assess the effect of ocean acidification
• Porewater concentration gradients and sediment-water fluxes (DIC, TA, pH, Ca2+, O2)
• Ocean acidification impacts early diagenesis in carbonate-rich sediments.
• CaCO3 dissolution and the TA release may increase the buffering capacity of bottom water.
Abstract
Marine sediments are an important carbonate reservoir whose partial dissolution could buffer seawater pH decreases in the water column as a consequence of anthropogenic CO2 uptake by the ocean. This study investigates the impact of ocean acidification on the carbonate chemistry at the sediment-water interface (SWI) of shallow-water carbonate sediments. Twelve sediment cores were sampled at one station in the Bay of Villefranche (NW Mediterranean Sea). Four sediment cores were immediately analyzed in order to determine the initial distribution (T0) of dissolved inorganic carbon (DIC), total alkalinity (TA), pH and dissolved oxygen (O2) in the porewaters and to quantify sediment-water fluxes. Four other cores were kept submerged in the laboratory for 25 days with ambient seawater (pHT = 8.12) and the remaining four cores were incubated with acidified seawater (average pH offset of −0.68). This acidification experiment was carried out in an open-flow system, in the dark and at in-situ temperature (15 °C). Every three days, sediment-water fluxes (DIC, TA, pH, O2 and nutrients) were determined using a whole core 12-h incubation technique. Additionally, vertical O2 and pH microprofiles were regularly recorded in the first 2 cm of the sediment during the entire experiment. At the end of the experiment, TA, DIC and Ca2+ concentrations were analyzed in the porewaters and the abundance and taxonomic composition of meiofaunal organisms were assessed. The saturation states of the porewaters with respect to calcite and aragonite were over-saturated but under-saturated with respect to 12 mol% Mg-calcite, in both acidified and non-acidified treatments. The sediment-water fluxes of TA and DIC increased in the acidified treatment, likely as a consequence of enhanced carbonate dissolution. In contrast, the acidification of the overlying water did not significantly affect the O2 and nutrients fluxes at the SWI. Meiofaunal abundance decreased in both treatments over the duration of the experiment, but the organisms seemed unaffected by the acidification. Our results demonstrate that carbonate dissolution increased under acidified conditions but other parameters, such as microbial redox processes, were apparently not affected by the pH decrease, at least during the duration of our experiment. The dissolution of sedimentary carbonates and the associated release of TA may potentially buffer bottom water, depending on the intensity of the TA flux, the TA/DIC ratio, vertical mixing and, therefore, the residence time of bottom water. Under certain conditions, this process may mitigate the effect of ocean acidification on benthic ecosystems.
Tough, armed and omnivorous: Hermodice carunculata (Annelida: Amphinomidae) is prepared for ecological challenges
Published 12 April 2018 Science ClosedTags: annelids, biological response, review
The bearded fireworm, Hermodice carunculata, is a common species in the marine annelid taxon Amphinomidae. It has a widespread distribution throughout the Atlantic, Gulf of Mexico, the Caribbean, Mediterranean and Red Seas. We review its environmental tolerances, defence mechanisms and feeding habits to evaluate its potential to survive in changing ocean conditions, to increasingly emerge as a nuisance species and to invade new geographic areas. Hermodice carunculata tolerates a wide range of environmental conditions, including temperature, salinity, oxygen saturation and various types of pollution. It has few natural predators because it is protected by its sharp chaetae and probably by toxins. Hermodice carunculata is best known for consuming live cnidarians, and has been implicated in transmitting coral pathogens, but it also feeds non-selectively on detritus. In the short term, we predict that H. carunculata will be able to withstand many future ecological challenges and possibly contribute to coral reef decline. In the long term, ocean acidification may negatively impact its defence mechanisms and survival. Its invasive potential may be significant. We highlight the gaps in our knowledge about the reproduction and development of this species, the nature and origin of its toxins and role of microbes in their feeding behaviour and defensive strategies.
Effect of temperature rise and ocean acidification on growth of calcifying tubeworm shells (Spirorbis spirorbis): an in situ benthocosm approach (update)
Published 12 March 2018 Science ClosedTags: annelids, Baltic, biological response, dissolution, field, growth, mesocosms, morphology, multiple factors, temperature
The calcareous tubeworm Spirorbis spirorbis is a widespread serpulid species in the Baltic Sea, where it commonly grows as an epibiont on brown macroalgae (genus Fucus). It lives within a Mg-calcite shell and could be affected by ocean acidification and temperature rise induced by the predicted future atmospheric CO2 increase. However, Spirorbis tubes grow in a chemically modified boundary layer around the algae, which may mitigate acidification. In order to investigate how increasing temperature and rising pCO2 may influence S. spirorbisshell growth we carried out four seasonal experiments in the Kiel Outdoor Benthocosms at elevated pCO2 and temperature conditions. Compared to laboratory batch culture experiments the benthocosm approach provides a better representation of natural conditions for physical and biological ecosystem parameters, including seasonal variations. We find that growth rates of S. spirorbis are significantly controlled by ontogenetic and seasonal effects. The length of the newly grown tube is inversely related to the initial diameter of the shell. Our study showed no significant difference of the growth rates between ambient atmospheric and elevated (1100 ppm) pCO2 conditions. No influence of daily average CaCO3 saturation state on the growth rates of S. spirorbis was observed. We found, however, net growth of the shells even in temporarily undersaturated bulk solutions, under conditions that concurrently favoured selective shell surface dissolution. The results suggest an overall resistance of S. spirorbis growth to acidification levels predicted for the year 2100 in the Baltic Sea. In contrast, S. spirorbis did not survive at mean seasonal temperatures exceeding 24 °C during the summer experiments. In the autumn experiments at ambient pCO2, the growth rates of juvenile S. spirorbis were higher under elevated temperature conditions. The results reveal that S. spirorbis may prefer moderately warmer conditions during their early life stages but will suffer from an excessive temperature increase and from increasing shell corrosion as a consequence of progressing ocean acidification.
The evolution of phenotypic plasticity under global change
Published 14 December 2017 Science ClosedTags: adaptation, annelids, biological response, laboratory, morphology, mortality, multiple factors, otherprocess, physiology, reproduction, temperature
Marine ecosystems are currently in a state of flux, with ocean warming and acidification occurring at unprecedented rates. Phenotypic plasticity underpins acclimatory responses by shifting the mean phenotype in a population, which may buffer the negative effects of global change. However, little is known about how phenotypic plasticity evolves across multiple generations. We tested this by reciprocally-transplanting the polychaete Ophryotrocha labronica between control and global change scenarios (ocean warming and acidification in isolation and combined) over five generations. By comparing the reaction norms of four life-history traits across generations, we show that juvenile developmental rate in the combined scenario was the only trait that changed its plastic response across generations when transplanted back to control conditions, and that adaptive plasticity was conserved in most traits, despite significant levels of selection and strong declines in individual fitness in the multi-generational exposure. We suggest the change in level of plasticity in the combined scenario is caused by differential allocation of energy between the mean and the plasticity of the trait along the multigenerational exposure. The ability to maintain within-generational levels of plasticity under global change scenarios has important eco-evolutionary and conservation implications, which are examined under the framework of assisted evolution programs.
Continue reading ‘The evolution of phenotypic plasticity under global change’
Extreme ocean acidification reduces the susceptibility of eastern oyster shells to a polydorid parasite
Published 22 November 2017 Science ClosedTags: annelids, biological response, laboratory, mollusks, morphology, performance
Ocean acidification poses a threat to marine organisms. While the physiological and behavioural effects of ocean acidification have received much attention, the effects of acidification on the susceptibility of farmed shellfish to parasitic infections are poorly understood. Here we describe the effects of moderate (pH 7.5) and extreme (pH 7.0) ocean acidification on the susceptibility of Crassostrea virginica shells to infection by a parasitic polydorid, Polydora websteri. Under laboratory conditions, shells were exposed to three pH treatments (7.0, 7.5 and 8.0) for 3- and 5-week periods. Treated shells were subsequently transferred to an oyster aquaculture site (which had recently reported an outbreak of P. websteri) for 50 days to test for effects of pH and exposure time on P. websteri recruitment to oyster shells. Results indicated that pH and exposure time did not affect the length, width or weight of the shells. Interestingly, P. websteri counts were significantly lower under extreme (pH 7.0; ~50% reduction), but not moderate (pH 7.5; ~20% reduction) acidification levels; exposure time had no effect. This study suggests that extreme levels – but not current and projected near-future levels – of acidification (∆pH ~1 unit) can reduce the susceptibility of eastern oyster shells to P. websteri infections.
Target gene expression studies on Platynereis dumerilii and Platynereis cfr massiliensis at the shallow CO2 vents off Ischia, Italy
Published 14 November 2017 Science ClosedTags: annelids, biological response, laboratory, Mediterranean, molecular biology, physiology, vents
Many studies predict negative effects of ocean acidification on marine organisms, potentially leading to loss of biodiversity and ecosystem function. Research on species inhabiting naturally high pCO2 environments, such as volcanic CO2 vents, offers an opportunity to understand the molecular mechanisms involved in high pCO2 regulation. Here we investigate the relative expression of NADH dehydrogenase, sodium-hydrogen antiporter (NHE), carbonic anhydrase (CA) and paramyosin genes from two non-calcifying sibling Nereididae polychaetes species, Platynereis cfr massiliensis, collected in the shallow CO2 vents off Ischia (Italy; 40°43′52.0″N 13°57′46.2″E and 40°43′55.5″N 13°57′48.4″E), and P. dumerilii collected in an area nearby (40°43′34.51″N; 13°57′35.7″E). The origin of the worms was confirmed using restriction enzyme digest. NHE and paramyosin expressions were both significantly increased in P. dumerilii relative to the P. cfr massiliensis vent populations. Furthermore, a seven day laboratory transfer experiment to lower/higher pCO2 conditions was conducted to investigate the effects on the short term gene expression. The transfer experiment of the non-vent worms to high pCO2 conditions showed no significant effect on any of the genes analysed, however, two genes (NADH dehydrogenase and NHE) from worms of the vent population were significantly down-regulated under low pCO2. These findings will help to gain further insights into the cellular mechanisms affected by pCO2 changes in two polychaete species.
Effects of in situ CO2 enrichment on epibiont settlement on artificial substrata within a Posidonia oceanica meadow
Published 16 October 2017 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, community composition, crustaceans, field, Mediterranean, mollusks, otherprocess, reproduction
- Ocean acidification (OA) may cause community shifts by effecting early life stages.
- pH was lowered in situ and maintained as an offset within a FOCE setup.
- Settlement/colonization of molluscs and peracarid crustaceans were robust to OA.
- Crustose coralline algae and calcifying polychaetes were vulnerable at early life.
Alterations to colonization or early post-settlement stages may cause the reorganization of communities under future ocean acidification conditions. Yet, this hypothesis has been little tested by in situ pH manipulation. A Free Ocean Carbon Dioxide Enrichment (FOCE) system was used to lower pH by a ~ 0.3 unit offset within a partially enclosed portion (1.7 m3) of a Posidonia oceanica seagrass meadow (11 m depth) between 21 June and 3 November 2014. Epibiont colonization and early post settlement stages were assessed within the FOCE setup, as part of the larger community-level study, to better understand the outcome for a multispecies assemblage and the ecological processes that result in reported community shifts under altered carbonate chemistry. Two types of artificial collectors (tiles and scourers) were placed within three treatments: a pH-manipulated enclosure, an un-manipulated control enclosure, and an open plot in the ambient meadow. Tiles and scourers were collected after one to four months. Additionally, to see whether the outcome differed for communities in a later successional stage, previously settled scourer-collectors were also placed in the same three treatments. Enclosures acted to reduce settlement and migrant colonization. Scourers deployed for one to four months within the open-plot contained a community assemblage that could be distinguished from the assemblages within the enclosures. However, a comparison of enclosure assemblages on tiles showed evidence of a pH effect. There was lowered coverage of crustose coralline algae and fewer calcareous tube-forming polychaetes (Spirorbis sp. and Spirobranchus sp.) on tiles placed in the pH-manipulated enclosure compared to the un-manipulated enclosure. For assemblages in scourer collectors, shared and common taxa, in all treatments, were invertebrate polychaetes Psamathe fusca, Sphaerosyllis sp., Chrysopetalum sp., arthropods Harpacticoida, and Amphipoda, and the juvenile bivalve Lyonsia sp. Similar organism composition and abundance, as well as taxonomic richness and evenness, were found in scourers from both enclosures. Pre-settled scourers contained greater numbers of individuals and more calcified members, but the assemblage, as well as the growth rate of a juvenile bivalve Lyonsia sp., appeared unaffected by a two-month exposure to lowered pH and calcium carbonate saturation state. Results from this case study support the hypothesis that early stages of specific calcifiers (crustose coralline algae and calcareous tube-forming polychaetes) are sensitive to near future ocean acidification conditions yet suggest that negative effects on sessile micro-invertebrate assemblages will be minimal.
The sibling polychaetes Platynereis dumerilii and Platynereis massiliensis in the Mediterranean Sea: are phylogeographic patterns related to exposure to ocean acidification?
Published 12 September 2017 Science ClosedTags: abundance, annelids, biological response, field, Mediterranean, otherprocess, vents
High pCO2 environments, such as volcanic carbon dioxide (CO2) vents, which mimic predicted near-future scenarios of ocean acidification (OA), offer an opportunity to examine effects of low pH conditions on marine biodiversity and adaptation/acclimatization of marine organisms to such conditions. Based on previous field studies in these systems, it is predicted that the stress owing to increasing CO2 concentrations favours the colonization by invertebrate species with a brooding habit. The goal of this study was to investigate the relative occurrence of the two sibling species Platynereis dumerilii (Audouin & Milne-Edwards, 1834) (free spawner) and Platynereis massiliensis (Moquin-Tandon, 1869) (egg brooder) in two shallow CO2 vents off Ischia and Vulcano islands (Italy, Tyrrhenian Sea), and in various areas with ambient pH conditions, where they represent one of the dominant genera. Phylogeographic analyses were integrated with reproductive biology and life-history observations on some selected populations thriving in the vent areas. This approach revealed the presence of four distinct Platynereis clades. Whereas two clades primarily inhabit CO2 vents and are presumably all brooders, the other two clades dominate the non-acidified sites and appear to be epitokous free spawners. We postulate that one of the brooding, vent-inhabiting clades represents P. massiliensis and one of the free spawning, non-vent-inhabiting clades represents P. dumerilii, although confirmation of the species status with sequence data from the respective-type localities would be desirable.
Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers
Published 23 August 2017 Science ClosedTags: abundance, annelids, biological response, BRcommunity, community composition, crustaceans, echinoderms, field, Mediterranean, mollusks, otherprocess, performance, physiology, vents
Increasing oceanic uptake of CO2 is predicted to drive ecological change as both a resource (i.e. CO2 enrichment on primary producers) and stressor (i.e. lower pH on consumers). We use the natural ecological complexity of a CO2 vent (i.e. a seagrass system) to assess the potential validity of conceptual models developed from laboratory and mesocosm research. Our observations suggest that the stressor-effect of CO2enrichment combined with its resource-effect drives simplified food web structure of lower trophic diversity and shorter length. The transfer of CO2 enrichment from plants to herbivores through consumption (apparent resource-effect) was not compensated by predation, because carnivores failed to contain herbivore outbreaks. Instead, these higher-order consumers collapsed (apparent stressor-effect on carnivores) suggesting limited trophic propagation to predator populations. The dominance of primary producers and their lower-order consumers along with the loss of carnivores reflects the duality of intensifying ocean acidification acting both as resource-effect (i.e. bottom-up control) and stressor-effect (i.e. top-down control) to simplify community and trophic structure and function. This shifting balance between the propagation of resource enrichment and its consumption across trophic levels provides new insights into how the trophic dynamics might stabilize against or propagate future environmental change.
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.
Effect of ocean acidification and elevated temperature on growth of calcifying tubeworm shells (Spirorbis spirorbis): an in-situ benthocosm approach
Published 10 July 2017 Science ClosedTags: annelids, Baltic, biological response, dissolution, field, growth, mesocosms, morphology, multiple factors, temperature
The calcareous tubeworm Spirorbis spirorbis is a wide-spread serpulid species in the Baltic Sea, where it commonly grows as an epibiont on brown macroalgae (genus Fucus). It lives within a Mg-calcite shell and could be affected by ocean acidification and temperature rise induced by the predicted future atmospheric CO2 increase. However, Spirorbis tubes grow in a chemically modified boundary layer around the algae, which may mitigate acidification. In order to investigate how increasing temperature and rising pCO2 may influence S. spirorbis shell growth we carried out four seasonal experiments in the ‘Kiel Outdoor Benthocosms’ at elevated pCO2 and temperature conditions. Compared to laboratory batch culture experiments the benthocosm approach provides a better representation of natural conditions for physical and biological ecosystem parameters, including seasonal variations. We find that growth rates of S. spirorbis are significantly controlled by ontogenetic and seasonal effects. The length of the newly grown tube is inversely related to the initial diameter of the shell. Our study showed no significant difference of the growth rates between ambient atmospheric and elevated (1100 ppm) pCO2 conditions. No influence of daily average CaCO3 saturation state on the growth rates of S. spirorbiswas observed. We found, however, net growth of the shells even in temporarily undersaturated bulk solutions, under conditions that concurrently favored selective shell surface dissolution. The results suggest an overall resistance of S. spirorbis growth to acidification levels predicted for the year 2100 in the Baltic Sea. In contrast, S. spirorbis did not survive at mean seasonal temperatures exceeding 24 °C during the summer experiments. In the autumn experiments at ambient pCO2, the growth rates of juvenile S. spirorbis were higher under elevated temperature conditions. The results reveal that S. spirorbis may prefer moderately warmer conditions during their early life stages but will suffer from an excessive temperature increase and from increasing shell corrosion as a consequence of progressing ocean acidification.
Continue reading ‘Effect of ocean acidification and elevated temperature on growth of calcifying tubeworm shells (Spirorbis spirorbis): an in-situ benthocosm approach’
Impacts of ocean acidification on sperm develop with exposure time for a polychaete with long lived sperm
Published 19 June 2017 Science ClosedTags: annelids, biological response, laboratory, performance, reproduction
The majority of marine invertebrate species release eggs and sperm into seawater for external fertilisation. Seawater conditions are currently changing at an unprecedented rate as a consequence of ocean acidification (OA). Sperm are thought to be particularly vulnerable to these changes and may be exposed to external environmental conditions for variable periods of time between spawning and fertilisation. Here, we undertook a mechanistic investigation of sperm swimming performance in the coastal polychaete Arenicola marina during an extended exposure to OA conditions (pHNBS 7.77, 1000 μatm pCO2). We found that key fitness-related aspects of sperm functioning declined faster under OA conditions i.e. impacts became apparent with exposure time. Sperm swimming speed (VCL), the number of motile sperm and sperm path linearity all dropped significantly after 4 h under OA conditions whilst remaining constant under ambient conditions at this time point. Our results highlight the importance of sperm exposure duration in ocean acidification experiments and may help towards explaining species specific differences in response.
Altered epiphyte community and sea urchin diet in Posidonia oceanica meadows in the vicinity of submarine volcanic CO2 vents
Published 13 April 2017 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, community composition, echinoderms, field, Mediterranean, otherprocess, phanerogams, vents
Ocean acidification (OA) predicted for 2100 is expected to shift seagrass epiphyte communities towards the dominance of more tolerant non-calcifying taxa. However, little is known about the indirect effects of such changes on food provision to key seagrass consumers. We found that epiphyte communities of the seagrass Posidonia oceanica in two naturally acidified sites (i.e. north and south sides of a volcanic CO2 vent) and in a control site away from the vent at the Ischia Island (NW Mediterranean Sea) significantly differed in composition and abundance. Such differences involved a higher abundance of non-calcareous crustose brown algae and a decline of calcifying polychaetes in both acidified sites. A lower epiphytic abundance of crustose coralline algae occurred only in the south side of the vents, thus suggesting that OA may alter epiphyte assemblages in different ways due to interaction with local factors such as differential fish herbivory or hydrodynamics. The OA effects on food items (seagrass, epiphytes, and algae) indirectly propagated into food provision to the sea urchin Paracentrotus lividus, as reflected by a reduced P. oceanica exploitation (i.e. less seagrass and calcareous epiphytes in the diet) in favour of non-calcareous green algae in both vent sites. In contrast, we detected no difference close and outside the vents neither in the composition of sea urchin diet nor in the total abundance of calcareous versus non-calcareous taxa. More research, under realistic scenarios of predicted pH reduction (i.e. ≤ 0.32 units of pH by 2100), is still necessary to better understand cascading effects of this altered urchin exploitation of food resources under acidified conditions on ecosystem diversity and function.
Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg
Published 20 February 2017 Science ClosedTags: annelids, biological response, crustaceans, laboratory, morphology, physiology, reproduction, zooplankton
In marine invertebrates, the environmental history of the mother can influence fecundity and egg size. Acclimation of females in climate change stressors, increased temperature and low pH, results in a decrease in egg number and size in many taxa, with the exception of cephalopods, where eggs increase in size. With respect to spawned eggs, near future levels of ocean acidification can interfere with the eggs’ block to polyspermy and intracellular pH. Reduction of the extracellular egg jelly coat seen in low pH conditions has implications for impaired egg function and fertilization. Some fast generation species (e.g. copepods, polychaetes) have shown restoration of female reproductive output after several generations in treatments. It will be important to determine if the changes to egg number and size induced by exposure to climate change stressors are heritable.
Impact of predicted climate change scenarios on a coral reef meiofauna community
Published 16 January 2017 Science ClosedTags: abundance, annelids, biological response, BRcommunity, corals, crustaceans, laboratory, nematodes, otherprocess, South Atlantic, zooplankton
Changes in marine communities in response to elevated CO2 have been reported but information on how representatives of the benthic lower trophic levels will be impacted remains scarce. A laboratory experiment was conducted to evaluate the impact of different climate change scenarios on a coral reef meiofauna community. Samples of the meiofauna community were collected from the coral reef subtidal zone of Serrambi beach (Ipojuca, Pernambuco, Brazil), using artificial substrate units. The units were exposed to control treatments and to three climate change scenarios, and collected after 15 and 29 d. Important changes in the meiofauna community structure were observed after 15 d of exposure. The major meiofauna groups exhibited divergent responses to the various scenarios. Although polychaetes were negatively affected after 29 d in the most severe scenario (Scenario III), harpacticoid copepods were negatively affected in Scenarios II and III after 15 and 29 d. Harpacticoid nauplii were strongly and negatively affected in all scenarios. In contrast, Nematoda exhibited higher densities in all scenarios. To the best of our knowledge, this community-based study was the first to observe how meiofauna organisms from a coral reef environment react to the synergetic effects of reductions in seawater pH and increased temperature.
Continue reading ‘Impact of predicted climate change scenarios on a coral reef meiofauna community’
Tropical CO2 seeps reveal the impact of ocean acidification on coral reef invertebrate recruitment
Published 3 January 2017 Science ClosedTags: abundance, annelids, biological response, BRcommunity, community composition, corals, crustaceans, field, mollusks, otherprocess, protists, reproduction, South Pacific, vents, zooplankton
Highlights
- CO2 seeps at two coral reefs in Papua New Guinea were used as natural analogues of ocean acidification.
- Elevated CO2 affected recruitment in marine invertebrate communities.
- Calcified recruits of reef-dwelling Foraminifera, polychaetes, gastropods, and bivalves were vulnerable to acidification.
- Amphipods and copepods, which are important prey taxa, were adversely affected by acidification caused by elevated CO2.
Rising atmospheric CO2 concentrations are causing ocean acidification by reducing seawater pH and carbonate saturation levels. Laboratory studies have demonstrated that many larval and juvenile marine invertebrates are vulnerable to these changes in surface ocean chemistry, but challenges remain in predicting effects at community and ecosystem levels. We investigated the effect of ocean acidification on invertebrate recruitment at two coral reef CO2 seeps in Papua New Guinea. Invertebrate communities differed significantly between ‘reference’ (median pH 7.97, 8.00), ‘high CO2’ (median pH 7.77, 7.79), and ‘extreme CO2’ (median pH 7.32, 7.68) conditions at each reef. There were also significant reductions in calcifying taxa, copepods and amphipods as CO2 levels increased. The observed shifts in recruitment were comparable to those previously described in the Mediterranean, revealing an ecological mechanism by which shallow coastal systems are affected by near-future levels of ocean acidification.
Short-term effects of CO2-induced low pH exposure on target gene expression in Platynereis dumerilii
Published 7 December 2016 Science ClosedTags: annelids, biological response, laboratory, Mediterranean, molecular biology, North Atlantic, physiology
Objective: Increasing atmospheric CO2 concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii.
Methods: We investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO2 using qPCR.
Results: mRNA expression of CA in the CO2-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes.
Conclusions: Results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO2 as the inducing agents.
Can multi-generational exposure to ocean warming and acidification lead to the adaptation of life-history and physiology in a marine metazoan?
Published 1 December 2016 Science ClosedTags: adaptation, annelids, biological response, laboratory, morphology, multiple factors, otherprocess, physiology, temperature
Ocean warming and acidification are concomitant global drivers that are currently threatening the survival of marine organisms. How species will respond to these changes depends on their capacity for plastic and adaptive responses. Little is known about the mechanisms that govern plasticity and adaptability or how global changes will influence these relationships across multiple generations. Here, we exposed the emerging model marine polychaete Ophryotrocha labronica to conditions simulating ocean warming and acidification, in isolation and in combination over five generations to identify: (i) how multiple versus single global change drivers alter both juvenile and adult life-traits; (ii) the mechanistic link between adult physiological and fitness-related life-history traits; (iii) whether observed phenotypic changes observed over multiple generations are of plastic and/or adaptive origin. Two juvenile (developmental rate; survival to sexual maturity) and two adult (average reproductive body size; fecundity) life-history traits were measured in each generation, in addition to three physiological (cellular reactive oxygen species content, mitochondrial density; mitochondrial capacity) traits. We found that multi-generational exposure to warming alone caused an increase in: juvenile developmental rate, reactive oxygen species production and mitochondrial density and decreases in: average reproductive body size, fecundity and fluctuations in mitochondrial capacity, relative to control conditions. While exposure to ocean acidification alone, had only minor effects on juvenile developmental rate. Remarkably, when both drivers of global change were present, only mitochondrial capacity was significantly affected, suggesting that ocean warming and acidification act as opposing vectors of stress across multiple generations.
