Studies on pH stress in marine animals typically focus on direct or species-specific aspects. We here test the hypothesis that a drop to pH = 7.6 indirectly affects the intra- and interspecific interactions of benthic invertebrates by means of chemical communication. We recorded fitness-relevant behaviours of small hermit crabs Diogenes pugilator, green shore crabs Carcinus maenas, and harbour ragworms Hediste diversicolor in response to short-term pH drop, and to putative stress metabolites released by conspecifics or gilt-head sea bream Sparus aurata during 30 min of acute pH drop. Not only did acute pH drop itself impair time to find a food cue in small hermit crabs and burrowing in harbour ragworms, but similar effects were observed under exposure to pH drop-induced stress metabolites. Stress metabolites from S. aurata, but not its regular control metabolites, also induced avoidance responses in all recipient species. Here, we confirm that a short-term abrupt pH drop, an abiotic stressor, has the capacity to trigger the release of metabolites which induce behavioural responses in conspecific and heterospecific individuals, which can be interpreted as a behavioural cost. Our findings that stress responses can be indirectly propagated through means of chemical communication warrant further research to confirm the effect size of the behavioural impairments caused by stress metabolites and to characterise their chemical nature.
Continue reading ‘Behavioural stress propagation in benthic invertebrates caused by acute pH drop-induced metabolites’Posts Tagged 'annelids'
Behavioural stress propagation in benthic invertebrates caused by acute pH drop-induced metabolites
Published 20 December 2021 Science ClosedTags: annelids, biological response, BRcommunity, crustaceans, fish, laboratory, North Atlantic, performance, physiology
Climate change alters shellfish reef communities: a temperate mesocosm experiment
Published 10 November 2021 Science ClosedTags: adaptation, annelids, biological response, BRcommunity, community composition, field, mesocosms, mollusks, morphology, multiple factors, otherprocess, temperature
Highlights
- Climate change will cause significant changes to rocky shore diversity.
- Outdoor mesocosms were used to test predictions of warming and ocean acidification.
- Elevated carbon dioxide in the atmosphere reduced the growth of the native mussels.
- Warming and carbon dioxide influenced the species that colonised the mussels.
Abstract
Climate change is expected to cause significant changes to rocky shore diversity. This study used outdoor mesocosms to test the predictions that warming and ocean acidification will alter the responses of native Trichomya hirsuta and introduced Mytilus galloprovincialis mussels, and their associated communities of infauna. Experiments consisted of orthogonal combinations of temperature (ambient 22 °C or elevated 25 °C), pCO2 (ambient 400 μatm or elevated 1000 μatm), mussel species (T. hirsuta or M. galloprovincialis), and mussel configuration (native, introduced, or both), with n = 3 replicates. Elevated pCO2 reduced the growth of T. hirsuta but not that of M. galloprovincialis, and warming and pCO2 influenced the infauna that colonised both species of mussels. There was a reduction in infaunal molluscs and an increase in polychaetes; there was, however, no effect on crustaceans. Results from this study suggest that climate-driven changes from one mussel species to another can significantly influence infaunal communities.
Continue reading ‘Climate change alters shellfish reef communities: a temperate mesocosm experiment’Biodiversity of coral reef cryptobiota shuffles but does not decline under the combined stressors of ocean warming and acidification
Published 21 September 2021 Science ClosedTags: annelids, biological response, cnidaria, community composition, corals, echinoderms, laboratory, mesocosms, molecular biology, mollusks, multiple factors, North Pacific, otherprocess, porifera, temperature
Significance
Although climate change is expected to decimate coral reefs, the combined impacts of ocean-warming and acidification on coral reef biodiversity remains largely unmeasured. Here, we present a two-year mesocosm experiment to simulate future ocean acidification and ocean-warming to quantify the impacts on species richness, community composition, and community structure. We find that species richness is equivalent between the dual-stressor and present-day treatments but that the community shuffles, undoubtedly altering ecosystem function. However, our ability to predict the outcomes of such community shuffling remains limited due to the critical knowledge gap regarding ecological functions, life histories, and distributions for most members of the cryptobenthic community that account for the majority of the biodiversity within these iconic ecosystems.
Abstract
Ocean-warming and acidification are predicted to reduce coral reef biodiversity, but the combined effects of these stressors on overall biodiversity are largely unmeasured. Here, we examined the individual and combined effects of elevated temperature (+2 °C) and reduced pH (−0.2 units) on the biodiversity of coral reef communities that developed on standardized sampling units over a 2-y mesocosm experiment. Biodiversity and species composition were measured using amplicon sequencing libraries targeting the cytochrome oxidase I (COI) barcoding gene. Ocean-warming significantly increased species richness relative to present-day control conditions, whereas acidification significantly reduced richness. Contrary to expectations, species richness in the combined future ocean treatment with both warming and acidification was not significantly different from the present-day control treatment. Rather than the predicted collapse of biodiversity under the dual stressors, we find significant changes in the relative abundance but not in the occurrence of species, resulting in a shuffling of coral reef community structure among the highly species-rich cryptobenthic community. The ultimate outcome of altered community structure for coral reef ecosystems will depend on species-specific ecological functions and community interactions. Given that most species on coral reefs are members of the understudied cryptobenthos, holistic research on reef communities is needed to accurately predict diversity–function relationships and ecosystem responses to future climate conditions.
Continue reading ‘Biodiversity of coral reef cryptobiota shuffles but does not decline under the combined stressors of ocean warming and acidification’DNA metabarcoding to examine the biodiversity of coral reef cryptobiota
Published 3 August 2021 Science ClosedTags: algae, annelids, biological response, BRcommunity, cnidaria, community composition, corals, echinoderms, laboratory, mesocosms, molecular biology, mollusks, multiple factors, North Pacific, porifera, reproduction, temperature
Coral reefs are among the most biologically diverse, complex, and productive of ecosystems. The vast majority of coral reef biodiversity is made up of the small and cryptic organisms living unseen by most within the reef matrix. This hidden community, the cryptobiota, are a critical component of coral reef trophic dynamics and play an essential role in nutrient recycling that enable reefs to thrive in oligotrophic environments. Despite their ecological importance, the cryptobiota are often ignored because they live deep within the reef matrix and require significant taxonomic expertise and time to collect and identify. As a result, our perceptions of coral reef biodiversity across marine gradients and how it will respond to climatic change is based on observable surface-dwelling taxa, such as corals and fish. Using DNA metabarcoding technology, this research fills an extensive knowledge gap about the diversity and distribution of the important and understudied coral reef cryptobiota community. The objectives of this dissertation were to (i) evaluate metabarcoding performance on marine sponges, a prominent and ecologically vital member of the cryptobenthos that is one of the most difficult metazoans to identify to species using both taxonomic and molecular methods; (ii) investigate the individual and combined effects of ocean warming and acidification on cryptobiota biodiversity; and (iii) examine cryptobiota diversity along the most striking macrospatial diversity gradient in the marine tropics. Contrary to expectations, this research (i) demonstrated that the metabarcoding approach performs much better than expected in capturing sponge richness; (ii) discovered that diversity shuffles but does not decline under the combined stressors of ocean warming and acidification; and (iii) cryptobiotic diversity undermines the tropical Pacific longitudinal diversity gradient defined by corals and fish. These results contribute towards reshaping the way we consider coral reef biodiversity under different oceanographic, geographic and climatic regimes.
Continue reading ‘DNA metabarcoding to examine the biodiversity of coral reef cryptobiota’Role of behaviour in marine organisms: potential effects under future ocean conditions
Published 30 July 2021 Science ClosedTags: annelids, biological response, chemistry, field, fish, laboratory, Mediterranean, morphology, multiple factors, performance, reproduction, temperature
Over the last 250 years, the intensive burning of fossil fuels along with industrial processes and land uses (e.g. clearing forests and agriculture) has contributed to an increase in atmospheric CO2 from approximately 280 to 410 ppm, with a further increase (from 730 to 1020 ppm) projected by the end of this century. About 30% of the anthropogenic CO2 has been absorbed by the ocean, with a consequent decrease of the ocean’s surface pH causing a phenomenon better known as Ocean Acidification (OA). The average pH of the surface ocean has declined from 8.2 by 0.1 units since pre-industrial times as a result of CO2 emissions and a further reduction of 0.3–0.5 pH units is expected to occur by the 2100.
This increased concentration of atmospheric CO2 has driven an increase in atmospheric and oceanic temperatures enhanced at a rate of ~ 0.2˚C per decade in the past 30 years. These rapid changing ocean conditions in pCO2 and temperature are considered two of the major threats to marine biodiversity, leading to changes in the distribution, physiology and behaviour of marine organisms, with potential consequences in community and ecosystem functioning and structure. Despite the increasing interest and amount of literature on this topic, the effects of OA and ocean warming (OW) on marine fauna is difficult to predict, especially because a wide range of impacts have been found across different life stages-and species suggesting that tolerance thresholds to such stressors can vary among life stages experienced by an organism or even between species. In this regard, an increased number of studies has been conducted to better understand the mechanisms by which species can cope with these rapid environmental changes.
The first response of animals to a changing environment is predominantly through modification of their behaviour. To date, only a few climate change biology studies have considered behavioural plasticity as a way that animals can adjust their performance under rapid climate change, especially for marine ectotherms.
The general objective of this thesis was to evaluate the effects of ocean warming and acidification on different aspects of behaviour in marine ectotherms. To achieve this aim I investigated the behavioural responses of two marine fish and one invertebrate, through field-based and laboratory experiments.
Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers
Published 3 June 2021 Science ClosedTags: algae, annelids, biogeochemistry, biological response, calcification, cnidaria, crustaceans, echinoderms, growth, individualmodeling, laboratory, mollusks, paleo, performance, photosynthesis, physiology, reproduction
Elemental ratios in biogenic marine calcium carbonates are widely used in geobiology, environmental science, and paleoenvironmental reconstructions. It is generally accepted that the elemental abundance of biogenic marine carbonates reflects a combination of the abundance of that ion in seawater, the physical properties of seawater, the mineralogy of the biomineral, and the pathways and mechanisms of biomineralization. Here we report measurements of a suite of nine elemental ratios (Li/Ca, B/Ca, Na/Ca, Mg/Ca, Zn/Ca, Sr/Ca, Cd/Ca, Ba/Ca, and U/Ca) in 18 species of benthic marine invertebrates spanning a range of biogenic carbonate polymorph mineralogies (low-Mg calcite, high-Mg calcite, aragonite, mixed mineralogy) and of phyla (including Mollusca, Echinodermata, Arthropoda, Annelida, Cnidaria, Chlorophyta, and Rhodophyta) cultured at a single temperature (25°C) and a range of pCO2 treatments (ca. 409, 606, 903, and 2856 ppm). This dataset was used to explore various controls over elemental partitioning in biogenic marine carbonates, including species-level and biomineralization-pathway-level controls, the influence of internal pH regulation compared to external pH changes, and biocalcification responses to changes in seawater carbonate chemistry. The dataset also enables exploration of broad scale phylogenetic patterns of elemental partitioning across calcifying species, exhibiting high phylogenetic signals estimated from both uni- and multivariate analyses of the elemental ratio data (univariate: λ = 0–0.889; multivariate: λ = 0.895–0.99). Comparing partial R2 values returned from non-phylogenetic and phylogenetic regression analyses echo the importance of and show that phylogeny explains the elemental ratio data 1.4–59 times better than mineralogy in five out of nine of the elements analyzed. Therefore, the strong associations between biomineral elemental chemistry and species relatedness suggests mechanistic controls over element incorporation rooted in the evolution of biomineralization mechanisms.
Continue reading ‘Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers’Reduced seawater pH alters marine biofilms with impacts for marine polychaete larval settlement
Published 2 March 2021 Science ClosedTags: annelids, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, physiology, prokaryotes, protists, reproduction, substrate
Highlights
• Reduced seawater pH strongly influences biofilm community composition, at both eukaryotic and prokaryotic level
• For older biofilms, biofilm age plays no role in community composition
• Incubation under different pH treatments results in variations in apparent colour and structural complexity of marine biofilms
• Incubation of marine biofilms under different pH treatments alters the settlement response in marine invertebrates
• The changes in marine biofilm community composition induced by seawater pH are most likely responsible for the changes observed in invertebrate settlement selectivity
Abstract
Ocean acidification (OA) can negatively affect early-life stages of marine organisms, with the key processes of larval settlement and metamorphosis potentially vulnerable to reduced seawater pH. Settlement success depends strongly on suitable substrates and environmental cues, with marine biofilms as key settlement inducers for a range of marine invertebrate larvae. This study experimentally investigated (1) how seawater pH determines growth and community composition of marine biofilms, and (2) whether marine biofilms developed under different pH conditions can alter settlement success in the New Zealand serpulid polychaete Galeolaria hystrix. Biofilms were developed under six pH(T) treatments (spanning from 7.0 to 8.1 [ambient]) in a flow-through system for up to 14 months. Biofilms of different ages (7, 10 and 14 months) were used to assay successful settlement of competent G. hystrix larvae reared under ambient conditions. Biofilm microbiomes were characterized through amplicon sequencing of the small subunit ribosomal rRNA gene (16S and 18S). Biofilm community composition was stable over time within each pH treatment and biofilm age did not affect larval settlement selectivity. Seawater pH treatment strongly influenced biofilm community composition, as well as subsequent settlement success when biofilms were presented to competent Galeolaria larvae. Exposure to biofilms incubated under OA-treatments caused a decrease in larval settlement of up to 40% compared to the ambient treatments. We observed a decrease in settlement on biofilms relative to ambient pH for slides incubated at pH 7.9 and 7.7. This trend was reversed at pH 7.4, resulting in high settlement, comparable to ambient biofilms. Settlement decreased on biofilms from pH 7.2, and no settlement was observed on biofilms from pH 7.0. For the first time, we show that long-term incubation of marine biofilms under a wide range of reduced seawater pH treatments can alter marine biofilms in such a way that settlement success in marine invertebrates can be compromised.
Continue reading ‘Reduced seawater pH alters marine biofilms with impacts for marine polychaete larval settlement’Volcanic CO2 seep geochemistry and use in understanding ocean acidification
Published 15 December 2020 Science ClosedTags: abundance, algae, annelids, biogeochemistry, BRcommunity, bryozoa, chemistry, cnidaria, community composition, corals, crustaceans, echinoderms, field, fish, Mediterranean, mollusks, otherprocess, phanerogams, phytoplankton, polychaetes, protists, review, vents
Ocean acidification is one of the most dramatic effects of the massive atmospheric release of anthropogenic carbon dioxide (CO2) that has occurred since the Industrial Revolution, although its effects on marine ecosystems are not well understood. Submarine volcanic hydrothermal fields have geochemical conditions that provide opportunities to characterise the effects of elevated levels of seawater CO2 on marine life in the field. Here, we review the geochemical aspects of shallow marine CO2-rich seeps worldwide, focusing on both gas composition and water chemistry. We then describe the geochemical effects of volcanic CO2 seepage on the overlying seawater column. We also present new geochemical data and the first synthesis of marine biological community changes from one of the best-studied marine CO2 seep sites in the world (off Vulcano Island, Sicily). In areas of intense bubbling, extremely high levels of pCO2 (> 10,000 μatm) result in low seawater pH (< 6) and undersaturation of aragonite and calcite in an area devoid of calcified organisms such as shelled molluscs and hard corals. Around 100–400 m away from the Vulcano seeps the geochemistry of the seawater becomes analogous to future ocean acidification conditions with dissolved carbon dioxide levels falling from 900 to 420 μatm as seawater pH rises from 7.6 to 8.0. Calcified species such as coralline algae and sea urchins fare increasingly well as sessile communities shift from domination by a few resilient species (such as uncalcified algae and polychaetes) to a diverse and complex community (including abundant calcified algae and sea urchins) as the seawater returns to ambient levels of CO2. Laboratory advances in our understanding of species sensitivity to high CO2 and low pH seawater, reveal how marine organisms react to simulated ocean acidification conditions (e.g., using energetic trade-offs for calcification, reproduction, growth and survival). Research at volcanic marine seeps, such as those off Vulcano, highlight consistent ecosystem responses to rising levels of seawater CO2, with the simplification of food webs, losses in functional diversity and reduced provisioning of goods and services for humans.
Continue reading ‘Volcanic CO2 seep geochemistry and use in understanding ocean acidification’Seawater acidification affects beta-diversity of benthic communities at a shallow hydrothermal vent in a Mediterranean marine protected area (underwater archaeological park of Baia, Naples, Italy)
Published 10 December 2020 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, community composition, crustaceans, field, Mediterranean, nematodes, otherprocess, vents
One of the most important pieces of climate change evidence is ocean acidification. Acidification effects on marine organisms are widely studied, while very little is known regarding its effects on assemblages’ β-diversity. In this framework, shallow hydrothermal vents within a Marine Protected Area (MPA) represent natural ecosystems acting as laboratory set-ups where the continuous carbon dioxide emissions affect assemblages with consequences that can be reasonably comparable to the effects of global water acidification. The aim of the present study is to test the impact of seawater acidification on the β-diversity of soft-bottom assemblages in a shallow vent field located in the Underwater Archeological Park of Baia MPA (Gulf of Naples, Mediterranean Sea). We investigated macro- and meiofauna communities of the ‘Secca delle fumose’ vent system in sites characterized by sulfurous (G) and carbon dioxide emissions (H) that are compared with control/inactive sites (CN and CS). Statistical analyses were performed on the most represented macrobenthic (Mollusca, Polychaeta, and Crustacea), and meiobenthic (Nematoda) taxa. Results show that the lowest synecological values are detected at H and, to a lesser extent, at G. Multivariate analyses show significant differences between hydrothermal vents (G, H) and control/inactive sites; the highest small-scale heterogeneities (measure of β-diversity) are detected at sites H and G and are mainly affected by pH, TOC (Total Organic Carbon), and cations concentrations. Such findings are probably related to acidification effects, since MPA excludes anthropic impacts. In particular, acidification markedly affects β-diversity and an increase in heterogeneity among sample replicates coupled to a decrease in number of taxa is an indicator of redundancy loss and, thus, of resilience capacity. The survival is assured to either tolerant species or those opportunistic taxa that can find good environmental conditions among gravels of sand.
Continue reading ‘Seawater acidification affects beta-diversity of benthic communities at a shallow hydrothermal vent in a Mediterranean marine protected area (underwater archaeological park of Baia, Naples, Italy)’Current and future trophic interactions in tropical shallow-reef lagoon habitats
Published 29 October 2020 Science ClosedTags: annelids, biological response, BRcommunity, chemistry, community composition, crustaceans, echinoderms, field, laboratory, multiple factors, nematodes, otherprocess, performance, South Pacific, zooplankton
Calcium carbonate (CaCO3) sediments are the dominant form of CaCO3 on coral reefs accumulating in lagoon and inter-reefal areas. Owing to their mineralogy and a range of physical parameters, tropical CaCO3 sediments are predicted to be more sensitive to dissolution driven by ocean acidification than the skeleton of living reef organisms. How this scales up to impact infaunal organisms, which are an important food source for higher trophic levels, and thereby ecosystem functioning, is not well explored. We combined seasonal field surveys in a shallow-reef lagoon ecosystem on the Great Barrier Reef, Australia, with stable isotope analyses and a tank-based experiment to examine the potential top-down influence of the deposit-feeding sea cucumber, Stichopus herrmanni, on this infaunal community under current and future ocean pH. Densities of surface-sediment meiofauna were lowest in winter and spring, with harpacticoid copepods (38%) and nematodes (27%) the dominant taxa. Stable isotope analyses showed that S. herrmanni had a top-down influence on meiofauna and microphytes with a distinct δ13C and δ15N trophic position that was homogenous across seasons and locations. Tanks that mimicked sandy shallow-reef lagoon habitats were used to examine the effects of ocean acidification (elevated pCO2) on this trophic interaction. We used outdoor control (sediment only) and experimental (sediment plus S. herrmanni) tanks maintained at present-day and near-future pCO2 (+ 570 µatm) for 24 days, which fluctuated with the diel pCO2 cycle. In sediment-only tanks, copepods were > twofold more abundant at elevated pCO2, with no negative effects documented for any meiofauna group. When included in the community, top-down control by S. herrmanni counteracted the positive effects of low pH on meiofaunal abundance. We highlight a novel perspective in coral reef trophodynamics between surface-sediment meiofauna and deposit-feeding sea cucumbers, and posit that community shifts may occur in shallow-reef lagoon habitats in a future ocean with implications for the functioning of coral reefs from the bottom up.
Continue reading ‘Current and future trophic interactions in tropical shallow-reef lagoon habitats’Experimental evidence of uncertain future of the keystone ragworm Hediste diversicolor (O.F. Müller, 1776) under climate change conditions
Published 3 September 2020 Science ClosedTags: annelids, biological response, laboratory, morphology, mortality, multiple factors, otherprocess, performance, physiology, temperature
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.
Multimarker response of the ragworm Hediste diversicolor (Polychaeta) to seawater acidification derived from potential CO2 leakage from the CCS sub-seabed storage site in the Baltic Sea
Published 24 July 2020 Science ClosedTags: annelids, Baltic, biological response, laboratory, morphology, physiology
Highlights
• Seawater acidification affected physiological traits, LPO and growth of Hediste diversicolor from the southern Baltic Sea.
• Moderate hypercapnia (pH 7.5–7.1) induced an increase in metabolic rate of the polychaetes and a decline of their growth.
• The most acidic environment (pH 6.5) caused metabolic slow down limiting energy turnover and growth.
• Reduced seawater pH did not impact energetic reserves so, proteins were not used as substrates under acidic conditions.
• High tolerance of the ragworms to hypercapnia stems probably from pre-adaptation to natural pH reduction events in sediment.
Abstract
Sub-seabed Carbon Capture and Storage (CCS) is conceived as safe technology with small likehood of negative consequences to the marine ecosystem but CO2 escape from geological reservoir still poses potential environmental risk. If carbon dioxide leakage occurs carbonate chemistry in the bottom zone and sessile benthic fauna are expected to be the most likely affected by elevated levels of CO2. Though generic mechanisms and advisory conclusions on the presumable impact of increased acidity on the marine benthic biota were formulated they cannot be applied uniformly across different environmental variables as specific local conditions may alter biological response to hypercapnia. A laboratory experiment was conducted to quantify the effects of medium-term (8 wk) exposure to seawater acidification (pH 7.7–6.5) on the infaunal polychaete Hediste diversicolor from the southern Baltic Sea using multimarker approach. Under moderate acidity (pH 7.5 and 7.1) the polychaetes were found to increase metabolic rate (by 13.4% and 19.6%, respectively) and reduce their body mass (by 8.1% and 5.5% wet weight, respectively and by 6.1% and 3.0% dry weight, respectively) whilst enhancing synthesis of antioxidant malondialdehyde (by 22.8% and 65.3%, respectively). In the most acidic environment (pH 6.5) the ragworms showed overall metabolic slow down (by 34.8%) and impaired growth (e.g. by 10.2% for length of the first three segments) indicative of low vulnerability to hypercapnia. High implicit tolerance of the polychaetes to increased acidity in the environment stems inevitably from a certain level of pre-adaptation to pH reduction events which occur in organic-rich stratified sediments due to intense aerobic biomineralization leading often to oxygen depletion and formation of toxic hydrogen sulphide. Acidification did not affect energetic reserves suggesting that costs of acid-base maintenance were covered mainly from assimilated food and that proteins were not used as metabolic substrates.
Ocean acidification alters the responses of invertebrates to wound-activated infochemicals produced by epiphytes of the seagrass Posidonia oceanica
Published 20 July 2020 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, crustaceans, laboratory, Mediterranean, mollusks, morphology, otherprocess, performance, phytoplankton
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.
Evolutionary links between intra‐ and extracellular acid–base regulation in fish and other aquatic animals
Published 8 June 2020 Science ClosedTags: algae, annelids, biogeochemistry, biological response, calcification, fish, photosynthesis, physiology, review
The acid–base relevant molecules carbon dioxide (CO2), protons (H+), and bicarbonate (HCO3−) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid–base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO2, H+, and HCO3− have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways. Life in aquatic environments presents organisms with distinct acid–base challenges that are not found in terrestrial environments. These include a relatively high CO2 relative to O2 solubility that prevents internal CO2/HCO3− accumulation to buffer pH, a lower O2 content that may favor anaerobic metabolism, and variable environmental CO2, pH and O2 levels that require dynamic adjustments in acid–base homeostatic mechanisms. Additionally, some aquatic animals purposely create acidic or alkaline microenvironments that drive specialized physiological functions. For example, acidifying mechanisms can enhance O2 delivery by red blood cells, lead to ammonia trapping for excretion or buoyancy purposes, or lead to CO2 accumulation to promote photosynthesis by endosymbiotic algae. On the other hand, alkalinizing mechanisms can serve to promote calcium carbonate skeletal formation. This nonexhaustive review summarizes some of the distinct acid–base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.
Continue reading ‘Evolutionary links between intra‐ and extracellular acid–base regulation in fish and other aquatic animals’Toward a mechanistic understanding of marine invertebrate behavior at elevated CO2
Published 5 June 2020 Science ClosedTags: annelids, biological response, BRcommunity, cnidaria, crustaceans, echinoderms, fish, mollusks, performance, physiology, reproduction, review
Elevated carbon dioxide (CO2) levels can alter ecologically important behaviors in a range of marine invertebrate taxa; however, a clear mechanistic understanding of these behavioral changes is lacking. The majority of mechanistic research on the behavioral effects of elevated CO2 has been done in fish, focusing on disrupted functioning of the GABAA receptor (a ligand-gated ion channel, LGIC). Yet, elevated CO2 could induce behavioral alterations through a range of mechanisms that disturb different components of the neurobiological pathway that produces behavior, including disrupted sensation, altered behavioral choices and disturbed LGIC-mediated neurotransmission. Here, we review the potential mechanisms by which elevated CO2 may affect marine invertebrate behaviors. Marine invertebrate acid–base physiology and pharmacology is discussed in relation to altered GABAA receptor functioning. Alternative mechanisms for behavioral change at elevated CO2 are considered and important topics for future research have been identified. A mechanistic understanding will be important to determine why there is variability in elevated CO2-induced behavioral alterations across marine invertebrate taxa, why some, but not other, behaviors are affected within a species and to identify which marine invertebrates will be most vulnerable to rising CO2 levels.
Energetic context determines species and community responses to ocean acidification
Published 23 April 2020 Science ClosedTags: abundance, annelids, biological response, BRcommunity, bryozoa, chordata, field, laboratory, mesocosms, mollusks, morphology, multiple factors, North Pacific, nutrients, otherprocess, performance, protists
Physiological responses to ocean acidification are thought to be related to energetic trade‐offs. Although a number of studies have proposed that negative responses to low pH could be minimized in situations where food resources are more readily available, evidence for such effects on individuals remain mixed, and the consequences of such effects at the community level remain untested. We explored the potential for food availability and diet quality to modify the effects of acidification on developing marine fouling communities in field‐deployed mesocosms by supplementing natural food supply with one of two species of phytoplankton, differing in concentration of fatty acids. After twelve weeks, no species demonstrated the interactive effects generally predicted in the literature, where a positive overall effect of diet mitigated the negative overall effects of acidification. Rather, for some species, additional food supply appeared to bring out or exacerbate the negative effects of low pH. Community richness and structure were only altered by acidification, while space occupation and evenness reflected patterns of the most dominant species. Importantly, we find that acidification stress can increase the relative abundance of invasive species, even under resource conditions that otherwise prevented invasive species establishment. Overall, the proposed hypothesis regarding the ability for food addition to mitigate the negative effects of acidification is thus far not widely supported at species or community levels. It is clear that acidification is a strong driving force in these communities but understanding underlying energetic and competitive context is essential to developing mechanistic predictions for climate change responses.
Transcriptome analysis of the Nematode Caenorhabditis elegans in acidic stress environments
Published 13 March 2020 Science ClosedTags: annelids, biological response, laboratory, molecular biology
Ocean acidification and acid rain, caused by modern industrial fossil fuels burning, lead to decrease of living environmental pH, which results in a series of negative effects on many organisms. However, the underlying mechanisms of animals’response to acidic pH stress are largely unknown. In this study, we used the nematode Caenorhabditis elegans as an animal model to explore the regulatory mechanisms of organisms’response to pH decline. Two major stress-responsive pathways were found through transcriptome analysis in acidic stress environments. Firstly, when the pH dropped from 6.33 to 4.33, the worms responded to the pH stress by up-regulation of the col, nas and dpy genes, which are required for cuticle synthesis and structure integrity. Secondly, when the pH continued to decrease from 4.33, the metabolism of xenobiotics by cytochrome P450 pathway genes (cyp, gst, ugt, and ABC transporters) played a major role in protecting the nematodes from the toxic substances probably produced by the more acidic environment. At the same time, cuticle synthesis slowed down might due to its insufficient protective ability. Moreover, the systematic regulation pattern we found in nematodes, might also be applied to other invertebrate and vertebrate animals to survive in the changing pH environments. Thus, our data might lay the foundation to identify the master gene(s) responding and adaptation to acidic pH stress in further studies, and might also provide new solutions to improve assessment and monitoring of ecological restoration outcomes, or generate novel genotypes via genome editing for restoring in challenging environments especially in the context of acidic stress through global climate change.
Within- and trans-generational responses to combined global changes are highly divergent in two congeneric species of marine annelids
Published 13 March 2020 Science ClosedTags: annelids, biological response, growth, laboratory, Mediterranean, morphology, mortality, multiple factors, physiology, reproduction, temperature
Trans-generational plasticity (TGP) represents a primary mechanism for guaranteeing species persistence under rapid global changes. To date, no study on TGP responses of marine organisms to global change scenarios in the ocean has been conducted on phylogenetically closely related species, and we thus lack a true appreciation for TGP inter-species variation. Consequently, we examined the tolerance and TGP of life-history and physiological traits in two annelid species within the genus Ophryotrocha: one rare (O. robusta) and one common (O. japonica). Both species were exposed over two generations to ocean acidification (OA) and warming (OW) in isolation and in combination (OAW). Warming scenarios led to a decrease in energy production together with an increase in energy requirements, which was lethal for O. robusta before viable offspring could be produced by the F1. Under OA conditions, O. robusta was able to reach the second generation, despite showing lower survival and reproductive performance when compared to control conditions. This was accompanied by a marked increase in fecundity and egg volume in F2 females, suggesting high capacity for TGP under OA. In contrast, O. japonica thrived under all scenarios across both generations, maintaining its fitness levels via adjusting its metabolomic profile. Overall, the two species investigated show a great deal of difference in their ability to tolerate and respond via TGP to future global changes. We emphasize the potential implications this can have for the determination of extinction risk, and consequently, the conservation of phylogenetically closely related species.
