Ocean acidification, a direct consequence of increasing carbon dioxide (CO2) emissions, is a pressing environmental issue that has far-reaching implications for marine ecosystems (Doney et al., 2009). The oceans absorb approximately one-third of the CO2 produced by human activities, leading to decreased seawater pH, a process known as ocean acidification (Rodriguez, 2012). This phenomenon has been identified as a significant threat to marine life, mainly invertebrates such as mollusks, echinoderms, and crustaceans, which rely on carbonate ions to build their shells and skeletons (Guinotte and Fabry, 2008; Doney et al., 2020).
Continue reading ‘Chapter 6 – Impacts of ocean acidification on the behavior of marine mollusks’Posts Tagged 'performance'
Chapter 6 – Impacts of ocean acidification on the behavior of marine mollusks
Published 22 October 2024 Science ClosedTags: biological response, BRcommunity, laboratory, mollusks, performance
Ecophysiology and ocean acidification in marine mollusks: from molecule to behavior
Published 17 October 2024 Science ClosedTags: biological response, education, growth, mollusks, morphology, performance, physiology, reproduction, review, socio-economy
Ecophysiology and Ocean Acidification in Marine Mollusks: From Molecule to Behavior provides an extensive overview of the latest research on the various ecophysiological effects of ocean acidification on marine mollusks. This book synthesizes historical information and recent findings on the effects of environmental change, ocean warming, and acidification on key mollusks and their life-history. It also discusses the underlying mechanisms underpinning the effects of ocean warming and acidification. Written by internationally recognized experts in the field of marine biology, this book systematically examines the effects of ocean acidification on the reproduction, growth and development, physiological metabolism, immunity, and behavior of marine mollusks.
The book concludes by discussing the implications of current research, acknowledging data limitations in the field, and proposing future research directions, providing a better understanding of the potential impacts of ocean acidification on mollusks and the global aquaculture industry and inspiring new thinking for future research practices. It will be an indispensable resource for researchers, practitioners, undergraduate and graduate students, conservationists, and aquaculturists alike who are interested in marine environmental change, ecology, physiology, and marine biology.
Continue reading ‘Ecophysiology and ocean acidification in marine mollusks: from molecule to behavior’Mutligenerational chronic exposure to near future ocean acidification in European sea bass (Dicentrarchus labrax): insights into the regulation of the transcriptome in a sensory organ involved in feed intake, the tongue
Published 10 October 2024 Science ClosedTags: biological response, BRcommunity, fish, laboratory, molecular biology, performance, physiology
Highlights
- Multigenerational exposure to OA has no impact on teeth mineralization in Sea bass.
- Of the 18703 genes expressed in the tongue, 295 exhibited OA-induced regulation.
- Genes related to cell stress, immune system and fatty acid sensitivity are regulated.
- OA impacts the branchial expression of p2ry4 gene involved in gustatory system.
Abstract
In this study, we examined the effect of near future ocean acidification (OA) on the transcriptome of a sensory organ in contact with surrounding water, the tongue in adult European sea bass (Dicentrarchus labrax) by mean of RNAseq experiment. We acquired a total of 14.1 Mb quality-trimmed reads covering 18,703 expressed genes from the tongue of fish reared from two generations at actual (pH 8.0 condition) and predicted near-future seawater pH (pH 7.6 condition). Gene ontologies analyses of expressed genes support the evidence that the tongue exhibits biological processes related to the sensory system, tooth mineralization and immune defences among others. Our data revealed only 295 OA-induced regulated genes with 114 up- and 181 down-regulated by OA. Functions over-represented encompass processes involved in organic substance metabolic process, RNA metabolism and especially RNA methylation which, combined with the regulation of some hsp genes expression, suggest a molecular response to stress which might contribute to lingual cell homeostasis under OA. The immune system process is also found enriched within OA-induced regulated genes. With the exception of one fatty acid receptor, known taste perception effectors were not impacted by OA in the tongue. However, a complementary droplet digital PCR approach dedicated to genes involved in gustatory signal transduction revealed the down regulation by OA of pyrimidinergic receptor (p2ry4) transcript expression in the gills of the fish. Combined with scanning electron microscopy analysis, our RNAseq data revealed that OA has no impact on processes related to teeth development and mineralization. Altogether, our data reveal that multigenerational exposure to OA has not a substantially effect on the tongue transcriptome but emphasis should be placed on investigating the potential physiological consequences related to the regulation of genes related to cell stress, immune system and fatty acid sensitivity to conclude on species resilience in face of OA.
Continue reading ‘Mutligenerational chronic exposure to near future ocean acidification in European sea bass (Dicentrarchus labrax): insights into the regulation of the transcriptome in a sensory organ involved in feed intake, the tongue’Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum
Published 26 September 2024 Science ClosedTags: biological response, BRcommunity, growth, laboratory, morphology, performance, prokaryotes
The acidification of the ocean caused by the diffusion of anthropogenic carbon dioxide (CO2) into seawater has been believed to threaten the stability of the marine ecosystem. As one of the major contributors to the primary production in oligotrophic oceans, the response of Trichodesmium to the acidification of the ocean has attracted a lot of attention. Therefore, in this study, we applied physiological and biochemical methods to identify the influences of high pCO2 and low pH conditions on the growth of T. erythraeum. Our results showed that the low pH during the acidification of the ocean was the main factor inhibiting the growth of T. erythraeum. In addition, low pH caused oxidative stress to T. erythraeum, as evidenced by the increase of the reactive oxygen species and antioxidant enzyme’s activities. The activity of carbonic anhydrase (CA) enzyme is dually regulated by pCO2 and pH, and T. erythraeum can adapt to different levels of pCO2 and pH in seawater by flexibly adjusting CA enzyme activity. We also discovered that the stimulatory effect of high pCO2 on the exopolysaccharide (EPS) content of T. erythraeum outweighed the inhibitory effect of low pH during the process of ocean acidification. In conclusion, this study systematically revealed the effects of high pCO2 and low pH caused by the acidification of the ocean on the growth and EPS of T. erythraeum. These results provide new insights into the response mechanisms of T. erythraeum in the acidified ocean under future climate conditions.
Continue reading ‘Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum’Brood-grooming behavior of American lobsters Homarus americanus in conditions of ocean warming and acidification
Published 9 September 2024 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, North Atlantic, performance, reproduction, temperature
The relationship between adverse environmental conditions and grooming behavior is an unresolved mechanism whereby a changing climate may impact reproductive success in animals that brood their eggs. Although important to embryo survival and development in decapod crustaceans, brood grooming by ovigerous females may be impacted by energetically demanding conditions associated with climate change, which may contribute to lethal and sublethal outcomes for brood health and survival. Despite its potential importance to reproduction, brood-grooming behavior has not been empirically described in the American lobster Homarus americanus H. Milne Edwards, 1837, a commercially important marine decapod. The relationship between brood-grooming behavior, temperature, and pH was explored at different points in the embryogenesis of American lobsters. For a period of 5 mo, egg-bearing females were exposed to different combinations of ecologically relevant conditions of temperature and pH, including those reflecting ocean warming (+4°C), ocean acidification (-0.5 pH), and the combination of warming and acidification. Fecundity, embryo development, and female grooming behavior were assessed at multiple time points. The proportion of time that lobsters spent fanning, but not probing, their broods increased with advancing embryo development. Neither egg loss, nor any measured brood-grooming behaviors, varied significantly with temperature or pH in this experiment. American lobster reproduction appears well suited to tolerate future conditions of ocean acidification and warming based on the ability to maintain stable brood grooming and brood mortality levels under a range of conditions.
Continue reading ‘Brood-grooming behavior of American lobsters Homarus americanus in conditions of ocean warming and acidification’Interactive impact of residual pyrethroid compounds used in the Chilean salmon farming industry and coastal acidification conditions on the feeding performance of farmed mussels in northern Patagonia
Published 3 September 2024 Science ClosedTags: biological response, fisheries, laboratory, mollusks, multiple factors, performance, physiology, reproduction, socio-economy, temperature
Highlights
- We examine the interaction of natural environmental regimes of temperature and pH conditions, with pyrethroids concentration used by salmon farming industry in Chilean Patagonia, and its potential impact of mussel feeding (clearance and ingestion rate of newly-hatched larvae and juveniles).
- We combined approaches, including oceanographic monitoring in a salmon and mussel farming area in Chilean Patagonia, with experiments aiming estimate the effects of two pyrethroids (deltamethrin and cypermethrin) on the clearance and ingestion rate of mussel larvae.
- We also exposed to mussel spats to both pyrethroids, but at contrasting temperature and pH conditions mimicking winter and summer conditions.
Abstract
The use of pyrethroids in aquaculture has been an important component of achieving a thriving salmon farming industry in Chile. While the residual presence of such substances is known to depend on environmental conditions, most ecotoxicological studies to date have not considered environmental context. Here, we conducted oceanographic monitoring combined with experiments aiming to estimate the effects of two pyrethroids on the feeding rates of larvae of farmed mussels, Mytilus chilensis. In additional experiments, mussel spats were exposed to both pyrethroids, but under contrasting temperature/pH so as to mimic winter and summer conditions. Experiments mimicking spring conditions revealed that both pyrethroid substances affected the feeding of mussel larvae as a function of concentration. Conversely, significant impact of pyrethroids on adults were not observed with regard to temperature and pH, but a significant impact of low temperature/low pH condition on ingestion rates was confirmed. Given the current status of increasing ocean acidification, the results of this study are expected to provide useful information with regard to achieving sustainable mussel aquaculture, especially considering both activities occur in similar geographic areas, and the expansion of salmon farming areas is ongoing in Chile.
Continue reading ‘Interactive impact of residual pyrethroid compounds used in the Chilean salmon farming industry and coastal acidification conditions on the feeding performance of farmed mussels in northern Patagonia’Effects of pH/pCO2 fluctuation on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequence of coastal acidification
Published 30 August 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, North Pacific, performance, photosynthesis, physiology, phytoplankton
Coastal waters are impacted by a range of natural and anthropogenic factors, which superimpose on effects of increasing atmospheric CO2, resulting in dynamically changing seawater carbonate chemistry. Research on influences of dynamic pH/pCO2 on marine ecosystem is still in its infancy, although effects of ocean acidification have been extensively studied. In the present study, we manipulated the culturing pH/pCO2 to investigate physiological performance and fatty acid (FA) composition of two coastal diatoms Skeletonema costatum and Thalassiosira weissflogii in both steady and fluctuating pH/pCO2 regimes. Generally, seawater acidification and pH variability showed neutral or positive effects on specific growth rate, chlorophyll a, and biogenic silica contents of two species. Elevated pCO2 inhibited net photosynthetic rate by 27 % and enhanced mitochondrial respiration rate of S. costatum by 36 % in the steady pH regime, while these rates were unaltered by elevated pCO2 in the fluctuating regime. Elevated pCO2 leaded to 21 % lower saturated FA and twofold increase in polyunsaturated FA proportions of T. weissflogii. Our results indicate that costal acidification could affect primary production in a different way from ocean acidification. Together with the altered nutritional quality of prey for higher trophic levels, coastal acidification might have far-reaching consequence for marine ecosystem functioning.
Continue reading ‘Effects of pH/pCO2 fluctuation on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequence of coastal acidification’Integrated multi-biomarker responses of juvenile zebra seabream (Diplodus cervinus) to warming and acidification conditions
Published 29 August 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, mortality, multiple factors, North Atlantic, performance, physiology, reproduction, temperature
The impacts of climate change-related stressors are becoming more noticeable in the ocean, particularly in coastal marine ecosystems. Yet limited information still exists on the physiological state and ecological resilience of marine fish species, especially during their early life stages (i.e., larvae and juveniles). The present study investigated the effects of chronic exposure to seawater warming (OW; ΔT = +4 °C) and acidification (OA; ΔpH = −0.3 pH units, equivalent to pCO2~1000 µatm), acting alone or combined (OWA), on juvenile zebra seabream (Diplodus cervinus) physiological resilience, considering distinct levels of biological organization (i.e., biochemical, cell, organ and individual levels). After 60 days of exposure, both stressors, in isolation or combination, significantly decreased specific growth rate (−11% in OW, −42% in OA and −49% in OWA) and leukocyte counts (from −29% in OA and OWA up to −37% in OW) in relation to the control treatment. In addition, a decreased Fulton’s condition index (K) was observed under warming and acidification in combination (−35% in OWA). At the cell level, OW, OA and OWA triggered different biomarker responses in D. cervinus (i.e., up-regulation, down-regulation, or absence of significant effect). In general, the results are suggestive of an antagonistic effect when warming and acidification are combined. OWA yielded the highest integrated biomarker response (IBR) index value in the whole organism, muscle, brain and gills of D. cervinus juveniles, therefore suggesting that the effects of these stressors are more severe when they act together. The distinct patterns observed in each stress scenario highlight the importance of carrying out further studies adjusted to the specificities of different regions, i.e., accounting not only for the type and degree of severity of environmental stressors already felt and/or projected for that specific area, but also the physiological plasticity of species that inhabit a particular ecosystem. The gathered knowledge will allow one to determine the vulnerability of particular marine species and geographic areas and, most importantly, to draw up effective and tailor-made conservation strategies to overcome climate change impacts.
Continue reading ‘Integrated multi-biomarker responses of juvenile zebra seabream (Diplodus cervinus) to warming and acidification conditions’Can niche plasticity mediate species persistence under ocean acidification?
Published 27 August 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, field, fish, performance, vents
Global change stressors can modify ecological niches of species, thereby altering ecological interactions within communities and food webs. Yet, some species might take advantage of a fast-changing environment, allowing species with high niche plasticity to thrive under climate change.
We used natural CO2 vents to test the effects of ocean acidification on niche modifications of a temperate rocky reef fish assemblage. We quantified three ecological niche traits (overlap, shift and breadth) across three key niche dimensions (trophic, habitat and behavioural).
Only one species increased its niche width along multiple niche dimensions (trophic and behavioural), shifted its niche in the remaining (habitat) was the only species to experience a highly increased density (i.e. doubling) at vents. The other three species that showed slightly increased or declining densities at vents only displayed a niche width increase in one (habitat niche) out of seven niche metrics considered. This niche modification was likely in response to habitat simplification (transition to a system dominated by turf algae) under ocean acidification.
We further showed that, at the vents, the less abundant fishes had a negligible competitive impact on the most abundant and common species. This species appeared to expand its niche space, overlapping with other species, which likely led to lower abundances of the latter under elevated CO2.
We conclude that niche plasticity across multiple dimensions could be a potential adaptation in fishes to benefit from a changing environment in a high-CO2 world.
Continue reading ‘Can niche plasticity mediate species persistence under ocean acidification?’Impact of fluctuating temperature and elevated CO2 on the growth, survival, and oxygen consumption of juvenile pinto abalone Haliotis kamtschatkana kamtschatkana Jonas
Published 22 August 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, mollusks, mortality, North Pacific, performance, physiology, respiration
Pinto abalone populations in the Salish Sea, WA have declined precipitously in the last several decades and have not recovered despite fishery closure in 1994. The Puget Sound Restoration Fund, in collaboration with state and federal agencies, has been outplanting juvenile pinto abalone at sites in the San Juan Archipelago, and some sites are much more successful than others despite similar physical characteristics. The sites, however, likely differ in oceanic parameters, such as temperature, salinity, and pH, which are in turn changing as the climate of the Earth is changing. The purpose of this study was to investigate the effects of temperature fluctuation and pCO2 levels on the survival, growth, and oxygen consumption of juvenile pinto abalone. In a fully crossed experiment, juvenile pinto abalone were held at either currently ambient (400 ppm) or elevated (1,200 ppm) pCO2 and at constant (10°C) or fluctuating (10 → 14 → 10°C) temperature. Survival was monitored weekly and growth was measured after 4 wk. In a second experiment, abalone were held in the same crossed pCO2 and temperature treatments, and oxygen consumption was measured. High pCO2 and fluctuating temperature both significantly decreased abalone survival. Abalone growth was not affected by pCO2 level (temperature could not be analyzed due to very poor survival in the fluctuating temperature treatments). In addition, there was an interaction between fluctuating temperature and pCO2 level on abalone oxygen consumption. Abalone in the constant temperature treatment had higher oxygen consumption when exposed to elevated pCO2; however, this pattern was not observed in the fluctuating temperature treatment. The results of this experiment indicate that outplant sites with minimal temperature fluctuation and lower pCO2 levels could lead to improvements in outplanting success of juvenile pinto abalone.
Continue reading ‘Impact of fluctuating temperature and elevated CO2 on the growth, survival, and oxygen consumption of juvenile pinto abalone Haliotis kamtschatkana kamtschatkana Jonas’Morphological and physiological responses of the cosmopolitan marine diatom Thalassiosira rotula to acidification
Published 13 August 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, laboratory, morphology, North Atlantic, performance, physiology, phytoplankton
We investigated the effect of decreased pH on the morphology and nutrient physiology of the cosmopolitan marine diatom Thalassiosira rotula (CCMP3362) by acclimating unialgal cultures to two different CO2 gas concentrations under optimal light, temperature and nutrient conditions. At lower pH (higher CO2), T. rotula exhibited a reduction in cell diameter (7%), surface area (13%), and volume (20%), and an increase in surface area-to-volume ratio (7%). All measures of silicification in T. rotula, i.e., silica (SiO2) quota, rate of silicic acid (Si(OH)4) utilization, and elemental ratios of SiO2:C and SiO2:N, remained unchanged. Similarly, carbon (C) and nitrogen (N) quotas, ratios and utilization rates were mostly unaffected by pH. In contrast, the utilization rate of nitrate (ρNO3) was significantly lower at decreased pH when the rate was normalized by cell number instead of by cell volume. The changes in cell morphology found in this study under low pH were likely not large enough to significantly impact physiological processes and the role of this species in marine food webs and biogeochemical cycles. It is possible that the interactive effects of pH, temperature, light, and nutrient availability characteristic of different regions of the world ocean could result in stronger physiological and morphological responses in this widespread diatom. However, under constant optimal growth conditions, T. rotula was only mildly affected by changes in pH, and in particular the physiology and elemental stoichiometry of C, N and Si were not sensitive to acidification.
Continue reading ‘Morphological and physiological responses of the cosmopolitan marine diatom Thalassiosira rotula to acidification’The water content, apoptosis, and proliferation of the brain in marine medaka affected by seawater acidification
Published 8 August 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, North Pacific, performance, physiology
A possible explanation for ocean acidification-induced changes in fish behavior is a systemic effect on the nervous system. Three biological barriers at the blood–brain interface effectively separate the brain from the body fluids. It is not known whether fish brain regions in contact with these barriers are affected by acidification. Here, we studied structural changes in medaka (Oryzias melastigma) brain regions contacting cerebrospinal fluid (CSF) after short-term (7 days) CO2 exposure. The brain water content decreased significantly and the superficial structure of the pia mater was changed, but there was no obvious damage to the internal structures of the brain after seawater acidification. Seawater acidification also led to an increase in apoptosis and a decrease in the number of proliferative cells in brain areas contacting CSF. These results indicate that the structure of CSF-contacting brain regions in medaka was affected by seawater acidification, and the brain responded to seawater acidification stress by increasing apoptosis and reducing proliferation.
Continue reading ‘The water content, apoptosis, and proliferation of the brain in marine medaka affected by seawater acidification’Unveiling the secrets of diatom-mediated calcification: implications for the biological pump
Published 19 July 2024 Science ClosedTags: abundance, biological response, chemistry, laboratory, North Pacific, otherprocess, performance, photosynthesis, phytoplankton
Siliceous diatoms are one of the most prominent actors in the oceans, and they account for approximately 40% of the primary production and particulate organic carbon export flux. It is believed that changes in carbon flux caused by variations in diatom distribution can lead to significant climate shifts. Although the fundamental pathways of diatom-driven carbon sequestration have long been established, there are no reports of CaCO3 precipitation induced by marine diatom species. This manuscript introduces novel details regarding the enhancement of aragonite precipitation during photosynthesis in Skeletonema costatum in both artificial and natural seawater. Through direct measurements of cell surfaces via a pH microelectrode and zeta potential analyzer, it was determined that the diatom-mediated promotion of CaCO3 precipitation is achieved through the creation of specific microenvironments with concentrated [CO32−] and [Ca2+] and/or the dehydrating effect of adsorbed Ca2+. Based on this mechanism, it is highly plausible that diatom-mediated calcification could occur in the oceans, an assertion that was supported by the significant deviation of total alkalinity (TA) from the conservative TA-salinity mixing line during a Skeletonema costatum bloom in the East China Sea and other similar occurrences. The newly discovered calcification pathway establishes a link between particulate inorganic and organic carbon flux and thus helps in the reassessment of marine carbon export fluxes and CO2 sequestration efficiency. This discovery may have important ramifications for assessing marine carbon cycling and predicting the potential effects of future ocean acidification.
Continue reading ‘Unveiling the secrets of diatom-mediated calcification: implications for the biological pump’Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii
Published 17 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, mortality, North Pacific, performance, physiology, reproduction
Ocean acidification can affect the immune responses of fish, but effects on pathogen susceptibility remain uncertain. Pacific herring Clupea pallasii were reared from hatch under 3 CO2 partial pressure ( pCO2) treatments (ambient, ∼650 µatm; intermediate, ∼1500 µatm; high, ∼3000 µatm) through metamorphosis (98 d) to evaluate the effects of ocean acidification on bioenergetics and susceptibility to an endemic viral disease. Mortality from viral hemorrhagic septicemia (VHS) was comparable between herring reared under ambient and intermediate pCO2 (all vulnerability testing at ambient pCO2). By contrast, fish reared under high pCO2 experienced significantly higher rates of VHS mortality, and the condition factor of survivors was significantly lower than in the other pCO2 treatments. However, the prevalence of infection among survivors was not influenced by pCO2 treatment. Pre-flexion larval development was not affected by elevated pCO2, as growth rate, energy use, and feeding activity were comparable across treatments. Similarly, long-term growth (14 wk) was not affected by chronic exposure to elevated pCO2. Herring reared under both elevated pCO2 treatments showed an average reduction in swimming speed; however, wide intra-treatment variability rendered the effect nonsignificant. This study demonstrates that the VHS susceptibility and bioenergetics of larval and post-metamorphic Pacific herring are not affected by near-future ocean acidification predicted for coastal systems of the North Pacific. However, increased susceptibility to VHS in fish reared under 3000 µatm pCO2 indicates potential health and fitness consequences from extreme acidification.
Continue reading ‘Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii’CO2-induced seawater acidification impairs the stinging cells of a jellyfish
Published 12 July 2024 Science ClosedTags: biological response, chemistry, cnidaria, growth, laboratory, molecular biology, performance, physiology
CO2-induced seawater acidification has been shown to modify predator–prey interactions in many marine taxa. Scyphozoans play an important role in the trophic dynamics of marine ecosystems during their blooms in coastal waters; however, the impacts of seawater acidification on the predation behavior of these animals are poorly understood. Here, we aimed to examine the impact of a decrease in seawater pH on the feeding behavior and growth of ephyrae (juvenile medusae) of the scyphozoan Aurelia coerulea. Combining bulk and single-cell RNA sequencing approaches, we assessed transcriptomic changes of ephyrae under a laboratory-based pH 7.6 condition. We found that the feeding rates and growth of ephyrae were significantly inhibited by a decrease in seawater pH. Furthermore, transcriptome analysis showed that a decline in pH significantly reduced the expression of genes related to toxins and nematocyst structure in ephyrae. These findings were further confirmed by single-cell transcriptomic analyses and revealed that low pH impaired the toxin activity and energy metabolism of stinging cells. The pH recovery experiment indicated that moving ephyrae from seawater with pH 7.6 into seawater with pH 8.1 greatly restored their feeding, growth, and toxin-related and nematocyst structure–related gene expression. However, exposure to pH 7.6 for 23 d could not recover the decrease in the feeding and growth of ephyrae. Together, these findings indicate that CO2-induced acidification compromised the stinging cells of A. coerulea ephyrae, with concomitant negative consequences on predation and growth that are likely to alter predator–prey interactions, with consequent effects on community structure and ecosystem.
Continue reading ‘CO2-induced seawater acidification impairs the stinging cells of a jellyfish’Temperate coastal fish shows resilience to extreme low pH in early larval stages
Published 11 July 2024 Science ClosedTags: biological response, chemistry, fish, Indian, laboratory, performance, physiology, reproduction, respiration
Highlights
- Coastal species is tolerant short term, acute low pH conditions in dynamic coastal habitats.
- Tolerance exceeds projected ocean acidification for local coastal habitat.
- Physiological capacity sufficient to compensate for low pH conditions even in the early post-flexion stage of Diplodus capensis.
- Diplodus capensis shows potential for behavioural plasticity at low pH.
Abstract
Fishes have shown varying responses to the decline in seawater pH associated with ocean acidification. Coastal marine species inhabit characteristically dynamic environments which requires physiological adaptation to variability, including fluctuations in pH and associated carbonate chemistry parameters. Our study assessed the response of the early life stages (postflexion) of a common coastal fish species (Diplodus capensis) that is found in coastal nearshore and estuarine habitats along the South African coastline. We assessed their metabolic and behavioural response to a range of pH conditions which covered a high pH (8.02), the lowest pH that they are naturally exposed to (7.75) as well as extremely low pH levels (∼7.75–7.27) exceeding their current range of exposure, which may occur with future coastal acidification. Our findings suggest that this species is metabolically tolerant of acute low pH conditions (down to 7.27 pH) showing no changes in either routine or active metabolic rates. Although our study identified a slight increase in swimming activity in D. capensis larvae exposed to low pH, there was no change in feeding activity. These results suggest that this species may have the physiological capacity to withstand the present and future high pH variability associated with its environments, in the absence of other stressors and ecological interactions. However, the increased swimming activity at low pH may translate into downstream ecological impacts, for which the mechanisms need to be assessed with further research.
Continue reading ‘Temperate coastal fish shows resilience to extreme low pH in early larval stages’Out of shape: ocean acidification simplifies coral reef architecture and reshuffles fish assemblages
Published 3 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, corals, fish, otherprocess, performance, physiology, South Pacific
- Climate change stressors are progressively simplifying biogenic habitats in the terrestrial and marine realms, and consequently altering the structure of associated species communities.
- Here, we used a volcanic CO2 seep in Papua New Guinea to test in situ if altered reef architecture due to ocean acidification reshuffles associated fish assemblages.
- We observed replacement of branching corals by massive corals at the seep, with simplified coral architectural complexity driving abundance declines between 60% and 86% for an assemblage of damselfishes associated with branching corals. An experimental test of habitat preference for a focal species indicated that acidification does not directly affect habitat selection behaviour, with changes in habitat structural complexity consequently appearing to be the stronger driver of assemblage reshuffling. Habitat health affected anti-predator behaviour, with P. moluccensis becoming less bold on dead branching corals relative to live branching corals, irrespective of ocean acidification.
- We conclude that coral reef fish assemblages are likely to be more sensitive to changes in habitat structure induced by increasing pCO2 than any direct effects on behaviour, indicating that changes in coral architecture and live cover may act as important mediators of reef fish community structures in a future ocean.
Ocean warming and acidification adjust inter- and intra-specific variability in the functional trait expression of polar invertebrates
Published 3 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, echinoderms, mollusks, otherprocess, performance, sediment
Climate change is known to affect the distribution and composition of species, but concomitant alterations to functionally important aspects of behaviour and species-environment relations are poorly constrained. Here, we examine the ecosystem ramifications of changes in sediment-dwelling invertebrate bioturbation behaviour—a key process mediating nutrient cycling—associated with near-future environmental conditions (+ 1.5 °C, 550 ppm [pCO2]) for species from polar regions experiencing rapid rates of climate change. We find that responses to warming and acidification vary between species and lead to a reduction in intra-specific variability in behavioural trait expression that adjusts the magnitude and direction of nutrient concentrations. Our analyses also indicate that species behaviour is not predetermined, but can be dependent on local variations in environmental history that set population capacities for phenotypic plasticity. We provide evidence that certain, but subtle, aspects of inter- and intra-specific variation in behavioural trait expression, rather than the presence or proportional representation of species per se, is an important and under-appreciated determinant of benthic biogeochemical responses to climate change. Such changes in species behaviour may act as an early warning for impending ecological transitions associated with progressive climate forcing.
Continue reading ‘Ocean warming and acidification adjust inter- and intra-specific variability in the functional trait expression of polar invertebrates’Impact of ocean acidification on microzooplankton grazing dynamics
Published 28 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, laboratory, North Pacific, otherprocess, performance, phytoplankton, zooplankton
This study examines the potential impacts of projected atmospheric carbon dioxide (pCO2) levels reaching 800 ppm by the end of the century, focusing on ocean acidification effects on marine ecosystems in the coastal areas of Bohai. We investigated how acidification affects the grazing patterns of microzooplankton using dilution techniques and ecophysiological methods. Our findings indicate that acidic conditions shift the phytoplankton community structure, changing dominant species. Elevated CO2 concentrations reduced grazing pressure on phytoplankton, with less steep declines in growth rates at 800 ppm CO2 (spring: 2.43 d−1 vs. 2.16 d−1, summer: −0.46 d−1 vs. −0.73 d−1, autumn: −0.45 d−1 vs. −0.90 d−1) and significant decreases in grazing pressure percentages (%Pp from 0.84 to 0.58 and %Pi from 0.64 to 0.46). Short-term acid exposure significantly increased superoxide dismutase activity in both microplankton (from 0.03 to 0.08 U mg−1, p<0.01) and nanoplankton (from 0.05 to 0.09 U mg−1, p<0.001), indicating an adaptive response to oxidative stress. These results highlight that elevated CO2 levels primarily boost phytoplankton growth by reducing microzooplankton grazing pressure, resulting in higher growth rates and a shift towards smaller-sized phytoplankton, reflecting complex short-term ecological responses to acidification. Further research is needed to understand the long-term effects of ocean acidification on microzooplankton and their role in marine secondary productivity.
Continue reading ‘Impact of ocean acidification on microzooplankton grazing dynamics’Neuromolecular mechanisms related to reflex behaviour in Aplysia are affected by ocean acidification
Published 25 June 2024 Science ClosedTags: biological response, chemistry, echinoderms, laboratory, molecular biology, performance, physiology
While ocean acidification (OA) impacts the behaviour of marine organisms, the complexity of neurosystems makes linking behavioural impairments to environmental change difficult. Using a simple model, we exposed Aplysia to ambient or elevated CO2 conditions (approx. 1500 µatm) and tested how OA affected the neuromolecular response of the pleural–pedal ganglia and caused tail withdrawal reflex (TWR) impairment. Under OA, Aplysia relax their tails faster with increased sensorin-A expression, an inhibitor of mechanosensory neurons. We further investigate how OA affects habituation training output, which produced a ‘sensitization-like’ behaviour and affected vesicle transport and stress response gene expression, revealing an influence of OA on learning. Finally, gabazine did not restore normal behaviour and elicited little molecular response with OA, instead, vesicular transport and cellular signalling link other neurotransmitter processes with TWR impairment. Our study shows the effects of OA on neurological tissue parts that control for behaviour.
Continue reading ‘Neuromolecular mechanisms related to reflex behaviour in Aplysia are affected by ocean acidification’
