Posts Tagged 'crustaceans'

Do pH-Variable habitats provide refuge for stone crabs from coastal acidification?

PURPOSE OF ACTIVITY

This guided, inquiry-based, hands-on lesson uses data from a local monitoring station in Tampa Bay, Florida, to guide students toward understanding how coastal acidification may impact the reproductive success of the Florida stone crab, an important regional fishery. The objectives of the lesson are for students to: (1) determine how pH varies between different habitats, (2) determine how pH can affect the reproductive success of an important commercial fishery, the Florida stone crab, and (3) evaluate whether exposure to variable seawater pH results in greater reproductive success in stone crabs relative to individuals that are not exposed to pH variability.

AUDIENCE

This lesson is designed for undergraduates in introductory-level biology, marine biology, environmental chemistry, and oceanography courses. The activities introduce students to ocean acidification relationships associated with diel fluctuations in pH in benthic habitats like seagrass and sand. The lesson also correlates reductions in seawater pH to the reproductive success of a commercially important species, the Florida stone crab.

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Transcriptome analysis of hepatopancreas in penaeus monodon under acute low pH stress

The decrease of seawater pH can affect the metabolism, acid-base balance, immune response and immunoprotease activity of aquatic animals, leading to aquatic animal stress, impairing the immune system of aquatic animals and weakening disease resistance, etc. In this study, we performed high-throughput sequencing analysis of the hepatopancreas transcriptome library of low pH stress penaeus monodon, and after sequencing quality control, a total of 43488612–56271828 Clean Reads were obtained, and GO annotation and KEGG pathway enrichment analysis were performed on the obtained Clean Reads, and a total of 395 DEGs were identified. we mined 10 differentially expressed and found that they were significantly enriched in the Metabolic pathways (ko01100), Biosynthesis of secondary metabolites (ko01110), Nitrogen metabolism (ko00910) pathways, such as PIGA, DGAT1, DGAT2, UBE2E on Metabolic pathways; UGT, GLT1, TIM genes on Biosynthesis of secondary metabolites; CA, CA2, CA4 genes on Nitrogen metabolism, are involved in lipid metabolism, induction of oxidative stress and inflammation in the muscular body of spot prawns. These genes play an important role in lipid metabolism, induction of oxidative stress and inflammatory response in the muscle of the shrimp. In summary, these genes provide valuable reference information for future breeding of low pH-tolerant shrimp.

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Effects of hypoxia and acidification on Calanus pacificus: behavioral changes in response to stressful environments

Copepods, which play major roles in marine food webs and biogeochemical cycling, frequently undergo diel vertical migration (DVM), swimming downwards during the day to avoid visual predation and upwards at night to feed. Natural water columns that are stratified with chemical stressors at depth, such as hypoxia and acidification, are increasing with climate change. Understanding behavioral responses of copepods to these stresses—in particular, whether copepods alter their natural migration—is important to anticipating impacts of climate change on marine ecosystems. We conducted laboratory experiments using stratified water columns to measure the effects of bottom water hypoxia and pH on mortality, distribution, and swimming behaviors of the calanoid copepod Calanus pacificus. When exposed to hypoxic (0.65 mg O2 l-1) bottom waters, the height of C. pacificus from the bottom increased 20% within hypoxic columns, and swimming speed decreased 46% at the bottom of hypoxic columns and increased 12% above hypoxic waters. When exposed to low pH (7.48) bottom waters, swimming speeds decreased by 8 and 9% at the base of the tanks and above acidic waters, respectively. Additionally, we found a 118% increase in ‘moribund’ (immobile on the bottom) copepods when exposed to hypoxic, but not acidic, bottom waters. Some swimming statistics differed between copepods collected from sites with versus without historical hypoxia and acidity. Observed responses suggest potential mechanisms underlying in situ changes in copepod population distributions when exposed to chemical stressors at depth.

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Do global environmental drivers’ ocean acidification and warming exacerbate the effects of oil pollution on the physiological energetics of Scylla serrata?

Global climate change–induced ocean warming and acidification have complex reverberations on the physiological functioning of marine ectotherms. The Sundarbans estuarine system has been under threat for the past few decades due to natural and anthropogenic disturbances. In recent years, petroleum products’ transportation and their usage have increased manifold, which causes accidental oil spills. The mud crab (Scylla serrata) is one of the most commercially exploited species in the Sundarbans. The key objective of this study was to delineate whether rearing under global environmental drivers (ocean acidification and warming) exacerbates the effect of a local driver (oil pollution) on the physiological energetics of mud crab (Scylla serrata) from the Sundarbans estuarine system. Animals were reared separately for 30 days under (a) the current climatic scenario (pH 8.1, 28°C) and (b) the predicted climate change scenario (pH 7.7, 34°C). After rearing for 30 days, 50% of the animals from each treatment were exposed to 5 mg L−1 of marine diesel oil for the next 24 h. Physiological energetics (ingestion rate, absorption rate, respiration rate, excretion rate, and scope for growth), thermal performance, thermal critical maxima (CTmax), acclimation response ratio (ARR), Arrhenius activation energy (AAE), temperature coefficient (Q10), warming tolerance (WT), and thermal safety margin (TSM) were evaluated. Ingestion and absorption rates were significantly reduced, whereas respiration and ammonia excretion rates significantly increased in stressful treatments, resulting in a significantly lower scope for growth. A profound impact on thermal performance was also noticed, leading to a downward shift in CTmax value for stress-acclimated treatment. The present results clearly highlighted the detrimental combined effect of global climatic stressors and pollution on the physiological energetics of crabs that might potentially reduce their population and affect coastal aquaculture in forthcoming years.

Continue reading ‘Do global environmental drivers’ ocean acidification and warming exacerbate the effects of oil pollution on the physiological energetics of Scylla serrata?’

Crustacean ecology in a changing climate

Whilst crustaceans occupy a diversity of ecological niches and have adapted to many environmental challenges, relatively little is known on how the predicted changes associated with climate change will impact individuals, communities, species and ecosystems globally. Direct oceanic change to seawater temperature, pH, alkalinity, oxygen level and salinity and indirect impacts on weather, seasonality, food availability and changes in ecological networks will put pressure upon crustaceans to acclimate. There is now emerging evidence that behaviour, physiology, fitness and ultimately reproduction and survival of coastal crustaceans is altered under experimental climate change conditions, with most studies showing negative impacts. Nevertheless measurable endpoints, multigenerational and ecosystem studies are to date extremely rare and the full impact of climate change stress upon crustaceans is nowhere near fully understood.

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Crustacean decapods are models to describe the general trends of biodiversity according to ocean acidification

A remarkable lack of punctual and comparable data on the availability of trophic resources characterizes most studies relating biodiversity and food webs, but decapod crustaceans will help, in this study, finding some peculiar common trends of ecosystems. Structural properties of networks, as statistically investigated, affect their stability and food webs are ultimately considered as complex networks of biotic interactions. Fixed mathematical limits constrain the number of species naturally assembled in a community, even if species composition was progressively modified by climate changes: the biodiversity has space constraints. Consequently, since there is less space at higher latitudes than at lower ones, less species may be predicted to globally co-exist, as the planet warms up and the oceans acidify. Here, according to some key mathematical relationships of networks, we forecast an inverse relationship between connectance (a specific feature of food webs) and species diversity. In this chapter, we will apply these relationships to test a general model of biodiversity trends based on the responses of crustacean decapods to the abundance of feeding sources, in a range of environments variably impacted by O.A. The conclusions reached within this chapter will demonstrate consistent properties characterizing the assemblages of aquatic creatures, and extensible to various structural levels, from single cells to the largest ecosystems.

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Ocean acidification does not overlook sex: review of understudied effects and implications of low pH on marine invertebrate sexual reproduction

Sexual reproduction is a fundamental process essential for species persistence, evolution, and diversity. However, unprecedented oceanographic shifts due to climate change can impact physiological processes, with important implications for sexual reproduction. Identifying bottlenecks and vulnerable stages in reproductive cycles will enable better prediction of the organism, population, community, and global-level consequences of ocean change. This article reviews how ocean acidification impacts sexual reproductive processes in marine invertebrates and highlights current research gaps. We focus on five economically and ecologically important taxonomic groups: cnidarians, crustaceans, echinoderms, molluscs and ascidians. We discuss the spatial and temporal variability of experimental designs, identify trends of performance in acidified conditions in the context of early reproductive traits (gametogenesis, fertilization, and reproductive resource allocation), and provide a quantitative meta-analysis of the published literature to assess the effects of low pH on fertilization rates across taxa. A total of 129 published studies investigated the effects of ocean acidification on 122 species in selected taxa. The impact of ocean acidification is dependent on taxa, the specific reproductive process examined, and study location. Our meta-analysis reveals that fertilization rate decreases as pH decreases, but effects are taxa-specific. Echinoderm fertilization appears more sensitive than molluscs to pH changes, and while data are limited, fertilization in cnidarians may be the most sensitive. Studies with echinoderms and bivalve molluscs are prevalent, while crustaceans and cephalopods are among the least studied species even though they constitute some of the largest fisheries worldwide. This lack of information has important implications for commercial aquaculture, wild fisheries, and conservation and restoration of wild populations. We recommend that studies expose organisms to different ocean acidification levels during the entire gametogenic cycle, and not only during the final stages before gametes or larvae are released. We argue for increased focus on fundamental reproductive processes and associated molecular mechanisms that may be vulnerable to shifts in ocean chemistry. Our recommendations for future research will allow for a better understanding of how reproduction in invertebrates will be affected in the context of a rapidly changing environment.

Continue reading ‘Ocean acidification does not overlook sex: review of understudied effects and implications of low pH on marine invertebrate sexual reproduction’

Marine heatwave impacts on newly-hatched planktonic larvae of an estuarine crab

Graphical abstract.

Highlights

  • Larvae survival was affected by temperature increase regardless of pH conditions.
  • Larvae heart beating and abdominal contractions were affected by temperature and pH.
  • Over the past 38 years Santos/São Vicente coast had a mean SST increase of 0.85 °C.
  • Higher intensity and duration of heatwaves are expected to reduce larval recruitment.

Abstract

Climate change is imposing constant and more severe environmental challenges to coastal and marine species. Regional climate and species acclimation capacity determine the communities’ ecological response to stressors. Marine heatwave events are of serious threat to species fitness and survivorship, even more to the sensitive early-history stages of ectotherms. By combining modeled regional historical data and climate change predictions with manipulative experiments, we evaluated the potential impact of marine heatwaves in a widespread and abundant planktonic larvae of the fiddler crab Leptuca thayeri. Larvae survival was affected by temperature increase with lowest survival probability under higher temperature treatments regardless of pH conditions. Larval physiology was affected by both temperature increase and pH conditions. With heatwaves becoming more frequent, hotter, and lasting longer in the region, we could expect potential reductions in the larval recruitment and stocks with cascade ecological negative effects on estuarine habitats.

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Interaction between reduced pH and multiple stressors affects the physiology of the fiddler crab Leptuca thayeri (Rathbun, 1900) (Decapoda: Brachyura: Ocypodidae)

Increasing ocean acidification combined with other impacts may cause changes in homeostatic mechanisms of intertidal invertebrates. Stressors do not act in isolation, and experimental work is needed to assess their synergistic potential. We evaluated the effect of exposure to multiple stressors on the survival, osmoregulation, metabolism, Q10, excretion, hepatosomatic index, and energy substrate oxidation on of the fiddler crab Leptuca thayeri (Rathbun, 1900). Crabs were exposed to two pH values (7.0, 6.3) combined with temperatures (20, 25, 30, 35, 40 °C) and these pH values combined with salinities (10, 20, 30, 40, and 50 psu) during acute exposure. All individuals died at 40 °C. Crabs osmoregulated, suggesting that the factors evaluated did not affect salt absorption or secretion. Individuals were weak hyperosmorregulators at lower salinities in the pH 7 control, but they became strong hyperosmoregulators at acidified pH 6.3. Alterations in oxygen consumption and hepatosomatic index were observed in individuals exposed to the acidified pH combined with temperatures or salinities, compared to those kept in the control pH. Q10 was elevated under an acidified pH, with crabs using proteins and lipids as energy substrates. The interaction between reduced pH and temperature or salinity thus affected physiological mechanisms related to the energetic metabolism, but elevated temperatures are more limiting because they affected survival. These physiological effects of acute exposure offer clues about extreme climatic events, which have a short duration but can affect the related energy demands.

Continue reading ‘Interaction between reduced pH and multiple stressors affects the physiology of the fiddler crab Leptuca thayeri (Rathbun, 1900) (Decapoda: Brachyura: Ocypodidae)’

Epigenetic plasticity enables copepods to cope with ocean acidification

Plasticity enhances species fitness and survival under climate change. Ocean acidification poses a potential threat to copepods, a major zooplankton group that serves as a key link between the lower and higher trophic levels in the marine environment, yet the mechanisms underlying different adaptive responses remain poorly understood. Here we show that although elevated CO2 can exert negative effects on reproduction of Paracyclopina nana, multigenerational plasticity can enable recovery after three generations. By integrating the methylome and transcriptome with the draft genome and undertaking DNA methylation treatments, we demonstrate the vital role of epigenetic modifications in ocean acidification responses and identify regions associated with reproductive resilience. Our results demonstrate that DNA methylation might play an important role in enhancing species fitness of copepods and that failing to consider phenotypic plasticity could lead to overestimation of species’ vulnerabilities.

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Immune defense in hypoxic waters: impacts of CO2 acidification

Periodic episodes of low oxygen (hypoxia) and elevated CO2 (hypercapnia) accompanied by low pH occur naturally in estuarine environments. Under the influence of climate change, the geographic range and intensity of hypoxia and hypercapnic hypoxia are predicted to increase, potentially jeopardizing the survival of economically and ecologically important organisms that use estuaries as habitat and nursery grounds. In this review we synthesize data from published studies that evaluate the impact of hypoxia and hypercapnic hypoxia on the ability of crustaceans and bivalve molluscs to defend themselves against potential microbial pathogens. Available data indicate that hypoxia generally has suppressive effects on host immunity against bacterial pathogens as measured by in vitro and in vivo assays. Few studies have documented the effects of hypercapnic hypoxia on crustaceans or bivalve immune defense, with a range of outcomes suggesting that added CO2 might have additive, negative, or no interactions with the effects of hypoxia alone. This synthesis points to the need for more partial pressure of O2 × low pH factorial design experiments and recommends the development of new host∶pathogen challenge models incorporating natural transmission of a wide range of viruses, bacteria, and parasites, along with novel in vivo tracking systems that better quantify how pathogens interact with their hosts in real time under laboratory and field conditions.

Continue reading ‘Immune defense in hypoxic waters: impacts of CO2 acidification’

How does CO2-induced acidification affect post-ecydsial exoskeletal mineralization in the blue crab, Callinectes sapidus?

Carbon dioxide (CO2) enrichment in seawater because of increased use of fossil fuels can possibly cause detrimental effects on the physiological processes of marine life, especially shell builders, due to CO2-induced ocean acidification. We investigated, for the first time, specifically the effect of CO2 enrichment on post-ecydsial shell mineralization in Crustacea using the blue crab, Callinectes sapidus, as the model crustacean. It was hypothesized that CO2 enrichment of seawater would adversely affect exoskeletal mineralization in the blue crab. This experiment used two groups of post-ecydsial crabs, with one group exposed to seawater at a pH of 8.20 and the other group treated with CO2-acidified seawater with a pH of 7.80 – 7.90. After a period of 7 days, samples of exoskeleton and hemolymph were collected from the survivors. CO2 enrichment was found to significantly increase exoskeletal magnesium content by 104% relative to control, while a statistically non-significant elevation of 31% in exoskeletal calcium was registered. Because CO2 treatment did not change the content of magnesium and calcium in the hemolymph, we postulate herein that increased exoskeletal mineralization in post-ecydsial blue crabs must stem from an increased influx of bicarbonate ions from the medium through the gill, to the hemolymph, and across the epidermis. Additionally, the observed significant increase in the mass of exoskeleton following CO2 treatment must be at least partly accounted for by enhanced postmolt carbonate salt deposition to the shell.

Continue reading ‘How does CO2-induced acidification affect post-ecydsial exoskeletal mineralization in the blue crab, Callinectes sapidus?’

Intergenerational effects of ocean acidification on reproductive traits of an estuarine copepod

Graphical abstract

Copepods are an important part of the marine food web because of their high biomass productivity and nutrient turnover rate compared to other zooplankton in the marine ecosystem. Despite their great ecological role in the ocean, there is only limited information available on the consequences of ocean acidification (OA) induced by the future increase in CO2 on the planet. More specifically, there is almost no information about the impact of OA on the European copepod Calanipeda aquaedulcis Kritschagin, 1873. Therefore, the present investigation hypothesized that OA would not produce negative multigenerational effects on the survival and reproductive performance of this copepod species. Here we assessed, the multigenerational (F1 and F2) effect of OA on eight important reproductive traits (maturity, prosome length, fertility, egg release, hatching success, survival rate, reproductive performance, and the total number of adults per generation). For this study, C. aquaedulcis were collected from the Guadalquivir River (southwest of Spain) and were exposed to four different pH gradients (pH 8.1 as control and pH 7.5, 7.0, 6.5 as acidified conditions) to mimic the future seawater acidification scenarios. The survival rate from nauplius to adult, C. aquaedulcis was significantly reduced by pHs and across generations. Besides, results also indicated that there were marked effects on fertility, reflected by a significantly lower number of eggs per female in each generation. Similarly, hatching success also showed a decreasing pattern towards low pH, and importantly, F1 females had lower hatching success than F0 females. While a beneficial parental effect was detected in the offspring in response to OA, it was insufficient to offset the negative effects caused by it. The findings presented here appear to have ecological significance, as decreasing the reproductive performance of copepods may have a negative impact on the marine food web, as ichthyofaunal feeding and growth are heavily reliant on this component of the food web.

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Effect of CO2 driven ocean acidification on the mud crab Scylla serrata instars

Graphical abstract

Highlights

  • Ocean acidification (OA) affected feed intake and growth of Scylla serrata.
  • OA reduced minerals content in S. serrata.
  • OA disturbs the chitin production and alkaline phosphatase activity in S.serrata.
  • OA increased the antioxidants and metabolic enzymes in S. serrata.

Abstract

The decreasing ocean pH seems to adversely affect marine organisms, including crustaceans, which leads to potential threats to seafood safety. The present investigation evaluated the effect of seawater acidification on the edible marine mud crab Scylla serrata instars. The experimental setup was designed using a multi-cell cage based system assembled with 20 pre holed PVC pipes containing 20 individual crabs to avoid cannibalism. The crab instars were exposed to CO2 driven acidified seawater at pH 7.8 (IPCC forecast pH at the end of the 21st century), 7.6, 7.4, 7.2, and 7.0 for 60 days. The crabs reared in seawater without acidification at pH 8.2 served as control. The present study revealed a notable decrease in survival, feed intake, growth, molting, tissue biochemical constituents, minerals, chitin, and alkaline phosphatase in S. serrata instar reared in acidified seawater, denotes the adverse effect of seawater acidification on crabs. The significant elevations in antioxidants, lipid peroxidation, and metabolic enzymes in all acidified seawater compared to ambient pH indicates the physiological stress of the crabs’ instars. The changes in the metabolic enzymes reveal the metabolism of protein and glucose for additional energy required by the crabs to tolerate the acidic stress. Hence, the present study provides insight into the seawater acidification can adversely affect the crab S. serrata.

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Differential effects of warming and acidification on chemosensory transmission and detection may strengthen non-consumptive effects of blue crab predators (Callinectes sapidus) on mud crab prey (Panopeus herbstii)

Predators control prey abundance and behavior, both of which strongly influence community dynamics. However, the relative importance of these predator effects may shift with climate change stressors, suggesting understanding the potential effects on these different processes is critical to predicting effects of climate change on community function. We investigated the effects of global warming and ocean acidification on the transmission and detection of chemical cues from blue crab predators (Callinectes sapidus) by mud crab prey (Panopeus herbstii). We measured mud crab feeding rates in the presence of blue crab predator cues, using either predator cues stressed in acidified conditions or mud crabs stressed in warmed and acidified conditions. Mud crabs consumed less food in the presence of predator cues, but acidifying the cues or subjecting mud crabs receiving the cues to acidified environment did not affect this antipredator response. Mud crabs in warmed conditions consumed significantly less food regardless of predator cue, but this effect was reversed in ambient conditions. Therefore, climate change may produce shifts in community regulation as warming potentially compromises consumptive effects of predators by reducing motor function, whereas non-consumptive effects mediated by sensory transmission and detection remain unaffected by acidification. Overall, warming may have stronger effects than acidification on community dynamics in oyster reefs as global temperatures continue to rise.

Continue reading ‘Differential effects of warming and acidification on chemosensory transmission and detection may strengthen non-consumptive effects of blue crab predators (Callinectes sapidus) on mud crab prey (Panopeus herbstii)’

Exoskeletal predator defenses of juvenile California spiny lobsters (Panulirus interruptus) are affected by fluctuating ocean acidification-like conditions

Spiny lobsters rely on multiple biomineralized exoskeletal predator defenses that may be sensitive to ocean acidification (OA). Compromised mechanical integrity of these defensive structures may tilt predator-prey outcomes, leading to increased mortality in the lobsters’ environment. Here, we tested the effects of OA-like conditions on the mechanical integrity of selected exoskeletal defenses of juvenile California spiny lobster, Panulirus interruptus. Young spiny lobsters reside in kelp forests with dynamic carbonate chemistry due to local metabolism and photosynthesis as well as seasonal upwelling, yielding daily and seasonal fluctuations in pH. Lobsters were exposed to a series of stable and diurnally fluctuating reduced pH conditions for three months (ambient pH/stable, 7.97; reduced pH/stable 7.67; reduced pH with low fluctuations, 7.67 ± 0.05; reduced pH with high fluctuations, 7.67 ± 0.10), after which we examined the intermolt composition (Ca and Mg content), ultrastructure (cuticle and layer thickness), and mechanical properties (hardness and stiffness) of selected exoskeletal predator defenses. Cuticle ultrastructure was consistently robust to pH conditions, while mineralization and mechanical properties were variable. Notably, the carapace was less mineralized under both reduced pH treatments with fluctuations, but with no effect on material properties, and the rostral horn had lower hardness in reduced/high fluctuating conditions without a corresponding difference in mineralization. Antennal flexural stiffness was lower in reduced, stable pH conditions compared to the reduced pH treatment with high fluctuations and not correlated with changes in cuticle structure or mineralization. These results demonstrate a complex relationship between mineralization and mechanical properties of the exoskeleton under changing ocean chemistry, and that fluctuating reduced pH conditions can induce responses not observed under the stable reduced pH conditions often used in OA research. Furthermore, this study shows that some juvenile California spiny lobster exoskeletal defenses are responsive to changes in ocean carbonate chemistry, even during the intermolt period, in ways that can potentially increase susceptibility to predation among this critical life stage.

Continue reading ‘Exoskeletal predator defenses of juvenile California spiny lobsters (Panulirus interruptus) are affected by fluctuating ocean acidification-like conditions’

Is ocean acidification really a threat to marine calcifiers? A systematic review and meta-analysis of 980+ studies spanning two decades

Ocean acidification is considered detrimental to marine calcifiers, but mounting contradictory evidence suggests a need to revisit this concept. This systematic review and meta-analysis aim to critically re-evaluate the prevailing paradigm of negative effects of ocean acidification on calcifiers. Based on 5153 observations from 985 studies, many calcifiers (e.g., echinoderms, crustaceans, and cephalopods) are found to be tolerant to near-future ocean acidification (pH ≈ 7.8 by the year 2100), but coccolithophores, calcifying algae, and corals appear to be sensitive. Calcifiers are generally more sensitive at the larval stage than adult stage. Over 70% of the observations in growth and calcification are non-negative, implying the acclimation capacity of many calcifiers to ocean acidification. This capacity can be mediated by phenotypic plasticity (e.g., physiological, mineralogical, structural, and molecular adjustments), transgenerational plasticity, increased food availability, or species interactions. The results suggest that the impacts of ocean acidification on calcifiers are less deleterious than initially thought as their adaptability has been underestimated. Therefore, in the forthcoming era of ocean acidification research, it is advocated that studying how marine organisms persist is as important as studying how they perish, and that future hypotheses and experimental designs are not constrained within the paradigm of negative effects.

Continue reading ‘Is ocean acidification really a threat to marine calcifiers? A systematic review and meta-analysis of 980+ studies spanning two decades’

Higher survival but smaller size of juvenile Dungeness crab (Metacarcinus magister) in high CO2

Highlights

  • Ocean acidification conditions do not affect Dungeness crab megalopae survival.
  • Dungeness crab juveniles reared in high CO2 have higher survival but are smaller.
  • Dungeness crab zoea more susceptible to ocean acidification than juveniles.

Abstract

Dungeness crab (Metacarcinus magister) are the most valuable fishery on the U.S. West Coast and both larval and adult Dungeness crabs are important components of regional food webs. Previous experiments have shown decreased survival and a slower development rate for Dungeness crab zoea reared in water with high CO2, indicating a susceptibility to ocean acidification. In this study we reared late-stage megalopae and juvenile Dungeness crabs in both ambient and high CO2 conditions for over 300 days. Counter to expectations, crabs reared in high CO2 had a higher survival rate than those reared in ambient conditions and crabs in high CO2 transitioned more quickly in one of the stages (J5 to J6). However, crabs reared in high CO2 were generally smaller and had a higher resting metabolic rate than crabs in ambient CO2. We hypothesized that two separate mechanisms were in effect, with one process driving survival and a second process driving size and respiration rate. We further hypothesized that increased mortality in ambient CO2 could be caused by a CO2-sensitive microbial pathogen, but that size and respiration differences were caused by the direct effects of CO2 on the crabs themselves. Overall, the zoea stages seem more sensitive to CO2 than the megalopae and juvenile stages.

Continue reading ‘Higher survival but smaller size of juvenile Dungeness crab (Metacarcinus magister) in high CO2’

Context-dependent effects of ocean acidification on the interaction between a crab predator and its oyster prey

Ocean acidification affects the fitness of species in coastal and estuarine systems, although interactions among species may alleviate or elevate the responses. Acidification effects on predator-prey interactions were evaluated between the blue crab Callinectes sapidus and eastern oyster Crassostrea virginica. Animals were exposed to 5 pH treatments: (1) control (pH ~8.00), constant pH at (2) 7.10 and (3) 6.75, and cycling pH from (4) 7.10 and (5) 6.75 to ~8.00, respectively. Crab foraging behavior, oyster size, and their defensive response against crabs (i.e. shell thickening) were compared among pH treatments. Results showed that predation rates of crabs tended to decrease with pH and from cycling to constant conditions, though statistical differences were only found at the lowest pH value and when consuming the larger oysters offered. Also, crab interest in oysters decreased with decreasing pH. In contrast, prey handling times and foraging motivation triggered by an odor stimulus were not affected by pH. In oysters, size metrics decreased with pH and also from cycling to constant conditions. Additionally, shells were thicker in the presence of predators, although the defensive strategy of oysters was weakened at the lowest pH level examined. Results indicate that although impaired foraging behavior of blue crabs may compensate for the negative effects on oysters under extreme acidification conditions, net effects are difficult to predict depending on the conditions to which animals are exposed and the size and behavioral variables considered.

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Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem

The California Current Marine Ecosystem is a highly productive system that exhibits strong natural variability and vulnerability to anthropogenic climate trends. Relating projections of ocean change to biological sensitivities requires detailed synthesis of experimental results. Here, we combine measured biological sensitivities with high-resolution climate projections of key variables (temperature, oxygen, and pCO2) to identify the direction, magnitude, and spatial distribution of organism-scale vulnerabilities to multiple axes of projected ocean change. Among 12 selected species of cultural and economic importance, we find that all are sensitive to projected changes in ocean conditions through responses that affect individual performance or population processes. Response indices were largest in the northern region and inner shelf. While performance traits generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss. For two species, combining sensitivities to temperature and oxygen changes through the Metabolic Index shows how aerobic habitat availability could be compressed under future conditions. Our results suggest substantial and specific ecological susceptibility in the next 80 years, including potential regional loss of canopy-forming kelp, changes in nearshore food webs caused by declining rates of survival among red urchins, Dungeness crab, and razor clams, and loss of aerobic habitat for anchovy and pink shrimp. We also highlight fillable gaps in knowledge, including specific physiological responses to stressors, variation in responses across life stages, and responses to multistressor combinations. These findings strengthen the case for filling information gaps with experiments focused on fitness-related responses and those that can be used to parameterize integrative physiological models, and suggest that the CCME is susceptible to substantial changes to ecosystem structure and function within this century.

Continue reading ‘Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem’

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