Ocean acidification (OA) presents a unique challenge to early life stages of marine species. Developing organisms must balance the need to grow rapidly with the energetic demands of maintaining homeostasis. The small sizes of early life stages can make them highly sensitive to changes in environmental CO2 levels, but studies have found wide variation in responses to OA. Thus far most OA studies have manipulated CO2 only, and modifying factors need to be considered in greater detail. We investigated the effects of high pCO2 and food ration on rates of growth and mortality of a coastal fish, the California Grunion (Leuresthes tenuis). We also examined how CO2 and food levels affected feeding success, metabolic rate, and swimming activity – processes reflective of energy acquisition and expenditure. In general, exposure to high CO2 decreased energy intake by reducing feeding success, and increased energy expenditure by increasing metabolic rate and routine swimming speed, though the magnitudes of these effects varied somewhat with age. Despite these changes in energetics, growth of biomass was not affected significantly by pCO2 level but was reduced by low ration level, and we did not detect an interactive effect of food ration and pCO2 on growth. However, under OA conditions, larvae were in poorer condition (as evaluated by the mass to length ratio) by the end of the experiment and our analysis of mortality revealed a significant interaction in which the effects of OA were more lethal when food energy was limited. These results are consistent with the idea that although energy can be reallocated to preserve biomass growth, increased energetic demand under ocean acidification may draw energy away from maintenance, including those processes that foster homeostasis during development. Overall, these results highlight both the need to consider the availability of food energy as a force governing species’ responses to ocean acidification and the need to explicitly consider the energy allocated to both growth and maintenance as climate changes.
Continue reading ‘Experimental ocean acidification and food limitation reveals altered energy budgets and synergistic effects on mortality of larvae of a coastal fish’Posts Tagged 'mortality'
Experimental ocean acidification and food limitation reveals altered energy budgets and synergistic effects on mortality of larvae of a coastal fish
Published 31 August 2023 Science ClosedTags: biological response, fish, laboratory, morphology, mortality, multiple factors, North Pacific, nutrients, performance, physiology
Effects of pH and salinity on survival, growth, and enzyme activities in juveniles of the sunray surf clam (Mactra chinensis Philippi)
Published 30 August 2023 Science ClosedTags: biological response, growth, laboratory, mollusks, mortality, multiple factors, North Pacific, physiology, salinity
Highlights
- Salinity and pH tolerance ranges were identified for Mactra chinensis Philippi juveniles in laboratory tests.
- Survival rates were significantly reduced at extreme pH and salinity.
- Low pH and salinity induced oxidative stress, decreasing antioxidant enzyme activities.
Abstract
The study investigated the impact of salinity and pH changes on the survival, growth, and antioxidant enzyme activity in Mactra chinensis Philippi (1.00 ± 0.10 cm shell length, 0.75±0.04 cm shell height), a marine clam species. Juveniles were exposed to various pH levels (5.4 – 9.6) and salinities (5 – 35 psu) for up to 20 days at 19 ± 0.5 ˚C. The individual effect of salinity and pH on juveniles were evaluated under pH 8.0 and salinity 30 psu, respectively. The results indicated that the highest survival rates were observed at pH 8.0 (85%, salinity = 30 psu) and salinity 30 psu (95%, pH = 8.0). The survival rates were significantly reduced at extreme pH (≤ 7.2; ≥ 8.4) and salinities (≤ 15; 35 psu). Additionally, oxidative stress was observed in clams exposed to low pH and salinity as indicated by the decreased activities of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Notably, no significant difference in relative growth rates was observed between salinity 25 and 30 psu, between pH 7.8/8.4 and pH 8.0. Our results provide information on potential impact of pH and salinity changes on economically important bivalve species and may be used to optimize pH and salinity in aquaculture.
Continue reading ‘Effects of pH and salinity on survival, growth, and enzyme activities in juveniles of the sunray surf clam (Mactra chinensis Philippi)’Impact of dissolved CO2 on calcification in two large, benthic foraminiferal species
Published 23 August 2023 Science ClosedTags: biological response, calcification, laboratory, mortality, North Atlantic, protists
Rising atmospheric CO2 shifts the marine inorganic carbonate system and decreases seawater pH, a process often abbreviated to ‘ocean acidification’. Since acidification decreases the saturation state for crystalline calcium carbonate (e.g., calcite and aragonite), rising dissolved CO2 levels will either increase the energy demand for calcification or reduce the total amount of CaCO3 precipitated. Here we report growth of two large benthic photosymbiont-bearing foraminifera, Heterostegina depressa and Amphistegina lessonii, cultured at four different ocean acidification scenarios (400, 700, 1000 and 2200 ppm atmospheric pCO2). Using the alkalinity anomaly technique, we calculated the amount of calcium carbonate precipitated during the incubation and found that both species produced the most carbonate at intermediate CO2 levels. The chamber addition rates for each of the conditions were also determined and matched the changes in alkalinity. These results were complemented by micro-CT scanning of selected specimens to visualize the effect of CO2 on growth. The increased chamber addition rates at elevated CO2 concentrations suggest that both foraminifera species can take advantage of the increased availability of the inorganic carbon, despite a lower saturation state. This adds to the growing number of reports showing the variable response of foraminifera to elevated CO2 concentrations, which is likely a consequence of differences in calcification mechanisms.
Continue reading ‘Impact of dissolved CO2 on calcification in two large, benthic foraminiferal species’Large-scale culturing of Neogloboquadrina pachyderma, its growth in, and tolerance of, variable environmental conditions
Published 18 August 2023 Science ClosedTags: Arctic, biological response, laboratory, morphology, mortality, performance, phytoplankton, protists
The planktic foraminifera Neogloboquadrina pachyderma is a calcifying marine protist and the dominant planktic foraminifera species in the polar oceans, making it a key species in marine polar ecosystems. The calcium carbonate shells of foraminifera are widely used in palaeoclimate studies because their chemical composition reflects the seawater conditions in which they grow. This species provides unique proxy data for past surface ocean hydrography, which can provide valuable insight to future climate scenarios. However, little is known about the response of N. pachyderma to variable and changing environmental conditions.Here, we present observations from large-scale culturing experiments where temperature, salinity and carbonate chemistry were altered independently. We observed overall low mortality, calcification of new chambers and addition of secondary calcite crust in all our treatments. In-culture asexual reproduction events also allowed us to monitor the variable growth of N. pachyderma’s offspring. Several specimens had extended periods of dormancy or inactivity after which they recovered. These observations suggest that N. pachyderma can tolerate, adapt to and calcify within a wide range of environmental conditions. This has implications for the species-level response to ocean warming and acidification, for future studies aiming to culture N. pachyderma and use in palaeoenvironmental reconstruction.
Continue reading ‘Large-scale culturing of Neogloboquadrina pachyderma, its growth in, and tolerance of, variable environmental conditions’Examining the reproductive success of bull kelp (Nereocystis luetkeana, Phaeophyceae, Laminariales) in climate change conditions
Published 10 August 2023 Science ClosedTags: biological response, growth, laboratory, mortality, multiple factors, North Pacific, phanerogams, reproduction, temperature
Climate change is affecting marine ecosystems in many ways, including raising temperatures and leading to ocean acidification. From 2014 to 2016, an extensive marine heat wave extended along the west coast of North America and had devastating effects on numerous species, including bull kelp (Nereocystis luetkeana). Bull kelp is an important foundation species in coastal ecosystems and can be affected by marine heat waves and ocean acidification; however, the impacts have not been investigated on sensitive early life stages. To determine the effects of changing temperatures and carbonate levels on Northern California’s bull kelp populations, we collected sporophylls from mature bull kelp individuals in Point Arena, CA. At the Bodega Marine Laboratory, we released spores from field-collected bull kelp, and cultured microscopic gametophytes in a common garden experiment with a fully factorial design crossing modern conditions (11.63 ± 0.54°C and pH 7.93 ± 0.26) with observed extreme climate conditions (15.56 ± 0.83°C and 7.64 ± 0.32 pH). Our results indicated that both increased temperature and decreased pH influenced growth and egg production of bull kelp microscopic stages. Increased temperature resulted in decreased gametophyte survival and offspring production. In contrast, decreased pH had less of an effect but resulted in increased gametophyte survival and offspring production. Additionally, increased temperature significantly impacted reproductive timing by causing female gametophytes to produce offspring earlier than under ambient temperature conditions. Our findings can inform better predictions of the impacts of climate change on coastal ecosystems and provide key insights into environmental dynamics regulating the bull kelp lifecycle.
Continue reading ‘Examining the reproductive success of bull kelp (Nereocystis luetkeana, Phaeophyceae, Laminariales) in climate change conditions’Short-term exposure to combined condition of low salinity and pH affects ROS-mediated stress in disk abalone (Haliotis discus hannai)
Published 3 August 2023 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, physiology, salinity
Climate change due to global warming can alter the salinity and pH in aquatic ecosystems. Low salinity (LS) and ocean acidification (OA) are stressors involved in osmotic regulation and can alter the antioxidant capacity of the body. In this study, we observed Na+/K+-ATPase (NKA) expression and activity in disk abalone gill tissue and changes in hemolymph osmolarity in relation to osmotic regulation over a short period (5 days). To confirm the degree of oxidative stress caused by changes in salinity and pH, changes in H2O2 levels, reactive oxygen species (ROS) levels, antioxidant enzyme (superoxide dismutase [SOD] and catalase [CAT]) expression, and caspase-7 expression were investigated at the molecular level. The degree of DNA damage was evaluated using the comet assay. mRNA expression, activity of gill NKA, and osmolarity of the hemolymph were significantly decreased in the LS group. Nonetheless, no noteworthy distinction was observed in mRNA expression or NKA activity between the control group and OA group. Hemolymph H2O2 levels and mRNA expression of SOD, CAT, and caspase-7 were significantly higher under the LS + OA condition than under single conditions of LS and OA. Further, caspase-7 mRNA expression and DNA damage increased with increasing exposure time. The group exposed to LS + OA showed the highest levels of caspase-7 expression and DNA damage. These results indicate that a combination of low salinity and pH induces more stress than a single condition does. Unmanageable ROS-mediated stress caused by environmental changes can lead to cell death and DNA damage.
Continue reading ‘Short-term exposure to combined condition of low salinity and pH affects ROS-mediated stress in disk abalone (Haliotis discus hannai)’Northern shrimp from multiple origins show similar sensitivity to global change drivers, but different cellular energetic capacity
Published 3 August 2023 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, North Pacific, physiology, respiration, temperature
Species with a wide distribution can experience regionally a wide range of environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the physiological responses of the northern shrimp Pandalus borealis, at different levels of biological organization and from four different geographic origins, exposed to elevated temperature and low pH to define its sensitivity to future ocean warming (OW) and acidification (OA). Shrimp sampled within the northwest Atlantic, were exposed for 30 days to combinations of three temperature (2, 6 or 10 °C) and two pH levels (7.75 or 7.40). Survival, metabolic rates, whole-organism aerobic performance and cellular energetic capacity were assessed at the end of the exposure. Our results show that shrimp survival was negatively affected by temperature above 6 °C and low pH, regardless of their origin. Additionally, shrimp from different origins show overall similar whole-organism performances: aerobic scope increasing with increasing temperature and decreasing with decreasing pH. Finally, the stability of aerobic metabolism appears to be related to cellular adjustments specific to shrimp origin. Our results show that the level of intraspecific variation differs among levels of biological organization: different cellular capacities lead to similar individual performances. Thus, the northern shrimp sensitivity to OW and OA is overall comparable among origins. Nonetheless, shrimp vulnerability to predicted global change scenarios for 2100 could differ among origins due to different regional environmental conditions.
Continue reading ‘Northern shrimp from multiple origins show similar sensitivity to global change drivers, but different cellular energetic capacity’Water quality and the CO2-carbonate system during the preconditioning of Pacific oyster (Crassostrea gigas) in a recirculating aquaculture system
Published 2 August 2023 Science ClosedTags: biological response, fisheries, laboratory, mollusks, morphology, mortality, North Pacific, reproduction
The continued increase of the demand for seed of the Pacific oyster (Crassostrea gigas) has driven the aquaculture industry to produce land-based hatcheries using broodstock conditioning. This has led to the need to create closed systems to control the main factors involved in reproduction (temperature and food). Additionally, reproductive synchronization of broodstocks may be considered to ensure homogeneous maturation and spawning among the organisms. In this work, we synchronized the broodstock reproductive stage of Pacific oysters in a recirculating aquaculture system (RAS) using a “preconditioning” process and evaluated the effect of the water quality and the CO2-carbonate system on preconditioned broodstock. The oysters were kept at 12 °C for 45 days in a RAS containing a calcium reactor (C2) or without a calcium reactor (C1, control). Water quality parameters were measured daily, and the oyster’s condition and reproductive development were monitored using condition index, biometrics, and histology, on Days 0, 20, and 45. C1 and C2 systems kept the water quality within the ranges reported as favorable for bivalves. The calcium reactor kept the pH (8.03–8.10), alkalinity (200 mg/L as CaCO3), CO32− (≤ 80 µmol/kg), and Ω aragonite (≤ 1) closer to the ranges reported as optimal for bivalves. However, no significant differences were detected in the total weight and the condition index in C1 and C2. The preconditioning allowed to maintain the organisms in early reproductive development, allowing gametogenesis synchronization to start maturation.
Continue reading ‘Water quality and the CO2-carbonate system during the preconditioning of Pacific oyster (Crassostrea gigas) in a recirculating aquaculture system’Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability
Published 1 August 2023 Science ClosedTags: biological response, calcification, corals, laboratory, morphology, mortality, multiple factors, nutrients, performance, respiration, South Pacific, temperature
Highlights
- Response to multiple stressors differs between cold-water coral life stages.
- Elevated temperature and reduced feeding have the strongest effect.
- Highest mortality occurs in adult corals.
- Calcification rates decrease the most in juvenile corals.
- Three-month delay in response to changing environmental conditions.
Abstract
Cold-water corals (CWCs) are considered vulnerable to environmental changes. However, previous studies have focused on adult CWCs and mainly investigated the short-term effects of single stressors. So far, the effects of environmental changes on different CWC life stages are unknown, both for single and multiple stressors and over long time periods. Therefore, we conducted a six-month aquarium experiment with three life stages of Caryophyllia huinayensis to study their physiological response (survival, somatic growth, calcification and respiration) to the interactive effects of aragonite saturation (0.8 and 2.5), temperature (11 and 15 °C) and food availability (8 and 87 μg C L−1). The response clearly differed between life stages and measured traits. Elevated temperature and reduced feeding had the greatest effects, pushing the corals to their physiological limits. Highest mortality was observed in adult corals, while calcification rates decreased the most in juveniles. We observed a three-month delay in response, presumably because energy reserves declined, suggesting that short-term experiments overestimate coral resilience. Elevated summer temperatures and reduced food supply are likely to have the greatest impact on live CWCs in the future, leading to reduced coral growth and population shifts due to delayed juvenile maturation and high adult mortality.
Continue reading ‘Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability’The effects of ocean change drivers on the ecophysiology of the mottled brittle star Ophionereis fasciata
Published 18 July 2023 Science ClosedTags: biological response, calcification, dissolution, echinoderms, growth, laboratory, mesocosms, mortality, multiple factors, performance, physiology, South Pacific, temperature
Global ocean environments are rapidly changing, posing a substantial threat to the viability of marine populations due to the co-occurrence of different changing ocean (CO) drivers, such as ocean warming (OW) and ocean acidification (OA). In order to persist, marine species undergo some combination of acclimation and adaptation in response to these changes. Understanding such responses is essential to measure and predict the magnitude and direction of environmental changes, leading to the development of different approaches to understanding the links and interactions between biological processes and abiotic environmental conditions. A series of long-term mesocosm experiments have been conducted using adult Ophionereis fasciata as a model to investigate the physiological response and trade-offs of marine organisms to ocean acidification, ocean warming and the combined effect of both drivers. A scenario-based approach was adopted to elucidate the primary physiological responses to conditions currently experienced by this species in its tidally influenced habitat (21-24°C and pH 7.75-7.4) as well as changes expected to occur in the near future due to CO (+2.5 ℃ and -0.36 pH by 2100). Long-term exposure to OW and OA conditions affected survival, metabolic rate, regeneration and growth rates, calcification/dissolution and the righting response of O. fasciata. Temperature changes clearly impacted these aspects of the mottled brittle star, while changes in pH had more subtle or no effect. Our results indicate that for most of the assessed ecophysiological traits, there are no significant interactive effects of OA and OW. Moreover, temperature was the dominant driver, with a greater impact regarding the magnitude and quantity of the affected processes. However, the exposure to a combination of high temperature and low pH produced complex responses in terms of survival and calcification/dissolution. Finally, we documented the first report of symbionts associated with O. fasciata: an obligate amphipod parasite and a facultative commensal polychaete. Our findings indicate that the mottled brittle star will need to cope with CO conditions in context with the predictions made for New Zealand waters, with a potential impact on its performance and survival, as well as its distribution and ecological interactions.
Continue reading ‘The effects of ocean change drivers on the ecophysiology of the mottled brittle star Ophionereis fasciata’Integrated assessment of CO2-induced acidification lethal and sub-lethal effects on tropical mussels Perna perna
Published 17 July 2023 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, mortality, physiology, South Pacific
Leakages of CO2 capture and storage systems from the seabed are able to cause significant adverse biological effects in marine species. Adult mussels were exposed to different CO2 enrichment scenarios (pH from 8.3 to 6.0) for 96 h, and endpoints (lysosomal membrane deterioration, lipid peroxidation and primary damages in DNA) were assessed. Mortality and reduced health status can occur after short exposure of the tropical mussel Perna perna to pH levels lower than 7.5. Results pointed out cytogenotoxic effects in the hemolymph and gills after 48 and 96 h of exposure, respectively. These findings should be considered when environmental monitoring approaches are performed in tropical marine areas employing CCS strategies.
Continue reading ‘Integrated assessment of CO2-induced acidification lethal and sub-lethal effects on tropical mussels Perna perna’The impact of ocean acidification on the physiology of the blue mussel Mytilus edulis
Published 10 July 2023 Science ClosedTags: biological response, growth, laboratory, mollusks, morphology, mortality, North Atlantic
Bivalve aquaculture garners global ecological and economic benefits, which makes the continued health of bivalve populations paramount. Ocean acidification presents a novel pressure on bivalves. Decreased pH due to acidification limits the carbonate available for bivalves to takeup, thus inhibiting the formation and growth of their calcium carbonate-based shells. The aragonite saturation (Ω) of seawater serves a useful biologic contextualization for pH in studies of acidification and bivalves, as an Ω of 1 indicates that calcium and carbonate ions can bond to form calcium carbonate. Shell health is a central aspect of bivalve fitness as it is the main defense of these organisms against predation and exposure to disease or other unfavorable environmental conditions. Resistance of the shell against crushing force is highly relevant as aquaculture bivalves are reportedly becoming increasingly predated upon by crustaceans in the Gulf of Maine as more invasive crab species become established in the region. Juvenile bivalves seem exceptionally susceptible based on reports from the Gulf of Maine shellfish industry that has recently been losing large portions of their juvenile stock to crab predation.
The blue mussel Mytilus edulis was selected for this study as it is a model species in bivalve research and has commercial relevance in the Gulf of Maine. Three cohorts of M. edulis were housed for this study. One cohort was housed in aquaria to simulate ambient pH Gulf of Maine seawater, whereas two were exposed to moderately and highly acidified conditions (0.25 pH and 0.5 pH below ambient) in aquaria. Exposure was conducted for three months and enabled examination of the significance of pH, Ω, and the length of exposure time to the physical conditions of resistance to crushing force, lengthwise growth, and mortality.
Mussels with greater shell length had more resistance to crushing force than smaller mussels, and the force required to crush mussels of all length classes increased at a consistent rate of 1.25 lbf per millimeter of shell length within each length class. The average force required to crush mussels between 40 and 45 mm long was significantly greater than for mussels between 35 and 39.99 mm long. The average force required to crush mussels greater than 45 mm long was also significantly greater than for mussels between 40 and 45 mm long. Exposure time did not have a significant effect on the force required to crush the shells of M. edulis housed for the acidification treatment, but resistance to crushing force increased linearly with increased Ω. Crushing force resistance, standardized against length, was expected to increase by 0.609 lbf/mm per one unit increase of Ω.
Lengthwise growth rates were unaffected by the amount of time that mussels were exposed to treatment, but lower Ω decreased lengthwise growth rates. For every one unit increase of Ω, lengthwise growth was expected to increase by 176%. Mussels housed at ambient pH levels had the highest average lengthwise growth rate, whereas the average lengthwise growth was lowest in the -0.5 pH treatment. One additional mortality out of one-thousand mussels per day was estimated by the end of the study period, but Ω did not significantly affect mussel mortality. The number of mussel mortalities in the aquaria increased over the course of the study period, but percent mortality never exceeded 5% of the total cohort in any of the treatment aquaria, and biweekly percent mortality ranged between 0.18% to 4.92%. Acidification may lower blue mussel shell resistance to crushing force and may increase the timeframe when mussels are more actively susceptible to predation by crabs and other damage through the paired effects of acidification on force resistance and lengthwise growth.
Continue reading ‘The impact of ocean acidification on the physiology of the blue mussel Mytilus edulis’Growth performance, antioxidant indexes, and the expression of genes were considerably promoted by dietary supplementation of alanyl-glutamine and vitamin E in juvenile marine medaka in seawater acidification by carbon dioxide
Published 26 June 2023 Science ClosedTags: biological response, fish, growth, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, nutrients, physiology
The experiment was conducted to study the effect of different dietary supplementation of alanyl-glutamine dipeptide (AGD) and/or vitamin E (VE) on the growth performance, antioxidant indexes, and the expression of glutathione peroxidase (GPx) and peroxisome proliferator-activated receptor α (PPARⱭ) genes in juvenile marine medaka (Oryzias melastigma) in seawater acidification. Seven groups of juvenile marine medaka in triplicate were studied in an ecosystem. One of them was in normal seawater (pH 8.1, pH control), and the others were in seawater acidification (pH 7.7) regulated by carbon dioxide (CO2). The juveniles were separately fed for 10 weeks using one of six different diets. The six diets were one control diet (basic feed) without supplements and the other diets with different amounts of additional AGD and/or VE. The juveniles were sampled randomly for analysis of a whole fish in week 0 and week 10. The results showed that different dietary supplementation of AGD and/or VE could considerably promote the growth performance, antioxidant indexes, and the expression of GPx and PPARα genes of juvenile marine medaka in seawater acidification. The optimal diet was D4, with additional AGD 5 g and VE 50 IU per kg of dried feed.
Continue reading ‘Growth performance, antioxidant indexes, and the expression of genes were considerably promoted by dietary supplementation of alanyl-glutamine and vitamin E in juvenile marine medaka in seawater acidification by carbon dioxide’Impact of fluctuating temperature and elevated CO2 on the growth, survival, and metabolic rate of the endangered pinto abalone (Haliotis kamtschatkana) in the Salish Sea
Published 23 June 2023 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, physiology, temperature
Pinto abalone (Haliotis kamtschatkana) is the only abalone species found in the Salish Sea in the northeastern Pacific Ocean. They were recently declared as a State endangered species and human intervention is necessary to recover the species. Puget Sound Restoration Fund (PSRF) is one of the organizations trying to restore pinto abalone populations in the Salish Sea. Some of their outplant sites are less successful than others although they are physically similar. Currently, there is no research on how environmental variation affects juvenile pinto abalone survival, growth, and metabolic rate.
The goal of my thesis was to simulate summer sea water temperature fluctuations in the Salish Sea at different pCO2 levels. I investigated how these treatments affected juvenile pinto abalone growth, survival, and metabolic rate. I also included abalone size as a factor in my growth and survival experiment. I hypothesized that (1) fluctuating temperature and elevated pCO2 would negatively interact, resulting in less growth and survival, with larger abalone less affected. And (2) that fluctuating temperature and elevated pCO2 would synergistically interact, resulting in abalone with an increased metabolic rate. Fluctuating temperature significantly decreased abalone survival. Growth was not impacted by initial size nor pCO2 level. There was a significant interaction between temperature and pCO2 on abalone metabolic rate.
In addition to the physical parameters used to determine outplant sites, PSRF can use my findings to choose outplant sites better suited for juvenile pinto abalone to increase the probability of their populations recovering in the Salish Sea.
Continue reading ‘Impact of fluctuating temperature and elevated CO2 on the growth, survival, and metabolic rate of the endangered pinto abalone (Haliotis kamtschatkana) in the Salish Sea’Variable food alters responses of larval crown-of-thorns starfish to ocean warming but not acidification
Published 20 June 2023 Science ClosedTags: biological response, echinoderms, laboratory, morphology, mortality, multiple factors, nutrients, performance, South Pacific, temperature
Phytoplankton abundance is decreasing and becoming more variable as the ocean climate changes. We examine how low, high, and variable phytoplankton food supply affected the survival, development, and growth of larval crown-of-thorns starfish, Acanthaster sp. exposed to combined warming (26, 30 °C) and acidification (pH 8.0, 7.6). Larvae fed a low food ration are smaller, and develop slower and with more abnormalities than larvae fed a high ration. Larvae fed a variable food supply (low, followed by high ration) overcome the negative effects of low food on development rate and occurrence of abnormalities, but are 16–17% smaller than larvae fed the high ration continuously. Acidification (pH 7.6) slows growth and development and increases abnormalities regardless of the food regime. Warming slows growth and development, but these effects are mitigated by high food availability. As tropical oceans warm, the success of crown-of-thorns starfish larvae may depend on the abundance of their phytoplankton prey.
Continue reading ‘Variable food alters responses of larval crown-of-thorns starfish to ocean warming but not acidification’Effects of sediment and water column acidification on growth, survival, burrowing behaviour, and GABAA receptor function of benthic invertebrates
Published 16 June 2023 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, performance, physiology, sediment
In coastal regions, sediment-dwelling animals are exposed to a high degree of variability in seawater and sediment pH and pH is expected to decline due to anthropogenic effects. The impacts of 6-week exposure to reduced-pH seawater on length, weight, and survival of two species of molluscs that inhabit mudflats, juvenile soft-shell clams (Mya arenaria) and adult mud snails (Tritia obsoleta), were examined in two laboratory trials (2017 and 2018). The interactive effects of this prior exposure to water column acidification and subsequent sediment acidification on burrowing behaviour were then investigated for these mollusc species and adults of the amphipod Corophium volutator. In a separate experiment, the potential involvement of GABAA receptors in changes in burrowing behaviour in reduced-pH conditions was tested by exposing three species: C. volutator, T. obsoleta, and the Baltic clam Limecola balthica to sediment acidification and the neuroinhibitor gabazine. Reduced-pH water conditions only decreased the shell length of T. obsoleta in 2017 while all other morphometric metrics were not significantly impacted for this species in either year or for M. arenaria. The burrowing of T. obsoleta was reduced by 13% in acidified sediments in one of the two years but not by prior exposure to water column acidification. The burrowing of M. arenaria was not affected by either factor. The burrowing of C. volutator was impacted by the interaction of water column exposure and sediment acidification in 2017 with the acidified water, control sediment treatment having 14% higher burrowing then the remaining treatment combinations. In 2018, C. volutator burrowing was reduced in acidified sediment by 30%. The presence of gabazine only had an interactive effect on the burrowing of one species, C. volutator. The presence of gabazine increased the proportion of C. volutator individuals burrowed in the acidified water treatment by almost 30%, suggesting that GABAA neuroreceptors are involved in the mechanism for the impact of sediment acidification on burrowing in this species. The results of our experiments indicate that there is taxonomic variation in species’ responses of benthic invertebrates to ocean and sediment acidification with respect to growth, survival, and burrowing behaviour.
Continue reading ‘Effects of sediment and water column acidification on growth, survival, burrowing behaviour, and GABAA receptor function of benthic invertebrates’Costs and mechanisms associated with resilience to acidification in marine bivalves
Published 9 June 2023 Science ClosedTags: adaptation, biological response, dissolution, laboratory, molecular biology, mollusks, mortality, otherprocess, physiology
The unprecedented flux of CO2 into the ocean and the resulting chemical reactions has led to a reduction in pH, carbonate concentration, and saturation states of calcium carbonate, known as ocean acidification (OA). These conditions make it more difficult to precipitate biogenic calcium carbonate to mineralize shells because of the reduction in available carbonate ions. This represents a serious and growing threat to the future of commercially and ecologically important species, such as the northern quahog (Mercenaria mercenaria) and eastern oyster (Crassostrea virginica). But clams and oysters are found in heterogeneous coastal environments and are already exposed to reductions in pH surpassing predictions for the decrease in open ocean pH for the end of the century (with pH dropping below 7 under ambient conditions). These bivalves have shown high levels of resilience to fluctuations in pH and a capacity to respond to altered carbonate chemistry. However, the accelerated pace of these changes requires additional understanding of how or if species and populations will be able to acclimate or adapt to such swift environmental alterations. Future acidification might result in reduction in average pH, changes in the scale of variability, more occurrences of extreme acidification, and less periods of relief, exceeding thresholds of tolerance.
Thus far, the majority of studies have focused on the physiological effects of elevated pCO2 on bivalve larvae. While important, this leaves a substantial gap in knowledge of the molecular mechanisms of resilience to elevated pCO2 or the effect of acidification on different life history stages. To fill this gap in our understanding, this dissertation aims to uncover the mechanisms of resilience to elevated pCO2 in clams and oysters at different stages of their life.
This study combined physiological assays with ‘omic’ approaches (transcriptomics, genomics, proteomics) to assess the susceptibility of clams and oysters to acidification and the factors conferring resilience. Mechanisms enabling bivalves to respond to elevated pCO2 (from the organism level to individual genes) were investigated, taking into consideration the potential costs of resilience to elevated pCO2. Gene silencing experiments (RNAi) and chemical inhibition were used to confirm the protective role of candidate genes (perlucin and carbonic anhydrase, respectively) associated with resilience to elevated pCO2. While there were consequences for surviving under stressful acidification conditions, demonstrated by a marked reduction in immunity, depletion of energy resources, and inability to remineralize damaged shell, M. mercenaria and C. virginica, having already been exposed to natural fluctuations in pH and carbonate chemistry for generations, appear to be capable of implementing strategies to mitigate the negative impacts of elevated pCO2 (acclimation). While acclimation can be costly, the potential for adaptation was also investigated, and there was evidence to suggest genetic selection for OA-resilient genotypes enabling clams and oysters to persist under future climate regimes.
Continue reading ‘Costs and mechanisms associated with resilience to acidification in marine bivalves’Risk assessment of a coastal ecosystem from SW Spain exposed to CO2 enrichment conditions
Published 8 June 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, crustaceans, echinoderms, laboratory, mesocosms, mollusks, morphology, mortality, North Atlantic, otherprocess, physiology, sediment
The Weight-of-Evidence (WOE) approach uses multiple lines of evidence to analyze the adverse effects associated with CO2 enrichment in two stations from the Gulf of Cádiz (Spain) with different contamination degrees. Sediment contamination and metal (loid) mobility, toxicity, ecological integrity, and bioaccumulation from the samples exposed to different acidification scenarios (pH gradient from 8.0 to 6.0) were used in the WOE. The experiments were conducted under laboratory conditions using a CO2-bubbling system. Different integration approaches such as multivariate analyses were used to evaluate the results. The results indicated that the adverse biological effects under pH 6.5 were related to the mobility of dissolved elements (As, Fe, Cu, Ni, and Zn). Furthermore, the pH reduction was correlated to the increase of bioaccumulation of As, Cr, Cu, Fe, and Ni in the tissues of mussels at pH 7.0. The noncontaminated sediment showed environmental degradation related to the acidification at pH values of 7.0; whereas the sediment moderately contaminated showed both environmental risks, caused by acidification and the presence and the increase of the bioavailability of contaminants. The WOE approach supposes an effective tool to identify and distinguish the causes of adverse effects related to the enrichment of CO2 in marine environments.
Continue reading ‘Risk assessment of a coastal ecosystem from SW Spain exposed to CO2 enrichment conditions’Effects of anthropogenic stressorson Helgoland’s lobsters(Homarus gammarus)
Published 2 June 2023 Science ClosedTags: biological response, crustaceans, laboratory, morphology, mortality, multiple factors, North Atlantic, physiology, temperature
As meroplankton, lobsters make up a great portion of both benthic communities and planktonic fauna in the water column. Furthermore, they represent a mayor food source across the marine food web and a vital source of protein for humans. As an economically important species, lobsters are highly susceptible to anthropogenic stressors (e.g habitat destruction, over-fishing, noise pollution). Moreover, climate change may magnify the impact of human activities on lobsters’ fitness. The collapse of the population of European lobster (Homarus gammarus) around Helgoland constitutes a good example and prompted a largescale restocking program. Yet, the question arises if recruitment of remaining natural individuals and program released specimens could be stunted by ongoing climate change and human activities.
In my thesis I investigate the effect of several anthropogenic stressors that could potentially be affecting the route to recovery of Helgoland’s lobsters.
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Owing to the difficulties in catching lobster larvae in the field, I used larvae from lobster-rearing facilities to study the effects of anthropogenic stress on larval development and physiology. Studies on the effects of climate change on European lobster larvae have mostly focused on the isolated effect of ocean acidification or warming. Acidification treatments were based on two shared socio-economic pathways emitted by the Intergovernmental Panel on Climate Change (IPCC) regarding the amount of atmospheric CO2 for the end of the century. This study is the first to provide a more complete picture of the thermal limits at different levels of biological organization of lobster larvae under acidification by including a ten-level temperature gradient setup (13-24°C) The results show temperature was positively correlated with growth and energy metabolism; while, pCO2 had a negative impact on survival and morphology. Thus, climate change could potentially stunt the European lobster restocking efforts taking place on the island.
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Continue reading ‘Effects of anthropogenic stressorson Helgoland’s lobsters(Homarus gammarus)’Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata
Published 31 May 2023 Science ClosedTags: abundance, algae, biological response, calcification, corals, laboratory, mortality, multiple factors, North Pacific, otherprocess, photosynthesis, temperature
Ocean acidification (OA) and warming (OW) are major global threats to coral reef ecosystems; however, studies on their combined effects (OA + OW) are scarce. Therefore, we evaluated the effects of OA, OW, and OA + OW in the branching reef corals Acropora digitifera and Montipora digitata, which have been found to respond differently to environmental changes. Our results indicate that OW has a greater impact on A. digitifera and M. digitata than OA and that the former species is more vulnerable to OW than the latter. OW was the main stressor for increased mortality and decreased calcification in the OA + OW group, and the effect of OA + OW was additive in both species. Our findings suggest that the relative abundance and cover of M. digitata are expected to increase whereas those of A. digitifera may decrease in the near future in Okinawa.
Continue reading ‘Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata’
