Crustose coralline algae (CCA) function as foundation species by creating marine carbonate hardground habitats. High‐latitude species may be vulnerable to regional warming and acidification. Here, we report the results of an experiment investigating the impacts of CO2‐induced acidification (pCO2 ∼350, 490, 890, 3200 µatm) and temperature (∼6.5, 8.5, 12.5°C) on the skeletal density of two species of high‐latitude CCA: Clathromorphum compactum (CC) and C. nereostratum (CN). Skeletal density of both species significantly declined with pCO2. In CN, the density of previously deposited skeleton declined in the highest pCO2 treatment. This species was also unable to precipitate new skeleton at 12.5°C, suggesting that CN will be particularly sensitive to future warming and acidification. The decline in skeletal density exhibited by both species under future pCO2 conditions could reduce their skeletal strength, potentially rendering them more vulnerable to disturbance, and impairing their production of critical habitat in high‐latitude systems.
Continue reading ‘Ocean acidification reduces skeletal density of hardground‐forming high‐latitude crustose coralline algae’Posts Tagged 'laboratory'
Ocean acidification reduces skeletal density of hardground‐forming high‐latitude crustose coralline algae
Published 15 February 2021 Science ClosedTags: algae, biological response, dissolution, laboratory, morphology, multiple factors, temperature
Adaptive responses of free‐living and symbiotic microalgae to simulated future ocean conditions
Published 12 February 2021 Science ClosedTags: adaptation, biological response, laboratory, multiple factors, phytoplankton, prokaryotes, review, temperature
Marine microalgae are a diverse group of microscopic eukaryotic and prokaryotic organisms capable of photosynthesis. They are important primary producers and carbon sinks but their physiology and persistence are severely affected by global climate change. Powerful experimental evolution technologies are being used to examine the potential of microalgae to respond adaptively to current and predicted future conditions, as well as to develop resources to facilitate species conservation and restoration of ecosystem functions. This review synthesizes findings and insights from experimental evolution studies of marine microalgae in response to elevated temperature and/or pCO2. Adaptation to these environmental conditions has been observed in many studies of marine dinoflagellates, diatoms and coccolithophores. An enhancement in traits such as growth and photo‐physiological performance and an increase in upper thermal limit have been shown to be possible, although the extent and rate of change differ between microalgal taxa. Studies employing multiple monoclonal replicates showed variation in responses among replicates and revealed the stochasticity of mutations. The work to date is already providing valuable information on species’ climate sensitivity or resilience to managers and policy‐makers but extrapolating these insights to ecosystem and community level impacts continues to be a challenge. We recommend future work should include in situ experiments, diurnal and seasonal fluctuations, multiple drivers and multiple starting genotypes. Fitness trade‐offs, stable versus plastic responses and the genetic bases of the changes also need investigating, and the incorporation of genome resequencing into experimental designs will be invaluable.
Continue reading ‘Adaptive responses of free‐living and symbiotic microalgae to simulated future ocean conditions’Welfare of scaleless fish, Sagor catfish (Hexanematichthyssagor) juveniles under different carbon dioxide concentrations
Published 12 February 2021 Science ClosedTags: biological response, fish, laboratory, morphology, physiology
Increased acidification has shown to bring negative impacts on marine fish. Currently, fish with scales have been extensively investigated, whereas a few systematic studies have been carried out for investigating impacts of acidified environment towards the growth of scaleless fish. Thus, this research aimed to evaluate carbon dioxide, CO2‐induced acidification impacts towards the welfare (growth with health) of the commercially aquaculture scaleless fish, Sagor catfish (Hexanematichthys sagor) for 20 weeks. Fish specimens were exposed to control pCO2 (400 µatm), mild pCO2 (550 µatm) and high pCO2 (900 µatm). Growth were measured by feed conversion ratio (FCR) plus specific growth rate (SGR). The outcomes indicated that the significantly lowest SGR was flaunted in high pCO2 group supported with the significantly highest FCR indicating poor growth. Health parameters significantly showed the highest value of red blood cell, haematocrit, haemoglobin, white blood cell, thrombocyte, mean corpuscular volume and haemoglobin in control group while urea, cholesterol, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, serum cortisol plus glucose were significantly the lowest in control pCO2 with regard to mild and high pCO2 group. These findings can serve as important baseline data in formulating managements regarding the specific effects of acidification on scaleless fish.
Continue reading ‘Welfare of scaleless fish, Sagor catfish (Hexanematichthyssagor) juveniles under different carbon dioxide concentrations’The dual benefit of ocean acidification for the laminarialean kelp, Saccharina latissima: enhanced growth and reduced herbivory
Published 11 February 2021 Science ClosedTags: algae, biological response, laboratory, mollusks, morphology, multiple factors, nutrients, performance
The laminarialean kelp, Saccharina latissima, is a common macroalgae along rocky shorelines that is also frequently used in aquaculture. This study examined how ocean acidification may alter the growth of S. latissima as well as grazing on S. latissima by the gastropod, Lacuna vincta. Under elevated nutrients, S. latissima experienced significantly enhanced growth at pCO2 levels >1,200 µatm compared to ambient pCO2 (~400 µatm). Elevated pCO2 (>830 µatm) also significantly reduced herbivory of L. vincta grazing on S. latissima relative to ambient pCO2. There was no difference in grazing of S. latissima previously grown under elevated or ambient pCO2, suggesting lowered herbivory was due to harm to the gastropods rather than alteration of the biochemical composition of the kelp. Decreased herbivory was specifically elicited when L. vincta were exposed to elevated pCO2 in the absence of food for >18 h prior to grazing, with reduced grazing persisting 72 h. Elevated growth of S. latissima and reduced grazing by L. vincta at 1,200 µatm pCO2 combined to increase net growth rates of S. latissima by more than four-fold relative to ambient pCO2. L. vincta consumed 70% of daily production by S. latissima under ambient pCO2 but only 38% and 9% at 800 µatm and 1,200 µatm, respectively. Collectively, decreased grazing by L. vincta coupled with enhanced growth of S. latissima under elevated pCO2 demonstrates that increased CO2 associated with climate change and/or coastal processes will dually benefit commercially and ecologically important kelps by both promoting growth and reducing grazing pressure.
Continue reading ‘The dual benefit of ocean acidification for the laminarialean kelp, Saccharina latissima: enhanced growth and reduced herbivory’Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules
Published 9 February 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, growth, laboratory, mortality, otherprocess, protists
Calcifying organisms such as benthic foraminifera are susceptible to changes in ocean pH and alkalinity. Responses to these changes include variations in mortality, calcification rates or assemblage composition, which have been observed in field and experimental studies. Here we applied a growth experiment with benthic foraminiferal propagules under different pH conditions to gather insights into the effect of pH on the composition of grown assemblages. A homogeneous propagule assemblage from a local mudflat in Corfu Island (Greece) was exposed to a range of pH conditions (6.5, 7.2, 7.8 and 8.5) for 5 weeks. In a second experiment, the assemblages were first exposed to low and subsequently to high conditions for a total of 8 weeks. After termination of the experiments, we recorded high survivability and growth throughout the treatments. Analysis of the assemblage composition of the first experiments revealed a shift from porcelaneous dominated taxa in the higher pH treatments to an assemblage with higher numbers of agglutinated taxa in the lower pH treatments. Soft-shelled monothalamous species were common throughout. The second experiment revealed assemblages that were significantly dominated by porcelaneous taxa with monothalamous taxa being almost absent. The results of this study are congruent with other observations on changing assemblage compositions with changing pH from both laboratory and field studies. The fast response of the assemblages through activation of potentially dormant propagules adds insights into the mechanisms behind seasonal composition changes in naturally variable environments such as river estuaries. They also shed new light on possible effects of continuous decreases in ocean pH on shallow-water foraminiferal assemblages in future.
Continue reading ‘Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules’Influence of ocean acidification and warming on DMSP & DMS in New Zealand coastal water
Published 8 February 2021 Science ClosedTags: chemistry, laboratory, mesocosms, multiple factors, temperature
The cycling of the trace gas dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) may be affected by future ocean acidification and warming. DMSP and DMS concentrations were monitored over 20-days in four mesocosm experiments in which the temperature and pH of coastal water were manipulated to projected values for the year 2100 and 2150. This had no effect on DMSP in the two-initial nutrient-depleted experiments; however, in the two nutrient-amended experiments, warmer temperature combined with lower pH had a more significant effect on DMSP & DMS concentrations than lower pH alone. Overall, this indicates that future warming may have greater influence on DMS production than ocean acidification. The observed reduction in DMSP at warmer temperatures was associated with changes in phytoplankton community and in particular with small flagellate biomass. A small decrease in DMS concentration was measured in the treatments relative to other studies, from −2% in the nutrient-amended low pH treatment to −16% in the year 2150 pH and temperature conditions. Temporal variation was also observed with DMS concentration increasing earlier in the higher temperature treatment. Nutrient availability and community composition should be considered in models of future DMS.
Continue reading ‘Influence of ocean acidification and warming on DMSP & DMS in New Zealand coastal water’Photosynthesis and calcification of the coccolithophore Emiliania huxleyi are more sensitive to changed levels of light and CO2 under nutrient limitation
Published 8 February 2021 Science ClosedTags: biological response, calcification, laboratory, light, multiple factors, nutrients, physiology, phytoplankton
Highlights
- Nutrient limitation reduced the light intensity for cells to achieve the highest rates of photosynthesis and calcification.
- Nitrate limitation enhanced calcification rate and phosphate limitation reduced photosynthetic rate.
- Electron transport rate linearly and positively correlated with rates of photosynthesis and calcification.
Abstract
Photophysiological responses of phytoplankton to changing multiple environmental drivers are essential in understanding and predicting ecological consequences of ocean climate changes. In this study, we investigated the combined effects of two CO2 levels (410 and 925 μatm) and five light intensities (80 to 480 μmol photons m−2 s−1) on cellular pigments contents, photosynthesis and calcification of the coccolithophore Emiliania huxleyi grown under nutrient replete and limited conditions, respectively. Our results showed that high light intensity, high CO2 level and nitrate limitation acted synergistically to reduce cellular chlorophyll a and carotenoid contents. Nitrate limitation predominantly enhanced calcification rate; phosphate limitation predominantly reduced photosynthetic carbon fixation rate, with larger extent of the reduction under higher levels of CO2 and light. Reduced availability of both nitrate and phosphate under the elevated CO2 concentration decreased saturating light levels for the cells to achieve the maximal relative electron transport rate (rETRmax). Light-saturating levels for rETRmax were lower than that for photosynthetic and calcification rates under the nutrient limitation. Regardless of the culture conditions, rETR under growth light levels correlated linearly and positively with measured photosynthetic and calcification rates. Our findings imply that E. huxleyi cells acclimated to macro-nutrient limitation and elevated CO2 concentration decreased their light requirement to achieve the maximal electron transport, photosynthetic and calcification rates, indicating a photophysiological strategy to cope with CO2 rise/pH drop in shoaled upper mixing layer above the thermocline where the microalgal cells are exposed to increased levels of light and decreased levels of nutrients.
Continue reading ‘Photosynthesis and calcification of the coccolithophore Emiliania huxleyi are more sensitive to changed levels of light and CO2 under nutrient limitation’Phosphorus enrichment masked the negative effects of ocean acidification on picophytoplankton and photosynthetic performance in the oligotrophic Indian Ocean
Published 8 February 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, laboratory, multiple factors, nutrients, otherprocess, photosynthesis, phytoplankton
Highlights
- High pCO2 and P interactively increased the abundances of Syn, Pro and PEuks.
- Rising pCO2 alone decreased the abundances of Syn, Pro and PEuks.
- Elevated pCO2 alone facilitated the NPQNSV process significantly.
- There was a strong coupling of picophytoplankton and the charge separation rates.
- P enrichment masked the negative effects of OA on picophytoplankton and photosynthesis.
Abstract
Dynamics of picophytoplankton and photosynthesis will be inevitably impacted by changing marine environment, such as ocean acidification and nutrient supply, but related studies are very scarce. Here we cultured the picophytoplankton-dominated surface water of the oligotrophic Eastern Indian Ocean (EIO; R/V Shiyan-3, 20 March to 18 May 2019) at two levels of pCO2 (400 and 1000 ppm) and phosphate (0.05 and 1.50 µM) to investigate the interactive effects of elevated pCO2 and phosphate (P) on the dynamics of picophytoplankton and photosynthetic properties. High pCO2 and P levels interactively increased the abundances of Synechococcus, Prochlorococcus and picoeukaryotes by 33%, 18%, and 21%, respectively, of which high P level had a major promoting effect. Conversely, rising pCO2 alone decreased their abundances by 9%, 32%, and 46%, respectively. For the photophysiological responses in relation to the combination of high pCO2 and P levels, there was an increase in the maximum (Fv/Fm) and effective (Fq‘/Fm‘) photochemical efficiency, the electron transfer rates (ETRRCII) and the charge separation rates (JVPSII, an indicator of primary production), but a decrease in the non-photochemical quenching (NPQNSV). Elevated pCO2 alone facilitated the NPQNSV process significantly, ultimately leading to reduced light use efficiency (e.g., Fv/Fm, Fq‘/Fm‘ and ETRRCII) and primary production (JVPSII). There was a strong coupling of picophytoplankton and JVPSII, suggesting the EIO primary productivity was potentially controlled by picophytoplankton. Overall, our results indicate that the negative effects caused by ocean acidification may be masked or outweighted by the role that P availability plays in regulating growth and metabolism in this oligotrophic ecosystem.
Continue reading ‘Phosphorus enrichment masked the negative effects of ocean acidification on picophytoplankton and photosynthetic performance in the oligotrophic Indian Ocean’The Mediterranean mussel Mytilus galloprovincialis: responses to climate change scenarios as a function of the original habitat
Published 5 February 2021 Science ClosedTags: adaptation, biological response, laboratory, mollusks, morphology, mortality, multiple factors, North Atlantic, performance, temperature
The impact of simulated seawater acidification and warming conditions on specimens of the mussel Mytilus galloprovincialis locally adapted to very distinct, widely separated sites in the Mediterranean Sea (Tunisia) and Atlantic Sea (Galicia, NW Spain) was evaluated in relation to key behavioral and eco-physiological parameters. Over the 2-month exposure to the experimental conditions, mussels were fed optimally to ensure that there are no synergistic interactions between climate change drivers and energetic status of the individuals. In general, regardless of origin (Atlantic or Mediterranean), the mussels were rather resilient to acidification for most of the parameters considered and they were able to grow in strongly acidified seawater through an increased feeding activity. However, shell strength decreased (40%) consistently in both mussel populations held in moderately and highly acidified seawater. The observed reduction in shell strength was not explained by slight alterations in organic matter, shell thickness or aragonite: calcite ratio. The combined effects of high acidification and warming on the key response of byssus strength caused a strong decline in mussel performance, although only in Galician mussels, in which the valve opening time decreased sharply as well as condition index (soft tissue state) and shell growth. By contrast, the observed negative effect of highly acidified scenario on the strength of Tunisian mussel shells was (partly but not totally) counterbalanced by the higher seawater temperature. Eco-physiological and behavioral interactions in mussels in relation to climate change are complex, and future scenarios for the ecology of the species and also the feasibility of cultivating them in Atlantic and Mediterranean zones are discussed.
Continue reading ‘The Mediterranean mussel Mytilus galloprovincialis: responses to climate change scenarios as a function of the original habitat’Coastal ocean acidification and nitrogen loading facilitate invasions of the non-indigenous red macroalga, Dasysiphonia japonica
Published 4 February 2021 Science ClosedTags: abundance, algae, biological response, communityMF, field, laboratory, morphology, multiple factors, nitrogen fixation, North Atlantic, nutrients
Coastal ecosystems are prone to multiple anthropogenic and natural stressors including eutrophication, acidification, and invasive species. While the growth of some macroalgae can be promoted by excessive nutrient loading and/or elevated pCO2, responses differ among species and ecosystems. Native to the western Pacific Ocean, the filamentous, turf-forming rhodophyte, Dasysiphonia japonica, appeared in estuaries of the northeastern Atlantic Ocean during the 1980s and the northwestern Atlantic Ocean during the late 2000s. Here, we report on the southernmost expansion of the D. japonica in North America and the effects of elevated nutrients and elevated pCO2 on the growth of D. japonica over an annual cycle in Long Island, New York, USA. Growth limitation of the macroalga varied seasonally. During winter and spring, when water temperatures were < 15 °C, growth was significantly enhanced by elevated pCO2 (p < 0.05). During summer and fall, when the water temperature was 15–24 °C, growth was significantly higher under elevated nutrient treatments (p < 0.05). When temperatures reached 28 °C, the macroalga grew poorly and was unaffected by nutrients or pCO2. The δ13C content of regional populations of D. japonica was −30‰, indicating the macroalga is an obligate CO2-user. This result, coupled with significantly increased growth under elevated pCO2 when temperatures were < 15 °C, indicates this macroalga is carbon-limited during colder months, when in situ pCO2 was significantly lower in Long Island estuaries compared to warmer months when estuaries are enriched in metabolically derived CO2. The δ15N content of this macroalga (9‰) indicated it utilized wastewater-derived N and its N limitation during warmer months coincided with lower concentrations of dissolved inorganic N in the water column. Given the stimulatory effect of nutrients on this macroalga and that eutrophication can promote seasonally elevated pCO2, this study suggests that eutrophic estuaries subject to peak annual temperatures < 28 °C may be particularly vulnerable to future invasions of D. japonica as ocean acidification intensifies. Conversely, nutrient reductions would serve as a management approach that would make coastal regions more resilient to invasions by this macroalga.
Continue reading ‘Coastal ocean acidification and nitrogen loading facilitate invasions of the non-indigenous red macroalga, Dasysiphonia japonica’Effect of environmental history on the habitat-forming kelp Macrocystis pyrifera responses to ocean acidification and warming: a physiological and molecular approach
Published 2 February 2021 Science ClosedTags: algae, biological response, laboratory, mesocosms, molecular biology, morphology, multiple factors, photosynthesis, physiology, South Pacific, temperature
The capacity of marine organisms to adapt and/or acclimate to climate change might differ among distinct populations, depending on their local environmental history and phenotypic plasticity. Kelp forests create some of the most productive habitats in the world, but globally, many populations have been negatively impacted by multiple anthropogenic stressors. Here, we compare the physiological and molecular responses to ocean acidification (OA) and warming (OW) of two populations of the giant kelp Macrocystis pyrifera from distinct upwelling conditions (weak vs strong). Using laboratory mesocosm experiments, we found that juvenile Macrocystis sporophyte responses to OW and OA did not differ among populations: elevated temperature reduced growth while OA had no effect on growth and photosynthesis. However, we observed higher growth rates and NO3− assimilation, and enhanced expression of metabolic-genes involved in the NO3− and CO2 assimilation in individuals from the strong upwelling site. Our results suggest that despite no inter-population differences in response to OA and OW, intrinsic differences among populations might be related to their natural variability in CO2, NO3− and seawater temperatures driven by coastal upwelling. Further work including additional populations and fluctuating climate change conditions rather than static values are needed to precisely determine how natural variability in environmental conditions might influence a species’ response to climate change.
Continue reading ‘Effect of environmental history on the habitat-forming kelp Macrocystis pyrifera responses to ocean acidification and warming: a physiological and molecular approach’Ocean acidification decreases grazing pressure but alters morphological structure in a dominant coastal seaweed
Published 1 February 2021 Science ClosedTags: algae, biological response, BRcommunity, laboratory, mollusks, morphology, nitrogen fixation, North Atlantic, performance, physiology
Ocean acidification driven by anthropogenic climate change is causing a global decrease in pH, which is projected to be 0.4 units lower in coastal shallow waters by the year 2100. Previous studies have shown that seaweeds grown under such conditions may alter their growth and photosynthetic capacity. It is not clear how such alterations might impact interactions between seaweed and herbivores, e.g. through changes in feeding rates, nutritional value, or defense levels. Changes in seaweeds are particularly important for coastal food webs, as they are key primary producers and often habitat-forming species. We cultured the habitat-forming brown seaweed Fucus vesiculosus for 30 days in projected future pCO2 (1100 μatm) with genetically identical controls in ambient pCO2 (400 μatm). Thereafter the macroalgae were exposed to grazing by Littorina littorea, acclimated to the relevant pCO2-treatment. We found increased growth (measured as surface area increase), decreased tissue strength in a tensile strength test, and decreased chemical defense (phlorotannins) levels in seaweeds exposed to high pCO2-levels. The herbivores exposed to elevated pCO2-levels showed improved condition index, decreased consumption, but no significant change in feeding preference. Fucoid seaweeds such as F. vesiculosus play important ecological roles in coastal habitats and are often foundation species, with a key role for ecosystem structure and function. The change in surface area and associated decrease in breaking force, as demonstrated by our results, indicate that F. vesiculosus grown under elevated levels of pCO2 may acquire an altered morphology and reduced tissue strength. This, together with increased wave energy in coastal ecosystems due to climate change, could have detrimental effects by reducing both habitat and food availability for herbivores.
Continue reading ‘Ocean acidification decreases grazing pressure but alters morphological structure in a dominant coastal seaweed’Adaptation of a marine diatom to ocean acidification and warming reveals constraints and trade-offs
Published 1 February 2021 Science ClosedTags: adaptation, biological response, laboratory, multiple factors, photosynthesis, physiology, phytoplankton, temperature
Highlights
- Ocean warming is the main driver for the adaptation of a marine diatom
- The adaptation resulting from warming can be constrained by ocean acidification
- The adaptations to ocean acidification and warming come with trade-offs
Abstract
Ocean acidification and warming are recognized as two major anthropogenic perturbations of the modern ocean. However, little is known about the adaptive response of phytoplankton to them. Here we examine the adaptation of a marine diatom Thalassiosira weissflogiito ocean acidification in combination with ocean warming. Our results show that ocean warming have a greater effect than acidification on the growth of T. weissflogiiover the long-term selection experiment (~380 generations), as well as many temperature response traits (e.g., optimum temperatures for photosynthesis, maximal net photosynthetic oxygen evolution rates, activation energy) in thermal reaction norm. These results suggest that ocean warming is the main driver for the evolution of the marine diatom T. weissflogii, rather than oceanacidification. However, the evolution resulting fromwarming can be constrained by ocean acidification, where ocean warming did not impose any effects at high CO2level. Furthermore, adaptationsto ocean warming alone or to the combination of ocean acidification and warming comewith trade-offs by inhibiting photochemical performances. The constrains and trade-offs associated with the adaptation to ocean acidification and warming demonstrated in this study, should be considered for parameterizing evolutionary responses in eco-evolutionary models of phytoplankton dynamics in a future ocean.
Continue reading ‘Adaptation of a marine diatom to ocean acidification and warming reveals constraints and trade-offs’American lobster postlarvae alter gene regulation in response to ocean warming and acidification
Published 29 January 2021 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, physiology, reproduction, temperature
Anthropogenic carbon emissions released into the atmosphere is driving rapid, concurrent increases in temperature and acidity across the world’s oceans. Disentangling the interactive effects of warming and acidification on vulnerable life stages is important to our understanding of responses of marine species to climate change. This study evaluates the interactive effects of these stressors on the acute response of gene expression of postlarval American lobster (Homarus americanus), a species whose geographic range is warming and acidifying faster than most of the world’s oceans. In the context of our experiment, we found two especially noteworthy results: First, although physiological end points have consistently been shown to be more responsive to warming in similar experimental designs, our study found gene regulation to be considerably more responsive to elevated pCO2. Furthermore, the combined effect of both stressors on gene regulation was significantly greater than either stressor alone. Using a full factorial experimental design, lobsters were raised in control and elevated pCO2 concentrations (400 ppm and 1,200 ppm) and temperatures (16°C and 19°C). A transcriptome was assembled from an identified 414,517 unique transcripts. Overall, 1,108 transcripts were differentially expressed across treatments, several of which were related to stress response and shell formation. When temperature alone was elevated (19°C), larvae downregulated genes related to cuticle development; when pCO2 alone was elevated (1,200 ppm), larvae upregulated chitinase as well as genes related to stress response and immune function. The joint effects of end‐century stressors (19°C, 1,200 ppm) resulted in the upregulation of those same genes, as well as cellulase, the downregulation of calcified cuticle proteins, and a greater upregulation of genes related to immune response and function. These results indicate that changes in gene expression in larval lobster provide a mechanism to respond to stressors resulting from a rapidly changing environment.
Continue reading ‘American lobster postlarvae alter gene regulation in response to ocean warming and acidification’Calcification does not necessarily protect articulated coralline algae from urchin grazing
Published 27 January 2021 Science ClosedTags: algae, biological response, BRcommunity, dissolution, echinoderms, laboratory, North Pacific, performance
Calcification is widely thought to be an adaptation that reduces the impact of herbivory. Recent work has shown that ocean acidification may negatively impact calcification of marine organisms, including coralline red algae, which could theoretically increase the susceptibility of corallines to benthic grazers. By manipulating calcium carbonate content of three articulated coralline algal species, we demonstrated that calcification has a variable and species-specific effect on urchin grazing. For two species, Corallina vancouveriensis and Corallina officinalis var. chilensis, reductions in calcium carbonate content did not cause a significant increase in urchin grazing, raising questions about the benefit of calcification in these species. For Calliarthron tuberculosum, reduced calcium carbonate content caused an increase in urchin grazing rates but only after calcium carbonate had been reduced by more than 15%, suggesting that only dramatic shifts in calcification would make C. tuberculosum more susceptible to urchin grazing. We hypothesize that the herbivory-reducing benefits of calcification likely depend upon coralline thallus morphology. Negative impacts of ocean acidification on calcification in coralline algae may not necessarily increase herbivory rates.
Continue reading ‘Calcification does not necessarily protect articulated coralline algae from urchin grazing’The effect of acidified seawater on shell characteristics of blood cockle, Tegillarca granosa
Published 27 January 2021 Science ClosedTags: biological response, laboratory, mollusks, morphology, South Pacific
Our ocean currently has been recorded to absorb about 25% of anthropogenic CO2 on an annual basis. This has estimated the global average sea surface pH to decrease from 8.2 to 8.1 units since the pre-industrial revolution and to further drop between 0.1 to 0.3 units by the end of the 21st century. This possesses a potential impact on wide range of marine organismschr(’39’) especially marine calcifiers where the CO32- is a fundamental mineral for shell and skeleton formation. In a 7-day experiment, this study investigated the effect of different pH treatments, which were pH 7.10, pH 7.50 and control pH (pH 7.81) on shell properties of the blood cockle, Tegillarca granosa. The shell weight and shell density of T. granosa was significantly reduced at pH 7.10. The smaller mean ratio for weight and density at pH 7.10 indicated there was a large difference between the initial and final value for weight and density. Furthermore, the scanning electron micrograph revealed the rough outer shell surface (periostracum) of T. granosa under decreased pH treatment (pH 7.10). However, the ocean acidification level of pH 7.50 which predicted to occur by the year 2300 showed no significant decrease in shell weight and shell density of T. granosa compared to the control pH treatment (pH 7.81).
Continue reading ‘The effect of acidified seawater on shell characteristics of blood cockle, Tegillarca granosa’Long-term thermal acclimation drives adaptive physiological adjustments of a marine gastropod to reduce sensitivity to climate change
Published 27 January 2021 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, physiology, respiration, South Pacific, temperature
Highlights
- The effects of thermal history on thermal threshold and physiology were assessed.
- Gastropods acclimated to warmer environments had higher thermal threshold (CTmax).
- Warm-acclimated gastropods were metabolically less active than cool-acclimated ones.
- Energy conservation appeared to be a strategy for thermal acclimation.
- Long-term thermal acclimation may allow marine organisms to adjust to climate change.
Abstract
Ocean warming is predicted to challenge the persistence of a variety of marine organisms, especially when combined with ocean acidification. Whilst temperature affects virtually all physiological processes, the extent to which thermal history mediates the adaptive capacity of marine organisms to climate change has been largely overlooked. Using populations of a marine gastropod (Turbo undulatus) with different thermal histories (cool vs. warm), we compared their physiological adjustments following exposure (8-week) to ocean acidification and warming. Compared to cool-acclimated counterparts, we found that warm-acclimated individuals had higher thermal threshold (i.e. increased CTmax by 2°C), which was unaffected by the exposure to ocean acidification and warming. Thermal history also strongly mediated physiological effects, where warm-acclimated individuals adjusted to warming by conserving energy, suggested by lower respiration and ingestion rates, energy budget (i.e. scope for growth) and O:N ratio. After exposure to warming, warm-acclimated individuals had higher metabolic rates and greater energy budget due to boosted ingestion rates, but such compensatory feeding disappeared when combined with ocean acidification. Overall, we suggest that thermal history can be a critical mediator of physiological performance under future climatic conditions. Given the relatively gradual rate of global warming, marine organisms may be better able to adaptively adjust their physiology to future climate than what short-term experiments currently convey.
Continue reading ‘Long-term thermal acclimation drives adaptive physiological adjustments of a marine gastropod to reduce sensitivity to climate change’Mind your methods: acidification degrades total nitrogen and stable isotopic values within calcified marine macroalgae
Published 26 January 2021 Science ClosedTags: algae, biological response, laboratory, methods, physiology
Nitrogen and carbon are commonly used to determine nutrient regimes and trophic structures within marine ecosystems. Macroalgae are convenient for assessing nutrient conditions via stable isotopes and tissue nutrient levels because of their ability to absorb and integrate ambient nutrients over extended time periods. Calcified macroalgae, such as Halimeda and Udotea spp, are common constituents of tropical marine ecosystems, making them ideal candidates for nutrient-based and food web analyses. However, calcified genera require acidification to remove calcium carbonate to accurately determine δ13C and percentage of N (by weight); the overall effect of acidification on the tissue nutrients and stable isotopes of calcified genera is unresolved. Individuals of Halimeda kanaloana (n = 10) and Udotea geppiorum (n = 9) were collected from Maui, O‘ahu, and Lāna‘i. Each specimen was split into two samples and either decalcified using liquid-phase HCl (acidified) or left unaltered (control). We found that liquid-phase HCl acidification resulted in significantly lower percentage of N in both Halimeda kanaloana and Udotea geppiorum. Whereas δ13C values in acidified samples of both species were predictably lowered, the δ15N in acidified U. geppiorum was significantly increased. Acidification may have unpredictable consequences on both the percentage of nutrients in calcified algal tissue and their δ15N, suggesting that the use of acidification in calcified algal nutrient studies may produce erroneous conclusions. Analysing two sets of samples as calcified (for δ15N) and acidified (for δ13C) would eliminate these errors. However, the use of calcified macroalgae to assess percentage of N should be avoided.
Continue reading ‘Mind your methods: acidification degrades total nitrogen and stable isotopic values within calcified marine macroalgae’Assessing the impact of static and fluctuating ocean acidification on the behavior of Amphiprion percula
Published 26 January 2021 Science ClosedTags: biological response, fish, laboratory, multiple factors, performance
Coral reef organisms are exposed to both an increasing magnitude of pCO2, and natural fluctuations on a diel scale. For coral reef fishes, one of the most profound effects of ocean acidification is the impact on ecologically important behaviors. Previous behavioral research has primarily been conducted under static pCO2 conditions and have recently come under criticism. Recent studies have provided evidence that the negative impacts on behavior may be reduced under more environmentally realistic, fluctuating conditions. We investigated the impact of both present and future day, static (500 and 1000 μatm) and diel fluctuating (500 ± 200 and 1000 ± 200 μatm) pCO2 on the lateralization and chemosensory behavior of juvenile anemonefish, Amphiprion percula. Our static experimental comparisons support previous findings that under elevated pCO2, fish become un-lateralized and lose the ability to discriminate olfactory cues. Diel-fluctuating pCO2 may aid in mitigating the severity of some behavioral abnormalities such as the chemosensory response, where a preference for predator cues was significantly reduced under a future diel-fluctuating pCO2 regime. This research aids in ground truthing earlier findings and contributes to our growing knowledge of the role of fluctuating conditions.
Continue reading ‘Assessing the impact of static and fluctuating ocean acidification on the behavior of Amphiprion percula’Effects of ocean acidification on growth, pigment contents and antioxidant potential of the subtropical Atlantic red alga Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira (Gigartinales) in laboratory
Published 25 January 2021 Science ClosedTags: algae, biological response, laboratory, morphology, photosynthesis, physiology, South Atlantic
Marine ecosystems are subject to several modifications due to anthropogenic impacts, including ocean acidification caused by the absorption of excessive CO2 present in the atmosphere. Perspectives are for dramatic modifications in seawater pH and more than 60% of the ocean surface impacted over the next 100 years by global change. In this study, ocean acidification scenarios were simulated by CO2 enrichment into seawater in three pH levels (8.0, 7.6 and 7.2) using a bioreactor system in laboratory conditions. Experimental evaluation was performed with Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira due to its great importance in coastal marine ecosystems for primary production and commercial interest. Contrary to our initial hypothesis, the growth rate of H. pseudomusciformis decreased significantly with decreased pH conditions, even with increased availability of CO2. The maximum quantum yield and chlorophyll a content were also negatively affected by the pH reduction, while an increase in antioxidant activity was observed, indicating physiological stress. The physiological responses to decreased pH conditions reflect the importance of species-level studies and corroborate the changes caused by the ocean acidification on the macroalgal species.
Continue reading ‘Effects of ocean acidification on growth, pigment contents and antioxidant potential of the subtropical Atlantic red alga Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira (Gigartinales) in laboratory’
