Posts Tagged 'morphology'

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Cellular and genetic responses of Phaeodactylum tricornutum to seawater acidification and copper exposure

Published 2 January 2025 Science Closed
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Highlights

  • Seawater acidification reduced Cu uptake in marine diatom Phaeodactylum tricornutum.
  • Seawater acidification resulted in rougher surfaces, lower adhesion and modulus in the diatom.
  • Diatoms regulated Cu homeostasis via FRE1, CTR1, and ATPase 5-1B transporters.
  • The expression of CTR1 and FRE1 were significantly downregulated in response to seawater acidification.

Abstract

The ongoing decline in seawater pH, driven by the absorption of excess atmospheric CO2, represents a major environmental issue. This reduction in pH can interact with metal pollution, resulting in complex effects on marine phytoplankton. In this study, we examined the combined impacts of seawater acidification and copper (Cu) exposure on the marine diatom Phaeodactylum tricornutum. Our data indicate that elevated pCO2 had a minor effect on the growth and photochemistry and overall performance of P. tricornutum. However, seawater acidification significantly influenced cell size, surface roughness, and adhesion. Higher pCO2 levels led to increased Cu accumulation in P. tricornutum under low ambient Cu concentrations, while significantly reducing Cu accumulation. The smaller cell size and reduced negative charge on the cell surface may explain the decreased Cu accumulation and toxicity. In response to metal stress, P. tricornutum upregulated Cu efflux to mitigate the increased Cu stress in acidified seawater. The expression of the metal transporter gene CTR1 and the reductase gene FRE1 were significantly downregulated, while ATPase5-1B was upregulated in cells exposed to elevated Cu concentrations at 1200 μatm pCO2. Our study provides useful insights into the interactions between metals and diatoms in an increasingly acidified ocean.

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The effect of carbonic anhydrase on foraminiferal Mg/Ca

Published 30 December 2024 Science Closed
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Marine biogenic calcium carbonate production plays a role in the exchange of CO2 between ocean and atmosphere. The effect of increased CO2 on calcification and on the resulting chemistry of shells and skeletons, however, is only partly understood. Foraminifera are among the main marine CaCO3 producers and the controls on element partitioning and isotope fractionation is the subject of many recent investigations. The enzyme carbonic anhydrase (CA) was, for example, shown to be vital for CaCO3 deposition in benthic foraminifera and indicates their ability to manipulate their intracellular inorganic carbon chemistry. Here, we tested whether CA affects the partitioning of Na, Mg and Sr in the perforate, large benthic, symbiont-bearing foraminifer Amphistegina lessonii by addition of the inhibitor acetazolamide (AZ). The effect of dissolved CO2 on the effect of CA on element partitioning was also determined using a culturing setup with controlled atmospheric carbon dioxide levels (400–1,600 ppm). Results show that inhibition by AZ reduces calcification greatly and that CO2 has a small, but positive effect on the amount of calcite formed during the incubations. Furthermore, the inhibition of CA activity has a positive effect on element partitioning, most notably Mg. This may be explained by a (n indirect) coupling of inorganic carbon uptake and inward calcium ion pumping.

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Contrasting responses of commercially important Northwest Atlantic bivalve species to ocean acidification and temperature conditions

Published 23 December 2024 Science Closed
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Modern calcifying marine organisms face numerous environmental stressors, including overfishing, deoxygenation, increasing ocean temperatures, and ocean acidification (OA). Coastal marine settings are predicted to become warmer and more acidic in coming decades, heightening the risks of extreme events such as marine heat waves. Given these threats, it is important to understand the vulnerabilities of marine organisms that construct their shells from calcium carbonate, which are particularly susceptible to warming and decreasing pH levels. To investigate the response of four commercially relevant bivalve species to OA and differing temperatures, juvenile Mercenaria mercenaria (hard shell clams), juvenile Mya arenaria (soft shell clams), adult and juvenile Arctica islandica (ocean quahog), and juvenile Placopecten magellanicus (Atlantic sea scallops) were grown in varying pH and temperature conditions. Species were exposed to four controlled pH conditions (7.4, 7.6, 7.8, and ambient/8.0) and three controlled temperature conditions (6, 9, and 12°C) for 20.5 weeks and then shell growth and coloration were analyzed. This research marks the first direct comparison of these species’ biological responses to both temperature and OA conditions within the same experiment. The four species exhibited varying responses to temperature and OA conditions. Mortality rates were not significantly associated with pH or temperature conditions for any of the species studied. Growth (measured as change in maximum shell height) was observed to be higher in warmer tanks for all species and was not significantly impacted by pH. Two groups (juvenile M. arenaria and juvenile M. mercenaria) exhibited lightening in the color of their shells at lower pH levels at all temperatures, attributed to a loss of shell periostracum. The variable responses of the studied bivalve species, despite belonging to the same phylogenetic class and geographic region, highlights the need for further study into implications for health and management of bivalves in the face of variable stressors.

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Coexisting mangrove-coral habitats: trends in seawater chemistry and coral diversity

Published 20 December 2024 Science Closed
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Coral reefs face unprecedented threats from climate change, with rising temperatures, ocean acidification, and other stressors endangering their survival. Coexisting mangrove-coral (CMC) habitats provide a natural laboratory to study coral resilience under extreme conditions. However, these habitats are rare and understudied, leaving gaps in understanding their biogeochemical and ecological dynamics. This thesis examines how mangrove proximity influences seawater chemistry, coral diversity, and morphology. A global review identified differences in seawater chemistry between habitat types and regions, driven by biogeochemical processes and freshwater inputs. Edge habitats, particularly in the Great Barrier Reef (GBR), were identified as understudied. An empirical study at Pioneer Bay, GBR, revealed significant spatial and temporal variations in seawater chemistry along a gradient from mangroves to open reefs. Corals near mangroves experienced greater fluctuations in pH, temperature, and oxygen, stabilizing with distance. Tidal flushing mitigated extremes, fostering coral resilience. Mangrove proximity significantly influenced benthic communities, coral morphology, and biodiversity. Extreme conditions near mangroves favored resilient corals like *Porites*, while intermediate sites supported the highest diversity due to nutrient influx and moderate disturbances. Farther sites were dominated by complex coral communities. Edge CMC habitats play a vital role in supporting coral adaptation to climate change. However, intensifying stressors threaten even resilient systems, underscoring the need for long-term monitoring and adaptive management to protect these critical biodiversity hotspots.

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Sensitivity of pteropod calcification to multi stressor variability in coastal habitats

Published 18 December 2024 Science , Uncategorized Closed
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Highlights

  • Pteropod calcification under coastal multiple stressors was investigated.
  • Shell morphometrics and high-resolution model outputs was combined.
  • Saturation state, temperature and food are drivers of calcification.
  • Different calcification modes are dependent on the type of environment.
  • Stable vs dynamic conditions induce different calcification strategy.

Abstract

Comprehensive understanding of environmental multiple stressors on calcification in marine calcifiers remains an important topic of study, especially under ocean global change associated with multiple stressors. We explore the impact of multiple stressor variability on pteropod calcification in the southern Salish Sea (Washington, U.S.), a coastal estuarine system that exhibits a high degree of spatial and temporal variability in multiple environmental parameters across sampling locations. We hypothesized that such variability is associated with differences in pteropod calcification. Shell thickness and shell density across pteropod life history stages was compared with high-resolution outputs from a realistic model of regional circulation and biogeochemistry to explore how the mean and variability of multiple stressors (aragonite saturation state (Ωar), temperature, food availability) influence calcification. We found that both the mean and variability in multiple stressors play a major role in calcification in pteropods, with a generalized linear model explaining more than 60% of the variance in calcification. We suggest two different modes of shell building: stable conditions of lower mean Ωar trigger the loss of shell thickness and density. In the more variable habitats, i.e., where the variability occurs over diel and seasonal scales, shell thickness increases at higher Ωar variability and greater food availability, which might partially compensate for the loss of shell density. This plastic response appears to be consistent across life stages and could represent a response mechanism that allows some compensatory calcification under less favourable conditions. However, compensation is very limited, as evident by lower shell growth resulting in lower shell sizes comparable to early life stages. These results substantially improve the understanding of the variability in multiple stressors on the calcification process under multiple stressors and provide a foundation for the development of two new proxies for calcification monitoring, and with implications for marine carbon dioxide removal strategies.

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Differential impacts of pH on growth, physiology, and elemental stoichiometry across three coccolithophore species

Published 10 December 2024 Science Closed
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Coccolithophores are pivotal players in ocean biogeochemistry, yet the impact of changing pH on the physiology of different species remains unclear as there has been a dominant focus on Gephyrocapsa huxleyi. Meta-analyses of existing experimental data are challenging due to the differences in multidimensional culture conditions. This study investigated the response of three species—Gephyrocapsa huxleyi, Coccolithus braarudii, and Chrysotila carterae—under varying CO2 conditions (via pH). The sensitivity to pH differed between species, but all species showed reduced growth rates under the highest CO2 (lowest pH) treatment possibly due to high [H+]-related inhibition. Low pH impacted cellular physiology and elemental stoichiometry, while the impact of high pH was less adverse. The changes in elemental production induced by low pH could exert a negative influence on the contribution of coccolithophores to nutrient and carbon export, especially for biogeochemically relevant open-ocean species. pH also affected coccolith formation, especially in C. braarudii, through CO2 limitation at high pH and low calcite saturation state at low pH. Contrasting species-specific pH sensitivities highlighted the potential for species like G. huxleyi to further outperform others like C. braarudii in an acidic ocean. Literature synthesis showed that coccolithophores show a broad CO2 optimum, although growth rates and particulate inorganic carbon to particulate organic carbon ratios consistently declined with increasing CO2. Strain-specific CO2 optima partly contributed to the variability within responses of individual species, giving the misleading perception of a broad species-level CO2 optimum. Strain-specific optima exist possibly due to their adaptation to carbonate chemistry conditions at the place of origin.

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Effects of ocean acidification on abalone (Haliotis spp.) reproduction, early development, and growth: a review

Published 5 December 2024 Science Closed
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Abalone (Haliotis spp.) is a highly valuable and economically relevant marine commodity worldwide, with its production and value showing significant growth over the past two decades. Additionally, abalone hold essential ecological value by serving as a grazer and providing a microhabitat for various benthic organisms. Currently, seawater is experiencing a decrease in pH due to increased carbon dioxide (CO2) levels. It is projected that by 2100, the pH of seawater will decrease by approximately 0.3–0.4 units, with this trend continuing to 0.7–0.8 units by 2300. Abalone is particularly susceptible to ocean acidification due to its limited ability to maintain acid-base balance. Moreover, even if the effects on abalone are not lethal, world production values and ecosystem balance are likely to be impacted. This review examines the economic and ecological significance of abalone, as well as the morphological and physiological effects of ocean acidification on abalone during its early development, juvenile, and adult stages based on previous studies. In summary, the adverse effects of ocean acidification on abalone depend on several aspects, including the species, developmental stage, size, and duration of exposure.

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Physiological and behavioral responses of the Baltic clam Macoma balthica to a laboratory simulated CO2-leakage from a subseabed carbon storage site

Published 3 December 2024 Science Closed
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Highlights

  • Baltic clams were exposed to CO2 leakage simulated in laboratory conditions.
  • Physiological and behavioral responses of the model organism were evaluated.
  • Shell growth in thickness and length were inhibited at pH 6.3.
  • Biochemical composition, condition index and burrowing depth results were inconclusive.

Abstract

Carbon capture and storage in sub-seabed geological reservoirs is now officially included in the atmospheric CO2 emissions reduction policy and meets the agenda of Sustainable Development Goals (SDGs). Over the last few years biological risk assessment studies have delivered substantial empirical data on possible consequences of CO2 leakages from underwater storage sites on benthic systems. Current knowledge on Carbon Capture and Storage CCS associated risks is limited to marine systems. Yet there are multiple areas identified as suitable for carbon storage, but their hydrogeochemical features are so distinct that they should be studied as separate cases. Baltic Sea is one example of an area but is host to a unique – in a world scale – ecosystem with low salinity in combination with reduced oxygen availability in the benthic zone. Geological surveys have designated a potential storage site in the Southern Baltic Sea, namely the B3 oil field. Thus, this study focuses on biological effects of seawater acidification caused by a simulated CO2 leakage scenarios under laboratory conditions on a model macrobenthic in-faunal species. Baltic clams Macoma balthica were exposed to different environmental pH scenarios: pH 7.7 (no leakage), pH 7.0 (moderate hypercapnia) and pH 6.3 (severe hypercapnia) in three independent experiments conducted with the use of a hyperbaric tank (Karl Eric Titank) mimicking hydrostatic pressure of 900 kPa, relevant to conditions at the B3 field. Selected physiological aspects of the Baltic clam, such as survival, shell growth rate, morphometric condition and biochemical composition were investigated along with their behavioral responses, i.e. sediment burrowing activity. The results showed modest effects of hypercapnia on physiological performance of the clams that did not lead to greater mortality in neither of the tested leakage scenarios. Apart from high survival of the clams even in the lowest seawater pH (6.3) there were only little changes observed in the burrowing depth of the clams and biochemical composition of their soft tissues related to seawater acidification. The most evident physiological responses of the clams to prolonged hypercapnia (40 days at pH 6.3) were manifested in decreased shell growth.

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Acidification and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary

Published 27 November 2024 Science Closed
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Coastal acidification, warming, and nutrient management actions all alter water quality conditions that marine species experience, with potential impacts to their physiological processes. Decreases in calcite saturation state (ΩCa) and food availability, combined with warming water temperatures, pose a threat to calcifying organisms; however, the magnitude of future changes in estuarine systems is challenging to predict and is not well known. This study aims to determine how and where oysters will be affected by future acidification, warming, and nutrient reductions, and the relative effects of these stressors. To address these goals, an oyster bioenergetics model for Eastern oysters (Crassostrea virginica) was embedded in a 3-D coupled hydrodynamic-biogeochemistry model implemented for two tributaries in the lower Chesapeake Bay. Model simulations were forced with projected future conditions (mid-21st century atmospheric CO2, atmospheric temperature, and managed nutrient reductions) and compared with a realistic present-day reference run. Together, all three stressors are projected to reduce ΩCa and growth of oyster shell and tissue. Increased atmospheric CO2 and temperature are both projected to cause widespread reductions in ΩCa. The resulting reductions in oyster shell and tissue growth will be most severe along the tributary shoals. Future warming during peak oyster growing seasons is projected to have the strongest negative influence on tissue and shell growth, due to summer water temperatures reducing filtration rates, enhancing shell dissolution and oyster respiration rates, and increasing organic matter remineralization rates, thus reducing food availability. Nutrient reductions will exacerbate deficits in oyster food availability, contributing to further reductions in growth. Quantifying the effects of these stressors provides insight on the areas in the lower bay where oysters will be most vulnerable to mid 21st-century conditions.

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Performance of Acanthina monodon juveniles under long-term exposure to predicted climate change conditions

Published 27 November 2024 Science Closed
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Highlights

  • Combination of increasing temperature and decreasing pH increased juvenile shell growth.
  • Decrease in pH has a negative effect on shell strength.
  • Juveniles exposed to the higher temperature attached strongly to substrate.
  • Under prolonged exposure, juveniles appear to compensate for high temperature/low pH stress.
  • PCO2/temperature interaction had no effect on metabolic rate or juvenile survival.

Abstract

The increase of anthropogenic CO2 in the Earth’s atmosphere reduces the pH and raises the temperature of the oceans. The combination of both factors impacts the physiological responses and calcium carbonate structures of marine organisms. This study assessed the performance of the juvenile stage of the gastropod Acanthina monodon, after it was continuously exposed to treatments at two pCO2 levels (400 and 1200 μatm) at two temperatures (10 °C and 15 °C) during the periods of embryonic encapsulated development and the early post-hatching juvenile stage. Juvenile performance was evaluated by quantifying shell growth, survival, foot adhesion strength, shell breakage resistance, and oxygen consumption rates. The results indicate that the combination of increased temperature and decreased pH increased juvenile shell growth, while only the decrease in pH had a negative effect on shell strength. However, juveniles were able to attach more strongly to substrates following exposure to the higher temperature level. Furthermore, the interaction of treatments had no effect on the metabolic rate or survival of juveniles, suggesting a possible compensatory effect of the juveniles to the more adverse conditions to which they were exposed.

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Assessment of ocean acidification impact on gastropod shells using geometric morphometrics

Published 21 November 2024 Science Closed
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To evaluate the effects of ocean acidification (OA) on the shell morphology of the gastropods, three different populations of Planaxis sulcatus (Born) in the South China Sea (Coast of Borneo) were investigated. All sites are natural rocky shores sharing a very similar geologic setting of the intertidal zone including, water depth, beach topography, and wave energy. The population densities observed during sampling were similar across all three study sites. However, one population lives under low pH due to geochemical discharge from acidic soils (site E), while the other two populations live under higher pH levels (T and U sites). Quantitative analyses of the shell shape using geometric morphometrics demonstrated that OA had a significant effect on the shell morphology, demonstrating that both allometric growth and the calcification process were affected. Shells from the acidified sites were more rounded and had smaller apertures. Moreover, shell size was significantly reduced as a response to OA stress. These shell changes may have arisen to reduce the cost of shell maintenance. As there is also a significant salinity difference among sites, salinity may have influenced the shell shape of the gastropod Planaxis sulcatus and therefore, the role of OA should be examined in areas where all other physicochemical variables are the same.

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Ecophenotypic variation in a cosmopolitan reef-building coral suggests reduced deep-sea reef growth under ocean change

Published 7 November 2024 Science Closed
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Sensitivity of reef-building corals to environmental factors has far-reaching ecosystem implications, especially in the limited number of cold-water coral (CWC) species that form reefs in the deep sea. Understanding CWC responses to large-scale oceanographic variation in their natural habitat can elucidate their sensitivity to global anthropogenic stressors. Here, we use skeletal samples to analyse fine-scale phenotypic variation in the widespread reef-building CWC Desmophyllum pertusum (Lophelia pertusa) in relation to broad physicochemical gradients in different sites across the Atlantic Ocean and Mediterranean Sea. We find evidence, amidst local and regional differentiation, of species-wide growth responses to physicochemical factors, mainly affecting corallite length, width and their ratio (slenderness). Our results suggest that higher temperature and lower oxygen levels negatively affect skeletal linear extension and budding rate of polyps. As also hinted by the reduced corallite length and slenderness in less developed reefs, these widespread responses may lead to a general decline in CWC reef growth rates as a long-term consequence of ocean warming and deoxygenation. Given this relevance, such responses can be used to model reef growth in a changing ocean.

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Environmental behavior and toxic effects of micro(nano)plastics and engineered nanoparticles on marine organisms under ocean acidification: a review

Published 5 November 2024 Science Closed
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Ocean acidification (OA) driven by human activities and climate change presents new challenges to marine ecosystems. At the same time, the risks posed by micro(nano)plastics (MNPs) and engineered nanoparticles (ENPs) to marine ecosystems are receiving increasing attention. Although previous studies have uncovered the environmental behavior and the toxic effects of MNPs and ENPs under OA, there is a lack of comprehensive literature reviews in this field. Therefore, this paper reviews how OA affects the environmental behavior of MNPs and ENPs, and summarizes the effects and the potential mechanisms of their co-exposure on marine organisms. The review indicates that OA changes the marine chemical environment, thereby altering the behavior of MNPs and ENPs. These changes affect their bioavailability and lead to co-exposure effects. This impacts marine organisms’ energy metabolism, growth and development, antioxidant systems, reproduction and immunity. The potential mechanisms involved the regulation of signaling pathways, abnormalities in energy metabolism, energy allocation, oxidative stress, decreased enzyme activity, and disruptions in immune and reproductive functions. Finally, based on the limitations of existing research, actual environment and hot issues, we have outlined future research needs and identified key priorities and directions for further investigation. This review deepens our understanding of the potential effects of MNPs and ENPs on marine organisms under OA, while also aiming to promote further research and development in related fields.

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Improved growth performance and physiological state in hybrid abalone (Haliotis rufescens and Haliotis fulgens) facing ocean acidification conditions

Published 1 November 2024 Science Closed
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Highlights

  • Hybrid vigor in abalones evaluated under future ocean acidification scenarios.
  • Hybrid cross abalone show positive heterosis on biological performance.
  • More robust metabolic response observed in hybrids than in pure abalone crosses.
  • Higher heterosis for survival and shell growth reached at pH 7.8 conditions.
  • Interspecific hybridization yield resilient cross withstand ocean acidification.

Abstract

Abalone (Haliotis spp.) is a valuable global aquaculture resource in Mexican abalone industry, particularly red (Haliotis rufescens) and green (H. fulgens) abalone, showing significant growth. However, climate change -particularly ocean acidification (OA)- threatens production by negatively impacting mollusks, leading to recruitment failures, poor fertilization, malformations, and reduced calcification and growth jeopardizing sustainability and food security. This study aims to assess robustness of a hybrid abalone cross RF (H. rufescens ♀ x H. fulgens ♂) to OA conditions by evaluating biological performance (survival, growth in weight and length) and metabolic response (oxygen consumption, ammonia excretion rate, and atomic O:N ratio). Juveniles from hybrid RF cross and two pure parental crosses (RR, FF) were exposed to three pH levels: control (pH ≈ 8.0) and two reduced pH scenarios (pH 7.8 and 7.5), representing moderate and severe OA conditions. The results showed hybrid cross exhibiting better growth and metabolic response than pure crosses under all conditions. Notably, hybrid length growth was superior under moderate OA conditions (pH 7.8) compared to control (pH 8.0) and intense OA conditions (pH 7.5). Enhanced physiological hybrid status was evidenced by increased oxygen consumption and stable ammonia excretion, reflected in higher atomic O:N ratio. This study demonstrates hybrid cross RF robustness under OA conditions and supports interspecific hybridization as potential mitigation strategy to alleviate negative OA effects for sustainable abalone production.

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Chapter 1 – Overview: ocean acidification and marine mollusks

Published 18 October 2024 Science Closed
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Ocean acidification, resulting from elevated CO2 levels in the atmosphere, has considerable effects on marine mollusks. This chapter presents a comprehensive overview of the consequences of ocean acidification on marine mollusks, with a specific focus on gastropods, bivalves, and cephalopods. Mollusks with CaCO3-deposited shells are especially susceptible to ocean acidification, as it disrupts their calcification process. The diminished pH of seawater impedes the capability of marine mollusks to create and uphold their calcium carbonate shells, resulting in a decline in shell growth and overall shell strength. The extent of the reduction in calcification varies depending on the polycrystalline structure of CaCO3 secreted by the mollusks, their acid–base regulation, and their local physicochemical surroundings. Ocean acidification affects the physiological processes and metabolic rates of marine mollusks, potentially impacting their ability to allocate resources for calcification. It also negatively impacts reproduction, as ocean acidification increases the energy cost of physiological processes, consequently affecting energy allocation and reproductive capacity. The sustainability of shellfish populations is under threat from the adverse impacts of ocean acidification on mollusk reproduction and shell durability.

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Ecophysiology and ocean acidification in marine mollusks: from molecule to behavior

Published 17 October 2024 Science Closed
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Ecophysiology and Ocean Acidification in Marine Mollusks: From Molecule to Behavior provides an extensive overview of the latest research on the various ecophysiological effects of ocean acidification on marine mollusks. This book synthesizes historical information and recent findings on the effects of environmental change, ocean warming, and acidification on key mollusks and their life-history. It also discusses the underlying mechanisms underpinning the effects of ocean warming and acidification. Written by internationally recognized experts in the field of marine biology, this book systematically examines the effects of ocean acidification on the reproduction, growth and development, physiological metabolism, immunity, and behavior of marine mollusks.

The book concludes by discussing the implications of current research, acknowledging data limitations in the field, and proposing future research directions, providing a better understanding of the potential impacts of ocean acidification on mollusks and the global aquaculture industry and inspiring new thinking for future research practices. It will be an indispensable resource for researchers, practitioners, undergraduate and graduate students, conservationists, and aquaculturists alike who are interested in marine environmental change, ecology, physiology, and marine biology.

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Low sensitivity of a heavily-calcified coccolithophore under increasing CO2: the case study of Helicosphaera carteri

Published 17 October 2024 Science Closed
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Studies on CO2 effects on coccolithophores, unicellular calcifying phytoplankton, show species-specific responses, although only less than 5 % of the ~280 living species have been tested so far. Helicosphaera carteri significantly contributes to carbon fluxes and CaCO3 storage due to its size and high calcite production. Despite its importance, few studies have examined H. carteri under experimental conditions, and only one has addressed the effects of rising CO2/decreasing pH. Being H. carteri a large-sized, obligated calcifier species, an important aspect to understand is how changes in seawater carbonate chemistry may affect its morphology. It has already been suggested for other coccolithophores species, that the presence of malformed coccoliths may represent a disadvantage for these organisms. Moreover, an alteration in coccolith morphology may affect their contribution to CaCO3 sedimentation and ballasting. As for H. carteri, it has also been suggested that due to its high PIC:POC ratio, the species could show a high-sensitivity to CO2 rise. In this study, we investigate for the first time whether high pCO2/low pH does affect the morphology of H. carteri coccoliths, by culturing this species under pre-industrial CO2 levels (~295 µatm) and ~600 µatm, i.e., the SSP 2-4.5 scenario for 2100 (IPCC, 2021). We also analyzed cellular PIC and POC quotas using morphometric data, roundness, and protoplast and coccosphere size to observe the pCO2 influence on the calcification and photosynthesis ratio.

Our results indicate that H. carteri morphology is only slightly affected by increasing CO2, in contrast to other heavily calcified species. Helicosphaera carteri protoplast and coccosphere shapes did not vary with changes in CO2, indicating unaltered general health. The low PIC:POC ratio found in this work for H. carteri compared to ratios previously measured in the same strain under different experimental conditions, and compared to other highly-calcified species, could explain the observed low sensitivity of H. carteri to CO2. Moreover, the observation of a stable ratio between calcification and photosynthesis in H. carteri under increasing CO2 might suggest a constant contribution to the rain ratio under climate change. However, further studies comparing experimental and field data from past ocean acidification events will be required to confirm the conclusions drawn here.

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Impact of warming and acidification of the Mediterranean Sea on statolith formation of the scyphozoan jellyfish Rhizostoma pulmo Macri (1778)

Published 16 October 2024 Science Closed
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Highlights

  • R. pulmo ephyrae statoliths size is affected by ocean warming and acidification.
  • Bigger statoliths are produced due to warming, but smaller under acidification.
  • Number of statoliths in R. pulmo ephyrae do not depend on temperature nor acidity.
  • R. pulmo statoliths composition is not altered due to temperature or acidification.
  • Survivability of jellyfishes could be affected by ocean warming and acidification.

Abstract

Ocean warming and acidification negatively affect organisms and biogeochemical cycles. To date, emphasis has been placed on the study of the impact on the structures of calcifying species; however, there is limited knowledge about the influence of the increase of these two variables on the solid structures of non-calcifying species as jellyfish. Here, we study the effects that the increase of temperature and acidity would cause on the statoliths of newly released ephyrae of the Mediterranean jellyfish Rhizostoma pulmo. Six combinations of temperature and PCO2 (18, 24 and 30ºC with a PCO2 of 500 and 1000 ppm each), according to the projections of the SSP5-8.5 (IPCC, 2021) scenario for the year 2100, were applied during 32 days to different groups of polyps randomly selected. Statoliths of the released ephyrae were counted and their size was measured. Our results show that, even though neither temperature nor PCO2 increase exerted a representative effect on the amount of statoliths synthesized in newly released ephyra from R. pulmo, it did exert an impact on the size of these structures: warming led to the formation of larger statoliths, while the rise in PCO2 induced the production of smaller structures. Under the simultaneous increase of both variables, acidification attenuated the effects of temperature, but still slightly larger statoliths were synthesized. The size differences observed in these structures could negatively impact the equilibrium system of this jellyfish species, potentially affecting its ability to survive.

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Shifting seagrass-oyster interactions alter species response to ocean warming and acidification

Published 16 October 2024 Science Closed
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  1. A major challenge in biodiversity research is the incorporation of species interactions into frameworks describing population and community response to global edfnmental change (GEC). Mutualisms are a type of species interaction especially sensitive to changing environmental conditions, and the breakdown of facilitative species interactions could amplify the negative impacts of novel climate regimes on focal species.
  2. Here, we investigate how reciprocal interactions between two coastal foundation species, the eastern oyster (Crassostrea virginica) and eelgrass (Zostera marina) shift in sign and magnitude in response to ocean warming (+1.5°C) and acidification (−0.4 pH) via a manipulative co-culture experiment in mesocosms.
  3. Under ambient environmental conditions, oysters facilitated eelgrass leaf growth and clonal reproduction by 35% and 38%, respectively. Simultaneously, eelgrass decreased the oyster condition index (the ratio of tissue to shell biomass) by 35%, indicating greater allocation of energy to shell growth instead of soft tissues at ambient conditions. Varying sensitivities of each species to ocean warming and/or acidification treatments led to complex shifts in species interactions that were trait dependent. As such, community outcomes under future conditions were influenced by species interactions that amplified and mitigated species response to environmental change.
  4. Synthesis: Given that species interaction effect sizes were similar in magnitude to effect sizes of warming or pH treatments, our results underscore the need to identify key species and interaction types that strongly influence community response to GEC. Specifically, for macrophyte-bivalve interactions, understanding how physiological limitations on growth are impacted by environmental heterogeneity and co-culture will support the successful restoration of natural populations and the rapid expansion of aquaculture.
Continue reading ‘Shifting seagrass-oyster interactions alter species response to ocean warming and acidification’

Could future ocean acidification be affecting the energy budgets of marine fish?

Published 14 October 2024 Science Closed
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With the unprecedented environmental changes caused by climate change including ocean acidification, it has become crucial to understand the responses and adaptive capacity of fish to better predict directional changes in the ecological landscape of the future. We conducted a systematic literature review to examine if simulated ocean acidification (sOA) could influence growth and reproduction in fish within the dynamic energy budget theory framework. As such, we chose to examine metabolic rate, locomotion, food assimilation and growth in early life stages (i.e. larvae and juvenile) and adults. Our goal was to evaluate if acclimatization to sOA has any directional changes in these traits and to explore potential implications for energetic trade-offs in these for growth and reproduction. We found that sOA had negligible effects on energetic expenditure for maintenance and aerobic metabolism due to the robust physiological capacity regulating acid–base and ion perturbations but substantive effects on locomotion, food assimilation and growth. We demonstrated evidence that sOA significantly reduced growth performance of fish in early life stages, which may have resulted from reduced food intake and digestion efficiency. Also, our results showed that sOA may enhance reproduction with increased numbers of offspring although this may come at the cost of altered reproductive behaviours or offspring fitness. While these results indicate evidence for changes in energy budgets because of physiological acclimatization to sOA, the heterogeneity of results in the literature suggests that physiological and neural mechanisms need to be clearly elucidated in future studies. Lastly, most studies on sOA have been conducted on early life stages, which necessitates that more studies should be conducted on adults to understand reproductive success and thus better predict cohort and population dynamics under ongoing climate change.

Continue reading ‘Could future ocean acidification be affecting the energy budgets of marine fish?’

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