Posts Tagged 'multiple factors'

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Differential effects of ocean acidification and warming on biological functioning of a predator and prey species may alter future trophic interactions

Published 23 February 2023 Science Closed
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Highlights

  • Multiple environmental stressors act upon multiple trophic levels.
  • Mollusc predator and prey respond differently to future climate scenarios.
  • Prey are negatively impacted physiologically and behaviourally.
  • Predators unaffected resulting in elevated predation risk for prey.
  • Potential for fundamental change in trophic interactions affecting biodiversity.

Abstract

Independently, ocean warming (OW) and acidification (OA) from increased anthropogenic atmospheric carbon dioxide are argued to be two of the greatest threats to marine organisms. Increasingly, their interaction (ocean acidification and warming, OAW) is shown to have wide-ranging consequences to biological functioning, population and community structure, species interactions and ecosystem service provision. Here, using a multi-trophic experiment, we tested the effects of future OAW scenarios on two widespread intertidal species, the blue mussel Mytilus edulis and its predator Nucella lapillus. Results indicate negative consequences of OAW on the growth, feeding and metabolic rate of M. edulis and heightened predation risk. In contrast, Nucella growth and metabolism was unaffected and feeding increased under OAW but declined under OW suggesting OA may offset warming consequences. Should this differential response between the two species to OAW, and specifically greater physiological costs to the prey than its predator come to fruition in the nature, fundamental change in ecosystem structure and functioning could be expected as trophic interactions become disrupted.

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Antagonism toxicity of CuO nanoparticles and mild ocean acidification to marine algae

Published 22 February 2023 Science Closed
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Graphical abstract

The toxicity of CuO nanoparticles (NPs) to marine microalgae (Emiliania huxleyi) under ocean acidification (OA) conditions (pHs 8.10, 7.90, 7.50) was investigated. CuO NPs (5.0 mg/L) caused significant toxicity (e.g., 48-h growth inhibition, 20%) under normal pH (8.10), and severe OA (pH 7.50) increased the toxicity of CuO NPs (e.g., 48-h growth inhibition, 68%). However, toxicity antagonism was observed with a growth inhibition (48 h) decreased to 37% after co-exposure to CuO NPs and mild OA (pH 7.90), which was attributed to the released Cu2+ ions from CuO NPs. Based on biological responses as obtained from RNA-sequencing, the dissolved Cu2+ ions (0.078 mg/L) under mild OA were found to increase algae division (by 17%) and photosynthesis (by 28%) through accelerating photosynthetic electron transport and promoting ATP synthesis. In addition, mild OA enhanced EPS secretion by 41% and further increased bioavailable Cu2+ ions, thus mitigating OA-induced toxicity. In addition, excess Cu2+ ions could be transformed into less toxic Cu2S and Cu2O based on X-ray absorption near-edge spectroscopy (XANES) and high-resolution transmission electron microscopy (HR-TEM), which could additionally regulate the antagonism effect of CuO NPs and mild OA. The information advances our knowledge in nanotoxicity to marine organisms under global climate change.

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Responses of free-living planktonic bacterial communities to experimental acidification and warming

Published 20 February 2023 Science Closed
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Climate change driven by human activities encompasses the increase in atmospheric CO2 concentration and sea-surface temperature. Little is known regarding the synergistic effects of these phenomena on bacterial communities in oligotrophic marine ecosystems that are expected to be particularly vulnerable. Here, we studied bacterial community composition changes based on 16S rRNA sequencing at two fractions (0.1–0.2 and >0.2 μm) during a 10- day fully factorial mesocosm experiment in the eastern Mediterranean where the pH decreased by ~0.3 units and temperature increased by ~3 °C to project possible future changes in surface waters. The bacterial community experienced significant taxonomic differences driven by the combined effect of time and treatment; a community shift one day after the manipulations was noticed, followed by a similar state between all mesocosms at the third day, and mild shifts later on, which were remarkable mainly under sole acidification. The abundance of Synechococcus increased in response to warming, while the SAR11 clade immediately benefited from the combined acidification and warming. The effect of the acidification itself had a more persistent impact on community composition. This study highlights the importance of studying climate change consequences on ecosystem functioning both separately and simultaneously, considering the ambient environmental parameters.

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Similarities in biomass and energy reserves among coral colonies from contrasting reef environments

Published 16 February 2023 Science Closed
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Coral reefs are declining worldwide, yet some coral populations are better adapted to withstand reductions in pH and the rising frequency of marine heatwaves. The nearshore reef habitats of Palau, Micronesia are a proxy for a future of warmer, more acidic oceans. Coral populations in these habitats can resist, and recover from, episodes of thermal stress better than offshore conspecifics. To explore the physiological basis of this tolerance, we compared tissue biomass (ash-free dry weight cm−2), energy reserves (i.e., protein, total lipid, carbohydrate content), and several important lipid classes in six coral species living in both offshore and nearshore environments. In contrast to expectations, a trend emerged of many nearshore colonies exhibiting lower biomass and energy reserves than colonies from offshore sites, which may be explained by the increased metabolic demand of living in a warmer, acidic, environment. Despite hosting different dinoflagellate symbiont species and having access to contrasting prey abundances, total lipid and lipid class compositions were similar in colonies from each habitat. Ultimately, while the regulation of colony biomass and energy reserves may be influenced by factors, including the identity of the resident symbiont, kind of food consumed, and host genetic attributes, these independent processes converged to a similar homeostatic set point under different environmental conditions.

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Morphology and stable isotope ecology of Pleuroncodes planipes adult life stages and their vulnerability to climate change stressors

Published 16 February 2023 Science Closed
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Like many in Southern California during the 2015/16 El Niño event, I was struck by the presence of thousands of bright red tuna crabs (Pleuroncodes planipes) abundant at sea and washing ashore. Their sudden prevalence inspired me to learn more about these fascinating animals. Despite drawing so much attention, basic details related to their feeding behaviors and life history remain unknown. P. planipes have long been thought, but never confirmed, to experience a unique life history among crustaceans during which they undergo a sequential habitat shift from pelagic to benthic as adults. In this dissertation research, I applied contemporary methods of stable isotope ecology in combination with ecomorphology to examine aspects of their life history relevant to their pelagic and benthic life stages. We further assessed their vulnerability to the climate change stressors of ocean acidification and ocean warming through a long-term experiment. Through this work, we uncovered morphological differences and an ontogenetic diet shift between pelagic and benthic adult stages as well as significant impacts of temperature, but not pCO2/pH on molting and growth in pelagic adults. These results provide the first evidence in support of the hypothesis that P. planipes adult pelagic and benthic stages are distinct and yield important insight into how this transition could be impacted as the oceans continue to change.

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Season-specific impacts of two projected climate scenarios on intertidal seaweed communities

Published 15 February 2023 Science Closed
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Predictions regarding the ecological impacts of future climate change often lack nuance when they rely on studies that focus on a single species under one future scenario. The inclusion of factors such as seasonality, multiple projected climate scenarios, and community-level interactions, which can alter how climate related stressors affect a species, will lead to more holistic and well-informed predictions. Rockweeds, such as Silvetia compressa, whose canopies support diverse understory communities, can have strong responses to climate change when in conjunction with these other factors due to narrow tolerance thresholds and tightly coupled species interactions. Therefore, we chose to assess the impacts of climate change on Silvetia by subjecting simplified Silvetia assemblages to elevated temperature and pCO2 in a mesocosm environment. Due to the uncertainty of future climate trajectories and the potential interactions with seasonality, we tested these stressors under two IPCC projected climate scenarios (RCP 2.6 & 4.5) in both the summer and winter. This was coupled with a field experiment involving Silvetia removal to simulate the effect of climate mediated Silvetia loss on natural assemblages. We found that Silvetia abundance declined under RCP 4.5 in both seasons, and this loss of canopy led to shifts in the understory algal assemblage. In contrast, Silvetia increased under RCP 2.6 in the winter, which resulted in an understory assemblage comparable to those observed under ambient conditions. These results indicate that while most future scenarios will reduce present-day Silvetia communities, some scenarios may lead to their recovery. Given these varied results, future experimental climate change research on similarly structured communities should consider seasonality, multiple climate change scenarios, and species interactions in their designs.

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Life-stage-dependent effects of multiple flood-associated stressors on a coastal foundational species

Published 15 February 2023 Science Closed
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Global changes in precipitation patterns have increased the frequency and duration of flooding events. Freshwater inflows into estuaries reduce salinity levels and increase nutrient inputs, which can lead to eutrophication and impaired water quality. Oysters are important ecosystem engineers in coastal environments that are vulnerable to co-occurring environmental stressors associated with freshwater flooding events. Successful recruitment is necessary to maintain adult oyster populations, but early life stage responses to multiple stressors are not well understood. Flood-associated stressor conditions were observed near oyster habitats at multiple locations across the northern Gulf of Mexico during peak recruitment months in the spring and summer of 2021. In the laboratory, we examined the interactive effects of acidification, hypoxia, and low salinity on larval and juvenile life stages of the eastern oyster (Crassostrea virginica) to better understand the impact of flooding events on oyster development and survival. Salinity stress in isolation reduced larval growth and settlement, and decreased survival and growth at the juvenile stage. Hypoxia was more stressful to oyster larvae than to juveniles, whereas low pH had negative effects on juvenile growth. There were no synergistic effects of multiple flood-associated stressors on early oyster life stages and effects were either additive or predicted by the salinity stress response. The negative impacts of flooding disturbances on recruitment processes in benthic populations need to be considered in restoration planning and flood control mitigation strategies as the frequency and intensity of extreme freshwater events continue to rise worldwide.

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Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification

Published 14 February 2023 Science Closed
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Ocean warming (OW) and acidification (OA) are recognized as two major climatic conditions influencing phytoplankton growth and nutritional or toxin content. However, there is limited knowledge on the responses of harmful algal bloom species that produce toxins. Here, the study provides quantitative and mechanistic understanding of the acclimation and adaptation responses of the domoic acid (DA) producing diatom Pseudo-nitzschia multiseries to rising temperature and pCO2 using both a one-year in situ bulk culture experiment, and an 800-day laboratory acclimation experiment. Ocean warming showed larger selective effects on growth and DA metabolism than ocean acidification. In a bulk culture experiment, increasing temperature +4 °C above ambient seawater temperature significantly increased DA concentration by up to 11-fold. In laboratory when the long-term warming acclimated samples were assayed under low temperatures, changes in growth rates and DA concentrations indicated that P. multiseries did not adapt to elevated temperature, but could instead rapidly and reversibly acclimate to temperature shifts. However, the warming-acclimated lines showed evidence of adaptation to elevated temperatures in the transcriptome data. Here the core gene expression was not reversed when warming-acclimated lines were moved back to the low temperature environment, which suggested that P. multiseries cells might adapt to rising temperature over longer timescales. The distinct strategies of phenotypic plasticity to rising temperature and pCO2 demonstrate a strong acclimation capacity for this bloom-forming toxic diatom in the future ocean.

Continue reading ‘Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification’

Physiological and gene expression responses of the mussel Mytilus galloprovincialis to low pH and low dissolved oxygen

Published 10 February 2023 Science Closed
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Graphical abstract.

Highlight

  • Low pH and DO, alone or in combination, affected physiology and gene expression in mussels.
  • Low pH alone led to a decrease of all tested physiological parameters.
  • Low DO decreased the clearance rate, modulated haemocytes parameters, increased carbohydrates levels.
  • The combined effect of low pH and low DO could not be predicted by a simple arithmetic additive response.

Abstract

The prevalence and frequency of hypoxia events have increased worldwide over the past decade as a consequence of global climate change and coastal biological oxygen depletions. On the other hand, anthropogenic emissions of CO2 and consequent accumulation in the sea surface result in a perturbation of the seawater carbonate system, including a decrease in pH, known as ocean acidification. While the effect of decreases in pH and dissolved oxygen (DO) concentration is better understood, their combined effects are still poorly resolved. Here, we exposed adult mussels (Mytilus galloprovincialis) to two pHs (8.27 and 7.63) and DO concentrations (7.65 and 2.75 mg L−1) over 17 days in a full-factorial design. These levels correspond to extremes of the present natural variability and are relevant in the context of ocean acidification and hypoxia. No mortality was observed during the experiment. However, sublethal effects were observed for clearance and oxygen consumption rates, as well as total haemocytes count and haemocytes viability and gene expression in mussels exposed to the combination of low pH and low DO. Respiration and excretion rates were not significantly impacted by low pH and DO, alone or in combination. Overall, low pH alone led to a decrease in all tested physiological parameters while low DO alone led to a decline in clearance rate, haemocyte parameters and an increase in carbohydrate content. Both parameters led to up- or down-regulation of most of the selected genes. Not surprisingly, the combined effect of low pH and low DO could not be predicted by a simple arithmetic additive response at the effect level, highlighting more complex and non-linear effects.

Continue reading ‘Physiological and gene expression responses of the mussel Mytilus galloprovincialis to low pH and low dissolved oxygen’

Restoration and coral adaptation delay, but do not prevent, climate-driven reef framework erosion of an inshore site in the Florida Keys

Published 9 February 2023 Science Closed
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For reef framework to persist, calcium carbonate production by corals and other calcifiers needs to outpace loss due to physical, chemical, and biological erosion. This balance is both delicate and dynamic and is currently threatened by the effects of ocean warming and acidification. Although the protection and recovery of ecosystem functions are at the center of most restoration and conservation programs, decision makers are limited by the lack of predictive tools to forecast habitat persistence under different emission scenarios. To address this, we developed a modelling approach, based on carbonate budgets, that ties species-specific responses to site-specific global change using the latest generation of climate models projections (CMIP6). We applied this model to Cheeca Rocks, an outlier in the Florida Keys in terms of high coral cover, and explored the outcomes of restoration targets scheduled in the coming 20 years at this site by the Mission: Iconic Reefs restoration initiative. Additionally, we examined the potential effects of coral thermal adaptation by increasing the bleaching threshold by 0.25, 0.5, 1 and 2˚C. Regardless of coral adaptative capacity or restoration, net carbonate production at Cheeca Rocks declines heavily once the threshold for the onset of annual severe bleaching is reached. The switch from net accretion to net erosion, however, is significantly delayed by mitigation and adaptation. The maintenance of framework accretion until 2100 and beyond is possible under a decreased emission scenario coupled with thermal adaptation above 0.5˚C. Although restoration initiatives increase reef accretion estimates, Cheeca Rocks will only be able to keep pace with future sea-level rise in a world where anthropogenic CO2 emissions are reduced. Present results, however, attest to the potential of restoration interventions combined with increases in coral thermal tolerance to delay the onset of mass bleaching mortalities, possibly in time for a low-carbon economy to be implemented and complementary mitigation measures to become effective.

Continue reading ‘Restoration and coral adaptation delay, but do not prevent, climate-driven reef framework erosion of an inshore site in the Florida Keys’

Long-term slowdown of ocean carbon uptake by alkalinity dynamics

Published 9 February 2023 Science Closed
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Abstract

Oceanic absorption of atmospheric carbon dioxide (CO2) is expected to slow down under increasing anthropogenic emissions; however, the driving mechanisms and rates of change remain uncertain, limiting our ability to project long-term changes in climate. Using an Earth system simulation, we show that the uptake of anthropogenic carbon will slow in the next three centuries via reductions in surface alkalinity. Warming and associated changes in precipitation and evaporation intensify density stratification of the upper ocean, inhibiting the transport of alkaline water from the deep. The effect of these changes is amplified three-fold by reduced carbonate buffering, making alkalinity a dominant control on CO2 uptake on multi-century timescales. Our simulation reveals a previously unknown alkalinity-climate feedback loop, amplifying multi-century warming under high emission trajectories.

Key Points

  • Oceanic uptake of carbon could slow in upcoming centuries through previously unidentified alkalinity-climate feedback
  • Reduced upwelling and carbonate buffer enhance the influence of alkalinity on the increase in surface ocean carbon dioxide
  • Reductions in surface alkalinity will reduce the rate of carbon uptake on multi-century timescales
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Impacts of rising temperatures and water acidification on the oxidative status and immune system of aquatic ectothermic vertebrates: a meta-analysis

Published 8 February 2023 Science Closed
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Highlights

  • CO2 emissions are driving increase in temperature and water acidification.
  • Meta-analysis implemented to assess impacts of CO2-stressors on ectotherms physiology.
  • High temperature and water acidification induce higher oxidative damage in ectotherms.
  • Early life stages are more capable than adults to upregulate antioxidant enzymes.
  • Oxidative status regulation underlies thermal acclimation.

Abstract

Species persistence in the Anthropocene is dramatically threatened by global climate change. Large emissions of carbon dioxide (CO2) from human activities are driving increases in mean temperature, intensity of heatwaves, and acidification of oceans and freshwater bodies. Ectotherms are particularly sensitive to CO2-induced stressors, because the rate of their metabolic reactions, as well as their immunological performance, are affected by environmental temperatures and water pH. We reviewed and performed a meta-analysis of 56 studies, involving 1259 effect sizes, that compared oxidative status or immune function metrics between 42 species of ectothermic vertebrates exposed to long-term increased temperatures or water acidification (≥48 h), and those exposed to control parameters resembling natural conditions. We found that CO2-induced stressors enhance levels of molecular oxidative damages in ectotherms, while the activity of antioxidant enzymes was upregulated only at higher temperatures, possibly due to an increased rate of biochemical reactions dependent on the higher ambient temperature. Differently, both temperature and water acidification showed weak impacts on immune function, indicating different direction (increase or decrease) of responses among immune traits. Further, we found that the intensity of temperature treatments (Δ°C) and their duration, enhance the physiological response of ectotherms, pointing to stronger effects of prolonged extreme warming events (i.e., heatwaves) on the oxidative status. Finally, adult individuals showed weaker antioxidant enzymatic responses to an increase in water temperature compared to early life stages, suggesting lower acclimation capacity. Antarctic species showed weaker antioxidant response compared to temperate and tropical species, but level of uncertainty in the antioxidant enzymatic response of Antarctic species was high, thus pairwise comparisons were statistically non-significant. Overall, the results of this meta-analysis indicate that the regulation of oxidative status might be one key mechanism underlying thermal plasticity in aquatic ectothermic vertebrates.

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Multi-stress interplay: time and duration of ocean acidification modulate the toxicity of mercury and other metals

Published 8 February 2023 Science Closed
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The current understanding of multi-stress interplay assumes stresses occur in perfect synchrony, but this assumption is rarely met in the natural marine ecosystem. To understand the interplay between non-perfectly overlapped stresses in the ocean, we manipulated different temporal scenarios of acidification and assessed their effect on mercury toxicity in a marine copepod. We found that the scenario of past acidification aggravated mercury toxicity, but personal and persistent acidification mitigated the toxicity. This is because personal and persistent acidification initiated the energy compensation to enhance growth and mercury efflux. To explore how general temporal scenarios of acidification affected multi-stress interplay, we conducted a meta-analysis on marine animals and found that scenarios significantly changed the toxicity of several other metals. Our study thus demonstrates that time and duration of stresses modulate multi-stress interplay in the marine ecosystem, and suggests that future studies should move beyond the scenario of perfect synchrony.

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Common sea star (Asterias rubens) coelomic fluid changes in response to short-term exposure to environmental stressors

Published 8 February 2023 Science Closed
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Common sea stars (Asterias rubens) are at risk of physiological stress and decline with projected shifts in oceanic conditions. This study assessed changes in coelomic fluid (CF) blood gases, electrolytes, osmolality, and coelomocyte counts in adult common sea stars after exposure to stressors mimicking effects from climate change for 14 days, including decreased pH (−0.4 units, mean: 7.37), hypoxia (target dissolved oxygen ~1.75 mg O2/L, mean: 1.80 mg O2/L), or increased temperature (+10 °C, mean: 17.2 °C) and compared sea star CF electrolytes and osmolality to tank water. Changes in CF blood gases, electrolytes, and/or coelomocyte counts occurred in all treatment groups after stressor exposures, indicating adverse systemic effects with evidence of increased energy expenditure, respiratory or metabolic derangements, and immunosuppression or inflammation. At baseline, CF potassium and osmolality of all groups combined were significantly higher than tank water, and, after exposures, CF potassium was significantly higher in the hypoxia group as compared to tank water. These findings indicate physiological challenges for A. rubens after stressor exposures and, given increased observations of sea star wasting events globally, this provides evidence that sea stars as a broad group are particularly vulnerable to changing oceans.

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Fresh and saline submarine groundwater discharge as sources of carbon and nutrients to the Japan Sea

Published 7 February 2023 Science Closed
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Highlights

  • Fresh groundwater was comparable to the discharge from rivers and the main source of carbon, phosphate, and nitrate to coastal waters.
  • Groundwater-derived alkalinity fluxes were 7 times greater than river inputs, buffering the coastal ocean.
  • Nutrient and chlorophyll observations revealed the strong influence of groundwater discharge on primary productivity.

Abstract

Submarine groundwater discharge (SGD) is an important pathway for carbon and nutrients to the coastal ocean, sometimes exceeding river inputs. SGD fluxes can have implications for long-term carbon storage, ocean acidification and nutrient dynamics. Here, we used radium (223Ra and 226Ra) isotopes to quantify SGD-derived fluxes of dissolved inorganic (DIC) and organic (DOC) carbon, nitrate (NO3−), nitrite (NO2−), ammonium (NH4+) and phosphate (PO43−) in a spring-fed coastal bay in the Japan Sea. The average coastal water residence times using 223Ra/226Ra ratios was 32.5 ± 17.9 days. Fresh and saline SGD were estimated using a radium mixing model with short- and long-lived isotopes. The volume of fresh SGD entering the bay (4.6 ± 4.6 cm day−1) was more than twice that of the volume of saline SGD (1.9 ± 2.1 cm day−1). Fresh SGD (mmol m2 day−1) was the main source of DOC (2.7 ± 2.6), DIC (13.9 ± 13.7), PO43− (0.3 ± 0.3) and NO3− (6.6 ± 6.5) to the coastal ocean, whereas saline SGD was the main source of NH4+ (0.2 ± 0.2). Total SGD-derived carbon and nutrient fluxes were 4 – 7 and 2–16 times greater than local river inputs. Positive correlations between chlorophyll-a, 226Ra and δ13C-DIC indicate that SGD significantly (p < 0.05) enhances primary productivity nearshore. Overall, fresh SGD of nitrogen and carbon to seawater drove chlorophyll-a, decreased DIC/Alkalinity ratios, and modified the carbonate biogeochemistry of the coastal ocean.

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Potential effects of climate change on the growth response of the toxic dinoflagellate Karenia selliformis from Patagonian waters of Chile

Published 6 February 2023 Science Closed
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Northern Patagonia (41–44°S) is affected by climatic, hydrological and oceanographic anomalies, which in synergy with processes such as global warming and acidification of the coastal oceans may affect the frequency and intensity of harmful algal blooms (HABs). Greater frequency of HABs has been reported in the southeastern Pacific Ocean, including blooms of the toxic dinoflagellate Karenia selliformis, causing massive mortality of marine fauna in the oceanic and coastal areas of Patagonia. The objective of this study was to determine the effects of temperature and pH interaction on the growth of K. selliformis (strain CREAN_KS02), since these factors have wide seasonal fluctuations in the Patagonian fjord ecosystem. The CREAN_KS02 strain isolated from the Aysén Region (43°S) was used in a factorial experiment with five pH levels (7.0, 7.4, 7.7, 8.1 and 9.0) and two temperatures (12 and 17 °C) during a period of 18–21 days. Results indicated a significant effect of temperature and pH interaction on growth rate (range 0.22 ± 0.00 to 0.08 ± 0.01 d−1) and maximum density (range 13,710 ± 2,616 to 2,385 ± 809 cells mL−1) of K. selliformis. The highest density and growth of K. selliformis was found at 12 °C with a reduced pH (7.0–7.7). The results suggest that the current environmental conditions of coastal Patagonia, waters of low temperature and relatively low pH, may be favorable for the development of blooms of this species during autumn. We suggest that there is natural plasticity of K. selliformis in a wide pH range (7.0–8.1) but in a narrow low temperature range (10.6–12.9 °C), values that are typically recorded in the oceanic region of northern Patagonia. In contrast, in an extreme climate change scenario (ocean warming and coastal acidification) in northern Patagonia, a negative effect on the growth of K. selliformis may be expected due to amplification of the acidification effects caused by the thermal stress of high temperature water.

Continue reading ‘Potential effects of climate change on the growth response of the toxic dinoflagellate Karenia selliformis from Patagonian waters of Chile’

Effects of global environmental change on microalgal photosynthesis, growth and their distribution

Published 6 February 2023 Science Closed
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Global climate change (GCC) constitutes a complex challenge posing a serious threat to biodiversity and ecosystems in the next decades. There are several recent studies dealing with the potential effect of increased temperature, decrease of pH or shifts in salinity, as well as cascading events of GCC and their impact on human-environment systems. Microalgae as primary producers are a sensitive compartment of the marine ecosystems to all those changes. However, the potential consequences of these changes for marine microalgae have received relatively little attention and they are still not well understood. Thus, there is an urgent need to explore and understand the effects generated by multiple climatic changes on marine microalgae growth and biodiversity. Therefore, this review aimed to compare and contrast mechanisms that marine microalgae exhibit to directly respond to harsh conditions associated with GCC and the potential consequences of those changes in marine microalgal populations. Literature shows that microalgae responses to environmental stressors such as temperature were affected differently. A stress caused by salinity might slow down cell division, reduces size, ceases motility, and triggers palmelloid formation in microalgae community, but some of these changes are strongly species-specific. UV irradiance can potentially lead to an oxidative stress in microalgae, promoting the production of reactive oxygen species (ROS) or induce direct physical damage on microalgae, then inhibiting the growth of microalgae. Moreover, pH could impact many groups of microalgae being more tolerant of certain pH shifts, while others were sensitive to changes of just small units (such as coccolithophorids) and subsequently affect the species at a higher trophic level, but also total vertical carbon transport in oceans. Overall, this review highlights the importance of examining effects of multiple stressors, considering multiple responses to understand the complexity behind stressor interactions.

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Combined effects of climate change stressors and predators with contrasting feeding-digestion strategies on a mussel species

Published 1 February 2023 Science Closed
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Graphical abstract

Highlights

  • Combined effects of climate change stressors and Predator Cues (PC) were evaluated.
  • Ocean Acidification (OA), Warming (OW) and PC affected mussel traits.
  • At the control temperature (15 °C), mussel byssal biogenesis increased with PC.
  • PC affected mussel size, wet mass and calcification rate.
  • The effects of starfish PC on some mussel traits were larger than those of snail PC.

Abstract

We investigated the combined effects of Ocean Warming (OW), Acidification (OA) and predator cues (Non-Consumptive Effects; NCEs) of two predators with contrasting feeding-digestion strategies on the mussel Perumytilus purpuratus. We considered starfish-NCEs (partially external digestion) and snail-NCEs (internal digestion). Mussels were exposed for 13 weeks to cross-factored OA (~500 and ~1400 μatm, pCO2) and OW (~15 and ~20 °C) conditions, in the presence/absence of NCEs from one or both predators. Mussels exposed to both NCEs exhibited smaller length and buoyant weight growth than those under control or snail-NCEs conditions. Mussels exposed to starfish-NCEs exhibited smaller wet mass than control mussels. OW and starfish-NCEs in isolation or combined with snail-NCEs increased mussel oxygen consumption. Byssal biogenesis was affected by the three-factors interaction. Clearance rates were affected by the OW × OA interaction. We suggest that mainly starfish-NCEs, in isolation or interacting with OA or/and OW, can threat mussel traits and the associated community.

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Elevated CO2 reduces copper accumulation and toxicity in the diatom Thalassiosira pseudonana

Published 31 January 2023 Science Closed
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The projected ocean acidification (OA) associated with increasing atmospheric CO2 alters seawater chemistry and hence the bio-toxicity of metal ions. However, it is still unclear how OA might affect the long-term resilience of globally important marine microalgae to anthropogenic metal stress. To explore the effect of increasing pCO2 on copper metabolism in the diatom Thalassiosira pseudonana (CCMP 1335), we employed an integrated eco-physiological, analytical chemistry, and transcriptomic approach to clarify the effect of increasing pCO2 on copper metabolism of Thalassiosira pseudonana across different temporal (short-term vs. long-term) and spatial (indoor laboratory experiments vs. outdoor mesocosms experiments) scales. We found that increasing pCO2 (1,000 and 2,000 μatm) promoted growth and photosynthesis, but decreased copper accumulation and alleviated its bio-toxicity to T. pseudonana. Transcriptomics results indicated that T. pseudonana altered the copper detoxification strategy under OA by decreasing copper uptake and enhancing copper-thiol complexation and copper efflux. Biochemical analysis further showed that the activities of the antioxidant enzymes glutathione peroxidase (GPX), catalase (CAT), and phytochelatin synthetase (PCS) were enhanced to mitigate oxidative damage of copper stress under elevated CO2. Our results provide a basis for a better understanding of the bioremediation capacity of marine primary producers, which may have profound effect on the security of seafood quality and marine ecosystem sustainability under further climate change.

Continue reading ‘Elevated CO2 reduces copper accumulation and toxicity in the diatom Thalassiosira pseudonana’

No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies

Published 27 January 2023 Science Closed
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In a future ocean, dissolved organic carbon (DOC) release by seaweed has been considered a pathway for organic carbon that is not incorporated into growth under carbon dioxide (CO2) enrichment/ocean acidification (OA). To understand the influence of OA on seaweed DOC release, a 21-day experiment compared the physiological responses of three seaweed species, two which operate CO2 concentrating mechanisms (CCMs), Ecklonia radiata (C. Agardh) J. Agardh and Lenormandia marginata (Hooker F. and Harvey) and one that only uses CO2 (non-CCM), Plocamium cirrhosum (Turner) M.J. Wynne. These two groups (CCM and non-CCM) are predicted to respond differently to OA dependent on their affinities for Ci (defined as CO2 + bicarbonate, HCO3−). Future ocean CO2 treatment did not drive changes to seaweed physiology—growth, Ci uptake, DOC production, photosynthesis, respiration, pigments, % tissue carbon, nitrogen, and C:N ratios—for any species, regardless of Ci uptake method. Our results further showed that Ci uptake method did not influence DOC release rates under OA. Our results show no benefit of elevated CO2 concentrations on the physiologies of the three species under OA and suggest that in a future ocean, photosynthetic CO2 fixation rates of these seaweeds will not increase with Ci concentration.

Continue reading ‘No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies’
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