Kelps are pivotal to temperate coastal ecosystems, providing essential habitat and nutrients for diverse marine life, and significantly enhancing local biodiversity. The impacts of elevated CO2 levels on kelps may induce far-reaching effects throughout the marine food web, with potential consequences for biodiversity and ecosystem functions. This study considers the kelp Macrocystis pyrifera and its symbiotic microorganisms as a holistic functional unit (holobiont) to examine their collective response to heightened CO2 levels. Over a 4 month cultivation from the fertilization of M. pyrifera gametes to the development of juvenile sporophytes, our findings reveal that elevated CO2 levels influence the structure of the M. pyrifera symbiotic microbiome, alter metabolic profiles, and reshape microbe-metabolite interactions using 16S rRNA amplicon sequencing and liquid chromatography coupled to mass spectrometry analysis. Notably, Dinoroseobacter, Sulfitobacter, Methylotenera, Hyphomonas, Milano-WF1B-44 and Methylophaga were selected as microbiome biomarkers, which showed significant increases in comparative abundance with elevated CO2 levels. Stress-response molecules including fatty-acid metabolites, oxylipins, and hormone-like compounds such as methyl jasmonate and prostaglandin F2a emerged as critical metabolomic indicators. We propose that elevated CO2 puts certain stress on the M. pyrifera holobiont, prompting the release of these stress-response molecules. Moreover, these molecules may aid the kelp’s adaptation by modulating the microbial community structure, particularly influencing potential pathogenic bacteria, to cope with environmental change. These results will enrich the baseline data related to the chemical interactions between the microbiota and M. pyrifera and provide clues for predicting the resilience of kelps to future climate change.
Continue reading ‘Chemical interactions between kelp Macrocystis pyrifera and symbiotic bacteria under elevated CO2 condition’Posts Tagged 'algae'
Chemical interactions between kelp Macrocystis pyrifera and symbiotic bacteria under elevated CO2 condition
Published 26 November 2024 Science ClosedTags: algae, biological response, community composition, molecular biology, otherprocess, physiology, prokaryotes, protists, reproduction
The role of rolling corals and free-living calcifying coralline algae in the management of greenhouse gas CO2 in the Colombian Caribbean
Published 25 November 2024 Science ClosedTags: algae, biological response, BRcommunity, calcification, corals, dissolution, field, laboratory, mitigation, North Atlantic, photosynthesis, primary production, respiration
The ongoing increase in anthropogenic CO₂ emissions since the industrial revolution has accelerated ocean acidification (OA) by introducing CO₂ into seawater, forming carbonic acid and reducing pH levels. This acidification threatens marine calcifiers by weakening their capacity to build calcium carbonate structures and promoting the dissolution of existing skeletons. Nonetheless, calcifying organisms may contribute to mitigating OA effects. This study explores the roles of corals (rolling Siderastrea radians, a seagrass dweller) and free-living calcifying coralline algae (back reef) in CO₂ mitigation in seawater. Field experiments were conducted on Isla Grande (Corales del Rosario and San Bernardo National Natural Park, Colombian Caribbean), to observe the diel variations in photosynthesis and calcification of these uncommon reef builders across different times of the day. Results demonstrate diel shifts influenced by photosynthesis/respiration and calcification/dissolution, with free-living coralline algae exhibiting higher productivity and calcification rates than corals during the day. Notably, free-living coralline algae displayed pronounced hysteresis, reflecting high sensitivity to light. These findings underscore the significant role of free-living coralline algae in marine carbon cycling, suggesting a more substantial impact on CO₂ mitigation than previously recognized. Conserving free-living coralline algae and their habitats is thus critical for supporting marine ecosystem health and resilience amidst global change, warranting further research into their metabolic responses to inform conservation strategies.
Continue reading ‘The role of rolling corals and free-living calcifying coralline algae in the management of greenhouse gas CO2 in the Colombian Caribbean’Challenges and opportunities towards meeting the United Nations’ Sustainable Development Goals from coral and seaweed ecosystems in an era of climate change
Published 22 November 2024 Science ClosedTags: algae, biological response, corals, mitigation, policy, review, socio-economy
Global climate change scenarios due to anthropogenic responses jeopardize ecosystem sustainability and hinder progress toward achieving the United nations (UN-SDGs). Achieving “natural carbon solutions” from terrestrial ecosystems is challenging due to decreasing arable land and increasing marginal land. Marine ecosystems representing a wider “natural carbon solutions” have also been severely impacted by climate change. Among marine ecosystems, coral reefs and seaweed communities are the key ecosystem engineers that support a wide range of marine life, facilitate nutrient cycling, and provide essential ecosystem services with a pivotal role in sustaining coastal economies and livelihoods. Notably, these communities compete for space within the reef ecosystem and suffer from loss of diversity and richness due to climate change. Therefore, assessing the climate change resilience of both the corals and seaweeds is essential to evaluate and design long-term adaptation strategies, ecological innovations, and science-informed policies to conserve, restore, and sustainably manage economic services. This review article aims to highlight (1) the physiological response and resilience of corals and seaweeds to environmental changes, (2) the impact of climate change on their ecosystems and economic services, (3) their potential contributions towards the United Nations’ sustainable goals, (4) progressive efforts applied for their restoration, and (5) the potential complementary value of large-scale seaweed aquaculture as a carbon sink.
Continue reading ‘Challenges and opportunities towards meeting the United Nations’ Sustainable Development Goals from coral and seaweed ecosystems in an era of climate change’Competitive dissolution of mixed carbonate solids under simulated ocean acidification
Published 12 November 2024 Science ClosedTags: algae, biogeochemistry, biological response, BRcommunity, laboratory, sediment
It is estimated that at least 25 % of the anthropogenic carbon dioxide (CO2) emitted to the atmosphere since the start of the industrial revolution has been absorbed and dissolved by the oceans. The uptake of CO2 by the oceans leads to an increase in the seawater proton concentration ([H+]), and decreases in seawater pH, carbonate ion concentration ([CO32–]), and saturation state (Ω) with respect to calcium carbonate (CaCO3) minerals; a process commonly referred to as “ocean acidification”. Shallow-water (<200 m), high-magnesium, biogenic calcites are expected to be amongst the first to respond to ocean acidification, and it has been proposed that they will dissolve selectively and sequentially according to their solubility in seawater. In this study, we test this competitive dissolution hypothesis by reacting a mixture of biogenic and synthetic carbonates of varying Mg content with acidified, natural seawater to simulate the progressive acidification of surface-ocean waters by anthropogenic CO2. The results of this study confirm the hypothesis that carbonates will dissolve sequentially according to their respective solubility. They also reveal that the dissolution of high Mg-calcites will proceed incongruently. The originality of this contribution rests with the demonstration that the presence of a single high Mg-calcite will generate, like in a sediment of mixed mineralogy, a continuum of transient states as lower Mg-calcites of greater stability are precipitated and dissolved. Consequently, in a semi-closed or closed system, the pH buffering of the acidified seawater solution will be progressive rather than occur in steps according to changes in the solubility of the individual carbonate phases that compose a sediment. Hence, we expect that, as the oceans take up more anthropogenic CO2 and further acidify, the average mineralogy and composition (Mg content) of shallow-water carbonate sediments and reef structures will change over the next few centuries as the most soluble carbonate phases (high-Mg calcites) are dissolved and no longer precipitated.
Continue reading ‘Competitive dissolution of mixed carbonate solids under simulated ocean acidification’Sustainable seaweed aquaculture and climate change in the North Atlantic: challenges and opportunities
Published 4 November 2024 Science ClosedTags: algae, modeling, North Atlantic, socio-economy
Seaweed aquaculture is gaining traction globally as a solution to many climate issues. However, seaweeds themselves are also under threat of anthropogenically driven climate change. Here, we summarize climate-related challenges to the seaweed aquaculture industry, with a focus on the developing trade in the North Atlantic. Specifically, we summarize three main challenges: i) abiotic change; ii) extreme events; and iii) disease & herbivory. Abiotic change includes negative effects of ocean warming and acidification, as well as altered seasonality due to ocean warming. This can lower biomass yield and change biochemical composition of the seaweeds. Extreme events can cause considerable damage and loss to seaweed farms, particularly due to marine heatwaves, storms and freshwater inputs. Seaweed diseases have a higher chance of proliferating under environmentally stressful conditions such as ocean warming and decreased salinity. Herbivory causes loss of biomass but is not well researched in relation to seaweed aquaculture in the North Atlantic. Despite challenges, opportunities exist to improve resilience to climate change, summarized in three sections: i) future proof site selection; ii) advances in breeding and microbiome manipulation; and iii) restorative aquaculture. We present a case study where we use predictive modelling to illustrate suitable habitat for seaweed cultivation in the North Atlantic under future ocean warming. Notably, there was a large loss of suitable habitat for cultivating Alaria esculenta and Laminaria digitata. We show how selection and priming and microbe inoculates may be a cost-effective and scalable solution to improve disease- and thermal tolerance. Co-cultivation of seaweeds may increase both yield and biodiversity co-benefits. Finally, we show that aquaculture and restoration can benefit from collaborating on nursery techniques and push for improved legislation.
Continue reading ‘Sustainable seaweed aquaculture and climate change in the North Atlantic: challenges and opportunities’The dilemma of Luhuitou fringing reefs: net dissolution in winter and enhanced acidification in summer
Published 24 October 2024 Science ClosedTags: algae, calcification, chemistry, corals, North Pacific
Global coral reef ecosystems have been severely degraded due to the combined effects of climate change and human activities. Changes in the seawater carbonate system of coral reef ecosystems can reflect their status and their responses to the impacts of climate change and human activities. Winter and summer surveys in 2019 found that the ecological community of the Luhuitou coral reef flat was dominated by macroalgae and corals, respectively, contrasting with the conditions 10 years ago. The Luhuitou fringing reefs were sources of atmospheric CO2 in both seasons. In winter, the daily variation range of dissolved inorganic carbon (DIC) in Luhuitou coral reefs was up to 450 µmol/kg, while that of total alkalinity (TA) was only 68 µmol/kg. This indicated that the organic production was significantly higher than the calcification process during this period. The TA/DIC was approximately 0.15, which was less than half of that in healthy coral reefs; hence, photosynthesis-respiration processes were the most important factors controlling daily changes in the seawater carbonate system. The net community production (NCP) of the Luhuitou coral reef ecosystem in winter was as high as 47.65 mmol C/(m2·h). While the net community calcification (NCC) was approximately 3.35 and −4.15 mmol CaCO3/(m2·h) during the daytime and nighttime respectively. Therefore, the NCC for the entire day was −21.9 mmol CaCO3/(m2·d), indicating a net autotrophic dissolved state. In summer, the acidification was enhanced by thunderstorms and heavy rain with the highest seawater partial pressure of CO2 (pCO2) and lowest pHT. Over the past 10 years, the increase rate of seawater pCO2 in Luhuitou reef was approximately 13.3 µatm/a***, six times that of the open ocean, while the decrease rate of pH was approximately 0.008 3/a, being five times that of the global ocean. These findings underscore the importance of protecting and restoring Luhuitou fringing reef, as well as similar reefs worldwide.
Continue reading ‘The dilemma of Luhuitou fringing reefs: net dissolution in winter and enhanced acidification in summer’Regulation of seawater dissolved carbon pools by environmental changes in Ulva prolifera originating sites: a new perspective on the contribution of U. prolifera to the seawater carbon sink function
Published 21 October 2024 Science ClosedTags: algae, biological response, laboratory, light, multiple factors, North Pacific, nutrients, temperature
Highlights
- Moderate light, temperature and nitrate addition boost U. prolifera DIC absorption.
- U. prolifera adapts carbon fixation modes to environmental changes.
- Origin environmental conditions determine U. prolifera’s carbon sink contribution.
Abstract
The Ulva prolifera bloom is considered one of the most serious ecological disasters in the Yellow Sea in the past decade, forming a carbon sink in its source area within a short period but becoming a carbon source at its destination. To explore the effects of different environmental changes on seawater dissolved carbon pools faced by living U. prolifera in its originating area, U. prolifera were cultured in three sets with different light intensity (54, 108, and 162 μmol m−2 s−1), temperature (12, 20, and 28 °C) and nitrate concentration gradients (25, 50, and 100 μmol L−1). The results showed that moderate light (108 μmol m−2 s−1), temperature (20 °C), and continuous addition of exogenous nitrate significantly enhanced the absorption of dissolved inorganic carbon (DIC) in seawater by U. prolifera and most promoted its growth. Under the most suitable environment, the changes in the seawater carbonate system were mainly dominated by biological production and denitrification, with less influence from aerobic respiration. Facing different environmental changes, U. prolifera continuously changed its carbon fixation mode according to tissue δ13C results, with the changes in the concentrations of various components of DIC in seawater, especially the fluctuation of HCO3− and CO2 concentrations. Enhanced light intensity of 108 μmol m−2 s−1 could shift the carbon fixation pathway of U. prolifera towards the C4 pathway compared to temperature and nitrate stimulation. Environmental conditions at the origin determined the amount of dissolved carbon fixed by U. prolifera. Therefore, more attention should be paid to the changes in marine environmental conditions at the origin of U. prolifera, providing a basis for scientific management of U. prolifera.
Continue reading ‘Regulation of seawater dissolved carbon pools by environmental changes in Ulva prolifera originating sites: a new perspective on the contribution of U. prolifera to the seawater carbon sink function’Assessing the potential of macroalgae-based carbon sequestration in Indonesia
Published 11 October 2024 Science ClosedTags: algae, biological response, Indian, laboratory, mitigation
Macroalgae are being intensively explored as a nature-based solution to address climate change. Although there are still some uncertainties about recognizing macroalgae in climate mitigation, the research trend on macroalgae carbon potential continues to increase. We collected secondary data, literature reviews, and expert opinions through focus group discussions to estimate the carbon sequestration potential of macroalgae and examine its feasibility in Indonesian climate mitigation. Our analysis shows that the carbon sequestration potential of macroalgae in Indonesia is significant, estimated to range from 351.246-2.526.332 Mg C yr−1, placing macroalgae as the third largest marine carbon store after mangroves and seagrass. In addition, macroalgae have higher CO2 sequestration rates than other blue carbon habitats. Our assessment of the viability of macroalgae in the blue carbon shows that macroalgae meet the critical elements of blue carbon criteria, including carbon sequestration scale, long-term storage, anthropogenic impact, and social or environmental interventions. However, aligning it with other climate mitigation policies is essential for macroalgae to be fully recognized in blue carbon. This preliminary study suggests that macroalgae could be necessary for Indonesia’s climate mitigation action.
Continue reading ‘Assessing the potential of macroalgae-based carbon sequestration in Indonesia’Assessing the role of natural kelp forests in modifying seawater chemistry
Published 8 October 2024 Science ClosedTags: algae, biological response, chemistry, review
Climate change is causing widespread impacts on seawater pH through ocean acidification (OA). Kelp forests, in some locations can buffer the effects of OA through photosynthesis. However, the factors influencing this variation remain poorly understood. To address this gap, we conducted a literature review and field deployments of pH and dissolved oxygen (DO) loggers within four habitats: intact kelp forest, moderate kelp cover, sparse kelp cover and barrens at one site in Port Phillip Bay, a wind-wave dominated coastal embayment in Victoria, Australia. Additionally, a wave logger was placed directly in front of the intact kelp forest and barrens habitats. Most studies reported that kelp increased seawater pH and DO during the day, compared to controls without kelp. This effect was more pronounced in densely populated forests, particularly in shallow, sheltered conditions. Our field study was broadly consistent with these observations, with intact kelp habitat having higher seawater pH than habitats with less kelp or barrens and higher seawater DO compared to barrens, particularly in the afternoon and during calmer wave conditions. Although kelp forests can provide local refuges to biota from OA, the benefits are variable through time and may be reduced by declines in kelp density and increased wave exposure.
Continue reading ‘Assessing the role of natural kelp forests in modifying seawater chemistry’“Pink power”—the importance of coralline algal beds in the oceanic carbon cycle
Published 7 October 2024 Science ClosedTags: algae, biological response, calcification, primary production, South Atlantic
Current evidence suggests that macroalgal-dominated habitats are important contributors to the oceanic carbon cycle, though the role of those formed by calcifiers remains controversial. Globally distributed coralline algal beds, built by pink coloured rhodoliths and maerl, cover extensive coastal shelf areas of the planet, but scarce information on their productivity, net carbon flux dynamics and carbonate deposits hampers assessing their contribution to the overall oceanic carbon cycle. Here, our data, covering large bathymetrical (2–51 m) and geographical ranges (53°N–27°S), show that coralline algal beds are highly productive habitats that can express substantial carbon uptake rates (28–1347 g C m−2 day−1), which vary in function of light availability and species composition and exceed reported estimates for other major macroalgal habitats. This high productivity, together with their substantial carbonate deposits (0.4–38 kilotons), renders coralline algal beds as highly relevant contributors to the present and future oceanic carbon cycle.
Continue reading ‘“Pink power”—the importance of coralline algal beds in the oceanic carbon cycle’Shifting seagrass-oyster interactions alter species response to ocean warming and acidification
Published 30 September 2024 Science ClosedTags: algae, biological response, BRcommunity, mesocosms, mollusks, morphology, physiology
- 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.
- 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.
- 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.
- 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.
Genome of Halimeda opuntia reveals differentiation of subgenomes and molecular bases of multinucleation and calcification in algae
Published 27 September 2024 Science ClosedTags: algae, biological response, calcification, laboratory, molecular biology
Significance
Coral reef ecosystems are undergoing significant degradation and reorganization due to ocean warming and acidification. Calcareous algae, crucial primary producers and reef-builders, exhibit diverse morphologies, lifestyles, and adaptative strategies. A significant gap exists, however, in deciphering the genetic basis of algae positioned at an evolutionary crossroad from unicellular to multicellular, from intracellular calcifying to extracellular calcification, and from acidification-sensitive to acidification-tolerant. Genome analysis of the green alga Halimeda opuntia and other algae shed light on unique genetic features associated with multinucleation, cell fragment regeneration, extracellular calcification, and tolerance of CO2 increases in seawater. Our findings advance the understanding of how calcareous algae respond to environmental changes and have implications in regenerative biology, plant grafting, and coral reef conservation and restoration.
Abstract
Algae mostly occur either as unicellular (microalgae) or multicellular (macroalgae) species, both being uninucleate. There are important exceptions, however, as some unicellular algae are multinucleate and macroscopic, some of which inhabit tropical seas and contribute to biocalcification and coral reef robustness. The evolutionary mechanisms and ecological significance of multinucleation and associated traits (e.g., rapid wound healing) are poorly understood. Here, we report the genome of Halimeda opuntia, a giant multinucleate unicellular chlorophyte characterized by interutricular calcification. We achieve a high-quality genome assembly that shows segregation into four subgenomes, with evidence for polyploidization concomitant with historical sea level and climate changes. We further find myosin VIII missing in H. opuntia and three other unicellular multinucleate chlorophytes, suggesting a potential mechanism that may underpin multinucleation. Genome analysis provides clues about how the unicellular alga could survive fragmentation and regenerate, as well as potential signatures for extracellular calcification and the coupling of calcification with photosynthesis. In addition, proteomic alkalinity shifts were found to potentially confer plasticity of H. opuntia to ocean acidification (OA). Our study provides crucial genetic information necessary for understanding multinucleation, cell regeneration, plasticity to OA, and different modes of calcification in algae and other organisms, which has important implications in reef conservation and bioengineering.
Continue reading ‘Genome of Halimeda opuntia reveals differentiation of subgenomes and molecular bases of multinucleation and calcification in algae’Effects of ocean acidification and temperature coupling on photosynthetic activity and physiological properties of Ulva fasciata and Sargassum horneri
Published 25 September 2024 Science ClosedTags: algae, biological response, BRcommunity, growth, laboratory, multiple factors, North Pacific, photosynthesis, physiology, temperature
Simple Summary
Macroalgae in natural marine areas play an important role in mitigating ocean climate change. The complexity of natural conditions also makes it necessary to study macroalgae not only by considering the effects of changes in a single factor but also by exploring the coupled effects of different environmental conditions on macroalgae. Therefore, in this study, two species of macroalgae were used as experimental subjects to observe their growth processes under different co-treatments of temperature and CO2 concentration. The results of this study can provide a reference for how natural macroalgae can cope with future changes in ocean climate.
Abstract
To investigate the ecological impacts of macroalgae in the framework of shifting global CO2 concentrations, we conducted a study utilizing Ulva fasciata and Sargassum horneri specimens sourced from the Ma’an Archipelago in Zhejiang Province on how ocean acidification (OA) and temperature changes interact to affect the photosynthetic physiological responses of macroalgae. The results of the study showed that OA reduced the tolerance of U. fasciata to bright light at 20 °C, resulting in more pronounced photoinhibition, while 15 °C caused significant inhibition of U. fasciata, reducing its growth and photosynthetic activity, but OA alleviated the inhibition and promoted the growth of the alga to a certain extent. The tolerance of S. horneri to bright light was also reduced at 20 °C; the inhibition was relieved at 15 °C, and the OA further improved the algal growth. The Relative Growth Rate (RGR), photosynthetic pigment content, and the release of the dissolved organic carbon (DOC) of U. fasciata were mainly affected by the change in temperature; the growth of the alga and the synthesis of metabolites were more favored by 20 °C. A similar temperature dependence was observed for S. horneri, with faster growth and high metabolism at 15 °C. Our results suggest that OA reduces the tolerance of macroalgae to high light at suitable growth temperatures; however, at unsuitable growth temperatures, OA effectively mitigates this inhibitory effect and promotes algal growth.
Continue reading ‘Effects of ocean acidification and temperature coupling on photosynthetic activity and physiological properties of Ulva fasciata and Sargassum horneri’Elevated temperature as the dominant stressor on the harmful algal bloom-causing dinoflagellate Prorocentrum obtusidens in a future ocean scenario
Published 23 September 2024 Science ClosedTags: algae, biological response, laboratory, multiple factors, physiology, temperature
Highlights
- Elevated temperature was the dominant stressor impacting Prorocentrum obtusidens.
- Elevated temperature induced rapid cell growth mainly via higher energy production.
- Elevated temperature offset the negative effects from high pCO2 and/or N/P ratio.
- P. obtusidens would probably benefit in a future ocean environment.
- Multi-stressor interactions should be considered in phytoplankton stress response.
Abstract
Marine dinoflagellates are increasingly affected by ongoing global climate changes. While understanding of their physiological and molecular responses to individual stressors anticipated in the future ocean has improved, their responses to multiple concurrent stressors remain poorly understood. Here, we investigated the individual and combined effects of elevated temperature (26 °C relative to 22 °C), increased pCO2 (1000 μatm relative to 400 μatm), and high nitrogen: phosphorus ratio (180:1 relative to 40:1) on a harmful algal bloom-causing dinoflagellate Prorocentrum obtusidens under short-term (28 days) exposure. Elevated temperature was the most dominant stressor affecting P. obtusidens at physiological and transcriptomic levels. It significantly increased cell growth rate and maximum photosynthetic efficiency (Fv/Fm), but reduced chlorophyll a, particulate organic carbon, particulate organic nitrogen, and particulate organic phosphorus. Elevated temperature also interacted with other stressors to produce synergistic positive effects on cell growth and Fv/Fm. Transcriptomic analysis indicated that elevated temperature promoted energy production by enhancing glycolysis, tricarboxylic acid cycle, and nitrogen and carbon assimilation, which supported rapid cell growth but reduced material storage. Increased pCO2 enhanced the expression of genes involved in ionic acid-base regulation and oxidative stress resistance, whereas a high N:P ratio inhibited photosynthesis, compromising cell viability, although the effect was alleviated by elevated temperature. The combined effect of these multiple stressors resulted in increased energy metabolism and up-regulation of material-synthesis pathways compared to the effect caused by elevated temperature alone. Our results underscore ocean warming as the predominant stressor for dinoflagellates and highlight the complex, synergistic effects of multi-stressors on dinoflagellates.
Continue reading ‘Elevated temperature as the dominant stressor on the harmful algal bloom-causing dinoflagellate Prorocentrum obtusidens in a future ocean scenario’Key benthic species are affected by predicted warming in winter but show resistance to ocean acidification
Published 20 September 2024 Science ClosedTags: algae, biological response, BRcommunity, community composition, laboratory, mesocosms, mollusks, mortality, multiple factors, otherprocess, photosynthesis, physiology, temperature
The effects of climate change on coastal biodiversity are a major concern because altered community compositions may change associated rates of ecosystem functioning and services. Whilst responses of single species or taxa have been studied extensively, it remains challenging to estimate responses to climate change across different levels of biological organisation. Studies that consider the effects of moderate realistic near-future levels of ocean warming and acidification are needed to identify and quantify the gradual responses of species to change. Also, studies including different levels of biological complexity may reveal opportunities for amelioration or facilitation under changing environmental conditions. To test experimentally for independent and combined effects of predicted near-future warming and acidification on key benthic species, we manipulated three levels of temperature (winter ambient, +0.8 and +2°C) and two levels of pCO2 (ambient at 450 ppm and elevated at 645 ppm) and quantified their effects on mussels and algae growing separately and together (to also test for inter-specific interactions). Warming increased mussel clearance and mortality rates simultaneously, which meant that total biomass peaked at +0.8°C. Surprisingly, however, no effects of elevated pCO2 were identified on mussels or algae. Moreover, when kept together, mussels and algae had mutually positive effects on each other’s performance (i.e. mussel survival and condition index, mussel and algal biomass and proxies for algal productivity including relative maximum electron transport rate [rETRmax], saturating light intensity [Ik] and maximum quantum yield [Fv/Fm]), independent of warming and acidification. Our results show that even moderate warming affected the functioning of key benthic species, and we identified a level of resistance to predicted ocean acidification. Importantly, we show that the presence of a second functional group enhanced the functioning of both groups (mussels and algae), independent of changing environmental conditions, which highlights the ecological and potential economic benefits of conserving biodiversity in marine ecosystems.
Continue reading ‘Key benthic species are affected by predicted warming in winter but show resistance to ocean acidification’Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum
Published 18 September 2024 Science ClosedTags: algae, biogeochemistry, biological response, calcification, laboratory, North Atlantic
Highlights
- The δ11B of coralline algae skeleton offer a means to reconstruct coastal pH.
- 2D maps of trace element content and δ11B were collected on Boreolithothamniom cf. soriferum.
- These images were aligned using correlated multimodal imaging techniques.
- We reconstruct an ocean acidification trend of −0.018 pH units yr-1 in Loch Sween.
- Loch Sween switched from being a substantial sink of CO2 to a source in ∼2008.
Abstract
Ocean Acidification (OA) arises from the increase in atmospheric carbon dioxide concentration following the industrial revolution. The ecological and socio-economic consequences of OA were first identified around 10–15 years ago but remain poorly understood. This is particularly true in coastal regions where local processes can have dramatic consequences on pH trends through time, obscuring and compounding the long-term effects from rising atmospheric CO2. Here we explore the possibility of generating long records of coastal ocean pH using the skeletons of widely distributed coralline algae (CA). The skeletons of these slow growing (<1 mm/year) taxa often contain micron-scale heterogeneities, making sampling for high-resolution climate reconstructions using bulk sampling techniques difficult. Here we use laser ablation coupled to inductively coupled plasma mass spectrometers to generate high-resolution 2D images of the element/calcium ratios and boron isotope composition (δ11B) of a sample of Boreolithothamniom cf. soriferum from Loch Sween in Scotland, UK where we have been monitoring temperature since 2004 and pH during 2014. By carefully correlating the geochemical images with a scanning electron microscopy image we can segment them to remove the marginal portions of the skeleton, isolating the central growth axis to generate an age model and growth rate. The δ11B-pH is significantly elevated above the seawater pH in Loch Sween (8.4 to 8.9 vs. 7.9 to 8.1) consistent with other CA that show internal pH elevation. On a seasonal scale, internal pH is negatively correlated with temperature and also exhibits a long-term decline. By removing this temperature effect, internal pH can be correlated to seawater pH during the 2014 monitoring period allowing us to reconstruct a seawater acidification trend from 2004 to 2018 of -0.018 pH units per year, 10x higher than open ocean trends but consistent with contemporaneous monitoring efforts of UK coastal waters. Reconstructed aqueous CO2 suggests that prior to ∼2008 Loch Sween was a sink of CO2 but after this date, particularly during the early summer, it was a substantial CO2 source. Comparison of reconstructed aqueous CO2 with a record of calcification rate of our sample of Boreolithothamniom cf. soriferum suggests this acidification and associated rise in local seawater pCO2 may have freed this sample from carbon limitation leading to a recent increase in calcification.
Continue reading ‘Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum’Effects of ocean acidification and nitrogen limitation on the growth and photophysiological performances of marine macroalgae Gracilariopsis lemaneiformis
Published 11 September 2024 Science ClosedTags: algae, biological response, growth, laboratory, morphology, North Pacific, photosynthesis, physiology, respiration
To investigate the effects of ocean acidification (OA) and nitrogen limitation on macroalgae growth and photophysiological responses, Gracilariopsis lemaneiformis was cultured under two main conditions: ambient (Low CO2, LC, 390 μatm) and CO2 enriched (High CO2, HC, 1000 μatm), with low (LN, 7 μmol L-1) and high (HN, 56 μmol L-1) nitrate. High CO2 levels decreased growth under both LN and HN treatments. HC reduced Chl a, carotenoids, phycoerythrin (PE), and phycocyanin (PC) under HN conditions, while only Chl a decreased under LN conditions. NO3– uptake rate was restricted under LN compared to HN, while HC enhanced it under HN. Net photosynthetic O2 evolution rates did not differ between CO2 and nitrate treatments. Dark respiration rates were higher under HN, further boosted by HC. The stimulated effective quantum yield (Y(II)) corresponded to decreased non-photochemical quenching (NPQ) under HN conditions. Nitrate, not CO2, showed significant effects on the relative electron transport rate (rETRmax), light use efficiency (α) and saturation light intensity (Ik) that with lowered rETRmax and α under LN culture. Our results indicate that OA may negatively affect Gracilariopsis lemaneiformis growth and alter its photophysiological performance under different nutrient conditions.
Continue reading ‘Effects of ocean acidification and nitrogen limitation on the growth and photophysiological performances of marine macroalgae Gracilariopsis lemaneiformis’Harmful algal blooms in eutrophic marine environments: causes, monitoring, and treatment
Published 6 September 2024 Science ClosedTags: algae, mitigation, review
Marine eutrophication, primarily driven by nutrient over input from agricultural runoff, wastewater discharge, and atmospheric deposition, leads to harmful algal blooms (HABs) that pose a severe threat to marine ecosystems. This review explores the causes, monitoring methods, and control strategies for eutrophication in marine environments. Monitoring techniques include remote sensing, automated in situ sensors, modeling, forecasting, and metagenomics. Remote sensing provides large-scale temporal and spatial data, while automated sensors offer real-time, high-resolution monitoring. Modeling and forecasting use historical data and environmental variables to predict blooms, and metagenomics provides insights into microbial community dynamics. Control treatments encompass physical, chemical, and biological treatments, as well as advanced technologies like nanotechnology, electrocoagulation, and ultrasonic treatment. Physical treatments, such as aeration and mixing, are effective but costly and energy-intensive. Chemical treatments, including phosphorus precipitation, quickly reduce nutrient levels but may have ecological side effects. Biological treatments, like biomanipulation and bioaugmentation, are sustainable but require careful management of ecological interactions. Advanced technologies offer innovative solutions with varying costs and sustainability profiles. Comparing these methods highlights the trade-offs between efficacy, cost, and environmental impact, emphasizing the need for integrated approaches tailored to specific conditions. This review underscores the importance of combining monitoring and control strategies to mitigate the adverse effects of eutrophication on marine ecosystems.
Continue reading ‘Harmful algal blooms in eutrophic marine environments: causes, monitoring, and treatment’Can niche plasticity mediate species persistence under ocean acidification?
Published 27 August 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, field, fish, performance, vents
Global change stressors can modify ecological niches of species, thereby altering ecological interactions within communities and food webs. Yet, some species might take advantage of a fast-changing environment, allowing species with high niche plasticity to thrive under climate change.
We used natural CO2 vents to test the effects of ocean acidification on niche modifications of a temperate rocky reef fish assemblage. We quantified three ecological niche traits (overlap, shift and breadth) across three key niche dimensions (trophic, habitat and behavioural).
Only one species increased its niche width along multiple niche dimensions (trophic and behavioural), shifted its niche in the remaining (habitat) was the only species to experience a highly increased density (i.e. doubling) at vents. The other three species that showed slightly increased or declining densities at vents only displayed a niche width increase in one (habitat niche) out of seven niche metrics considered. This niche modification was likely in response to habitat simplification (transition to a system dominated by turf algae) under ocean acidification.
We further showed that, at the vents, the less abundant fishes had a negligible competitive impact on the most abundant and common species. This species appeared to expand its niche space, overlapping with other species, which likely led to lower abundances of the latter under elevated CO2.
We conclude that niche plasticity across multiple dimensions could be a potential adaptation in fishes to benefit from a changing environment in a high-CO2 world.
Continue reading ‘Can niche plasticity mediate species persistence under ocean acidification?’
