Posts Tagged 'BRcommunity'

From marine snails to marine spatial planning : the science of human impacts and relationships with marine ecosystems

Extractive human systems are driving unprecedented biodiversity loss and exacerbating social inequity. The magnitude of the intertwined climate, biodiversity, and social inequity crises has prompted the development of interdisciplinary research approaches to address these complex problems. One such approach, social-ecological systems (SES), aims to understand the relationships between coupled human and ecological systems. This thesis applies an SES lens to understand the science of human impacts on and relationships with marine ecosystems and inform characterizations of system vulnerability. First, I examined the sensitivity of marine ectothermic animals to climate change by conducting a meta-analysis of the effects of ocean acidification and warming. My synthesis of nearly five hundred factorial studies demonstrates the negative effects of these two drivers, identifies specific taxonomic groups (molluscs), life- history traits (adults, sessile), and latitudes (tropical and temperate) that are more sensitive, and refutes two common assumptions about the drivers’ interactive effects. Next, I tested whether populations of a marine snail vary in their vulnerability to ocean warming based on thermal sensitivity and local rates of ocean warming. Using coupled lab and field experiments with snails from two regions in the middle of their range that differ in thermal characteristics, I found that snails from the warmer Salish Sea, an urban sea, showed greater vulnerability to ocean warming than those from the cooler central coast of British Columbia, Canada. Finally, to inform how humans can mitigate our impacts while sustaining complex relationships with the ocean, I partnered with the Sḵwx̲wú7mesh Úxwumixw (Squamish Nation) and regional stewardship organizations on a marine spatial planning project in the Salish Sea. I employed a mixed- methods community-based participatory mapping approach to characterize place-based values and outline opportunities to decolonize research and mapping processes. The results contribute important social data about place-based values, reveal value interactions, reflect knowledge system plurality, and identify avenues to advance reconciliation. Overall, this thesis highlights the vulnerability of marine life, particularly life within urban seas, to climate change and provides a roadmap for researchers and decision-makers to meaningfully steward the health and well-being of coastal social-ecological systems.

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Anthropogenic changes to the nighttime environment

How the relative impacts of anthropogenic pressures on the natural environment vary between different taxonomic groups, habitats, and geographic regions is increasingly well established. By contrast, the times of day at which those pressures are most forcefully exerted or have greatest influence are not well understood. The impact on the nighttime environment bears particular scrutiny, given that for practical reasons (e.g., researchers themselves belong to a diurnal species), most studies on the impacts of anthropogenic pressures are conducted during the daytime on organisms that are predominantly day active or in ways that do not differentiate between daytime and nighttime. In the present article, we synthesize the current state of knowledge of impacts of anthropogenic pressures on the nighttime environment, highlighting key findings and examples. The evidence available suggests that the nighttime environment is under intense stress across increasing areas of the world, especially from nighttime pollution, climate change, and overexploitation of resources.

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Long-term adaptation to elevated temperature but not CO2 alleviates the negative effects of ultraviolet-B radiation in a marine diatom

Multifaceted changes in marine environments as a result of anthropogenic activities are likely to have a compounding impact on the physiology of marine phytoplankton. Most studies on the combined effects of rising pCO2sea surface temperature, and UVB radiation on marine phytoplankton were only conducted in the short-term, which does not allow to test the adaptive capacity of phytoplankton and associated potential trade-offs. Here, we investigated populations of the diatom Phaeodactylum tricornutum that were long-term (∼3.5 years, ∼3000 generations) adapted to elevated CO2 and/or elevated temperatures, and their physiological responses to short-term (∼2 weeks) exposure of two levels of ultraviolet-B (UVB) radiation. Our results showed that while elevated UVB radiation showed predominantly negative effects on the physiological performance of P. tricornutum regardless of adaptation regimes. Elevated temperature alleviated these effects on most of the measured physiological parameters (e.g., photosynthesis). We also found that elevated CO2 can modulate these antagonistic interactions, and conclude that long-term adaptation to sea surface warming and rising CO2 may alter this diatom’s sensitivity to elevated UVB radiation in the environment. Our study provides new insights into marine phytoplankton’s long-term responses to the interplay of multiple environmental changes driven by climate change.

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Coral adaptive capacity insufficient to halt global transition of coral reefs into net erosion under climate change

Projecting the effects of climate change on net reef calcium carbonate production is critical to understanding the future impacts on ecosystem function, but prior estimates have not included corals’ natural adaptive capacity to such change. Here we estimate how the ability of symbionts to evolve tolerance to heat stress, or for coral hosts to shuffle to favourable symbionts, and their combination, may influence responses to the combined impacts of ocean warming and acidification under three representative concentration pathway (RCP) emissions scenarios (RCP2.6, RCP4.5 and RCP8.5). We show that symbiont evolution and shuffling, both individually and when combined, favours persistent positive net reef calcium carbonate production. However, our projections of future net calcium carbonate production (NCCP) under climate change vary both spatially and by RCP. For example, 19%–35% of modelled coral reefs are still projected to have net positive NCCP by 2050 if symbionts can evolve increased thermal tolerance, depending on the RCP. Without symbiont adaptive capacity, the number of coral reefs with positive NCCP drops to 9%–13% by 2050. Accounting for both symbiont evolution and shuffling, we project median positive NCPP of coral reefs will still occur under low greenhouse emissions (RCP2.6) in the Indian Ocean, and even under moderate emissions (RCP4.5) in the Pacific Ocean. However, adaptive capacity will be insufficient to halt the transition of coral reefs globally into erosion by 2050 under severe emissions scenarios (RCP8.5).

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Projected effects of climate change on marine ecosystems in Southeast Asian seas

The seas of Southeast Asia are home to some of the world’s most diverse ecosystems and resources that support the livelihoods of millions of people. Climate change will bring temperature changes, acidification and other environmental change, with uncertain consequences for human and natural systems, but there has been little regional-scale climate modelling of the marine ecosystem. We present initial dynamically downscaled projections using a biogeochemical model suitable for coastal and shelf seas. A coupled physical-biogeochemical model with a resolution of 0.1° (approximately 11 km) was used to create projections of future environmental conditions under moderate (RCP4.5) and high (RCP8.5) greenhouse gas scenarios. Changes for different parts of the region are presented, including four sensitive coastal sites of key importance for biodiversity and sustainable development: UNESCO Biosphere Reserves at Cu Lao Cham-Hoi An in Vietnam, Palawan in the Philippines and Taka Bonerate-Kepulauan Selayar in Indonesia, and coastal waters of Sabah, Malaysia, which include several marine parks. The projections show a sea that is warming by 1.1 to 2.9°C through the 21st century, with dissolved oxygen decreasing by 5 to 13 mmol m-3 and changes in many other environmental variables. The changes reach all parts of the water column and many places are projected to experience conditions well outside the range seen at the start of the century. The resulting damage to coral reefs and altered species distribution would have consequences for biodiversity, the livelihoods of small-scale fishers and the food security of coastal communities. Further work using a range of global models and regional models with different biogeochemical components is needed to provide confidence levels, and we suggest some ways forward. Projections of this type serve as a key tool for communities and policymakers as they plan how they will adapt to the challenge of climate change.

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Ocean acidification alters the benthic biofilm communities in intertidal soft sediments

Microphytobenthos (MPB) and bacterial biofilms play crucial roles in primary and secondary production, nutrient cycling and invertebrate settlement in coastal ecosystems, yet little is known of the effects of ocean acidification (OA) on these communities in intertidal soft sediments. To fill in this gap, a 28-day CO2 enhancement experiment was conducted for the benthic biofilms in soft intertidal sediments (muds and sands) from Qingdao, China. This experiment included three CO2 treatments: 400 ppm CO2 (control), 700 ppm CO2 and 1000 ppm CO2 (IPCC predicted value in 2100), which were established in a three-level CO2 incubator that can adjust the CO2 concentration in the overlying air. The effects of OA on benthic biofilms were assessed in the following three aspects: MPB biomass, biofilm community structure and microbial biogeochemical cycling (e.g., C-cycle, N-cycle and S-cycle). This study found that the 700 ppm CO2 treatment did not significantly affect the benthic biofilms in intertidal soft sediments, but the 1000 ppm CO2 treatment significantly altered the biofilm community composition and potentially their role in microbial biogeochemical cycling in sediments (especially in sandy sediments). For the bacterial community in biofilms, the 1000 ppm CO2 enhancement increased the relative abundance of Alteromonadales and Bacillales but decreased the relative abundance of Rhodobacterales and Flavobacteriales. For microbial biogeochemical cycling, the 1000 ppm CO2 treatment enhanced the potential of chemoheterotrophic activity, nitrate reduction and sulfur respiration in sediments, likely resulting in a more stressful environment (hypoxic and enriched H2S) for most benthic organisms. Even though incubations in this study were only 28 days long and thus couldn’t fully accommodate the range of longer-term adaptions, it still suggests that benthic biofilms in intertidal sandy sediments are likely to change significantly near the end of the century if anthropogenic CO2 emissions unmitigated, with profound implications on local ecosystems and biogeochemical cycling.

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Two treatment methods on Ulva prolifera bloom result in distinctively different ecological effects in coastal environment

Green tides Ulva prolifera have broken out in the Yellow Sea for more than 10 years, becoming a periodic ecological disaster. The largest-ever green tide that occurred in 2021 promoted innovation in treatment methods. Different from the traditional harvest-disposal method, a microbial complex formulation was firstly sprayed on the harvest U. prolifera that promotes rapid degradation, and then fermented and disposed into the sea. At present, little was known about the ecological effects of those different treatment methods. In order to examine this hypothesis, we run an in-lab incubation of 60 days to simulate the two methods to degrade U. prolifera, with focuses on the degradation ensued impacts on water quality. The degradation process of fresh U. prolifera over two months was dominated by the continuous and slow release of DOM, and the concentration of DOM in the water column was hardly observed to decrease within two months. The pre-discomposed-disposal method also significantly altered microbial community structure. The pre-decomposing treatment with microbial complex formulations destroyed U. prolifera cell tissues and changed its physical state in seawater from floating to fast depositing, and increased the degradation rate by about 14 times. The rapid decomposition of the released bioactive organic matter consumed a substantial amount of dissolved oxygen in local seawater, which has the potential risk of causing local hypoxia and acidification in a short-term. The pre-decomposition treatment of U. prolifera could be a practical and efficient countermeasures to U. prolifera blooming. After the complete degradation of the pre-decomposed U. prolifera, the resulting dissolved organic matter could increase TA to resist acidification. Overall, compared with traditional harvest-packing-disposal method, the pre-decomposing-disposal treatment is an efficient and environmental-friendly disposal method to deal with the U. prolifera “green tide”, but it should be used cautiously.

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Macroalgal cover on coral reefs: spatial and environmental predictors, and decadal trends in the Great Barrier Reef

Macroalgae are an important component of coral reef ecosystems. We identified spatial patterns, environmental drivers and long-term trends of total cover of upright fleshy and calcareous coral reef inhabiting macroalgae in the Great Barrier Reef. The spatial study comprised of one-off surveys of 1257 sites (latitude 11–24°S, coastal to offshore, 0–18 m depth), while the temporal trends analysis was based on 26 years of long-term monitoring data from 93 reefs. Environmental predictors were obtained from in situ data and from the coupled hydrodynamic-biochemical model eReefs. Macroalgae dominated the benthos (≥50% cover) on at least one site of 40.4% of surveyed inshore reefs. Spatially, macroalgal cover increased steeply towards the coast, with latitude away from the equator, and towards shallow (≤3 m) depth. Environmental conditions associated with macroalgal dominance were: high tidal range, wave exposure and irradiance, and low aragonite saturation state, Secchi depth, total alkalinity and temperature. Evidence of space competition between macroalgal cover and hard coral cover was restricted to shallow inshore sites. Temporally, macroalgal cover on inshore and mid-shelf reefs showed some fluctuations, but unlike hard corals they showed no systematic trends. Our extensive empirical data may serve to parameterize ecosystem models, and to refine reef condition indices based on macroalgal data for Pacific coral reefs.

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Sponge organic matter recycling: reduced detritus production under extreme environmental conditions


  • Sponge metabolism was measured at the natural laboratory of Bouraké where sponges are naturally exposed to extreme conditions associated with tidal phase.
  • The photosymbiotic HMA sponge Rhabdastrella globostellata was able to cope with extreme acidification and deoxygenation seawater.
  • Photosynthetic activity of sponge symbionts was negatively affected during extreme environmental conditions.
  • The sponge loop pathway was disrupted during low tide, which correlated with extreme acidification, deoxygenation and warming seawater.


Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. During two years (2018 and 2020), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions.

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Effect of ocean acidification on the growth, response and hydrocarbon degradation of coccolithophore-bacterial communities exposed to crude oil

Hydrocarbon-degrading bacteria, which can be found living with eukaryotic phytoplankton, play a pivotal role in the fate of oil spillage to the marine environment. Considering the susceptibility of calcium carbonate-bearing phytoplankton under future ocean acidification conditions and their oil-degrading communities to oil exposure under such conditions, we investigated the response of non-axenic E. huxleyi to crude oil under ambient versus elevated CO2 concentrations. Under elevated CO2 conditions, exposure to crude oil resulted in the immediate decline of E. huxleyi, with concomitant shifts in the relative abundance of Alphaproteobacteria and Gammaproteobacteria. Survival of E. huxleyi under ambient conditions following oil enrichment was likely facilitated by enrichment of oil-degraders Methylobacterium and Sphingomonas, while the increase in relative abundance of Marinobacter and unclassified Gammaproteobacteria may have increased competitive pressure with E. huxleyi for micronutrient acquisition. Biodegradation of the oil was not affected by elevated CO2 despite a shift in relative abundance of known and putative hydrocarbon degraders. While ocean acidification does not appear to affect microbial degradation of crude oil, elevated mortality responses of E. huxleyi and shifts in the bacterial community illustrates the complexity of microalgal-bacterial interactions and highlights the need to factor these into future ecosystem recovery projections.

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Ocean acidification conditions and marine diatoms

Ocean acidification doesn’t just erode calcium carbonate shells. It can also slow the rate of diatoms to build their beautiful, intricate silica cell walls. Thinner walls mean lighter diatoms making the algae less able to transport carbon to the deep ocean. Diatoms are a key group of non-calcifying marine phytoplankton, responsible for ~40% of ocean productivity. Growth, cell size, and silica content are strong determinants of diatom resilience and sinking velocity; therefore, the effect of diatom species on ocean biogeochemistry is a function of its growth strategy, size, and frustule thickness. In natural environments, pH directly affects the diatom’s growth rate and therefore the timing and abundance of species. Consequently, understanding impacts of ocean acidification on diatom community structure is crucial for evaluating the sensitivity of biogeochemical cycles and ecosystem services in the world’s oceans.

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Volcanic-associated ecosystems of the Mediterranean Sea: a systematic map and an interactive tool to support their conservation


Hydrothermal vents, cold seeps, pockmarks and seamounts are widely distributed on the ocean floor. Over the last fifty years, the knowledge about these volcanic-associated marine ecosystems has notably increased, yet available information is still limited, scattered, and unsuitable to support decision-making processes for the conservation and management of the marine environment.


Here we searched the Scopus database and the platform Web of Science to collect the scientific information available for these ecosystems in the Mediterranean Sea. The collected literature and the bio-geographic and population variables extracted are provided into a systematic map as an online tool that includes an updated database searchable through a user-friendly R-shiny app.


The 433 literature items with almost one thousand observations provided evidence of more than 100 different volcanic-associated marine ecosystem sites, mostly distributed in the shallow waters of the Mediterranean Sea. Less than 30% of these sites are currently included in protected or regulated areas. The updated database available in the R-shiny app is a tool that could guide the implementation of more effective protection measures for volcanic-associated marine ecosystems in the Mediterranean Sea within existing management instruments under the EU Habitats Directive. Moreover, the information provided in this study could aid policymakers in defining the priorities for the future protection measures needed to achieve the targets of the UN Agenda 2030.

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High taxonomic diversity and miniaturization in benthic communities under persistent natural CO2 disturbances

Metabarcoding techniques have revolutionized ecological research in recent years, facilitating the differentiation of cryptic species and revealing previously hidden diversity. In the current scenario of climate change and ocean acidification, biodiversity loss is one of the main threats to marine ecosystems. Here, we explored the effects of ocean acidification on marine benthic communities using DNA metabarcoding to assess the diversity of algae and metazoans. Specifically, we examined the natural pH gradient generated by the Fuencaliente CO2 vent system, located near La Palma Island (Canary Islands). High-resolution COI metabarcoding analyses revealed high levels of taxonomic diversity in an acidified natural area for the first time. This high number of species arises from the detection of small and cryptic species that were previously undetectable by other techniques. Such species are apparently tolerant to the acidification levels expected in future oceans. Hence and following our results, future subtropical communities are expected to keep high biodiversity values under an acidification scenario, although they will tend toward overall miniaturization due to the dominance of small algal and invertebrate species, leading to changes in ecosystem functions.


Electronic supplementary material is available online at

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Sediment-seawater exchange altered adverse effects of ocean acidification towards marine microalgae


  • Five marine microalgal species showed different sensitivities to OA.
  • OA promoted algal growth except I. galbana after introducing sediments.
  • N, P and Fe released from sediments mitigated OA-induced toxicity to E. huxleyi.
  • OA-induced algal community instability was alleviated by the presence of sediments.


Ocean acidification (OA) exhibits high threat to marine microalgae. However, the role of marine sediment in the OA-induced adverse effect towards microalgae is largely unknown. In this work, the effects of OA (pH 7.50) on the growth of individual and co-cultured microalgae (Emiliania huxleyiIsochrysis galbanaChlorella vulgarisPhaeodactylum tricornutum, and Platymonas helgolandica tsingtaoensis) were systematically investigated in the sediment-seawater systems. OA inhibited E. huxleyi growth by 25.21 %, promoted P. helgolandica (tsingtaoensis) growth by 15.49 %, while did not cause any effect on the other three microalgal species in the absence of sediment. In the presence of the sediment, OA-induced growth inhibition of E. huxleyi was significantly mitigated, because the released chemicals (N, P and Fe) from seawater-sediment interface increased the photosynthesis and reduced oxidative stress. For P. tricornutum, C. vulgaris and P. helgolandica (tsingtaoensis), the growth was significantly increased in the presence of sediment in comparison with those under OA alone or normal seawater (pH 8.10). For I. galbana, the growth was inhibited when the sediment was introduced. Additionally, in the co-culturing system, C. vulgaris and P. tricornutum were the dominant species, while OA increased the proportions of dominant species and decreased the community stability as indicated by Shannon and Pielou’s indexes. After the introduction of sediment, the community stability was recovered, but remained lower than that under normal condition. This work demonstrated the role of sediment in the biological responses to OA, and could be helpful for better understanding the impact of OA on marine ecosystems.

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Ocean acidification drives gut microbiome changes linked to species-specific immune defence

Ocean acidification (OA) has important effects on the intrinsic phenotypic characteristics of many marine organisms. Concomitantly, OA can alter the extended phenotypes of these organisms by perturbing the structure and function of their associated microbiomes. It is unclear, however, the extent to which interactions between these levels of phenotypic change can modulate the capacity for resilience to OA. Here, we explored this theoretical framework assessing the influence of OA on intrinsic (immunological responses and energy reserve) and extrinsic (gut microbiome) phenotypic characteristics and the survival of important calcifiers, the edible oysters Crassostrea angulata and C. hongkongensis. After one-month exposure to experimental OA (pH 7.4) and control (pH 8.0) conditions, we found species-specific responses characterised by elevated stress (hemocyte apoptosis) and decreased survival in the coastal species (C. angulata) compared with the estuarine species (C. hongkongensis). Phagocytosis of hemocytes was not affected by OA but in vitro bacterial clearance capability decreased in both species. Gut microbial diversity decreased in C. angulata but not in C. hongkongensis. Overall, C. hongkongensis was capable of maintaining the homeostasis of the immune system and energy supply under OA. In contrast, C. angulata’s immune function was suppressed, and the energy reserve was imbalanced, which might be attributed to the declined microbial diversity and the functional loss of essential bacteria in the guts. This study highlights a species-specific response to OA determined by genetic background and local adaptation, shedding light on the understanding of host-microbiota-environment interactions in future coastal acidification.

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

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.

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

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.

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Evaluation of the current understanding of the impact of climate change on coral physiology after three decades of experimental research

After three decades of coral research on the impacts of climate change, there is a wide consensus on the adverse effects of heat-stress, but the impacts of ocean acidification (OA) are not well established. Using a review of published studies and an experimental analysis, we confirm the large species-specific component of the OA response, which predicts moderate impacts on coral physiology and pigmentation by 2100 (scenario-B1 or SSP2-4.5), in contrast with the severe disturbances induced by only +2 °C of thermal anomaly. Accordingly, global warming represents a greater threat for coral calcification than OA. The incomplete understanding of the moderate OA response relies on insufficient attention to key regulatory processes of these symbioses, particularly the metabolic dependence of coral calcification on algal photosynthesis and host respiration. Our capacity to predict the future of coral reefs depends on a correct identification of the main targets and/or processes impacted by climate change stressors.

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Seasonal net calcification by secondary calcifiers in coral reefs of the Eastern Tropical Pacific Ocean

This study assesses whether secondary calcification is driven by a contrasting seasonal pattern (rainy vs dry) that occurs in the Eastern Tropical Pacific (ETP). Secondary calcifiers net calcification rates and coverage were measured in two reefs: the semi-enclosed Bahía Tiburón reef (BT [21°52′30 “N, 105°54/54 “W]) and the open Las Monas fringing reef (LM [21°51ʹ00ʹʹN, 105°52ʹ45ʹʹW]). Measurements were made from 2013 to 2016 using Calcification Accretion Units (CAUs). Seawater temperature, illuminance, pCO2, pH, ΩCa, and ΩAr were also measured. Low means of pCO2, and high means of ΩCa and ΩAr, were measured during the rainy season. At Las Monas, the composition of the calcifier community differed between seasons. A seasonal effect on net calcification was recorded in the semi-enclosed reef and in the exposed microhabitat of both reefs. Overall, net calcification (mean ± SD) was 1.17 ± 1.13 g·CaCO3·m−2·day−1. Calcification in the open fringing reef (1.51 ± 1.32 g·CaCO3·m−2·day−1) was almost double that in the semi-enclosed reef (0.83 ± 0.78 g·CaCO3·m−2·day−1). Calcification also decreased dramatically between 2014 (1.57 g·CaCO3·m−2·day−1) and 2016 (0.99 g·CaCO3·m−2·day−1). The ENSO event of 2015 raised the water temperature almost 1 °C above the decadal average, which led to a mass coral bleaching in both reefs. That thermal stress might explain the calcification decline in 2015–2016, but probably also obscured a clearer seasonal pattern in net calcification. This study is the first to show that anomalous and persistent high seawater temperatures can affect carbonate production by secondary calcifiers.

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Climate change amelioration by marine producers: does dominance predict impact?

Climate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature via shading and mitigating ocean acidification via photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species’ functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.

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