Call for submissions for special issue: “The effects of ocean acidification on the species across the lower trophic levels in the pelagic realm”

Deadline for manuscript submissions: 31 July 2019

Special Issue description: The overarching aim of this Special Issue focuses on establishing how ocean acidification (OA) drives changes across pelagic species and communities from molecular to cellular to physiological to population levels and demonstrating our capacity to improve the forecasting and management of the emerging effects of OA in dynamic, complex systems. This Special Issue welcomes the integration of various complementary approaches, ranging from field experiments with laboratory manipulations to synthesis and modelling approaches with the aim to advance a mechanistic understanding across different levels of biological organization, as well as to improve the prediction of OA emerging effects. Studies can use a variety of natural systems that represent natural analogues for OA or are characterized by the variability that determines overall OA exposure in the pelagic realm. With topics describing the species sensitivity and resiliency aspects, biological thresholds, and OA-driven species distribution and habitat suitability modelling, this Special Issue aims to contribute to the overall biological vulnerability assessment of pelagic species and communities to OA. Studies that include multiple drivers are warranted if that will ultimately drive overall pelagic vulnerability or resilience to OA.

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Hawaiian ‘supercorals’ that can tolerate warm, acidic waters offer hope for the future

Human activity such as carbon emissions and pollution are threatening coral colonies across the globe. Some believe that at this rate, the world’s coral reefs will collapse within a couple of decades. But that’s assuming all coral are the same, which is not true. Some coral species are more resilient than others, and some — such as those growing in Hawaii’s Kāne’ohe Bay — are so tolerant to warm and acidic waters that scientists are calling them “supercorals”.

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Observing changes in ocean carbonate chemistry: our autonomous future

Our developing network of autonomous carbonate observations is currently targeted at surface ocean CO2 fluxes and compact ecosystem observatories. New integration of developed sensors on gliders and surface vehicles will increase our coastal and regional observational capability. Most autonomous platforms observe a single carbonate parameter, which leaves us reliant on the use of empirical relationships to constrain the rest of the carbonate system. Sensors now in development promise the ability to observe multiple carbonate system parameters from a range of vehicles in the near future.

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Proteomic responses to ocean acidification of the marine diazotroph Trichodesmium under iron-replete and iron-limited conditions

Growth and dinitrogen (N2) fixation of the globally important diazotrophic cyanobacteria Trichodesmium are often limited by iron (Fe) availability in surface seawaters. To systematically examine the combined effects of Fe limitation and ocean acidification (OA), T. erythraeum strain IMS101 was acclimated to both Fe-replete and Fe-limited concentrations under ambient and acidified conditions. Proteomic analysis showed that OA affected a wider range of proteins under Fe-limited conditions compared to Fe-replete conditions. OA also led to an intensification of Fe deficiency in key cellular processes (e.g., photosystem I and chlorophyll a synthesis) in already Fe-limited T. erythraeum. This is a result of reallocating Fe from these processes to Fe-rich nitrogenase to compensate for the suppressed N2 fixation. To alleviate the Fe shortage, the diazotroph adopts a series of Fe-based economic strategies (e.g., upregulating Fe acquisition systems for organically complexed Fe and particulate Fe, replacing ferredoxin by flavodoxin, and using alternative electron flow pathways to produce ATP). This was more pronounced under Fe-limited-OA conditions than under Fe limitation only. Consequently, OA resulted in a further decrease of N2- and carbon-fixation rates in Fe-limited T. erythraeum. In contrast, Fe-replete T. erythraeum induced photosystem I (PSI) expression to potentially enhance the PSI cyclic flow for ATP production to meet the higher demand for energy to cope with the stress caused by OA. Our study provides mechanistic insight into the holistic response of the globally important N2-fixing marine cyanobacteria Trichodesmium to acidified and Fe-limited conditions of future oceans.

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OA-ICC bibliographic database updated

An updated version of the OA-ICC bibliographic database is available online.

The database currently contains more than 5,520 references and includes citations, abstracts and assigned keywords. Updates are made every month.

The database is available as a group on Mendeley. Subscribe online or, for a better user experience, download the Mendeley Desktop application and sync with the group Ocean Acidification (OA-ICC). Please see the “User instructions” for further details.

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CO2 effects on diatoms: a synthesis of more than a decade of ocean acidification experiments with natural communities

Diatoms account for 40 % of marine primary production and are considered to be key players in the biological carbon pump. Ocean acidification (OA) is expected to affect diatoms primarily by changing the availability of CO2 as a substrate for photosynthesis or through altered ecological interactions within the marine food web. Yet, there is little consensus how entire diatom communities will respond to increasing CO2. To address this question, we synthesized the literature from over a decade of OA-experiments with natural diatom communities to uncover: 1) if and how bulk diatom communities respond to elevated CO2; 2) if shifts within the diatom communities could be expected and how they are expressed with respect to taxonomic affiliation and size structure. We found that diatom communities responded to high CO2 in ~60 % of the experiments and in this case more often positively (56 %) than negatively (32 %; 12 % did not report the direction of change). Shifts among different diatom species were observed in 65 % of the experiments. Our synthesis supports the hypothesis that high CO2 particularly favors larger species as 12 out of 13 experiments which investigated cell size found a shift towards larger species. Unraveling winners and losers with respect to taxonomic affiliation was difficult due to a limited database, but there is evidence that the genus Pseudo-nitzschia could be among the losers. We conclude that OA-induced changes in diatom competitiveness and assemblage structure must be classified as a “risk for ecosystem services” due to the pivotal role diatoms play in trophic transfer and biogeochemical cycles.

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Adaptive responses and local stressor mitigation drive coral resilience in warmer, more acidic oceans

Coral reefs have great biological and socioeconomic value, but are threatened by ocean acidification, climate change and local human impacts. The capacity for corals to adapt or acclimatize to novel environmental conditions is unknown but fundamental to projected reef futures. The coral reefs of Kāne‘ohe Bay, Hawai‘i were devastated by anthropogenic insults from the 1930s to 1970s. These reefs experience naturally reduced pH and elevated temperature relative to many other Hawaiian reefs which are not expected to face similar conditions for decades. Despite catastrophic loss in coral cover owing to human disturbance, these reefs recovered under low pH and high temperature within 20 years after sewage input was diverted. We compare the pH and temperature tolerances of three dominant Hawaiian coral species from within Kāne‘ohe Bay to conspecifics from a nearby control site and show that corals from Kāne‘ohe are far more resistant to acidification and warming. These results show that corals can have different pH and temperature tolerances among habitats and understanding the mechanisms by which coral cover rebounded within two decades under projected future ocean conditions will be critical to management. Together these results indicate that reducing human stressors offers hope for reef resilience and effective conservation over coming decades.

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Ocean acidification in the IPCC AR5 WG II

OUP book