Biological Response of Planktic Foraminifera to Decline in Seawater pH

Understanding the way in which a decline in ocean pH can affect calcareous organisms could enhance our ability to predict the impacts of the potential decline in seawater pH on marine ecosystems, and could help to reconstruct the paleoceanographic events over a geological time scale. Planktic foraminifera are among the most important biological proxies for these studies; however, the existing research on planktic foraminifera is almost exclusively based on their geochemical indices, without the inclusion of information on their biological development. Through a series of on-board experiments in the western tropical Pacific (134°33′54″ E, 12°32′47″ N), the present study showed that the symbiont-bearing calcifier Trilobatus sacculifer—a planktic foraminifer—responded rapidly to a decline in seawater pH, including losing symbionts, bleaching, etc. Several indices were established to quantify the relationships between these biological parameters and seawater pH, which could be used to reconstruct the paleoceanographic seawater pH. We further postulated that the loss of symbionts in planktic foraminifera acts as an adaptive response to the stress of low pH. Our results indicate that an ongoing decline in seawater pH may hinder the growth and calcification of planktic foraminifera by altering their biological processes. A reduction in carbonate deposition and predation could have profound effects on the carbon cycle and energy flow in the marine food web.

Anthropogenic and Climatic Drivers of Long-Term Changes of Mercury and Feeding Ecology in Arctic Beluga (Delphinapterus leucas) Populations

We assessed long-term changes in the feeding ecology and mercury (Hg) accumulation in Eastern High Arctic-Baffin Bay beluga (Delphinapterus leucas) using total Hg and stable isotope (δ¹³C, δ¹⁵N) assays in teeth samples from historical (1854-1905) and modern (1985-2000) populations. Mean δ¹³C values in teeth declined significantly over time, from -13.01 ± 0.55‰ historically to -14.41 ± 0.28‰ in 2000, while no consistent pattern was evident for δ¹⁵N due to high individual variability within each period. The temporal shift in isotopic niche is consistent with beluga feeding ecology changing in recent decades to a more pelagic and less isotopically diverse diet or an ecosystem wide change in isotope profiles. Mercury concentrations in modern beluga teeth were 3-5 times higher on average than those in historical beluga. These results are similar to the long-term trends of Hg and feeding ecology reported in other beluga populations and in other Arctic marine predators. Similar feeding ecology shifts across regions and species indicate a consistent increased pelagic diet response to climate change as the Arctic Ocean progressively warmed and lost sea ice. Previously, significant temporal Hg increase in beluga and other Arctic animals was attributed solely to direct inputs of anthropogenic Hg from long-range sources. Recent advances in understanding the Arctic marine Hg cycle suggest an additional, complementary possibility─increased inputs of terrestrial Hg of mixed anthropogenic-natural origin, mobilized from permafrost and other Arctic soils by climate warming. At present, it is not possible to assign relative importance to the two processes in explaining the rise of Hg concentrations in modern Arctic marine predators.

Atmospheric deposition of inorganic nutrients to the Western North Pacific Ocean

We evaluated the potential impacts of atmospheric deposition on marine productivity and inorganic carbon chemistry in the northwestern Pacific Ocean (8-39°N, 125-157°E). The nutrient concentration in atmospheric total suspended particles decreased exponentially with increasing distance from the closest land-mass (Asia), clearly revealing anthropogenic and terrestrial contributions. The predicted mean depositional fluxes of inorganic nitrogen were approximately 34 and 15 μmol m^-2 d^-1 to the west and east of 140°E, respectively, which were at least two orders of magnitude greater than the inorganic phosphorus flux. On average, atmospheric particulate deposition would support 3-4% of the net primary production along the surveyed tracks, which is equivalent to ~2% of the dissolved carbon increment caused by the penetration of anthropogenic CO₂. Our observations generally fell within the ranges observed over the past 18 years, despite an increasing trend of atmospheric pollution in the source regions during the same period, which implies high temporal and spatial variabilities of atmospheric nutrient concentration in the study area. Continued atmospheric anthropogenic nitrogen deposition may alter the relative abundances of nitrogen and phosphorus.

The calcifying interface in a stony coral primary polyp: An interplay between seawater and an extracellular calcifying space

Stony coral exoskeletons build the foundation for the most biologically diverse marine ecosystems on Earth, coral reefs, which face major threats due to many anthropogenic-related stressors. Therefore, understanding coral biomineralization mechanisms is crucial for coral reef management in the coming decades and for using coral skeletons in geochemical studies. This study combines in-vivo imaging with cryo-electron microscopy and cryo-elemental mapping to gain novel insights into the biological microenvironment and the ion pathways that facilitate biomineralization in primary polyps of the stony coral Stylophora pistillata. We document increased tissue permeability in the primary polyp and a highly dispersed cell packing in the tissue directly responsible for producing the coral skeleton. This tissue arrangement may facilitate the intimate involvement of seawater at the mineralization site, also documented here. We further observe an extensive filopodial network containing carbon-rich vesicles extruding from some of the calicoblastic cells. Single-cell RNA-Sequencing data interrogation supports these morphological observations by showing higher expression of genes involved in filopodia and vesicle structure and function in the calicoblastic cells. These observations provide a new conceptual framework for resolving the ion pathway from the external seawater to the tissue-mineral interface in stony coral biomineralization processes.

Seeking natural analogs to fast-forward the assessment of marine CO2 removal

Mitigating global climate change will require gigaton-scale carbon dioxide removal (CDR) as a supplement to rapid emissions reduction. The oceans cover 71% of the Earth surface and have the potential to provide much of the required CDR. However, none of the proposed marine CDR (mCDR) methods is sufficiently well understood to determine their real-world efficiency and environmental side effects. Here, we argue that using natural mCDR analogs should become the third interconnecting pillar in the mCDR assessment as they bridge the gap between numerical simulations (i.e., large scale/reduced complexity) and experimental studies (i.e., small scale/high complexity). Natural mCDR analogs occur at no cost, can provide a wealth of data to inform mCDR, and do not require legal permission or social license for their study. We propose four simple criteria to identify particularly useful analogs: 1) large scale, 2) abruptness of perturbation, 3) availability of unperturbed control sites, and 4) reoccurrence. Based on these criteria, we highlight four examples: 1) equatorial upwelling as a natural analog for artificial upwelling, 2) downstream of Kerguelen Island for ocean iron fertilization, 3) the Black and Caspian Seas for ocean alkalinity enhancement, and 4) the Great Atlantic Sargassum Belt for ocean afforestation. These natural analogs provide a reality check for experimental assessments and numerical modeling of mCDR. Ultimately, projections of mCDR efficacy and sustainability supported by observations from natural analogs will provide the real-world context for the public debate and will facilitate political decisions on mCDR implementation. We anticipate that a rigorous investigation of natural analogs will fast-forward the urgently needed assessment of mCDR.

Major loss of coralline algal diversity in response to ocean acidification

Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and evaluate their potential future biodiversity and abundance. We found a decrease in the taxonomic diversity of coralline algae with increasing acidification with more than half of the species lost in high pCO₂ conditions. Sporolithales is the oldest order (Lower Cretaceous) and diversified when ocean chemistry favoured low Mg calcite deposition; it is less diverse today and was the most sensitive to ocean acidification. Corallinales were also reduced in cover and diversity but several species survived at high pCO₂ ; it is the most recent order of coralline algae and originated when ocean chemistry favoured aragonite and high Mg calcite deposition. The sharp decline in cover and thickness of coralline algal carbonate deposits at high pCO₂ highlighted their lower fitness in response to ocean acidification. Reductions in CO₂ emissions are needed to limit the risk of losing coralline algal diversity.

Novel and disappearing climates in the global surface ocean from 1800 to 2100

Marine ecosystems are experiencing unprecedented warming and acidification caused by anthropogenic carbon dioxide. For the global sea surface, we quantified the degree that present climates are disappearing and novel climates (without recent analogs) are emerging, spanning from 1800 through different emission scenarios to 2100. We quantified the sea surface environment based on model estimates of carbonate chemistry and temperature. Between 1800 and 2000, no gridpoints on the ocean surface were estimated to have experienced an extreme degree of global disappearance or novelty. In other words, the majority of environmental shifts since 1800 were not novel, which is consistent with evidence that marine species have been able to track shifting environments via dispersal. However, between 2000 and 2100 under Representative Concentrations Pathway (RCP) 4.5 and 8.5 projections, 10-82% of the surface ocean is estimated to experience an extreme degree of global novelty. Additionally, 35-95% of the surface ocean is estimated to experience an extreme degree of global disappearance. These upward estimates of climate novelty and disappearance are larger than those predicted for terrestrial systems. Without mitigation, many species will face rapidly disappearing or novel climates that cannot be outpaced by dispersal and may require evolutionary adaptation to keep pace.

Fluctuating selection and global change: a synthesis and review on disentangling the roles of climate amplitude, predictability and novelty

A formidable challenge for global change biologists is to predict how natural populations will respond to the emergence of conditions not observed at present, termed novel climates. Popular approaches to predict population vulnerability are based on the expected degree of novelty relative to the amplitude of historical climate fluctuations experienced by a population. Here, we argue that predictions focused on amplitude may be inaccurate because they ignore the predictability of environmental fluctuations in driving patterns of evolution and responses to climate change. To address this disconnect, we review major findings of evolutionary theory demonstrating the conditions under which phenotypic plasticity is likely to evolve in natural populations, and how plasticity decreases population vulnerability to novel environments. We outline key criteria that experimental studies should aim for to effectively test theoretical predictions, while controlling for the degree of climate novelty. We show that such targeted tests of evolutionary theory are rare, with marine systems being overall underrepresented in this venture despite exhibiting unique opportunities to test theory. We conclude that with more robust experimental designs that manipulate both the amplitude and predictability of fluctuations, while controlling for the degree of novelty, we may better predict population vulnerability to climate change.

Are biodegradable plastics an environmental rip off?

While the use of biodegradable polymers is recognized as a global strategy to minimize plastic pollution, the technical standards (TS) used to attest their biodegradability may not be in compliance with most environmental parameters observed aquatic ecosystems. Indeed, through a careful assessment of the TS currently in use, this study evidenced that these guidelines cover only a fraction of the biogeochemical parameters seen in nature and largely disregard those that occur in the deep-sea. Thus, these TS may not be able to ensure the degradation of such polymers in natural environments, where microbial activity, pH, temperature, salinity, UV radiation and pressure are highly variable. This raises environmental concern, since relevant parcel of plastic ends up in the oceans reaching deep zones. Therefore, there is an urgent need to revise these TS, which must consider the actual fate of most plastic debris and include assessments under the challenging conditions found at these types of environment, alongside microplastic formation and ecotoxicology effects. Moreover, the next generation of biodegradability tests must be designed to enable a cost-effective implementation and incorporate accurate analytical techniques to assess polymer transformation. Furthermore, certification should provide information on time scale and degradation rates and, preferably, be globally harmonized.

Scenario Simulation of the Impact of China’s Free-Trade Zone Construction on Regional Sustainable Development: A Case Study of the Pearl River Delta Urban Agglomeration

Regional sustainable development is a complex process driven by multiple factors, such as the economy, society, and environment. China has made a series of major adjustments and devised plans, including the establishment of a pilot free-trade zone, to promote regional sustainable development. The pilot free-trade zone, characterized by free trade and the opening up of institutions, changes the path and mode of regional sustainable development to a certain extent. However, an effective empirical quantitative analysis to verify the impact of the pilot free-trade zone on regional sustainable development is lacking. This paper employs the system dynamics method to predict the social–economic–environmental development trends and key control factors of the Pearl River Delta urban agglomeration by considering the unique advantages of system dynamics. The construction of a pilot free-trade zone was set as a control variable to analyze its promoting effect on regional sustainable development. Next, the most suitable model for sustainable development for the future was determined. The results indicate that the construction of the pilot free-trade zone led to significant growth in indicators such as import and export trade, total economic volume, income, and labor force, all of which are conducive to regional sustainable development. Practically, the simulation results provide decision support for promoting the sustainable development of the Pearl River Delta urban agglomeration.

CO2 Activation Within a Superalkali-Doped Fullerene

With the aim of finding a suitable synthesizable superalkali species, using the B3LYP/6-31G* density functional level of theory we provide results for the interaction between the buckminsterfullerene C60 and the superalkali Li3F2. We show that this endofullerene is stable and provides a closed environment in which the superalkali can exist and interact with CO2. It is worthwhile to mention that the optimized Li3F2 structure inside C60 is not the most stable C2v isomer found for the "free" superalkali but the D3h geometry. The binding energy at 0 K between C60 and Li3F2 (D3h) is computed to be 119 kJ mol-1. Once CO2 is introduced in the endofullerene, it is activated, and theO C O ^ angle is bent to 132°. This activation does not follow the previously studied CO2 reduction by an electron transfer process from the superalkali, but it is rather an actual reaction where a F (from Li3F2) atom is bonded to the CO2. From a thermodynamic analysis, both CO2 and the encapsulated [Li3F2⋅CO2] are destabilized in C60 with solvation energies at 0 K of 147 and < -965 kJ mol-1, respectively.

Physiology, niche characteristics and extreme events: Current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic

Given the ecological and biogeochemical importance of rhodolith beds, it is necessary to investigate how future environmental conditions will affect these organisms. We investigated the impacts of increased nutrient concentrations, acidification, and marine heatwaves on the performance of the rhodolith-forming species Lithothamnion crispatum in a short-term experiment, including the recovery of individuals after stressor removal. Furthermore, we developed an ecological niche model to establish which environmental conditions determine its current distribution along the Brazilian coast and to project responses to future climate scenarios. Although L. crispatum suffered a reduction in photosynthetic performance when exposed to stressors, they returned to pre-experiment values following the return of individuals to control conditions. The model showed that the most important variables in explaining the current distribution of L. crispatum on the Brazilian coast were maximum nitrate and temperature. In future ocean conditions, the model predicted a range expansion of habitat suitability for this species of approximately 58.5% under RCP 8.5. Physiological responses to experimental future environmental conditions corroborated model predictions of the expansion of this species' habitat suitability in the future. This study, therefore, demonstrates the benefits of applying combined approaches to examine potential species responses to climate-change drivers from multiple angles.

Adaptive responses of free-living and symbiotic microalgae to simulated future ocean conditions

Marine microalgae are a diverse group of microscopic eukaryotic and prokaryotic organisms capable of photosynthesis. They are important primary producers and carbon sinks but their physiology and persistence are severely affected by global climate change. Powerful experimental evolution technologies are being used to examine the potential of microalgae to respond adaptively to current and predicted future conditions, as well as to develop resources to facilitate species conservation and restoration of ecosystem functions. This review synthesizes findings and insights from experimental evolution studies of marine microalgae in response to elevated temperature and/or pCO₂ . Adaptation to these environmental conditions has been observed in many studies of marine dinoflagellates, diatoms and coccolithophores. An enhancement in traits such as growth and photo-physiological performance and an increase in upper thermal limit have been shown to be possible, although the extent and rate of change differ between microalgal taxa. Studies employing multiple monoclonal replicates showed variation in responses among replicates and revealed the stochasticity of mutations. The work to date is already providing valuable information on species' climate sensitivity or resilience to managers and policymakers but extrapolating these insights to ecosystem- and community-level impacts continues to be a challenge. We recommend future work should include in situ experiments, diurnal and seasonal fluctuations, multiple drivers and multiple starting genotypes. Fitness trade-offs, stable versus plastic responses and the genetic bases of the changes also need investigating, and the incorporation of genome resequencing into experimental designs will be invaluable.

The coral conservation crisis: interacting local and global stressors reduce reef resiliency and create challenges for conservation solutions

Coral reefs are one of the most productive and biodiverse ecosystems in the world. Humans rely on these coral reef ecosystems to provide significant ecological and economic resources; however, coral reefs are threatened by numerous local and global anthropogenic factors that cause significant environmental change. The interactions of these local and global human impacts may increase the rate of coral reef degradation. For example, there are many local influences (i.e., sedimentation and submarine groundwater discharge) that may exacerbate coral bleaching and mortality. Therefore, researchers and resource managers cannot limit their narratives and actions to mitigating a sole stressor. With the continued increase in greenhouse gas emissions, management strategies and restoration techniques need to account for the scale at which environmental change occurs. This review aims to outline the various local and global anthropogenic stressors threatening reef resiliency and address the recent disagreements surrounding present-day conservation practices. Unfortunately, there is no one solution to preserve and restore all coral reefs. Each coral reef region is challenged by numerous interactive stressors that affect its ecosystem response, recovery, and services in various ways. This review discusses, while global reef degradation occurs, local solutions should be implemented to efficiently protect the coral reef ecosystem services that are valuable to marine and terrestrial environments.

Nitrogen Limitation Decreases the Repair Capacity and Enhances Photoinhibition of Photosystem II in a Diatom

Macronutrient limitation and increased solar exposure coincide with ocean warming-enhanced stratification, with consequences for phytoplankton within the upper mixing layer. In this study, we grew a diatom, Thalassiosira punctigera, under nitrogen-limited and replete conditions for more than 14 generations and investigated both the biochemical composition of treated cells and their photochemical responses to high light and UV exposure. The photosynthetic pigment and the particulate organic nitrogen (PON) content significantly decreased in the low nitrate grown cells, with drastic decline of the absorption of UV absorbing compounds. Under an acute exposure to high light or UV radiation, we observed a significant decline in the photochemical yield along with an increase of nonphotosynthetic quenching (NPQ), with the former lowered and the latter raised in the low-nitrogen grown cells. The results reveal a decreased repair rate and enhanced photoinhibition of the diatom under nitrogen limitation when exposed to increased levels of light and UV radiation, suggesting a higher vulnerability of the diatom phytoplankton under influences of oceanic global change.

Early-Stage Recovery of Lithium from Tailored Thermal Conditioned Black Mass Part I: Mobilizing Lithium via Supercritical CO2-Carbonation

In the frame of global demand for electrical storage based on lithium-ion batteries (LIBs), their recycling with a focus on the circular economy is a critical topic. In terms of political incentives, the European legislative is currently under revision. Most industrial recycling processes target valuable battery components, such as nickel and cobalt, but do not focus on lithium recovery. Especially in the context of reduced cobalt shares in the battery cathodes, it is important to investigate environmentally friendly and economic and robust recycling processes to ensure lithium mobilization. In this study, the method early-stage lithium recovery (“ESLR”) is studied in detail. Its concept comprises the shifting of lithium recovery to the beginning of the chemo-metallurgical part of the recycling process chain in comparison to the state-of-the-art. In detail, full NCM (Lithium Nickel Manganese Cobalt Oxide)-based electric vehicle cells are thermally treated to recover heat-treated black mass. Then, the heat-treated black mass is subjected to an H2O-leaching step to examine the share of water-soluble lithium phases. This is compared to a carbonation treatment with supercritical CO2, where a higher extent of lithium from the heat-treated black mass can be transferred to an aqueous solution than just by H2O-leaching. Key influencing factors on the lithium yield are the filter cake purification, the lithium separation method, the solid/liquid ratio, the pyrolysis temperature and atmosphere, and the setup of autoclave carbonation, which can be performed in an H2O-environment or in a dry autoclave environment. The carbonation treatments in this study are reached by an autoclave reactor working with CO2 in a supercritical state. This enables selective leaching of lithium in H2O followed by a subsequent thermally induced precipitation as lithium carbonate. In this approach, treatment with supercritical CO2 in an autoclave reactor leads to lithium yields of up to 79%.

Photophysiological responses of the marine macroalga Gracilariopsis lemaneiformis to ocean acidification and warming

To study the combined effects of ocean acidification (OA) and warming on the growth and photosynthetic performance of the economically important marine macroalga Gracilariopsis lemaneiformis, thalli were grown under ambient low CO₂ (390 μatm, LC) and elevated high CO₂ (1000 μatm, HC) conditions with culture temperatures of 20 °C and 24 °C. Based on the evaluation of growth and photosynthetic responses to light and dissolved inorganic carbon (DIC), HC decreased the growth rate and phycoerythrin (PE) and phycocyanin (PC) levels but increased contents of UV-absorbing compounds (UVACs) in G. lemaneiformis at 20 °C, and high temperature counteracted these effects. Photosynthetic responses such as chlorophyll fluorescence parameters (maximum relative electron transport rate, rETR_max; light use efficiency, α; saturation light intensity, I_k; maximum quantum yield, F_V/F_M; effective quantum yield, Y(II) and non-photochemical quenching, NPQ) were not different among the treatments. However, increased oxygen evolution (P_n) and dark respiration (R_d) rates were observed at 20 °C in the HC treatment. No significant effects of HC on apparent carboxylation efficiency (ACE), maximum oxygen evolution rate (V_max) and DIC affinity for oxygen evolution (K_1/2DIC) were found, and HC synergy with high temperature increased K_1/2DIC. A lower C/N ratio with decreased tissue carbon but increased nitrogen was observed under HC and high-temperature treatment. Our results indicate that high temperature may counteract the negative effects of OA on the growth and pigment characteristics of G. lemaneiformis and improve food quality, as evidenced by enhanced N per biomass.

Intraspecific variation in multiple trait responses of Alexandrium ostenfeldii towards elevated pCO2

Dissolved oceanic CO₂ concentrations are rising as result of increasing atmospheric partial pressure of CO₂ (pCO₂), which has large consequences for phytoplankton. To test how higher CO₂ availability affects different traits of the toxic dinoflagellate Alexandrium ostenfeldii, we exposed three strains of the same population to 400 and 1,000 µatm CO₂, and measured traits including growth rate, cell volume, elemental composition, ¹³C fractionation, toxin content, and volatile organic compounds (VOCs). Strains largely increased their growth rates and particulate organic carbon and nitrogen production with higher pCO₂ and showed significant changes in their VOC profile. One strain showed a significant decrease in both PSP and cyclic imine content and thereby in cellular toxicity. Fractionation against ¹³C increased in response to elevated pCO₂, which may point towards enhanced CO₂ acquisition and/or a downscaling of the carbon concentrating mechanisms. Besides consistent responses in some traits, other traits showed large variation in both direction and strength of responses towards elevated pCO₂. The observed intraspecific variation in phenotypic plasticity of important functional traits within the same population may help A. ostenfeldii to negate the effects of immediate environmental fluctuations and allow populations to adapt more quickly to changing environments.

Effects of climate change factors on marine macroalgae: A review

Marine macroalgae, the main primary producers in coastal waters, play important roles in the fishery industry and global carbon cycles. With progressive ocean global changes, however, they are increasingly exposed to enhanced levels of multiple environmental drivers, such as ocean acidification, warming, heatwaves, UV radiation and deoxygenation. While most macroalgae have developed physiological strategies against variations of these drivers, their eco-physiological responses to each or combinations of the drivers differ spatiotemporally and species-specifically. Many freshwater macroalgae are tolerant of pH drop and its diel fluctuations and capable of acclimating to changes in carbonate chemistry. However, calcifying species, such as coralline algae, are very sensitive to acidification of seawater, which reduces their calcification, and additionally, temperature rise and UV further decrease their physiological performance. Except for these calcifying species, both economically important and harmful macroalgae can benefit from elevated CO₂ concentrations and moderate temperature rise, which might be responsible for increasing events of harmful macroalgal blooms including green macroalgal blooms caused by Ulva spp. and golden tides caused by Sargassum spp. Upper intertidal macroalgae, especially those tolerant of dehydration during low tide, increase their photosynthesis under elevated CO₂ concentrations during the initial dehydration period, however, these species might be endangered by heatwaves, which can expose them to high temperature levels above their thermal windows' upper limit. On the other hand, since macroalgae are distributed in shallow waters, they are inevitably exposed to solar UV radiation. The effects of UV radiation, depending on weather conditions and species, can be harmful as well as beneficial to many species. Moderate levels of UV-A (315-400nm) can enhance photosynthesis of green, brown and red algae, while UV-B (280-315nm) mainly show inhibitory impacts. Although little has been documented on the combined effects of elevated CO₂, temperature or heatwaves with UV radiation, exposures to heatwaves during midday under high levels of UV radiation can be detrimental to most species, especially to their microscopic stages which are less tolerant of climate change induced stress. In parallel, reduced availability of dissolved O₂ in coastal water along with eutrophication might favour the macroalgae's carboxylation process by suppressing their oxygenation or photorespiration. In this review, we analyse effects of climate change-relevant drivers individually and/or jointly on different macroalgal groups and different life cycle stages based on the literatures surveyed, and provide perspectives for future studies.

Human Health and Ocean Pollution

Background

Pollution - unwanted waste released to air, water, and land by human activity - is the largest environmental cause of disease in the world today. It is responsible for an estimated nine million premature deaths per year, enormous economic losses, erosion of human capital, and degradation of ecosystems. Ocean pollution is an important, but insufficiently recognized and inadequately controlled component of global pollution. It poses serious threats to human health and well-being. The nature and magnitude of these impacts are only beginning to be understood.

Goals

(1) Broadly examine the known and potential impacts of ocean pollution on human health. (2) Inform policy makers, government leaders, international organizations, civil society, and the global public of these threats. (3) Propose priorities for interventions to control and prevent pollution of the seas and safeguard human health.

Methods

Topic-focused reviews that examine the effects of ocean pollution on human health, identify gaps in knowledge, project future trends, and offer evidence-based guidance for effective intervention.

Environmental Findings

Pollution of the oceans is widespread, worsening, and in most countries poorly controlled. It is a complex mixture of toxic metals, plastics, manufactured chemicals, petroleum, urban and industrial wastes, pesticides, fertilizers, pharmaceutical chemicals, agricultural runoff, and sewage. More than 80% arises from land-based sources. It reaches the oceans through rivers, runoff, atmospheric deposition and direct discharges. It is often heaviest near the coasts and most highly concentrated along the coasts of low- and middle-income countries. Plastic is a rapidly increasing and highly visible component of ocean pollution, and an estimated 10 million metric tons of plastic waste enter the seas each year. Mercury is the metal pollutant of greatest concern in the oceans; it is released from two main sources - coal combustion and small-scale gold mining. Global spread of industrialized agriculture with increasing use of chemical fertilizer leads to extension of Harmful Algal Blooms (HABs) to previously unaffected regions. Chemical pollutants are ubiquitous and contaminate seas and marine organisms from the high Arctic to the abyssal depths.

Ecosystem Findings

Ocean pollution has multiple negative impacts on marine ecosystems, and these impacts are exacerbated by global climate change. Petroleum-based pollutants reduce photosynthesis in marine microorganisms that generate oxygen. Increasing absorption of carbon dioxide into the seas causes ocean acidification, which destroys coral reefs, impairs shellfish development, dissolves calcium-containing microorganisms at the base of the marine food web, and increases the toxicity of some pollutants. Plastic pollution threatens marine mammals, fish, and seabirds and accumulates in large mid-ocean gyres. It breaks down into microplastic and nanoplastic particles containing multiple manufactured chemicals that can enter the tissues of marine organisms, including species consumed by humans. Industrial releases, runoff, and sewage increase frequency and severity of HABs, bacterial pollution, and anti-microbial resistance. Pollution and sea surface warming are triggering poleward migration of dangerous pathogens such as the Vibrio species. Industrial discharges, pharmaceutical wastes, pesticides, and sewage contribute to global declines in fish stocks.

Human Health Findings

Methylmercury and PCBs are the ocean pollutants whose human health effects are best understood. Exposures of infants in utero to these pollutants through maternal consumption of contaminated seafood can damage developing brains, reduce IQ and increase children's risks for autism, ADHD and learning disorders. Adult exposures to methylmercury increase risks for cardiovascular disease and dementia. Manufactured chemicals - phthalates, bisphenol A, flame retardants, and perfluorinated chemicals, many of them released into the seas from plastic waste - can disrupt endocrine signaling, reduce male fertility, damage the nervous system, and increase risk of cancer. HABs produce potent toxins that accumulate in fish and shellfish. When ingested, these toxins can cause severe neurological impairment and rapid death. HAB toxins can also become airborne and cause respiratory disease. Pathogenic marine bacteria cause gastrointestinal diseases and deep wound infections. With climate change and increasing pollution, risk is high that Vibrio infections, including cholera, will increase in frequency and extend to new areas. All of the health impacts of ocean pollution fall disproportionately on vulnerable populations in the Global South - environmental injustice on a planetary scale.

Conclusions

Ocean pollution is a global problem. It arises from multiple sources and crosses national boundaries. It is the consequence of reckless, shortsighted, and unsustainable exploitation of the earth's resources. It endangers marine ecosystems. It impedes the production of atmospheric oxygen. Its threats to human health are great and growing, but still incompletely understood. Its economic costs are only beginning to be counted.Ocean pollution can be prevented. Like all forms of pollution, ocean pollution can be controlled by deploying data-driven strategies based on law, policy, technology, and enforcement that target priority pollution sources. Many countries have used these tools to control air and water pollution and are now applying them to ocean pollution. Successes achieved to date demonstrate that broader control is feasible. Heavily polluted harbors have been cleaned, estuaries rejuvenated, and coral reefs restored.Prevention of ocean pollution creates many benefits. It boosts economies, increases tourism, helps restore fisheries, and improves human health and well-being. It advances the Sustainable Development Goals (SDG). These benefits will last for centuries.

Recommendations

World leaders who recognize the gravity of ocean pollution, acknowledge its growing dangers, engage civil society and the global public, and take bold, evidence-based action to stop pollution at source will be critical to preventing ocean pollution and safeguarding human health.Prevention of pollution from land-based sources is key. Eliminating coal combustion and banning all uses of mercury will reduce mercury pollution. Bans on single-use plastic and better management of plastic waste reduce plastic pollution. Bans on persistent organic pollutants (POPs) have reduced pollution by PCBs and DDT. Control of industrial discharges, treatment of sewage, and reduced applications of fertilizers have mitigated coastal pollution and are reducing frequency of HABs. National, regional and international marine pollution control programs that are adequately funded and backed by strong enforcement have been shown to be effective. Robust monitoring is essential to track progress.Further interventions that hold great promise include wide-scale transition to renewable fuels; transition to a circular economy that creates little waste and focuses on equity rather than on endless growth; embracing the principles of green chemistry; and building scientific capacity in all countries.Designation of Marine Protected Areas (MPAs) will safeguard critical ecosystems, protect vulnerable fish stocks, and enhance human health and well-being. Creation of MPAs is an important manifestation of national and international commitment to protecting the health of the seas.

The role of gastropod shell composition and microstructure in resisting dissolution caused by ocean acidification

Organisms, such as molluscs, that produce their hard parts from calcium carbonate are expected to show increased difficulties growing and maintaining their skeletons under ocean acidification (OA). Any loss of shell integrity increases vulnerability, as shells provide protection against predation, desiccation, and disease. Not all species show the same responses to OA, which may be due to the composition and microstructural arrangement of their shells. We explore the role of shell composition and microstructure in resisting dissolution caused by decreases in seawater pH using a combination of microCT scans, XRD analysis, and SEM imaging. Two gastropods with different shell compositions and microstructure, Tegula funebralis and Nucella ostrina, were exposed to simulated ocean acidification conditions for six months. Both species showed signs of dissolution on the exterior of their shells, but changes in density were significantly more pronounced in T. funebralis. XRD analysis indicated that the exterior layer of both shell types was made of calcite. T. funebralis may be more prone to dissolution because their outer fibrous calcite layer has more crystal edges and faces exposed, potentially increasing the surface area on which dissolution can occur. These results support a previous study where T. funebralis showed significant decreases in both shell growth and strength, but N. ostrina only showed slight reductions in shell strength, and unaffected growth. We suggest that microstructural arrangement of shell layers in molluscs, more so than their composition alone, is critical for determining the vulnerability of mollusc shells to OA.

Decreased pH impairs sea urchin resistance to predatory fish: A combined laboratory-field study to understand the fate of top-down processes in future oceans

Changing oceans represent a serious threat for a wide range of marine organisms, with severe cascading effects on ecosystems and their services. Sea urchins are particularly sensitive to decreased pH expected for the end of the century and their key ecological role in regulating community structure and functioning could be seriously compromised. An integrated approach of laboratory and field experiments has been implemented to investigate the effects of decreased pH on predator-prey interaction involving sea urchins and their predators. Our results suggest that under future Ocean Acidification scenarios adult sea urchins defence strategies, such as spine length, test robustness and oral plate thickness, could be compromised together with their survival chance to natural predators. Sea urchins represent the critical linkage between top-down and bottom-up processes along Mediterranean rocky reefs, and the cumulative impacts of global and local stressors could lead to a decline producing cascading effects on benthic ecosystems.

Energetic response of Atlantic surfclam Spisula solidissima to ocean acidification

In this study, we assessed the Atlantic surfclam (Spisula solidissima) energy budget under different ocean acidification conditions (OA). During 12 weeks, 126 individuals were maintained at three different ρCO₂ concentrations. Every two weeks, individuals were sampled for physiological measurements and scope for growth (SFG). In the high ρCO₂ treatment, clearance rate decreased and excretion rate increased relative to the low ρCO₂ treatment, resulting in reduced SFG. Moreover, oxygen:nitrogen (O:N) excretion ratio dropped, suggesting that a switch in metabolic strategy occurred. The medium ρCO₂ treatment had no significant effects upon SFG; however, metabolic loss increased, suggesting a rise in energy expenditure. In addition, a significant increase in food selection efficiency was observed in the medium treatment, which could be a compensatory reaction to the metabolic over-costs. Results showed that surfclams are particularly sensitive to OA; however, the different compensatory mechanisms observed indicate that they are capable of some temporary resilience.

Transcriptional changes of Pacific oyster Crassostrea gigas reveal essential role of calcium signal pathway in response to CO2-driven acidification

There is increasing evidence that ocean acidification (OA) has a significant impact on marine organisms. However, the ability of most marine organisms to acclimate to OA and the underlying mechanisms are still not well understood. In the present study, whole transcriptome analysis was performed to compare the impacts of short- (7 days, named as short group) and long- (60 days, named as long group) term CO₂ exposure (pH 7.50) on Pacific oyster Crassostrea gigas. The responses of C. gigas to short- and long-term CO₂ exposure shared common mechanisms in metabolism, membrane-associated transportation and binding processes. Long-term CO₂ exposure induced significant expression of genes involved in DNA or RNA binding, indicating the activated transcription after long-term CO₂ exposure. Oysters in the short-term group underwent significant intracellular calcium variation and oxidative stress. In contrast, the intracellular calcium, ROS level in hemocytes and H₂O₂ in serum recovered to normal levels after long-term CO₂ exposure, suggesting the compensation of physiological status and mutual interplay between calcium and oxidative level. The compensation was supported by the up-regulation of a series of calcium binding proteins (CBPs) and calmodulins (CaMs) related signal pathway. The results provided valuable information to understand the molecular mechanism underlying the responses of Pacific oyster to the acidified ocean and might have implications for predicting the possible effects of global climate changes on oyster aquaculture.

Toxicity of Carbon Dioxide to Freshwater Fishes: Implications for Aquatic Invasive Species Management

Carbon dioxide (CO₂ ) has been approved by the US Environmental Protection Agency as a new aquatic pesticide to control invasive Asian carps and other aquatic nuisance species in the United States. However, limited CO₂ toxicity data could make it challenging for resource managers to characterize the potential risk to nontarget species during CO₂ applications. The present study quantified the toxicity of CO₂ to 2 native riverine fishes, bluegill (Lepomis macrochirus) and fathead minnow (Pimephales promelas), using 12-h continuous flow-through CO₂ exposure at 5, 15, and 25 °C water temperatures. Resulting survival indicated that bluegill (median lethal concentration [LC50] range 91-140 mg/L CO₂ ) were more sensitive to CO₂ than fathead minnow (LC50 range 235-306 mg/L CO₂ ) across all water temperatures. Bluegill were also more sensitive to CO₂ at 5 °C (LC50 91 mg/L CO₂ , 95% CI 85-96 mg/L CO₂ ) than at 25 °C (LC50 140 mg/L CO₂ , 95% CI 135-146 mg/L CO₂ ). Fathead minnow showed an opposite response and were less sensitive at 5 °C (LC50 306 mg/L CO₂ , 95% CI 286-327 mg/L CO₂ ) relative to 25 °C (LC50 235 mg/L CO₂ , 95% CI 224-246 mg/L CO₂ ). Our results show that CO₂ toxicity can differ by species and water temperature. Data from the present study may inform decisions related to the use of CO₂ as a control tool. Environ Toxicol Chem 2020;39:2247-2255. Published 2020. This article is a U.S. government work and is in the public domain in the USA.

Progressive seawater acidification on the Great Barrier Reef continental shelf

Coral reefs are highly sensitive to ocean acidification due to rising atmospheric CO₂ concentrations. We present 10 years of data (2009-2019) on the long-term trends and sources of variation in the carbon chemistry from two fixed stations in the Australian Great Barrier Reef. Data from the subtropical mid-shelf GBRWIS comprised 3-h instrument records, and those from the tropical coastal NRSYON were monthly seawater samples. Both stations recorded significant variation in seawater CO₂ fugacity (fCO₂), attributable to seasonal, daytime, temperature and salinity fluctuations. Superimposed over this variation, fCO₂ progressively increased by > 2.0 ± 0.3 µatm year^-1 at both stations. Seawater temperature and salinity also increased throughout the decade, whereas seawater pH and the saturation state of aragonite declined. The decadal upward fCO₂ trend remained significant in temperature- and salinity-normalised data. Indeed, annual fCO₂ minima are now higher than estimated fCO₂ maxima in the early 1960s, with mean fCO₂ now ~ 28% higher than 60 years ago. Our data indicate that carbonate dissolution from the seafloor is currently unable to buffer the Great Barrier Reef against ocean acidification. This is of great concern for the thousands of coral reefs and other diverse marine ecosystems located in this vast continental shelf system.

A possible link between coral reef success, crustose coralline algae and the evolution of herbivory

Crustose coralline red algae (CCA) play a key role in the consolidation of many modern tropical coral reefs. It is unclear, however, if their function as reef consolidators was equally pronounced in the geological past. Using a comprehensive database on ancient reefs, we show a strong correlation between the presence of CCA and the formation of true coral reefs throughout the last 150 Ma. We investigated if repeated breakdowns in the potential capacity of CCA to spur reef development were associated with sea level, ocean temperature, CO₂ concentration, CCA species diversity, and/or the evolution of major herbivore groups. Model results show that the correlation between the occurrence of CCA and the development of true coral reefs increased with CCA diversity and cooler ocean temperatures while the diversification of herbivores had a transient negative effect. The evolution of novel herbivore groups compromised the interaction between CCA and true reef growth at least three times in the investigated time interval. These crises have been overcome by morphological adaptations of CCA.

The origin and diversification of pteropods precede past perturbations in the Earth's carbon cycle

Pteropods are a group of planktonic gastropods that are widely regarded as biological indicators for assessing the impacts of ocean acidification. Their aragonitic shells are highly sensitive to acute changes in ocean chemistry. However, to gain insight into their potential to adapt to current climate change, we need to accurately reconstruct their evolutionary history and assess their responses to past changes in the Earth's carbon cycle. Here, we resolve the phylogeny and timing of pteropod evolution with a phylogenomic dataset (2,654 genes) incorporating new data for 21 pteropod species and revised fossil evidence. In agreement with traditional taxonomy, we recovered molecular support for a division between "sea butterflies" (Thecosomata; mucus-web feeders) and "sea angels" (Gymnosomata; active predators). Molecular dating demonstrated that these two lineages diverged in the early Cretaceous, and that all main pteropod clades, including shelled, partially-shelled, and unshelled groups, diverged in the mid- to late Cretaceous. Hence, these clades originated prior to and subsequently survived major global change events, including the Paleocene-Eocene Thermal Maximum (PETM), the closest analog to modern-day ocean acidification and warming. Our findings indicate that planktonic aragonitic calcifiers have shown resilience to perturbations in the Earth's carbon cycle over evolutionary timescales.

Inorganic carbon uptake strategies in coralline algae: Plasticity across evolutionary lineages under ocean acidification and warming

Dissolved inorganic carbon (DIC) assimilation is essential to the reef-building capacity of crustose coralline algae (CCA). Little is known, however, about the DIC uptake strategies and their potential plasticity under ongoing ocean acidification (OA) and warming. The persistence of CCA lineages throughout historical oscillations of pCO₂ and temperature suggests that evolutionary history may play a role in selecting for adaptive traits. We evaluated the effects of pCO₂ and temperature on the plasticity of DIC uptake strategies and associated energetic consequences in reef-building CCA from different evolutionary lineages. We simulated past, present, moderate (IPCC RCP 6.0) and high pCO₂ (RCP 8.5) and present and high (RCP 8.5) temperature conditions and quantified stable carbon isotope fractionation (¹³ε), organic carbon content, growth and photochemical efficiency. All investigated CCA species possess CO₂-concentrating mechanisms (CCMs) and assimilate CO₂ via diffusion to varying degrees. Under OA and warming, CCA either increased or maintained CCM capacity, which was associated with overall neutral effects on metabolic performance. More basal taxa, Sporolithales and Hapalidiales, had greater capacity for diffusive CO₂ use than Corallinales. We suggest that CCMs are an adaptation that supports a robust carbon physiology and are likely responsible for the endurance of CCA in historically changing oceans.

The seawater carbon inventory at the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM) (55.6 Mya) was a geologically rapid carbon-release event that is considered the closest natural analog to anthropogenic CO₂ emissions. Recent work has used boron-based proxies in planktic foraminifera to characterize the extent of surface-ocean acidification that occurred during the event. However, seawater acidity alone provides an incomplete constraint on the nature and source of carbon release. Here, we apply previously undescribed culture calibrations for the B/Ca proxy in planktic foraminifera and use them to calculate relative changes in seawater-dissolved inorganic carbon (DIC) concentration, surmising that Pacific surface-ocean DIC increased by [Formula: see text] µmol/kg during the peak-PETM. Making reasonable assumptions for the pre-PETM oceanic DIC inventory, we provide a fully data-driven estimate of the PETM carbon source. Our reconstruction yields a mean source carbon δ¹³C of -10‰ and a mean increase in the oceanic C inventory of +14,900 petagrams of carbon (PgC), pointing to volcanic CO₂ emissions as the main carbon source responsible for PETM warming.

Proxy evidence for state-dependence of climate sensitivity in the Eocene greenhouse

Despite recent advances, the link between the evolution of atmospheric CO2 and climate during the Eocene greenhouse remains uncertain. In particular, modelling studies suggest that in order to achieve the global warmth that characterised the early Eocene, warmer climates must be more sensitive to CO2 forcing than colder climates. Here, we test this assertion in the geological record by combining a new high-resolution boron isotope-based CO2 record with novel estimates of Global Mean Temperature. We find that Equilibrium Climate Sensitivity (ECS) was indeed higher during the warmest intervals of the Eocene, agreeing well with recent model simulations, and declined through the Eocene as global climate cooled. These observations indicate that the canonical IPCC range of ECS (1.5 to 4.5 °C per doubling) is unlikely to be appropriate for high-CO2 warm climates of the past, and the state dependency of ECS may play an increasingly important role in determining the state of future climate as the Earth continues to warm.

Ocean acidification interacts with variable light to decrease growth but increase particulate organic nitrogen production in a diatom

Phytoplankton in the upper oceans are exposed to changing light levels due to mixing, diurnal solar cycles and weather conditions. Consequently, effects of ocean acidification are superimposed upon responses to variable light levels. We therefore grew a model diatom Thalassiosira pseudonana under either constant or variable light but at the same daily photon dose, with current low (400 μatm, LC) and future high CO₂ (1000 μatm, HC) treatments. Variable light, compared with the constant light regime, decreased the growth rate, Chl a, Chl c, and carotenoid contents under both LC and HC conditions. Cells grown under variable light appeared more tolerant of high light as indicated by higher maximum relative electron transport rate and saturation light. Light variation interacted with high CO₂/lowered pH to decrease the carbon fixation rate, but increased particulate organic carbon (POC) and particularly nitrogen (PON) per cell, which drove a decrease in C/N ratio, reflecting changes in the efficiency of energy transfer from photo-chemistry to net biomass production. Our results imply that elevated pCO₂ under varying light conditions can lead to less primary productivity but more PON per biomass of the diatom, which might improve the food quality of diatoms and thereby influence biogeochemical nitrogen cycles.

Amelioration of ocean acidification and warming effects through physiological buffering of a macroalgae

Concurrent anthropogenic global climate change and ocean acidification are expected to have a negative impact on calcifying marine organisms. While knowledge of biological responses of organisms to oceanic stress has emerged from single-species experiments, these do not capture ecologically relevant scenarios where the potential for multi-organism physiological interactions is assessed. Marine algae provide an interesting case study, as their photosynthetic activity elevates pH in the surrounding microenvironment, potentially buffering more acidic conditions for associated epiphytes. We present findings that indicate increased tolerance of an important epiphytic foraminifera, Marginopora vertebralis, to the effects of increased temperature (±3°C) and pCO2 (~1,000 µatm) when associated with its common algal host, Laurencia intricata. Specimens of M. vertebralis were incubated for 15 days in flow-through aquaria simulating current and end-of-century temperature and pH conditions. Physiological measures of growth (change in wet weight), calcification (measured change in total alkalinity in closed bottles), photochemical efficiency (Fv/Fm), total chlorophyll, photosynthesis (oxygen flux), and respiration were determined. When incubated in isolation, M. vertebralis exhibited reduced growth in end-of-century projections of ocean acidification conditions, while calcification rates were lowest in the high-temperature, low-pH treatment. Interestingly, association with L. intricata ameliorated these stress effects with the growth and calcification rates of M. vertebralis being similar to those observed in ambient conditions. Total chlorophyll levels in M. vertebralis decreased when in association with L. intricata, while maximum photochemical efficiency increased in ambient conditions. Net production estimates remained similar between M. vertebralis in isolation and in association with L. intricata, although both production and respiration rates of M. vertebralis were significantly higher when associated with L. intricata. These results indicate that the association with L. intricata increases the resilience of M. vertebralis to climate change stress, providing one of the first examples of physiological buffering by a marine alga that can ameliorate the negative effects of changing ocean conditions.

Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation

Crustose coralline algae (CCA) are vital to coral reefs worldwide, providing structural integrity and inducing the settlement of important invertebrate larvae. CCA are known to be impacted by changes in their environment, both during early development and adulthood. However, long-term studies on either life history stage are lacking in the literature, therefore not allowing time to explore the acclimatory or potential adaptive responses of CCA to future global change scenarios. Here, we exposed a widely distributed, slow growing, species of CCA, Sporolithon cf. durum, to elevated temperature and pCO2 for five months and their first set of offspring (F1) for eleven weeks. Survival, reproductive output, and metabolic rate were measured in adult S. cf. durum, and survival and growth were measured in the F1 generation. Adult S. cf. durum experienced 0% mortality across treatments and reduced their O2 production after five months exposure to global stressors, indicating a possible expression of plasticity. In contrast, the combined stressors of elevated temperature and pCO2 resulted in 50% higher mortality and 61% lower growth on germlings. On the other hand, under the independent elevated pCO2 treatment, germling growth was higher than all other treatments. These results show the robustness and plasticity of S. cf. durum adults, indicating the potential for them to acclimate to increased temperature and pCO2. However, the germlings of this species are highly sensitive to global stressors and this could negatively impact this species in future oceans, and ultimately the structure and stability of coral reefs.

Effects of pH and nitrogen form on Nitzschia closterium growth by linking dynamic with enzyme activity

In this study, Nitzschia closterium was incubated in seawater at different pH values (8.10, 7.71, and 7.45) and using different nitrogen forms (NO₃-N and NH₄-N) in the laboratory. The results showed that the growth of N. closterium was inhibited by ocean acidification, with individuals under lower pH levels showing lower growth rates and lower nitrogen uptake rates for both nitrogen forms. The V_max/K_s ratio decreased with decreasing pH, indicating the inhibition of nitrogen uptake, whereas the ratios for NH₄-N cultures were higher than those for NO₃-N cultures, implying the highly competitive position of NH₄-N. Acidification might induce reactive oxygen species based on the result that the maximum enzyme activities of SuperOxide Dismutase (SOD) and CATalase (CAT) increased under lower pH levels. The SOD and CAT activities for the NO₃-N cultures were higher than those for NH₄-N cultures at the low pH level, indicating that acidification might cause more oxidative stress for NO₃-N cultures than for NH₄-N cultures. Thus, ocean acidification might have a more detrimental effect on the growth of N. closterium under NO₃-N conditions than NH₄-N conditions, with a lower ratio (γ) of the maximum growth rate to the maximum nutrient uptake rate, and a drop in nitrate reductase activity under lower pH levels.

Development Trends and Frontiers of Ocean Big Data Research Based on CiteSpace

Modern socio-economic development and climate prediction depend greatly on the application of ocean big data. With the accelerated development of ocean observation methods and the continuous improvement of the big data science, the challenges of multiple data sources and data diversity have emerged in the ocean field. As a result, the current data magnitude has reached the terabyte scale. Currently, the traditional theoretical foundation and technical methods have their inherent limitations and demerits that cannot satisfied the temporal and spatial attributes of the current ocean big data. Numerous scholars and countries were involved in ocean big data research. To explore the focus and current status, and determine the topics of research on bursts and acquisition of trend related to ocean big data, 400 articles between 1990 and 2019 were collected from the “Web of Science.” Combined with visualization software CiteSpace, bibliometrics method and literature combing technology, the pivotal literature related to ocean big data, including significant level countries, institutions, authors, journals and keywords were recognized. A synthetical analysis has revealed research hot spots and research frontiers. The purpose of this study is to provide researchers and practitioners in the field of ocean big data with the main research domains and research hotspots, and orientation for further research.

The impacts of ocean acidification on marine trace gases and the implications for atmospheric chemistry and climate

Surface ocean biogeochemistry and photochemistry regulate ocean-atmosphere fluxes of trace gases critical for Earth's atmospheric chemistry and climate. The oceanic processes governing these fluxes are often sensitive to the changes in ocean pH (or pCO2) accompanying ocean acidification (OA), with potential for future climate feedbacks. Here, we review current understanding (from observational, experimental and model studies) on the impact of OA on marine sources of key climate-active trace gases, including dimethyl sulfide (DMS), nitrous oxide (N2O), ammonia and halocarbons. We focus on DMS, for which available information is considerably greater than for other trace gases. We highlight OA-sensitive regions such as polar oceans and upwelling systems, and discuss the combined effect of multiple climate stressors (ocean warming and deoxygenation) on trace gas fluxes. To unravel the biological mechanisms responsible for trace gas production, and to detect adaptation, we propose combining process rate measurements of trace gases with longer term experiments using both model organisms in the laboratory and natural planktonic communities in the field. Future ocean observations of trace gases should be routinely accompanied by measurements of two components of the carbonate system to improve our understanding of how in situ carbonate chemistry influences trace gas production. Together, this will lead to improvements in current process model capabilities and more reliable predictions of future global marine trace gas fluxes.

Common Caribbean corals exhibit highly variable responses to future acidification and warming

We conducted a 93-day experiment investigating the independent and combined effects of acidification (280-3300 µatm pCO₂) and warming (28°C and 31°C) on calcification and linear extension rates of four key Caribbean coral species ( Siderastrea siderea, Pseudodiploria strigosa, Porites astreoides, Undaria tenuifolia) from inshore and offshore reefs on the Belize Mesoamerican Barrier Reef System. All species exhibited nonlinear declines in calcification rate with increasing pCO₂. Warming only reduced calcification in Ps. strigosa. Of the species tested, only S. siderea maintained positive calcification in the aragonite-undersaturated treatment . Temperature and pCO₂ had no effect on the linear extension of S. siderea and Po. astreoides, and natal reef environment did not impact any parameter examined. Results suggest that S. siderea is the most resilient of these corals to warming and acidification owing to its ability to maintain positive calcification in all treatments, Ps. strigosa and U. tenuifolia are the least resilient, and Po. astreoides falls in the middle. These results highlight the diversity of calcification responses of Caribbean corals to projected global change.

Have decades of abiotic studies in sediments been misinterpreted?

Sterilization techniques are largely employed to distinguish biotic and abiotic processes in biogeochemical studies as they inhibit microbial activity. Since one century, chemical sterilizers, supposed to preserve original environmental samples, have taken precedence over physical sterilization techniques considered too destructive. Sodium azide (NaN₃) is nowadays the most commonly used inorganic chemical sterilizer. It is sufficiently purified to study trace metals, as well. Nevertheless, its (in)activity in physico-chemical processes was never ascertained. Through the investigation of sediment resuspension in seawater, the present work unequivocally demonstrated that NaN₃ can impact carbon and trace metals' transfers by altering the redox balance and pH. Unlike decades of blind practice, NaN₃ should be used with great care to track abiotic processes from organic matter rich and reductive matrices.

Two-step extinction of Late Cretaceous marine vertebrates in northern Gulf of Mexico prolonged biodiversity loss prior to the Chicxulub impact

Recent studies on mass extinctions are often based on the global fossil record, but data from selected paleogeographic regions under a relatively constant paleoenvironmental setting can also provide important information. Eighty-nine marine vertebrate species, including cartilaginous and bony fish and marine reptiles, from northern Gulf of Mexico – located about 500 km from the Chicxulub crater – offer a unique opportunity to determine an extinction process during the last 20 million years of the Late Cretaceous. Our diversity data show two separate extinction events: (i) the ‘Middle Campanian Crisis’ (about 77 Mya) and (ii) the end-Maastrichtian (66 Mya) events. Whether this stepwise pattern of extinctions occurred locally or globally cannot be determined at present due to the lack of a dataset of the marine vertebrate record for reliable comparison. However, this stepwise pattern including the Middle Campanian and end-Maastrichtian events for, at least, a 13 million-year interval indicates long-term global marine environmental changes (e.g., regression, ocean water chemistry change). Because most Cretaceous marine vertebrates already disappeared in the Gulf of Mexico prior to the latest Maastrichtian, the Chicxulub Impact may not be considered as the most devastating extinction event for the community.

Evolutionary Traits that Enable Scleractinian Corals to Survive Mass Extinction Events

Scleractinian “stony” corals are major habitat engineers, whose skeletons form the framework for the highly diverse, yet increasingly threatened, coral reef ecosystem. Fossil coral skeletons also present a rich record that enables paleontological analysis of coral origins, tracing them back to the Triassic (~241 Myr). While numerous invertebrate lineages were eradicated at the last major mass extinction boundary, the Cretaceous-Tertiary/K-T (66 Myr), a number of Scleractinian corals survived. We review this history and assess traits correlated with K-T mass extinction survival. Disaster-related “survival” traits that emerged from our analysis are: (1) deep water residing (>100 m); (2) cosmopolitan distributions, (3) non-symbiotic, (4) solitary or small colonies and (5) bleaching-resistant. We then compared these traits to the traits of modern Scleractinian corals, using to IUCN Red List data, and report that corals with these same survival traits have relatively stable populations, while those lacking them are presently decreasing in abundance and diversity. This shows corals exhibiting a similar dynamic survival response as seen at the last major extinction, the K-T. While these results could be seen as promising, that some corals may survive the Anthropocene extinction, they also highlight how our relatively-fragile Primate order does not possess analogous “survival” characteristics, nor have a record of mass extinction survival as some corals are capable.

Resilience of marine invertebrate communities during the early Cenozoic hyperthermals

The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated.

Hierarchical micro/nanoporous ion-exchangeable sponge

Inspired by the versatile properties of a sponge, we propose an ion-exchangeable sponge composed of hierarchical micropores and nanopores for water treatment. Sodium ions in brackish water (10-300 mM) absorbed in the sponge were exchanged for hydrogen ions in a short incubation time and the desalted water was released by squeezing the sponge with a single hand grip. This simple desalination process was attributed to the multi-scale porous structures in the sponge. A number of nanoporous thin films were formed like bubbles surrounded by the closed backbone of the microporous sponge. The hierarchical micro/nanopores maximized the contact area of the ion-exchanging surface with the saline solution so that scaled-up desalination was achieved. Furthermore, the growth of wheat shoots in the desalted water was demonstrated in vivo after using this micro/nanofluidic based water-treatment with the sponges. Wheat shoots grown in NaHCO₃/Na₂CO₃ solutions treated by the sponges were 110 to 226.45% longer than those grown in the original salty water. This implies that the ion-exchangeable sponge could serve as an appropriate technology for the treatment of ground water affected by acid rain and weathered alkaline rocks.

Ocean Carbon Storage across the middle Miocene: a new interpretation for the Monterey Event

The Miocene Climatic Optimum (MCO, 14-17 Ma) was ~3-4 °C warmer than present, similar to estimates for 2100. Coincident with the MCO is the Monterey positive carbon isotope (δ13C) excursion, with oceans more depleted in 12C relative to 13C than any time in the past 50 Myrs. The long-standing Monterey Hypothesis uses this excursion to invoke massive marine organic carbon burial and draw-down of atmospheric CO2 as a cause for the subsequent Miocene Climate Transition and Antarctic glaciation. However, this hypothesis cannot explain the multi-Myr lag between the δ13C excursion and global cooling. We use planktic foraminiferal B/Ca, δ11B, δ13C, and Mg/Ca to reconstruct surface ocean carbonate chemistry and temperature. We propose that the MCO was associated with elevated oceanic dissolved inorganic carbon caused by volcanic degassing, global warming, and sea-level rise. A key negative feedback of this warm climate was the organic carbon burial on drowned continental shelves.