Coastal acidification alters estuarine sediment nitrous oxide and methane fluxes

Published 2 June 2023 Science Leave a Comment
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Abstract

The impact of coastal acidification on sediment nitrous oxide (N2O) and methane (CH4) fluxes is largely unknown. We exposed temperate estuarine sediments to moderate (pH 7.3) and extreme (pH 6.3) acidification. Sediments were collected from two sites—one exposed to high and the other to low nitrogen loading. We demonstrate that low pH has a strong effect on greenhouse gas fluxes. The response, in terms of both magnitude and direction, was site specific. Sediments from the high nitrogen loading site exhibited increased N2O fluxes and decreased CH4 fluxes under moderate and extreme acidification. In contrast, sediments from the low nitrogen loading site exhibited decreased N2O fluxes under moderate and extreme acidification while CH4 fluxes both decreased (moderate) and increased (extreme). This study highlights the dynamic response of sediment N2O and CH4 fluxes to low pH and emphasizes the need for deeper understanding of ofcoastal acidification impacts on sediment biogeochemistry.

Scientific Significance Statement

Estuaries are increasingly exposed to low pH conditions (i.e., coastal acidification) largely driven by rising temperatures, increased precipitation, and excess nutrient loading. The impact of coastal acidification on sediment biogeochemical processes, including those responsible for the production or consumption of greenhouse gases (GHGs) are largely unknown. Here, we show that sediment fluxes of two powerful GHGs (nitrous oxide: N2O and methane: CH4) respond rapidly to low pH conditions. In addition, the magnitude and direction of this response varies within an estuary, even at sites with similar pH exposure histories. Overall, this study highlights the need to incorporate current and future pH conditions in forecasting models and in the development of coastal GHG budgets.

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Differential roles of anthropogenic CO2 in mediating seasonal amplitudes of ocean acidification metrics over a coastal coral habitat

Published 2 June 2023 Science Leave a Comment
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Seasonal-scale local forcings sharply reduce the coastal pH and aragonite saturation state (Ωaragonite). However, habitat-specific seasonality and control change signatures under increasing atmospheric CO2 are still poorly characterized. Here, we investigated carbonate system parameter dynamics over a Dongshan coral habitat that is greatly influenced by seasonal current patterns on the western Taiwan Strait coast. Specifically, relatively low pH and Ωaragonite were observed in the trial zone throughout the seasons. Using a first-order Taylor decomposition considering biological carbon metabolism, we suggest that the higher net aerobic respiration related to intense local human activities produced worse ocean acidity in the trial zone. Seasonally, a decreasing Ωaragonite trend was observed from the transition to the northeast monsoon seasons, mainly controlled by dissolved inorganic carbon (DIC) divergence among seasons. The pH/hydrogen ion concentration ([H+]) seasonal cycle was determined by both DIC and temperature components, revealing the lowest/highest value in the southwest monsoon season. Based on ocean acidification scenario modeling forced with a business-as-usual emissions scenario, the Ωaragonite seasonal amplitude attenuation was projected to exceed 30% during the 21st century. However, [H+] seasonal amplitude was amplified over 170%. The attenuation in the Ωaragonite seasonal amplitude mainly resulted from an increase in anthropogenic CO2 seasonal divergence. The increase in [H+] seasonal amplitude mostly followed from an increase in the [H+] sensitivities to DIC and temperature changes.

Continue reading ‘Differential roles of anthropogenic CO2 in mediating seasonal amplitudes of ocean acidification metrics over a coastal coral habitat’

Effects of anthropogenic stressorson Helgoland’s lobsters(Homarus gammarus)

Published 2 June 2023 Science Leave a Comment
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As meroplankton, lobsters make up a great portion of both benthic communities and planktonic fauna in the water column. Furthermore, they represent a mayor food source across the marine food web and a vital source of protein for humans. As an economically important species, lobsters are highly susceptible to anthropogenic stressors (e.g habitat destruction, over-fishing, noise pollution). Moreover, climate change may magnify the impact of human activities on lobsters’ fitness. The collapse of the population of European lobster (Homarus gammarus) around Helgoland constitutes a good example and prompted a largescale restocking program. Yet, the question arises if recruitment of remaining natural individuals and program released specimens could be stunted by ongoing climate change and human activities.

In my thesis I investigate the effect of several anthropogenic stressors that could potentially be affecting the route to recovery of Helgoland’s lobsters.

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Owing to the difficulties in catching lobster larvae in the field, I used larvae from lobster-rearing facilities to study the effects of anthropogenic stress on larval development and physiology. Studies on the effects of climate change on European lobster larvae have mostly focused on the isolated effect of ocean acidification or warming. Acidification treatments were based on two shared socio-economic pathways emitted by the Intergovernmental Panel on Climate Change (IPCC) regarding the amount of atmospheric CO2 for the end of the century. This study is the first to provide a more complete picture of the thermal limits at different levels of biological organization of lobster larvae under acidification by including a ten-level temperature gradient setup (13-24°C) The results show temperature was positively correlated with growth and energy metabolism; while, pCO2 had a negative impact on survival and morphology. Thus, climate change could potentially stunt the European lobster restocking efforts taking place on the island.

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Mitigating climate change through restoration of coastal ecosystems

Published 2 June 2023 Press releases Leave a Comment

Summary: Researchers are proposing a novel pathway through which coastal ecosystem restoration can permanently capture carbon dioxide from the atmosphere. Seagrass and mangroves — known as blue carbon ecosystems — naturally capture carbon through photosynthesis, which converts carbon dioxide into living tissue.

One of the primary drivers of climate change is excess greenhouse gases like carbon dioxide in the atmosphere. Mitigating climate change in the coming century will require both decarbonization — electrifying the power grid or reducing fossil fuel-guzzling transportation — and removing already existing carbon dioxide from the atmosphere, a process called carbon dioxide removal.

Researchers at the Georgia Institute of Technology and Yale University are proposing a novel pathway through which coastal ecosystem restoration can permanently capture carbon dioxide from the atmosphere. Seagrass and mangroves — known as blue carbon ecosystems — naturally capture carbon through photosynthesis, which converts carbon dioxide into living tissue.

“Mangroves and seagrasses extract carbon dioxide from the atmosphere all day long and turn it into biomass,” said Chris Reinhard, an associate professor in the School of Earth and Atmospheric Sciences (EAS). “Some of this biomass can get buried in sediments, and if it stays there, then you’ve basically just removed carbon dioxide from the atmosphere.”

Restoring these ecosystems could potentially benefit local flora and fauna and help to energize coastal economies. But Reinhard and colleagues now suggest that restoring them could also remove additional carbon through a novel pathway while combating increasing acidity in the ocean.

In May, they presented their research in “Ocean Alkalinity Enhancement Through Restoration of Blue Carbon Ecosystems” in Nature Sustainability.

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Microbe, climate change and marine environment: linking trends and research hotspots

Published 1 June 2023 Science Leave a Comment
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Microbes, or microorganisms, have been the foundation of the biosphere for over 3 billion years and have played an essential role in shaping our planet. The available knowledge on the topic of microbes associated with climate change has the potential to reshape upcoming research trends globally. As climate change impacts the ocean or marine ecosystem, the responses of these “unseen life” will heavily influence the achievement of a sustainable evolutionary environment. The present study aims to identify microbial-related research under changing climate within the marine environment through the mapping of visualized graphs of the available literature. We used scientometric methods to retrieve documents from the Web of Science platform in the Core Collection (WOSCC) database, analyzing a total of 2767 documents based on scientometric indicators. Our findings show that this research area is growing exponentially, with the most influential keywords being “microbial diversity,” “bacteria,” and “ocean acidification,” and the most cited being “microorganism” and “diversity.” The identification of influential clusters in the field of marine science provides insight into the hot spots and frontiers of research in this area. Prominent clusters include “coral microbiome,” “hypoxic zone,” “novel Thermoplasmatota clade,” “marine dinoflagellate bloom,” and “human health.” Analyzing emerging trends and transformative changes in this field can inform the creation of special issues or research topics in selected journals, thus increasing visibility and engagement among the scientific community.

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The Paleocene-Eocene transition in the Gulf of Guinea: evidence of the Petm in the Douala Basin, Cameroon

Published 1 June 2023 Science Leave a Comment
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The Paleocene-Eocene Thermal Maximum (PETM) was identified for the first time in two sections (Bongue and Dibamba) from the Douala sub-basin located in the Gulf of Guinea, Cameroon. This discovery was based on a multi-disciplinary approach including benthic and planktic foraminifera, ostracods, major and trace elements, mercury, carbon stable isotope (δ13C values), total organic carbon (TOC), whole-rock and clay mineralogy. A combination of lithology, microfossil assemblage, and carbon isotope data indicate zone P5 and the top of the Paleocene enabling the definition of the Paleocene-Eocene boundary (PEB). A negative carbon-isotope excursion (CIE) spanning from the uppermost Paleocene deposits to the earliest Eocene sediments (PETM interval) shows a shift in δ13Corg values of 1.5 ‰ in Bongue and 3.0 ‰ in Dibamba. In both sections, this interval is affected by widespread acidification, as revealed by carbonate dissolution and microfossil preservation (i.e., species are dwarfed, broken, thin shelled, and with holes). The very low carbonate content and the scarcity of microfauna indicate the severity of acidification during the PETM, especially in the early Eocene where only one species was identified (Igorina broedermanni). Mercury anomalies, TOC contents, and trace element concentration ratios, point to volcanic activity linked to the Cameroon Volcanic Line (CVL) intrusive magma, and a decrease in productivity prior to the PETM. In addition to climate change, our geochemical and mineralogical data support the hypothesis that other environmental perturbations such as an increase in productivity and detrital input, as well as a decrease in bottom water oxygenation occurred during the PETM in the Douala sub-basin.

Continue reading ‘The Paleocene-Eocene transition in the Gulf of Guinea: evidence of the Petm in the Douala Basin, Cameroon’

Ocean alkalinity enhancement through restoration of blue carbon ecosystems

Published 1 June 2023 Science Leave a Comment
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Blue carbon ecosystems provide a wide range of ecosystem services, are critical for maintaining marine biodiversity and may potentially serve as sites of economically viable carbon dioxide removal through enhanced organic carbon storage. Here we use biogeochemical simulations to show that restoration of these marine ecosystems can also lead to permanent carbon dioxide removal by driving ocean alkalinity enhancement and atmosphere-to-ocean CO2 fluxes. Most notably, our findings suggest that restoring mangroves, which are common in tropical shallow marine settings, will lead to notable local ocean alkalinity enhancement across a wide range of scenarios. Enhanced alkalinity production is linked to increased rates of anaerobic respiration and to increased dissolution of calcium carbonate within sediments. This work provides further motivation to pursue feasible blue carbon restoration projects and a basis for incorporating inorganic carbon removal in regulatory and economic incentivization of blue carbon ecosystem restoration.

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Novel in-situ pH measurement method for high-temperature hydrothermal systems

Published 1 June 2023 Press releases Leave a Comment

Alkaline hydrothermal systems are considered ideal environments for the origin of life because they can provide ideal ion gradient conditions for the formation of early life on Earth.

However, alkaline hydrothermal vents have only been found in the Lost City hydrothermal field in the Atlantic Ocean. Additionally, accurately obtaining the in-situ pH of high-temperature hydrothermal vent fluids is a challenge.

Recently, a research team led by Prof. Zhang Xin from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) and their collaborators from the University of Science and Technology Beijing constructed an in-situ pH measurement method for high-temperature hydrothermal fluids based on the self-developed Raman insertion Probe (RiP) system.

They applied it to the measurement of arc-back arc (ABA) hydrothermal systems and revealed that the in-situ pH of high-temperature fluids in the sediment-host hydrothermal systems is alkaline. The study was published in Geophysical Research Letters on May 10.

The researchers used a deep-sea extreme environment simulation platform to conduct quantitative analysis of the H2S-HS– ion equilibrium system. They established Raman quantitative analysis models for H2S and HS– under high-temperature and high-pressure conditions, as well as an in-situ pH calibration model for hydrothermal fluids.

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Ocean acidification increases copper accumulation and exacerbates copper toxicity in Amphioctopus fangsiao (Mollusca: Cephalopoda): a potential threat to seafood safety

Published 31 May 2023 Science Leave a Comment
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Highlights

  • A. fangsiao can adapt well to ocean acidification after 21-days experiment.
  • Copper accumulation in tissues showed increase in acidified seawater.
  • Copper exposure can influence the growth and feeding of A. fangsiao.
  • Acidification exacerbated the copper effect in metabolism and oxidative stress.
  • Copper exposure triggered DNA and protein and mitochondrial damage.

Abstract

Ocean acidification (OA) and trace metal pollutants coexist to exert combined effects on the functions and services of marine ecosystems. Increasing atmospheric carbon dioxide has caused a decrease in the pH of the ocean, affecting the bioavailability and speciation of trace metals and consequently altering metal toxicity in marine organisms. As an important trace metal functioned in hemocyanin, the richness of Copper (Cu) in octopuses is remarkable. Therefore, the biomagnification and bioaccumulation capacities of Cu in octopuses may be a non-negligible risk of contamination. Here, Amphioctopus fangsiao was continuously exposed to acidified seawater (pH 7.8) and copper (50 μg/L) to investigate the combined effect of ocean acidification and Cu exposure on marine mollusks. Our results showed that A. fangsiao could adapt well to ocean acidification after 21 days of the rearing experiment. However, the accumulation of Cu in A. fangsiao intestine increased significantly in acidified seawater under high levels of Cu stress. In addition, Cu exposure can influence the physiological function of A. fangsiao, including growth and feeding. This study also demonstrated that Cu exposure disturbed glucolipid metabolism and induced oxidative damage to intestine tissue, and ocean acidification further exacerbated these toxic effects. The obvious histological damage and microbiota alterations were also caused by Cu stress and its combined effect with ocean acidification. At the transcription level, we found numerous differentially expressed genes (DEGs) and significantly enriched KEGG pathways, involving glycolipid metabolism, transmembrane transport, glucolipid metabolism, oxidative stress, mitochondrial, protein and DNA damage, all revealing the strong toxicological synergetic effect of Cu and OA exposure and the molecular adaptation mechanism of A. fangsiao. Collectively, this study demonstrated that octopuses may withstand future ocean acidification conditions, however, the complex interactions of future OA and trace metal pollution need to be emphasized. OA can influence the toxicity of trace metals, inducing a potential threat to marine organism safety.

Continue reading ‘Ocean acidification increases copper accumulation and exacerbates copper toxicity in Amphioctopus fangsiao (Mollusca: Cephalopoda): a potential threat to seafood safety’

Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata

Published 31 May 2023 Science Leave a Comment
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Ocean acidification (OA) and warming (OW) are major global threats to coral reef ecosystems; however, studies on their combined effects (OA + OW) are scarce. Therefore, we evaluated the effects of OA, OW, and OA + OW in the branching reef corals Acropora digitifera and Montipora digitata, which have been found to respond differently to environmental changes. Our results indicate that OW has a greater impact on A. digitifera and M. digitata than OA and that the former species is more vulnerable to OW than the latter. OW was the main stressor for increased mortality and decreased calcification in the OA + OW group, and the effect of OA + OW was additive in both species. Our findings suggest that the relative abundance and cover of M. digitata are expected to increase whereas those of A. digitifera may decrease in the near future in Okinawa.

Continue reading ‘Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata’

Direct H2S, HS− and pH measurements of high-temperature hydrothermal vent fluids with in situ Raman spectroscopy

Published 31 May 2023 Science Leave a Comment
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Abstract

Hydrothermal H2S is an important energy source for hydrothermal ecosystems. However, it is difficult to obtain accurate hydrogen sulfide concentrations in high-temperature hydrothermal fluids because they are highly susceptible to oxidation and compositional variability with mixing. In this study, a new in situ approach for measuring H2S, HS− and pH in hydrothermal fluids was developed and applied to the detections of Okinawa Trough hydrothermal activities. The in situ total H2S concentrations in the Jade and Biwako fluids were determined to be 31.4 and 76.7 mmol/kg, respectively. The in situ measured pH of the Jade fluids was determined to be 6.3, which has exceeded that of a neutral fluid at a specific temperature and pressure, indicating that the pH of Jade fluids is weakly alkaline. The pH transition of hydrothermal fluids from alkaline to acidic may be attributed to the thermal decomposition of organic matter and sulfide precipitation.

Key Points

  • The first in situ measured pH of high-temperature hydrothermal vent fluids at arc-back arc basins was reported
  • A new approach to obtain in situ H2S/HS− concentration and in situ pH of high temperature hydrothermal vent fluids was established
  • The pH transition of hydrothermal fluids from alkaline to acidic should attributes to the precipitation of sulfide minerals
Continue reading ‘Direct H2S, HS− and pH measurements of high-temperature hydrothermal vent fluids with in situ Raman spectroscopy’

Behavioral and physiological effects of ocean acidification and warming on larvae of a continental shelf bivalve

Published 30 May 2023 Science Leave a Comment
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Highlights

  • Warming and acidification impacts on surfclam larvae were investigated.
  • Warming increased larvae feeding, scope for growth and biomineralization.
  • Warming decreased swimming speed and pelagic larval duration.
  • Acidification increased respiration but reduced immunity and biomineralization.

Abstract

The negative impacts of ocean warming and acidification on bivalve fisheries are well documented but few studies investigate parameters relevant to energy budgets and larval dispersal. This study used laboratory experiments to assess developmental, physiological and behavioral responses to projected climate change scenarios using larval Atlantic surfclams Spisula solidissima solidissima, found in northwest Atlantic Ocean continental shelf waters. Ocean warming increased feeding, scope for growth, and biomineralization, but decreased swimming speed and pelagic larval duration. Ocean acidification increased respiration but reduced immune performance and biomineralization. Growth increased under ocean warming only, but decreased under combined ocean warming and acidification. These results suggest that ocean warming increases metabolic activity and affects larval behavior, while ocean acidification negatively impacts development and physiology. Additionally, principal component analysis demonstrated that growth and biomineralization showed similar response profiles, but inverse response profiles to respiration and swimming speed, suggesting alterations in energy allocation under climate change.

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Technical note: Enhancement of float-pH data quality control methods: a study case in the Subpolar Northwestern Atlantic region

Published 30 May 2023 Science Leave a Comment
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Since a pH sensor has become available that is suitable for this demanding autonomous measurement platform, the marine CO2 system can be observed independently and continuously by BGC-Argo floats. This opens the possibility to detect variability and long-term changes in interior ocean inorganic carbon storage and quantify the ocean sink for atmospheric CO2. In combination with a second parameter of the marine CO2 system, pH can be a useful tool to derive the surface ocean CO2 partial pressure (pCO2).

The large spatiotemporal variability of the marine CO2 system requires sustained observations to decipher trends and punctual events (e.g., river discharge, phytoplankton bloom) but also puts a high emphasis on the quality control of float-based pH measurements. In consequence, as the interpretation of changes depends on accurate data, and because sensor offsets or drifts might appear, a consistent and rigorous correction procedure to process and quality-control the data has been established. By applying standardized routines of the Ago data management to pH measurements from a pH/O2 float pilot array in the subpolar North Atlantic Ocean, we investigate the uncertainties and lack of objective criteria associated with the standardized routines, notably the choice of the reference method for the pH correction (CANYON-B or LIRPH) as well the reference depth for this correction. For the studied float array, significant differences of ca. 0.02 pH units are observed between the two reference methods which can be used to correct float-pH data from water samples. Through comparison against discrete pH data from water samples, an assessment of the adjusted float-pH data quality is presented. The results point out noticeable discrepancies near the surface of > 0.01 pH units. In the context of converting surface ocean pH measurements into pCO2 data for the purpose to derive air-sea CO2 fluxes, we conclude that the minimum accuracy requirement of 0.01 pH units (equivalent to the minimum pCO2 accuracy of 10 µatm for potential future inclusion into the SOCAT database) is not systematically achieved in the upper ocean.

While the limited dataset and regional focus of our study provides only one showcase, it still calls for an additional independent pH reference in the surface ocean. We therefore propose a way forward to enhance the float-pH quality control procedure. In our analysis, the current philosophy of pH data correction against climatological reference data at one single depth in the deep ocean appears insufficient to assure adequate data quality in the surface ocean. Ideally, an additional reference point should be taken at or near the surface where the resulting pCO2 data are of the highest importance to monitor the air-sea exchange of CO2 and would have the potential to very significantly augment the impact of the current observation network.

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Increasing atmospheric CO2 enhances the carbon uptake of the coastal ocean

Published 30 May 2023 Science Leave a Comment
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Observational reconstructions indicate a contemporary increase in coastal ocean CO2 uptake. However, the mechanisms and their relative importance in driving this globally intensifying absorption remain unclear. Here we integrate coastal carbon dynamics in a global model via regional grid refinement and enhanced process representation. We find that the increasing coastal ocean CO2 uptake is primarily driven by the upper ocean-atmosphere equilibration lag (41%), followed by climate-induced changes in the circulation (36%) and increasing riverine nutrient loads (23%). The comparatively weak riverine impact is mediated by enhanced advective export of organic carbon across the shelf break, thereby further adding to the carbon enrichment of the open ocean. The contribution of biological carbon fixation increases as the coastal ocean capacity to hold CO2 decreases under continuous climate change and ocean acidification. Our seamless coastal ocean integration advances carbon cycle model realism, which is relevant for addressing impacts of climate change mitigation efforts.

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Assessing the gender-based perception of climate change and ocean acidification of coastal artisanal fishing communities in Liberia

Published 30 May 2023 Media coverage Leave a Comment

The research was separated into three phases: (1) designing the survey, (2) conducting surveys and focus group discussions in the field, and (3) continually analyzing the data.

With the assistance of Dr. Patrizia Ziveri, our Pier2Peer mentor, we partnered with Dr. Victoria Reyes from the Universitat Autonoma de Barcelona (UAB) and the Comanagement Association (CMA) in Robertsport to plan interviews and group discussions involving female fishers and traders. This project utilized a research protocol based on the LICCI project https://doi.org/10.1371/journal.pone.0279847.

Examining the involvement of women in fisheries will offer comprehensive insights into geolocalized community-based data concerning climate change and ocean acidification effects and resilience. This research study aims to investigate how local knowledge can assist in climate and ocean acidification research, enhance our comprehension of the perceived impacts of climate change and ocean acidification, and incorporate local knowledge into policymaking. The project will document and communicate climate change, and ocean acidification impacts at the local level, capturing how small-scale fisheries (SSF) have adapted to these impacts.

The study aims to pinpoint locally perceived species abundance, temporality, location, and size and evaluate how the fishing community has responded to these changes.

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Workshop on Ocean Change and Blue Carbon

Published 26 May 2023 Courses and training Leave a Comment

Dates: 28 August–8 September 2023

Location: IAEA Marine Environment Laboratories, Monaco

Deadline for receipt of applications from the nominating national authority: 26 June 2023

Introduction

The Workshop on Ocean Change and Blue Carbon will provide participants with the foundations to carry out research on the capacity of coastal vegetated ecosystems (i.e. mangroves, seagrasses and saltmarshes) to sequester carbon.

Objectives

Coastal vegetated ecosystems such as mangrove forests, seagrass meadows and tidal marshes sequester large amounts of carbon in their sediment and are identified as both i) key players in the carbon cycle and ii) potentially important as a nature-based solution to climate change (Blue Carbon). This is an addition to the many other relevant ecosystem services they provide, such as nutrient cycling, support of fisheries and biodiversity and coastal protection.

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The aim of this course is to train early-career scientists interested on working on Blue Carbon with the key concepts involved when planning a research study, including designing and conducting the field work, preparation of the samples, carrying out the required analyses, and interpreting and scaling up the results. This will be accompanied by critical reflections on the challenges and open questions to promote discussion and advances on the subject.

Target Audience

The course is open to 10 trainees. Priority will be given to early-career scientists with experience in marine sciences. Scientific publications in related fields will be valued.

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Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico

Published 26 May 2023 Science Leave a Comment
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Ocean acidification is expected to negatively affect many ecologically important organisms. Here we explored the response of Caribbean benthic foraminiferal assemblages to naturally discharging low-pH waters similar to expected future projections for the end of the 21st century. At low pH (~7.7 pH units) and low calcite saturation, agglutinated and symbiont-bearing species were relatively more abundant, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics declined steeply with decreasing pH, despite exposure of this ecosystem for millennia to low pH conditions, suggesting that tropical foraminifera communities will be negatively impacted under acidification scenarios SSP3-7.0 and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean, was able to calcify at conditions more extreme than those projected for the late 21st century (7.1 pH units), but the calcified tests were of lower density than those exposed to higher-pH ambient conditions (7.96 pH units), indicating that reef foraminiferal carbonate budget might decrease. Smaller foraminifera were highly sensitive to decreasing pH and our results demonstrate their potential as indicators to monitor increasing OA conditions.

Continue reading ‘Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico’

New Zealand’s media and the crisis in the ocean: news norms and scientific urgency

Published 26 May 2023 Science Leave a Comment
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1. To date, no studies have analysed New Zealand’s media coverage of ocean-related threats, potential harms, or sources used for their coverage. This is concerning given that marine media coverage is linked to public support, awareness of conservation issues, and policymaking.

2. This research helps fill this gap, examining all ocean-related articles 2 weeks before and after the 2019 Intergovernmental Panel on Climate Change (IPCC) report’s release on the oceans and cryosphere.

3. It first analyses the media’s reporting of threats, potential harms arising from the threats, and the sources on whom journalists relied and gave voice, then it tests a report of global significance for influence on reportage.

4. Second, it examines whether the threats covered by media align with scientists’ main concerns (from the IPCC report and a survey of New Zealand scientists).

5. In contrast to previous studies on media sources for environmental conservation, this study found that journalists in New Zealand relied considerably on scientists as key sources. However, it found that coverage of ocean-related threats did not match scientists’ main concerns.

6. Finally, the research found that the IPCC report appeared to influence coverage in two areas: reporting on threats to island nations, and multiple potential harms. Otherwise, New Zealand’s media covered the IPCC report as any other news item, reporting on it and then shifting to other matters.

7. The lack of coverage on primary scientific concerns and that a globally significant momentous report did not dramatically impact the marine media landscape is problematic for conservation of ocean habitats, species, and broader environmental and societal outcomes owing to poor understandings by policymakers and the public, which can lead to inaction and policy failures.

8. The potential reasons and solutions to advance communication of marine conservation issues for a more educated and mobilized public are explored.

Continue reading ‘New Zealand’s media and the crisis in the ocean: news norms and scientific urgency’

Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont

Published 26 May 2023 Science Leave a Comment
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Introduction: 

Reef building oysters provide vast ecological benefits and ecosystem services. A large part of their role in driving ecological processes is mediated by the microbial communities that are associated with the oysters; together forming the oyster holobiont. While changing environmental conditions are known to alter the physiological performance of oysters, it is unclear how multiple stressors may alter the ability of the oyster holobiont to maintain its functional role.

Methods: 

Here, we exposed oysters to acidification and hypoxia to examine their physiological responses (molecular defense and immune response), changes in community structure of their associated microbial community, and changes in water nutrient concentrations to evaluate how acidification and hypoxia will alter the oyster holobiont’s ecological role.

Results: 

We found clear physiological stress in oysters exposed to acidification, hypoxia, and their combination but low mortality. However, there were different physiological trade-offs in oysters exposed to acidification or hypoxia, and the combination of stressors incited greater physiological costs (i.e., >600% increase in protein damage and drastic decrease in haemocyte counts). The microbial communities differed depending on the environment, with microbial community structure partly readjusted based on the environmental conditions. Microbes also seemed to have lost some capacity in nutrient cycling under hypoxia and multi-stressor conditions (~50% less nitrification) but not acidification.

Discussion: 

We show that the microbiota associated to the oyster can be enriched differently under climate change depending on the type of environmental change that the oyster holobiont is exposed to. In addition, it may be the primary impacts to oyster physiology which then drives changes to the associated microbial community. Therefore, we suggest the oyster holobiont may lose some of its nutrient cycling properties under hypoxia and multi-stressor conditions although the oysters can regulate their physiological processes to maintain homeostasis on the short-term.

Continue reading ‘Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont’

Exposure to extremes in multiple global change drivers: characterizing pH, dissolved oxygen, and temperature variability in a dynamic, upwelling dominated ecosystem

Published 25 May 2023 Science Leave a Comment
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In upwelling systems, fluctuations in seawater pH, dissolved oxygen (DO), and temperature can expose species to extremes that differ greatly from the mean conditions. Understanding the nature of this exposure to extremes, including how exposure to low pH, low DO concentrations, and temperature varies spatiotemporally and in the context of other drivers, is critical for informing global change biology. Here, we use a 4-yr time series of coupled pH, DO, and temperature observations at six nearshore kelp forest sites spanning the coast of California to characterize the variability and covariance among these drivers. We further compare observed properties to those derived from a high-resolution coupled physical-biogeochemical simulation for the central California current system. We find the intensity, duration, and severity of exposure to extreme conditions beyond heuristic, biologically relevant pHT (< 7.7), and DO (< 4.6 mg L−1) values were greatest at sites with strong upwelling. In contrast, sites with relatively weaker upwelling had little exposure to pH or DO conditions below these heuristic values but had higher and more variable temperature. The covariance between pH, DO, and temperature was highest in sites with strong upwelling and weakest in sites with limited upwelling. These relationships among pH, DO, and temperature at the observation locations were mirrored in the model, and model output highlighted geographic differences in exposure regimes across the California marine protected area network. Together, these results provide important insight into the conditions marine ecosystems are exposed to relevant to studies of global change biology.

Continue reading ‘Exposure to extremes in multiple global change drivers: characterizing pH, dissolved oxygen, and temperature variability in a dynamic, upwelling dominated ecosystem’
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