Posts Tagged 'North Pacific'

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Clay-shielded estuarine gastropods are better protected against environmental acidification than unshielded individuals

Published 30 January 2023 Science Closed
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Graphical abstract.

Highlights

  • Acidified estuaries compromise building and threaten dissolution of gastropods shells.
  • Periostracum of Neripteron snails directs formation of an outer shell clay shield.
  • Shield constructed of the mineral illite is tightly chemically-bonded to the periostracum.
  • The more reflective unshielded shells showed a greater rate of dissolution.
  • Ecological and evolutionary constraints on carbonate shell building predict outer protection.

Abstract

The effects of progressive global acidification on the shells of marine organisms is a topic of much current interest. Most studies on molluscan shell resistance to dissolution consider the carbonate mineral component, with less known about the protective role of the outer organic periostracum. Outer-shell resistance would seem especially important to gastropods living in carbonate-undersaturated and calcium-deficient estuarine waters that threaten shell dissolution and constrain CaCO3 production. We tested this prediction using gastropods from an acidified estuarine population (Neripteron violaceum) that form a clay shield outside the periostracum. Specifically, we aimed to show that the carbonate shell component lacks integrity, that the formation of the clay shield is directed by the organism, and that the clay shield functions to protect against shell dissolution. We found no evidence for any specific carbonate dissolution resistance strategy in the thin, predominantly aragonitic shells of these gastropods. Shield formation was directed by an ornamented periostracum which strongly bonded illite elements (e.g., Fe, Al and S), that become available through suspension in the water column. In unshielded individuals, CaCO3 erosion was initiated randomly across the shell (not age-related) and progressed rapidly when the periostracum was breached. A light reflectance technique showed qualitatively that shield consolidation is negatively-related to shell erosion. These findings support a conceptual framework for gastropod outer-shell responses to acidification that considers both environmental and evolutionary constraints on shell construction. We describe a novel strategy for shell protection against dissolution, highlighting the diversity of mechanisms available to gastropods facing extreme coastal acidification.

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Response mechanism of harmful algae Phaeocystis globosa to ocean warming and acidification

Published 30 January 2023 Science Closed
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Graphical abstract

Simultaneous ocean warming and acidification will alter marine ecosystem structure and directly affect marine organisms. The alga Phaeocystis globosa commonly causes harmful algal blooms in coastal areas of eastern China. P. globosa often outcompetes other species due to its heterotypic life cycle, primarily including colonies and various types of solitary cells. However, little is known about the adaptive response of P. globosa to ocean warming and acidification. This study aimed to reveal the global molecular regulatory networks implicated in the response of P. globosa to simultaneous warming and acidification. After exposure to warming and acidification, the phosphatidylinositol (PI) and mitogen-activated protein kinase (MAPK) signaling pathways of P. globosa were activated to regulate other molecular pathways in the cell, while the light harvesting complex (LHC) genes were downregulated to decrease photosynthesis. Exposure to warming and acidification also altered the intracellular energy flow, with more energy allocated to the TCA cycle rather than to the biosynthesis of fatty acids and hemolytic substances. The upregulation of genes associated with glycosaminoglycan (GAG) degradation prevented the accumulation of polysaccharides, which led to a reduction in colony formation. Finally, the upregulation of the Mre11 and Rad50 genes in response to warming and acidification implied an increase in meiosis, which may be used by P. globosa to increase the number of solitary cells. The increase in genetic diversity through sexual reproduction may be a strategy of P. globosa that supports rapid response to complex environments. Thus, the life cycle of P. globosa underwent a transition from colonies to solitary cells in response to warming and acidification, suggesting that this species may be able to rapidly adapt to future climate changes through life cycle transitions.

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Spatial pH variability of coral reef flats of Kiritimati Island, Kiribati

Published 27 January 2023 Science Closed
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Ocean acidification poses a threat to carbonate-dominated marine systems, such as tropical coral reefs, as it impacts the ability of organisms to calcify. For assessing the susceptibility of coral reef flats to open ocean acidification it is crucial to better understand the dynamics between the carbonate chemistry of open ocean waters flowing onto coral reef flats and the ecological and hydrodynamic processes that locally modify seawater conditions.

In this study, variations in seawater pH and temperature were measured along cross-reef flat transects in high resolution (∼0.3 m) and complemented by surveys of the benthic community composition and reef flat bathymetry.

Results represent a snapshot in time and suggest that reef flat hydrodynamic processes determine spatial pH modifications, with little influence of variations in benthic community composition. As mean reef flat pH largely equals ocean conditions, ocean acidification has had and will have an unhampered impact on narrow fringing reef flats.

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Population-specific vulnerability to ocean change in a multistressor environment

Published 26 January 2023 Science Closed
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Variation in environmental conditions across a species’ range can alter their responses to environmental change through local adaptation and acclimation. Evolutionary responses, however, may be challenged in ecosystems with tightly coupled environmental conditions, where changes in the covariance of environmental factors may make it more difficult for species to adapt to global change. Here, we conduct a 3-month-long mesocosm experiment and find evidence for local adaptation/acclimation in populations of red sea urchins, Mesocentrotus franciscanus, to multiple environmental drivers. Moreover, populations differ in their response to projected concurrent changes in pH, temperature, and dissolved oxygen. Our results highlight the potential for local adaptation/acclimation to multivariate environmental regimes but suggest that thresholds in responses to a single environmental variable, such as temperature, may be more important than changes to environmental covariance. Therefore, identifying physiological thresholds in key environmental drivers may be particularly useful for preserving biodiversity and ecosystem functioning.

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

Published 24 January 2023 Science Closed
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After three decades of coral research on the impacts of climate change, there is a wide consensus on the adverse effects of heat-stress, but the impacts of ocean acidification (OA) are not well established. Using a review of published studies and an experimental analysis, we confirm the large species-specific component of the OA response, which predicts moderate impacts on coral physiology and pigmentation by 2100 (scenario-B1 or SSP2-4.5), in contrast with the severe disturbances induced by only +2 °C of thermal anomaly. Accordingly, global warming represents a greater threat for coral calcification than OA. The incomplete understanding of the moderate OA response relies on insufficient attention to key regulatory processes of these symbioses, particularly the metabolic dependence of coral calcification on algal photosynthesis and host respiration. Our capacity to predict the future of coral reefs depends on a correct identification of the main targets and/or processes impacted by climate change stressors.

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Ocean acidification increases the impact of typhoons on algal communities

Published 24 January 2023 Science Closed
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Graphical abstract.

Highlights

  • Algal community dynamics studied with three-year monthly surveys at a CO2 seep
  • Acidification consistently altered community composition across all seasons
  • Structurally complex communities shifted to degraded ‘turf’ state with rising pCO2
  • Acidification-driven community changes were maintained by typhoon disturbance
  • Turf-dominated communities displayed low resistance to typhoons

Abstract

Long-term environmental change, sudden pulses of extreme perturbation, or a combination of both can trigger regime shifts by changing the processes and feedbacks which determine community assembly, structure, and function, altering the state of ecosystems. Our understanding of the mechanisms that stabilise against regime shifts or lock communities into altered states is limited, yet also critical to anticipating future states, preventing regime shifts, and reversing unwanted state change. Ocean acidification contributes to the restructuring and simplification of algal systems, however the mechanisms through which this occurs and whether additional drivers are involved requires further study. Using monthly surveys over three years at a shallow-water volcanic seep we examined how the composition of algal communities change seasonally and following periods of significant physical disturbance by typhoons at three levels of ocean acidification (equivalent to means of contemporary ∼350 and future ∼500 and 900 μatm pCO2). Sites exposed to acidification were increasingly monopolised by structurally simple, fast-growing turf algae, and were clearly different to structurally complex macrophyte-dominated reference sites. The distinct contemporary and acidified community states were stabilised and maintained at their respective sites by different mechanisms following seasonal typhoon disturbance. Macroalgal-dominated sites were resistant to typhoon damage. In contrast, significant losses of algal biomass represented a near total ecosystem reset by typhoons for the turf-dominated communities at the elevated pCO2 sites (i.e. negligible resistance). A combination of disturbance and subsequent turf recovery maintained the same simplified state between years (elevated CO2 levels promote turf growth following algal removal, inhibiting macroalgal recruitment). Thus, ocean acidification may promote shifts in algal systems towards degraded ecosystem states, and short-term disturbances which reset successional trajectories may ‘lock-in’ these alternative states of low structural and functional diversity.

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

Published 19 January 2023 Science Closed
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This study assesses whether secondary calcification is driven by a contrasting seasonal pattern (rainy vs dry) that occurs in the Eastern Tropical Pacific (ETP). Secondary calcifiers net calcification rates and coverage were measured in two reefs: the semi-enclosed Bahía Tiburón reef (BT [21°52′30 “N, 105°54/54 “W]) and the open Las Monas fringing reef (LM [21°51ʹ00ʹʹN, 105°52ʹ45ʹʹW]). Measurements were made from 2013 to 2016 using Calcification Accretion Units (CAUs). Seawater temperature, illuminance, pCO2, pH, ΩCa, and ΩAr were also measured. Low means of pCO2, and high means of ΩCa and ΩAr, were measured during the rainy season. At Las Monas, the composition of the calcifier community differed between seasons. A seasonal effect on net calcification was recorded in the semi-enclosed reef and in the exposed microhabitat of both reefs. Overall, net calcification (mean ± SD) was 1.17 ± 1.13 g·CaCO3·m−2·day−1. Calcification in the open fringing reef (1.51 ± 1.32 g·CaCO3·m−2·day−1) was almost double that in the semi-enclosed reef (0.83 ± 0.78 g·CaCO3·m−2·day−1). Calcification also decreased dramatically between 2014 (1.57 g·CaCO3·m−2·day−1) and 2016 (0.99 g·CaCO3·m−2·day−1). The ENSO event of 2015 raised the water temperature almost 1 °C above the decadal average, which led to a mass coral bleaching in both reefs. That thermal stress might explain the calcification decline in 2015–2016, but probably also obscured a clearer seasonal pattern in net calcification. This study is the first to show that anomalous and persistent high seawater temperatures can affect carbonate production by secondary calcifiers.

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Variability of pCO2 and FCO2 in the Mexican Pacific during 25 years

Published 17 January 2023 Science Closed
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Oceanographic features acting on different spatial-temporal scales influence the variation in the partial pressure of CO2 (pCO2) and ocean-atmosphere CO2 flux (FCO2). In this work, we regionally characterize regions of variability in the Mexican Pacific (MP) based on these chemical properties. We also evaluate the seasonal and interannual changes of each region: in the California Current System (CCS), Cabo Corrientes (CC), and Gulf of Tehuantepec (GT) regions. Sea surface temperature (SST), salinity, wind, pCO2, and FCO2 data from 1993 to 2018 were analyzed. Bayesian t-tests (95% credibility intervals) determined showed that the three regions had high probabilities of being different. Typical FCO2 values in the CCS were higher (−27.6–29.8 mmol C m−2 d−1) than those of the CC and GT regions (−19.9–25.8 and − 11.8–12.5 mmol C m−2 d−1, respectively). The highest positive seasonal variation of FCO2 (mean ± standard deviation) was found in the CCS and CC (∼4.6 ± 4.2 mmol C m−2 d−1) regions during spring, and in the GT region (1.2 ± 2 mmol C m−2 d−1) in autumn due to the strong northerly winds. It was found that during ENSO conditions the MP was a source (4.0 and 3.9 mol C m−2 y−1 for El Niño and La Niña, respectively), although on average over the last 25 years included in the study the MP acted as a slight-CO2 sink (∼10.9 ± 0.005 mol C m−2).

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Rapid increase of pCO2 and seawater acidification along Kuroshio at the east edge of the East China Sea

Published 16 January 2023 Science Closed
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Graphical abstract

Highlights

  • Fast rates of pCO2 increase and seawater acidification were found along the Kuroshio mainstream near the East China Sea
  • Under sustained DIC increase, faster seawater warming led to rapid rates of pCO2 increase and acidification
  • It potentially implies a gradual loss of oceanic CO2 uptake in ocean margins under climate change.

Abstract

Rates of seawater acidification and rise of partial pressure of CO2 (pCO2) at ocean margins are highly uncertain. In this study, nine years of time-series data sampled during 2010–2018 along Kuroshio Current near the East China Sea (ECS) were investigated. We found trends of surface seawater pCO2 at 3.70 ± 0.57 μatm year−1 and pH at −0.0033 ± 0.0009 unityear−1, both of which were significantly greater than those reported from other oceanic time series. Mechanistic analysis showed that seawater warming caused rapid rates of pCO2 increase and acidification under sustained DIC increase. The faster pCO2 growth relative to the atmosphere resulted in the CO2 uptake through the air-sea exchange declining by ~50 % (~−0.8 to −0.4 mol C m−2 year−1) over the study period. Our results imply that rapidly warming boundary currents could potentially present an elevated pCO2 trend, leading to a gradual reduction and eventual loss of oceanic CO2 uptake under climate change.

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

Published 13 January 2023 Science Closed
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Climate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature via shading and mitigating ocean acidification via photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species’ functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.

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Simulated impact of ocean alkalinity enhancement on atmospheric CO2 removal in the Bering Sea

Published 11 January 2023 Science Closed
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Abstract

Ocean alkalinity enhancement (OAE) has the potential to mitigate ocean acidification (OA) and induce atmospheric carbon dioxide (CO2) removal (CDR). We evaluate the CDR and OA mitigation impacts of a sustained point-source OAE of 1.67 × 1010 mol total alkalinity (TA) yr−1 (equivalent to 667,950 metric tons NaOH yr−1) in Unimak Pass, Alaska. We find the alkalinity elevation initially mitigates OA by decreasing pCO2 and increasing aragonite saturation state and pH. Then, enhanced air-to-sea CO2 exchange follows with an approximate e-folding time scale of 5 weeks. Meaningful modeled OA mitigation with reductions of >10 μatm pCO2 (or just under 0.02 pH units) extends 100–100,000 km2 around the TA addition site. The CDR efficiency (i.e., the experimental seawater dissolved inorganic carbon (DIC) increase divided by the maximum DIC increase expected from the added TA) after the first 3 years is 0.96 ± 0.01, reflecting essentially complete air-sea CO2 adjustment to the additional TA. This high efficiency is potentially a unique feature of the Bering Sea related to the shallow depths and mixed layer depths. The ratio of DIC increase to the TA added is also high (≥0.85) due to the high dissolved carbon content of seawater in the Bering Sea. The air-sea gas exchange adjustment requires 3.6 months to become (>95%) complete, so the signal in dissolved carbon concentrations will likely be undetectable amid natural variability after dilution by ocean mixing. We therefore argue that modeling, on a range of scales, will need to play a major role in assessing the impacts of OAE interventions.

Key Points

  • We used regional ocean model to simulate single point-source ocean alkalinity enhancement in the Bering Sea
  • The steady state carbon dioxide removal efficiency was near one in years 3+ of the simulation
  • The meaningful modeled ocean acidification mitigation is confined to the region near the alkalinity addition

Plain Language Summary

The Intergovernmental Panel on Climate Change suggests that carbon dioxide (CO2) removal (CDR) approaches will be required to stabilize the global temperature increase at 1.5–2°C. In this study, we simulated the climate mitigation impacts of adding alkalinity (equivalent to 667,950 metric ton NaOH yr−1) in Unimak Pass on the southern boundary of the Bering Sea. We found that adding alkalinity can accelerate the ocean CO2 uptake and storage and mitigate ocean acidification near the alkalinity addition. It takes about 3.6 months for the Ocean alkalinity enhancement impacted area to take up the extra CO2. The naturally cold and carbon rich water in the Bering Sea and the tendency of Bering Sea surface waters to linger near the ocean surface without mixing into the subsurface ocean both lead to high CDR efficiencies (>96%) from alkalinity additions in the Bering Sea. However, even with high efficiency, it would take >8,000 alkalinity additions of the kind we simulated to be operating by the year 2100 to meet the target to stabilize global temperatures within the targeted range.

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Ocean acidification and ammonium enrichment interact to stimulate a short-term spike in growth rate of a bloom forming macroalga

Published 10 January 2023 Science Closed
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Introduction: The coastal macroalgal genus, Ulva, is found worldwide and is considered a nuisance algal genus due to its propensity for forming vast blooms. The response of Ulva to ocean acidification (OA) is of concern, particularly with nutrient enrichment, as these combined drivers may enhance algal blooms because of increased availability of dissolved inorganic resources.

Methods: We determined how a suite of physiological parameters were affected by OA and ammonium (NH4+) enrichment in 22-day laboratory experiments to gain a mechanistic understanding of growth, nutrient assimilation, and photosynthetic processes. We predicted how physiological parameters change across a range of pCO2 and NH4+ scenarios to ascertain bloom potential under future climate change regimes.

Results: During the first five days of growth, there was a positive synergy between pCO2 and NH4+ enrichment, which could accelerate initiation of an Ulva bloom. After day 5, growth rates declined overall and there was no effect of pCO2, NH4+, nor their interaction. pCO2 and NH4+ acted synergistically to increase NO3– uptake rates, which may have contributed to increased growth in the first five days. Under the saturating photosynthetically active radiation (PAR) used in this experiment (500 μmol photon m-2 s-1), maximum photosynthetic rates were negatively affected by increased pCO2, which could be due to increased sensitivity to light when high CO2 reduces energy requirements for inorganic carbon acquisition. Activity of CCMs decreased under high pCO2 and high NH4+ conditions indicating that nutrients play a role in alleviating photodamage and regulating CCMs under high-light intensities.

Discussion: This study demonstrates that OA could play a role in initiating or enhancing Ulva blooms in a eutrophic environment and highlights the need for understanding the potential interactions among light, OA, and nutrient enrichment in regulating photosynthetic processes.

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Multistressor global change drivers reduce hatch and viability of Lingcod embryos, a benthic egg layer in the California Current System

Published 10 January 2023 Science Closed
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Early life history stages of marine fishes are often more susceptible to environmental stressors than adult stages. This vulnerability is likely exacerbated for species that lay benthic egg masses bound to substrate because the embryos cannot evade locally unfavorable environmental conditions. Lingcod (Ophiodon elongatus), a benthic egg layer, is an ecologically and economically significant predator in the highly-productive California Current System (CCS). We ran a flow-through mesocosm experiment that exposed Lingcod eggs collected from Monterey Bay, CA to conditions we expect to see in the central CCS by the year 2050 and 2100. Exposure to temperature, pH, and dissolved oxygen concentrations projected by the year 2050 halved the successful hatch of Lingcod embryos and significantly reduced the size of day-1 larvae. In the year 2100 treatment, viable hatch plummeted (3% of normal), larvae were undersized (83% of normal), yolk reserves were exhausted (38% of normal), and deformities were widespread (94% of individuals). This experiment is the first to expose marine benthic eggs to future temperature, pH, and dissolved oxygen conditions in concert. Lingcod are a potential indicator species for other benthic egg layers for which global change conditions may significantly diminish recruitment rates.

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Effects of seawater acidification and solar ultraviolet radiation on photosynthetic performances and biochemical compositions of Rhodosorus sp. SCSIO-45730

Published 6 January 2023 Science Closed
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Ocean acidification (OA) caused by rising atmospheric CO2 concentration and solar ultraviolet radiation (UVR) resulting from ozone depletion may affect marine organisms, but little is known regarding how unicellular Rhodosorus sp. SCSIO-45730, an excellent species resource containing various biological-active compounds, responds to OA and UVR. Therefore, we conducted a factorial coupling experiment to unravel the combined effects of OA and UVR on the growth, photosynthetic performances, biochemical compositions and enzyme activities of Rhodosorus sp. SCSIO-45730, which were exposed to two levels of CO2 (LC, 400 μatm, current CO2 level; HC, 1000 μatm, future CO2 level) and three levels of UVR (photosynthetically active radiation (PAR), PAR plus UVA, PAR plus UVB) treatments in all combinations, respectively. Compared to LC treatment, HC stimulated the relative growth rate (RGR) due to higher optimum and effective quantum yields, photosynthetic efficiency, maximum electron transport rates and photosynthetic pigments contents regardless of UVR. However, the presence of UVA had no significant effect but UVB markedly reduced the RGR. Additionally, higher carbohydrate content and lower protein and lipid contents were observed when Rhodosorus sp. SCSIO-45730 was cultured under HC due to the ample HCO−3HCO3− applications and active stimulation of metabolic enzymes of carbonic anhydrase and nitrate reductase, thus resulting in higher TC/TN. OA also triggered the production of reactive oxygen species (ROS), and the increase of ROS coincided approximately with superoxide dismutase and catalase activities, as well as phenols contents. However, UVR induced photochemical inhibition and damaged macromolecules, making algal cells need more energy for self-protection. Generally, these results revealed that OA counteracted UVR-related inhibition on Rhodosorus sp. SCSIO-45730, adding our understanding of the red algae responding to future global climate changes.

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Wild oyster population resistance to ocean acidification adversely affected by bacterial infection

Published 22 December 2022 Science Closed
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Graphical abstract.

The carbon dioxide induced ocean acidification (OA) process is well known to have profound effects on physiology, survival and immune responses in marine organisms, and particularly calcifiers including edible oysters. At the same time, some wild populations could develop a complex and sophisticated immune system to cope with multiple biotic and abiotic stresses, such as bacterial infections and OA, over the long period of coevolution with the environment. However, it is unclear how immunological responses and the underlying mechanisms are altered under the combined effect of OA and bacterial infection, especially in the ecologically and economically important edible oysters. Here, we collected the wild population of oyster species Crassostrea hongkongensis (the Hong Kong oyster) from their native estuarine area and carried out a bacterial challenge with the worldwide pervasive pathogen of human foodborne disease, Vibrio parahaemolyticus, to investigate the host immune responses and molecular mechanisms under the high-CO2 and low pH-driven OA conditions. The wild population had a high immune resistance to OA, but the resistance is compromised under the combined effect of OA and bacterial infection both in vivo or in vitro. We classified all transcriptomic genes based on expression profiles and functional pathways and identified the specifically switched on and off genes and pathways under combined effect. These genes and pathways were mainly involved in multiple immunological processes including pathogen recognition, immune signal transduction and effectors. This work would help understand how the immunological function and mechanism response to bacterial infection in wild populations and predict the dynamic distribution of human health-related pathogens to reduce the risk of foodborne disease under the future climate change scenario.

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The effects of temperature and pH on the reproductive ecology of sand dollars and sea urchins: impacts on sperm swimming and fertilization

Published 22 December 2022 Science Closed
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In an era of climate change, impacts on the marine environment include warming and ocean acidification. These effects can be amplified in shallow coastal regions where conditions often fluctuate widely. This type of environmental variation is potentially important for many nearshore species that are broadcast spawners, releasing eggs and sperm into the water column for fertilization. We conducted two experiments to investigate: 1) the impact of water temperature on sperm swimming characteristics and fertilization rate in sand dollars (Dendraster excentricus; temperatures 8-38°C) and sea urchins (Mesocentrotus franciscanus; temperatures 8-28°C) and; 2) the combined effects of multiple stressors (water temperature and pH) on these traits in sand dollars. We quantify thermal performance curves showing that sand dollar fertilization rates, sperm swimming velocities, and sperm motility display remarkably wide thermal breadths relative to red urchins, perhaps reflecting the wider range of water temperatures experienced by sand dollars at our field sites. For sand dollars, both temperature (8, 16, 24°C) and pH (7.1, 7.5, 7.9) affected fertilization but only temperature influenced sperm swimming velocity and motility. Although sperm velocities and fertilization were positively correlated, our fertilization kinetics model dramatically overestimated measured rates and this discrepancy was most pronounced under extreme temperature and pH conditions. Our results suggest that environmental stressors like temperature and pH likely impair aspects of the reproductive process beyond simple sperm swimming behavior.

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Observed and projected impacts of coastal warming, acidification, and deoxygenation on Pacific oyster (Crassostrea gigas) farming: a case study in the Hinase Area, Okayama Prefecture and Shizugawa Bay, Miyagi Prefecture, Japan

Published 20 December 2022 Science Closed
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Coastal warming, acidification, and deoxygenation are progressing, primarily due to the increase in anthropogenic CO2. Coastal acidification has been reported to have effects that are expected to become more severe as acidification progresses, including inhibiting formation of the shells of calcifying organisms such as shellfish. However, compared to water temperature, an indicator of coastal warming, spatiotemporal variations in acidification and deoxygenation indicators such as pH, aragonite saturation state (Ωarag), and dissolved oxygen in coastal areas of Japan have not been observed and projected. Moreover, many species of shellfish are important fisheries resources, including Pacific oyster (Crassostrea gigas). Therefore, there is concern regarding the future combined impacts of coastal warming, acidification, and deoxygenation on Pacific oyster farming, necessitating evaluation of current and future impacts to facilitate mitigation measures. We deployed continuous monitoring systems for coastal warming, acidification, and deoxygenation in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan. In Hinase, the Ωarag value was often lower than the critical level of acidification for Pacific oyster larvae, although no impact of acidification on larvae was identified by microscopy examination. Oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters. No significant future impact of surface-water deoxygenation on Pacific oysters was identified. To minimize the impacts of coastal warming and acidification on Pacific oyster and related local industries, cutting CO2 emissions is mandatory, but adaptation measures such as regulation of freshwater and organic matter inflow from rivers and changes in the form of oyster farming practiced locally might also be required.

Continue reading ‘Observed and projected impacts of coastal warming, acidification, and deoxygenation on Pacific oyster (Crassostrea gigas) farming: a case study in the Hinase Area, Okayama Prefecture and Shizugawa Bay, Miyagi Prefecture, Japan’

Ocean acidification and warming significantly affect coastal eutrophication and organic pollution: a case study in the Bohai Sea

Published 14 December 2022 Science Closed
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Highlights

  • Ocean acidification alone favors eutrophication and organic pollution.
  • Warming alone inhibits eutrophication and organic pollution.
  • Interactions between acidification and warming may exacerbate organic pollution.
  • Their interactions may mitigate the progress of eutrophication.

Abstract

Most coastal ecosystems are faced with novel challenges associated with human activities and climate change such as ocean acidification, warming, eutrophication, and organic pollution. However, data on the independent or combined effects of ocean acidification and warming on coastal eutrophication and organic pollution at present are relatively limited. Here, we applied the generalized additive models (GAMs) to explore the dynamics of coastal eutrophication and organic pollution in response to future climate change in the Bohai Sea. The GAMs reflected the fact that acidification alone favors eutrophication and organic pollution, while warming alone inhibits these two variables. Differently, the interactions between acidification and warming in the future may further exacerbate the organic pollution but may mitigate the progress of eutrophication. These different responses of eutrophication and organic pollution to acidification and warming may be attributed to algae growth and microbial respiration, as well as some physical processes such as stratification.

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Bathyal octopus, Muusoctopus leioderma, living in a world of acid: first recordings of routine metabolic rate and critical oxygen partial pressures of a deep water species under elevated pCO2

Published 14 December 2022 Science Closed
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Elevated atmospheric CO2 as a result of human activity is dissolving into the world’s oceans, driving a drop in pH, and making them more acidic. Here we present the first data on the impacts of ocean acidification on a bathyal species of octopus Muusoctopus leioderma. A recent discovery of a shallow living population in the Salish Sea, Washington United States allowed collection via SCUBA and maintenance in the lab. We exposed individual Muusoctopus leioderma to elevated CO2 pressure (pCO2) for 1 day and 7 days, measuring their routine metabolic rate (RMR), critical partial pressure (Pcrit), and oxygen supply capacity (α). At the time of this writing, we believe this is the first aerobic metabolic data recorded for a member of Muusoctopus. Our results showed that there was no change in either RMR, Pcrit or α at 1800 µatm compared to the 1,000 µatm of the habitat where this population was collected. The ability to maintain aerobic physiology at these relatively high levels is discussed and considered against phylogeny and life history.

Continue reading ‘Bathyal octopus, Muusoctopus leioderma, living in a world of acid: first recordings of routine metabolic rate and critical oxygen partial pressures of a deep water species under elevated pCO2’

Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)

Published 12 December 2022 Science Closed
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The combined effect of elevated pCO2 (Partial Pressure of Carbon Dioxide) and decreased salinity, which is mainly caused by freshwater input, on the growth and physiological traits of algae has been poorly assessed. In order to investigate their individual and interactive effects on the development of commercially farmed algae, the juvenile sporophytes of Saccharina japonica were cultivated under different levels of salinity (30, 25 and 20 psu) and pCO2 (400 and 1000 µatm). Individually, decreased salinity significantly reduced the growth rate and pigments of S. japonica, indicating that the alga was low-salinity stressed. The maximum quantum yield, Fv/Fm, declined at low salinities independent of pCO2, suggesting that the hyposalinity showed the main effect. Unexpectedly, the higher pCO2 enhanced the maximum relative electron transport rate (rETRmax) but decreased the growth rate, pigments and soluble carbohydrates contents. This implies a decoupling between the photosynthesis and growth of this alga, which may be linked to an energetic reallocation among the different metabolic processes. Interactively and previously untested, the decreased salinity offset the improvement of rETRmax and aggravated the declines of growth rate and pigment content caused by the elevated pCO2. These behaviors could be associated with the additionally decreased pH that was induced by the low salinity. Our data, therefore, unveils that the decreased salinity may increase the risks of future CO2-induced ocean acidification on the production of S. japonica.

Continue reading ‘Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)’
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