Posts Tagged 'North Pacific'

Ocean acidification affects the bioenergetics of marine mussels as revealed by high-coverage quantitative metabolomics

Graphical abstract.

Highlights

  • The metabolic response of mussels to acidification was evaluated.
  • Acidification decreased energy storage and increased energy demands.
  • Acidification affected amino acid metabolism and biosynthesis.
  • Carry-over effects of acidification on cellular energy allocation were observed.

Abstract

Ocean acidification has become a major ecological and environmental problem in the world, whereas the impact mechanism of ocean acidification in marine bivalves is not fully understood. Cellular energy allocation (CEA) approach and high-coverage metabolomic techniques were used to investigate the acidification effects on the energy metabolism of mussels. The thick shell mussels Mytilus coruscus were exposed to seawater pH 8.1 (control) and pH 7.7 (acidification) for 14 days and allowed to recover at pH 8.1 for 7 days. The levels of carbohydrates, lipids and proteins significantly decreased in the digestive glands of the mussels exposed to acidification. The 14-day acidification exposure increased the energy demands of mussels, resulting in increased electron transport system (ETS) activity and decreased cellular energy allocation (CEA). Significant carry-over effects were observed on all cellular energy parameters except the concentration of carbohydrates and cellular energy demand (Ec) after 7 days of recovery. Metabolomic analysis showed that acidification affected the phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine metabolism, and glycine, serine and threonine metabolism. Correlation analysis showed that mussel cell energy parameters (carbohydrates, lipids, proteins, CEA) were negatively/positively correlated with certain differentially abundant metabolites. Overall, the integrated biochemical and metabolomics analyses demonstrated the negative effects of acidification on energy metabolism at the cellular level and implicated the alteration of biosynthesis and metabolism of amino acids as a mechanism of metabolic perturbation caused by acidification in mussels.

Continue reading ‘Ocean acidification affects the bioenergetics of marine mussels as revealed by high-coverage quantitative metabolomics’

Characteristics of calcium isotopes at different water depths and their palaeoenvironmental significance for carbonate rocks of the Permian-Triassic boundary in Chibi, southern China

Calcium isotopes of carbonate rocks can trace calcium cycles and record changes in the marine environment. As published calcium isotope profiles of carbonate rocks at the Permian-Triassic boundary are rare, comparative studies on deep-water profiles were lacking for the major extinction event that occurred during this time. We present sections of different water depths in the Chibi area of southern China that we have selected for a comparative study. We analyzed carbon isotopes, calcium isotopes, as well as major and trace elements of carbonates from two sections (Chibi North and Chibi West) to obtain information on the volcanic activity, ocean acidification, as well as sea level rise and fall in the Chibi area during the mass extinction period. All carbon and calcium isotopes of carbonates from both sections are all negative after the mass extinction boundary. Carbonates from the Chibi North section have higher δ44/40Ca values and lower Sr/Ca ratios than the rocks from the Chibi West section. We propose that the negative bias of the calcium isotopes in the two sections result from diagenesis. Diagenesis transforms primary aragonite into calcite, showing the characteristics of high δ44/40Ca value and low Sr/Ca. By comparing our data with three published profiles of shallow-water carbonate rock, we recognize that calcium isotopes record gradients at different water depths. In the slope environment, the enhancement of pore fluid action near the coast caused an increase of the fluid buffer alteration, and we propose that a regression event occurred in the Chibi region during the Late Permian.

Continue reading ‘Characteristics of calcium isotopes at different water depths and their palaeoenvironmental significance for carbonate rocks of the Permian-Triassic boundary in Chibi, southern China’

Processes controlling the carbonate chemistry of surface seawater along the 150°E transect in the Northwest Pacific ocean

The problem of ocean acidification caused by the increase of atmospheric carbon dioxide concentration is becoming increasingly prominent. Field observation in the northwest Pacific Ocean was carried out along the 150°E transect in November 2019. The distribution characteristics and influencing factors of the surface seawater carbonate chemistry, including dissolved inorganic carbon (DIC), total alkalinity (TA), pH, partial pressure of carbon dioxide (pCO2) and aragonite saturation state (Ωarag) were investigated. DIC and TA ranged from 1915 to 2014 µmol kg−1 and 2243 to 2291 µmol kg−1, respectively; DIC in general decreased with decreasing latitude, but TA had no clear latitudinal gradient. pCO2 values increased with the decrease of latitude and were all below the atmospheric pCO2 level, ranging from 332 to 387 µatm. pH on the total hydrogen ion concentration scale (pHT) decreased with the decrease of latitude in the range of 8.044–8.110, while Ωarag increased with the decrease of latitude in the range of 2.61–3.88, suggesting that the spatial distributions of pHT and Ωarag were out of phase. Compared with the present, the predicted values of pHT and Ωarag by the end of this century would decrease remarkedly; larger declines were found in the higher pHT and Ωarag regions, resulting in the differences along the meridional gradient becoming smaller for both pHT and Ωarag.

Continue reading ‘Processes controlling the carbonate chemistry of surface seawater along the 150°E transect in the Northwest Pacific ocean’

Phosphate limitation intensifies negative effects of ocean acidification on globally important nitrogen fixing cyanobacterium

Growth of the prominent nitrogen-fixing cyanobacterium Trichodesmium is often limited by phosphorus availability in the ocean. How nitrogen fixation by phosphorus-limited Trichodesmium may respond to ocean acidification remains poorly understood. Here, we use phosphate-limited chemostat experiments to show that acidification enhanced phosphorus demands and decreased phosphorus-specific nitrogen fixation rates in Trichodesmium. The increased phosphorus requirements were attributed primarily to elevated cellular polyphosphate contents, likely for maintaining cytosolic pH homeostasis in response to acidification. Alongside the accumulation of polyphosphate, decreased NADP(H):NAD(H) ratios and impaired chlorophyll synthesis and energy production were observed under acidified conditions. Consequently, the negative effects of acidification were amplified compared to those demonstrated previously under phosphorus sufficiency. Estimating the potential implications of this finding, using outputs from the Community Earth System Model, predicts that acidification and dissolved inorganic and organic phosphorus stress could synergistically cause an appreciable decrease in global Trichodesmium nitrogen fixation by 2100.

Continue reading ‘Phosphate limitation intensifies negative effects of ocean acidification on globally important nitrogen fixing cyanobacterium’

High sclerobiont calcification in marginal reefs of the eastern tropical Pacific

Graphical abstract.

A sclerobiont is any organism capable of fouling hard substrates. Sclerobionts have recently received attention due to their notable calcium carbonate contributions to reef structures and potential to offset drops in carbonate budgets in degraded reefs. However, due to their encrusting nature, it is difficult to quantify net calcium carbonate production at the level of individual taxonomic groups, and knowledge regarding the main environmental factors that regulate their spatial distributions is limited. In addition, the material types used to create experimental substrates, their orientations, and their overall deployment times can influence settlement and the composition of the resulting communities. Thus, comparative evaluations of these variables are necessary to improve future research efforts. In this study, we used calcification accretion units (CAUs) to quantify the calcium carbonate contributions of sclerobionts at the taxonomic group level and evaluated the effects of two frequently used materials [i.e., polyvinyl chloride (PVC) and terracotta (TCT) tiles] on the recruitment and calcification of the sclerobiont community in the tropical Mexican Pacific and the Midriff Island Region of the Gulf of California over 6 and 15 months [n = 40; 5 CAUs x site (2) x deployment time (2) x material type (2)]. The net sclerobiont calcification rate (mean ± SD) reached maximum values at six months and was higher in the Mexican Pacific (2.15 ± 0.99 kg m−2 y−1) than in the Gulf of California (1.70 ± 0.67 kg m−2 y−1). Moreover, the calcification rate was slightly higher on the PVC-CAUs compared to that of the TCT-CAUs, although these differences were not consistent at the group level. In addition, cryptic microhabitats showed low calcification rates when compared to those of exposed microhabitatsCrustosecoralline algae and barnacles dominated the exposed experimental surfaces, while bryozoans, mollusks, and serpulid polychaetes dominated cryptic surfaces. Regardless of the site, deployment time, or material type, barnacles made the greatest contributions to calcimass production (between 41 and 88%). Our results demonstrate that the orientation of the experimental substrate, and the material to a lesser extent, influence the sclerobiont community and the associated calcification rate. Upwelling-induced surface nutrient levels, low pH levels, and the aragonite saturation state (ΩAr) limit the early cementation of reef-building organisms in the tropical Mexican Pacific and promote high bioerosion rates in corals of the Gulf of California. Our findings demonstrate that sclerobionts significantly contribute to calcium carbonate production even under conditions of high environmental variability.

Continue reading ‘High sclerobiont calcification in marginal reefs of the eastern tropical Pacific’

Impacts of global environmental change on fish and fisheries of the Northeastern Pacific Ocean

Marine fishes’ intolerance to global change conditions can affect the abundance and distribution of ecologically and economically important species, reshape the structure of trophic webs, and profoundly impact the human communities that rely on fished species for their livelihood and culture. Only by understanding the vulnerability of fished species and fishing communities to global change can we take effective adaptive action and implement climate-ready fisheries management. In this dissertation, I investigate the vulnerability of eight commercially important fished species and one fishing community to global change in the Northeastern Pacific Ocean. In chapter one, I expose Lingcod (Ophiodon elongatus), a benthic egg layer, to temperature, oxygen, and pH conditions we expect to see in the Central California Current System (CCS) by the year 2050 and 2100. I examine both the lethal and sublethal effects of these two multistressor climate change scenarios by measuring differences in metabolic rate, hatching success, and larval quality between treatments. In chapter two, I use a species distribution modeling approach to evaluate how historical (1982-2019) and projected (2030 through end-of-century) warming in the Eastern Bering Sea (EBS), Alaska, affects predator-prey interactions for some of the most commercially valuable fisheries in the U.S. These species include: 1) Pacific Cod (Gadus macrocephalus), 2) Pacific Halibut (Hippoglossus stenolepis), 3) Arrowtooth Flounder, 4) Walleye Pollock (Gadus chalcogrammus), 5) Tanner Crab (Chionoecetes bairdi), 6) Snow Crab (Chionoecetes opilio), and 7) Alaskan Pink Shrimp (Pandalus eous). In chapter three, I use social network analyses to depict the resilience and adaptability of the California Market Squid fishery (Doryteuthis opalescens), the most valuable in the state, to climate perturbations and project changes in habitat suitability by the year 2100 in the CCS. By using all of these vulnerability assessment tools, we can begin to prepare U.S. west coast fisheries for global environmental change.

Continue reading ‘Impacts of global environmental change on fish and fisheries of the Northeastern Pacific Ocean’

Carbonate dynamics in a tropical coastal system in the South China Sea featuring upwelling, river plumes and submarine groundwater discharge

This study examined carbonate dynamics in the northwestern South China Sea (NWSCS), an area jointly influenced by upwelling, river plumes and submarine groundwater discharge. Data were obtained from two cruises conducted in summer 2009 and 2012. In 2009, a high salinity-low temperature water mass occurred nearshore off northeastern Hainan Island, indicative of upwelling, commonly referred to as HNEU. A river plume fueled primarily by local rivers and characterized by low salinity and high temperature was observed in the NWSCS off the mainland roughly along the 30 m isobath. In 2012, coastal upwelling off northeastern Hainan Island was not detectable at the surface, but was observed at a different location off eastern Hainan Island (HEU). River plume waters in 2012 were patchily distributed, with a low salinity zone further westerly than that in 2009 and another on the mid-shelf of the NWSCS sourced from the Pearl River which reached out ∼250 km from the mouth of the Pearl River Estuary. In 2009, elevated dissolved inorganic carbon (DIC) and total alkalinity (TA) occurred in the coastal plume, where submarine groundwater discharge contributed DIC and TA additions of 38.9±20.5 and 42.5±22.3 µmol kg−1, respectively, with a DIC/TA ratio of ∼0.92, which made a minor contribution to the variation of seawater partial pressure of CO2 (pCO2), pH and the aragonite saturation state index (Ωarag). Additionally, high surface phytoplankton production consumed DIC of 10.0±10.4 µmol kg−1 but did not significantly affect TA, which dominated pCO2 drawdown in the coastal plume water and increased the pH and Ωarag at surface. Submarine groundwater discharge was also observed in the region influenced by upwelling, but to a lesser degree than that impacted by coastal plume. Lower pH and Ωarag and higher pCO2 values than in offshore waters were observed downstream of the upwelling system, attributable largely to organic matter remineralization with a DIC addition of 23.8±8.4 µmol kg−1. In 2012, submarine groundwater discharge was not detected but high phytoplankton production dominated carbonate dynamics in the coastal plume water with a net DIC consumption of 104.2 µmol kg−1, which markedly drew down sea surface pCO2 and increased pH and Ωarag. In the Pearl River Plume, the solubility-driven CO2 sink exceeded biological CO2 uptake, resulting in an additional decrease of pH and Ωarag and increase of seawater pCO2. Taken together, this study demonstrated complex spatial and year-to-year variability, and the controls of the carbonate system under the joint modulations of upwelling, river plumes and submarine groundwater discharge. A first order estimate that considered the rise of atmospheric CO2 and seawater temperature further suggested a high risk of ocean acidification in this coastal area by the end of this century, which could be amplified under the stresses of river plumes, submarine groundwater discharge and organic matter remineralization.

Continue reading ‘Carbonate dynamics in a tropical coastal system in the South China Sea featuring upwelling, river plumes and submarine groundwater discharge’

Seasonal nearshore ocean acidification and deoxygenation in the Southern California Bight

The California Current System experiences seasonal ocean acidification and hypoxia (OAH) owing to wind-driven upwelling, but little is known about the intensity, frequency, and depth distribution of OAH in the shallow nearshore environment. Here we present observations of OAH and dissolved inorganic carbon and nutrient parameters based on monthly transects from March 2017 to September 2018 extending from the surf zone to the ~ 40 m depth contour in La Jolla, California. Biologically concerning OAH conditions were observed at depths as shallow as 10 m and as close as 700 m to the shoreline. Below 20 m depth, 8% of observations were undersaturated with respect to aragonite, 28% of observations had a pHT less than 7.85, and 19% of observations were below the sublethal oxygen threshold of 157 µmol kg−1. These observations raise important questions about the impacts of OAH on coastal organisms and ecosystems and how future intensified upwelling may exacerbate these conditions.

Continue reading ‘Seasonal nearshore ocean acidification and deoxygenation in the Southern California Bight’

Epigenetic plasticity enables copepods to cope with ocean acidification

Plasticity enhances species fitness and survival under climate change. Ocean acidification poses a potential threat to copepods, a major zooplankton group that serves as a key link between the lower and higher trophic levels in the marine environment, yet the mechanisms underlying different adaptive responses remain poorly understood. Here we show that although elevated CO2 can exert negative effects on reproduction of Paracyclopina nana, multigenerational plasticity can enable recovery after three generations. By integrating the methylome and transcriptome with the draft genome and undertaking DNA methylation treatments, we demonstrate the vital role of epigenetic modifications in ocean acidification responses and identify regions associated with reproductive resilience. Our results demonstrate that DNA methylation might play an important role in enhancing species fitness of copepods and that failing to consider phenotypic plasticity could lead to overestimation of species’ vulnerabilities.

Continue reading ‘Epigenetic plasticity enables copepods to cope with ocean acidification’

Slow-sinking particulate organic carbon and its attenuation in the mesopelagic water of the South China Sea

Coastal acidification has been widely investigated in terms of its rationale and ecological effects in the last decade. However, the driving mechanism for acidification in open seawater, especially in mesopelagic water, is still poorly understood. Here, the sinking velocity and flux attenuation of particulate organic carbon (POC) were examined based upon the radioactive 210Po-210Pb tracer to reveal the remineralization of POC in the mesopelagic zone in the northeastern South China Sea (SCS). Overall, the profiles of 210Po followed those of 210Pb, lending support to the particle sinking controlled top-down deficits of 210Po. Using an inverse model, the sinking velocity of particles, for the first time in the SCS, was estimated to vary from 3 to 34 m d-1 with the mean value of 15 ± 9 m d-1, indicating that the slow sinking particles largely contribute to the POC flux in the SCS. Beneath the euphotic zone, a consistent descending of the sinking speed implied continuous remineralization of sinking POC in the twilight zone. A preliminary estimate revealed that 1.9-5.4 mmol-C m-2 d-1 remineralized back to carbon dioxide within 100-500 m, representing about 70% of the exported autochthonous POC from the euphotic zone. In 100-1000 m, 2.4-6.6 mmol-C m-2 d-1 (i.e., 84%) remineralized. Thus, the upper twilight zone (i.e., 100-500 m) is the dominant layer of POC remineralization, and POC-induced acidification could be unneglectable there. These results provided insights into the POC-induced acidification mechanism in the mesopelagic water, especially in the upper mesopelagic layer.

Continue reading ‘Slow-sinking particulate organic carbon and its attenuation in the mesopelagic water of the South China Sea’

Phenotypic plasticity in economically and ecologically important bivalves in response to changing environments

Marine bivalves are ecologically important, providing ecosystem services like filtering water, stabilizing substrate, and creating hard structure for epibionts. Cultured bivalves are also economically important, supporting thousands of aquaculture jobs nationwide and providing valuable protein sources for our growing human population. However, recent shifts in the environment such as temperature, ocean acidification, hypoxia, and extreme environmental variation have greatly affected bivalve physiology, reproduction, and survival across multiple lifestages. Bivalves in the Northeast Pacific are increasingly vulnerable climate change related stressors like intensifying upwelling and weather extremes, defined stratification, and unique geography which causes distinct spatial and seasonal variation. I seek to investigate if higher degrees of phenotypic plasticity and parental carryover will have the potential to improve bivalve’s fitness and tolerance as climate change progresses. My goal is to evaluate plastic capacity by taking a multi-method approach to assessing the physiological metrics of several important bivalve species, using both field and laboratory experiments. Early lifestages are greatly influenced by parental environmental history leading to carryover effects, favoring phenotypes that have a higher likelihood of surviving. In addition to natural selection in the wild, commercial and restoration aquaculturists may select for beneficial phenotypes in adults and offspring which would yield the most desirable characteristics. In our experiment, I focus on three different species: the purple-hinge rock scallop Crassadoma gigantea, the Mediterranean mussels Mytilus galloprovincialis, and the Olympia oyster Ostrea lurida. By choosing a suite of native and non-native, inter- and subtidal species, I hope to obtain a broad snapshot of physiological responses to help restore vulnerable species and maximize quality of farmed product. Chapter 1 examines physiological responses of the scallop C. gigantea to climate change related stressors in the laboratory. I conducted a full factorial laboratory experiment, manipulating pCO2 and temperature to mimic current and future ocean acidification and warming levels. After six weeks of acclimation, I found that stressors reduced shell strength and periostracum (outer shell layer) density. Only acidification affected lipids, and fatty acid content varied between treatments. I was the first to quantify microbial composition of a bivalve under multiple stressors and I found differences in the microbiome, especially with temperature stress. Chapter 2 explores physiological responses of C. gigantea and M. galloprovincialis in a six-month field acclimatation experiment. Shellfish were deployed in cages in Puget Sound, Washington at either 5 or 30 m below the surface. I found that environmental gradients varied seasonally and spatially and affected growth, shell strength, and isotopic signatures. There were differences between the two species, namely with shell strength and δ13C. I found that no one depth or time period yielded the most desirable traits for culturing, and I highlight the concerning patterns in Puget Sound’s most productive region. In Chapter 3, I took my research one step further by introducing a spatial component to a one-year field experiment. I outplanted O. lurida in cages at 5 m depth in three different locations in Puget Sound, one of which also had a 20 m depth. Each of these locations had an oceanographic monitoring buoy which allowed me to couple physiological data with high-resolution environmental data. I spawned the oysters to test parental carryover and found evidence in growth rates of larvae, which when acclimated to high temperatures, mirrored their parents. Interestingly, larval survival did not coincide with growth, and through respirometry, I found that 20°C may be a bottleneck for this lifestage. Adult oyster growth, isotopic signatures, and gametogenesis were affected by both seasonal and spatial field conditions. Metabolic responses to pH and temperature depending on recent acclimatization history. This research shows evidence of strong adaptive plasticity which was demonstrated by energetic trade-offs and parental carryover. Chapter 4 acclimatized M. galloprovincialis in the field in a similar fashion to O. lurida. Growth, shell strength, and isotopes were all affected by season and site. Similar to oysters, acute metabolic rate of each site and season was affected differently between pH and temperature. Shellfish covered in Chapter 3/4 have a high degree of plasticity and results are useful to restoration (oyster) and commercial (mussel) aquaculturists to create selective breeding programs that will withstand climate change. Results of this dissertation demonstrate the rapid degree of phenotypic plasticity and capacity for parental carryover in field and laboratory setting though a wide array of physiological analysis. Outcomes of this research add to the limited but growing body of literature about multiple-stressors and field experiments, and indents to assist aquaculturists as climate change progresses.

Continue reading ‘Phenotypic plasticity in economically and ecologically important bivalves in response to changing environments’

Different responses of phytoplankton and zooplankton communities to current changing coastal environments

Marine plankton are faced with novel challenges associated with environmental changes such as ocean acidification, warming, and eutrophication. However, data on the effects of simultaneous environmental changes on complex natural communities in coastal ecosystems are relatively limited. Here we made a systematic analysis of biological and environmental parameters in the Bohai Sea over the past three years to suggest that plankton communities responded differently to current changing coastal environments, with the increase of phytoplankton and the decrease of zooplankton. These different changes of phyto- and zooplankton potentially resulted from the fact that both the effect of acidification as a result of pH decline and the effect of warming as a consequence of increasing temperature favored phytoplankton over zooplankton at present. Furthermore, water eutrophication and salinity as well as heavy metals Hg, Zn, and As had more or less diverse consequences for the dynamics of phytoplankton and zooplankton. Differently, with ongoing climate change, we also revealed that both phytoplankton and zooplankton would decrease in the future under the influence of interactions between acidification and warming.

Continue reading ‘Different responses of phytoplankton and zooplankton communities to current changing coastal environments’

Anthropogenic CO2 in the Philippine Sea, northwestern Pacific: distribution, storage, and decadal variations

Highlights

  • Anthropogenic CO2 (CANT) was investigated with details in the Philippine Sea.
  • CANT storage increased 9–40% faster in the 2010 s than before.
  • More than 82% of CANT storage in the tropical zone is input via ocean circulation.

Abstract

The Philippine Sea, a deep tropical/subtropical marginal sea in the northwestern Pacific, is influenced by the Kuroshio Current in the west and the Kuroshio Recirculation (KR) in the north. In this study, the seawater carbonate system and related parameters were investigated along 130°/136°E and 21°N transects across the Philippine Sea in 2018–2019, and the inventory of anthropogenic CO2 (CANT) was investigated with details. Results showed that the CANT inventory had a maximum value of 38.8 ± 0.6 mol m−2 at 25°−30°N (KR zone) and decreased southward to 27.8 ± 2.5 mol m−2 at 8°−15°N (tropical zone). In the tropical zone, more than 82% of the CANT inventory was input from extra-tropics through ocean transportation. On a decadal scale, the CANT inventory increased by 0.95 ± 0.10 mol m−2 yr−1 in the KR zone during the 2010s, which is 40% higher than that between 1994 and 2007 (∼0.68 mol m−2 yr−1). This acceleration is also higher than that predicted solely on the basis of increased atmospheric CO2. In the tropical zone, however, the CANT inventory increased by 0.59 ± 0.08 mol m−2 yr−1 during the 2010s, which is similar to the rate between 1994 and 2007 (∼0.54 mol m−2 yr−1). This new high-quality dataset of carbonate system parameters could help the future quantification of the oceanic CANT inventory by increasing spatiotemporal resolution in the Philippine Sea.

Continue reading ‘Anthropogenic CO2 in the Philippine Sea, northwestern Pacific: distribution, storage, and decadal variations’

Gregarious larval settlement mediates the responses of new recruits of the reef coral Acropora austera to ocean warming and acidification

Gregarious larval settlement represents an important window for chimera formation in reef corals, yet it remains largely unknown how aggregated settlement and early chimerism could modify the performance and responses of coral recruits under elevated temperature and pCO2. In this study, single and aggregated recruits of the broadcast spawning coral Acropora austera were exposed to contrasts of two temperatures (28 versus 30.5°C) and pCO2 levels (~500 versus 1000 μatm) for two weeks, and algal symbiont infection success, survivorship and growth were assessed. Results showed that symbiont infection success was mainly affected by temperature and recruit type, with reduced symbiont infection at increased temperature and consistently higher infection success in chimeric recruits compared to single recruits. Furthermore, although chimeric recruits with larger areal size had significantly higher survivorship in all treatments, the polyp-specific growth rates were considerably lower in chimeric entities than individual recruits. More importantly, the recruit type significantly influenced the responses of recruit polyp-specific growth rates to elevated temperature, with chimeras exhibiting lowered skeletal lateral growth under elevated temperature. These results demonstrate the benefits and costs associated with gregarious larval settlement for juvenile corals under ocean warming and acidification, and highlight the ecological role of larval settlement behavior in mediating the responses of coral recruits to climate change stressors.

Continue reading ‘Gregarious larval settlement mediates the responses of new recruits of the reef coral Acropora austera to ocean warming and acidification’

Response of calcareous nannoplankton to the Paleocene–Eocene Thermal Maximum in the Paratethys seaway (Tarim Basin, West China)

Highlights

  • A new, shallow marine Paleocene–Eocene Thermal Maximum (PETM) record was discovered in the eastern Tethys.
  • High-resolution calcareous nannofossil biostratigraphy across the PETM was established.
  • The PETM “excursion taxa” are marker species for identifying PETM record in the eastern Tethys.
  • Low pre- and syn-PETM carbonate contents were attributed to ocean acidification and terrestrial dilution.
  • Marine productivity increased during the PETM due to elevated nutrient input from continental weathering.

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) was a rapid global warming occurred 56 million years ago and has been widely viewed as an ancient analogue to the ongoing warming driven by anthropogenic CO2 emissions. The complete and continuous Paleogene shallow marine strata well preserved and outcropped in the Tarim Basin, northwestern China are ideal to study the paleoenvironmental change of the Paratethys Seaway during the PETM. To date, no high-resolution calcareous nannofossil biostratigraphy has been performed for the PETM interval in the Tarim Basin. Outcrop samples taken from the Qimugen Formation in the Kuzigongsu section contain abundant, moderately well preserved calcareous nannofossils allows for the establishment of a high-resolution biostratigraphic framework. Overall, 73 species of calcareous nannofossils from 33 genera were observed, with the dominant species including Coccolithus pelagicus, various Toweius species, Pontosphaera exilis, and Micrantholithus flos. The five calcareous nannofossil datums allow for the recognization of nannofossil Zone NP6 through Zone NP10. The common occurrence of shallow-water taxa (Micrantholithus) throughout the section suggests a middle to outer neritic setting for depositional environment of the Kuzigongsu section. The stratigraphic distribution of “excursion taxa” (Coccolithus bownii, Discoaster araneusD. acutus, Rhomboaster spp.) is consistent with the range of negative excursion in δ13Ccarb and δ18Ocarb, indicating that these excursion taxa are micropaleontological means for identifying the presence of the PETM in the Paratethys Seaway. During the PETM, the deteriorated preservation and extremely low abundance of nannofossils and near-zero wt% CaCO3 values suggest that ocean acidification occurred in the shallow water of the Paratethys Seaway. In addition, a significant increase in the species Neochiastozygus junctus, which is a high productivity indicator indicates increased surface ocean productivity. Higher primary productivity may be triggered by enhanced continental weathering delivering increased nutrient through river runoff.

Continue reading ‘Response of calcareous nannoplankton to the Paleocene–Eocene Thermal Maximum in the Paratethys seaway (Tarim Basin, West China)’

The effects of ocean acidification and temperature rise on the thermal tolerance and critical thermal limit of Pacific herring (Clupea pallasii)

Anthropogenic climate change, including the interactive effects of ocean acidification and temperature rise, is projected to affect marine ecosystems by challenging the environmental tolerance limits of individual species. Such impacts have been documented in a handful of marine fishes, including major physiological effects experienced in early-life stages of Pacific herring, an important forage and commercial fish species widely distributed in coastal systems across the North Pacific. In this study, we investigated the effects of temperatures between 10-16°C and two pCO2 levels (ambient and high pCO2) on hatching and survival of Pacific herring. Survival after acute temperature exposure was assessed and compared between incubation treatments, as may be experienced by herring egg deposits during low tide on warm days. We compared early and late spawning populations to determine if their responses differed when exposed to chronic temperature and pCO2 conditions and to short term temperature stress. A subset of embryos from the 10°C and 16°C treatments were exposed to critical thermal maximum (𝐶𝑇𝑚𝑎𝑥) trials that simulated the acute temperature fluctuations associated with marine heat waves and tidal processes in shallow nearshore habitats. Hatching success was primarily influenced by temperature in both winter and spring embryos. 𝐶𝑇𝑚𝑎𝑥 results indicate that embryos were able to withstand acute exposure to 20°C regardless of spawning population or incubation treatments, but survival was greatly reduced after 2-3 hours at 25°C. Post-exposure heart contraction measurements revealed a greater rate of increase in heart rate in the combined treatment of 10°C and 𝐶𝑇𝑚𝑎𝑥 duration hours compared to 16°C, suggesting respiratory acclimation at higher incubation temperatures. Oxygen consumption rates (MO2) measured at stable incubation conditions resulted in higher MO2 values at elevated temperatures and pCO2 levels. Overall, this study reinforces that Pacific herring are resilient to moderate pCO2 and temperature stress but are vulnerable to acute temperature increases that may accompany marine heatwave events and late season low tide temperatures, and in some cases the combination of elevated pCO2 and temperature can introduce additional challenges for these important forage fish.

Continue reading ‘The effects of ocean acidification and temperature rise on the thermal tolerance and critical thermal limit of Pacific herring (Clupea pallasii)’

Marine pelagic ecosystem responses to climate variability and change

The marine coastal region makes up just 10% of the total area of the global ocean but contributes nearly 20% of its total primary production and over 80% of fisheries landings. Unicellular phytoplankton dominate primary production. Climate variability has had impacts on various marine ecosystems, but most sites are just approaching the age at which ecological responses to longer term, unidirectional climate trends might be distinguished. All five marine pelagic sites in the US Long Term Ecological Research (LTER) network are experiencing warming trends in surface air temperature. The marine physical system is responding at all sites with increasing mixed layer temperatures and decreasing depth and with declining sea ice cover at the two polar sites. Their ecological responses are more varied. Some sites show multiple population or ecosystem changes, whereas, at others, changes have not been detected, either because more time is needed or because they are not being measured.

Continue reading ‘Marine pelagic ecosystem responses to climate variability and change’

Geochemical significance of Acropora death assemblages in the northern South China Sea: implications for environmental reconstruction using branching corals

Highlights

  • Acropora-derived SST reconstruction using Sr/Ca has registered SST shifts around 4–5 ka BP and the modern warming.
  • The universal Li/Mg-SST calibration tends to underestimate the SST reconstruction.
  • Reduced pHcf is found for the post-industrial corals compared to the ancient corals.
  • Coral DICcf exhibits a progressive decrease since the mid-Holocene.
  • Skeletal δ13C is intrinsically linked to the coral CF carbonate chemistry.

Abstract

The geochemistry preserved in coral skeletons provides access to pre-instrumental records of environmental changes. While a variety of proxies have been established for coral paleoclimatology, their applications to the use of Acropora to generate longer-term reconstructions have been studied less. Here, we examine the geochemical proxies (i.e., Sr/Ca, Li/Mg, δ18O, δ13C, δ11B, and B/Ca) of dead Acropora assemblages collected from a fringing reef off Hainan Island in the northern South China Sea. These samples have been precisely dated using Usingle bondTh isotopes and record reef development episodes since the mid-Holocene, allowing us to assess their potential as paleoclimate archives. The sea surface temperature (SST) trend reconstructed by Sr/Ca and Li/Mg exhibits better consistency with each other, and they have recorded the SST shifts around 5–4 ka BP and the subdued variability during the Medieval Climate Anomaly (MCA), whereas the δ18O-SST record exhibits less clear variations over the past 7000 years. However, the universal Li/Mg-SST calibration tends to underestimate the SST reconstruction from tropical corals, highlighting the importance of using a site- and species-specific calibration of the Li/Mg-SST. Boron systematics are used to reconstruct the carbonate chemistry of coral calcifying fluid (CF), which reveals significant differences between the ancient and modern corals. The pH of the coral CF (pHcf) is significantly lower in the modern Acropora compared to the ancient corals, with a mean difference of ~0.08 pH, corroborating the pronounced influence of ocean acidification on the coral CF chemistry. The dissolved inorganic carbon of the coral CF (DICcf) is also lower for modern Acropora, and this decreasing trend seems to have persisted over the past 7000 years. In addition, the skeletal δ13C is closely related to the CF carbonate chemistry, highlighting the intrinsic relationship between the coral internal carbon pool used for calcification and the up-regulation of the pHcf.

Continue reading ‘Geochemical significance of Acropora death assemblages in the northern South China Sea: implications for environmental reconstruction using branching corals’

Integrative assessment of biomarker responses in Mytilus galloprovincialis exposed to seawater acidification and copper ions

Graphical abstract

Highlights

  • Both OA and Cu ions caused physiological disturbances to the mussel.
  • Mussels have the ability to restore most of the tested parameters from the stress of OA and Cu ions.
  • Gills are more sensitive than digestive glands.
  • IBR analysis demonstrated the co-exposure caused the most brutal impact to the mussel.

Abstract

The interactive effects of ocean acidification (OA) and copper (Cu) ions on the mussel Mytilus galloprovincialis are not well understood. The underlying mechanisms also remain obscure. In this study, individuals of M. galloprovincialis were exposed for 28 days to 25 μg/L and 50 μg/L Cu ions at two pH levels (ambient level – pH 8.1; acidified level – pH 7.6). The mussels were then monitored for 56 days to determine their recovery ability. Physiological parameters (clearance rate and respiration rate), oxidative stress and neurotoxicity biomarkers (activities of superoxide dismutase, lipid peroxidation, catalase, and acetylcholinesterase), as well as the recovery ability of these parameters, were investigated in two typical tissues (i.e., gills and digestive glands). Results showed that (1) OA affected the bioconcentration of Cu in the gills and digestive glands of the mussels; (2) both OA and Cu can lead to physiological disturbance, oxidative stress, cellular damage, energy metabolism disturbance, and neurotoxicity on M. galloprovincialis; (3) gill is more sensitive to OA and Cu than digestive gland; (4) Most of the biochemical and physiological alternations caused by Cu and OA exposures in M. galloprovincialis can be repaired by the recovery experiments; (5) integrated biomarker response (IBR) analysis demonstrated that both OA and Cu ions exposure caused survival stresses to the mussels, with the highest effect shown in the co-exposure treatment. This study highlights the necessity to include OA along with pollutants in future studies to better elucidate the risks of ecological perturbations. The work also sheds light on the recovery of marine animals after short-term environmental stresses when the natural environment has recovered.

Continue reading ‘Integrative assessment of biomarker responses in Mytilus galloprovincialis exposed to seawater acidification and copper ions’

Editorial: eutrophication, algal bloom, hypoxia and ocean acidification in large river estuaries

Editorial on the Research Topic
Eutrophication, algal bloom, hypoxia and ocean acidification in large river estuaries

Estuaries are transitional regions of river freshwater to seawater, and biogeochemical parameters such as salinity, nutrients and biological parameters typically show strong gradients in the offshore direction. Estuaries occupy a small portion of the global ocean area (about 0.2%) but play an important role for marine fisheries and contribute disproportionately to the global carbon budget. Furthermore, estuaries are under multiple strong anthropogenic and climate change pressures, such as eutrophication, wetland degradation, and overfishing, and the ecosystems of many estuaries have dramatically changed, leading to hypoxia, harmful algal blooms, ocean acidification and changes in biodiversity.

In this Research Topic, papers were solicited on estuarine systems that exemplify the changes and the complexities of interactions that are occurring in response to anthropogenic and climate change influences. The ten papers on this Research Topic focus largely–but not exclusively–on Asian waters. Asian waters are among the most rapidly changing and progressively impacted by nutrient enrichment and climate change. One of the major themes of these papers is the coupling between physical and biological processes. The themes herein of physical-biological coupling and impacts on water quality changes were also developed in papers on the Chesapeake Bay and the Salish Sea. Modeling, time series analysis and advanced analytical techniques were all brought to bear in the analyses reported.

Continue reading ‘Editorial: eutrophication, algal bloom, hypoxia and ocean acidification in large river estuaries’

  • Reset

Subscribe

OA-ICC Highlights


%d bloggers like this: