Posts Tagged 'North Pacific'

Role of biological activity in mediating acidification in a coastal upwelling zone at the east coast of Hainan Island

Highlights

  • Three types (relief/aggravation/minor) of biological contribution to upwelling-induced acidification are quantitatively revealed at the east coast of Hainan Island.
  • Behaviors of carbonate chemistry and dissolved oxygen in upwelled waters are distinct due to different biological mediation between the nearshore and offshore regimes.
  • Aerobic respiration intensifies acidification in the subsurface of the nearshore area during a coastal upwelling.

Abstract


Coastal upwelling that brings to the surface both CO2- and nutrient-rich deep seawater is related to acidification and intense biological productivities in surface waters. However, the impact of biological activities on upwelling-induced acidification from nearshore to offshore areas in an upwelling zone remains insufficiently known. In this paper, we present daily records of high-resolution profiles of carbonate chemistry and hydrographic parameters from the nearshore to the offshore upwelling zone off the east coast of Hainan Island (ECH) in July 2014 (summer season). A three end-member mixing model was adopted to discriminate biological processes from physical mixing and to further semiquantitatively diagnose biological contribution to the upwelling-induced acidification. The results show divergent responses in pH, aragonite saturation state (ΩAr) and biomediated nonconservative dissolved inorganic carbon (ΔDIC) at depths of 10 m–30 m between nearshore and offshore regimes under the on-going coastal upwelling, which were attributed to the distinct roles of biological activities in mediating acidification in the upper 30 m across the ECH. Specifically, in the offshore regime, enhanced photosynthesis reduced the upwelling-induced acidification by 40% (i.e., type C: relief role), whereas aerobic respiration increased acidification in the subsurface waters of the nearshore regime by 15% (i.e., type B: aggravation role). This led to the pH and ΩAr minimum in upwelled waters along the transect from the nearshore to the offshore. In contrast, the biological contribution was almost negligible over surface waters in the nearshore regime because of the balance between net community productivity and net community calcification (i.e., type A: limited or minor role).

Continue reading ‘Role of biological activity in mediating acidification in a coastal upwelling zone at the east coast of Hainan Island’

Retrieving monthly and interannual total-scale pH (pHT) on theEast China Sea shelf using an artificial neural network:ANN-pHT-v1 (update)

While our understanding of pH dynamics has strongly progressed for open-ocean regions, for marginal seas such as the East China Sea (ECS) shelf progress has been constrained by limited observations and complex interactions between biological, physical and chemical processes. Seawater pH is a very valuable oceanographic variable but not always measured using high-quality instrumentation and according to standard practices. In order to predict total-scale pH (pH(T)) and enhance our understanding of the seasonal variability of pHT on the ECS shelf, an artificial neural network (ANN) model was developed using 11 cruise datasets from 2013 to 2017 with coincident observations of pHT, temperature (T), salinity (S), dissolved oxygen (DO), nitrate (N), phosphate (P) and silicate (Si) together with sampling position and time. The reliability of the ANN model was evaluated using independent observations from three cruises in 2018, and it showed a root mean square error accuracy of 0.04. The ANN model responded to T and DO errors in a positive way and S errors in a negative way, and the ANN model was most sensitive to S errors, followed by DO and T errors. Monthly water column pHT for the period 2000-2016 was retrieved using T, S, DO, N, P and Si from the Changjiang biology Finite-Volume Coastal Ocean Model (FVCOM). The agreement is good here in winter, while the reduced performance in summer can be attributed in large part to limitations of the Changjiang biology FVCOM in simulating summertime input variables.

Continue reading ‘Retrieving monthly and interannual total-scale pH (pHT) on theEast China Sea shelf using an artificial neural network:ANN-pHT-v1 (update)’

The effect of ocean acidification on the enzyme activity of Apostichopus japonicus

Highlights

  • The long-time impact of ocean acidification on enzyme activity of sea cucumbers were studied.
  • The significant difference of enzyme assemblage existed among three experimental groups by the multivariate statistical results.
  • The acidic environment has a great effect on immune process by influencing the elimination of reactive oxygen species (ROS).

Abstract

The influence of ocean acidification (OA) is particularly significant on calcifying organisms. The sea cucumber Apostichopus japonicus is an important cultured calcifying organism in the northern China seas. Little was known about the effects of OA on this economically important species. In this study, individuals from embryo to juveniles stage of A. japonicus, cultured in different levels of acidified seawater, were measured their enzymes activities, including five metabolic enzymes and three immune enzymes. The activity of acid phosphatase (ACP) and alkaline phosphatase (ALP) was significantly lower in the severely acid group (pH 7.1), while the content of lactate dehydrogenase (LDH) was significantly higher. Superoxide dismutase (SOD) and catalase (CAT) were significantly lower in the severely acid group. The multivariate statistical results showed that the significant difference of enzyme assemblage existed among three experimental groups. This study indicated that OA could reduce the biomineralization capacity, influence the anaerobic metabolism and severely affect the immune process of A. japonicas. More researches are needed in the future to reveal the mechanisms of enzyme regulation and expression of A. japonicas underlying mixture environmental stress.

Continue reading ‘The effect of ocean acidification on the enzyme activity of Apostichopus japonicus’

DNA methylation changes in response to ocean acidification at the time of larval metamorphosis in the edible oyster, Crassostrea hongkongensis

Highlights

  • Low pH stress resulted in hyper- and hypo-methylated genes in the pediveliger larvae of the Hong Kong oyster
  • Differentially methylated loci were concentrated in the exon region within the gene bodies
  • High capability of oyster larvae to acclimate and adapt to low pH condition within single generation despite poor habitat selection for attachment
  • Differential methylation is associated to higher metamorphosis success rate and poor larval substratum selection under low pH stress.

Abstract

Unprecedented rate of increased CO2 level in the ocean and the subsequent changes in carbonate system including decreased pH, known as ocean acidification (OA), is predicted to disrupt not only the calcification process but also several other physiological and developmental processes in a variety of marine organisms, including edible oysters. Nonetheless, not all species are vulnerable to those OA threats, e.g. some species may be able to cope with OA stress using environmentally induced modifications on gene and protein expressions. For example, external environmental stressors including OA can influence the addition and removal of methyl groups through epigenetic modification (e.g. DNA methylation) process to turn gene expression “on or off” as part of a rapid adaptive mechanism to cope with OA. In this study, we tested the above hypothesis through testing the effect of OA, using decreased pH 7.4 as proxy, on DNA methylation pattern of an endemic and a commercially important estuary oyster species, Crassostrea hongkongensis at the time of larval habitat selection and metamorphosis. Larval growth rate did not differ between control pH 8.1 and treatment pH 7.4. The metamorphosis rate of the pediveliger larvae was higher at pH 7.4 than those in control pH 8.1, however over one-third of the larvae raised at pH 7.4 failed to attach on optimal substrate as defined by biofilm presence. During larval development, a total of 130 genes were differentially methylated across the two treatments. The differential methylation in the larval genes may have partially accounted for the higher metamorphosis success rate under decreased pH 7.4 but with poor substratum selection ability. Differentially methylated loci were concentrated in the exon regions and appear to be associated with cytoskeletal and signal transduction, oxidative stress, metabolic processes, and larval metamorphosis, which implies the high potential of C. hongkongensis larvae to acclimate and adapt through non-genetic ways to OA threats within a single generation.

Continue reading ‘DNA methylation changes in response to ocean acidification at the time of larval metamorphosis in the edible oyster, Crassostrea hongkongensis’

A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering

In contrast to most seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with a higher pH during the daytime and a lower pH during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon on Dongsha Island had a unique diel pattern with an extremely high pH across a diel cycle. We suggest that this distinct diel pattern in pH was a result of a combination of total alkalinity (TA) production through the coupling of aerobic/anaerobic respiration and carbonate dissolution in the sediments and dissolved inorganic carbon consumption through the high productivity of seagrasses in overlying seawaters. The confinement of the semienclosed inner lagoon may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may provide an ideal scenario for sedimentary TA production and accumulation, thereby forming a strong capacity for seagrass meadows to buffer ocean acidification.

Continue reading ‘A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering’

Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing

Ocean acidification and microplastic pollution is a global environmental threat, this research evaluated the effects of ocean acidification and microplastics on mussel digestive tract microbial community. The 16S rRNA gene was sequenced to characterize the flora. Species diversity in the samples was assessed by clustering valid tags on 97% similarity. Bacteroidetes, Firmicutes and Proteobacteria were the three most abundant genera in the four groups, with Bacteroidetes showing the highest diversity. However, no differences in flora structure were evident under various treatments. Phylogenetic relationship analysis revealed Bacteroidetes and Firmicutes had the highest OTU diversity. The weighted UniFrac distance, principal coordinate analysis (PCoA), unweighted pair group method with arithmetic mean (UPGMA) cluster tree and analysis of molecular variance (AMOVA) evaluation results for all samples also showed that changes in pH and microplastics concentration did not significantly affect the microbial community structure in the mussel digestive tract. The results presented the no significant effects of ocean acidification and microplastics intake on mussel intestinal diversity.

Continue reading ‘Effects of ocean acidification and microplastics on microflora community composition in the digestive tract of the thick shell mussel Mytilus coruscus through 16s RNA gene sequencing’

Ecosystem status report of the California current for 2019–20: a summary of ecosystem indicators compiled by the California current integrated ecosystem assessment team (CCIEA)


This document is an expansion of the ecosystem status report (ESR) provided by the California Current Integrated Ecosystem Assessment Team (CCIEA Team) to the Pacific Fishery Management Council (PFMC) in March 2020 (Harvey et al. 2020). The CCIEA Team provides ESRs annually to PFMC, as one component of the overall CCIEA goal of providing quantitative, integrative science tools, products, and synthesis in support of a more holistic (ecosystem-based) approach to managing marine resources in the California Current. The ESR features a suite of indicators codeveloped by the CCIEA Team and PFMC. The suite of indicators was initially identified in 2009, and has been refined and updated over the years to best capture the current state of the California Current ecosystem (CCE). The analyses in this document represent our best understanding of environmental, ecological, and socioeconomic conditions in this ecosystem roughly through late 2019 and early 2020. Because the time required to process data varies for different indicators, some of the resulting time series are slightly more up-to-date than others. The time series for some indicators (snowpack, sea lion reproduction and pup growth, seabirds, fishery landings, fishery revenue, and nonfishing human activities) have been updated since the March 2020 report to PFMC (Harvey et al. 2020).

Continue reading ‘Ecosystem status report of the California current for 2019–20: a summary of ecosystem indicators compiled by the California current integrated ecosystem assessment team (CCIEA)’

Elevated CO2 affects kelp nutrient quality: a case study of Saccharina japonica from CO2 enriched coastal mesocosm systems

Kelps provide critical services for coastal food chains and ecosystem, and they are important food source for some segments of human population. Despite their ecological importance, little is known about long‐term impacts of elevated CO2 (eCO2) on nutrient metabolites in kelps and the underlying regulation mechanisms. In this study, the kelp Saccharina japonica was cultured in CO2 enriched coastal mesocosm systems for up to 3 months. We found that though eCO2 significantly increased the growth rate, carbon concentrations and C/N ratio of S. japonica, it had no effect on total nitrogen and protein contents at the end of cultivation period. Meanwhile it decreased the lipid, magnesium, sodium, calcium contents and changed the amino acid and fatty acid composition. Combining the genome‐wide transcriptomic and metabolic evidence, we obtained a systems‐level understanding of metabolic response of S. japonica to eCO2. The unique ornithine‐urea cycle (OUC) and aspartate‐argininosuccinate shunt (AAS), coupled with TCA cycle balanced the carbon and nitrogen metabolism under eCO2 by providing carbon skeleton for amino acid synthesis and reduced power for nitrogen assimilation. This research provides a major advance in the understanding of kelp nutrient metabolic mechanism in the context of global climate change, and such CO2‐induced shifts in nutritional value may induce changes in the structure and stability of marine trophic webs and affect the quality of human nutrition resources.

Continue reading ‘Elevated CO2 affects kelp nutrient quality: a case study of Saccharina japonica from CO2 enriched coastal mesocosm systems’

Spectrophotometric loop flow analyzer for high-precision measurement of seawater pH

Highlights

  • Spectrophotometric seawater pH analyzer was developed based on loop flow analysis.
  • The pH analyzer can be used for underway and in situ measurements
  • The precision of in situ measurement system first reached 0.0004.
  • The pH analyzer showed good stability and accuracy in various environments.

Abstract

Automated instrument for long-term measurement of seawater pH is important for documenting the changes of the marine carbonate system and the impacts of ocean acidification. An automated pH analyzer based on loop flow analysis (LFA-pH) was developed to achieve precise and accurate measurements of seawater pH. The circulating loop allows complete mixing of an indicator and seawater, constant mixing volume of two solutions, and correcting indicator perturbation for each measurement. During laboratory testing, the LFA-pH precision achieved 0.0004, and the accuracy was 0.0017±0.0038 compared with the certified standard buffer at different temperatures. During the 59 day underway measurement across the mid and high latitudes, more than 2500 pH measurements were carried out. LFA-pH showed good stability with high temperature and salinity changes, and measurement results were consistent with the discrete surface seawater pH measurement data. In situ testing of two LFA-pHs was completed near the Zhongyuan pier in Qingdao. The average pH offset between the two LFA-pHs was 0.0010±0.0032 (n=788), with the accuracies of the two LFA-pHs of 0.0012±0.0033 and 0.0005±0.0035 compared to discrete measurements. For continuous measurement, the average power consumption is 3.6 W at a 10 min measurement frequency. Given its low power consumption, high precision, and accuracy, FLA-pH could be adapted for underway and in situ measurements of ocean acidification observations.

Continue reading ‘Spectrophotometric loop flow analyzer for high-precision measurement of seawater pH’

Elevated CO2 concentration alleviates UVR-induced inhibition of photosynthetic light reactions and growth in an intertidal red macroalga

Highlights

  • Both photosynthetic and growth rates of Pyropia yezoensis are inhibited by UVR.
  • Ultraviolet radiation showed significant inhibition on PSII but not for PSI.
  • There is an interaction between CO2 concentration and irradiance quality.
  • High CO2 concentration could alleviate the negative effects of UVR.

Abstract

The commercially important red macroalga Pyropia (formerly Porphyra) yezoensis is, in its natural intertidal environment, subjected to high levels of both photosynthetically active and ultraviolet radiation (PAR and UVR, respectively). In the present work, we investigated the effects of a plausibly increased global CO2 concentration on quantum yields of photosystems II (PSII) and I (PSI), as well as photosynthetic and growth rates of P. yezoensis grown under natural solar irradiance regimes with or without the presence of UV-A and/or UV-B. Our results showed that the high-CO2 treatment (~1000 μbar, which also caused a drop of 0.3 pH units in the seawater) significantly increased both CO2 assimilation rates (by 35%) and growth (by 18%), as compared with ambient air of ~400 μbar CO2. The inhibition of growth by UV-A (by 26%) was reduced to 15% by high-CO2 concentration, while the inhibition by UV-B remained at ~6% under both CO2 concentrations. Homologous results were also found for the maximal relative photosynthetic electron transport rates (rETRmax), the maximum quantum yield of PSII (Fv/Fm), as well as the midday decrease in effective quantum yield of PSII (YII) and concomitant increased non-photochemical quenching (NPQ). A two-way ANOVA analysis showed an interaction between CO2 concentration and irradiance quality, reflecting that UVR-induced inhibition of both growth and YII were alleviated under the high-CO2 treatment. Contrary to PSII, the effective quantum yield of PSI (YI) showed higher values under high-CO2 condition, and was not significantly affected by the presence of UVR, indicating that it was well protected from this radiation. Both the elevated CO2 concentration and presence of UVR significantly induced UV-absorbing compounds. These results suggest that future increasing CO2 conditions will be beneficial for photosynthesis and growth of P. yezoensis even if UVR should remain at high levels.

Continue reading ‘Elevated CO2 concentration alleviates UVR-induced inhibition of photosynthetic light reactions and growth in an intertidal red macroalga’

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