Posts Tagged 'field'

Implementing a finite-volume coupled physical-biogeochemical model to the coastal East China Sea

Several models for estuarine physical processes and biogeochemistry have been developed over last decades. One of the most comprehensive coupled model systems, Finite Volume Community Coastal Model (FVCOM) coupled with European Regional Seas Ecosystem Model (ERSEM) through the Framework for Aquatic Biogeochemical Models (FABM) has been implemented to a high resolution coastal East China Sea (ECS), which encompassed complex coastal zone and part of continental shelf. Physical model was assessed by traditional univariate comparisons, while a rigorous model skill assessment was conducted for coupled biological model. The model system’s ability to reproduce major characteristics both in physical and biological environments was evaluated. The roles of physical, chemical and environmental parameters on the biogeochemistry of the ECS were extensively studied. This work could form a significant basis for future work, e.g. the response of biogeochemical flux to physical mechanism.

Continue reading ‘Implementing a finite-volume coupled physical-biogeochemical model to the coastal East China Sea’

Organic carbon and carbonate system in the bottom sediments of shallow bights of the Peter the Great Bay (Sea of Japan)

The diagenesis of organic matter (OM) is studied in bottom sediments taken in February, 2018 from therapeutic mud deposits of the Uglovoi Bay and Voevoda and Ekspeditsiya bights (Peter the Great Bay, Sea of Japan). The carbonate system of bottom sediments and pore water were analyzed for the contents of nutrients, dissolved organic carbon, humic substance, and concentrations of sulfates and chlorides. The concentrations of organic carbon, chlorophyll-a, humic and fulvic acids, and mobile sulfide species are measured in a solid phase of sediment. Underwater photographing shows that sampling localities are covered by Zostera marina meadows in the Voevoda and Ekspeditsiya bights and by diatom mats in Uglovoi Bay. The proportions between dissolved inorganic carbon and alkalinity, as well as data on sulfate–chlorine ratios and mobile sulfide species indicate that the OM degradation in bottom sediments is mainly controlled by sulfate reduction. The Uglovoi Bay and Voevoda and Ekspeditsii bights are characterized by different values of bioturbation coefficients: 3.0, 107.6, and 14.5 cm2/day, respectively. The estimated fluxes of organic carbon from water into sediment and of dissolved inorganic carbon from sediment into water significantly differ. The disbalance between organic and inorganic carbons can be caused by the following reasons: (a) ignored CO2 flux released by marine organisms from bottom sediments through their siphonal system; (b) partial OM consumption in food with its subsequent deposition in it.

Continue reading ‘Organic carbon and carbonate system in the bottom sediments of shallow bights of the Peter the Great Bay (Sea of Japan)’

Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea

Human-induced global change has caused rapid increases in ocean temperature (warming) and declines in seawater pH (acidification), and are expected to have negative impacts on tropical reef-building corals globally. Abnormally high seawater temperatures disrupt the symbiosis between corals and their algal endosymbiont in a process known as ‘coral bleaching.’ During such bleaching events, calcification rates decline and physiological processes deteriorate. Additionally, corals rely heavily on elevated seawater pH in order to support and maintain production of their calcium carbonate skeletons. Together, changes in ocean temperatures and seawater pH pose serious threats to coral reefs, foundational ecosystems that provide habitat for countless essential fisheries, while also acting as natural buffers from storms and providing major economic support for tropical coastal communities. Identifying how these global scale stressors impact Caribbean coral reefs is critical in understanding community composition and coral abundance on future reefs. This dissertation employs an interdisciplinary suite of techniques to assess the impacts of ocean acidification and warming on the growth and physiology of Caribbean corals to improve understandings of the responses of coral under projected global change, and provide a framework for similar future studies. Through the use of a meta-analysis (Chapter 1), I identified trends in coral calcification throughout the Greater Caribbean Sea in response to experimental ocean acidification and warming, and performed quantitative assessment of experimental design effects on coral calcification rates. I then conducted a 93- day simulated ocean acidification and warming mesocosm experiment to identify growth (Chapter 2, 4) and physiological (Chapter 3) responses of several species of common Caribbean corals. The results from this work highlight the diversity of responses of Caribbean corals to projected global change at individual and species levels, as well as between the coral host and algal endosymbiont. Overall, the variation in growth and physiological responses of these important Caribbean coral species under ocean acidification and warming is critical in predicting the future ‘winners’ and ‘losers’ of Caribbean reefs as global change unfolds.

Continue reading ‘Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea’

Evaluation of a new carbon dioxide system for autonomous surface vehicles

Current carbon measurement strategies leave spatiotemporal gaps that hinder the scientific understanding of the oceanic carbon biogeochemical cycle. Data products and models are subject to bias because they rely on data that inadequately capture mesoscale spatiotemporal (kilometers and days to weeks) changes. High-resolution measurement strategies need to be implemented to adequately evaluate the global ocean carbon cycle. To augment the spatial and temporal coverage of ocean-atmosphere carbon measurements, an Autonomous Surface Vehicle CO2 (⁠⁠) system was developed. From 2011 to 2018, ASVCO2 systems were deployed on seven Wave Glider and Saildrone missions along the U.S. Pacific and Australia’s Tasmanian coastlines and in the tropical Pacific to evaluate the viability of the sensors and their applicability to carbon cycle research. Here we illustrate that the ASVCO2 systems are capable of long-term oceanic deployment and robust collection of air and seawater pCO2 within ± 2 µatm based on comparisons with established ship-board underway systems, with previously described MAPCO2 systems, and with companion ASVCO2 systems deployed side-by-side.

Continue reading ‘Evaluation of a new carbon dioxide system for autonomous surface vehicles’

Along-path evolution of biogeochemical and carbonate system properties in the Intermediate Water of the Western Mediterranean

A basin-scale oceanographic cruise (OCEANCERTAIN2015) was carried out in the Western Mediterranean (WMED) in summer 2015 to study the evolution of hydrological and biogeochemical properties of the most ubiquitous water mass of the Mediterranean Sea, the Intermediate Water (IW). IW is a relatively warm water mass, formed in the Eastern Mediterranean (EMED) and identified by a salinity maximum all over the basin. While it flows westward, toward and across the WMED, it gradually loses its characteristics. This study describes the along-path changes of thermohaline and biogeochemical properties of the IW in the WMED, trying to discriminate changes induced by mixing and changes induced by interior biogeochemical processes. In the first part of the path (from the Sicily Channel to the Tyrrhenian Sea), respiration in the IW interior was found to have a dominant role in determining its biogeochemical evolution. Afterward, when IW crosses regions of enhanced vertical dynamics (Ligurian Sea, Gulf of Lion and Catalan Sea), mixing with surrounding water masses becomes the primary process. In the final part of the investigated IW path (the Menorca-Mallorca region), the role of respiration is further masked by the effects of a complex circulation of IW, indicating that short-term sub-regional hydrological processes are important to define IW characteristics in the westernmost part of the investigated area. A pronounced along-path acidification was detected in IW, mainly due to remineralization of organic matter. This induced a shift of the carbonate equilibrium toward more acidic species and makes this water mass increasingly less adequate for an optimal growth of calcifying organisms. The carbonate buffering capacity also decreases as IW flows through the WMED, making it more exposed to the adverse effects of a decreasing pH. The present analysis indicates that IW evolution in the sub-basins of the WMED is currently driven by complex hydrological and biogeochemical processes, which could be differently impacted by coming climate changes, in particular considering expected increases of extreme meteorological events, mainly due to the warming of the Mediterranean basin.

Continue reading ‘Along-path evolution of biogeochemical and carbonate system properties in the Intermediate Water of the Western Mediterranean’

Severe coastal hypoxia interchange with ocean acidification: an experimental perturbation study on carbon and nutrient biogeochemistry

Normally atmospheric CO2 is the major driver of ocean acidification (OA); however, local discharge/degradation of organic matter (OM) and redox reactions can exacerbate OA in coastal areas. In this work we study the response of nutrient and carbon systems to pH decrease in relation to hydrographically induced intermittent characteristics and examine scenarios for future ocean acidification in a coastal system. Laboratory microcosm experiments were conducted using seawater and surface sediment collected from the deepest part of Elefsis Bay; the pH was constantly being monitored while CO2 gas addition was adjusted automatically. In Elefsis Bay surface pCO2 is already higher than global present atmospheric values, while near the bottom pCO2 reaches 1538 μatm and carbonate saturation states were calculated to be around 1.5. During the experiment, in more acidified conditions, limited alkalinity increase was observed and was correlated with the addition of bicarbonates and OM. Ammonium oxidation was decelerated and a nitrification mechanism was noticed, despite oxygen deficiency, paralleled by reduction of Mn-oxides. Phosphate was found significantly elevated for the first time in lower pH values, without reprecipitating after reoxygenation; this was linked with Fe(II) oxidation and Fe(III) reprecipitation without phosphate adsorption affecting both available dissolved phosphate and (dissolved inorganic nitrogen) DIN:DIP (dissolved inorganic phosphate)ratio.

Continue reading ‘Severe coastal hypoxia interchange with ocean acidification: an experimental perturbation study on carbon and nutrient biogeochemistry’

ARIOS: An acidification ocean database for the Iberian Upwelling Ecosystem (1976–2018)

A data product of 17,653 discrete samples from 3,357 oceanographic stations combining measurements of pH, alkalinity and other biogeochemical parameters off the North-western Iberian Peninsula from June 1976 to September 2018 is presented in this study. The oceanography cruises funded by 24 projects were primarily carried out in the Ría de Vigo coastal inlet, but also in an area ranging from the Bay of Biscay to the Portuguese coast. The robust seasonal cycles and long-term trends were only calculated along a longitudinal section, gathering data from the coastal and oceanic zone of the Iberian Upwelling System. The pH in the surface waters of these separated regions, which were highly variable due to intense photosynthesis and the remineralization of organic matter, showed an interannual acidification ranging from −0.0016 yr−1 to −0.0032 yr−1 that grew towards the coastline. This result is obtained despite the buffering capacity increasing in the coastal waters further inland as shown by the increase in alkalinity by 1.1±0.7 μmol kg−1 yr−1 and 2.6±1.0 μmol kg−1 yr−1 in the inner and outer Ría de Vigo respectively, driven by interannual changes in the surface salinity of 0.0193±0.0056 psu yr−1 and 0.0426±0.016 psu yr−1 respectively. The loss of the vertical salinity gradient in the long-term trend in the inner ria was consistent with other significant biogeochemical changes such as a lower oxygen concentration and fertilization of the surface waters. These findings seem to be related to a growing footprint of sediment remineralization of organic matter in the surface layer of a more homogeneous water column. Data are available at: https://doi.org/10.20350/digitalCSIC/12498 (Pérez et al., 2020).

Continue reading ‘ARIOS: An acidification ocean database for the Iberian Upwelling Ecosystem (1976–2018)’

Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios

Highlights

•Calcifying algae were exposed to herbicide and future climate scenarios combined.

•Half of the algae were given long acclimation to future climate-change conditions.

•Experimental effects were exaggerated for algae that were not acclimated.

•Still, herbicide effects on acclimated algae stronger in future climate conditions

•Results show the need of climate-adjusted thresholds for water quality guidelines.

Abstract

Tropical marine habitat-builders such as calcifying green algae can be susceptible to climate change (warming and acidification). This study evaluated the cumulative effects of ocean warming (OW), ocean acidification (OA) and the herbicide diuron on the calcifying green algae Halimeda opuntia. We also assessed the influence of acclimation history to experimental climate change conditions on physiological responses. H. opuntia were exposed for 15 days to orthogonal combinations of three climate scenarios [ambient (28 °C, pCO2 = 378 ppm), 2050 (29 °C, pCO2 = 567 ppm) and 2100 (30 °C, pCO2 = 721 ppm)] and to six diuron concentrations (up to 29 μg L−1). Half of the H. opuntia had been acclimated for eight months to the climate scenarios in a mesocosm approach, while the remaining half were not pre-acclimated, as is current practice in most experiments. Climate effects on quantum yield (ΔF/Fm′), photosynthesis and calcification in future climate scenarios were significantly stronger (by −24, −46 and +26%, respectively) in non-acclimated algae, suggesting experimental bias may exaggerate effects in organisms not appropriately acclimated to future-climate conditions. Thus, full analysis was done on acclimated plants only. Interactive effects of future climate scenarios and diuron were observed for ΔF/Fm′, while the detrimental effects of climate and diuron on net photosynthesis and total antioxidant capacity (TAC) were additive. Calcification-related enzymes were negatively affected only by diuron, with inhibition of Ca-ATPase and upregulation of carbonic anhydrase. The combined and consistent physiological and biochemical evidence of negative impacts (across six indicators) of both herbicide and future-climate conditions on the health of H. opuntia highlights the need to address both climate change and water quality. Guideline values for contaminants may also need to be lowered considering ‘climate adjusted thresholds’. Importantly, this study highlights the value of applying substantial future climate acclimation periods in experimental studies to avoid exaggerated organism responses to OW and OA.

Continue reading ‘Acclimation history modulates effect size of calcareous algae (Halimeda opuntia) to herbicide exposure under future climate scenarios’

Adult exposure to acidified seawater influences sperm physiology in Mytilus galloprovincialis: Laboratory and in situ transplant experiments

Highlights

•SWAc impacts on sperm physiology in the M. galloprovincialis after paternal exposure.

•Microcosm and in situ transplant experiment were set up and compared.

•Several sperm quality parameters were analyzed at different exposure times.

•Paternal SWAc exposure affects sperm motility, morphology, mitochondria and pHi.

•Microcosm experiments allowed to explore mechanism underlying responses to SWAc.

Abstract

The ongoing increase of CO2 in the atmosphere is inducing a progressive lowering of marine water pH that is predicted to decrease to 7.8 by the end of this century. In marine environment, physical perturbation may affect reproduction, which is crucial for species’ survival and strictly depends on gamete quality. The effects of seawater acidification (SWAc) on gamete quality of broadcast spawning marine invertebrates result largely from experiments of gamete exposure while the SWAc impact in response to adult exposure is poorly investigated. Performing microcosm and in field experiments at a naturally acidified site, we investigated the effects of adult SWAc exposure on sperm quality parameters underlying fertilization in Mytilus galloprovincialis. These animals were exposed to pH 7.8 over 21 days and collected at different times to analyze sperm parameters as concentration, motility, viability, morphology, oxidative status, intra- and extra-cellular pH and mitochondrial membrane potential. Results obtained in the two experimental approaches were slightly different. Under field conditions, we found an increase in total sperm motility and mitochondrial membrane potential on days 7 and 14 from the start of SWAc exposure whereas, in microcosm, SWAc group showed an increase of total motility on day 14. In addition, sperm morphology and intracellular pH were affected in both experimental approaches; whereas oxidative stress was detected only in spermatozoa collected from mussels under natural SWAc. The overall analysis suggests that, in mussels, SWAc toxic mechanism in spermatozoa does not involve oxidative stress. This study represents the first report on mussel sperm quality impairment after adult SWAc exposure, which may affect fertilization success with negative ecological and economic consequences; it also indicates that, although naturally acidified areas represent ideal natural laboratories for investigating the impact of ocean acidification, microcosm experiments are necessary for examining action mechanisms.

Continue reading ‘Adult exposure to acidified seawater influences sperm physiology in Mytilus galloprovincialis: Laboratory and in situ transplant experiments’

The influence of plastic pollution and ocean change on detrital decomposition

Highlights

•The combined effects of plastic pollution, ocean warming, and acidification on macrophyte decomposition were tested.

•High quantities of plastic slowed the decomposition of seagrass and kelp.

•Ocean warming increased the decomposition rates of seagrass and kelp.

•Ocean acidification did not significantly influence macrophyte decomposition.

•Reducing plastic pollution and CO2 emissions is likely the best approach for preserving detritus-based ecosystem processes.

Abstract

Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyte detrital decomposition. These experiments focused on detritus from kelp, Ecklonia radiata, and eelgrass, Zostera muelleri, and included crossed treatments of (i) no, low and high plastic pollution, (ii) current/future ocean temperatures, and (iii) ambient/future ocean partial pressure of carbon dioxide (pCO2). High levels of plastic pollution significantly reduced the decomposition rate of kelp and eelgrass by approximately 27% and 36% in comparison to controls respectively. Plastic pollution also significantly slowed the nitrogen liberation from seagrass and kelp detritus. Higher seawater temperatures significantly increased the decomposition rate of kelp and eelgrass by 12% and 5% over current conditions, respectively. Higher seawater temperatures were also found to reduce the nitrogen liberation in eelgrass. In contrast, ocean acidification did not significantly influence the rate of macrophyte decomposition or nutrient liberation. Overall, our results show how detrital processes might respond to increasing plastic pollution and ocean temperatures, which has implications for detrital-driven secondary productivity, nutrient dynamics and carbon cycling.

Continue reading ‘The influence of plastic pollution and ocean change on detrital decomposition’

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