An indoor mesocosm experiment was carried out to investigate the combined effects of ocean acidification and warming on the species composition and biogeochemical element cycling during a winter/spring bloom with a natural phytoplankton assemblage from the Kiel fjord, Germany. The experimental setup consisted of a “Control” (ambient temperature of ~4.8 °C and ~535 ± 25 μatm pCO2), a “High-CO2” treatment (ambient temperature and initially 1020 ± 45 μatm pCO2) and a “Greenhouse” treatment (~8.5 °C and initially 990 ± 60 μatm pCO2). Nutrient replete conditions prevailed at the beginning of the experiment and light was provided at in situ levels upon reaching pCO2 target levels. A diatom-dominated bloom developed in all treatments with Skeletonema costatum as the dominant species but with an increased abundance and biomass contribution of larger diatom species in the Greenhouse treatment. Conditions in the Greenhouse treatment accelerated bloom development with faster utilization of inorganic nutrients and an earlier peak in phytoplankton biomass compared to the Control and High CO2 but no difference in maximum concentration of particulate organic matter (POM) between treatments. Loss of POM in the Greenhouse treatment, however, was twice as high as in the Control and High CO2 treatment at the end of the experiment, most likely due to an increased proportion of larger diatom species in that treatment. We hypothesize that the combination of warming and acidification can induce shifts in diatom species composition with potential feedbacks on biogeochemical element cycling.
Posts Tagged 'Baltic'
Shift towards larger diatoms in a natural phytoplankton assemblage under combined high-CO2 and warming conditions
Published 6 June 2018 Science ClosedTags: Baltic, biogeochemistry, biological response, BRcommunity, community composition, laboratory, mesocosms, morphology, multiple factors, otherprocess, phytoplankton, temperature
Anomaly of total boron concentration in the brackish waters of the Baltic Sea and its consequence for the CO2 system calculations
Published 28 May 2018 Science ClosedTags: Baltic, chemistry, methods
- • Total boron (TB) concentration anomaly has been identified for the Baltic Sea.
- • The mean TB concentration in the Baltic Sea rivers (S = 0) is 13.8 μmol kg−1.
- • Ignoring the TB anomaly causes errors in numerical determination of pCO2 and pH.
Abstract
Borates are the third most important component of total alkalinity (AT) in the oxic waters. Their concentrations are a function of the dissociation constant of boric acid and total boron (TB) concentration. The latter is approximated from salinity (S) as boron behave conservatively in the seawater. The linear dependencies between TB and S developed for the open ocean contain no intercept suggesting that river water contains no boron. Based on the historical data and our own measurements we identified a TB vs. S relationship specific for the Baltic Sea: TB [μmol kg−1] = 10.838 ∗ S + 13.821. In the series of the sensitivity tests we analysed what effect can have this anomaly on the determination of borate alkalinity (AB) and on the calculations within the CO2 system performed with AT as an input variable. Due to the high pKa for boric acid the influence of TB anomaly on AB exists only for pH > 8. The highest deviation in AB appears at low salinities. When salinity increases the effect becomes smaller and at salinities > 14, due to lower slope in TB vs. S dependency in the Baltic than in the open ocean, the effect on AB turns to negative and decreases further with the S increase. These uncertainties in ABinfluence calculations of pCO2 (CO2 partial pressure) and pH, when CT (total CO2 concentration) and AT are used as input parameters (the combination used in biogeochemical models). For pCO2 the discrepancies in calculations are not very much dependent on the AT. The highest are observed for low salinities and pH of 8.2–8.4, however they do not exceed 10 μatm. This relatively low influence of TB anomaly on pCO2 calculations is a result of the high distance on the pH scale between high pCO2 conditions (low pH) and the highest AB anomaly (high pH). In case of pH calculations the highest influence of TB anomaly is observed for the low AT and low S waters. For three different AT considered in our study the highest pH errors (up to 0.05 pH unit) were observed for AT = 500 μmol kg−1, while the lowest (up to 0.01 pH unit) were observed for highly buffered waters (AT = 3000 μmol kg−1). Irrespective of the AT the highest errors were found for low CT simulating low pCO2 (and thus high pH) conditions. This is due to the high pKa for boric acid that shifts the effects of the TB anomaly to high pH values. Although the observed discrepancies in pH and pCO2 calculations due to TB anomaly manifest themselves only at the specific environmental conditions the use of experimentally obtained TB vs. S dependency will increase the accuracy of the CO2 system calculations for the Baltic Sea and likely for other brackish systems.
Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors
Published 8 May 2018 Science ClosedTags: Baltic, biological response, chemistry, field, physiology, zooplankton
On a daily basis, planktonic organisms migrate vertically and thus experience widely varying conditions in their physico-chemical environment. In the Gulf of Finland, these changes are larger than values predicted by climate change scenarios predicted for the next century (up to 0.5 units in pH and 5°C in temperature). In this work, we are interested in how temporal variations in physico-chemical characteristics of the water column on a daily and weekly scale influence oxidative stress level and antioxidant responses in the planktonic copepod of the genus Acartia. Responses were determined from samples collected during a two-week field survey in the western Gulf of Finland, Baltic Sea. Our results showed that GST (Glutathione-S-transferase) enzyme activity increased in the surface waters between Weeks I and II, indicating antioxidant defense mechanism activation. This is most likely due to elevating temperature, pH, and dissolved oxygen observed between these two weeks. During Week II also GSSG (oxidized glutathione) was detected, indicating that copepods responded to stressor(s) in the environment. Our results suggest that Acartia copepods seem fairly tolerant to weekly fluctuations in environmental conditions in coastal and estuarine areas, in terms of antioxidant defense and oxidative stress. This could be directly connected to a very efficient glutathione cycling system acting as antioxidant defense system for neutralizing ROS and avoiding elevated levels of LPX.
Shallow water carbonate sediments of the Galapagos archipelago: ecologically sensitive biofacies in a transitional oceanographic environment
Published 4 May 2018 Science ClosedTags: Arctic, Baltic, biogeochemistry, biological response, field, mesocosms, North Atlantic, North Pacific, phytoplankton, primary production
Shallow water carbonate producing organisms are directly controlled by their local oceanography. As a result, long-term environmental signals—stemming from the breakdown of calcareous organisms—can be read from time-averaged carbonate sediments. To better understand these complex biophysical interactions, it is important to study carbonate development within oceanographic transition zones and environments affected by disturbances, such as the El Niño—Southern Oscillation (ENSO). This dissertation represents the first investigation into modern shallow water, soft sediment, carbonate environments of the Galápagos Archipelago, eastern tropical Pacific (ETP). This region is notable for straddling an oceanographic transition zone from tropical oligotrophic to temperate eutrophic—caused by high nutrient and low pH upwelling—and for being directly impacted by ENSO. A top-down approach is followed, which analyzes the biogenic structure of Galápagos sediments and their connection to local and regional oceanography and climate, and then explores how these findings relate to benthic foraminifera—sensitive environmental indicators contained within the sediments. Sediment point counting and statistical models revealed that while these carbonate environments span a biogenic and oceanographic transition comparable to similar settings in the ETP, the proximity of the Galápagos to the ENSO region directly influences its sedimentary structure and distribution. Point counting also revealed a near-absence of benthic foraminifera, which is unusual for ETP, and tropical shallow water carbonates in general. Statistically comparing foraminiferal species composition and diversity to dominant oceanographic parameters revealed the low abundances and distribution of these testate (shelled) single-celled protists to be negatively influenced by the combination of repeated Holocene ENSO events, and the effects of protracted exposure to high nutrient and low pH waters of the southern archipelago. Ultimately, the results of this study may serve as a template for investigating the interaction of carbonates and oceanography within similar atypical tropical assemblages in the fossil record.
Phytoplankton do not produce carbon‐rich organic matter in high CO2 oceans
Published 4 May 2018 Science ClosedTags: Arctic, Baltic, biogeochemistry, biological response, field, mesocosms, North Atlantic, North Pacific, phytoplankton, primary production
The ocean is a substantial sink for atmospheric carbon dioxide (CO2) released as a result of human activities. Over the coming decades the dissolved inorganic C concentration in the surface ocean is predicted to increase, which is expected to have a direct influence on the efficiency of C utilization (consumption and production) by phytoplankton during photosynthesis. Here, we evaluated the generality of C‐rich organic matter production by examining the elemental C:N ratio of organic matter produced under conditions of varying pCO2. The data used in this analysis were obtained from a series of pelagic in situ pCO2 perturbation studies that were performed in the diverse ocean regions and involved natural phytoplankton assemblages. The C:N ratio of the resulting particulate and dissolved organic matter did not differ across the range of pCO2 conditions tested. In particular, the ratio for particulate organic C and N was found to be 6.58 ± 0.05, close to the theoretical value of 6.6.
Bivalve shell formation in a naturally CO2-enriched habitat: unraveling the resilience mechanisms from elemental signatures
Published 29 March 2018 Science ClosedTags: adaptation, Baltic, biological response, laboratory, mollusks, morphology, otherprocess
Research highlights:
- Mya arenaria juveniles from Kiel Fjord can partially alleviate the impact of high pCO2
- Changes in the calcifying fluid chemistry can be inferred from shell elemental signatures
- Cl/Cashell reflects the import of HCO3– in the calcifying fluid
- U/Cashell indicates the pH in the calcifying fluid
- Our work provides new evidence of how marine bivalves respond to high pCO2
Abstract
Marine bivalves inhabiting naturally pCO2-enriched habitats can likely tolerate high levels of acidification. Consequently, elucidating the mechanisms behind such resilience can help to predict the fate of this economically and ecologically important group under near-future scenarios of CO2-driven ocean acidification. Here, we assess the effects of four environmentally realistic pCO2 levels (900, 1500, 2900 and 6600 μatm) on the shell production rate of Mya arenaria juveniles originating from a periodically pCO2-enriched habitat (Kiel Fjord, Western Baltic Sea). We find a significant decline in the rate of shell growth as pCO2 increases, but also observe unchanged shell formation rates at moderate pCO2 levels of 1500 and 2900 μatm, the latter illustrating the capacity of the juveniles to partially mitigate the impact of high pCO2. Using recently developed geochemical tracers we show that M. arenaria exposed to a natural pCO2 gradient from 900 to 2900 μatm can likely concentrate HCO3– in the calcifying fluid through the exchange of HCO3–/Cl– and simultaneously maintain the pH homeostasis through active removal of protons, thereby being able to sustain the rate of shell formation to a certain extent. However, with increasing pCO2 beyond natural maximum the bivalves may have limited capacity to compensate for changes in the calcifying fluid chemistry, showing significant shell growth reduction. Findings of the present study may pave the way for elucidating the underlying mechanisms by which marine bivalves acclimate and adapt to high seawater pCO2.
Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community
Published 20 March 2018 Science ClosedTags: abundance, Baltic, biogeochemistry, biological response, BRcommunity, chemistry, community composition, field, laboratory, multiple factors, otherprocess, photosynthesis, phytoplankton, primary production, prokaryotes, salinity
Helcom scenario modelling suggests that the Baltic Sea, one of the largest brackish-water bodies in the world, could expect increased precipitation (decreased salinity) and increased concentration of atmospheric CO2 over the next 100 years. These changes are expected to affect the microplanktonic food web, and thereby nutrient and carbon cycling, in a complex and possibly synergistic manner. In the Baltic Proper, the extensive summer blooms dominated by the filamentous cyanobacteria Aphanizomenon sp., Dolichospermum spp. and the toxic Nodularia spumigena contribute up to 30% of the yearly new nitrogen and carbon exported to the sediment. In a 12 days outdoor microcosm experiment, we tested the combined effects of decreased salinity (from 6 to 3) and elevated CO2 concentrations (380 and 960 µatm) on a natural summer microplanktonic community, focusing on diazotrophic filamentous cyanobacteria. Elevated pCO2 had no significant effects on the natural microplanktonic community except for higher biovolume of Dolichospermum spp. and lower biomass of heterotrophic bacteria. At the end of the experimental period, heterotrophic bacterial abundance was correlated to the biovolume of N. spumigena. Lower salinity significantly affected cyanobacteria together with biovolumes of dinoflagellates, diatoms, ciliates and heterotrophic bacteria, with higher biovolume of Dolichospermum spp. and lower biovolume of N. spumigena, dinoflagellates, diatoms, ciliates and heterotrophic bacteria in reduced salinity. Although the salinity effects on diatoms were apparent, they could not clearly be separated from the influence of inorganic nutrients. We found a clear diurnal cycle in photosynthetic activity and pH, but without significant treatment effects. The same diurnal pattern was also observed in situ (pCO2, pH). Thus, considering the Baltic Proper, we do not expect any dramatic effects of increased pCO2 in combination with decreased salinity on the microplanktonic food web. However, long-term effects of the experimental treatments need to be further studied, and indirect effects of the lower salinity treatments could not be ruled out. Our study adds one piece to the complicated puzzle to reveal the combined effects of increased pCO2 and reduced salinity levels on the Baltic microplanktonic community.
Calcification in a marginal sea – influence of seawater [Ca2+] and carbonate chemistry on bivalve shell formation (update)
Published 15 March 2018 Science ClosedTags: Baltic, biological response, laboratory, mollusks, morphology
In estuarine coastal systems such as the Baltic Sea, mussels suffer from low salinity which limits their distribution. Anthropogenic climate change is expected to cause further desalination which will lead to local extinctions of mussels in the low saline areas. It is commonly accepted that mussel distribution is limited by osmotic stress. However, along the salinity gradient, environmental conditions for biomineralization are successively becoming more adverse as a result of reduced [Ca2+] and dissolved inorganic carbon (CT) availability. In larvae, calcification is an essential process starting during early development with formation of the prodissoconch I (PD I) shell, which is completed under optimal conditions within 2 days.
Experimental manipulations of seawater [Ca2+] start to impair PD I formation in Mytilus larvae at concentrations below 3 mM, which corresponds to conditions present in the Baltic at salinities below 8 g kg−1. In addition, lowering dissolved inorganic carbon to critical concentrations (< 1 mM) similarly affected PD I size, which was well correlated with calculated ΩAragonite and [Ca2+] [HCO3−] ∕ [H+]in all treatments. Comparing results for larvae from the western Baltic with a population from the central Baltic revealed a significantly higher tolerance of PD I formation to lowered [Ca2+] and [Ca2+] [HCO3−] ∕ [H+][H+] in the low saline adapted population. This may result from genetic adaptation to the more adverse environmental conditions prevailing in the low saline areas of the Baltic.
The combined effects of lowered [Ca2+] and adverse carbonate chemistry represent major limiting factors for bivalve calcification and can thereby contribute to distribution limits of mussels in the Baltic Sea.
Effect of temperature rise and ocean acidification on growth of calcifying tubeworm shells (Spirorbis spirorbis): an in situ benthocosm approach (update)
Published 12 March 2018 Science ClosedTags: annelids, Baltic, biological response, dissolution, field, growth, mesocosms, morphology, multiple factors, temperature
The calcareous tubeworm Spirorbis spirorbis is a widespread serpulid species in the Baltic Sea, where it commonly grows as an epibiont on brown macroalgae (genus Fucus). It lives within a Mg-calcite shell and could be affected by ocean acidification and temperature rise induced by the predicted future atmospheric CO2 increase. However, Spirorbis tubes grow in a chemically modified boundary layer around the algae, which may mitigate acidification. In order to investigate how increasing temperature and rising pCO2 may influence S. spirorbisshell growth we carried out four seasonal experiments in the Kiel Outdoor Benthocosms at elevated pCO2 and temperature conditions. Compared to laboratory batch culture experiments the benthocosm approach provides a better representation of natural conditions for physical and biological ecosystem parameters, including seasonal variations. We find that growth rates of S. spirorbis are significantly controlled by ontogenetic and seasonal effects. The length of the newly grown tube is inversely related to the initial diameter of the shell. Our study showed no significant difference of the growth rates between ambient atmospheric and elevated (1100 ppm) pCO2 conditions. No influence of daily average CaCO3 saturation state on the growth rates of S. spirorbis was observed. We found, however, net growth of the shells even in temporarily undersaturated bulk solutions, under conditions that concurrently favoured selective shell surface dissolution. The results suggest an overall resistance of S. spirorbis growth to acidification levels predicted for the year 2100 in the Baltic Sea. In contrast, S. spirorbis did not survive at mean seasonal temperatures exceeding 24 °C during the summer experiments. In the autumn experiments at ambient pCO2, the growth rates of juvenile S. spirorbis were higher under elevated temperature conditions. The results reveal that S. spirorbis may prefer moderately warmer conditions during their early life stages but will suffer from an excessive temperature increase and from increasing shell corrosion as a consequence of progressing ocean acidification.
Early development of the threespine stickleback in relation to water pH
Published 4 January 2018 Science ClosedTags: Baltic, biological response, fish, laboratory, morphology, mortality, reproduction
Ocean acidification is a growing environmental problem, and there is a need to investigate how the decreasing pH will affect marine organisms. Here we studied the effects of lowered pH on the growth and development of the threespine stickleback (Gasterosteus aculeatus) eggs. Adult fish, collected from the natural environment, were allowed to mate in aquaria and the newly produced eggs were incubated in an experiment. Eggs and larvae from ambient conditions (produced in the laboratory) were reared at three different pH concentrations (control: pH 7.8; and reduced pH treatments: pH 7.5 and 7.0) for 21 days in the laboratory. Dissolved oxygen concentration (8.1 ± 0.1 mg l−1) and temperature (18.6 ± 0.02°C) were monitored regularly. Then, egg diameter, larval length, weight and survival were measured. There was no relationship between egg diameter and pH or oxygen, but a negative relationship was found with temperature. Survival of larvae was not affected by pH or temperature, whereas dissolved oxygen concentration had a positive effect on number of survivors. The pH did not have a significant effect on the final larval length on day 21, but interacted significantly with dissolved oxygen. Higher temperatures were found to have a positive effect on the final larval length and weight. Larval weight, on the other hand, was not related to pH nor oxygen. Coastal zones are characterized by pH levels that fluctuate due to natural processes, such as upwelling and river runoff. Our results suggest that the threespine stickleback larvae are well adapted to the different pHs tested, and egg development will likely not be affected by decreasing pH, but even slight temperature and oxygen changes can have a great impact on the threespine stickleback development.
Continue reading ‘Early development of the threespine stickleback in relation to water pH’
Biogeographic vulnerability to ocean acidification and warming in a marine bivalve
Published 2 January 2018 Science ClosedTags: Baltic, biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, reproduction, temperature
- • Low pH reduces hatching in the Baltic, southern and northern East Atlantic clade.
- • Temperature rise alleviates pH effects on hatching success in the East Atlantic clades.
- • Smallest hatching sizes were found in low pH (< 7.5) calcite-undersaturated seawater.
- • Temperature rise reduces hatching size in the Baltic and northern East Atlantic clade.
- • The Gulf of Finland population appears most endangered in future high pCO2waters.
Anthropogenic CO2 emissions are rapidly changing seawater temperature, pH and carbonate chemistry. This study compares the embryonic development under high pCO2conditions across the south-north distribution range of the marine clam Limecola balthicain NW Europe. The combined effects of elevated temperature and reduced pH on hatching success and size varied strongly between the three studied populations, with the Gulf of Finland population appearing most endangered under the conditions predicted to occur by 2100. These results demonstrate that the assessment of marine faunal population persistence to future climatic conditions needs to consider the interactive effects of co-occurring physico-chemical alterations in seawater within the local context that determines population fitness, adaptation potential and the system resilience to environmental change.
DISCO – Drivers and impacts of coastal ocean acidification
Published 6 December 2017 Science ClosedTags: Baltic, biological response, chemistry, community composition, dissolution, field, multiple factors, North Atlantic, otherprocess, paleo, protists, salinity
Ocean acidification, mainly attributed to the increasing anthropogenic CO2 in the atmosphere, is characterised by a lowering pH together with a shift in the sea water carbonate chemistry toward lower concentration of carbonate ions. On the coasts, where the environmental variability is high due to natural and human impacts, ocean acidification mainly affects the frequency, magnitude, and duration of lower pH and lower calcium carbonate saturation events. Coastal ecosystems are adapted to environmental variability such as frequent changes in salinity, temperature, pH, oxygen levels and organic matter content. However, the effects of an increase of the range of this variability on coastal species, and especially on calcifiers, are still not clear. In this context, this thesis explores the impacts of coastal ocean acidification combined with other environmental stressors on benthic foraminifera.
In the Skagerrak-Baltic Sea region, foraminifera faunas varied along a strong gradient in terms of salinity, pH, and dissolved oxygen concentration, and species were adapted to local environmental stressors. However, the specimens of Ammonia spp. and Elphidium spp. observed in the south Baltic Sea were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralisation.
In a culture study, the coastal species Ammonia spp. and E. crispum were found to be resistant to dissolution under varying salinity and pH, which reflects the environmental variations in their natural habitats. However, their resistance to lower pH is decreased when cultured in brackish water conditions, and living decalcified specimens were also observed under a salinity of 5. This underlines the importance of a high salinity in the calcification process of foraminifera.
At the entrance of the Baltic Sea, environmental changes during the last 200 years were reconstructed using foraminiferal faunas. Four periods were identified with varying oxygen levels, salinity, organic matter content, and pollution with lower pH. This highlights that foraminiferal faunas were able to adapt to multiple environmental stressors.
This thesis concludes that, even if coastal species of foraminifera can tolerate extremely varying conditions in their environment on the short term, it is likely that tolerance thresholds will be passed for benthic ecosystems under the future increase in anthropogenic impacts such as coastal ocean acidification.
Further studies of micro-organisms such as foraminifera will be necessary to improve our understanding of past environmental changes and to put present and future changes into a larger context.
Continue reading ‘DISCO – Drivers and impacts of coastal ocean acidification’
The effects of multiple stressors on the distribution of coastal benthic foraminifera: a case study from the Skagerrak-Baltic Sea region
Published 27 November 2017 Science ClosedTags: abundance, Baltic, biological response, community composition, field, morphology, North Atlantic, otherprocess, protists
- • Foraminifera in the Skagerrak-Baltic region are adapted to the large environmental conditions.
- • Living dissolved Ammonia spp. and Elphidium spp. were found in the south Baltic Sea.
- • The combination of multiple factors influences the energy available for biogenic calcification.
- • Benthic ecosystems will be affected by an increase in the environmental variability.
Abstract
Coastal ecosystems are subjected to both large natural variability and increasing anthropogenic impact on environmental parameters such as changes in salinity, temperature, and pH. This study documents the distribution of living benthic foraminifera under the influence of multiple environmental stressors in the Skagerrak-Baltic Sea region. Sediment core tops were studied at five sites along a transect from the Skagerrak to the Baltic Sea, with strong environmental gradients, especially in terms of salinity, pH, calcium carbonate saturation and dissolved oxygen concentration in the bottom water and pore water. We found that living foraminiferal densities and species richness were higher at the Skagerrak station, where the general living conditions were relatively beneficial for Foraminifera, with higher salinity and Ωcalc in the water column and higher pH and oxygen concentration in the bottom and pore water. The most common species reported at each station reflect the differences in the environmental conditions between the stations. The dominant species were Cassidulina laevigata and Hyalinea balthica in the Skagerrak, Stainforthia fusiformis, Nonionella aff. stella and Nonionoides turgida in the Kattegat and N. aff. stella and Nonionellina labradorica in the Öresund. The most adverse conditions, such as low salinity, low Ωcalc, low dissolved oxygen concentrations and low pH, were noted at the Baltic Sea stations, where the calcareous tests of the dominant living taxa Ammonia spp. and Elphidium spp. were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralization. Even though Foraminifera are able to live in extremely varying environmental conditions, the present results suggest that the benthic coastal ecosystems in the studied region, which are apparently affected by an increase in the range of environmental variability, will probably be even more influenced by a future increase in anthropogenic impacts, including coastal ocean acidification and deoxygenation.
Mussel larvae modify calcifying fluid carbonate chemistry to promote calcification
Published 23 November 2017 Science ClosedTags: Baltic, biological response, calcification, dissolution, laboratory, mollusks, morphology, physiology
Understanding mollusk calcification sensitivity to ocean acidification (OA) requires a better knowledge of calcification mechanisms. Especially in rapidly calcifying larval stages, mechanisms of shell formation are largely unexplored—yet these are the most vulnerable life stages. Here we find rapid generation of crystalline shell material in mussel larvae. We find no evidence for intracellular CaCO3 formation, indicating that mineral formation could be constrained to the calcifying space beneath the shell. Using microelectrodes we show that larvae can increase pH and [CO32−] beneath the growing shell, leading to a ~1.5-fold elevation in calcium carbonate saturation state (Ωarag). Larvae exposed to OA exhibit a drop in pH, [CO32−] and Ωarag at the site of calcification, which correlates with decreased shell growth, and, eventually, shell dissolution. Our findings help explain why bivalve larvae can form shells under moderate acidification scenarios and provide a direct link between ocean carbonate chemistry and larval calcification rate.
Ship emissions and the use of current air cleaning technology: contributions to air pollution and acidification in the Baltic Sea
Published 19 October 2017 Science ClosedTags: Baltic, chemistry, modeling, regionalmodeling
The shipping sector is a significant contributor to emissions of air pollutants in marine and coastal regions. In order to achieve sustainable shipping, primarily through new regulations and techniques, greater knowledge of dispersion and deposition of air pollutants is required. Regional model calculations of the dispersion and concentration of sulfur, nitrogen, and particulate matter, as well as deposition of oxidized sulfur and nitrogen from the international maritime sector in the Baltic Sea and the North Sea, have been made for the years 2011 to 2013. The contribution from shipping is highest along shipping lanes and near large ports for concentration and dry deposition. Sulfur is the most important pollutant coupled to shipping. The contribution of both SO2 concentration and dry deposition of sulfur represented up to 80 % of the total in some regions. WHO guidelines for annual concentrations were not trespassed for any analysed pollutant, other than PM2.5 in the Netherlands, Belgium, and central Poland. However, due to the resolution of the numerical model, 50 km × 50 km, there may be higher concentrations locally close to intense shipping lanes. Wet deposition is more spread and less sensitive to model resolution. The contribution of wet deposition of sulfur and nitrogen from shipping was up to 30 % of the total wet deposition. Comparison of simulated to measured concentration at two coastal stations close to shipping lanes showed some underestimations and missed maximums, probably due to resolution of the model and underestimated ship emissions.
A change in regulation for maximum sulfur content in maritime fuel, in 2015 from 1 to 0.1 %, decreases the atmospheric sulfur concentration and deposition significantly. However, due to costs related to refining, the cleaning of exhausts through scrubbers has become a possible economic solution. Open-loop scrubbers meet the air quality criteria but their consequences for the marine environment are largely unknown. The resulting potential of future acidification in the Baltic Sea, both from atmospheric deposition and from scrubber water along the shipping lanes, based on different assumptions about sulfur content in fuel, scrubber usage, and increased shipping density has been assessed. The increase in deposition for different shipping and scrubber scenarios differs for the basins in the Baltic Sea, with highest potential of acidification in the southern basins with high traffic. The proportion of ocean-acidifying sulfur from ships increases when taking scrubber water into account and the major reason for increasing acidifying nitrogen from ships is increasing ship traffic. Also, with the implementation of emission control for nitrogen, the effect of scrubbers on acidification is evident. This study also generates a database of shipping and scrubber scenarios for atmospheric deposition and scrubber exhaust from the period 2011 to 2050.
Calcification in a marginal sea – influence of seawater [Ca2+] and carbonate chemistry on bivalve shell formation
Published 17 October 2017 Science ClosedTags: Baltic, biological response, laboratory, mollusks, morphology
In estuarine coastal systems such as the Baltic Sea, mussels suffer from low salinity which limits their distribution. Anthropogenic climate change is expected to cause further desalination which will lead to local extinctions of mussels in the low saline areas. It is commonly accepted that mussel distribution is limited by osmotic stress. However, along the salinity gradient environmental conditions for biomineralization are successively becoming more adverse as a result of reduced [Ca2+] and dissolved inorganic carbon (CT) availability. In larvae, calcification is an essential process starting during early development with formation of the prodissoconch I (PD I) shell which is completed under optimal conditions within 2 days.
Experimental manipulations of seawater [Ca2+] start to impair PD I formation in Mytilus larvae at concentrations below 3 mM, which corresponds to conditions present in the Baltic at salinities below 8 g kg-1. In addition, lowering dissolved inorganic carbon to critical concentrations (< 1 mM) similarly affected PD I size which was well correlated with calculated ΩAragonite and [Ca2+][HCO3–]/[H+] in all treatments. Comparing results for larvae from the western Baltic with a population from the central Baltic revealed significantly higher tolerance of PD I formation to lowered [Ca2+] and [Ca2+][HCO3–]/[H+] in the low saline adapted population. This may result from genetic adaptation to the more adverse environmental conditions prevailing in the low saline areas of the Baltic.
The combined effects of lowered [Ca2+] and adverse carbonate chemistry represent major limiting factors for bivalve calcification and can thereby contribute to distribution limits of mussels in the Baltic Sea.
Differing responses of the estuarine bivalve Limecola balthica to lowered water pH caused by potential CO2 leaks from a sub-seabed storage site in the Baltic Sea: an experimental study
Published 12 October 2017 Science ClosedTags: Baltic, biological response, mesocosms, mitigation, mollusks, morphology, performance, respiration
Highlights
- CO2-induced seawater acidification affected behavioral and physiological traits of Limecola balthica from the Baltic Sea.
- In response to hypercapnia, the bivalves approached the sediment surface and increased respiration rates.
- Lower seawater pH reduced shell weight and growth, and increased soft tissue weight that places L. balthica in a unique position among marine invertebrates.
Abstract
Sub-Seabed CCS is regarded as a key technology for the reduction of CO2 emissions, but little is known about the mechanisms through which leakages from storage sites impact benthic species. In this study, the biological responses of the infaunal bivalve Limecola balthica to CO2-induced seawater acidification (pH 7.7, 7.0, and 6.3) were quantified in 56-day mesocosm experiments. Increased water acidity caused changes in behavioral and physiological traits, but even the most acidic conditions did not prove to be fatal. In response to hypercapnia, the bivalves approached the sediment surface and increased respiration rates. Lower seawater pH reduced shell weight and growth, while it simultaneously increased soft tissue weight; this places L. balthica in a somewhat unique position among marine invertebrates.
The potential future contribution of shipping to acidification of the Baltic Sea
Published 11 October 2017 Science ClosedTags: Baltic, biogeochemistry, chemistry, field, modeling, regionalmodeling
International regulation of the emission of acidic sulphur and nitrogen oxides from commercial shipping has focused on the risks to human health, with little attention paid to the consequences for the marine environment. The introduction of stricter regulations in northern Europe has led to substantial investment in scrubbers that absorb the sulphur oxides in a counterflow of seawater. This paper examines the consequences of smokestack and scrubber release of acidic oxides in the Baltic Sea according to a range of scenarios for the coming decades. While shipping is projected to become a major source of strong acid deposition to the Baltic Sea by 2050, the long-term effect on the pH and alkalinity is projected to be significantly smaller than estimated from previous scoping studies. A significant contribution to this difference is the efficient export of surface water acidification to the North Sea on a timescale of 15–20 years.
Continue reading ‘The potential future contribution of shipping to acidification of the Baltic Sea’
Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios
Published 19 September 2017 Science ClosedTags: Baltic, biological response, chordata, crustaceans, echinoderms, laboratory, mollusks, multiple factors, North Atlantic, oxygen, physiology, respiration
Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation however; the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats such as sand and mud flats, seagrass beds, exposed and protected shorelines, and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high/low oxygen and low/high CO2; varying pCO2 of 450 and 1300 ppm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allows us to evaluate respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will results in multiplicative effects and focus attention on alleviating hypoxia in the region.
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Intense pCO2 and [O2] oscillations in a mussel-seagrass habitat: implications for calcification
Published 14 September 2017 Science ClosedTags: Baltic, biogeochemistry, chemistry, field
Numerous studies have been conducted on the effect of ocean acidification on calcifiers inhabiting nearshore benthic habitats, such as the blue mussel Mytilus edulis. The majority of these experiments was performed under stable CO2 partial pressure (pCO2), carbonate chemistry and oxygen (O2) levels, reflecting present or expected future open ocean conditions. Consequently, levels and variations occurring in coastal habitats, due to biotic and abiotic processes, were mostly neglected, even though these variations largely override global long-term trends. To highlight this hiatus and guide future research, state-of-the-art technologies were deployed to obtain high-resolution time series of pCO2 and [O2] on a mussel patch within a Zostera marina seagrass bed, in Kiel Bay (western Baltic Sea) in August and September 2013. Combining the in situ data with results of discrete sample measurements, a full seawater carbonate chemistry was derived using statistical models. An average pCO2 more than 50 % (~ 640 µatm) higher than current atmospheric levels was found right above the mussel patch. Diel amplitudes of pCO2 were large: 765 ± 310 (mean ± SD). Corrosive conditions for calcium carbonates (Ωarag and Ωcalc < 1) centered on sunrise were found, but the investigated habitat never experienced hypoxia throughout the study period. It is estimated that mussels experience conditions limiting calcification for 12–15 h per day, based on a regional calcium carbonate concentration physiological threshold. Our findings call for more extensive experiments on the impact of fluctuating corrosive conditions on mussels. We also stress the complexity of the interpretation of carbonate chemistry time series data in such dynamic coastal environments.
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