Posts Tagged 'Baltic'

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)

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 or low oxygen and low or high CO2; varying pCO2 of 450 and 1300 µatm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allowed us to evaluate respiration responses of species of contrasting habitats to single and multiple stressors. Results show that respiratory responses 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 result in multiplicative effects and focus attention on alleviating hypoxia in the region.

Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)’

The effects of low seawater pH on energy storage and heat shock protein 70 expression in a bivalve Limecola balthica

Highlights

• Seawater acidification affected gross biochemical composition of the bivalve Limecola balthica to a limited extent.
• Moderate hypercapnia (pH 7.0) induced elevated catabolism of carbohydrates including glycogen and lipids.
• Biochemical responses did not involve proteins suggesting that amino acids were not utilized as metabolic substrates.
• Clams demonstrated broad tolerance to reduced seawater pH presumably as pre-adaptation to CO2 variations in the environment.

Abstract

Though biological consequences of CCS (Carbon Capture and Storage) implementation into the marine environment have received substantial research attention, the impact of potential CO2 leakage on benthic infauna in the Baltic Sea remained poorly recognized. This study quantified medium-term (56-day laboratory exposure) effects of CO2-induced seawater acidification (pH 7.7, 7.0 and 6.3) on energetic reserves and heat-shock protein HSP70 expression of adult bivalve Limecola balthica from the southern Baltic. While no clear impact was evident in the most acidic treatment (pH 6.3), moderate seawater hypercapnia (pH 7.0) induced elevated catabolism of high caloric reserves (carbohydrates including glycogen and lipids) in order to provide energy to cover enhanced metabolic requirements for acid-base regulation. Biochemical response did not involve, however, breakdown of proteins, suggesting that they were not utilized as metabolic substrates. As indicated also by subtle variations in the chaperone protein HSP70, the clams demonstrated high CO2 tolerance, presumably through development of efficient defensive/compensatory mechanisms during their larval and/or ontogenic life stages.

Continue reading ‘The effects of low seawater pH on energy storage and heat shock protein 70 expression in a bivalve Limecola balthica’

Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming

Nitrogen fixation is a key source of nitrogen in the Baltic Sea which counteracts nitrogen loss processes in the deep anoxic basins. Laboratory and field studies have indicated that single-strain nitrogen-fixing (diazotrophic) cyanobacteria from the Baltic Sea are sensitive to ocean acidification and warming, 2 drivers of marked future change in the marine environment. Here, we enclosed a natural plankton community in 12 indoor mesocosms (volume ~1400 l) and manipulated partial pressure of carbon dioxide ( pCO2) in seawater to yield 6 CO2 treatments with 2 different temperature treatments (16.6°C and 22.4°C, pCO2 range = 360-2030 µatm). We followed the filamentous, heterocystous diazotrophic cyanobacteria community (Nostocales, primarily Nodularia spumigena) over 4 wk. Our results indicate that heterocystous diazotrophic cyanobacteria may become less competitive in natural plankton communities under ocean acidification. Elevated CO2 had a negative impact on Nodularia sp. biomass, which was exacerbated by warming. Our results imply that Nodularia sp. may contribute less to new nitrogen inputs in the Baltic Sea in the future.

Continue reading ‘Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming’

Shift towards larger diatoms in a natural phytoplankton assemblage under combined high-CO2 and warming conditions

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.

Continue reading ‘Shift towards larger diatoms in a natural phytoplankton assemblage under combined high-CO2 and warming conditions’

Anomaly of total boron concentration in the brackish waters of the Baltic Sea and its consequence for the CO2 system calculations

Highlights

• 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 COconcentration) 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 pCOconditions (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 COsystem calculations for the Baltic Sea and likely for other brackish systems.

Continue reading ‘Anomaly of total boron concentration in the brackish waters of the Baltic Sea and its consequence for the CO2 system calculations’

Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors

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.

Continue reading ‘Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors’

Shallow water carbonate sediments of the Galapagos archipelago: ecologically sensitive biofacies in a transitional oceanographic environment

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.

Continue reading ‘Shallow water carbonate sediments of the Galapagos archipelago: ecologically sensitive biofacies in a transitional oceanographic environment’


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