Posts Tagged 'Baltic Sea'

Biokinetics of 110m Ag in Baltic shrimp Palaemon adspersus under elevated pCO2

Ocean acidification impacts the physiology of crustaceans as well as marine calcifiers although most of the hitherto studies has focused on calcifiers. Bioconcentration of elements in a marine animal depends on seawater chemistry and the animal’s physiology. Here we studied biokinetics and body distribution of Ag in Baltic shrimp Palaemon adspersus for 47 days by using radiotracer method (110mAg). The bioconcentration of 110mAg was assessed under three pCO2 levels: 370, 795 and 1634 μatm. Uptake rate constants of 110mAg were inversely related to pH (3.1 at pH: 8.1, 4.2 at pH: 7.8 and 4.9 at pH: 7.5). A higher percentage of Ag accumulated in edible parts in the shrimps reared in acidified seawater compared to control. The moulting frequency was significantly higher in acidified seawater conditions compared to the control condition. The results of this study suggest that seawater acidification may partly modify Ag bioconcentration in Baltic shrimp Palaemon adspersus as well as energy-demanding physiological processes like moulting.

Continue reading ‘Biokinetics of 110m Ag in Baltic shrimp Palaemon adspersus under elevated pCO2’

A system for the determination of surface water pCO2 in a highly variable environment, exemplified in the southern Baltic Sea

Highlights

  • The system for pCO2 measurements, data storage and ship-to-shore transmission is presented.
  • In the open Baltic Sea waters the pCO2 measurements obtained an accuracy of ±1.3 µatm met the state-of-the-art requirements (±2.0 µatm).
  • We discuss redefining requirements for quality control and assurance for pCO2 measurements in the coastal zone.

Abstract

Measurement of pCO2 in highly dynamic coastal zones such as the southern Baltic Sea presents many challenges. In this study, we designed a system to measure pCO2 and then validated it in a series of laboratory and seagoing tests. The fast response time of the system was shown to provide a better resolution of CO2 system gradients. In the open waters of the Baltic Sea, the accuracy of the pCO2 measurements (±1.3 µatm) met the requirements of the ICOS (±2.0 µatm). In the coastal zone, there was less consistency between pCO2, DIC and pH measurements, suggesting the need to redefine the quality assurance and control requirements for the measurement of pCO2 in dynamic regions.

Continue reading ‘A system for the determination of surface water pCO2 in a highly variable environment, exemplified in the southern Baltic Sea’

Growth response of calcifying marine epibionts to biogenic pH fluctuations and global ocean acidification scenarios

In coastal marine environments, physical and biological forces can cause dynamic pH fluctuations from microscale (diffusive boundary layer [DBL]) up to ecosystem‐scale (benthic boundary layer [BBL]). In the face of ocean acidification (OA), such natural pH variations may modulate an organism’s response to OA by providing temporal refugia. We investigated the effect of pH fluctuations, generated by the brown alga Fucus serratus‘ biological activity, on the calcifying epibionts Balanus improvisus and Electra pilosa under OA. For this, both epibionts were grown on inactive and biologically active surfaces and exposed to (1) constant pH scenarios under ambient (pH 8.1) or OA conditions (pH 7.7), or (2) oscillating pH scenarios mimicking BBL conditions at ambient (pH 7.7–8.6) or OA scenarios (pH 7.4–8.2). Furthermore, all treatment combinations were tested at 10°C and 15°C. Against our expectations, OA treatments did not affect epibiont growth under constant or fluctuating (BBL) pH conditions, indicating rather high robustness against predicted OA scenarios. Furthermore, epibiont growth was hampered and not fostered on active surfaces (fluctuating DBL conditions), indicating that fluctuating pH conditions of the DBL with elevated daytime pH do not necessarily provide temporal refugia from OA. In contrast, results indicate that factors other than pH may play larger roles for epibiont growth on macrophytes (e.g., surface characteristics, macrophyte antifouling defense, or dynamics of oxygen and nutrient concentrations). Warming enhanced epibiont growth rates significantly, independently of OA, indicating no synergistic effects of pH treatments and temperature within their natural temperature range.

Continue reading ‘Growth response of calcifying marine epibionts to biogenic pH fluctuations and global ocean acidification scenarios’

Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community

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.

Continue reading ‘Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community’

Impact of seawater carbonate chemistry on the calcification of marine bivalves (update)

Bivalve calcification, particularly of the early larval stages, is highly sensitive to the change in ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no effects and [HCO3] and pH had only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. An equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

Continue reading ‘Impact of seawater carbonate chemistry on the calcification of marine bivalves (update)’

Impact of seawater carbonate chemistry on the calcification of marine bivalves

Bivalve calcification, particular of the early larval stages is highly sensitive to the change of ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no and [HCO3−] and pH only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3−] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3−] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. Therefore, the availability of [HCO3−] combined with favorable environmental pH determines calcification rate and an equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

Continue reading ‘Impact of seawater carbonate chemistry on the calcification of marine bivalves’

Metabolic rate and activity of blue mussel Mytilus edulis trossulus under short-term exposure to carbon dioxide-induced water acidification and oxygen deficiency

This work investigated the effect of carbon dioxide-induced decreased water pH (8.1 – control, 7.5 and 7.0), oxygen saturation (~100% and ~20%) and the combination of both factors on the behaviour (gaping activity) and the total metabolic rate of blue mussel Mytilus edulis trossulus from the southern Baltic Sea. Heat dissipation measurements were carried out in a Calvet-type isothermal twin calorimeter equipped with a flow-through system. The resting metabolic rate was not significantly (p > 0.05) affected by pH or oxygen saturation. Neither was there significant (p > 0.05) effect of the interaction of both factors on this process. The high inter-individual variability in behaviour affected the value of maximal recorded activity and duration of activity peaks connected with shell gaping behaviour. In some mussels, they were short and appeared periodically, and other individuals were inactive or exhibited temporal activity terms of different duration. The lowered oxygen saturation significantly (p < 0.05) affected the time spent on activity. However, there was no effect (p > 0.05) of lowered pH on this parameter, which indicates that oxygen deficiency may affect the Baltic population of M. edulis trossulus more seriously than acidification.

Continue reading ‘Metabolic rate and activity of blue mussel Mytilus edulis trossulus under short-term exposure to carbon dioxide-induced water acidification and oxygen deficiency’

Juvenile sea stars exposed to acidification decrease feeding and growth with no acclimation potential

Ocean acidification has the potential to affect growth and calcification of benthic marine invertebrates, particularly during their early life history. We exposed field-collected juveniles of Asterias rubens from Kiel Fjord (western Baltic Sea) to 3 seawater CO2 partial pressure (pCO2) levels (ranging from around 650 to 3500 µatm) in a long-term (39 wk) and a short-term (6 wk) experiment. In both experiments, survival and calcification were not affected by elevated pCO2. However, feeding rates decreased strongly with increasing pCO2, while aerobic metabolism and NH4+ excretion were not significantly affected by CO2 exposure. Consequently, high pCO2 reduced the scope for growth in A. rubens. Growth rates decreased substantially with increasing pCO2 and were reduced even at pCO2 levels occurring in the habitat today (e.g. during upwelling events). Sea stars were not able to acclimate to higher pCO2, and growth performance did not recover during the long-term experiment. Therefore, the top-down control exerted by this keystone species may be diminished during periods of high environmental pCO2 that already occur occasionally and will be even higher in the future. However, some individuals were able to grow at high rates even at high pCO2, indicating potential for rapid adaption. The selection of adapted specimens of A. rubens in this seasonally acidified habitat may lead to higher CO2 tolerance in adult sea stars of this population compared to the juvenile stage. Future studies need to address the synergistic effects of multiple stressors such as acidification, warming and reduced salinity, which will simultaneously impact the performance of sea stars in this habitat.

Continue reading ‘Juvenile sea stars exposed to acidification decrease feeding and growth with no acclimation potential’

Effect on pCO2 by phytoplankton uptake of dissolved organic nutrients in the Central and Northern Baltic Sea, a model study

Dissolved organic matter (DOM) has been added to an existing biogeochemical model and the phytoplankton were allowed to utilize the dissolved organic nutrients for primary production. The results show typical vertical structures for dissolved organic carbon (DOC), and improved or maintained model skill for both mean vertical profiles and mean seasonal variation of biogeochemical variables, evaluated by objective skill metrics. Due to scarce DOM measurements in the Baltic Sea it was hard to validate the new variables, but the model can recreate the general magnitude and distribution of terrestrial and in situ produced DOC, DON, and DOP, as far as we know them. The improvements are especially clear for the total nutrient levels and in recreating the biological drawdown of CO2 in the Eastern Gotland basin. Without phytoplankton uptake of dissolved organic nitrogen and phosphate, CO2 assimilation is lower during the summer months and the partial pressure of CO2 increases by about 200 μatm in the Eastern Gotland Basin, while in the Bothnian Bay, both the duration and magnitude of CO2 assimilation are halved. Thus the phytoplankton uptake of dissolved organic nutrients lowers pCO2 in both basins. Variations in the river transported DOM concentration mainly affect the magnitude of the summer cyanobacteria bloom.

Continue reading ‘Effect on pCO2 by phytoplankton uptake of dissolved organic nutrients in the Central and Northern Baltic Sea, a model study’

Multiple stressors threatening the future of the Baltic Sea–Kattegat marine ecosystem: Implications for policy and management actions

The paper discusses the combined effects of ocean acidification, eutrophication and climate change on the Baltic Sea and the implications for current management strategies. The scientific basis is built on results gathered in the BONUS+ projects Baltic-C and ECOSUPPORT. Model results indicate that the Baltic Sea is likely to be warmer, more hypoxic and more acidic in the future. At present management strategies are not taking into account temporal trends and potential ecosystem change due to warming and/or acidification, and therefore fulfilling the obligations specified within the Marine Strategy Framework Directive, OSPAR and HELCOM conventions and national environmental objectives may become significantly more difficult. The paper aims to provide a basis for a discussion on the effectiveness of current policy instruments and possible strategies for setting practical environmental objectives in a changing climate and with multiple stressors.

Continue reading ‘Multiple stressors threatening the future of the Baltic Sea–Kattegat marine ecosystem: Implications for policy and management actions’


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