Reduced seawater pH due to elevated carbon dioxide (CO2), a process known as ocean acidification (OA), is a globally significant environmental issue. OA is predicted to influence a range of ecosystem processes, but little is known about how changing seawater carbon chemistry could influence the extent and impacts of epiphytism. In the brackish Baltic Sea, increased epiphytism is associated with coastal eutrophication and the potential for OA to interact with this relationship remains unclear. This study focuses on slow-growing perennial algae Fucus vesiculosus—which is one of the most important habitat-forming species in the Baltic Sea—and two of its most common and abundant filamentous epiphytes Ceramium tenuicorne and Pylaiella littoralis. Material for this study was collected from Estonian coastal waters. The aim of the research was to determine which carbon acquisition strategies these species possess, which could indicate how they respond to predicted changes in seawater chemistry due to elevated CO2. Carbon-use strategies in macroalgae were determined by analyzing natural carbon isotope signatures (δ13C), pH drift experiments, and photosynthesis vs. dissolved inorganic carbon (P vs. DIC) curves. Our results showed that although F. vesiculosus and its filamentous epiphytes all possess a carbon concentrating mechanism (CCM), the potential species-specific variation in the CCMs operation will favor C. tenuicorne over F. vesiculosus and P. littoralis in a future high CO2 world.
Posts Tagged 'Baltic'
Could ocean acidification influence epiphytism? A comparison of carbon-use strategies between Fucus vesiculosus and its epiphytes in the Baltic Sea
Published 25 November 2019 Science ClosedTags: algae, Baltic, biogeochemistry, biological response, laboratory, photosynthesis
Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem
Published 21 November 2019 Science ClosedTags: abundance, algae, Baltic, biological response, BRcommunity, community composition, crustaceans, field, laboratory, mesocosms, mollusks, morphology, multiple factors, otherprocess, performance, photosynthesis, reproduction, temperature, zooplankton
The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.
Ocean acidification may threaten a unique seaweed community and associated industry in the Baltic Sea
Published 28 October 2019 Science ClosedTags: abundance, algae, Baltic, biogeochemistry, biological response, otherprocess, photosynthesis
Wild harvest of seaweed supports small-scale, high-value industries in a number of regions in the world. Information is lacking on how increasing carbon dioxide (CO2) concentrations in seawater could impact seaweeds in wild harvest situations. This study focuses on a mixed unattached loose-lying red algal community of Furcellaria lumbricalis in close association with Coccotylus truncatus that is found in the West Estonian Archipelago Sea, NE Baltic Sea. In Estonian coastal waters, the wild harvest of F. lumbricalis started in 1960s and it has since been used as raw material for furcellaran production. The aim of this study was to determine how ocean acidification may impact the balance of these two red algal species in the community. Mechanistic assessment of the carbon physiology of F. lumbricalis and C. truncatus was used to predict productivity and competitive interactions between these species in a high-CO2 world. Carbon use strategies in macroalgae were determined by analysing the natural abundances of carbon isotopes (δ13C), pH drift experiments and photosynthesis vs. dissolved inorganic carbon (DIC) curves. Photosynthesis of F. lumbricalis (operating with a CO2 concentrating mechanism or CCM) performed worse along the broader range of DIC concentrations compared to C. truncatus (non-CCM), especially those characterized under future climate conditions. Therefore, changing seawater carbon chemistry through ocean acidification has the potential to influence the balance of F. lumbricalis and C. truncatus in the community and the efficiency of the wild harvest of this community and the quality of product provided.
Sensitivities to global change drivers may correlate positively or negatively in a foundational marine macroalga
Published 16 October 2019 Science ClosedTags: algae, Baltic, biological response, growth, laboratory, mesocosms, mortality, multiple factors, nutrients, oxygen, reproduction, temperature
Ecological impact of global change is generated by multiple synchronous or asynchronous drivers which interact with each other and with intraspecific variability of sensitivities. In three near-natural experiments, we explored response correlations of full-sibling germling families of the seaweed Fucus vesiculosus towards four global change drivers: elevated CO2 (ocean acidification, OA), ocean warming (OW), combined OA and warming (OAW), nutrient enrichment and hypoxic upwelling. Among families, performance responses to OA and OW as well as to OAW and nutrient enrichment correlated positively whereas performance responses to OAW and hypoxia anti-correlated. This indicates (i) that families robust to one of the three drivers (OA, OW, nutrients) will also not suffer from the two other shifts, and vice versa and (ii) families benefitting from OAW will more easily succumb to hypoxia. Our results may imply that selection under either OA, OW or eutrophication would enhance performance under the other two drivers but simultaneously render the population more susceptible to hypoxia. We conclude that intraspecific response correlations have a high potential to boost or hinder adaptation to multifactorial global change scenarios.
Seasonal interactive effects of pCO2 and irradiance on the ecophysiology of brown macroalga Fucus vesiculosus L.
Published 27 June 2019 Science ClosedTags: algae, Baltic, biogeochemistry, biological response, growth, laboratory, light, multiple factors, photosynthesis
Stochastic upwelling of seawater in the Baltic Sea from the deep, anoxic bottoms may bring low-pH water rich in CO2 close to the surface. Such events may become more frequent with climate change and ongoing ocean acidification (OA). Photoautotrophs, such as macroalgae, which are important foundation species, have been proposed to benefit from increased carbon availability due to reduced energetic cost in carbon acquisition. However, the exact effects of CO2 fertilization may depend on the ambient light environment, as photosynthesis rates depend on available irradiance. In this experimental study, interacting effects of CO2 addition and irradiance on the habitat-forming macroalga Fucus vesiculosus were investigated during two seasons – winter and summer – in the northern Baltic Sea. Growth rates remained unaffected by CO2 or irradiance during both seasons, suggesting that direct effects of elevated CO2 on mature F. vesiculosus are small. Increases in CO2 affected algal elemental ratios by increasing carbon and decreasing nitrogen content, with resulting changes in the C:N ratio, but only in winter. In summer, chlorophyll a content increased under low irradiance. Increases in CO2 caused a decline in light-harvesting efficiency (decrease in Fv/Fm and α) under high irradiance in summer, and conversely increased α under low irradiance. High irradiance caused increases in the maximum relative electron transport rate (rETRmax) in summer, but not in winter. Differences between winter and summer indicate that F. vesiculosus responses to CO2 and irradiance are season-specific. Increases in carbon content during winter could indicate slightly positive effects of CO2 addition in the long run if the extra carbon gained may be capitalized in growth. The results of this study suggest that increases in CO2, either through upwelling or OA, may have positive effects on F. vesiculosus, but these effects are probably small.
Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2
Published 13 May 2019 Science ClosedTags: abundance, Baltic, biological response, growth, laboratory, morphology, multiple factors, otherprocess, photosynthesis, prokaryotes, temperature
Temperature and CO2 levels are projected to increase in the future, with consequences for carbon and nutrient cycling in brackish environments, such as the Baltic Sea. Moreover, filamentous cyanobacteria are predicted to be favored over other phytoplankton groups under these conditions. Under a 12-day outdoor experiment, we examined the effect on a natural phytoplankton spring bloom community of elevated temperature (from 1°C to 4°C) and elevated pCO2 (from 390 to 970 μatm). No effects of elevated pCO2 or temperature were observed on phytoplankton biovolumes, but a significantly higher photosystem II activity was observed at elevated temperature after 9 days. In addition, three species of diazotrophic filamentous cyanobacteria were inoculated to test their competitive capacity under spring bloom conditions. The toxic cyanobacterium Nodularia spumigena exhibited an average specific growth rate of 0.10 d−1 by the end of the experiment, indicating potential prevalence even during wintertime in the Baltic Sea. Generally, none of the inoculated cyanobacteria species were able to outcompete the natural phytoplankton species at temperatures ≤4°C. No direct effects were found on heterotrophic bacteria. This study demonstrates the highly efficient resistance towards short-term (12 days) changes in abiotic factors by the natural Baltic Sea spring bloom community.
Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales
Published 12 April 2019 Science ClosedTags: algae, Baltic, biological response, laboratory, morphology, performance
Fucus vesiculosus is a keystone species in the North Atlantic and Baltic Sea; any changes in its distribution or physical structure could have broad-reaching implications on many coastal ecosystems. It is therefore important to understand both how this important species has evolved in the past and adapted to historical changes in the environment but also how future environmental stress and changes will affect this species. When stress, for example from environmental change, affects a population, traits that make individuals more likely to survive will remain in the population. This is the fundamental basis of evolution, occurring over both short and long time scales. Climate change is
liable to exert a strong selective pressure on many species as it changes the environment inhabited by those species.
Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification
Published 11 March 2019 Science ClosedTags: Baltic, biological response, fish, individualmodeling, modeling, multiple factors, regionalmodeling, socio-economy, temperature
Highlights
• Ocean warming and acidification (OAW) will drastically decrease cod fishing opportunities in the Baltic.
• Ecological-economic modeling shows high losses in catch, and profits due to OAW.
• There is a high risk of cod stock collapse under mid-term climate change.
• Improved management could temporarily counteract OAW stressors.
• Adaptation includes a reduction in fishing mortality, and increased mesh size.
Abstract
Human-induced climate change such as ocean warming and acidification, threatens marine ecosystems and associated fisheries. In the Western Baltic cod stock socio-ecological links are particularly important, with many relying on cod for their livelihoods. A series of recent experiments revealed that cod populations are negatively affected by climate change, but an ecological-economic assessment of the combined effects, and advice on optimal adaptive management are still missing. For Western Baltic cod, the increase in larval mortality due to ocean acidification has experimentally been quantified. Time-series analysis allows calculating the temperature effect on recruitment. Here, we include both processes in a stock-recruitment relationship, which is part of an ecological-economic optimization model. The goal was to quantify the effects of climate change on the triple bottom line (ecological, economic, social) of the Western Baltic cod fishery. Ocean warming has an overall negative effect on cod recruitment in the Baltic. Optimal management would react by lowering fishing mortality with increasing temperature, to create a buffer against climate change impacts. The negative effects cannot be fully compensated, but even at 3 °C warming above the 2014 level, a reduced but viable fishery would be possible. However, when accounting for combined effects of ocean warming and acidification, even optimal fisheries management cannot adapt to changes beyond a warming of +1.5° above the current level. Our results highlight the need for multi-factorial climate change research, in order to provide the best available, most realistic, and precautionary advice for conservation of exploited species as well as their connected socio-economic systems.
A new mesocosm system to study the effects of environmental variability on marine species and communities
Published 8 March 2019 Science ClosedTags: Baltic, BRcommunity, laboratory, mesocosms, mollusks, morphology, multiple factors, oxygen, temperature
Climate change will shift mean environmental conditions and also increase the frequency and intensity of extreme events, exerting additional stress on ecosystems. While field observations on extremes are emerging, experimental evidence of their biological consequences is rare. Here, we introduce a mesocosm system that was developed to study the effects of environmental variability of multiple drivers (temperature, salinity, pH, light) on single species and communities at various temporal scales (diurnal ‐ seasonal): the Kiel Indoor Benthocosms (KIBs). Both, real‐time offsets from field measurements or various dynamic regimes of environmental scenarios, can be implemented, including sinusoidal curve functions at any chosen amplitude or frequency, stochastic regimes matching in situ dynamics of previous years and modeled extreme events. With temperature as the driver in focus, we highlight the strengths and discuss limitations of the system. In addition, we examined the effects of different sinusoidal temperature fluctuation frequencies on mytilid mussel performance. High‐frequency fluctuations around a warming mean (+2°C warming, ± 2°C fluctuations, wavelength = 1.5 d) increased mussel growth as did a constant warming of 2°C. Fluctuations at a lower frequency (+2 and ± 2°C, wavelength = 4.5 d), however, reduced the mussels’ growth. This shows that environmental fluctuations, and importantly their associated characteristics (such as frequency), can mediate the strength of global change impacts on a key marine species. The here presented mesocosm system can help to overcome a major short‐coming of marine experimental ecology and will provide more robust data for the prediction of shifts in ecosystem structure and services in a changing and fluctuating world.
Sedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea
Published 30 January 2019 Science ClosedTags: Baltic, biogeochemistry, chemistry, modeling, regionalmodeling
Enhanced release of alkalinity from the seafloor, principally driven by anaerobic degradation of organic matter under low-oxygen conditions and associated secondary redox reactions, can increase the carbon dioxide (CO2) buffering capacity of seawater and therefore oceanic CO2 uptake. The Baltic Sea has undergone severe changes in oxygenation state and total alkalinity (TA) over the past decades. The link between these concurrent changes has not yet been investigated in detail. A recent system-wide TA budget constructed for the past 50 years using BALTSEM, a coupled physical–biogeochemical model for the whole Baltic Sea area revealed an unknown TA source. Here we use BALTSEM in combination with observational data and one-dimensional reactive-transport modeling of sedimentary processes in the Fårö Deep, a deep Baltic Sea basin, to test whether sulfate (SO2−4) reduction coupled to iron (Fe) sulfide burial can explain the missing TA source in the Baltic Proper. We calculated that this burial can account for up to 26 % of the missing source in this basin, with the remaining TA possibly originating from unknown river inputs or submarine groundwater discharge. We also show that temporal variability in the input of Fe to the sediments since the 1970s drives changes in sulfur (S) burial in the Fårö Deep, suggesting that Fe availability is the ultimate limiting factor for TA generation under anoxic conditions. The implementation of projected climate change and two nutrient load scenarios for the 21st century in BALTSEM shows that reducing nutrient loads will improve deep water oxygen conditions, but at the expense of lower surface water TA concentrations, CO2 buffering capacities and faster acidification. When these changes additionally lead to a decrease in Fe inputs to the sediment of the deep basins, anaerobic TA generation will be reduced even further, thus exacerbating acidification. This work highlights that Fe dynamics plays a key role in the release of TA from sediments where Fe sulfide formation is limited by Fe availability, as exemplified by the Baltic Sea. Moreover, it demonstrates that burial of Fe sulfides should be included in TA budgets of low-oxygen basins.
Ocean acidification research in Estonia: challenges and opportunities
Published 28 January 2019 Science ClosedTags: Baltic, biological response, chemistry, review
Anthropogenic carbon dioxide (CO2) emissions to the atmosphere are causing a decrease in the average surface global ocean pH, also known as ocean acidification. Our understanding of the global impacts of ocean acidification on marine ecosystems is growing rapidly. In the Baltic Sea area, however, the vast majority of studies have so far focused on the effects of eutrophication on marine ecosystems. Less is known about the changing carbon chemistry due to increasing CO2 concentrations in seawater, which could influence Baltic Sea marine ecosystems. The present study focuses on Estonian waters, located in the northeastern part of the Baltic Sea. The aim of this article is to summarize the existing knowledge on ocean acidification research in Estonia as well as to highlight the opportunities and challenges for future research. One key challenge is that the present national marine monitoring of carbonate chemistry in Estonia is not following best practices. The lack of proper seawater carbonate chemistry data in the study area is strongly limiting the ability to design relevant biological experiments and forecast future changes. So far, the effect of ocean acidification on marine biota in the Estonian coastal waters is mostly unexplored. However, several sensors for measurements of carbonate chemistry variables as well as laboratory facilities for conducting ocean acidification experiments are now available.
Continue reading ‘Ocean acidification research in Estonia: challenges and opportunities’
Ocean acidification in the Baltic Sea: involved processes, metrology of pH in brackish waters, and calcification under fluctuating conditions
Published 11 January 2019 Science ClosedTags: algae, Baltic, methods, review
The oceanic uptake of anthropogenic CO2 emissions counteracts global warming, but comes at the cost of Ocean Acidification, which is a threat to many marine organisms. In the Baltic Sea, the acidification process and its impact could so far not be quantified due to a lack of appropriate pH measurement techniques and the large pH variability. Looking back, in the first focus of this study acidification scenarios are derived from a detailed analysis of past alkalinity trends in the Baltic Sea water, which are put into context of the atmospheric CO2 forcing. In the second focus, the scientific basis for meaningful pH measurements in brackish waters is formed. Therefore, pH buffer solutions are characterized as primary standards and used to calibrate high-quality spectrophotometric pH measurements. In the last focus, pH fluctuations in benthic ecosystems are quantified. The importance of periods with high pH, during which organisms can maintain calcification rates even under acidified conditions, are highlighted.
Ecological and functional consequences of coastal ocean acidification: perspectives from the Baltic-Skagerrak System
Published 5 December 2018 Science ClosedTags: Baltic, biogeochemistry, biological response, chemistry, North Atlantic, review
Ocean temperatures are rising; species are shifting poleward, and pH is falling (ocean acidification, OA). We summarise current understanding of OA in the brackish Baltic-Skagerrak System, focussing on the direct, indirect and interactive effects of OA with other anthropogenic drivers on marine biogeochemistry, organisms and ecosystems. Substantial recent advances reveal a pattern of stronger responses (positive or negative) of species than ecosystems, more positive responses at lower trophic levels and strong indirect interactions in food-webs. Common emergent themes were as follows: OA drives planktonic systems toward the microbial loop, reducing energy transfer to zooplankton and fish; and nutrient/food availability ameliorates negative impacts of OA. We identify several key areas for further research, notably the need for OA-relevant biogeochemical and ecosystem models, and understanding the ecological and evolutionary capacity of Baltic-Skagerrak ecosystems to respond to OA and other anthropogenic drivers.
Fast and stable optical pH sensor materials for oceanographic applications
Published 27 November 2018 Science ClosedTags: Baltic, chemistry, field, methods
Highlights
• 4 novel optical sensor materials for pH measurements in seawater.
• 3 strategies for covalent immobilization of pH indicator into a hydrogel.
• Fast response times, excellent stability and low cross sensitivities to temperature and salinity.
• Successful application demonstration in several deployments.
Abstract
The study reports preparation and detailed comparison of four new pH sensor materials for seawater measurements. The composition of the sensors is optimized in several iterations to ensure optimal dynamic range, fast response time at low temperatures, low cross-sensitivities to temperature (dpKa/dT ∼ -0.013 pH units/K) and negligible cross sensitivity to ionic strength above salinity 15 PSU. The first generation (material “pH-1″) utilizes a pH indicator which is physically entrapped into a polyurethane hydrogel. This material shows satisfactory performance only at comparably high temperatures with response times being extremely long at low temperatures (t95 > 2 h at 5 °C). The three other materials utilize cross-linked hydrophilic polymers based on poly(acryloylmorpholine) with indicator dye covalently coupled to the polymer. They feature fast response times at low temperatures (t90 < 1 min at 5 °C). Moreover, the last two generations (“pH-3″ and “pH-4″) showed no drift over 54 days at 10 °C and only a drift of 0.003 pH units/day at 25 °C. Although the stability and the sensing properties of these materials are rather similar, the synthetic effort varies considerably. The material of the fourth generation “pH-4″ explores a novel approach of covalent coupling via B–O linkage and is characterized by low synthetic effort and the pKa value optimal for seawater measurements (8.05 at 20 °C). Importantly, all new sensor materials are spectrally compatible to a recently presented seawater optode system for combined pH, pO2 and pCO2 measurements which facilitates their application in marine environment.
Continue reading ‘Fast and stable optical pH sensor materials for oceanographic applications’
Impact of environmental hypercapnia on fertilization success rate and the early embryonic development of the clam Limecola balthica (Bivalvia, Tellinidae) from the southern Baltic Sea – a potential CO2 leakage case study
Published 18 September 2018 Science ClosedTags: Baltic, biological response, laboratory, mitigation, mollusks, morphology, reproduction
Highlights
- • Fertilization success of Limecola balthica drops along decreasing pH gradient.
- • Low pH causes delays of early embryonic development of the Baltic clam.
- • L. balthica embryos develop aberrations of early cleavages in CO2-rich environment.
- • CO2 leakage from CCS site may affect population’s size by impeding its reproduction.
Abstract
Carbon capture and storage technology was developed as a tool to mitigate the increased emissions of carbon dioxide by capture, transportation, injection and storage of CO2 into subterranean reservoirs. There is, however, a risk of future CO2 leakage from sub-seabed storage sites to the sea-floor sediments and overlying water, causing a pH decrease. The aim of this study was to assess effects of CO2-induced seawater acidification on fertilization success and early embryonic development of the sediment-burrowing bivalve Limecola balthica L. from the Baltic Sea. Laboratory experiments using a CO2 enrichment system involved three different pH variants (pH 7.7 as control, pH 7.0 and pH 6.3, both representing environmental hypercapnia). The results showed significant fertilization success reduction under pH 7.0 and 6.3 and development delays at 4 and 9 h post gamete encounter. Several morphological aberrations (cell breakage, cytoplasm leakages, blastomere deformations) in the early embryos at different cleavage stages were observed.
The Baltic Sea is one of the largest brackish seas in the world with a total surface area of 415,240 km2 (including the Danish Straits and Kattegat) with water volume of 21,706 km3. Its environmental conditions depend on the hydrological processes in the catchment area, meteorological forcing, oceanographic processes in the sea, and the interactions between these. The water body of the central Baltic is permanently stratified, with an upper layer of low-salinity (6–8 psu) water and a more saline (10–14 psu) deepwater layer, both separated by a strong halocline. Strong environmental gradients create a variety of habitats with different biota in different subbasins. Due to its young age and reduced salinity the biological structure of the Baltic Sea is relatively restricted. Low species richness is often associated with strong dominance of a few species and high productivity. Being a semienclosed sea surrounded by densely populated and highly industrialized countries, the Baltic Sea is highly vulnerable to anthropogenic pressure. Currently, the major threats to the Baltic Sea are chemical contamination, eutrophication, and hypoxia. Therefore, anthropogenic pressure along with related climate change should be taken into account for assessment of the environmental status of the Baltic Sea and its future changes.
A versatile optode system for oxygen, carbon dioxide, and pH measurements in seawater with integrated battery and logger
Published 9 August 2018 Science ClosedTags: Baltic, chemistry, field, methods, North Atlantic
Herein, we present a small and versatile optode system with integrated battery and logger for monitoring of O2, pH, and pCO2 in seawater. Three sensing materials designed for seawater measurements are optimized with respect to dynamic measurement range and long‐term stability. The spectral properties of the sensing materials were tailored to be compatible with a commercially available laboratory oxygen logger that was fitted into a pressure housing. Interchangeable sensor caps with appropriate “sensing chemistry” are conveniently attached to the end of the optical fiber. This approach allows using the same instrument for multiple analytes, which offers great flexibility and minimizes hardware costs. Applications of the new optode system were demonstrated by recording depth profiles for the three parameters during a research cruise in the Baltic Sea and by measuring surface water transects of pH. The optode was furthermore used to monitor the concentration of dissolved oxygen in a seagrass meadow in the Limfjord, Denmark, and sensor packages consisting of pO2, pH, and pCO2 were deployed in the harbors of Kiel, Germany, and Southampton, England, for 6 d. The measurements revealed that the system can resolve typical patterns in seawater chemistry related to spatial heterogeneities as well as temporal changes caused by biological and tidal activity.
Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)
Published 18 July 2018 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 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.
The effects of low seawater pH on energy storage and heat shock protein 70 expression in a bivalve Limecola balthica
Published 13 July 2018 Science ClosedTags: Baltic, biological response, laboratory, mollusks, physiology
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.
Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming
Published 6 July 2018 Science ClosedTags: Baltic, biological response, BRcommunity, community composition, laboratory, mesocosms, multiple factors, otherprocess, prokaryotes, temperature
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.
