Posts Tagged 'Baltic'

Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2

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.

Continue reading ‘Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2’

Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales

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.

Continue reading ‘Effects of environmental stressors on a habitat forming macroalga over evolutionary and ecological time scales’

Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification

• 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.

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.

Continue reading ‘Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification’

A new mesocosm system to study the effects of environmental variability on marine species and communities

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.

Continue reading ‘A new mesocosm system to study the effects of environmental variability on marine species and communities’

Sedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea

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.

Continue reading ‘Sedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea’

Ocean acidification research in Estonia: challenges and opportunities

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

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.

Continue reading ‘Ocean acidification in the Baltic Sea: involved processes, metrology of pH in brackish waters, and calcification under fluctuating conditions’

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Ocean acidification in the IPCC AR5 WG II

OUP book