Posts Tagged 'Baltic'

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

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.

Continue reading ‘Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem’

Ocean acidification may threaten a unique seaweed community and associated industry in the Baltic Sea

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.

Continue reading ‘Ocean acidification may threaten a unique seaweed community and associated industry in the Baltic Sea’

Sensitivities to global change drivers may correlate positively or negatively in a foundational marine macroalga

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.

Continue reading ‘Sensitivities to global change drivers may correlate positively or negatively in a foundational marine macroalga’

Seasonal interactive effects of pCO2 and irradiance on the ecophysiology of brown macroalga Fucus vesiculosus L.

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.

Continue reading ‘Seasonal interactive effects of pCO2 and irradiance on the ecophysiology of brown macroalga Fucus vesiculosus L.’

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

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.

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


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