Eutrophication: Early warning signals, ecosystem-level and societal responses, and ways forward

Bonsdorff, Erik

doi:10.1007/s13280-020-01432-7

Cited by 27 publications

(21 citation statements)

References 32 publications

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“…Integrated approaches encompassing all of the ecosystem-components discussed above, are needed in order to understand and manage the linkages between large-scale and long-term changes driven by synergistic impacts of over-arching climate change-related physical and chemical drivers in combination with other factors such as eutrophication, which may complicate human adaptation to the changing marine ecosystem (Blenckner et al, 2015;Stenseth et al, 2020;Bonsdorff, 2021).…”

Section: Marine Food Websmentioning

confidence: 99%

Climate Change in the Baltic Sea Region: A Summary

Meier

Kniebusch

Dieterich

et al. 2021

Preprint

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Abstract. Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge about the effects of global warming on past and future changes in climate of the Baltic Sea region is summarized and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focusses on the atmosphere, land, cryosphere, ocean, sediments and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in paleo-, historical and future regional climate research, we find that the main conclusions from earlier assessments remain still valid. However, new long-term, homogenous observational records, e.g. for Scandinavian glacier inventories, sea-level driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution and new scenario simulations with improved models, e.g. for glaciers, lake ice and marine food web, have become available. In many cases, uncertainties can now be better estimated than before, because more models can be included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth System have been studied and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication and climate change. New data sets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal time scales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first paleoclimate simulations regionalized for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA) and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics is dominated by tides, the Baltic Sea is characterized by brackish water, a perennial vertical stratification in the southern sub-basins and a seasonal sea ice cover in the northern sub-basins.

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Section: Marine Food Websmentioning

confidence: 99%

Climate Change in the Baltic Sea Region: A Summary

Meier

Kniebusch

Dieterich

et al. 2021

Preprint

Self Cite

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“…Finally, a number of modelling studies are reviewed. The main challenge when analyzing global climate change-induced effects on ecosystems is the possible synergistic effects between climate and other environmental drivers, such as eutrophication, hypoxia, fishing, habitat modifications, and levels of harmful substances, as all of these may be influenced by changes in temperature, salinity and acidification, which then in turn may have profound impacts on parts of or entire ecosystems and their functioning in time and space (Reusch et al, 2018;Stenseth et al, 2020;Bonsdorff, 2021).…”

Section: Introductionmentioning

confidence: 99%

Global climate change and the Baltic Sea ecosystem: direct and indirect effects on species, communities and ecosystem functioning

Viitasalo

Bonsdorff

2021

Preprint

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Abstract. Climate change has multiple direct and indirect potentially synergistic effects on Baltic Sea species, organism communities, and on ecosystem functioning, through physical and biogeochemical environmental characteristics of the sea. Associated indirect and secondary effects on species interactions, trophic dynamics and ecosystem function are expected to be significant. Evidence on effects of climate are compiled from and reviewed for field studies, experimental work, as well as modelling studies primarily from published literature after 2010. The responses vary within and between species groups, even between sibling species. Such subtle differences, as well as secondary feedbacks and altered trophic pathways, make projections difficult. Some common patterns arise from the wealth of recent studies, however. It is likely that the combined effects of increased external nutrient loads, stratification and internal loading will improve the conditions for cyanobacterial blooms in large parts of the Baltic. In the northernmost areas the increasing allochtonous DOM may further complicate the picture by increasing heterotrophy and by decreasing food web efficiency. This effect may, however, be counteracted by the intensification of the bacteria-flagellate-microzooplankton-mesozooplankton link, which may change the system from a bottom-up controlled one to a top-down controlled one. In deep benthic communities, continued eutrophication may promote higher sedimentation of organic matter and increase zoobenthic biomasses, but eventually increasing stratification and hypoxia/anoxia will disrupt benthic-pelagic coupling, leading to reduced benthic biomass. In the photic benthic systems warmer winters with less ice and nutrient increase enhances eutrophication. The projected salinity decline suppresses marine species, and temperature increase overgrowth of perennial macroalgae by annual filamentous alga throughout the growing-season, and major changes in the marine entire ecosystem are expected. The changes in environmental conditions probably also lead to increased establishment of non-indigenous species, potentially affecting food web dynamics in large areas of the Baltic Sea. However, several modelling studies have concluded that nutrient reductions according to the Baltic Sea Action Plan of Helsinki Commission may be a stronger driver for ecosystem functions in the Baltic Sea than climate change. Such studies highlight the importance of studying the Baltic Sea as an interlinked socio-ecological system. Knowledge gaps include uncertainties in projecting the future salinity level as well as stratification under different climate forcings. This weakens our ability to project how overall biodiversity, pelagic productivity, fish populations, and macroalgal communities may change in the future. Experimental work must be better integrated into studies of food web dynamics, to get a more comprehensive view of the responses of the pelagic and benthic systems to climate change, from bacteria to fish. Few studies have holistically investigated the shallow water ecosystems holistically. There are complex climate-induced interactions and multiple feedbacks between algae, grazers and their predators, that are poorly known, as are the effects of non-native invasive species. Finally, both 2D species distribution models and 3D ecosystem models could benefit from better integration of approaches including physical, chemical and biological parameters.

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“…Forest management is known to contribute to nutrient loads in receiving waterbodies [23,28,29] due to decreased water and nutrient uptake and increased runoff [23,30,31], accelerated nitrification and mineralization of organic matter [32,33], and release of nutrients from logging residues [34]. The environmental quality problems in the region, specifically human-induced eutrophication, are highlighted by the poor ecological status of the Baltic Sea [35].…”

Section: Introductionmentioning

confidence: 99%

Carbon, Nutrients and Methylmercury in Water from Small Catchments Affected by Various Forest Management Operations

Kļaviņa

Bārdule

Eklöf

et al. 2021

Forests

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Forest management activities in boreal and hemiboreal environments have been found to increase the concentration of carbon, nutrients, and methylmercury (MeHg) in runoff water, thus contributing to environmental quality issues. We evaluated carbon, nutrient, and MeHg concentrations in water at eight small, forested catchments on organic soils in Latvia, subject to ditch cleaning and beaver dam removal. These management-induced disturbances were classified into a major, minor, or no disturbance classes. The concentrations of dissolved organic carbon and total nitrogen were elevated in disturbed catchments (both major and minor) compared to the catchments with no disturbance. The concentrations of MeHg in the water displayed a clear seasonal variation with higher concentrations in spring and summer, but there were no significant differences in MeHg concentrations between catchments with major, minor, and no disturbances. However, the higher concentrations of SO42− in the disturbed catchments compared to those undisturbed may promote MeHg formation if the conditions become more reduced further downstream. While most former studies of forest management effects on water quality have focused on forest harvest, our research contributes to the currently rather scarce pool of data on the impact of less-studied management operations, such as ditch cleaning and beaver dam removal, on carbon, nutrient, and MeHg concentrations in runoff water.

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Eutrophication: Early warning signals, ecosystem-level and societal responses, and ways forward

Cited by 27 publications

References 32 publications

Climate Change in the Baltic Sea Region: A Summary

Climate Change in the Baltic Sea Region: A Summary

Global climate change and the Baltic Sea ecosystem: direct and indirect effects on species, communities and ecosystem functioning

Carbon, Nutrients and Methylmercury in Water from Small Catchments Affected by Various Forest Management Operations

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