Browning of freshwaters: Consequences to ecosystem services, underlying drivers, and potential mitigation measures

Abstract

Browning of surface waters, as a result of increasing dissolved organic carbon and iron concentrations, is a widespread phenomenon with implications to the structure and function of aquatic ecosystems. In this article, we provide an overview of the consequences of browning in relation to ecosystem services, outline what the underlying drivers and mechanisms of browning are, and specifically focus on exploring potential mitigation measures to locally counteract browning. These topical concepts are discussed with a focus on Scandinavia, but are of relevance also to other regions. Browning is of environmental concern as it leads to, e.g., increasing costs and risks for drinking water production, and reduced fish production in lakes by limiting light penetration. While climate change, recovery from acidification, and land-use change are all likely factors contributing to the observed browning, managing the land use in the hydrologically connected parts of the landscape may be the most feasible way to counteract browning of natural waters.

Operationalizing ecosystem service bundles for strategic sustainability planning: A participatory approach

“…The population has grown with 16 percent (SCB 2018 ) and the area has become dominated by larger scale and more homogenous farming and forestry enterprises. Brownification, a process of increasing levels of dissolved organic carbon in the river water due to a combination of changes in rain water acidity, forestry practices and climate change (Kritzberg et al 2020 ), has emerged as an important issue, encompassing both upstream–downstream and exploitation–recreation conflicts (Tuvendal and Elmqvist 2011 ).…”

“…Research funded through this call was intended to focus on practical applications of the concept. Second, Kristianstad Biosphere Office was experiencing challenges with brownification and believed that an ecosystem service approach could support a coordination effort to address this complex challenge, which is caused by a combination of processes (Kritzberg et al 2020 ), many of which are happening upstream, outside of the reserve boundaries. This motivated Kristianstad Biosphere Office to contact members of the author team to jointly apply for the SEPA funding.…”

Centers of endemism of freshwater protists deviate from pattern of taxon richness on a continental scale

“…Taxon richness of Chrysophyceae was exceptionally high in Scandinavia, which corresponds to a pre-dominance of Chrysophyceae in many Scandinavian lakes 64 . Since many Scandinavian lakes are nutrient poor, slightly acidic and rich in humic substances the high taxon richness may reflect abiotic conditions favoring this taxonomic group 65 – 67 .…”

Available Dissolved Organic Carbon Alters Uptake and Recycling of Phosphorus and Nitrogen from River Sediments

“…Concurrent with diffuse N and P pollution, agriculture has significantly impacted the quantity, composition, and bioavailability of catchment-derived dissolved organic carbon (DOC) in stream ecosystems [7][8][9]. There is also a widely understood change in aquatic DOC concentration and forms associated with DOC release from sources of humified soil C [10], effluents and urban areas [11,12]. This change in DOC sources could be of significant importance for the N and P losses as, based on the stoichiometric theory, the availability of DOC to microbiota is the primary driver controlling assimilative and dissimilative nutrient uptake [13][14][15][16].…”