Wetlands as a potential multi-functioning tool to mitigate eutrophication and brownification

Eutrophication and brownification are ongoing environmental problems
affecting aquatic ecosystems. Due to anthropogenic changes, increasing
amounts of organic and inorganic compounds are entering aquatic systems
from surrounding catchment areas, increasing both nutrients, total organic
carbon (TOC), and water color with societal, as well as ecological
consequences. Several studies have focused on the ability of wetlands to
reduce nutrients, whereas data on their potential to reduce TOC and water
color is scarce. Here we evaluate wetlands as a potential multi-functional
tool for mitigating both eutrophication and brownification. Therefore, we
performed a study over 18 months in nine wetlands allowing us to estimate
the reduction in concentrations of total nitrogen (TN), total phosphorus
(TP), TOC, and water color. We show that wetland reduction efficiency with
respect to these variables was generally higher during summer, but many of
the wetlands were also efficient during winter. We also show that some,
but not all, wetlands have the potential to reduce TOC, water color, and
nutrients simultaneously. However, the generalist wetlands that reduced
all four parameters were less efficient in reducing each of them than the
specialist wetlands that only reduced one or two parameters. In a broader
context, generalist wetlands have the potential to function as
multi-functional tools to mitigate both eutrophication and brownification
of aquatic systems. However, further research is needed to assess the
design of the generalist wetlands and to investigate the potential of
using several specialist wetlands in the same catchment.