In the 1980s, the Elbe estuary had largely lost its function as an estuarine filter due to heavy metal pollution. After decades, the estuary was able to recover from this, as a team led by doctoral student Louise Rewrie from the Helmholtz-Zentrum Hereon has discovered by measuring carbon and other parameters. Only in the last few years have biogeochemical processes in the Elbe River Estuary resumed naturally. The results recently appeared in the journal Limnology and Oceanography.
River estuaries can recover from many years of pollution if they are given the time. This is the result of a long-term study in which a team of researchers led by marine science PhD candidate Louise Rewrie from the department Coastal Productivity at Helmholtz-Zentrum Hereon evaluated water samples from the Elbe River over a period of 33 years. The data show that it takes several decades for the habitat and its biological and biogeochemical processes to return to a natural level. Accordingly, environmental protection measures must be planned for the long term.
As the scientists write in the current issue of the journal Limnology and Oceanography, the Elbe was extremely polluted in the mid-1980s. At that time, wastewater from industry and households flowed into the river almost untreated. Particularly large amounts of pollutants entered the Elbe upstream from industrial plants in what was then East Germany and Czechoslovakia – especially toxic heavy metals.
For the study, Rewrie analyzed water samples taken between 1985 and 2018.The water samples originate from regular helicopter flights, which are still carried out today by the Elbe River Basin Community. Water samplers are lowered at certain points along the Elbe estuary. The advantage of aerial surveys is that the entire estuary area from Geesthacht east of Hamburg to the bird island Scharhörn far out in the Elbe estuary can be sampled within a few hours. This provides a snapshot of the pollution situation for the entire estuary, which is about 150 kilometers long, in a short time. Various chemical, physical and biological parameters are then measured, such as the oxygen content or the pH value, the acidity of the water.
The study was led by the Helmholtz-Zentrum Hereon. Also involved were colleagues from the Geomar Helmholtz Centre for Ocean Research Kiel, the Elbe River Basin Community and the German Oceanographic Museum in Stralsund were involved in the study. The results of the aerial surveys were provided by the Elbe River Basin Community in Magdeburg. (Source: Hereon Press Release)
To learn more about the studies and the recovery of the Elbe River, read the Hereon press release and the published study:
==> Always in the flow
Rewrie, L.C.V., Voynova, Y.G., van Beusekom, J.E.E., Sanders, T., Körtzinger, A., Brix, H., Ollesch, G., & Baschek, B. (2023): Significant shifts in inorganic carbon and ecosystem state in a temperate estuary (1985–2018). Limnol Oceanogr., doi:10.1002/lno.12395
Abstract:
Estuaries regulate carbon cycling along the land-ocean continuum and thus influence carbon export to the ocean, and global carbon budgets. The Elbe Estuary in Germany has been altered by large anthropogenic perturbations, such as widespread heavy metal pollution, minimally treated wastewater before the 1980s, establishment of wastewater treatment plants after the 1990s, and an overall nutrient and pollutant load reduction in the last three decades. Based on an extensive evaluation of key ecosystem variables, and an analysis of the available inorganic and organic carbon records, this study has identified three ecosystem states in recent history: the polluted (1985–1990), transitional (1991–1996), and recovery (1997–2018) states. The polluted state was characterized by very high dissolved inorganic carbon (DIC) and ammonium concentrations, toxic heavy metal levels, dissolved oxygen undersaturation, and low pH. During the transitional state, heavy metal pollution decreased by > 50%, and primary production re-established in spring to summer, with weak seasonality in DIC. Since 1997, during the recovery state, DIC seasonality was driven by primary production, and DIC significantly increased by 11 μmol L−1 yr−1, and > 23 μmol L−1 yr−1 in the recent decade (2008–2018), in the mid to lower estuary, indicating that, along with the improvement in water quality the ecosystem state is still changing. Large anthropogenic perturbations can therefore alter estuarine ecosystems (on the order of decades), as well as induce large and complex biogeochemical shifts and significant changes to carbon cycling.