Abstract

The land-ocean dissolved organic carbon (DOC) flux represents a significant term within the global carbon budget, with peatland-dominated regions representing the most intense sources of terrestrial DOC export. As the interface between freshwater and marine systems, estuaries have the potential to act as a filter of the land-ocean carbon flux, removing terrestrially derived DOC, which is present at low concentrations in the oceans, via a combination of physicochemical and biological processes. However, the fate of peat-derived DOC within estuaries remains poorly quantified, partly due to the complicating influences of heterogeneous soils, land-use, point sources, and upstream modification of organic matter. To minimize these modifying factors, we studied DOC and inorganic nutrients in four small, peat-dominated, minimally disturbed, and oligotrophic Falkland Island estuaries. Contrary to expectations, we found limited evidence of physicochemical estuarine DOC removal, and instead observed apparent "hot zones" of biogeochemical activity, where terrestrially-derived silicate mixed with inorganic nitrogen and phosphorus entering the estuaries from the nutrient-rich marine ecosystem. In two estuaries, this coincided with apparent in situ DOC production. We suggest that the observed phenomena of marine nutrient subsidy of estuarine productivity, and flexible utilization of multiple nutrients within the oligotrophic system, may once have been widespread in temperate estuaries. However, this function has been lost in many ecosystems due to catchment eutrophication by agricultural and urban development. We conclude that the estuaries of the Falkland Islands provide a valuable pre-disturbance analogue for natural biogeochemical functioning in temperate estuaries receiving high organic matter inputs.

Published in

Limnology and Oceanography
2023, Volume: 68, number: 8, pages: 1802-1820
Publisher: WILEY

SLU Authors

• Evans, Christopher

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    
  • Centre for Ecology and Hydrology (CEH)

Sustainable Development Goals

Conserve and sustainably use the oceans, seas and marine resources for sustainable development


UKÄ Subject classification

Oceanography, Hydrology, Water Resources
Ecology
Geochemistry


Publication identifier

DOI: https://doi.org/10.1002/lno.12387

Permanent link to this page (URI)

https://res.slu.se/id/publ/122789