Land use change increases contaminant sequestration in blue carbon sediments

Stephen R Conrad; Isaac R Santos; Shane A White; Ceylena J Holloway; Dylan R Brown; Praktan D Wadnerkar; Rogger E Correa; Rebecca L Woodrow; Christian J Sanders

doi:10.1016/j.scitotenv.2023.162175

Land use change increases contaminant sequestration in blue carbon sediments

Sci Total Environ. 2023 May 15:873:162175. doi: 10.1016/j.scitotenv.2023.162175. Epub 2023 Feb 17.

Authors

Stephen R Conrad¹, Isaac R Santos², Shane A White¹, Ceylena J Holloway¹, Dylan R Brown¹, Praktan D Wadnerkar¹, Rogger E Correa³, Rebecca L Woodrow¹, Christian J Sanders⁴

Affiliations

¹ National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW 2540, Australia.
² National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW 2540, Australia; Department of Marine Sciences, University of Gothenburg, P.O. Box 461, 40530 Gothenburg, Sweden.
³ National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW 2540, Australia; Corporacion Merceditas - Merceditas Corporation, Medellín, Colombia.
⁴ National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Coffs Harbour, NSW 2540, Australia. Electronic address: christian.sanders@scu.edu.au.

PMID: 36801407
DOI: 10.1016/j.scitotenv.2023.162175

Abstract

Coastal blue carbon habitats perform many important environmental functions, including long-term carbon and anthropogenic contaminant storage. Here, we analysed twenty-five ²¹⁰Pb-dated mangrove, saltmarsh, and seagrass sediment cores from six estuaries across a land-use gradient to determine metal, metalloid, and phosphorous sedimentary fluxes. Cadmium, arsenic, iron, and manganese had linear to exponential positive correlations between concentrations, sediment flux, geoaccumulation index, and catchment development. Increases in anthropogenic development (agricultural or urban land uses) from >30 % of the total catchment area enhanced mean concentrations of arsenic, copper, iron, manganese, and zinc between 1.5 and 4.3-fold. A ~ 30 % anthropogenic land-use was the threshold in which blue carbon sediment quality begins to be detrimentally impacted on an entire estuary scale. Fluxes of phosphorous, cadmium, lead, and aluminium responded similarly, increasing 1.2 to 2.5-fold when anthropogenic land-use increased by at least 5 %. Exponential increases in phosphorus flux to estuary sediments seem to precede eutrophication as observed in more developed estuaries. Overall, multiple lines of evidence revealed how catchment development drives blue carbon sediment quality across a regional scale.

Keywords: Mangrove; Metalloid; Phosphorus; Saltmarsh; Seagrass; Trace metal.