Conversion of forest to agriculture increases colored dissolved organic matter in a subtropical catchment and adjacent coastal environment
Felgate, Stacey L.; Barry, Christopher D.; Mayor, Daniel J.; Sanders, Richard; Carrias, Abel; Young, Arlene; Fitch, Alice; Mayorga-Adame, Claudia G; Andrews, Gilbert; Brittain, Hannah; Cryer, Sarah E.; Evans, Chris D.; Goddard-Dwyer, Millie; Holt, Jason T.; Hughes, Bettany K.; Lapworth, Dan J.; Pinder, Adam; Price, David M.; Rosado, Samir; Evans, Claire
Peer reviewed, Journal article
Published version
Date
2021Metadata
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Original version
10.1029/2021JG006295Abstract
Land-ocean dissolved organic matter (DOM) transport is a significant and changing term in global biogeochemical cycles which is increasing as a result of human perturbation, including land-use change. Knowledge of the behavior and fate of transported DOM is lacking, particularly in the tropics and subtropics where land-use change is occurring rapidly. We used Parallel Factor (PARAFAC) Analysis to investigate how land-use influenced the composition of the DOM pool along a subtropical land-use gradient (from near-pristine broadleaf forest to agri-urban settings) in Belize, Central America. Three humic-like and two protein-like components were identified, each of which was present across land uses and environments. Land-use mapping identified a strong (R2 = 0.81) negative correlation between broadleaf forest and agri-urban land. All PARAFAC components were positively associated with agri-urban land-use classes (cropland, grassland, and/or urban land), indicating that land-use change from forested to agri-urban exerts influence on the composition of the DOM pool. Humic-like DOM exhibited linear accumulation with distance downstream and behaved conservatively in the coastal zone whilst protein-like DOM exhibited nonlinear accumulation within the main river and nonconservative mixing in coastal waters, indicative of differences in reactivity. We used a hydrodynamic model to explore the potential of conservative humics to reach the region's environmentally and economically valuable coral reefs. We find that offshore corals experience short exposures (10 ± 11 days yr−1) to large (∼120%) terrigenous DOM increases, whilst nearshore corals experience prolonged exposure (113 ± 24 days yr−1) to relatively small (∼30%) terrigenous DOM increases.