Details

Autor(en) / Beteiligte

• Felgate, Stacey L.
• Barry, Christopher D. G.
• 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, Bethany K.
• Lapworth, Dan J.
• Pinder, Adam
• Price, David M.
• Rosado, Samir
• Evans, Claire

Titel

Conversion of Forest to Agriculture Increases Colored Dissolved Organic Matter in a Subtropical Catchment and Adjacent Coastal Environment

Ist Teil von

• Journal of geophysical research. Biogeosciences, 2021-06, Vol.126 (6), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2021

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• 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. Plain Language Summary The transport of land‐derived dissolved organic matter into the oceans plays a substantial and important role in the global carbon and nutrient cycles. Land‐use change can alter the type and amount of material being transported, with widespread implications for downstream ecosystems. This is particularly true in the tropics and subtropics where land‐use change is occurring most rapidly, and where research into its effects is often lacking. We investigated whether land‐use had an effect on the type and amount of land‐derived material found in a subtropical river system that is experiencing a rapid conversion from forest to agricultural and urban land‐use. We found that streams draining agricultural and urban land contained more land‐derived material than those draining forested land, and that a substantial fraction of this material reached the coastal environment. We estimated the frequency with which this land‐derived material reached the region's environmentally and economically valuable coral reefs, and suggest that land‐use‐derived material reaches nearshore corals often and offshore corals rarely. Key Points A shift from broadleaf forest to agri‐urban land increased colored dissolved organic matter in the Belize River watershed Humic‐like material increased in transit downstream and behaved conservatively in coastal waters, indicative of its recalcitrance Land‐use change has increased terrigenous dissolved organic matter concentrations overlying Belize's coral reefs