Elevated organic carbon pulses persist in estuarine environment after major storm events

Eero Asmala,Ryan W Paerl,Christopher L Osburn,Hans W Paerl

doi:10.1002/lol2.10169

Abstract

AbstractEstuaries regulate transport of dissolved organic carbon (DOC) from land to ocean. Export of terrestrial DOC from coastal watersheds is exacerbated by increasing major rainfall and storm events and human activities, leading to pulses of DOC that are shunted through rivers downstream to estuaries. Despite an upward trend of extreme events, the fate of the pulsed terrestrial DOC in estuaries remains unclear. We analyzed the effects of seven major tropical cyclones (TC) from 1999 to 2017 on the quantity and fate of DOC in the Neuse River Estuary (NC, USA). Significant TC‐induced increases in DOC were observed throughout the estuary; the increase lasting from around 50 d at head‐of‐tide to over 6 months in lower estuary. Our results suggest that pulsed terrestrial DOC associated with TCs temporarily overwhelms the estuarine filter's abiotic and biotic degradation capacity under such high flow events, enhancing the shunt of terrestrial carbon to the coastal ocean.

Highlights

Estuaries regulate transport of dissolved organic carbon (DOC) from land to ocean
We observed an upward decadal trend in the DOC concentrations in the Neuse River Estuary, which concurs with recent findings of increasing organic matter concentrations throughout the northern hemisphere (Filella and RodríguezMurillo 2014)
Exacerbating the general increase in DOC concentrations, storm events are being recognized as important drivers of organic carbon loading from catchments to drainage networks, but the magnitude of DOC delivery to coastal environments attributable to these events remains uncertain (Avery Jr et al 2004; Clark et al 2007; Brown et al 2014; Paerl et al 2018)

Summary

Introduction

Estuaries regulate transport of dissolved organic carbon (DOC) from land to ocean. Export of terrestrial DOC from coastal watersheds is exacerbated by increasing major rainfall and storm events and human activities, leading to pulses of DOC that are shunted through rivers downstream to estuaries. Despite an upward trend of extreme events, the fate of the pulsed terrestrial DOC in estuaries remains unclear. Our results suggest that pulsed terrestrial DOC associated with TCs temporarily overwhelms the estuarine filter’s abiotic and biotic degradation capacity under such high flow events, enhancing the shunt of terrestrial carbon to the coastal ocean. Estuaries are important ecosystems that mediate processing of terrestrial carbon (C) at the land-ocean interface (Massicotte et al 2017). E.A. designed and performed the data analyses. H.W.P. led the monitoring program that provided the data. All authors contributed to discussions that shaped the manuscript and collaborated on writing the manuscript at all stages

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