Storm induced estuarine turbidity maxima and controls on nutrient fluxes across river-estuary-coast continuum.

Climate change is likely to increase the frequency and intensity of tropical storms. However, the impacts of major storms on nutrient cycling processes in the river-estuary-coast continuum are poorly understood. Continuous observations were made at lower river stations and on a transect down the Jiulong River Estuary in south east China for three storms in 2013-2014. There were major increases in both dissolved nutrients and suspended particulate matter (SPM) brought down the river during storms. Strong Estuarine Turbidity Maxima (ETM) were observed during major storms and were the result of SPM brought down rivers augmented by sediment scoured within the Upper Estuary (salinity=0psu) and possibly also from behind the dikes opened for flood control. There were major increases in dissolved nutrients (nitrate, ammonium and phosphate) in the Upper Estuary particularly during major Storms C (July 2013) and D (May 2014). These increases were probably due to river inflows with surrounding runoff, pore water supply and nutrients desorbed from scoured sediment. During major Storm D there were greater nutrient fluxes through the estuary-coast interface compared to the nutrients supplied through the river-estuary interface while the opposite pattern was observed during normal flow. The increased supply of ammonium and phosphate to the coastal region caused increased chlorophyll a once the light inhibiting SPM had been removed from the water column. This is likely to increase the potential of eutrophication. Storm induced increases in N:P:Si supplied from the estuary to the coastal region increased the degree of P limitation.