Nutrient dynamics and short-time scale variability of environmental parameters during the tidal cycle in the coastal waters of Incheon, Korea

Diurnal variability of nutrients, DOC, turbidity and other environmental parameters was investigated during the spring tidal cycle at the lower part of Han River Estuary, Korea. At every second or minute interval, automated monitoring system with online nutrient autoanalyzer, multi-parameter environmental monitoring sensors, DGPS, echo sounder and ADCP was used to evaluate the short-time scale variability and geochemical behavior of nutrients during the tidal cycle. During the flood tide, nitrate ranged from 21 to 152 μM and showed a convex nonconservative property along the salinity gradient. Meanwhile, ammonia ranged from 21 to 77 μM but showed a concave nonconservative property along the salinity gradient. This implies that sources of nitrate and nitrite are balanced against ammonia removal by nitrification process during a tidal excursion. Interestingly, marked increase of phosphate coincided with the maximum turbidity that occurred during the initial part of flood tide. Dissolved oxygen budget will be discussed with nitrification process and DOC oxidation in this macrotidal estuarine mixing area.