Distribution, fluxes and decadal changes of nutrients in the Jiulong River Estuary, Southwest Taiwan Strait
Tóm tắt
The Jiulong River Estuary (JRE) is a typical subtropical macro-tide estuary on the southwest coast of the Taiwan Strait (TWS), which has been greatly impacted by human activities over the past 30 years. To understand nutrient dynamics and fluxes under such a heavy background of anthropogenic perturbation, eight cruises were conducted from April 2008 to April 2011, covering both wet (May to September) and dry (October to April next year) seasons. Nutrient concentrations were very high for the freshwater end-member in the upper reach of the JRE (nitrate (NO3-N): 120–230 μmol L−1; nitrite (NO2−N): 5–15 μmol L−1; ammonium (NH4−N): 15–170 μmol L−1; soluble reactive phosphorus (SRP): 1.2–3.5 μmol L−1; dissolved silicate (DSi): 200–340 μmol L−1). In dry seasons, concentrations of these nutrients were higher than in wet seasons. Nitrate was the dominant chemical species of dissolved inorganic nitrogen (DIN), with percentages of 67%–96% in wet seasons and 55%–72% in dry seasons. Distributions of NO3-N and DSi against salinity were nearly constant during all cruises, and showed generally conservative mixing behaviors in the estuary (1