科研之友
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摘要
The objective was to determine the influence of nutrients on primary production on a tropical mudflat at Buloh River estuary, where the culture of blood cockle is the most important in the country and anthropogenic disturbance increasingly threatens it. Water and sediment samples were collected during spring tide at every 150- to 200-m intervals along three transects (north, river mouth, south) set approximately 2 km apart from each other in the wet (November-December 2014) and dry period (February-March 2015). Samples were analysed for their nutrient (N, P, Si) and chlorophyll-a concentrations. Water column chlorophyll concentration on the mudflat to the south of the river mouth was higher compared to the northern site, attributable to the southerly river discharge that contributed to the nutrient (N, P, Si) loadings. During the wet period, the high proportion (up to 92 %) and concentration (77 mu M) of ammonia in the dissolved inorganic nitrogen (DIN) pool appeared to suppress primary production. However, primary production dramatically increased during the subsequent dry period when phosphate-repleted and reduced ammonia conditions prevailed (low N/P ratio). Compared to the previous wet period, chlorophyll concentration in the water column increased 47-fold, while surface sediment chlorophyll increased 67-fold. The dense microalgae with their rapid nutrient uptake resulted in a shift in nutrient status, from relatively high DIN (N/P = 20.7) to potentially nitrogen-limiting (N/P = 4.5) and silica-limiting (Si/N = 0.8) conditions. Given the highly fluctuating primary production on the mudflat, future plans to increase stocking density and allocation of more mudflat area for blood cockle farming will need to consider the carrying capacity of the culture area.
- 出版日期2016-8
