Sediment Phosphate Release Flux Under Hydraulic Disturbances in the Shallow Lake of Chaohu, China

Quantifying the effect of hydraulic disturbances on sediment phosphate release is a key issue in the water quality assessment of lakes, especially for the shallow lakes which are susceptible to winds and waves. Here, we sampled the original sediment columns from 12 positions in the eastern, central, and western areas of the Chaohu Lake, a representative shallow lake in China, and observed phosphate release under three levels of hydraulic disturbances in the laboratory. When the disturbance was weak and the surface sediment of bottom mud moved individually (the Individual Motion Mode), sediment phosphate release rate was insignificant (0.24 mg/m2/d). When the disturbance was medium and only a small percentage (<16%) of surface sediment started to move (the Small Motion Mode), phosphate release rate sharply increased to 4.81 mg/m2/d. When the disturbance was further strengthened and most (≥16%) of the surface sediment moved (the General Motion Mode), phosphate release rate was more than doubled (10.23 mg/m2/d). With the increase of hydraulic disturbance intensity, the variation range of phosphate release also became wider. Spatial distribution showed that the release rate varies the most in the western area, followed by the eastern and the central areas. By extrapolating the experimental results to the real scale, we found the phosphate release fluxes would probably fall within a wide range between 203.43 kg/d to 7311.01kg/d under different levels of hydrodynamic disturbances with considerably affects phosphate release from shallow lakes. This study also has implications for the pollutant management in other shallow lakes.

KANDUNGAN FOSFAT DAN NITRAT KAITANNYA DENGAN KEBERADAAN GASTROPODA PADA EKOSISTEM MANGROVE DI PERAIRAN KAMBAPI, KABUPATEN MERAUKE

Mangrove ecosystem is inhabited by a variety of biota, one of the fauna inhabitants of the original mangrove area isgastropods. It is the quality of the waters which certainly has a direct impact on aquatic biota. Nitrate and phosphateare needed by gastropods because they are related to nutrient availability. The purpose of this study is to determinethe phosphate and nitrate contents and analyze the relationship between phosphate and nitrate contents and thepresence of gastropods in the mangrove ecosystem at the Kambapi Beach, Merauke. Data analysis used ecologicaldata of abundance, diversity, dominance and PCA. The results showed that phosphate contents ranged from 0.002-0.04 mg / l and nitrate ranged from 0.007 to 0.19 mg / l, whereas in sediment phosphate contents ranged from 9.63-19.32 mg / l and nitrates ranged from 0.89-4.55mg / l. The results of the analysis of the relationship between thepresence of gastropods and phosphate and nitrate indicates that the parameters of phosphate and nitrate in sedimentsand phosphates in waters have a positive value which means that these parameters affect the presence of gastropoddensity while the environment parameters which correlate negatively is nitrate in the water. This shows that thenitrate contents in water have an inverse relationship with gastropod density.Keywords: Gastropod, Merauke, Phosphate, Nitrate