鲫(Carassius auratus)对沉水植物占优水体水质的影响

Effects of crucian carp(Carassius auratus)on water quality of aquatic systems dominated by submerged plant

水体富营养化已成为当今世界广泛存在的水环境问题。杂食性鱼类分布广、食性杂,对水生态系统影响深远,可能会加重水体富营养化。以鲫(Carassius auratus)为对象,于室外构建了以沉水植物苦草(Vallisneria denseserrulata)为主要初级生产者的中型水生态系统,设置鲫鱼组与无鱼的对照组,通过测定水中氮、磷营养盐、浮游植物、透明度、溶解氧、pH等指标以研究杂食性鱼类对以苦草为主要初级生产者水体水质的影响。结果表明:鲫虽未显著改变水中的总氮、氨氮含量,但显著增加了总磷含量,提高了浮游植物生物量,降低了水体透明度和溶解氧浓度,从而恶化水质;因此,在以沉水植物为主要初级生产者的水体中,减少或去除鲫等杂食性鱼类,有利于降低水中总磷含量,减少浮游植物生物量,提高水体透明度、从而保护或改善水质。

Eutrophication has been a serious water environmental problem worldwide.Omnivorous fish has been causing profound effects on aquatic ecosystems due to widely distribution and omnivorous diets,enhancing the eutrophication.In this study,mesocosms dominated by submerged plant Vallisneria denseserrulata were constructed without(as controls)and with crucian carp(Carassius auratus)as fish treatment to test whether this species adversely affects the water quality by increasing the nutrient concentrations,stimulating the growth of phytoplankton and increasing water turbidity.Compared with the controls,though the concentrations of total nitrogen and ammonium did not change significantly,total phosphorus(TP)and phytoplankton biomass measured as chlorophyll a increased,while water clarity and dissolved oxygen(DO)decreased in fish treatment mesocosms,thereby deteriorating the water quality.So,reduction or removal of the omnivorous fish,such as crucian carp from a shallow ecosystem dominated by submerged plant,may help protecting or improving the water quality by decreasing TP and phytoplankton biomass,increasing the water clarity and DO.