伊乐藻管理对河蟹精养池藻类水华的防控作用

Algal Bloom Prevention and Control in Intensive Culture Ponds of Eriocheir sinensis by Management of Elodea nuttallii Planting

为探究河蟹(Eriocheir sinensis)精养池塘中伊乐藻(Elodea nuttalli)管理对藻类水华的预防和控制作用,2017年6月10日至10月25日在上海泖港地区河蟹精养池塘进行试验。实验设置处理组(控制植株高度30cm)和对照组(控制植株在水面以下20cm)。对池塘水质进行监测,利用回归分析判别水质理化因子与Chl-a浓度之间的关系。结果显示,对照组水体Chl-a的平均浓度是处理组的4.66倍(P<0.01),且TP、PO4-P、T、pH、DO和SD都显著高于处理组(P<0.05),两组的Chl-a浓度与TP、PO4-P、T、pH、DO呈显著的正相关,与SD呈显著的负相关(P<0.01),处理组Chl-a浓度还与NO3-N具有显著的正相关性(P<0.05),与CODMn、NH4-N、NO2-N、TN、TN/TP不相关,说明营养物质特别是TP和PO4-P的增多一定程度上会促进藻类的生长,河蟹精养池对伊乐藻的管理比常规处理能够更有效地抑制藻类生长,从而达到生态养殖的目的。

Algae blooms are one of the key issues inhibiting development of Eriocheir sinensis aquaculture.Cultivation of submerged plants,especially Eriocheir nuttallii,in E.sinensis culture ponds provides a new approach for controlling algal blooms in crab ponds.However,traditional planting of E.nuttallii limits inhibition of algae blooms.To better prevent and control algae blooms in crab culture ponds,we explored a new management approach and provide data and new ideas for improving cultivation of E.nuttallii.The experiment was carried out in crab breeding ponds from June 10to October 25,2017in the Shanghai Songjiang district.Two E.nuttallii planting trials were set in triplicate.In the treatment group,plant height was limited to 30cm and in the control group,plants were 20cm below the water surface.The six experimental ponds were semi-closed with an area of 0.5hm2.In February,E.nuttallii was planted to cover of 60%of the pond surface and reached 95%before the trial began.E.sinensis were released into the pond in March at a density of 9000ind/hm2.During the experiment,E.sinensis were fed once a day,as usual,and harvesting of E.nuttallii was based on plant growth.Water quality in each pond was monitored twice in June and October,and at irregular intervals in July,August and September,according to phytoplankton level and water color.After the trials were completed,the relationship between Chl-a concentration and the physicochemical water quality parameters was analyzed by regression analysis.The average concentration of Chl-a in the control group was 4.66times higher(P<0.01)than that of the treatment group.TP,PO4-P,T,pH,DO,and SD in the control group were significantly higher than those in the treatment group(P<0.05).The concentration of Chl-a in the control and treatment groups both presented a significantly positive correlation with TP,PO4-P,T,pH,DO,and a significantly negative correlation with SD(P<0.01).There was also a significant positive correlation of Chl-a with NO3-N in the treatment group(P<0.05).Chl-a was not correlated with CODMn,NH4-N,NO2-N,TN,TN/TP in either group(P>0.05).These findings indicate that increased nutrient concentrations,especially TP and PO4-P,will promote algal growth.The management of E.nuttallii planting in the treatment group demonstrated more effective prevention and control of phytoplankton growth in intensive culture ponds of E.sinensis and ecological cultivation was achieved.