以水绵和刚毛藻为代表的丝状藻广泛存在于各种自然水体和养殖水体，其过度生长对水体环境和养殖动物构成威胁。为探究丝状藻发生的关键因子，实验通过走访调查，筛选了5组环境相同且隶属同一家养殖户的有丝状藻池塘和无丝状藻池塘，重点对水质、底泥生物可利用性氮磷含量及丝状藻繁殖体进行了检测分析。结果显示，5组有丝状藻塘、无丝状藻塘整体水体氮磷水平无显著差异，而有4组无丝状藻塘叶绿素a含量显著高于有丝状藻塘。5组有丝状藻塘底泥平均生物可利用性氮含量为(15.72±3.60) mg/kg，而无丝状藻塘底泥平均生物可利用性氮为(13.22±1.97) mg/kg，较前者低2.50 mg/kg。5组有丝状藻塘底泥平均生物可利用性磷含量为(72.26±10.57) mg/kg，无丝状藻塘底泥平均生物可利用性磷含量为(50.33±12.62) mg/kg，较前者低21.93 mg/kg。底泥生物可利用性氮磷比在5组中均小于0.5，而无丝状藻塘平均较有丝状藻塘高26.32%。低氮磷比会抑制浮游藻类的繁殖，而丝状藻则对低氮及低氮磷比环境具有较强的适应能力。因此，在养殖开始时，底泥低氮及低氮磷比的条件使得浮游藻类在与丝状藻的初期生态位竞争中处于劣势，即使检测到的浮游藻类OTUs数量高于丝状藻繁殖体，也不能使其在上述条件下成为优势种。另外，对丝状藻繁殖体的检测发现，其广泛存在于有丝状藻塘、无丝状藻塘及水源的水体和底泥中，即使清塘、晒塘依然检测到繁殖体的存在，但清塘、晒塘能够减少丝状藻繁殖体的数量。研究表明，单独依靠生石灰或漂白粉清塘并不能完全杜绝丝状藻的发生，但可以作为一个辅助防控措施，而通过调控养殖系统的生物可利用氮含量及氮磷比左右种间生态位竞争则是一个值得深入研究的、有前景的丝状藻防控方向。本实验结果对养殖池塘的丝状藻防控研究和生产实践具有重要的参考价值。

Filamentous algae, represented by Spirogyra and Cladophora, exist widely in various natural and aquatic waters, and their overgrowth poses a threat to aquatic environment and cultured animals. In order to explore the key factors for filamentous algae occurrence, five pairs of ponds with and without filamentous algae in the same environment and belonging to the same farmers were selected for this study. Their water quality, bioavailable nitrogen and phosphorus in sediment, as well as filamentous algae propagules were detected and analyzed. The results showed that there were no significant differences in total nitrogen and phosphorus levels between ponds with and without filamentous algae (P>0.05), whereas the content of Chlorophyll a in four ponds in with filamentous algae was significantly higher than that in corresponding ponds without filamentous (P<0.05). The average bioavailable nitrogen content in the sediment of ponds with filamentous algae was (15.72±3.60) mg/kg, whereas the average bioavailable nitrogen content in those without filamentous algae was (13.22±1.97) mg/kg, 2.50 mg/kg lower than that of the former. The average available phosphorus content in the sediment of ponds with filamentous algae was (72.26±10.57) mg/kg, and that of ponds without filamentous algae was (50.33±12.62) mg/kg, 21.93 mg/kg lower than that of the former. The ratio of available N/P in sediment was below 0.5 in the five pairs, and the ratio of available N/P in ponds without filamentous algae was 26.32% higher than that in ponds with filamentous algae. Phytoplankton growth could be inhibited in low N/P ratio condition, whereas filamentous algae has strong adaptability to low nitrogen content and N/P ratio environment. Therefore, at the beginning of culturing, the conditions of low nitrogen content and low N/P ratio in the sediment put the phytoplankton at a disadvantage in the initial niche competition with filamentous algae, and even if the OTUs number of phytoplankton detected was larger than that of filamentous algae propagules, it did not make it the dominant species under the above conditions. In addition, the detection of filamentous algae propagules showed that they were widely present in water bodies and sediment of ponds with and without filamentous algae , as well as in water sources, and filamentous algae propagules were detected even in sterilized and sun-exposed ponds. However, the number of filamentous algae propagants could be reduced by sterilizing and sun-exposing ponds. Therefore, quicklime or bleaching powder alone cannot completely eliminate the occurrence of filamentous algae, but can be used as an auxiliary control measure, whereas controling the interspecific niche competition with the regulation of bioavailable nitrogen content and the ratio of nitrogen and phosphorus is a promising direction of controlling filamentous algae worth further study. The results of this experimental study have important reference value for the research and production practice of filamentous algae prevention and control in aquaculture ponds.

S 917.3

国家现代农业产业技术体系专项；黄河三角洲人才工程(DYRC20190210)