Lakes that experience recurrent toxic cyanobacterial harmful algae blooms (cyanoHABS) are often subject to cultural eutrophication, where landscape development and upland activities increase the nutrient inputs to the water column and fuel cyanoHABS. Few studies have focused on the response of a lake to nutrient inputs for which the natural geomorphic setting predisposes a nutrient-rich water column to already support abundant cyanobacteria. Here, we present a sediment core record from a lake surrounded by parkland that experiences recurrent cyanoHABs which produce dangerous levels of the neurotoxin, anatoxin-a, impacting the recreational use of the lake and park. Using photoautotrophic pigments in the sediment record, we establish cyanobacteria have long been part of the diverse and abundant phytoplankton community within the lake. Despite this long record, shotgun metagenome and other DNA analyses of the sediment record suggest that the current anatoxin-a producer Dolichospermum sp. WA102 only emerged to dominate the cyanobacterial community in the mid-1990s. A period of lakeshore farming that finished in the 1950s-1960s and possibly the stocking of rainbow trout fry (1970–2016) coincide with a progressive shift in primary production, together with a change in bacterial communities. Based on the history of the lake and contemporary ecology of Dolichospermum, we propose that the legacy of nutrient inputs and changes in nutrient cycling within the lake has encouraged the development of an ecosystem where the toxin producing Dolichospermum sp WA102 is highly competitive. Understanding the historical presence of cyanobacteria in the lake provides a context for current-day management strategies of cyanoHABs.

经常发生有毒蓝藻有害藻华（cyanoHABS）的湖泊经常遭受文化富营养化，那里的景观发展和高地活动增加了向水柱的营养输入，并为cyanoHABS提供燃料。很少有研究集中在湖泊对养分输入的响应上，因为自然地貌环境使养分丰富的水柱易于支持丰富的蓝细菌。在这里，我们介绍了一个被绿地包围的湖泊的沉积物核心记录，该纪录经历了反复的cyanoHAB，这些氰基HAB产生危险水平的神经毒素anatoxin-a，影响湖泊和公园的娱乐用途。在沉积物记录中使用光合自养色素，我们建立了蓝细菌，长期以来一直是湖中多样化和丰富的浮游植物群落的一部分。Dolichospermum SP。在1990年代中期，WA102才开始在蓝细菌群落中占主导地位。一段1950年代至1960年代结束的湖岸农业以及虹鳟鱼苗（1970-2016年）的放养时期与初级生产的逐步转移以及细菌群落的变化相吻合。基于湖泊的历史和当代Dolichospermum的生态学，我们认为营养物质输入和湖泊内营养物质循环变化的遗产鼓励了生态系统的发展，在该生态系统中，产生毒素的Dolichospermum sp WA102具有很高的竞争力。了解湖泊中蓝细菌的历史存在，为当今氰基HABs管理策略提供了背景。