1. Benthic primary producers are recognised for their important role in contributing to ecosystem productivity and nutrient cycling in lake and stream ecosystems, particularly in polar environments. In Arctic lakes, benthic producers often comprise mats or colonies of cyanobacteria capable of producing cyanotoxins. However, the extent to which benthic communities contribute cyanotoxins in polar regions remains poorly described.
2. We evaluated the potential for benthic colonies of the cyanobacterium Nostoc pruniforme from lakes in Kangerlussuaq, Greenland, to contribute microcystins (MCs) to lake water using three approaches. First, we dissected field‐collected Nostoc colonies and measured MCs within multiple layers of fresh colony tissue. Second, we conducted a laboratory experiment to evaluate the temporal dynamics of MC release by incubated, intact colonies. Finally, we quantified whether MC concentrations in water and sediment samples in the field were higher in and above dense bands of benthic Nostoc as compared to bare sediment.
3. Field‐collected Nostoc colonies contained MCs throughout the colony tissue, suggesting that damage to colonies from grazers or physical disturbance could facilitate the release of toxins into the water. Undamaged Nostoc colonies incubated in high‐nutrient conditions in the laboratory leaked MCs into the surrounding water at a steady mass‐specific rate over the course of 7 days.
4. Microcystin concentrations in water and sediment from two Greenlandic lakes were highly variable, but slightly higher in lake water immediately above dense bands of Nostoc than in water immediately above bare sediments, suggesting that benthic Nostoc colonies contribute cyanotoxins to lake water and that MCs vary at very fine, 1–2 m spatial scales.
5. Benthic cyanobacteria may be important in releasing MCs into aquatic ecosystems, especially in systems where benthic producers dominate, such as polar environments.

中文翻译：

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Nostoc属的底栖蓝细菌是格陵兰湖泊和池塘中微囊藻毒素的来源。

1. 底栖初级生产者因其在促进湖泊和河流生态系统（尤其是极地环境）中的生态系统生产力和养分循环中的重要作用而获得公认。在北极湖泊中，底栖动物的生产者通常包括能够产生氰毒素的蓝细菌的垫子或菌落。但是，底栖生物群落在极地区域贡献氰毒素的程度仍然缺乏描述。
2. 我们评估了使用三种方法从格陵兰州Kangerlussuaq湖中的蓝藻Nostoc pruniforme底栖菌落为湖水中贡献微囊藻毒素（MCs）的潜力。首先，我们解剖了野外收集的Nostoc菌落，并测量了多层新鲜菌落组织中的MC。其次，我们进行了一项实验室实验，以评估通过孵育的完整菌落释放MC的时间动态。最后，我们量化了田间水和沉积物样品中MC浓度在底栖Nostoc密集带内和上方是否高于裸露沉积物。
3. 野外收集的Nostoc菌落在整个菌落组织中均含有MC，这表明食草动物或物理干扰对菌落造成的损害可促进毒素向水中的释放。在7天的过程中，在实验室中高营养条件下培养的未受损Nostoc菌落以稳定的质量比速率将MC泄漏到周围水中。
4. 来自两个格陵兰湖的水和沉积物中微囊藻毒素的浓度变化很大，但紧接在Nostoc密集带上方的湖水中的微囊藻毒素浓度比裸露的沉积物上方的水中的微囊藻毒素浓度稍高，这表明底栖的Nostoc菌落对湖水贡献了氰毒素，MC的变化非常大。精细的1-2 m空间尺度。
5. 底栖蓝细菌对于将MC释放到水生生态系统中可能很重要，尤其是在底栖生物生产者占主导的系统中，例如极地环境。