Toxic benthic cyanobacterial proliferations, particularly of the genus Phormidium, are a major concern in many countries due to their increasing extent and severity. The aim of this study was to improve the current understanding of the dominant physicochemical variables associated with high Phormidium cover and toxin concentrations. Phormidium cover and anatoxin concentrations were assessed weekly for 30 weeks in eight predominately cobble-bed rivers in the South Island of New Zealand. Phormidium cover was highly variable both spatially (among and within sites) and temporally. Generalized additive mixed models (GAMMs) identified site, month of the year, conductivity and nutrient concentrations over the accrual period as significant variables associated with Phormidium cover. Cover was greatest under low to intermediate accrual dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) concentrations. Accrual nutrients had a strong, negative effect on cover at concentrations > 0.2 mg L^− 1 DIN and 0.014 mg L^− 1 DRP. The effect of flow was generally consistent across rivers, with cover accruing with time since the last flushing flow. Total anatoxins were detected at all eight study sites, at concentrations ranging from 0.008 to 662.5 mg kg^− 1 dried weight. GAMMs predicted higher total anatoxin concentrations between November and February and during periods of accrual DRP < 0.02 mg L^− 1. This study suggests that multiple physicochemical variables may influence Phormidium proliferations and also evidenced large site-to-site variability. This result highlights a challenge from a management perspective, as it suggests that mitigation options are likely to be site-specific.

中文翻译：

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的时空动态纤细席八条新西兰河流盖和类毒素浓度的对比营养和流态

有毒的底栖蓝细菌繁殖，特别是Ph属的繁殖，由于其程度和严重性的增加而引起了人们的极大关注。这项研究的目的是提高当前对与高磷覆盖率和毒素浓度相关的主要理化变量的了解。纤细席盖和类毒素浓度每周评估30在新西兰南岛8主要的鹅卵石床河流周。or 覆盖率在空间（站点内和站点内）和时间上都高度可变。广义添加剂混合模型（GAMMs）标识的网站，这一年，电导率和营养浓度在发生当期与相关显著变量月纤细席盖。在低至中间的应计溶解无机氮（DIN）和溶解反应性磷（DRP）浓度下，覆盖率最大。当浓度> 0.2 mg L ^{− 1} DIN和0.014 mg L ^{− 1时}，应计养分对覆盖率产生强烈的负面影响        DRP。跨河流的水流影响总体上是一致的，自上次冲洗水流以来，覆盖物随时间而累积。在所有八个研究地点均检测到总抗毒素，浓度范围为0.008至662.5  mg  kg ^{- 1}干重。GAMMs预测11月至2月之间以及应计DRP < 0.02 mg L ^{- 1}期间总的总抗毒素浓度较高。这项研究表明，多种物理化学变量可能会影响Ph的增殖，并且还证明了较大的位点间变异性。从管理的角度来看，此结果凸显了一项挑战，因为它表明缓解措施可能是针对特定地点的。