Periphytic Actinella Lewis (Ochrophyta, Bacillariophyceae) species from an Environmental Protection Area in the Brazilian Amazon

Abstract Aim The aim of this study is to present the Actinella species found in periphytic samples collected from an Environmental Protection Area in Santarém (PA, Brazil), to comment on their morphology by comparing them with existing records, and to increase knowledge of the distribution of the genus in Pará State. Methods Ten periphytic samples were collected from seven sampling stations in the Alter do Chão Environmental Protection Area (Santarém, Pará, Brazil) in October 2015 and February and July 2016. Dissolved oxygen, pH, conductivity and water temperature were measured in the field at sites from which samples were collected in 2016. Samples were oxidized and analyzed by light microscopy. Results The sampled water bodies presented low conductivity and an acidic pH. We identified 12 Actinella taxa, several of which had originally been described from samples collected from the Amazon in the mid-20th century, mainly in the lower Tapajós River region. Actinella rionegrensis is recorded for the first time in the State of Pará, outside of its type locality (Negro River, near Manaus, AM, Brazil), and the species habitus (wisp-shaped colonies) is recorded for the first time. Conclusion Our results indicate that the Environmental Protection Area has been effective in conserving the aquatic ecosystem, since Actinella species identified in the mid-20 th century are still present. Taxonomic issues for some species of this genus need clarification and revision, since overlapping diagnostic features occur among species and with species belonging to the genus Eunotia.

摘要
研究目的：本研究旨在报道从巴西圣塔伦（帕拉州）某环境保护区采集的周丛生物样本中发现的辐棘藻属（Actinella）物种，通过与已有记录比对对其形态特征进行评述，并增进对该属在帕拉州分布情况的认知。

研究方法：2015年10月、2016年2月与7月，于巴西帕拉州圣塔伦阿尔特杜尚环境保护区的7个采样站点采集了10份周丛生物样本。2016年采样期间，现场测定了各采样点位的溶解氧、pH值、电导率与水温。对样本进行氧化处理后，通过光学显微镜开展分析鉴定。

研究结果：采样水体呈现低电导率与酸性pH特征。本研究共鉴定出12个辐棘藻属分类单元，其中多个类群最初于20世纪中期基于亚马逊流域（主要为塔帕若斯河下游区域）采集的样本被正式描述。本研究首次在帕拉州报道了内格罗辐棘藻（Actinella rionegrensis）的分布记录，其发现地点远离该物种的模式产地（巴西亚马孙州马瑙斯附近的内格罗河），同时首次记录了该物种的束状菌落形态。

研究结论：本研究结果表明该环境保护区在水生生态系统保护方面成效显著，因为20世纪中期已报道的辐棘藻属物种至今仍有留存。由于该属部分物种之间以及与窗纹藻属（Eunotia）物种之间存在诊断特征重叠的情况，因此该属部分物种的分类学问题有待进一步厘清与修订。