Institute of Earth Sciences - ICT, University of Évora, Rua Romão Ramalho n°. 59, 7000-671 Évora, Portugal; Renewable Energies Chair, University of Évora, Casa Cordovil, Rua D. Augusto Eduardo Nunes nº7, Évora, 7000-651, Portugal.
Institute of Earth Sciences - ICT, University of Évora, Rua Romão Ramalho n°. 59, 7000-671 Évora, Portugal; Water Laboratory, University of Évora, P.I.T.E. Rua da Barba Rala No. 1, 7005-345 Évora, Portugal.
Sci Total Environ. 2020 Jun 1;719:137462. doi: 10.1016/j.scitotenv.2020.137462. Epub 2020 Feb 20.
The study of intermittent rivers is a critical and timely issue due to their worldwide increase, triggered by several causes including climate change. The need to understand the response of intermittent river biota to water intermittency led us to conduct this study using benthic diatoms collected in southern Portugal. Benthic diatoms were explored in terms of assemblages, diversity indices, the Specific Pollution Sensitivity (SPI) Index, functional metrics (i.e. ecological guilds and life-forms) and conservation status. We verified that changes in water physico-chemical characteristics were highly controlled by flow intermittency, which in turn is directly linked to meteorological variables (air temperature and precipitation). Changes in diatom assemblages reflect the aquatic regime of sites, changes in aquatic states through time and mesohabitats (dry biofilm, samples collected in pools or under flowing conditions). Species richness, on the other hand, did not reflect these differences, whilst Shannon diversity and Pielou's Evenness indices only reflected mesohabitat differences. The SPI distinguished sampling periods, and mesohabitats. The relative abundance of ecological guilds changed with aquatic states, with the low-profile guild dominating in eurheic and arheic conditions (except during Summer), being replaced by motile taxa in summer arheic conditions, reflecting increases in nutrient and siltation. The hypothesis that benthic diatom assemblages in dry biofilm can be used as an indicator of ecological status during the dry-phase was validated, since no differences between the Ecological Quality Ratio determined in dry biofilm collected in Summer 2017 and the previous Spring 2017 in flowing water. A method is proposed for diatom sampling in dry biofilm, contributing to an integrated ecological status evaluation, which considers the dry-phase and enhances the reach of biomonitoring programs.
间歇性河流的研究是一个至关重要且及时的问题，因为它们在全球范围内增加，这是由气候变化等多种原因引发的。了解间歇性河流生物群对间歇性水流的响应促使我们在葡萄牙南部采集底栖硅藻进行这项研究。我们从组合、多样性指数、特定污染敏感性（SPI）指数、功能指标（即生态类群和生活型）和保护状况等方面探讨了底栖硅藻。我们验证了水理化特性的变化主要受水流间歇性的控制，而水流间歇性又直接与气象变量（空气温度和降水）相关。硅藻组合的变化反映了站点的水生状态，随着时间的推移和中间生境（干燥生物膜、在水池中采集的样本或在流动条件下采集的样本）的变化而变化。物种丰富度则没有反映出这些差异，而 Shannon 多样性和 Pielou 的均匀度指数仅反映了中间生境的差异。SPI 区分了采样期和中间生境。生态类群的相对丰度随水生状态而变化，低轮廓类群在 eurheic 和 arheic 条件下占主导地位（夏季除外），在夏季 arheic 条件下被运动类群所取代，反映了营养物质和淤泥的增加。底栖硅藻在干燥生物膜中的组合可以作为干旱期生态状况的指示物的假设得到了验证，因为 2017 年夏季在干燥生物膜中采集的生态质量比与之前 2017 年春季在流动水中采集的生态质量比没有差异。提出了一种在干燥生物膜中进行硅藻采样的方法，有助于综合生态状况评估，该方法考虑了干旱期，并扩大了生物监测计划的范围。
