Responses of aquatic macrophytes to anthropogenic pressures: comparison between macrophyte metrics and indices

Abstract

Macrophyte responses to anthropogenic pressures in two rivers of Central Spain were assessed to check if simple metrics can exhibit a greater discriminatory and explanatory power than complex indices at small spatial scales. Field surveys were undertaken during the summer of 2014 (Duraton River) and the spring of 2015 (Tajuña River). Aquatic macrophytes were sampled using a sampling square (45 × 45 cm). In the middle Duraton River, macrophytes responded positively to the presence of a hydropower dam and a small weir, with Myriophyllum spicatum and Potamogeton pectinatus being relatively favored. Index of Macrophytes (IM) was better than Macroscopic Aquatic Vegetation Index (MAVI) and Fluvial Macrophyte Index (FMI) in detecting these responses, showing positive and significant correlations with total coverage, species richness, and species diversity. In the upper Tajuña River, macrophytes responded both negatively and positively to the occurrence of a trout farm effluent and a small weir, with Leptodictyum riparium and Veronica anagallis-aquatica being relatively favored. Although IM, MAVI, and FMI detected both negative and positive responses, correlations of IM with total coverage, species richness, and species diversity were higher. Species evenness was not sensitive enough to detect either positive or negative responses of aquatic macrophytes along the study areas. Overall, traditional and simple metrics (species composition, total coverage, species richness, species diversity) exhibited a greater discriminatory and explanatory power than more recent and complex indices (IM, MAVI, FMI) when assessing responses of aquatic macrophytes to anthropogenic pressures at impacted specific sites.

Application of Macrophytes to the Assessment and Classification of Ecological Status above and below the Barrage with Hydroelectric Buildings

“…They are resistant to different habitat conditions and cannot be seen as valuable, reference taxa for a given watercourse section because they can occur in various environmental conditions and have no distinct value as pollution indicators (they occur both in highly polluted and clean environments). Consequently, a slightly negative, although not very significant influence of hydroelectric buildings on the living conditions of macrophytes can be seen from this research [27][28][29].…”

Environmental DNA gives comparable results to morphology-based indices of macroinvertebrates in a large-scale ecological assessment

“…Thereby, DNA extracted from an environmental sample (so-called environmental DNA, eDNA) provides information about the possible occurrence and distribution of species [ 10 – 13 ]. Monitoring based on eDNA sampling has been explored for different indicator taxa, including fish (e.g., [ 14 , 15 ]); macroinvertebrates (e.g., [ 16 – 18 ]); macrophytes (e.g., [ 19 , 20 ]) and diatoms (e.g., [ 21 , 22 ]). In several instances, eDNA sampling was shown to complement traditional approaches for the assessment of biological indicators and the ecological state of ecosystems [ 23 – 25 ].…”

Impact and recovery of water quality in a river with salmon aquaculture

“…The results reported in the present study are in line with the results of these studies—that is, that scores increased the further from the hatchery the samples were taken and that there was increased abundance and diversity at downstream sites in pollution tolerant species. The use of macrophytes as a water quality indicator is sometimes queried as it may lack the finer detail or resolution of macroinvertebrates indices (Benítez‐Mora & Camargo, 2014; Camargo, 2018; Demars et al., 2012). However, the importance of macrophytes in promoting channel diversity, engineering ecological recovery from drainage works or flood events and their underlying support for physical water quality (O'Briain et al., 2017) cannot be overstated.…”