Response of epilithic diatom communities to environmental gradients along an Ecuadorian Andean River

Abstract

Epilithic diatom communities are particularly suitable for the evaluation of freshwater quality. In Ecuador, however, no water quality index includes this biotic parameter. This work is the first attempt in the country to determine the composition of epilithic diatom communities associated with different degrees of eutrophication. This was accomplished by measuring physical, chemical and microbiological variables at five sampling sites along the Pita River, Ecuador, from August to December 2016. The results indicate a clear gradient of eutrophication from sampling sites P1 (good water) in the upper reaches to P5 (bad water) located in the lower reaches. Concerning diatom analyses, the results indicated a high diversity for tropical areas in terms of species richness, varying from S=34 in headwaters to S=42 downstream. Moreover, the results obtained suggest a lack of concordance with the trophic values given to some of the epilithic diatoms in the literature. There were also species that seem to be sensitive to downstream nutrient increases that were not considered as bioindicators in previous studies. We concluded that the trophic values of diatom species available in the scientific literature are not directly applicable to their sites in the Pita River. Hence, it is necessary to establish a trophic diatom index for the Andean region of Ecuador.

Bioassessment of water quality of surface waters using diatom metrics

“…Many studies have been carried out to determine the trophic weight and indicator levels of diatom assemblages in different ecoregions (e.g., Rott et al, 1999;Dell'Uomo, 2004;Kelly et al, 2008;Lobo et al 2004Lobo et al , 2015Çelekli et al, 2019b;Salinas-Camarillo et al, 2020). Responses of epilithic diatom assemblages to pollution gradient give crucial information to predict the health of lotic ecosystems (Lobo et al, 2010;Böhm et al, 2013;Heinrich et al, 2015;Castillejo et al, 2018). According to their occurrence/succession in different environmental gradients, diatom taxa are considered as pollution sensitive, intermediate pollution tolerant, and pollution tolerant species based on their trophic weights from various diatom indices (Table 1).…”

Diatomeas como bioindicadores: Aspectos ecológicos de la respuesta de las algas a la eutrofización en América Latina

“…Estos estudios, por lo tanto, se constituyen en el primer paso para el desarrollo de índices regionales eficientes. En Colombia, por ejemplo, Heinrich et al (2018) Castillejo et al (2018) estudiaron la respuesta de las comunidades de diatomeas epilíticas a gradientes ambientales en un río andino, destacando que este trabajo fue el primer intento en el país de determinar la composición de las comunidades de diatomeas epilíticas asociadas con diferentes grados de eutrofización. Esto se logró mediante la medición de variables físicas, químicas y microbiológicas en cinco sitios de muestreo a lo largo del río Pita, Ecuador, de agosto a diciembre de 2016.…”

<p><strong>Three new needle-shaped <em>Fragilaria</em> species from Central America and the Tibetan Plateau</strong></p>

“…However, there is little floristic information on diatoms available for Central America (e.g. Hustedt 1953, Michels-Estrada 2003, Castillejo et al 2018 and the Tibetan Plateau (e.g. Zhu & Chen 1995.…”