Longitudinal distribution and seasonality of macroalgae in a subtropical stream impacted by organic pollution

Abstract

Aim: This study was carried out to assess longitudinal and temporal distribution and the effects of organic pollution on macroalgal communities in a subtropical stream; Methods: The occurrence and percent cover of stream macroalgae were investigated during seasonal period in four sampling sites along the course of the Cascavel Stream, in Paraná State, subtropical area of Brazil. Sampling sites were randomly chosen; however, their location in relation to urban organic pollution sources was taken into consideration. Besides, several stream variables usually related to organic pollution in aquatic ecosystems were measured; Results: Eleven macroalgal taxa were found during the samplings. Chlorophyta was the prevailing division (4 species or 36.3% of the total richness), followed by Cyanophyta and Rhodophyta (3 or 27.3%) and Heterokontophyta (1 or 9.1%). Analysis of variance (ANOVA) showed no significant differences in species diversity, percent cover and diversity index among seasons or the sampling sites. In addition, species diversity was not correlated with any environmental variable in particular. On the other hand, the relative composition of the stream macroalgal communities showed wide spatial and temporal variation. Thus, Chlorophyta had higher values of richness and percent cover in sampling site with higher levels of organic pollution, while Rhodophyta was never found in this segment. Taking seasonality into consideration, Chlorophyta had higher values of percent cover in winter, but Rhodophyta and Cyanophyta in spring and fall, respectively; Conclusions: In general terms, in this study macroalgal community structures were slightly affected by organic pollution, mainly by increase in richness and percent cover of Chlorophyta associated with the absence of Rhodophyta in the most polluted sampling site. The analysis of the richness throughout the stretch of the stream showed that the highest values were found in the intermediate part, being partly in accordance with the RCC (River Continuum Concept).

Modeling the species richness and abundance of lotic macroalgae based on habitat characteristics by artificial neural networks: a potentially useful tool for stream biomonitoring programs

“…In this context, ANNs have been treated as a powerful computational tool, since they can deal with nonlinear relationships, which are typical for most ecological relationships (Gevrey et al 2003;Gebler et al 2014). Artificial neural networks have been used in studies on organisms from freshwater ecosystems (e.g., Park et al 2003;Penczak et al 2012;Gebler et al 2014;Lopez-Exposito et al 2016); however, no further study has yet been conducted to confirm the performance of this approach in predicting the structure (richness and abundance) of lotic macroalgae communities, which are among the most important primary producers and are promising bioindicators of the trophic state in continental running water (Branco and Pereira 2002;Peres et al 2010;Cantonati et al 2012;Stancheva et al 2012). In this study, we showed that some architectures of multilayer ANNs were relatively efficient in predicting the species richness and abundance of macroalgae, even in high dynamic systems such as streams.…”

“…Algae abundance has also been treated as a very important metric in the identification of anthropogenic perturbations in aquatic ecosystems, since the excessive increase in algal biomass is one of the most usual effects of eutrophication (Yang et al 2012). Based on this assumption, this parameter of community structure and functioning, used alone or in association with other measures, has been largely applied in biomonitoring studies (e.g., Rakocevic-Nedovic and Hollert 2005;Rier and Stevenson 2006;Stevenson et al 2006;Peres et al 2010). Birk et al (2012) showed, for instance, based on an overview of almost 300 assessment methods, that algal abundance is one of the most used biological metric to evaluate water quality in European lakes.…”

Diversity Assessment of Lotic Macroalgal Flora by the Application of Taxonomic Distinctness Index

“…The results of diversity from TDI found in this study will be discussed considering the main general patterns of stream macroalgal diversity reported in previous studies, including Sheath & Cole (1992) (e.g., Sheath & Burkholder 1985, Branco et al 2009, Peres et al 2010.…”

“…In general, Chlorophyta is reported as the most diverse division of algae in lotic macroalgae communities around the world ( Branco et al 2009, Peres et al 2010). The same tendency was observed in Sheath & Cole (1992).…”