Composition, frequency and seasonal distribution of periphytic microalgae in stretches of the Curiaú River, Amapá, Eastern Amazon

Abstract

Periphyton communities are composed of microorganisms loosely attached to the substrate, including fungi, bacteria, microinvertebrates, and mostly microalgae. Due to their photosynthesizing component, they are important primary producers that subsidize the aquatic trophic chain. This study aimed to verify the composition, frequency, and seasonal distribution of periphytic microalgae in stretches of the Curiaú River, located in the Environmental Protection Area (APA) of the Curiaú River, in the State of Amapá. For this, quarterly collections were carried out comprising the months of June 2016 to October 2017, during the dry and rainy seasons. The periphyton algal communities were obtained by squeezing parts of two macrophytes species, Eichhornia crassipes Mart. (Solms) and Pistia stratiotes L. The data were statistically treated using absolute values and the Kruskal-Wallis test, the latter considering the distribution of richness between sites and sampling periods (significance level of α=0.05). A total of 64 taxa were inventoried, aggregated into three taxonomic divisions: Chlorophyta (n=48; 75%), Cyanophyta (n=12; 18.75%) and Heterokontophyta (n=4; 6.25%). In class terms, Zygnematophyceae had the highest number of taxa (n=42; 65.63%), followed by Cyanophyceae (n=12; 18.75%), Chlorophyceae (n=5; 7.81%), Bacillariophyceae (n=4; 6.25%) and, finally, Ulvophyceae (n=1; 1.56%). Of the total number of inventoried taxa, 64.06% (n=41) presented sporadic frequency. Species richness was influenced by seasonality, as higher values were associated with the rainy season (p<0.05). This research is a contribution to the phycology of the Amazon region, especially in its pioneering for the state of Amapá.