Distribution, composition, and abundance of protozoa in Burullus Lake, Egypt, and relationships with environmental variables

The spatial patterns of planktonic protozoa communities were studied from April 2015 to March 2016 in Burullus Lake, Egypt, in order to assess its environmental status. Protozoa were sampled and 13 environmental variables were measured monthly at ten stations. Over the study area, non-tintinnid ciliates dominated the protozoa community (annual contribution 49.3%) followed, in order, by amoebozoans (31.6%), tintinnids (15.2%), and foraminiferans (3.9%). A total of 35 species of protozoa were identified, and four of these species formed the main bulk of the entire community (with a percentage >47%), namely Vasicola ciliata (14.55%), Centropexis aculeata (11.34%), Acropisthium mutabile (11.21%), and Amphileptus claparedie (10.29%). The highest species number and diversity index values (17 species, H′= 2.03) were found at station I in the saline (average 29.4 ppt) and lowest trophic region of the lake. Univariate and multivariate analyses demonstrated that: (1) the environmental status of Burullus Lake fluctuated between eutrophic and hypertrophic; (2) the lake is divided into three main regions (A, B, and C) based on spatial similarities among environmental variables (the most stress-exposed was Region B, followed, in order, by C and A); (3) the spatial distribution of the protozoa communities was correlated with environmental variables, especially nitrogen nutrient concentrations and phytoplankton biomass in Region B, salinity and dissolved oxygen in Region A, and transparency in Region C; (4) Centropyxis aculeata and Vasicola ciliata were positively correlated with nutrients, and phytoplankton biomass in Region B, which receives large amounts of anthropogenic inputs. Thus, we proposed the use of these two protozoans as potential bioindicators of eutrophication in Burullus Lake.