Periphytic algae biomass at different shading levels: an experimental approach

Aim Light is an essential component in the process of synthesis of organic compounds by photosynthetic organisms. Assuming that a higher level of luminosity would positively influence the production of biomass, we evaluated the influence of different levels of shading on the biomass of periphytic algae, through an experimental study. Methods Glass slides were used for this as an artificial substrate for the colonization and succession of algae in Garças Lake, on the upper Paraná River floodplain, and later transferred to nine aquaria. These were divided into three treatments: three without cover (AC), three with 50% shading screens (A50) and three with 80% shading screens (A80). Abiotic variables (pH, conductivity, turbidity, temperature and dissolved oxygen) and biomass were measured every five days for 15 days. The biomass was evaluated using the chlorophyll-a method. Concentrations of total phosphorus, phosphate, total nitrogen, nitrate and ammoniacal nitrogen were evaluated every five days. Results There was no significant variation of the biomass over time, however, there is a significant difference between the treatments. The highest biomass was found in the control treatment and the lowest was found in the treatment with 80% shading. The other limnological variables evaluated did not show significant changes over time. Conclusions The abiotic variables did not influence the biomass of the phycoperiphyton community, which was influenced only by luminosity. Thus, we conclude that light is a variable with direct influence on the production of periphytic biomass. At low intensity it is a variable that can limit the production of biomass. In high intensity however, it influences by increasing its production.

Species composition, substrate specificity, and seasonal abundance of periphytic algae in a tropical riverine system Periyar, India

The study was conducted to assess the species composition, substrate specificity, and seasonal abundance of periphytic algae from the river Periyar. Monthly samples were collected for one year (June 2016 – May 2017) from different substrates of five selected stations. Eight physicochemical variables such as temperature, dissolved oxygen, pH, conductivity, chloride, sulfate, nitrate, and phosphate were also monitored during the study. Taxonomic studies recorded 156 species of periphytic algae belonging to 56 genera, 36 families, and 5 classes. Naviculaceae was the most abundant family followed by Fragilariaceae and Pinnulariaceae. The principal component analysis revealed the dominance of periphytic algae in the pre-monsoon period. Canonical correspondence analysis indicates pH, conductivity, and sulfate plays a crucial role in periphytic algal assemblages. Correspondence analysis and percentage abundance among different substrates showed the preference of leaf substrate for primary colonization and subsequent succession. The study signifies the importance of substratum and environmental variables in the dynamics of periphytic algal community composition and abundance.

The spatial pattern of periphytic algae communities and its corresponding mechanism to environmental variables in the Weihe River Basin, China

Periphytic algae is a useful indicator of aquatic ecological conditions. We investigated the periphytic algae on natural substrate and the environmental variables at 44 sites on three river systems in the Weihe River Basin (WRB). A total of 84 species are identified, representing 37 genera. The most common genera were Navicula, Oscillatoria, Nitzschia, Scenedesmus, Cymbell, and Fragilaria. One-way analysis of variance (ANOVA) indicated significant differences among the three river systems in environmental variables (p < 0.05). Non-metric multidimensional scaling (NMDS) analyses also showed differences in periphytic algae communities in the three river systems (p < 0.05) and identified different dominant species in each river system. Canonical correspondence analysis (CCA) and Monte Carlo permutation tests revealed that nutrient concentration, WT, and altitude were the most important variables affecting the structure and distribution of periphytic algae communities. Chemical variables were the most accounted for environmental variables (12.5%), while physical variable and geographical factors (5.8% in total) play a relevant minor role. Our results demonstrate that Navicula pupula, Navicula radiosq, Nitzschia palea, and Nitzschia denticula, exhibiting wide ecological amplitude, are tolerant of high concentrations of nutrient pollution. Variation of periphytic algae communities in WRB is due to the combination of anthropogenic and natural factors including agricultural and domestic wastes water inputting, land use patterns, geology, climatic changes, and river hydrology.