# Determinants of Cyanobacteria and Algae Diversity in Natural Freshwater Micro‐Ecosystems

## TL;DR

This study explores factors influencing cyanobacteria and algae diversity in freshwater micro-ecosystems, finding that site uniqueness relates to lower diversity and higher turbidity.

## Contribution

The study introduces the use of LCBD and SCBD to assess cyanobacteria and algae diversity in neotropical micro-ecosystems.

## Key findings

- LCBD is negatively related to Shannon diversity, turbidity, and luminosity in bromeliad tanks.
- Cyanobacteria and green algae contribute most to species-level beta diversity (SCBD).
- High LCBD values indicate micro-ecosystems needing restoration due to low species richness and high turbidity.

## Abstract

In this context, estimating the contributions of single sites to overall beta diversity (LCBD—Local Contribution to Beta Diversity, i.e., indicator of site's ecological uniqueness) or partitioning overall beta diversity into contributions of individual species (SCBD—Species Contribution to Beta Diversity, i.e., degree of variation of individual species across the study area) has proven to be a good approach to improve the knowledge of drivers of beta diversity. The number of studies on beta diversity in hyperdiverse environments, such as the Neotropics, is still scarce. We explored the contributions of each site and species to the overall cyanobacteria and algae beta diversity of 77 natural freshwater micro‐ecosystems (i.e., tank bromeliads) of a neotropical ecosystem. We observed that LCBD was negatively related to Shannon diversity, turbidity and luminosity (% canopy cover). The negative relationship between LCBD and Shannon diversity indicates that micro ecosystems with less diversity reflect unique characteristics, and LCBD values can predict these environments. In our study, high LCBD values indicated environments in need of restoration, that is, poor in species richness and with greater turbidity and luminosity, showing that most bromeliad tanks presented high species diversity and low turbidity and luminosity.

The Shannon Index, turbidity and luminosity negatively affected the LCBD, species with intermediate frequency of occurrence affected the LCBD, cyanobacteria and green algae are the groups that contribute most to the SCBD, as well as species with accessory frequency. LCBD can indicate microecosystems with greater need for management and conservation.