Taxa de sedimentação do fitoplâncton varia de modo espécie-específico, influenciada por fatores ecológicos

Abstract

Phytoplankton sedimentation means its upper disappearance from illuminated layer and its arrival on the bottom. That process is acelerated by aggregates formation. The aggregate has a different type of cells, organic or inorganic particles, and, also, a rapid phytoplankton sedimention than expected for a single cell. Thus, the phytoplankton sedimentation plays an important role in the biogeochemistry of aquatic ecosystems, affecting the distribution and transfer of chemical elements over water column and food chain. However, the phytoplankton has strategies to minimize its losses by sedimentation. Many of those are linked to their morfology, allowing species to thrive over lakes and oceans. Thus, the great phytoplankton morphological diversity demand different sedimentation velocity. The study aimed: 1 – to explore, by scientific literature revision, the phytoplankton sedimentation by their morphology and biogeochemical cycles effects; 2 – to evaluate how different phytoplankton sedimentation is affected by light availability. The scientific literature review was supported by scientific lecture essentially published in English, searching for the phytoplankton term linking to the sedimentation, sedimentation and sinking terms. The studies found allowed to explore the phytoplankton aggregates and the biogeochemical cycles relationship. It was observed an important participation of phytoplankton in the biogeochemistry of the aquatic system. The role of the aggregates is even special, because that has only phytoplankton but also bacterial populations growth. Aiming to meet objective 2, subsurface water samples were collected in two urban lagoons in Belo Horizonte (Lagoa da Pampulha and Lagoa do Nado) and applied to different light conditions. The sedimentation rates of different species were determined by the vertical distribution of cells over settling columns (SETCOLs) applied to a) Without Light (SI), b) With Upper Light (ISS) and c) With Light (IT) condition. One-way Analysis of Variance (One-way ANOVA) was performed, followed by the Tukey test. The results allowed to conclude that there is an important phytoplankton community and biogeochemistry ecological relationship. Understanding climate change, biogeochemical cycles and phytoplankton sedimentation stretch conservation strategies. The phytoplankton sedimentation velocity over the water column is species-specific, without any pattern. The morphological diversity and wide geographic distribution of phytoplankton influences their sedimentation rates.