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The relation between phytoplankton diversity and light availability: a case study for the floodplain of the Amazon Basin

Grant number: 19/15984-2
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): September 01, 2019
Effective date (End): August 31, 2021
Field of knowledge:Interdisciplinary Subjects
Cooperation agreement: Belmont Forum
Principal Investigator:Evlyn Márcia Leão de Moraes Novo
Grantee:Cleber Nunes Kraus
Home Institution: Instituto Nacional de Pesquisas Espaciais (INPE). Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brasil). São José dos Campos , SP, Brazil
Associated research grant:18/12083-1 - Balancing biodiversity conservation with development in Amazon wetlands - bonds, AP.R

Abstract

The hydrological phases are linked to the spatial and temporal changes influencing the ecological processes and the biodiversity of the floodplain systems. In the flood phase, the waters invade the floodplain oxygenating, bringing nutrients and giving rise to a terrestrial/aquatic transition area responsible for the environmental conditions favorable to biodiversity. In general, there are two peaks of primary productivity. The first occurs in flood due to the entry and release of nutrients accumulated in the dry period. This peak is replaced by low primary productivity during flood due to the process of dilution and increase of the depth lakes. During the ebb phase, the decrease in depth combined with the resuspension of autochthonous organic material promotes a second peak in primary productivity. In the low water phase, floodplain lakes have a smaller volume of water that is easily affected by the wind. This increase the turbidity, and creating considerable optical and limnological heterogeneity within the same area. These processes, throughout the hydrological year, support the nutrient needs such as nitrogen, phosphorus, and carbon compounds, which play an essential role in phytoplankton development.In aquatic environments, the phytoplankton community competes for nutrients and light that, together with other ecological interactions, contribute to the structuring of phytoplankton diversity. Light decreases vertically from the surface, while most nutrients are supplied from the bottom, forming a vertical gradient in the opposite direction of light. Diverse anthropogenic interventions, such as population growth and the expansion of agropastoral activities, can influence nutrient uptake, causing changes in phytoplankton diversity.In this context, the research seeks to answer the following questions: What is the impact of light availability on the water column on the abundance of phytoplankton groups in the Amazonian floodplains? To answer the question, we select the lake complex that makes up Lago Grande do Curuai (LGC), the lakes of the Mamirauá Sustainable Development Reserve (RDSM) and the lowland lakes of the Extractive Reserve (RESEX) of the Juruá middle. The first step will be to collect available phytoplankton taxonomy data to evaluate the existence of a relationship between biodiversity indexes and Secchi depth, already available from the BONDS team. In situ data collection missions will be carried out for the following variables: remote sensing reflectance, diffuse attenuation coefficient (Kd), phytoplankton samples for species determination and their density, water samples for the determination of optically active components and Remote Sensing Reflectance. These missions will be carried out in the RESEX Lakes and in the LGC region, which is characterized by distinct environmental and anthropogenic characteristics.RESEX lakes are deep, closer to the origin of the sediments, suffer more influence from the climate systems of the southern hemisphere and have preserved flood forest with low anthropogenic pressure. On the other hand, the LGC already has almost 60% of its original and secondary forest cleared, and the area of occupation by cattle ranching has been increasing. The missions will be carried out mainly in the phase of ebb in a date that coincides with the passage of the satellites Landsat and Sentinel. We will then develop models that allow relating the phytoplanktonic biodiversity to the optical diversity of Kd measured in situ. Once it is possible to calibrate a model capable of estimating phytoplankton biodiversity from optical diversity, we will apply the model in the other lakes of the plain. The development of a biodiversity indicator based on satellite images could be an essential tool for the remote monitoring of the anthropogenic and climatic impact on phytoplankton biodiversity.