Métodos de imageamento e análise do plâncton para monitoramento das variações temporais em multiplas escalas

Abstract

Part of planet Earth is covered by oceans, with its marine biodiversity composed mainly of planktonic organisms and its great relevance for humanity in the production of food and oxygen. To study these organisms in a long term allows to understand changes in the ecosystem. In this scope, the present work had the following objectives: to develop a protocol for automatic classification and counting of plankton in the Loki and FlowCam imaging systems; to develop a new diversity index to work with classes of images on the website ECOTAXA; to evaluate possible correlations between temporal variations in the structure of a community (betadiversity-ECOTAXA); and to apply the parameters of abundance and average size of the organisms as indicators of changes in the natural cycles of temporal and seasonal variations of populations of the holoplankton. To carry out the study described in the first chapter, the images were obtained on November 27, 2015, with the Lightframe On-Sight Keyspecies Investigation System (LOKI), and in the two other chapters, laboratory images were obtained from samples collected weekly between the years of 1998 and 2015, on Cabo Frio Island in Arraial do Cabo, RJ. In the first chapter, one of the algorithms tested for automatic characterization was statistically better by the dissimilarity test, with a success rate of 96%. In the second chapter, the results showed a variation in the diversity of image classes over time, between 0.38 and 2.04 (±0.28SD) bits.class-1. An annual increase in temperature was also observed, accompanied by an increase in diversity. In the third chapter, the Shift from a diatom dominant to a dinoflagellate regime indicates the distinct responses these organisms have to certain environmental conditions. Dinoflagellate species, unlike diatoms, are specialists in ecosystems with higher salinity and temperature and low concentrations of nutrients. Unlike zooplanktonic groups – copepods and cladocerans – dinoflagellates are considered opportunistic types of phytoplankton that tend to abrupt changes in ecosystems such as the upwelling phenomenon.