Banca de QUALIFICAÇÃO: CAIO VITOR MATOS MOREIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : CAIO VITOR MATOS MOREIRA
DATE: 07/08/2026
TIME: 09:00
LOCAL: Sala de Videoconferência da PoP- RN, Centro de Convivência da UFRN (formato híbrido)
TITLE:

Impacts of geoengineering on semi-arid plankton ecology: structure, resilience, and morphofunctional responses to the use of organic coagulants and a natural adsorbent

KEY WORDS:

eutrophication; lake geoengineering; cyanobacteria; tannin-based coagulants; phosphorus adsorbents; ecotoxicology; “Floc & Sink”; “Floc & Lock”

PAGES: 129
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Eutrophication is one of the major challenges for the conservation and multiple uses of reservoirs, promoting cyanobacterial blooms that impair water quality and ecosystem services. Among the available mitigation strategies, coagulation- and phosphorus adsorption-based techniques have shown high efficiency; however, they still rely predominantly on metallic coagulants and high-cost phosphorus adsorbents. This thesis investigated the efficiency and ecological safety of two tannin-based coagulants, Tanfloc® (TAN), derived from Acacia mearnsii, and Jurema extract (JUR), derived from Mimosa tenuiflora, and evaluated beige limestone (BL) as a lower-cost alternative to lanthanum-modified bentonite (LMB), aiming to contribute to the development of more sustainable eutrophication management strategies for tropical semiarid reservoirs. To achieve this objective, the thesis was structured into four chapters. Chapter 1 investigated how cyanobacterial morphology influences removal efficiency by tannin-based coagulants. Experiments with Microcystis sp., Sphaerospermopsis sp., and Raphidiopsis raciborskii showed mean chlorophyll-a removal efficiencies of 82%, 66%, and 59%, respectively, with a significant interaction among species, coagulant, and dose (F6,48 = 4.58; p < 0.001). Long filamentous cyanobacteria exhibited greater resistance to removal, whereas JUR performed comparably to TAN despite its lower condensed tannin content. The safe operational window ranged from 20 to 100 mg L−1; at 200 mg L−1, pH decreased below 6 and dissolved humic substances increased substantially. Chapter 2 evaluated the acute toxicity of these materials to Notodiaptomus iheringi, a calanoid copepod that is dominant in tropical eutrophic reservoirs. Neither phosphorus adsorbent caused mortality exceeding 50% at any tested concentration, precluding LC50 estimation. The LC50 values for the coagulants were 223.55 ± 44.89 mg L−1 for TAN and 705.41 ± 127.77 mg L−1 for JUR. At the operational doses (50 mg L−1 TAN or JUR combined with 100 mg L−1 LMB or BL), mortality did not differ from the control, indicating low acute ecotoxicological risk under operational conditions. Chapter 3 investigates removal efficiency in natural phytoplankton blooms and the associated morphofunctional patterns using Morphology-Based Functional Groups (MBFG). Preliminary results indicate that TAN consistently removed 66–74% of chlorophyll-a in both blooms evaluated (July 2025 and January 2026), whereas JUR removal efficiency ranged from 85.4% in Bloom 1 to 25.0% in Bloom 2 (p < 0.001), demonstrating a strong dependence on bloom characteristics. BL applied alone did not promote phytoplankton removal in either bloom. The MBFG analyses are currently in progress. Chapter 4 will investigate the effects of sediment capping with LMB and BL on the hatching of dormant zooplankton stages in sediments fromtropical semiarid reservoirs. Overall, the results indicate that the efficiency of these materials depends on the morphofunctional attributes of the phytoplankton community and that, at the identified operational doses, their application poses low acute ecotoxicological risk to zooplankton.

COMMITTEE MEMBERS:
Externa ao Programa - 3442192 - FABIANA OLIVEIRA DE ARAUJO - nullInterna - 2412921 - JULIANA DEO DIAS
Externo à Instituição - JULIANA DOS SANTOS SEVERIANO - UEM
Externa ao Programa - 3508414 - MARIANA RODRIGUES AMARAL DA COSTA - nullPresidente - 1764855 - VANESSA BECKER