Avaliação da eficiência das algas Tetraselmis tetrathele e Nannochloropsis oculata para produção de oxigênio

Abstract

In recent decades, there has been growing concern about the excessive emission of polluting gases into the environment, including carbon dioxide (CO2). CO2 is essential for life on the planet, but it is considered a devastating gas when released in excess, generating major imbalances, such as ocean warming, significant climate change, atmospheric pollution, among others. With this disorderly advancement, the use of microalgae is particularly effective in purifying the air and reducing carbon dioxide emissions in urban areas. Thus, microalgae are essential organisms for the production of oxygen, sustaining life in aquatic ecosystems and contributing to the global health of the environment. They contribute to the mitigation of climate change by sequestering carbon in the carbon cycle, together with their use in bioremediation processes to remove pollutants from water, such as heavy metals and excess nutrients. Therefore, this work aimed to study the efficiency of two species of microalgae, Nannochloropsis oculata and Tetraselmis tetrathele, which are responsible for the large production of oxygen in the environment. Nannochloropsis oculata has a high rate of photosynthesis due to its wide distribution in the oceans and freshwater, and is therefore crucial for the carbon cycle, where it absorbs carbon dioxide, releasing oxygen. Tetraselmis tetrathele is also found in salt water, but in more specific regions, since this species, unlike the first, does not resist waters with very high temperatures and high levels of luminosity. With these two species, the concentration of dissolved oxygen (D.O.) was determined and, subsequently, the rate of photosynthesis through the variation of dissolved oxygen in the liquid mass, which reflect the biological balance between photosynthetic production and consumption for respiration, and the physical balance through atmospheric exchanges of oxygen at the air-water interface. Based on these conditions, the aim was to determine which of the two microalgae studied contributed most significantly to oxygen production. Analysis of the results indicated that the microalgae Tetraselmis tetrathele presented greater efficiency in the production of dissolved oxygen (DO), due to its stability in the face of pH variations and its ability to utilize nutrients progressively, even under conditions of limitation. In contrast, Nannochloropsis oculata demonstrated physiological stress, with an early reduction in photosynthetic activity, possibly aggravated by a slight drop in temperature during the experiment, since the species performs better at higher temperatures. The absence of replacement of Guillard's formula reinforced the adaptability of T. tetrathele, which maintained high photosynthetic efficiency even under restricted nutritional conditions.