Climate change and coral ecosystem resilience: evaluating the impacts of metallic nanoparticles and harnessing climate-induced algal blooms for sustainable marine and energy solutions.

Abstract

The current problem of algae blooms is the excessive growth of sargassum and the presence of the green tide. These problems generated by anthropic processes develop alterations in marine ecosystems. In this study, we want to take advantage of the problem of algal blooms to use them as raw materials to obtain biopolymers or polysaccharides. The increase in the green tide, as the overpopulation of the <em>Ulva sp.</em> algae is known, helped us develop a novel method for extracting the polysaccharide from this alga, called Ulvan, which is highly sulfonated with a negative charge. It has exceptional potential in biomedical and biomaterials applications, but expensive, cumbersome, and extensive extraction and purification processes hinder its exploitation in this context. Herein, we explore an automated, rapid, and efficient extraction procedure for this polysaccharide using accelerated solvent extraction (ASE). ASE uses high pressures and temperatures to increase the solubility of analytes while decreasing solvent viscosity, thereby improving extraction efficiency and time, performing extractions on multiple samples in the same run. This work compares the ASE extraction method with the hot water extraction (HWE) method, a conventional extraction method, and the microwave-assisted extraction (MAE) method, a new method. The purity of the polysaccharides extracted by ASE, HWE, and MAE is compared to a high-purity commercial standard. The process was divided into three steps; the first two were the purification pretreatment with dichloromethane and acetone. Here, the pigments and fatty acids are extracted. The third step is hot water extraction, where the Ulvan polysaccharide is obtained. The same procedure was carried out to obtain sodium alginate from sargassum. Still, the final solid was left stirring in sodium carbonate (Na₂CO₃) to get the sodium alginate polysaccharide from the supernatant. Finally, the characterization for the identification of the polysaccharides was carried out by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), and thermogravimetric analysis (TGA) to confirm the Ulvan. Sodium alginate was characterized by FTIR, Differential scanning calorimeter (DSC), and Energy dispersive X-ray spectroscopy (EDS) to confirm the presence of alginate. Compared to others, this novel method is more cost-effective, faster, efficient, and automated and may allow more researchers to use polysaccharides for many applications.PDF Abstract - Amid climate change, we find one of the primary sources of pollution: runoff, which carries leached materials products of anthropogenic activities, from the immersion of novel nanomaterials to organic material to bodies of water such as the seas, affecting marine ecosystems. The studies in this thesis show how high-precious nanomaterials, such as gold and Titanium, a product of biological treatments, affect vulnerable organisms such as corals when reaching these ecosystems. When the gold reaches the sea, we see that it develops very adverse effects on the coral. In this study, the coral affected by gold nanoparticles dies in a short period.<br /> <br /> The study of titanium nanoparticles linked to a citrate complex (Ti(citrate)(IV)) demonstrated that initially, the coral interacts in a non-invasive way, even the analyses demonstrate an improvement in exposure, being that when Titanium is separated from the citrate, the adverse state it produces is seen.<br /> <br /> On the other hand, the mitigation of algal blooms, a product of the leaching of organic material, deepens the problems of marine ecosystems. To reduce the impact, studies were developed to extract materials from algae, one of the main ones being polysaccharides, which are sugars that contain the cellular structures of algae. A novel extraction method was developed, where the extraction time could be reduced, fewer solvents would be used, and more excellent polysaccharide recovery through the accelerated solvent extraction method. The polysaccharides obtained proved to have promising applications, first in retaining pigments to produce membranes and use them in treating coral and second in developing solid-state electrolytes with potential battery applications.