The growing concern about the shortage of fossil fuels drives the search for new sources of sustainable energy. Microalgae are considered promising in this area, since they are sources of third generation biofuels and protein. The present study aimed at describing and isolating species from the native phytoplankton communities of four reservoirs in the Pernambuco semiarid, making them available for experiments that can evaluate the biotechnological potential and meet the demands of the region. The collections occurred in water bodies located in the Pernambuco semiarid and the identification of the taxa occurred based on morphological characters using specific literature. A total of twenty-one taxa were identified, eight of them Cyanophyceae (Anabaena sp., Aphanocapsa elachista, Chroococcus dispersus, Dolichospermum sp., Merismopedia sp., Microcystis aeruginosa, Pseudanabaena limnetica, Synechococcus sp.), ten Chlorophyceae (Chlorella sp., Cosmarium bioculatum, Desmodesmus spp., Dictyosphaerium sp., Pediastrum duplex, Pediastrum simplex, Pseudokirchineriella subcapitata, Scenedesmus sp., Staurastrum leptocladum, Trochiscia sp) and only one of the following classes Bacillariophyceae (Aulacoseira granulata), Euglenophyceae (Trachelomonas volvocida) and Dinophyceae (Ceratium furcoides). The bioprospection of microalgae in the semiarid region of Pernambuco has made possible the formation of a bank of strains, important for fictional studies and obtaining biomass of species with biotechnological potential.

Integrated multitrophic aquaculture (IMTA) emerges as a sustainable strategy to control the excess of solids and inorganic nutrients that tend to increase in the biofloc system (BFT) cycle, since the model integrates organisms from different trophic levels sharing the same system and nutrients. Thus, this study compared a Penaeus vannamei monoculture system with an integrated biofloc system including Mugil liza, Holothuria grisea, Crassostrea tulipa, and Salicornia neei, focusing on water quality and the performance of organisms and systems. This study consisted of three monoculture systems (16 m³; 375 shrimp m⁻³) and three IMTA systems, composed of a shrimp tank (16 m³), a mullet tank (4 m³; 30 ind m⁻³), a combined tank (3 m³) for oysters (45 ind m⁻³) and sea cucumbers (3 ind m⁻²), and a Salicornia neei bed (2.78 m²; 37 ind m⁻²). All IMTA systems operated in recirculation without water exchange, using 10% of the established biofloc inoculum. The IMTA system had half the hydrated lime use (2.13 vs. 4.29 kg), lower solids (299.56 vs. 373.33 mg L⁻¹), and reduced sludge production (9.37 vs. 15.87 kg). Shrimp growth was similar in both systems. Mullet grew adequately with a survival rate of 95.8%, but oysters showed a survival rate of 45.7%. Sea cucumber had a survival rate of 100% until day 28, when a marked decline appeared, strongly correlated with rising temperature (>28 °C; r = −0.71). This resulted in a significant increase in solids in the last weeks, suggesting that the population decline reduces solids control capacity. Furthermore, the biofloc in IMTA was dominated by coccoid forms, with lower proportions of filamentous and cyanobacterial forms.

This study evaluated the salinity tolerance of the macroalga Ulva ohnoi cultivated in a biofloc system over a 14-day period. Five salinity treatments (10, 15, 20, 25, and 30‰) were tested, using 40-L tanks. Algae were acclimated to the target salinities before the cultivation phase and stocked at the density of 2 g∙L-1. Water quality parameters (ammonia, nitrite, nitrate, orthophosphate, alkalinity, and pH), biomass gain, daily growth rate, phenolic compounds, chlorophyll, and carotenoids were evaluated. Water quality remained within acceptable ranges across treatments, although alkalinity showed significant differences. Complete mortality of U. ohnoi was observed at 10‰, and reduced growth was recorded at 15‰. In contrast, salinities of 20, 25, and 30‰ supported higher biomass gains and daily growth rates, with no significant differences in antioxidant compound concentrations among these treatments. Growth was significantly higher at salinities of 20–30‰, with biomass gains of 318–400 g and daily growth rates of 5.4–6.4% day-1, whereas at 15‰ biomass gain reached only ~111 g and growth rate ~1.2% day-1. These findings highlight the potential of U. ohnoi for integration into low-salinity biofloc systems and multitrophic aquaculture strategies, contributing to sustainable aquaculture practices by recycling nutrients and producing valuable biomass.