For biofuels and nutraceuticals, the green microalga Haematococcus pluvialis (Chlorophyceae) is a prospective source of biomass and lipids. This study examined how biomass production and lipid accumulation were affected by temperature (10 °C, 20 °C, and 30 °C) and potassium nitrate (KNO₃) concentrations (0.41 g/L, 0.31 g/L, 0.21 g/L, 0.10 g/L, and 0). The findings showed that the largest biomass (0.665 ± 0.200 g/L) was produced at a potassium nitrate concentration of 0.21 g/L at 20 °C, whereas the highest lipid content (46.31 ± 0.026% dry weight) was produced at a temperature without nitrate. Notably, a balanced result was obtained with a modest nitrate content (0.10 g/L) at 20 °C, yielding significant biomass (0.560 ± 0.136 g/L) and lipids (40.30 ± 0.012% dry weight). These results highlight how crucial it is to optimize cultivation settings in order to increase H. pluvialis's dual productivity, offering important new information for its industrial-scale use. By adjusting growing conditions, this research helps meet the need for renewable resources worldwide by promoting the production of high-value bioproducts and sustainable, commercially viable algae-based biofuels.

This study aimed to supply three foods to the crab Callinectes sapidus in its juvenile stage and compare their effects on its growth. For that, crab larvae were cultured from oviparous adult female crabs. The larvae (z₁–z₈) were fed with rotifers, previously cultured with microalgae and megalopae (Meg.) with live Artemia salina larvae, obtained from fresh cysts until they reached juvenile development (c₁, first crab). Then, 270 animals (c₁) were analyzed in three groups of 90, with different diets: shrimp (Penaeus vannamei; Group 1), squid (Mastigoteuthis flammea; Group 2), and tilapia fish (Oreochromis niloticus; Group 3). After 90 days of feeding regimens, the sizes of juvenile crabs were measured by microscopy, and the following relationship was found (p < 0.001): Group 1 (20.8 ± 0.7) > Group 2 (14.5 ± 0.9) > Group 3 (10.4 ± 0.6). The nutritional factor played an essential role in this size differentiation. This intelligent and differentiated feeding strategy showed us that shrimp could be an essential source for the growth of crabs in the juvenile stage. This new approach to safe and efficient roost feeding can classify crabs by size for further hormonal, molting, and reproductive studies.

Reductions in the size of mature blue crabs, Callinectes sapidus, which are commercially harvested, are of concern to the aquaculture industry. Through their role in the production of viable offspring, aquaculturists focus their attention in particular on female crabs, although the phenomenon will, of course, also affect the males. Meanwhile, decreases in size at maturity throughout the crab population may be the result of temperature alterations, at present also due to global climate change. Temperature-based shifts in growth can lead to changes in reproductive efficiency, as well as in size and age at maturity. In this study, the effects of temperature on the moulting frequency of blue crabs were investigated and survival rates have been calculated. The purpose of this study was to investigate the temperature dependence of survival and of the moulting processes for blue crab larvae, and to determine the effect of increasing temperature on moulting. The stages from zoea-1 to zoea-5 were examined at 16, 22, 26 and 30°C. The results show that there is a significant difference in growth and moulting, depending on the rearing temperature. As the temperature increases, the interval between moulting days can be seen to be shortened, and increasingly so with the progress in the growth of the crabs. Moulting-interval days became less with the growth of the crabs. The effect of a rise in temperature on growth per moult is also significant, and along the temperature range tested the optimum temperature was found to be 26°C. A reduction in the length of the intermoult period was observed from the lowest to the optimum temperature, while a sudden, sharp increase in the intermoult period above 26°C was observed as well.

This study aimed to develop a sustainable method for synthesizing quantum dots (QDs) from crab-derived chitosan waste and evaluate their potential applications in marine environmental monitoring and aquaculture. We employed a microwave-assisted green synthesis protocol where chitosan extracted from local crab processing waste was dissolved in 1% acetic acid, subjected to microwave digestion (180 °C, 20 min), neutralized to pH 7, and purified through centrifugation, filtration, dialysis, and lyophilization at − 68 °C. Comprehensive characterization using multiple analytical techniques (AFM, FTIR, XRD, UV–Vis, photoluminescence) revealed QDs with uniform size distribution (2–4 nm), crystalline structure (62% crystallinity index), high quantum yield (46 ± 3%), and exceptional stability in marine environments (87% fluorescence retention in 3.5% NaCl). The QDs demonstrated excellent shelf-life (> 90% activity after 6 months at 4 °C) and photostability (8% reduction after 6 h of continuous UV exposure). Performance testing confirmed their effectiveness for water quality monitoring (detection limits 0.5 μM for Hg²⁺, 0.8 μM for Pb²⁺), antifouling applications (78% biofilm reduction), and pollutant remediation (adsorption capacities 187 mg/g for methylene blue, 142 mg/g for Cu²⁺). We conclude that crab-derived chitosan QDs represent a viable circular economy approach to transform seafood industry waste into high-value nanomaterials with significant applications in sustainable aquaculture and marine environmental protection, supporting blue economy innovation through waste valorization while reducing environmental impact.

Blue crab aquaculture faces challenges in optimizing feed formulations that balance nutritional requirements with sustainability. This study evaluated three innovative feed formulations incorporating unique ingredient combinations: a specialized high-protein formulation using novel protein hydrolysates (D1), a marine-based diet enriched with bioactive compounds from sustainable sources (D2), and an advanced plant-based formulation with enhanced digestibility through fermentation (D3). Growth performance, survival, energy conversion efficiency, molting frequency, and meat quality were assessed over 16 weeks. The marine-based diet (D2) achieved superior results with 92% weight gain and 95% survival rate, significantly outperforming the commercial control. This research demonstrates the potential of novel ingredient combinations and processing techniques in enhancing blue crab aquaculture productivity while addressing sustainability concerns.