Carbon sequestration in macroalgal mats of brackish-water habitats in Indian Sunderbans: Potential as renewable organic resource

Nutrient removal and biomass production of marine microalgae cultured in recirculating aquaculture systems (RAS) water with low phosphate concentration

This study was conducted to investigate the feasibility of microalgal biomass production and nutrient removal from recirculating aquaculture systems (RAS) water (RASW) with low phosphate concentration. For this purpose, Nannochloropsis oculata, Pavlova gyrans, Tetraselmis suecica, Phaeodactylum tricornutum, and their consortium were cultivated in RASW and RASW supplemented with vitamins (+V). Among them, N. oculata showed the maximum biomass production of 0.4 g/L in RASW. Vitamins supplementation significantly increased the growth of T. suecica from 0.16 g/L in RASW to 0.33 g/L in RASW + V. Additionally, T. suecica showed the highest nitrate (NO3-N) removal efficiency of 80.88 ± 2.08 % in RASW and 83.82 ± 2.08 % in RASW + V. Accordingly, T. suecica was selected for scaling up study of microalgal cultivation in RASW and RASW supplemented with nitrate (RASW + N) in 4-L airlift photobioreactors. Nitrate supplementation enhanced the growth of T. suecica up to 2.2-fold (day 15). The fatty acid nutritional indices in T. suecica cultivated in RASW and RASW + N showed optimal polyunsaturated fatty acids (PUFAs)/saturated fatty acid (SFAs), omega-6 fatty acid (n-6)/omega-3 fatty acid (n-3), indices of atherogenicity (IA), and thrombogenicity (IT)). Overall, the findings of this study revealed that despite low phosphate concentration, marine microalgae can grow in RASW and relatively reduce the concentration of nitrate. Furthermore, the microalgal biomass cultivated in RASW consisting of pigments and optimal fatty acid nutritional profile can be used as fish feed, thus contributing to a circular bioeconomy.

The effect of incorporating dietary green seaweed (Ulva sp.) on growth performance, blood parameters, and carcass and meat quality characteristics of Jumbo quail

Seaweeds are functional aquatic plants that can be used in Jumbo quail (Coturnix sp.) feeds as sources of phytochemicals and nutrients. However, no studies have investigated the feed value of green seaweed (Ulva sp.) meal (SM) for the Jumbo quail. Thus, the impact of different dietary inclusion levels of SM on productive traits, serum biochemistry, haematology, visceral organ sizes, carcass features, and meat quality attributes in Jumbo quail was investigated. In a completely randomised design, one-week-old quail (n = 385; 67.7 ± 3.44 g body weight) were allotted to five treatments, with seven replicate pens (experimental unit). The treatments were produced by including 0 (SM0), 20 (SM20), 40 (SM40), 60 (SM60) and 80 g/kg (SM80) of green SM in a commercial grower diet. Regression results showed no linear or quadratic effects (P > 0.05) to different levels of SM for average weekly feed intake, overall weight gain, haematological indices, internal organs, carcass features, and meat quality characteristics of the birds. However, incorporating SM up to 80 g/kg in the diet linearly reduced overall gain-to-feed ratio (G:F) [R2 = 0.282; P = 0.0001] and slaughter weights [R2 = 0.159; P = 0.026]. Treatment SM80 promoted (P < 0.05) higher feed intake than diet SM60 in weeks 3, 4 and 5, but were comparable to the control treatment in weeks 4 and 5. Birds fed with diets SM0 and SM20 had higher (P < 0.05) overall weight gain than birds fed with diet SM60. Diet SM80 resulted in lower (P < 0.05) overall G:F (0.250) than diet SM0 (0.277). Higher slaughter weights were observed on SM0 and SM20 groups than the SM60 group. We concluded that the use of dietary green SM up to 80 g/kg in Jumbo quail feeds compromises gain-to-feed ratio and slaughter weights but not physiological and meat quality attributes.

Whole System Analysis Is Required To Determine The Fate Of Macroalgal Carbon: A Systematic Review

The role of marine primary producers in capturing atmospheric CO₂ has received increased attention in the global mission to mitigate climate change. Yet, our understanding of carbon sequestration performed by macroalgae has been limited to a relatively small number of studies that have estimated the ultimate fate of macroalgal-derived carbon. This systematic review was conducted to provide a timely synthesis of the methods used to determine the fate of macroalgal carbon in this rapidly expanding research area. It also aimed to provide suggestions for more effective future research. We found that the most common methods to estimate the fate of macroalgal carbon can be categorized into groups based on those that quantify: (i) export of macroalgal carbon to other environments-known as horizontal transport; (ii) sequestration of macroalgal carbon into deep-sea sediments-known as vertical transport; (iii) burial of macroalgal carbon directly beneath a benthic community; (iv) the loss of macroalgal carbon as particulate carbon or dissolved carbon to the water column; (v) the loss of macroalgal carbon to primary consumers; and finally (vi) those studies that combined multiple methods in one location. Based on this review, several recommendations for future research were formulated, which require the combination of multiple methods in a whole system analysis approach.

Co-Cultivation of Leptolyngbya tenuis (Cyanobacteria) and Chlorella ellipsoidea (Green alga) for Biodiesel Production, Carbon Sequestration, and Cadmium Accumulation

The co-cultivation approach using cyanobacteria-Leptolyngbya tenuis and green alga-Chlorella ellipsoidea demonstrated in the present study showed additive and synergistic effects on biomass yield, biomass productivity, lipid yield, lipid productivity, CO₂ fixation, and cadmium bioremediation efficiency. The results of co-culture in batch mode revealed about 2-3 times increase in biomass and two times increase in total lipid, when compared to the pure culture batches. The results revealed that co-cultures exhibited significantly high CO₂ fixation rate of 2.63  ±  0.09 g/L/d, which is 1.5-2 times better than monocultures (P < 0.05). To explore the bioaccumulation of cadmium by co-cultures and pure cultures, different concentrations of cadmium nitrate was used in flask trials. Cadmium accumulation was observed in the order: co-culture (74%, 0.37 mg/L) > Chlorella (58%, 0.29 mg/L) > Leptolyngbya (50%, 0.25 mg/L) (P < 0.05). In addition, fatty acid composition, CHNS analysis, biodiesel characterization, and biochemical compositions were also determined using co-culture method. The maximum biomass yield, productivity, lipid content, and CO₂ fixation rate in cadmium induced co-culture were 3.95  ±  0.13 g/L, 258.88  ±  15.75 mg/L/d, 41.43  ±  0.71%, and 3.21  ±  0.20 g/L/d, respectively which is 1.2, 1.3, 2.3, and 1.2 times higher than the control (P < 0.05). Cadmium induced changes in growth and lipid yield using co-culture suggests cost-effective and eco-friendly production of biodiesel and carbon mitigation.