Browsing by Author "McGovern, Malachy"
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- Cultivation of the red seaweed Kappaphycus alvarezii using biofloc effluentPublication . Pires, Clovis Murilo; Bazzo, Giovana Carolina; Barreto, Pedro Luiz Manique; do Espirito Santo, Carlos Manoel; Ventura, Thallis Felipe Boa; Pedra, Anna Gabrielle La Macchia; Rover, Ticiane; McGovern, Malachy; Hayashi, LeilaThe aim of this work was to evaluate the use of effluent from a Biofloc System (BFT) as a fertilizer for the red seaweed Kappaphycus alvarezii cultivated in tanks and analyze its influence on carrageenan yield and quality. Firstly, the optimum effluent concentration and period for enrichment were determined by an in vitro study. The seedlings were then cultivated for 7 days in two different culture media: 50% von Stosch solution (V) and 25% BFT (B), both diluted in sterilized seawater. Seaweeds cultivated only in sterilized seawater were used as a control (C). After this period, all plants were grown in only sterilized seawater for a further 28 days. Seedlings from V (1.05 +/- 0.02% day(-1)) and B (1.13 +/- 0.01% day(-1)) showed no significant differences in growth rates, being both higher than the control (0.91 +/- 0.06% day(-1)). Seedlings from V and B also removed a greater quantity of nitrate (58.39% and 22.97%, respectively). Seedlings from V removed 100% phosphate, while those from B removed 83.58%. The tissue nitrogen content was higher only in the V. Although no significant differences were observed among treatments in the carrageenan yield, significantly higher gel strength and viscosity were observed in B (248.85 g cm(-2) and 19.89 mPa s, respectively). According to the results, BFT effluent can be used to replace von Stosch solution to grow K. alvarezii in tanks. At the same time, the seaweed, together with bacteria and microalgae from the effluent, can be an effective biofilter in IMTA systems using bioflocs.
- Domestication of the green seaweed Ulva ohnoi aka `sea lettuce´ for Biofloc effluent bioremediationPublication . McGovern, Malachy; Mata, Leonardo; Hayashi, LeilaThe green macro algae Ulva spp. (Chlorophyta) is being increasingly used in Integrated Multitrophic Aquaculture (IMTA) due to its rapid growth rate and efficiency in the sequestration of excess nutrients. This study tested and evaluated the growth performance of Ulva ohnoi in various concentrations of marine shrimp biofloc effluent (Litopenaeus vannamei). In the first growth experiment, 29mm Ulva discs were cultivated in 1L flasks containing biofloc effluent at 25% [BFT25], 50% [BFT50], 75% [BFT75] and 100% [BFT100] and compared to a seawater control containing 8mL von Stosch standard solution per litre [VS8]. The mean specific growth rates (SGR) after 3 weeks cultivation were [VS8]: 13.14% per day-1 , [BFT25]: 13.63% per day-1, [BFT50]: 14.08% per day-1, [BFT75]: 13.85% per day-1 and [BFT100]: 12.96% per day. From week 3 to week 4, the treatments [BFT25] and [BFT50] showed no growth whilst plants in [BFT75] and [BFT100] treatments continued to grow at a reduced rate of 2.45% per day-1 and 3.35% per day-1 respectively, which was not significantly different from the [VS8] control at 1.71 % per day-1 (p>0.05). The results indicate that the higher nutrient budgets of [BFT75] and [BFT100] continued to support algal growth at higher stocking densities by attenuating the effects of self-shading and stress, demonstrating similar performance to a formulated high-nutrient solution (von Stosch). In the second growth experiment, 19mm discs were cultivated in 1L flasks containing 25% [BF25], 50% [BF50], 75% [BF75] and 100% [BF100] biofloc effluent and compared to a seawater only control [FSW] and a second seawater control containing 10mL von Stosch standard solution per litre [VS10]. During week 1, the [BF75] demonstrated the highest mean specific growth rate (SGRmax) of 25.49 ± 3.23 % per day-1 which was significantly higher that the [FSW] control (p<0.05) and the highest observed growth rate of the study. At the end of the 4 week experiment no significant difference in growth rates was observed between plants in the biofloc treatment groups (p>0.05). During experiment 2, [BF50] reduced levels of TAN by 71.3% in week 1 and by 24.83% in week 2. Nitrite was reduced by 42.73% in week 1 and 28.38% in week 2. Nitrate was reduced by 13.98% in week 1 and 33.3% in week 2. Phosphate was reduced by 13.98% in week 1 and 52.63% in week 2. The results indicate the species’ preference for TAN over nitrate however the study found that sporulation events can release TAN into the medium which has implications for biofilter efficiency and bioremediation. In the sporulation experiment, 5mm Ulva ohnoi discs were excised from a plant acclimatized in FSW enriched with 10mL/L von Stosch (VS10). The discs were placed in petri dishes containing 15 mL of FSW and then subjected to 4⁰C cold shock for [10 mins], [20 min], [1 hour] and [2 hours]. A control treatment was given no cold shock and placed in FSW [FSW control] and a second control was given no cold shock and placed in fresh VS10 medium [VS10 control]. Combined 4°C cold shock [2 hours] and low nutrient shock proved highly effective at inducing a mean rate of sporulation of 90% after 5 days. However, this was not significantly different from low nutrient shock alone (i.e. transfer from VS10 to standard FSW [FSW control]) which caused a mean reproductive output of 76.66% (p>0.05). The results suggest that cold shock treatment is not financially viable however further experiments with plants taken from cultivation in [BF50] or [BF75] are recommended.