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  • Production and identification of Ulva sp. in multitrophic aquaculture in earth ponds
    Publication . Favot, Glauco; Serrão, Ester
    Waste water from intensive aquaculture can cause eutrophication of coastal waters and subsequent negatively impact downstream biological communities. The use of macroalgae as active biofilter optimizes the reduction of the dissolved nutrient loads in aquaculture effluents. Ulva species with their high growth rates and tissue nitrogen contents are very good candidates for bioremediation besides having an active role on carbon sequestration. This study identified the Ulva sp. cultivated in earth ponds facing the Ria Formosa lagoon (South Portugal), and assessed the biomass production, the SGR (specific growth rate) and CO2 uptake performance of this species. Using DNA barcoding with the markers ITS (internal transcribed spacer) I identified six species of the genus Ulva growing in the ponds, with Ulva flexuosa being the cultivated one. Ulva flexuosa was recorded for the first time in South Portugal. However, taxonomic questions were raised because distinct clades were found for this species using published sequences. Moreover, the ‘lettuce-leaf’ morphotype was observed for the first time for the marine species of Ulva flexuosa. The growth and production performance were tested among: a) two different multitrophic systems (IMTA (fish +oyster + Ulva) and ‘Fish + Ulva’); b) four different initial densities (15 ,30, 50 e 60 g/m2); c) five production and harvest cycles (6, 7, 8, 9 e 15 days). The Specific Growth Rate (SGR) of Ulva flexuosa was found to be significantly different between the two multitrophic systems (p <0.05) and higher in the 'Fish + Ulva' system (19.3 ± 0.08% day-1) than in the IMTA system (16.7 ± 0.8% day-1). Also, there was significant differences between different densities and varied cultivating periods. Growth of Ulva flexuosa was dependent of both densities and time periods. The densities of 30g/m2 revealed to be the best among the four tested densities (23 ± 3.9 % day−1) whereas the optimal cultivating period was between seven and nine days (≈21 % day−1). The annual NPP of Ulva flexuosa was estimated to be of 106 g C m-2 year-1 a value lower than those reported from different Ulva species in other countries. Ulva flexuosa showed to grow well under typical conditions of earthen pond aquaculture. The experiments on the production cycle indicated an optimal period of cultivation of about 8 days. The presence of Ulva flexuosa in the South Portugal broadens its geographic distribution and opens the prospect of using this species in IMTA systems in various parts of the country.
    2017-11-22Dissertação de mestrado Acesso aberto Ver mais