É sustentável? Uma análise dos cultivos de macroalgas marinhas no estado do Rio Grande do Norte

Abstract

The seaweed cultivation has been encouraged as an alternative to harvesting in natural beds as well as being a possibility of generating income, reducing the exodus, unemployment, family breakdown and valuation of women's role in generating income and participation of community organization. The aim of this study was to evaluate the sustainability of seaweed aquaculture of Rio Grande do Norte. The analysis considered socioeconomic, technological, and environmental aspects. The research was characterized as a case study, which qualitative and quantitative parameters were evaluated. Data were collected through semi-structured interviews, directed to the seaweed farmers, the presidents of the mariculture associations and aquaculture specialists. The collected data were used to characterize the associations, to identify the socioeconomic profile of the farmers, and to calculate the IDES, ICS, IT, IA and IS indexes. To improve the cultivation technique of Crassiphycus birdiae, an experiment was carried out using the nutrient pulse method. Thirteen treatments were tested, one control and 12 resulting from combinations of four concentrations (0.75 ml/L; 1.5 ml/L; 3.0 ml/L; 6.0 ml/L) of an agricultural fertilizer (VitanTM) and three exposure periods (12h; 24h; 48h). After the period of exposure to the nutrient pulse, the propagules were grown in sterilized seawater for four weeks. The effect of nutrient pulse on growth rate was analysed. The obtained results in the sustainability analysis of the mariculture activity were: High-level Index of Economic and Social Development (IDES – 0.931); Medium level Index of Social Capital (ICS – 0.759); High-level Index of Technology (IT – 0.836); Medium level Index of Environment (IA – 0.633) and medium level Index of Sustainability (IS – 0.790). In assessing the nutrient pulse effect, a progressive increase in the values of fresh biomass and growth rate was observed in all treatments, except for T13, treatment with higher concentration and higher period of exposure fertilizer. The highest increase in fresh biomass and growth rate was found in the T3 treatment (1.5ml/L; 12h), however the statistical analysis did not show any significant difference.