Oral Presentation Freshwater Sciences 2023

Management of harmful costly Raphidiopsis raciborskii blooms in a warmer, eutrophic and water scarce world: a case study from the Brazilian semi-arid (#334)

Rafael L Macêdo 1 , Fernanda Daniela M de Oliveira 2 , Betina Kozlowsky-Suzuki 3
  1. Graduate Program in Conservation and Ecotourism / UNIRIO, Rio de Janeiro
  2. Federal University of Rio de Janeiro State - UNIRIO, Rio de Janeiro
  3. Department of Ecology and Marine Resources, Federal University of Rio de Janeiro State - UNIRIO, Rio de Janeiro

Reports of massive blooms of cyanobacteria now represent a common phenomenon across freshwater and brackish environments. Current knowledge indicates low and uneven efforts on documenting monetary impacts of cyanobacteria at a global scale, although blooms impacts include loss of ecosystem functionality, poisonings with documented lethality to humans, and a multitude of costs related to social well-fare and non-material values. In spite of that, blooms have been rarely investigated for their technological and industrial potentialities with few exceptions e.g., nordic countries which are more prone to explore values of cyanobacterial scums for e.g., bioenergy production and biofertilizers. Among bloom-forming cyanobacteria, the potentially toxic and invasive Raphidiopsis raciborskii represents a socioeconomic and environmental threat in tropical and sub-tropical areas e.g., Australia and Brazil, with projected increasing impact in Europe and remote or indigenous areas. Here, we present a first attempt to assess the potentialities of using R. raciborsikii blooms as a sustainable solution in a semi-arid region of Brazil. We used literature data from 10 freshwater reservoirs in Pernambuco with reported biomass concentrations above the World Health Organization threshold for harmful blooms. Preliminary conservative estimates indicate that harvesting blooms of this cyanobacterium species alone, from those systems could potentially generate up to 1.11×107 m3 of methane and 33 GWh of electricity annually, which could provide electricity for over 21,000 inhabitants. Harvesting could also potentially recover up to ca. 4000 and 245 tons of nitrogen and phosphorus annually. Combining this solution with a myriad of existing management interventions and a comprehensive information on economic burdens caused by blooms may enhance social cohesion around the topic and potentially close the cycle in the water-waste-energy-food nexus.