Erratum to: The proliferating brown alga Sargassum polycystum in Tuvalu, South Pacific: assessment of the bloom and applications to local agriculture and sustainable energy

Abstract

Since 2011, the small South Pacific atoll nation of Tuvalu has been affected by algal blooms, the most recent being a large growth of the brown alga Sargassum on the main atoll of Funafuti. The gravity of the situation led to an invitation to the authors from the Tuvalu Government to conduct an initial survey of the problem in November 2013. The bloom was seen to be localized on the lagoon side of the main populated island of Fongafale, distributed in a variably dense belt up to 100 m from the shoreline. A total of 19 species of macroalgae were found in the survey area, the dominant one being the phaeophyceaen alga, Sargassum polycystum C. Agardh, with individual plants reaching up to 2 m in length with a cover ranging between 16 and 23 % of the substratum. For seven transects laid from the southern tip of the island to the end of the populated area, wet biomass ranged between 0.45 and 3.56 kg m−2, with an average of 1.68 kg m−2. There was a correlation noticed between the density of human population on the shore and algal biomass, with the highest biomass figures opposite a school and a hotel. Water quality tests also showed nutrient levels almost twice as high in front of populated areas than in unpopulated areas of the island. The algal belt was seen to be concentrated in water less than 1 m deep, becoming sparser as depth increased. The high amount of Sargassum biomass available makes it a good candidate for use as a fertiliser additive for agricultural practices in Tuvalu. Benefits from seaweed-based fertilisers are numerous, and individual farmers have already reported success with the blooms species on the atoll. Additionally, the Sargassum biomass could be converted into biogas using the process of anaerobic digestion in simple household digesters, to meet the need for renewable energy in lighting and cooking.