The sanitation service of seagrasses – Dependencies and implications for the estimation of avoided costs

Seagrasses are capable of sanitizing coastal seawaters polluted by fecal bacteria. In this work, the reduction of Enterococci concentration in the presence of a seagrasses’ assemblage (Pacific Ocean) was related to the decrease in the probability of gastroenteritis. A linear model fitted to data extracted from the literature showed a 20% reduction of this probability in the presence of these plants. Seagrass sanitation effect was estimated to allow avoiding ca. 24 million gastroenteritis cases/year, globally. Considering a global cost of gastroenteritis of ca. US$ 372 million/year, the global avoided cost, assuming that the sanitation service was always effective, was estimated to be ca. US$ 74 million/year (2020 US$). The seagrass sanitation effect appears genera/geographic dependent, and the targeted pathogen may change as well. Thus, the global estimates were roughly adjusted, obtaining conservative figures of ca. 8 million avoided cases/year and ca. US$ 24 million/year of avoided cost. Considering the importance of this Ecosystem Service (ES) for public health and the potential global spreading of diseases driven by climate change, further research is needed to ascertain the scope of this seagrass ES worldwide.