Seawater silicate fertilizer facilitated nitrogen removal via diatom proliferation

Abstract Dissolved inorganic nitrogen (DIN) enrichment accompanied by silicate deficiency in seawater can promote dinoflagellate growth over diatom growth and induce further negative ecological consequences. Here, we propose an easily exercisable method for silicate fertilization as a remedy of eutrophication. In the laboratory, rice husk ash (RHA) released silicate and phosphate in an atomic ratio range of 38–113 without a significant influence on DIN. During incubations of silicate-limited waters, low-dose fertilization increased the diatom/dinoflagellate ratio by 1–5 times. With the high-dose fertilizer addition, DIN, with an initial concentration of 7.63 ± 0.95 μmol l−1, was exhausted in three days, and the diatom abundance increased by 19 times on the 5th day. The silicate fertilization method presented here can be applied independently in eutrophicated waters for dinoflagellate suppression and dissolved nitrogen removal; this method could also work as a supplementary measure to existing nutrient (N, P) reduction and biomanipulation efforts.