Occurrence of white gelatinous foam on the beaches of Kollam (southwest coast of India) due to the senescent bloom of Phaeocystis globosa

An unusual white gelatinous foam (~2 ft high) was detected on the beaches of Kollam (Mundakkal), Kerala, southwest coast of India. It extended to ~300 m alongshore on 10 June 2019 from 7 am and sustained till around 10 am. CSIR-National Institute of Oceanography, Regional Centre, Kochi conducted a field survey and water sampling in the foam-affected coastal region on 11 June 2019 to identify the scientific cause behind this unusual foam formation. Analytical results of the study showed enhanced inorganic nutrients and dissolved forms of organic matter, carbon and nitrogen. The proliferation of a marine prymnesiophyte, Phaeocystis globosa Scherffel (>320 × 10³ cells l−1) in its diploid flagellate stage was detected in the samples along with a higher abundance of prokaryotes (>1.2 × 10⁶ VLPs ml−1) and viruses (>4 × 10⁷ VLPs ml−1). The study revealed that this foam event in Kollam beach area was merely the biogeochemical manifestation of the senescent bloom of P. globosa. Furthermore, since the foam formation due to blooming of P. globosa is the rarest coastal event in tropical marine waters, the study in the Indian waters (Kollam beach) is highly significant considering its potential impact on the marine ecosystems.