A uniquely resilient organism all but unheard of in the Arabian Sea 20 years ago has been proliferating and spreading at an alarming pace, forming thick, malodorous green swirls and filaments that are visible even from space.
A uniquely resilient organism all but unheard of in the Arabian Sea 20 years ago has been proliferating and spreading at an alarming pace, forming thick, malodorous green swirls and filaments that are visible even from space. This unusual organism is Noctiluca scintillans—a millimeter-size planktonic organism with an extraordinary capacity to survive, thrive and force out diatoms, the photosynthesizing plankton that have traditionally supported the Arabian Sea food web. Noctiluca is not a preferred food for larger organisms, so these large blooms, recurring annually and lasting for several months, are disrupting the base of the region’s marine food chain, threatening fisheries that sustain 150 million people, and possibly exacerbating the rise of criminal piracy in the region.
New research published this week in Nature’s Scientific Reports describes how the continued loss of snow over the Himalayan-Tibetan Plateau region is fueling the expansion of this destructive algal bloom. Led by Joaquim I. Goes from Columbia University’s Lamont-Doherty Earth Observatory, the study uses field data, laboratory experiments, and decades of NASA satellite imagery to link the rise of Noctiluca in the Arabian Sea with melting glaciers and a weakened winter monsoon.
Normally, cold winter monsoon winds blowing from the Himalayas cool the surface of the oceans. These colder waters sink and are replaced with nutrient-rich waters from below. This convective mixing is no different than putting an ice cube into a mug of hot coffee. During this time, phytoplankton, the primary producers of the food chain, thrive in the sunlit, nutrient-rich upper layers, and surrounding countries see a bounty of fish that feed directly or indirectly on the phytoplankton. But with the shrinking of glaciers and snow cover in the Himalayas, the monsoon winds blowing offshore from land are warmer and moister, resulting in diminished convective mixing and decreased fertilization of the upper layers.
Read more at Earth Institute at Columbia University
Image: Noctiluca blooms in the Arabian Sea, as seen from space. (Credit: Norman Kuring/NASA)
