In an exciting scientific breakthrough, a group of researchers from the Indian National Centre for Ocean Information Services (INCOIS) have developed a technique to measure the volume of chlorophyll-a—a critical indicator of phytoplankton concentration—in the Bay of Bengal in real-time. Phytoplanktons, tiny microscopic aquatic plants, play a pivotal role in controlling the overall health of the ocean ecosystem.
The importance of these minuscule plants cannot be overstated: they contribute over half of the oxygen content in our atmosphere, help mitigate global warming by absorbing human-produced carbon dioxide, form the base of marine food chains, and are essential bioindicators in oceanic life regulation.
Nitty-Gritty of the Study
Over the span of 16 years, from January 2003 to December 2018, the scientists closely monitored the trends in chlorophyll-a levels in the northwestern Bay of Bengal. This study was largely based on both in-situ data and satellite data procured from various sources, including NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer), NASA’s VIIRS (Visible Infrared Imaging Radiometer Suite) sensor, and ISRO’s OCM-2 (Ocean Colour Monitor-2).
Unraveling the Findings
The scientists noted two significant peaks in the levels of chlorophyll-a. The first, or the primary peak, was observed during the pre-southwest monsoon period due to recurrent phytoplankton blooms in coastal waters. In contrast, the secondary peak appeared towards the end of the southwest monsoon, spreading to significantly offshore areas.
Several factors were found to influence these peaks. The increase in phytoplankton numbers was certainly one influencing factor. However, physical forces such as upwelling, wind-induced vertical mixing, convective overturn, and various chemical inputs—including river runoff—were also noted to play a role.
Implications of the Study: Increased Nutrients and Eutrophication
The findings suggest a significant spatial variability in the study area during the pre-southwest monsoon tied to salinity and nutrients—a major driver for the abundance and distribution of phytoplankton. However, this increase in nutrients could potentially be a double-edged sword.
On one hand, an increase in nutrients might denote an overall improvement in the health status of the ecosystem. On the other hand, excessive phytoplanktons can also harm oceanic health due to a process known as eutrophication, where an over-enrichment of nutrients leads to the excessive growth of algae or algal blooms. This, in turn, depletes oxygen levels in the water body, adversely affecting other aquatic lifeforms.
Understanding Chlorophyll
Chlorophyll is the primary pigment harnessed by plants for photosynthesis—the process of converting light energy into chemical energy through the synthesis of organic compounds. Its name is derived from the Greek words ‘chloros,’ meaning green, and ‘phyllon,’ meaning leaf. There are four types of chlorophyll: Chlorophyll-a, found in all higher plants, algae, and cyanobacteria; Chlorophyll-b and -c, found in higher plants, green algae, diatoms, dinoflagellates, and brown algae respectively; and Chlorophyll-d, found exclusively in red algae.
Looking Ahead: The Importance of Continued Monitoring
The information gleaned about marine environmental parameters like these is becoming increasingly crucial as they serve as barometers for monitoring climate change, river discharge, and the impacts of pollution in oceans. Given that phytoplankton health is greatly dependent on light, temperature, and nutrients, continuous monitoring of the ocean ecosystem is critical. This will enable us to develop effective mitigation systems to combat disruptions caused by algal blooms resulting from excessive phytoplankton enrichment in coastal waters.
