Visakhapatnam: Seasonal changes in monsoon conditions and marine organisms’ reproductive cycles influence the distribution and biomass of plankton along the Visakhapatnam coast, with holoplankton peaking during the monsoon and meroplankton recording its highest levels in the pre-monsoon season, according to a study by Andhra University researchers, The New Indian Express reported.
The study found that holoplankton biomass reached a maximum of 2.33 grams per cubic metre at Rushikonda in September 2022. In comparison, meroplankton biomass peaked at 0.834 grams per cubic metre at Mangamaripeta in February 2023.
The research, titled Seasonal Biomass and Biochemical Composition of Nearshore Holoplankton and Meroplankton off Visakhapatnam, East Coast of India, was published in the African Journal of Applied Research.
Researchers I Sahoo and R B Kondamudi from the Department of Marine Living Resources at Andhra University analysed plankton samples collected monthly from Fishing Harbour, Rushikonda and Mangamaripeta between June 2022 and May 2023.
Zooplankton play an important role in the marine food chain by connecting phytoplankton with larger marine organisms, including commercially important fish. The researchers divided them into two groups: holoplankton, which remain planktonic throughout their lives, and meroplankton, which spend only a part of their life cycle in the water column.
The findings showed that holoplankton biomass was highest during the monsoon, followed by the post-monsoon and pre-monsoon seasons. Meroplankton displayed the reverse trend, with the highest biomass during the pre-monsoon, followed by the post-monsoon and monsoon periods.
Copepods and decapod larvae contribute to plankton biomass
Copepods accounted for a substantial share of holoplankton biomass, while decapod larvae were among the major contributors to meroplankton.
The researchers also observed a positive relationship between primary productivity and holoplankton biomass. Rushikonda recorded the highest annual mean primary productivity of 0.077 gCm⁻²hr⁻¹, along with the highest average holoplankton biomass of 0.623 grams per cubic metre.
However, meroplankton biomass did not show a similar relationship with primary productivity, suggesting that factors such as the reproductive cycles of marine organisms also influence its seasonal distribution.
The study further found that protein was the principal biochemical component of both holoplankton and meroplankton, followed by lipids and carbohydrates.
