VISAKHAPATNAM: While monsoon conditions favour a higher abundance of holoplankton along the Visakhapatnam coast, meroplankton biomass peaks during the pre-monsoon season, highlighting how seasonal changes influence the marine food web, according to a study by Andhra University researchers.
The study found that holoplankton biomass reached its highest level of 2.33 grams per cubic meter at Rushikonda in September 2022, while meroplankton recorded its peak of 0.834 grams per cubic meter at Mangamaripeta in February 2023.
The contrasting patterns point to the influence of changing environmental conditions and reproductive cycles on different groups of marine organisms.
Titled ‘Seasonal Biomass and Biochemical Composition of Nearshore Holoplankton and Meroplankton off Visakhapatnam, East Coast of India,’ the study was published in the African Journal of Applied Research.
Researchers I Sahoo and R B Kondamudi from the Department of Marine Living Resources, Andhra University, examined plankton samples collected monthly from Fishing Harbour, Rushikonda and Mangamaripeta between June 2022 and May 2023.
Zooplankton form an important link between phytoplankton and larger marine organisms, including commercially important fish. The researchers classified them into holoplankton, which remain planktonic throughout their lives, and meroplankton, which spend only a part of their life cycle in the water column.
The study found that holoplankton biomass was highest during the monsoon, followed by the post-monsoon and pre-monsoon seasons. Meroplankton showed the opposite pattern, recording its highest biomass during the pre-monsoon, followed by the post-monsoon and monsoon seasons.
Copepods contributed substantially to holoplankton biomass, while decapod larvae were among the major contributors to meroplankton.
Primary productivity also showed a positive relationship with holoplankton biomass. Rushikonda recorded the highest annual mean primary productivity of 0.077 gCm-2hr-1 and the highest mean holoplankton biomass of 0.623 grams per cubic meter.
However, meroplankton biomass did not follow the same pattern, indicating the influence of other factors, including the reproductive cycles of marine organisms.
Protein was the dominant biochemical constituent in both holoplankton and meroplankton, followed by lipids and carbohydrates.
