Monsoon conditions favour holoplankton growth

Monsoon conditions are associated with increased holoplankton biomass along the Visakhapatnam coast, according to a study conducted by researchers from Andhra University.

The research, titled Seasonal Biomass and Biochemical Composition of Nearshore Holoplankton and Meroplankton off Visakhapatnam, East Coast of India, examines seasonal variations in zooplankton biomass and its nutritional composition.

Researchers I. Sahoo and R. B. Kondamudi from Andhra University's Department of Marine Living Resources analysed samples collected from three coastal locations: Fishing Harbour, Rushikonda and Mangamaripeta.

The findings indicate that holoplankton biomass was highest during the monsoon, followed by the post-monsoon and pre-monsoon seasons.

Rushikonda records highest holoplankton biomass

The study reported a maximum holoplankton biomass of 2.33 grams per cubic metre at Rushikonda. The location also recorded the highest annual mean primary productivity at 0.077 gC/m²/hr and the highest mean holoplankton biomass at 0.623 grams per cubic metre.

Holoplankton are organisms that remain planktonic throughout their lives. Copepods contributed substantially to this group in the study.

Meroplankton follows a different seasonal pattern

Unlike holoplankton, meroplankton biomass was highest during the pre-monsoon season, followed by the post-monsoon and monsoon periods.

The highest reported meroplankton biomass was 0.834 grams per cubic metre at Mangamaripeta. Decapod larvae were among the major contributors to this group.

Meroplankton are organisms that spend only part of their life cycle as plankton before developing into other forms. Their seasonal abundance is influenced by factors including the reproductive cycles of marine organisms.

Importance for the marine food chain

Zooplankton play an important role in marine ecosystems by transferring energy from microscopic phytoplankton to larger marine organisms, including commercially important fish.

The researchers also found that protein was the dominant biochemical component in both holoplankton and meroplankton, followed by lipids and carbohydrates.

The study observed a positive relationship between primary productivity and holoplankton biomass. However, meroplankton did not show the same relationship, suggesting that additional biological and environmental factors influence its seasonal distribution.

Research offers insights into Vizag's coastal ecosystem

Published in the African Journal of Applied Research, the research provides information about seasonal variations in plankton biomass along the Visakhapatnam coastline.

The findings may support further coastal ecosystem monitoring and fisheries management by improving understanding of the organisms that form an important foundation of the marine food web.

The researchers also noted that the study covered only three locations and one year of sampling, meaning that further research would be needed to establish whether the observed patterns apply across a wider coastal area and longer periods.