|Abstract Submission No.
|Title of Abstract
|Distribution of diatoms in the deep Indian Ocean
|Ankur Sharma*, Aparna Mol T A, Pranoy Paul, Damare SR, Jagadish S Patil
|CSIR-National Institute of Oceanography
|SAB-2, NIO Colony, Dona Paula
Panaji, Goa, India
|In the open ocean, diatoms form the dominant phytoplankton group and are abundant both taxonomically and numerically in the sun-lit zone. In comparison to euphotic depth, the information on diatom distribution below photic depth in the deep ocean is limited despite knowing the prevalence of diatom sinkingin deeper waters across the global ocean. In this study, the diatom (>100Ám) distribution in deeper water up to 5000m in the equatorial and southern tropical Indian Ocean was evaluated from the multiple plankton net samples collected during the spring intermonsoonseason (March to May 2021). This study reports for the first time the presence of intact phytoplankton cells (>100 Ám) in all vertical zonation (up to 5000m depth) beyond the photic zone in both the equatorial and southern tropical Indian Ocean. However, the cell abundance decreased in deeper depths. Diatoms are abundant in depths of >500m followed by dinoflagellates. Among the diatoms, the counts of centric diatoms are higher followed by pennates. Community comparison across all depths revealed that only a few specieswere found in the upper as well as deep ocean indicating the prevalence of fast sinking mechanisms. However, their contribution at respective depths differed. For instance, Asterolampra sp. contribution to the total community was ~7% and 45% in the upper anddeeper (2500m-4000m) water, respectively. This study provides a basis to identify the community which can aid in deep ocean biogeochemistry studies.
|Diatoms,centrics, pennates, deep ocean, Indian Ocean
|Date Of Birth