DNA barcoding reveals the temporal variation of ichthyoplankton assemblages and their relationship with environmental variables in a tropical mangrove estuary.

Seasonal ichthyoplankton dynamics and their relationship with environmental parameters were studied in the Karanja mangrove estuary from January 2022 to March 2023 to determine ichthyoplankton biodiversity. Twenty-four ichthyoplankton species from 16 families and 3 orders were identified using morphological characteristics and DNA barcoding methods. The most dominant family was Mugilidae, contributing 20% of the total ichthyoplankton assemblage, followed by Engraulidae (12%). The maximum abundance of ichthyoplankton was recorded during the monsoon seasons, indicating that Karanja estuary can be a spawning ground for Mugil cephalus, Osteomugil perusii, Stolephorus insularis, Thryssa hamiltonii, Escualosa thoracata, Terapon jarbua, and Dendrophysa russelii. Redundancy analysis (RDA) and biotic-environmental (BIO-ENV) analysis revealed that water temperature, salinity, dissolved oxygen, nitrate, and transparency were the prevailing environmental factors affecting seasonal variation of ichthyoplankton in the estuary. The Shannon-Wiener index (index = 2.54), Margalef index (index = 2.60), and Pielou's index (index = 0.95) indicate diverse ichthyoplankton dynamics in the estuary. This is the first report of ichthyoplankton biodiversity from the Karanja estuary using integrated taxonomy, with the first-time documentation of Tridentiger barbatus and Scombrops sp. in the region. These findings provide valuable insights into the intricate interactions between environmental factors, food plankton, and ichthyoplankton assemblages, which will be crucial for biodiversity inventories, effective management, and sustainability of resources.