Preliminary Studies on Diversity, Occurrence and Abundance of Phytoplankton in Kalmat Khor, Makran coast Balochistan

Phytoplankton are foundation of marine food webs and are sensitive indicators of environmental variability. Phytoplankton are the primary biomass producer in marine ecosystems, providing ecological sustainability for aquatic life. Through photosynthesis, they produce nearly half of the Earth's organic matter, converting inorganic carbon into living biomass. This study documents the diversity, occurrence, and abundance of phytoplankton in Kalmat Khor, Makran coast, Balochistan, during October 2020–July 2021. Seasonal sampling revealed 92 species under 24 families, dominated by diatoms (Bacillariaceae, Chaetocerotaceae, Coscinodiscaceae, Rhizosoleniaceae) with dinoflagellate peaks of Tripos sp., Protoperidinium sp., Dinophysis sp., during nutrient-enriched monsoon periods. Physico-chemical parameters showed variation with seasonal fluctuations, with higher salinity and transparency in winter and reduced dissolved oxygen and pH during summer. Diversity indices indicated a stable and highly diverse community (Shannon–Wiener H′ = 3.62–3.74; Simpson’s 1–D = 0.94–0.95; Evenness = 0.87–0.89), with slight reductions in evenness during diatom blooms. These findings provide the first comprehensive baseline for Kalmat Khor, contributing to Pakistan’s coastal biodiversity inventories and supporting conservation and management strategies for semi-enclosed lagoons along the Makran coast.