Temporal variations in abundance and species richness of phytoplankton with emphasis on diatoms in the subtidal waters of Umm Al-Namil Island, north-western Arabian Gulf of the ROPME Sea Area

Aim: The present study aimed to understand the physico-chemical factors affecting the abundance and species richness of phytoplankton communities, with emphasis on diatoms at the end of the intertidal zone and start of subtidal zone. Methodology: Water quality and phytoplankton community species richness and abundance were measured in the subtidal waters of Umm Al-Namil Island, Kuwait Bay. Kruskal-Wallis statistical approach was used to measure the effect of various environmental parameters on abundance and species richness as well as abundance-species richness relationships using R statistical software. Results: The physico-chemical parameters showed variations at each sampling event as well as within the same season. Total phytoplankton mean abundance values in summer (22.26 ± 0.66 ind. 5l-1) and winter (21.63 ± 0.52 ind. 5l-1) did not significantly vary and the lowest mean abundance was observed during spring (26.36 ± 0.33 ind. 5l-1). Species abundance showed clear pattern with the events, resulting in somehow a negative relationship. Mean species richness was highest during autumn (24.59 ± 1.51), while no significant difference was observed between spring (11.09 ± 0.33), winter (10.47 ± 0.51) and summer (10.11 ± 0.66). The results indicate that phytoplankton species richness and species abundance in Umm Al-Namil Island varied temporally in response to fluctuations in environmental conditions. Interpretation: The end of intertidal zone and beginning of subtidal zone is affluent in diverse forms of phytoplankton species, specifically diatoms since Kuwait Bay is a eutrophic area mainly due to sewage and urbanization. Therefore, a temporal monitoring is required in order to observe any changes in either physico-chemical or biological factors with time and that will help in future conservation and restoration programs. Conservation approaches should be considered seriously since some diatoms like Melosira moniliformis, Gyrosigma diminutum, Fragilaria martyi, Hemidiscus cuneiformis, Planktoniella sol and Amphiprora plicata have been observed only at one event despite abundance and season.