The Effect of Seasonal Variations on the Abundance of Oikopleura dioica in the Northwestern Arabian Gulf

Abstract

This study aimed to assess the impact of physicochemical parameters, serving as indicators of eutrophication, on the abundance of Oikopleura dioica in Kuwait Bay due to urbanization and sewage runoff. Seasonal variations and the abundance of O. dioica, along with physicochemical parameters (temperature, salinity, dissolved oxygen concentration, and nutrient concentrations), and chlorophyll-a concentrations were investigated at three stations—KB1, KB2, and KB3—separated by approximately 18–20 km in the eutrophic seawater of Kuwait Bay. The abundance of O. dioica measured 35.3 ± 28.60 × 103, 48.2 ± 45.11 × 103, and 43.4 ± 15.46 × 103 ind m−3 in KB1, KB2, and KB3, respectively. Statistical analysis showed no significant variation in O. dioica abundance among the three stations (F = 0.123; d.f = 11, p > 0.05). Moreover, the abundance of O. dioica exhibited positive correlations with salinity, chlorophyll-a, and nitrates (r = 0.9; p > 0.05), while being negatively affected by dissolved oxygen concentration (r = − 0.64; p > 0.05). During summer, O. dioica showed the highest abundance at each station, with a peak of 125 × 103 ind.m−3 in KB2. Principal Component Analysis (PCA) revealed a strong association between O. dioica density, chlorophyll-a, and salinity during summer, suggesting that adequate food quality and quantity may contribute to the growth and reproduction of O. dioica in Kuwait Bay.