Caspian Sea Ecology Research Center, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Sari, Iran
10.22092/ijfs.2026.136428
Abstract
Sea surface temperature (SST) and chlorophyll-a (Chl-a) are important indicators of climatic variability and phytoplankton biomass. This study investigated temporal trends in SST and Chl-a and their relationship in the southern Caspian Sea at monthly and seasonal scales during 2002–2020. MODIS-Aqua and MODIS-Terra satellite data were used to construct long-term time series following standard image preprocessing, atmospheric correction, and retrieval using Multi‑Channel SST (MCSST) for SST and OC3M for Chl-a. Seasonal trends were assessed using the Mann–Kendall test, while the Pettitt’s test was applied to identify abrupt changes. Linear regression was used to examine the relationship between SST and Chl-a. Chl-a showed a significant increasing trend, with mean concentrations rising from 2.95 mg m⁻³ in 2002 to 4.52 mg m⁻³ in 2020. In contrast, mean SST increased slightly from 15.1°C to 16.1°C, but no significant monotonic trend was detected. The Pettitt’s test identified a significant change point in Chl-a around mid-2006. Regression analysis indicated a moderate positive relationship between SST and Chl-a, with SST explaining 57.5% of the observed variability (R²=0.575, p<0.05). The increasing Chl-a trend despite the absence of a significant SST trend suggests that factors beyond temperature, including nutrient inputs and river discharge, may contribute to phytoplankton variability. Overall, the findings highlight the value of long-term satellite observations for monitoring ecological changes in the southern Caspian Sea ecosystem.
Hajiradkouchak, E. , Nasrollahzadeh Saravi, H. , Fazli, H. , Rahnama, B. and Khoshnamvand, M. (2026). Long-term temporal variability of chlorophyll-a and sea surface temperature in the southern Caspian Sea using MODIS satellite observations (2002–2020). Iranian Journal of Fisheries Sciences, 25(6), 967-981. doi: 10.22092/ijfs.2026.136428
MLA
Hajiradkouchak, E. , , Nasrollahzadeh Saravi, H. , , Fazli, H. , , Rahnama, B. , and Khoshnamvand, M. . "Long-term temporal variability of chlorophyll-a and sea surface temperature in the southern Caspian Sea using MODIS satellite observations (2002–2020)", Iranian Journal of Fisheries Sciences, 25, 6, 2026, 967-981. doi: 10.22092/ijfs.2026.136428
HARVARD
Hajiradkouchak, E., Nasrollahzadeh Saravi, H., Fazli, H., Rahnama, B., Khoshnamvand, M. (2026). 'Long-term temporal variability of chlorophyll-a and sea surface temperature in the southern Caspian Sea using MODIS satellite observations (2002–2020)', Iranian Journal of Fisheries Sciences, 25(6), pp. 967-981. doi: 10.22092/ijfs.2026.136428
CHICAGO
E. Hajiradkouchak , H. Nasrollahzadeh Saravi , H. Fazli , B. Rahnama and M. Khoshnamvand, "Long-term temporal variability of chlorophyll-a and sea surface temperature in the southern Caspian Sea using MODIS satellite observations (2002–2020)," Iranian Journal of Fisheries Sciences, 25 6 (2026): 967-981, doi: 10.22092/ijfs.2026.136428
VANCOUVER
Hajiradkouchak, E., Nasrollahzadeh Saravi, H., Fazli, H., Rahnama, B., Khoshnamvand, M. Long-term temporal variability of chlorophyll-a and sea surface temperature in the southern Caspian Sea using MODIS satellite observations (2002–2020). Iranian Journal of Fisheries Sciences, 2026; 25(6): 967-981. doi: 10.22092/ijfs.2026.136428
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