{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T05:26:19Z","timestamp":1777958779404,"version":"3.51.4"},"reference-count":44,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2020,12,4]],"date-time":"2020-12-04T00:00:00Z","timestamp":1607040000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Currently, satellite ocean color imageries play an important role in monitoring of water properties in various oceanic, coastal, and inland ecosystems. Although there is a long-time and global archive of such valuable data, no study has comprehensively used these data to assess the changes in the Caspian Sea. Hence, this study assessed the variability of bio-optical properties of the upper-water column in the Southern Caspian Sea (SCS) using the archive of the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and the Moderate Resolution Imaging Spectroradiometer (MODIS). The images acquired from SeaWiFS (January 1998 to December 2002) and MODIS Aqua (January 2003 to December 2015) satellites were used to investigate the spatial\u2013temporal variability of bio-optical properties including Chlorophyll-a (Chl-a), attenuation coefficient, and remote sensing reflectance, and environmental parameters such as sea surface temperature (SST), wind stress and the El Nino-southern oscillation (ENSO) phenomena at different time lags in the study area. The trend analysis demonstrated an overall increase of 0.3358 mg m\u22123 in the Chl-a concentration during 1998\u20132015 (annual increase rate of 0.018 mg m\u22123 year\u22121) and four algal blooms and in turn an abnormal increase in Chl-a concentration were occurred in August 2001, September 2005, 2009, and August 2010. The linear model revealed that Chl-a in the northern and middle part of the study area had been influenced by the attenuation coefficient after a one-month lag time. The analysis revealed a sharp decline in Chl-a concentration during 2011\u20132015 and showed a high correlation with the turbidity and attenuation coefficient in the southern region, while Kd_490nm and remote sensing reflectance did a low one. Generally, Chl-a concentration exhibited a positive correlation with the attenuation coefficient (r = 0.63) and with remote sensing reflectance at the 555 nm (r = 0.111). This study can be used as the basis for predictive modeling to evaluate the changes of water quality and bio-optical indices in the Southern Caspian Sea (SCS).<\/jats:p>","DOI":"10.3390\/rs12233975","type":"journal-article","created":{"date-parts":[[2020,12,4]],"date-time":"2020-12-04T11:59:00Z","timestamp":1607083140000},"page":"3975","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Spatio-Temporal Variability in Bio-Optical Properties of the Southern Caspian Sea: A Historic Analysis of Ocean Color Data"],"prefix":"10.3390","volume":"12","author":[{"given":"Bonyad","family":"Ahmadi","sequence":"first","affiliation":[{"name":"Department of Environment, Faculty of Natural Resources &amp; Marine Sciences (FNRMS), Tarbiat Modares University (TMU), Noor 46414 356, Mazandaran, Iran"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9172-9507","authenticated-orcid":false,"given":"Mehdi","family":"Gholamalifard","sequence":"additional","affiliation":[{"name":"Department of Environment, Faculty of Natural Resources &amp; Marine Sciences (FNRMS), Tarbiat Modares University (TMU), Noor 46414 356, Mazandaran, Iran"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tiit","family":"Kutser","sequence":"additional","affiliation":[{"name":"Estonian Marine Institute, University of Tartu, M\u00e4ealuse 14, 12618 Tallinn, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9038-5914","authenticated-orcid":false,"given":"Stefano","family":"Vignudelli","sequence":"additional","affiliation":[{"name":"CNR Institute of Biophysics (CNR-IBF), Via Moruzzi 1, 56024 Pisa, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7441-5055","authenticated-orcid":false,"given":"Andrey","family":"Kostianoy","sequence":"additional","affiliation":[{"name":"P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, 36, Nakhimovsky Pr., 117997 Moscow, Russia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,4]]},"reference":[{"key":"ref_1","unstructured":"Mamedov, R., and Khoshravan, H. (2015). The Atlas of Caspian Sea Hydromorphology, Sophia Publishing Group."},{"key":"ref_2","unstructured":"(2005). The Caspian Sea Environment, Springer Science and Business Media LLC."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"24937","DOI":"10.1029\/98JC02160","article-title":"Ocean color chlorophyll algorithms for SeaWiFS","volume":"103","author":"Maritorena","year":"1998","journal-title":"J. Geophys. Res. 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