“…SAS in seawater are mainly formed by biological activities, especially by phytoplankton production (Ciglenečki et al, 2018Ćosović et al, 2000;Žutić et al, 1981), bacteria (Kurata et al, 2016), and feeding of zooplankton (Croot et al, 2007;Kujawinski et al, 2002). SAS belong to the group of biosurfactants and represent the most reactive fraction of DOC with amphiphilic character, whereby they adsorbed at various natural phase boundaries such as the sea surface microlayer (Ćosović & Vojvodić, 1987;Karavoltsos et al, 2015;Plavšić et al, 2007;Sabbaghzadeh et al, 2017;Wurl et al, 2011), the halocline in stratified estuaries (Ćosović & Vojvodić, 1989;Žutić & Legović, 1988), the chemocline of a marine lake (Ciglenečki et al, 2017;Marguš et al, 2015;Simonoviće et al, 2023), and in seawater eddies (Ciglenečki et al, 2021).…”