Fotosintezna barvila so se izkazala kot dobri kazalci abundance, sestave in fiziološkega stanja fitoplanktonske biomase v morskem okolju. Z uporabo HPLC-analize barvil smo določili strukturo fitoplanktonske združbe v treh različnih morskih okoljih: na območju ribogojnic, na območju komunalnih podvodnih izpustov in v sluzastih makroagregatih. Na referenčni postaji smo izmerili sezonske spremembe fitoplanktonske združbe s prevlado fukoksantin-vsebujočega fitoplanktona (t.j. diatomej) v zimsko-spomladanskem in jesenskem obdobju. Na območju ribogojnic smo izmerili višje koncentracije razgradnih produktov klorofila a, na lokalno obogatenem območju komunalnih izpustov pa smo opazili le manjše spremembe v taksonomski sestavi in biomasi fitoplanktona. Vpliv sezone je bolj izražen kakor vpliv podvodnih komunalnih izpustov. Z uporabo HPLC-analize barvil smo določili razvoj fitoplanktonske združbe v posameznih razvojnih stadijih sluzastih makroagregatov. V fitoplanktonski združbi sluzastih makroagregatov so prevladovale diatomeje in njihov delež k relativni biomasi je s starostjo agregatov še naraščal. Navedeni primeri kažejo na uporabnost in primernost HPLC-analize barvil v študijah morske ekologije.Photosynthetic pigments have proved to be useful biomarkers of the abundance, composition and physiological status of the phytoplankton biomass in the marine environment. Using HPLC pigment analysis, we determined phytoplankton community structure in three different marine environments: in the area of a fish farm, in the area of sewage outlets, and in the mucilaginous aggregates. At the reference site we observed seasonal changes with prevalence of fucoxanthin-containing phytoplankton (i.e. diatoms) during winter/spring and autumn. In the fish farm area the concentration of chlorophyll a degradation products was higher, whereas in the locally enriched environment of sewage outlets we observed only small changes in taxonomic composition and phytoplankton biomass. The impact of season is more expressed than the impact of sewage discharge. With the use of HPLC pigment analysis we determined the development of phytoplankton community in different stages of mucilage aggregates. Phytoplankton biomass was composed primarily of diatoms, and as the aggregates aged, diatoms increased in the relative biomass. Our examples have proven the usefulness and suitability of HPLC pigment analysis in marine ecology studies