Algal pigments as biomarkers in the aquatic food web: Phytoplankton divisions and their utilization by benthic invertebrates and fish in Lake Erie, 2003--2005

The chlorophylls and pheopigments primarily represent the condition of algal biomass. Specific carotenoids serve as biomarkers for the major divisions of algae. The ultimate goal is to determine levels of hydrophobic algal pigments in tissues of aquatic organisms, as indicators of diet, bioaccumulation and trophic transformations.;For analysis of algal pigments, reversed-phase high performance liquid chromatography method with PDA/Fl detectors has been established and provided the separation for 25 pigments.;Pigment composition was analyzed for phytoplankton, filamentous algae, sediments, benthic invertebrates and tissues of 12 fish species, collected from the eastern Lake Erie (2003--2005).;Spatial and temporal differences revealed 2004 being significantly cooler than 2005: P≤0.0007, df=3. Relative abundance of algal classes in phytoplankton samples varied significantly. Cryptophytes (alloxanthin) were more abundant in 2004 than in 2005, averaging 28% compared to 9%. Chlorophytes (lutein, chlorophyll b), are less abundant in 2004 vs. 2005: 10% compared to 40%, respectively. Diatoms (fucoxanthin) and cyanobacteria (zeaxanthin) abundance was similar for the two years (P>0.05) with an average of 30% and 24% respectively.;Analyses of sediments revealed large differences between sampling sites: 6m vs. 17m. In general sediments contained significantly more pheopigments than algal samples. The biomass expressed by the concentration of chlorophyll a was higher for 2005. Major carotenoids (fucoxanthin, alloxanthin, lutein, zeaxanthin) correspond to the most prominent pigments in extracts of phytoplankton.;Filamentous algae samples were analyzed both by the HPLC-PDA/Fl and scanning electron microscopy. Evidence for increasing biodegradation was determined from plots of log [caro] vs. log [chl], for phytoplankton (least degraded), filamentous algae (intermediate) and sediments (most degraded).;For oligocheates and chironomids degraded chlorophylls were generally more abundant than chlorophyll a. The predominant carotenoids were: beta-carotene>beta-cryptoxanthin>zeaxanthin and additionally retinyl palmitate accumulated by chironomids.;In fish, the distribution of chlorophylls and carotenoids varied among analyzed tissues. Chlorophylls and pheopigments were abundant in digestive tracts. Lutein, zeaxanthin, alloxanthin were found in fish liver. Retinol and retinyl palmitate were present in fish liver and eyes. Bioaccumulation model across trophic levels was developed, based on log [caro] vs. log [chl] ratio.