Organochlorines in black-crowned night heron (Nycticorax nycticorax) eggs reflect persistent contamination in northeastern US estuaries.

Colonially nesting aquatic birds can indicate site-specific contamination because they are high-level predators and dependent upon local resources during the breeding season. We compared persistent organochlorine concentrations in black-crowned night heron (Nvcticorax nvcticorax) eggs collected in 1992-93 among areas of known contamination (New York Harbor, Boston Harbor, Cape Cod, and Delaware Bay) and a reference site (Nantucket Island) in the northeastern United States (7-16 eggs/site). Total PCBs, p,p'-DDE, oxychlordane, heptachlor epoxide, and trans-nonachlor were detected in most eggs and were significantly higher in New York Harbor compared to all other sites (ANOVA on factor scores from the first principal component, which accounted for 75% of data variance, p < 0.0001). New York also had the highest contamination index (the number of Superfund sites within 20 km of the colony) among the sites. Nantucket, the reference site, had consistently low contamination in eggs, and the lowest contamination index. We conclude that black-crowned night heron eggs are useful indicators of site-specific persistent organochlorine contamination, as indexed by the number of nearby Superfund sites.

Confusing selective feeding with differential digestion in bacterivorous nanoflagellates.

Food selectivity and the mechanisms of food selection were analyzed by video microscopy for three species (Spumella, Ochromonas, Cafeteria) of interception-feeding heterotrophic nanoflagellates. The fate of individual prey particles, either live bacteria and/or inert particles, was recorded during the different stages of the particle-flagellate-interaction, which included capture, ingestion, digestion, and egestion. The experiments revealed species-specific differences and new insights into the underlying mechanisms of particle selection by bacterivorous flagellates. When beads and bacteria were offered simultaneously, both particles were ingested unselectively at similar rates. However, the chrysomonads Spumella and Ochromonas egested the inert beads after a vacuole passage time of only 2-3 min, which resulted in an increasing proportion of bacteria in the food vacuoles. Vacuole passage time for starved flagellates was significantly longer compared to that of exponential-phase flagellates for Spumella and Ochromonas. The bicosoecid Cafeteria stored all ingested particles, beads as well as bacteria, in food vacuoles for more then 30 min. Therefore "selective digestion" is one main mechanism responsible for differential processing of prey particles. This selection mechanism may explain some discrepancies of former experiments using inert particles as bacterial surrogates for measuring bacterivory.