Variation in Fecal Phosphorus Content among Lake Tanganyika Cichlids

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Fish excretion and egestion play a key role in phosphorus (P) cycling in nutrient-poor aquatic ecosystems. In Lake Tanganyika, a diverse assemblage of cichlid fishes includes specialized consumers of almost every resource type available. Given major differences in P content of food resources, we hypothesized that fecal P content would increase with consumer trophic level. We collected fresh fecal samples from 12 common species of fish caught in the field, including algivores and invertivores. Five of six algivores, studied had higher P content in their feces than carnivorous species. Telmatochromis temporalis which feeds on primarily benthic invertebrates had the lowest fecal P content. It is not clear why fecal P content appears to be negatively related to dietary P content. However, our data indicate that P in fish feces is an important component of nutrient cycling in the littoral zone of Lake Tanganyika.


Presented at the Society for Freshwater Science Annual Meeting, Louisville, KY.