ABSTRACT: Stable isotope ratios (d¹⁵N and d¹³C) of estuarine organisms were measured monthly within 2 field seasons in Seldovia Bay, Alaska, USA, to assess the impact of salmon carcass decomposition on estuarine productivity. A hypothesized indirect link between adult and juvenile salmon, with estuarine harpacticoid copepods acting as an intermediary, was supported by the data. Data show an influence of nutrients derived from salmon carcasses on estuarine macroalgal primary production, as nitrogen stable isotope ratio values of Ulva sp., an estuarine macroalga, were elevated in late summer following the salmon run. The isotope data also indicate that harpacticoids depend on Ulva sp. and possibly its epiphytes. Stomach content data for chum salmon fry (Oncorhynchusketa) show that they depend primarily on harpacticoids. Therefore, there is a nutrient link between adult and juvenile chum salmon in Seldovia Bay. Because harpacticoid production in an estuary is thought to control survival of chum fry, the nutrient link may function as a positive feedback mechanism influencing population fluctuations.

KEY WORDS: Harpacticoid copepod · Salmon · Seagrass · Ulva · Estuary · Food web · Nutrients · Stable isotope

Published in MEPS Vol. 158 (1997) on November 17
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997