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TESTING ISOSOURCE: STABLE ISOTOPE ANALYSIS OF A TROPICAL FISHERY WITH DIVERSE ORGANIC MATTER SOURCES
Author(s) -
Benstead Jonathan P.,
March James G.,
Fry Brian,
Ewel Katherine C.,
Pringle Catherine M.
Publication year - 2006
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/05-0721
Subject(s) - mangrove , seagrass , epiphyte , environmental science , ecology , organic matter , plant litter , estuary , isotope analysis , litter , trophic level , range (aeronautics) , δ13c , biology , ecosystem , stable isotope ratio , physics , quantum mechanics , composite material , materials science
We sampled consumers and organic matter sources (mangrove litter, freshwater swamp‐forest litter, seagrasses, seagrass epiphytes, and marine particulate organic matter [MPOM]) from four estuaries on Kosrae, Federated States of Micronesia for stable isotope (δ 13 C and δ 34 S) analysis. Unique mixing solutions cannot be calculated in a dual‐isotope, five‐endmember scenario, so we tested IsoSource, a recently developed statistical procedure that calculates ranges in source contributions (i.e., minimum and maximum possible). Relatively high minimum contributions indicate significant sources, while low maxima indicate otherwise. Litter from the two forest types was isotopically distinguishable but had low average minimum contributions (0–8% for mangrove litter and 0% for swamp‐forest litter among estuaries). Minimum contribution of MPOM was also low, averaging 0–13% among estuaries. Instead, local marine sources dominated contributions to consumers. Minimum contributions of seagrasses averaged 8–47% among estuaries (range 0–88% among species). Minimum contributions of seagrass epiphytes averaged 5–27% among estuaries (range 0–69% among species). IsoSource enabled inclusion of five organic matter sources in our dual‐isotope analysis, ranking trophic importance as follows: seagrasses > seagrass epiphytes > MPOM > mangrove forest > freshwater swamp‐forest. IsoSource is thus a useful step toward understanding which of multiple organic matter sources support food webs; more detailed work is necessary to identify unique solutions.