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Intra‐lake stable isotope ratio variation in selected fish species and their possible carbon sources in Lake Kyoga (Uganda): implications for aquatic food web studies
Author(s) -
Mbabazi Dismas,
Makanga B.,
OrachMeza F.,
Hecky R. E.,
Balirwa J.S.,
OgutuOhwayo R.,
Verburg P.,
Chapman L.,
Muhumuza E.
Publication year - 2010
Publication title -
african journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.499
H-Index - 54
eISSN - 1365-2028
pISSN - 0141-6707
DOI - 10.1111/j.1365-2028.2009.01163.x
Subject(s) - trophic level , food web , isotopes of carbon , stable isotope ratio , environmental science , phytoplankton , ecology , carbon fibers , trophic state index , δ15n , food chain , environmental chemistry , δ13c , biology , total organic carbon , chemistry , nutrient , physics , materials science , quantum mechanics , composite number , composite material
The stable isotopes of nitrogen ( δ 15 N) and carbon ( δ 13 C) provide powerful tools for quantifying trophic relationships and carbon flow to consumers in food webs; however, the isotopic signatures of organisms vary within a lake. Assessment of carbon and nitrogen isotopic signatures in a suite of plants, invertebrates, and fishes in Lake Kyoga, indicated significant variation between two sites for δ 13 C (paired t = 6.305; df = 14, P < 0.001 and δ 15 N paired t = 1.292; df = 14; P < 0.05). The fish fauna in Bukungu was generally more 13 C enriched (mean δ 13 C = –16.37 ± 1.64‰) than in Iyingo (mean δ 13 C = –20.80 ± 2.41‰) but more δ 15 N depleted (mean δ 15 N = 5.57 ± 0.71‰) than in Iyingo (mean δ 15 N = 6.92 ± 0.83‰). The simultaneous shifts in phytoplankton and consumer signatures confirmed phytoplankton as the major source of carbon for the food chain leading to fish. Limited sampling coverage within lakes may affect lake wide stable isotope signatures, and the same error is transferred into trophic position estimation. Consideration of potential intra‐lake spatial variability in isotope ratios and size is essential in evaluating the spatial and trophic structure of fish assemblages.