The abundance of mixotrophic algae drives the carbon isotope composition of the copepod Boeckella gracilipes in shallow Patagonian lakes.

C. TROCHINE,; DÍAZ VILLANUEVA, V.,; BASTIDAS NAVARRO, M.,; E. BALSEIRO,; B. MODENUTTI,

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2015 vol. 37 p. 441 - 451

0142-7873

The importance of allochthonous versus authochthonous carbon to the diet of zooplankters has been discussed at length in the recent literature and more so in lakes with dissolved organic matter (DOM) concentrations between 3.5 to 25 mg L-1. Here, we investigated the sources of carbon of Boeckella gracilipes (Copepoda, Calanoida) in three Patagonian shallow lakes that have different but relatively moderate DOM concentrations (<5 mg L-1). We linked their d13C values with parameters such as water color (absorbance 440 nm, abs440), dissolved organic carbon (DOC) concentrations and the ratio Colorabs440:Chlorophyll-a (Chl-a). We also determined the isotopic composition of seston and the phytoplankton composition. Our results showed a direct relationship between the d13C values of B. gracilipes and seston (r2=0.64 p<0.001) and we demonstrated the importance of phytoplankton to B. gracilipes as its d13C signal was strongly related to the abundance of the nanoflagellate Chrysochromulina parva (r2= 0.86 p<0.001). We further found inverse relationship between DOM and the ratio Colorabs440:Chl-a and B. gracilipes d13C values (r2=0.67 and 0.56, respectively) which also supported the importance of authochthonous carbon to the copepod. We conclude that phytoplankton, particularly mixotrophic algae, rather than allochthonous carbon, supports the copepod B. gracilipes in shallow Patagonian lakes.