Relevance of autochthonous and allochthonous carbon sources to the copepod Boeckella gracilipes in shallow patagonian lakes

TROCHINE, CAROLINA; DÍAZ VILLANUEVA, VERÓNICA; BASTIDAS NAVARRO, MARCELA; BALSEIRO, ESTEBAN; MODENUTTI, BEATRIZ

Granada

Congreso; ASLO; 2015

Our current knowledge on the importance of terrestrial-derived organic matter in the diet of copepods, which are selective feeders that usually do not consume bacteria directly, is somewhat diverse and complex. We investigated the incorporation of terrestrial carbon of Boeckella gracilipes (Copepoda, Calanoida) in three Patagonian shallow lakes that have distinct dissolved organic matter (DOM) concentrations. We linked their 13C values with parameters such as water color (absorbance 440 nm, abs440), dissolved organic carbon (DOC) concentrations, dissolved inorganic carbon (DIC) concentrations and the ratio Colorabs440:Chlorophyll-a. We also determined the 13C values of seston and the phytoplankton composition. Our results showed that the trend in DOM of the three lakes was related to B. gracilipes 13C values, with increasing allochthonous carbon resulting in lower 13C signals in the zooplankter. Particularly, the 13C signal of B. gracilipes was strongly related to the abundance of the nanoflagellate Chrysochromulina parva. This mixotroph acquires carbon mainly by phototrophy and ingests bacteria to supplement its nutrient uptake. We conclude that phytoplankton, rather than allochthonous carbon, supports the copepod B. gracilipes in shallow Patagonian lakes.