Differences in bacterial community-level physiological profiles between deep and shallow north-patagonian Andean lakes

Abstract

The utilization of carbon substrates by bacteria results in a process of great ecological significance for aquatic ecosystems. Bacteria are capable of consuming a wide range of organic molecules, but despite the highly diverse functional abilities, environmental availabilities can influence the composition of the community. Thus, differences in dissolved organic matter (DOM) and nutrient bulk between shallow and deep lakes would affect bacterial metabolic capacities. Here, we used the metabolic profiles obtained with Biolog EcoPlates® as a proxy of bacterial processing of DOM, and compared the bacterial community-level physiological profile (CLPP) from 20 North-Andean Patagonian lakes, including shallow (piedmont and high altitude, Z max < 15 m) and deep piedmont lakes. In addition, we carried out an incubation experiment of bacterial communities from one shallow lake to assess the response of the CLPP enriched with algal exudates or leaf leachates. Our results show that the lakes have contrasting limnological features relatable to the obtained CLPP. Shallow lakes have higher nutrient and dissolved organic carbon concentrations than deep lakes and high-altitude shallow lakes. Accordingly, bacterial CLPP differed between piedmont shallow lakes and deep lakes, with a higher ability of using carboxylic acids in deep lakes. The incubation experiment shows that bacteria can develop different metabolic capacities depending on the DOM (leachates versus algal exudates) offered during incubation, increasing the consumption of the carbohydrate D-cellobiose in the algal exudate treatment. Our results show that resource availability (concentration and origin) is an important metabolic-capacity driver of bacterial communities.