Potential changes in bacterial metabolism associated with increased water temperature and nutrient inputs in tropical humic lagoons

Abstract

Temperature and nutrient concentrations regulate aquatic bacterial metabolism. However, few studies have focused on the effect of the interaction between these factors on bacterial processes, and none have been performed in tropical aquatic ecosystems. We analyzed the main and interactive effects of changes in water temperature and N and P concentrations on bacterioplankton production (BP), bacterioplankton respiration (BR) and bacterial growth efficiency (BGE) in tropical coastal lagoons. We used a factorial design with three levels of water temperature (25, 30, and 35°C) and four levels of N and/or P additions (Control, N, P, and NP additions) in five tropical humic lagoons. When data for all lagoons were pooled together, a weak interaction was observed between the increase in water temperature and the addition of nutrients. Water temperature alone had the greatest impact on bacterial metabolism by increasing BR, decreasing BP, and decreasing BGE. An increase of 1°C lead to an increase of ~4% in BR, a decrease of ~0.9% in BP, and a decrease of ~4% in BGE. When data were analyzed separately, lagoons responded differently to nutrient additions depending on Dissolved Organic Carbon (DOC) concentration. Lagoons with lowest DOC concentrations showed the strongest responses to nutrient additions: BP increased in response to N, P, and their interaction, BR increased in response to N and the interaction between N and P, and BGE was negatively affected, mainly by the interaction between N and P additions. Lagoons with the highest DOC concentrations showed almost no significant relationship with nutrient additions. Taken together, these results show that different environmental drivers impact bacterial processes at different scales. Changes of bacterial metabolism related to the increase of water temperature are consistent between lagoons, therefore their consequences can be predicted at a regional scale, while the effect of nutrient inputs is specific to different lagoons but seems to be related to the DOC concentration.

Optimal metabolic regulation along resource stoichiometry gradients

“…), but not always (Scofield et al . ), possibly because sufficient organic nutrients may be available to fulfil the microorganism demand.…”

“…Fertilisation often decreases soil respiration rates (Janssens et al 2010), but it is not clear whether this pattern is due to increasing CUE with fertilisation ( Agren et al 2013), or to a reduction in microbial biomass in fertilised treatments (Riggs & Hobbie 2016). Adding inorganic nutrients to aquatic systems generally increases CUE (Manzoni et al 2012), but not always (Scofield et al 2015), possibly because sufficient organic nutrients may be available to fulfil the microorganism demand. A further layer of complexity is added when considering the possible trade-offs between growth rate and C-use efficiency (Lipson 2015).…”

Physical Factors Correlate to Microbial Community Structure and Nitrogen Cycling Gene Abundance in a Nitrate Fed Eutrophic Lagoon

“…The lagoon is intermittently connected to the ocean [such systems have been previously described as Intermittently Closed and Open Lakes and Lagoons or ICOLLs (Roy et al, 2001)], while also receiving inflows from nutrient rich freshwater sources (streams, groundwater) draining a farmed catchment. These factors contribute to large temporal variation in water salinity, nutrient levels, phytoplankton biomass (Schallenberg et al, 2010) and probably also microbial communities (Scofield et al, 2015). Similar lagoon systems act as net sinks of land derived nitrogen (N) and phosphorus (P) (Kjerfve, 1994), but diverse outcomes for deposited N are possible upon eutrophication (Taylor et al, 1996; Howarth and Marino, 2006; Nixon and Fulweiler, 2009; Glibert et al, 2014).…”

Biogeochemical cycling and phyto- and bacterioplankton communities in a large and shallow tropical lagoon (Términos Lagoon, Mexico) under 2009–2010 El Niño Modoki drought conditions

“…Despite their importance, few studies have considered the bacterial communities of tropical inland aquatic ecosystems (Roland et al, 2010) or coastal lagoons (Abreu et al, 1992;Hsieh et al, 2012;MacCord et al, 2013;They et al, 2013) and almost none have dealt with tropical coastal lagoons (Scofield et al, 2015). Among the existing studies, very few have been conducted on bacterial communities and most of them have been based on culture-dependent methods (Lizárraga-Partida et al, 1987.…”