Drivers of Ecosystem Metabolism in Two Managed Shallow Lakes with Different Salinity and Trophic Conditions: The Sauce Grande and La Salada Lakes (Argentina)

Abstract

Understanding the drivers and how they affect ecosystem metabolism is essential for developing effective management policy and plans. In this study, net ecosystem production (NEP), ecosystem respiration (R), and gross primary production (GPP) rates were estimated in relation to physicochemical, hydrological, and meteorological variables in La Salada (LS) and Sauce Grande (SG), two shallow lakes located in an important agricultural region with water management. LS is a mesosaline, mesotrophic-eutrophic lake, whereas SG is a hyposaline and eutrophic lake. GPP and R showed daily and seasonal variations, with R exceeding GPP during most of the study period in both lakes. Net heterotrophic conditions prevailed during the study period (NEP LS: −1.1 mmol O2 m−2 day−1 and NEP SG: −1.25 mmol O2 m−2 day−1). From data analysis, the temperature, wind speed, and lake volume are the main drivers of ecosystem metabolism for both lakes. Despite the significant differences between the two lakes, the NEP values were similar. The different hydrological characteristics (endorheic vs. flushing lake) were crucial in explaining why the two different systems presented similar ecosystem metabolic rates, emphasizing the importance of water management.

A new method to estimate planktonic oxygen metabolism using high‐frequency sensor measurements in mesocosm experiments and considering daytime and nighttime respirations

“…This is because, even if the daylength varies, the production period is still comparable across seasons (Supporting Information Table S3). This characteristic of the production period may be explained by the fact that metabolic processes are controlled by various mechanisms, such as temperature variations, throughout the seasons and not only by the daylength and the amount of light received (Solomon et al 2013; Alfonso et al 2018; Lopez Sandoval et al 2019). As a result, during long days, the actual production period is considerably shorter than the daylength, and hence Rdaytime integrated over the production period is in fact integrated over a significantly shorter period than that integrated from sunrise to sunset.…”

Shoring up the foundations of production to respiration ratios in lakes

“…We believe that aquatic metabolism studies are on a positive trajectory, providing methodological and conceptual guidance for future research. P:R ratios can provide valuable information for lake managers, highlighting the effects of changing hydrological inputs on lake metabolism (Idrizaj et al 2016;Alfonso et al 2018). Temporal trends in measured P:R ratios may signal browning events such as those caused by storms and high runoff (Sadro and Melack 2012).…”

“…Although macrophytes can make substantial contributions in some lakes, benthic and planktonic algae usually dominate GPP (Wetzel 2001) and bacterial and algal respiration dominates R (Wetzel 2001; Andersson and Kumblad 2006; Dodds and Cole 2007; Brothers et al 2013 a ). These broad terms, when applied to entire lakes, are widely used to infer whether phytoplankton or bacteria dominate material flows at the base of the food web (Cole et al 2000; Staehr et al 2012 a ; Alfonso et al 2018).…”

Vulnerabilidad eco-ambiental y estrategias de manejo sustentable del territorio: el caso de la cuenca del río Sauce Grande (Argentina)

“…Existe evidencia científica que la escorrentía superficial generó el transporte de nitrógeno y fósforo hacia el dique Paso de las Piedras (ubicado en la cuenca media), produciéndose un acelerado proceso de eutrofización durante los períodos de elevadas precipitaciones (primaveraverano) entre los años 2008 y 2009 (Espósito et al, 2016). Por otra parte, en la laguna Sauce Grande (Figura 1) esto se observó durante los años 2016 y 2017 (Alfonso et al, 2018).…”