Effect of water quality and confounding factors on digestive enzyme activities in Gammarus fossarum

Abstract

The feeding activity and subsequent assimilation of the products resulting from food digestion allow organisms to obtain energy for growth, maintenance and reproduction. Among these biological parameters, we studied digestive enzymes (amylase, cellulase and trypsin) in Gammarus fossarum to assess the impact of contaminants on their access to energy resources. However, to enable objective assessment of a toxic effect of decreased water quality on an organisms' digestive capacity, it is necessary to establish reference values based on its natural variability as a function of changing biotic and abiotic factors. To limit the confounding influence of biotic factors, a caging approach with calibrated male organisms from the same population was used. This study applied an in situ deployment at 23 sites of the Rhone basin rivers, complemented by a laboratory experiment assessing the influence of two abiotic factors (temperature and conductivity). The results showed a small effect of conductivity on cellulase activity and a significant effect of temperature on digestive enzyme activity but only at the lowest temperature (7 °C). The experimental conditions allowed us to define an environmental reference value for digestive enzyme activities to select sites where the quality of the water impacted the digestive capacity of the organisms. In addition to the feeding rate, this study showed the relevance of digestive enzymes as biomarkers to be used as an early warning tool to reflect organisms' health and the chemical quality of aquatic ecosystems.

Application of a multidisciplinary and integrative weight-of-evidence approach to a 1-year monitoring survey of the Seine River

“…The enzymatic activity of two carbohydrases (amylase and cellulase) and a protease (trypsin) was determined as previously described by Charron et al (2013) using starch (1 %), carboxymethyl cellulose (2 %), and N-benzoyl-DL-arginine 4-nitroanilide hydrochloride (3 mM) as substrates, respectively.…”

“…For digestive enzyme activity levels, mean reference values were taken from Charron et al (2013). The corresponding thresholds were calculated as described above for AChE activity levels and feeding rates.…”

“…These markers have been studied in our laboratories for several years and are commonly used in laboratory and field experiments (Dedourge- Xuereb et al 2009;Geffard et al 2010;Coulaud et al 2011;Charron et al 2013;Chaumot et al 2015). The substantial insights gained from these numerous studies more particularly allowed us to (1) fully determine the basal level and variation range of each marker; (2) identify and characterize the confounding factors that may modulate biomarker responses, especially under field conditions; and, thus, (3) determine specific reference levels and effect thresholds for these biomarkers adapted to in situ deployment conducted in the context of an environmental survey (ESM Table S4).…”

“…Besides, they are commonly used for the development of exposure biomarkers because they are easily sampled in the field and handled (Besse et al 2013;Dedourge-Geffard et al 2013;Lebrun et al 2014). Moreover, translocated gammarid populations have been fully characterized, and reference levels are (or could be) established for bioaccumulation levels and biomarker responses (Xuereb et al 2009;Geffard et al 2010;Coulaud et al 2011;Besse et al 2013;Charron et al 2013). According to the existence of reference levels or the possibility to derive them for each endpoint, the datasets selected for WOE integration were the following:…”

Consequences of Lower Food Intake on the Digestive Enzymes Activities, the Energy Reserves and the Reproductive Outcome in Gammarus fossarum

“…The interest of digestive enzymes as potential biomarkers in G . fossarum has been underlined in previous studies [26]. Moreover, the optimal conditions for their assay as biomarkers have been defined, including the use of males (to avoid the strong influence of the female reproductive cycle [30]), under an active approach to be able to feed them ad libitum .…”