Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum
Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum
Mirco Bundschuh 0 1 2 3 4
● Torsten Hahn 0 1 2 3 4
● Mark O. Gessner 0 1 2 3 4
● Ralf Schulz 0 1 2 3 4
0 Fraunhofer Institute for Toxicology and Experimental Medicine , Nikolai-Fuchs-Strasse 1, 30625 Hannover , Germany
1 Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences , Box 7050, 75007 Uppsala , Sweden
2 Institute for Environmental Sciences, University of Koblenz- Landau , Landau Campus, Fortstrasse 7, 76829 Landau , Germany
3 Department of Ecology, Berlin Institute of Technology (TU Berlin) , Ernst-Reuter-Platz 1, 10587 Berlin , Germany
4 Department of Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) , Alte Fischerhütte 2, 16775 Stechlin , Germany
Pharmaceuticals contribute greatly to human and animal health. Given their specific biological targets, pharmaceuticals pose a significant environmental risk by affecting organisms and ecosystem processes, including leaf-litter decomposition. Although litter decomposition is a central process in forest streams, the consequences of exposure to pharmaceuticals remain poorly known. The present study assessed the impact of antibiotics as an important class of pharmaceuticals on the growth of the leaf-shredding amphipod Gammarus fossarum over 24 days. Exposure scenarios involved an antibiotic mixture (i.e. sulfamethoxazole, trimethoprim, erythromycin-H2O, roxithromycin, clarithromycin) at 0, 2 and 200 µg/L to assess impacts resulting from exposure to both water and food. The antibiotics had no effect on either leaf-associated fungal biomass or bacterial abundance. However, modification of leaf quality (e.g. through shifts in leafassociated microbial communities) may have triggered faster growth of gammarids (assessed in terms of body mass gain) at the low antibiotic concentration relative to the control. At 200 µg/L, however, gammarid growth was not stimulated. This outcome might be due to a modified ability of the gut microflora to assimilate nutrients and carbon. Furthermore, the observed lack of increases in the diameter of the gammarids' peduncles, despite an increase in gammarid mass, suggests antibiotic-induced effects in the moulting cycle. Although the processes responsible for the observed effects have not yet been identified, these results suggest a potential role of food-quality, gammarid gut microflora and alteration in the moulting cycle in mediating impacts of antibiotics on these detritivores and the leaf decomposition process in streams.
Gammarus fossarum ● Food quality ● Leaf- associated microbial community ● Indirect effect ●; Physiological fitness
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Pharmaceuticals contribute greatly to human and animal
health and welfare. As a result, the global production of
pharmaceuticals has rapidly grown over the last four
decades (Bernhardt et al. 2017). However, these chemicals are
often incompletely metabolized within the treated
organisms and are only partly degraded during conventional
wastewater treatment. This results in the release of
significant amounts of pharmaceuticals and their metabolic
products into surface waters, together with a broad range of
other chemicals of industrial and domestic use (Hollender
et al. 2009). After their release into a receiving water body,
this mixture of chemicals (often referred to as
micropollutants, Schwarzenbach et al. 2006) can affect local and
downstream aquatic communities and the ecosystems
processes to which the communities contribute (Englert et al.
2013). Since pharmaceuticals are specifically designed to
exert high biological activity, for instance to treat bacterial
infections, they are also likely to have adverse effects on
microbes in aquatic ecosystems (Gessner and Tlili 2016).
Pharmaceuticals acting as antihistamines and antibiotics
can affect primary production, microbial respiration and
other biological processes (Jonsson et al. 2015;
RosiMarshall et al. 2013; but see Wilson et al. 2004).
Furthermore, the antibiotic ciprofloxacin affects the functional
diversity (i.e., the ability to use different carbon sources) of
leaf-associated microbial communities (Maul et al. 2006),
with potentially negative implications for microbial leaf
decomposition and thus nutrient cycling in streams. In
addition, antibiotics can modify interactions between bacteria
and fungi (i.e. aquatic hyphomycetes) colonising
decomposing leaf material (Bundschuh et al. 2009). These impacts
on leaf-associated microbial communities can propagate to
primary consumers, including leaf-shredding invertebrates
(shredder) such as gammarids (Zubrod et al. 2011).
Leaf-shredding gammarids show distinct feeding
preference when given the choice between leaf material that
has been microbially colonized (i.e. conditioned; sensu
Cummins 1974) in either the absence or presence of
antibiotics (Hahn and Schulz 2007). A leaf-shredding
amphipod, Gammarus fossarum (Amph (...truncated)