Evaluation of the Gammarus pulex in situ feeding assay as a biomonitor of water quality: Robustness, responsiveness, and relevance

Abstract

Biomonitoring using benthic macroinvertebrates has been used to assess water quality in Europe since the early 20th century. Most methods use community-level measurements, and the use of single-species responses has been limited, despite their potential benefits as sensitive, early warning indicators. Here we evaluate a single-species in situ assay in which the response is feeding inhibition of the freshwater amphipod Gammarus pulex. The assay was deployed in uncontaminated reference sites to quantify background variability in feeding rates and to elucidate sources of this variation. The ability of the assay to detect impacts of point-source discharges was assessed and the ecological relevance of the assay determined by comparing assay responses to aspects of community structure and functioning. Water temperature accounted for 76% of the variation in the feeding rate of animals deployed at uncontaminated sites, and summer deployments had a >90% power to detect a 30% inhibition in feeding. Inhibition of the situ feeding rate of G. pulex deployed downstream of a variety of point-source discharges ranged from 27 to 99.6%. Gammarus pulex is an important detritivore in stream communities, and a strong positive correlation existed between in situ feeding rate measured over 6 d and leaf decomposition measured over 28 d. A positive correlation also existed between in situ feeding and macroinvertebrate diversity and a biotic index. The G. pulex in situ feeding assay is a short-term sublethal biomonitor of water quality that is indicative of community- and ecosystem-level responses occurring over longer time periods. It is robust, responsive, and relevant.

Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum

“…Water was renewed and food replaced every 6 days. Any leaf material remaining at these times was removed, dried and weighed as described above to determine leaf consumption by the gammarids (see Maltby et al 2002; Zubrod et al 2010). …”

“…The leaf mass consumed per day and per mg dry mass of surviving G. fossarum (C) was individually calculated for each replicate and week (Maltby et al 2002) and then averaged over the study duration:where L a  = dry mass of the leaf discs after conditioning but before providing them as food to gammarids, L b  = dry mass of the conditioned leaf discs after 6 days of consumption by G. fossarum , g  = dry mass of the gammarid at the end of the experiment, t  = feeding time in days and k  = is a correction factor for microbial and physical leaf mass loss determined by the following formula:where L c  = dry mass of conditioned leaf discs placed in cages without gammarids, L d  = dry mass of the same leaf discs but after 6 days of exposure, and n  = number of replicates used per week. Moreover, the changes in the peduncle diameter, the fresh and dry mass of each gammarids over the 24-day study period were calculated and served as an indicator of growth.…”

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

“…Finally, gammarids are also relevant test species because of their relatively short, temperature-dependent, reproductive cycle [27], with several broods per year [28]. Thus, the whole ecological and physiological features of gammarids enable investigations on early changes during energy acquisition as well as long-term effects on their reproductive success [24, 29]. The interest of digestive enzymes as potential biomarkers in G .…”

Active <i>in Situ</i> Biomonitoring of Pesticide Pulses Using <i>Gammarus</i> spp. in Small Tributaries of Lake Constance

“…Our test protocol differs from the other approaches using large leaf packages together with higher numbers of gammarids in bags made of nylon nets. These tests have originally been used to study leaf decay and/or colonization with invertebrates but not for specific in situ ecotoxicological experiments with gammarids [7]. There is a higher probability that small invertebrates enter leaf packages in nylon mesh bags compared to our plexiglass tubes.…”

“…Bloor & Banks assessed landfill leachates with in situ tests using mixed species assemblages of Asellus aquaticus and Gammarus pulex [6]. Maltby et al studied effects of waste water treatment plants on gammarids in situ [7]. All papers conclude Gammarus spp.…”