Gammarus Spp. in Aquatic Ecotoxicology and Water Quality Assessment: Toward Integrated Multilevel Tests
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Gammarus spp. in Aquatic Ecotoxicology and Water Quality Assessment: Toward Integrated Multilevel Tests Petra Y. Kunz, Cornelia Kienle, and Almut Gerhardt Contents 1 Introduction ................................. 2 2 Culturing of Gammarids ............................ 5 3 Gammarids in Lethality Testing ......................... 7 3.1 Pesticides, Metals, and Surfactants ..................... 7 3.2 Extracted, Fractionated Sediments ..................... 8 3.3 Coastal Sediment Toxicity ......................... 8 4 Feeding Activity ............................... 10 4.1 Time–Response Feeding Assays ...................... 10 4.2 Food Choice Experiments ......................... 16 4.3 Leaf-Mass Feeding Assays Linked to Food Consumption ........... 17 4.4 Modeling of Feeding Activity and Rate ................... 19 4.5 Post-exposure Feeding Depression Assay .................. 20 4.6 Effects of Parasites on Gammarid Feeding Ecology ............. 21 5Behavior................................... 22 5.1 Antipredator Behavior .......................... 22 5.2 Multispecies Freshwater BiomonitorR (MFB) ................ 27 5.3 A Sublethal Pollution Bioassay with Pleopod Beat Frequency and Swimming Endurance ........................... 29 5.4 Behavior in Combination with Other Endpoints ............... 29 6 Mode-of-Action Studies and Biomarkers .................... 31 6.1 Bioenergetic Responses, Excretion Rate and Respiration Rate ......... 32 6.2 Population Experiments, and Development and Reproduction Modeling .... 41 6.3 Endpoints and Biomarkers for Endocrine Disruption in Gammarids ...... 44 6.4 Other Specific Biomarkers for Detecting Multiple Stressors in Gammarids ... 48 7 Exposure Types ................................ 53 7.1 Pulsed Exposure Assays and Models .................... 53 P.Y. Kunz (B) Ecotox Centre, Swiss Center for Applied Ecotoxicology, Eawag/EPFL, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland e-mail: [email protected] D.M. Whitacre (ed.), Reviews of Environmental Contamination and Toxicology, 1 Reviews of Environmental Contamination and Toxicology 205, DOI 10.1007/978-1-4419-5623-1_1, C Springer Science+Business Media, LLC 2010 2 P.Y. Kunz et al. 7.2 Sediment Toxicity Assays ......................... 57 7.3 In Situ Tests ............................... 58 8 Discussion .................................. 62 8.1 Evaluation of Existing Methods ...................... 62 8.2 Perspectives on a Multimetric Gammarus spp. Test System .......... 64 9 Summary ................................... 65 References ................................... 66 1 Introduction More than 4500 species belong to the crustacean sub-order Gammaridea (order Amphipoda) (Bousfield 1973). Among Amphipods, the Gammaridea are the most widespread group and are found throughout a range of marine, freshwater, and ter- restrial habitats (Bousfield 1973; Lincoln 1979), whereas the three other amphipod sub-orders (Hyperiidea, Ingolfiellidea, and Caprellidea) are highly specialized and ecologically restricted. Gammarus is the amphipod genus with the highest num- ber of epigean freshwater species, comprising over 100 species that are distributed throughout the Northern Hemisphere (Karaman and Pinkster 1977). Abiotic fac- tors such as temperature, salinity, oxygen, acidity, and pollution play an important role in the distribution of Gammarus species (Whitehurst and Lindsey 1990) and members of this species are often found in great abundance under rocks, in gravel, or in coarse substrates and among living and dead vegetation (Fitter and Manuel 1994). These substrata provide both shelter from predators and a supply of organic detritus and other foodstuffs, with the result that in many riverine communities, amphipod species such as Gammarus pulex (Linnaeus) may represent the dominant macroinvertebrate in terms of biomass (Macneil et al. 1997; Shaw 1979). The species G. fossarum and G. pulex, for example, are widespread and function- ally important in streams throughout much of Europe and Northern Asia (Karaman and Pinkster 1977). They display a wide trophic repertoire, feeding as herbivores, detritivores, and predators. Stream-conditioned leaves, biofilms that grow on them, dead chironomids, live juvenile isopods, and even juvenile and wounded/trapped fish are part of their diet (Fielding et al. 2003; Macneil et al. 1997). Intraguild pre- dation and cannibalism have been observed in many amphipod species, and data from G. pulex suggest that this is more common than previously realized (Macneil et al. 1997). This “foraging plasticity” is linked to the success of Gammarus spp. as they persist in colonizing and invading disturbance-prone ecosystems (Macneil et al. 1997). Hence, the ecological value of a macroinvertebrate like G. pulex in streams may exceed its important role as a shredder in processing leaf material that falls into streams (Welton et al. 1983; Willoughby and Earnshaw 1982; Willoughby and Sutcliffe 1976), and as prey items for many fish species (Maitland 1966; Smyly 1957; Welton 1979). Gammarus species have a complex life cycle, which is of value in ecotoxico- logical studies because changes in mating behavior can be observed more easily in the presence of xenoestrogen exposure (Segner et al. 2003; Watts et al. 2001, 2002, 2003). Gammarus females are available for mating only during a brief period Gammarus spp. in Aquatic Ecotoxicology and Water Quality Assessment 3 directly after the molt. Alternatively, males are available for mating during most of the molt cycle (Sutcliffe 1993), which results in a male-biased operational sex ratio. To address this situation, males engage in precopulatory mate guarding when encountering a female nearing the molt stage (Ridley 1983). Prior to mating, males grab and hold different females before deciding which one is likely to produce the most eggs. Pairing in Gammarus is positively size assortive and, unlike other arthro- pods, males are larger than females (Dick and Elwood 1996; Thomas et al. 1995; Zielinski 1998). When the male has found a suitable female, they form a precop- ula pair. The male holds the female under and parallel to his body using the first pair of gnathopods (Borowski 1984), and while carrying her, he performs all the necessary swimming movements (Bollache and Cezilly 2004). Pairs can remain in precopula for up to 2 weeks (Hartnoll and Smith 1980). As soon as the female sheds her skin, the male can mate with her. Then, the precopula pair separates and the female carries the developing eggs in her brooding pouch. The young hatch after 1–3 weeks; thereafter, the juveniles remain in the brooding pouch until the next female molt. Then, after 4–6 weeks, the young Gammarus swim out of the brooding pouch. Freshly hatched juveniles feed by coprophagy (feces of adults) (McCahon and Pascoe 1988b). The diet thereafter expands to include conditioned leaves, and after 1 month or so, the young feed only on conditioned leaves. The juveniles will, themselves, mate 3–4 months later, after they have reached sexual maturity and com- pleted about 10 molts (McCahon and Pascoe 1988a). Gammarids can reach ages of 1–2 years. The presence of gammarids in freshwater streams is crucial, because macroin- vertebrate feeding is a major rate-limiting step in the processing of stream detritus (Cummins and Klug 1979). Detritus is an integrated decomposition of leaf material in streams and is brought about by a combination of chemical leaching, microbial decomposition (primarily by aquatic hyphomycetes), macroinvertebrate feeding, and physical abrasion (Webster and Benfield 1986). Environmental contaminants can reduce detritus processing by decreasing the microbial conditioning and/or the abundance or the feeding activity of detritivores such as G. pulex (Forrow and Maltby 2000; Webster and Benfield 1986). Reductions in gammarid abundance from increased mortality have, for example, been observed after exposing them to acutely toxic landfill leachates that contain environmental contaminants (Bloor et al. 2005). Toxicant-induced reductions in feeding rate can result in reduced growth, size, fecundity, and survival of individuals (Anderson and Cummins 1979; Maltby and Naylor 1990), thereby affecting the stream community structure (Sutcliffe and Hildrew 1989). Feeding activity is one of many behavioral responses that may be affected by environmental contaminants. For example, changes in locomotory or ventilation behavior are compensatory, reversible adaptive responses to pollutants that may mitigate potential overt effects (e.g., direct behavioral response after perception of stress). Irreversible effects of a toxicant on a behavioral mechanism or expression are also observed in the behavioral response of an organism, after the toxicoki- netic and toxicodynamic processes have started [e.g., acetylcholinesterase (AChE) inhibition exerted by neurotoxins; Gerhardt 1995]. 4 P.Y. Kunz et al. Using behavioral parameters in ecotoxicology studies have advantages, to wit short response times (i.e., early warning responses), sensitivity (i.e., for neuro- muscular toxins), non-invasiveness, ecological relevance, and the possibility for time-dependent data analysis (Fossi 1998; Gerhardt 2007; Scherer 1992). Changes in behavior may be used as important indicators for ecosystem health, because they rest on biochemical processes, but also reflect the fitness of the individual organ- ism as well as potential effects on the population level, such as altered abundance of the species in the ecosystem. Behavioral responses seem to be of similar sen-