Functional Role of Native and Invasive Filter-Feeders, and the Effect of Parasites: Learning from Hypersaline Ecosystems

Abstract

Filter-feeding organisms are often keystone species with a major influence on the dynamics of aquatic ecosystems. Studies of filtering rates in such taxa are therefore vital in order to understand ecosystem functioning and the impact of natural and anthropogenic stressors such as parasites, climate warming and invasive species. Brine shrimps Artemia spp. are the dominant grazers in hypersaline systems and are a good example of such keystone taxa. Hypersaline ecosystems are relatively simplified environments compared with much more complex freshwater and marine ecosystems, making them suitable model systems to address these questions. The aim of this study was to compare feeding rates at different salinities and temperatures between clonal A. parthenogenetica (native to Eurasia and Africa) and the invasive American brine shrimp A. franciscana, which is excluding native Artemia from many localities. We considered how differences observed in laboratory experiments upscale at the ecosystem level across both spatial and temporal scales (as indicated by chlorophyll-a concentration and turbidity). In laboratory experiments, feeding rates increased at higher temperatures and salinities in both Artemia species and sexes, whilst A. franciscana consistently fed at higher rates. A field study of temporal dynamics revealed significantly higher concentrations of chlorophyll-a in sites occupied by A. parthenogenetica, supporting our experimental findings. Artemia parthenogenetica density and biomass were negatively correlated with chlorophyll-a concentration at the spatial scale. We also tested the effect of cestode parasites, which are highly prevalent in native Artemia but much rarer in the invasive species. The cestodes Flamingolepis liguloides and Anomotaenia tringae decreased feeding rates in native Artemia, whilst Confluaria podicipina had no significant effect. Total parasite prevalence was positively correlated with turbidity. Overall, parasites are likely to reduce feeding rates in the field, and their negative impact on host fecundity is likely to exacerbate the difference between grazing rates of native and alien Artemia populations at the ecosystem level. The results of this study provide evidence for the first time that the replacement of native Artemia by A. franciscana may have major consequences for the functioning of hypersaline ecosystems. The strong effect of parasites on feeding rate underlines the importance of taking parasites into account in order to improve our understanding of the functioning of aquatic ecosystems.

Environmental constraint of intraguild predation: Inorganic turbidity modulates omnivory in fairy shrimps

“…filterfeeding on algae) have been shown to be affected by salinity (Sánchez, Paredes, Lebouvier, & Green, 2016) and water quality (Brendonck, 1993), but the effect of inorganic turbidity was so far unknown. Herbivorous feeding (i.e.…”

“…Herbivorous feeding (i.e. filterfeeding on algae) have been shown to be affected by salinity (Sánchez, Paredes, Lebouvier, & Green, 2016) and water quality (Brendonck, 1993), but the effect of inorganic turbidity was so far unknown. For non-selective filter feeders such as cladocerans, high amounts of TSS usually lead to the ingestion of increased amounts of inorganic particles and consequently a reduction in ingested algae (Arruda, Marzolf, & Faulk, 1983;Hart, 1988).…”

Body Condition Peaks at Intermediate Parasite Loads in the Common Bully Gobiomorphus cotidianus

“…It is also likely that parasites showing a neutral or even positive effect on fish body condition within the age class examined in our study would have had severe negative consequences if they had infected the host at an early life stage [8]. Likewise, the ability of infected hosts to face new stressors such as global change may have been altered by the parasites [9], as well as the performance of the host in the ecosystem [54]. …”

Resurrection ecology in Artemia

“…It is the main prey for aquatic birds (Sánchez, Green, & Castellanos, ), the intermediate host for many species of parasites (Georgiev et al., ; Rode, Landes, et al., ; Rode, Lievens, et al., ; Vasileva et al., ), and the main consumer of phytoplankton. Because hypersaline ecosystems are simplified, and because of its central role in these ecosystems, Artemia is particularly suited to study cascading effects (Sánchez, Paredes, Lebouvier, & Green, ). For instance, it is a good system to explore how genetic changes in one species translate into “cascading” effects throughout the community and ecosystem.…”