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

Abstract

1. Omnivory is widespread in food webs, with an important stabilising effect.The strength of omnivorous trophic interactions may change considerably with changes in the local environment.2. Shallow temporary waters are often characterised by high levels of inorganic turbidity that may directly limit the food uptake of filter-feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto-and zooplankton.3. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short-term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design.4. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity. 5. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community-shaping role in plankton communities of temporary waters through altering trophic relationships. K E Y W O R D Sanostracans, phytoplankton, temporary ponds, trophic webs, zooplankton | 227 LUKIĆ et aL.

Life-history omnivory in the fairy shrimp Branchinecta orientalis (Branchiopoda: Anostraca)

“…In later juvenile stages, Chlamydomonas (i.e., a larger unicellular algae) was ingested at higher rates than the smaller sized algae, with the highest rates across all other food items. The ingestion rates of juvenile B. orientalis on both algae were comparable to adult conspecifics and our results also imply that they maintain their feeding ability on pico-and nano-sized algae throughout their life (Lukić et al, 2018(Lukić et al, , 2020. However, nano-sized planktonic algae are probably their dominant prey items within phytoplankton likely due to mechanical limitations of their filtering apparatus, which could also be the case with other juvenile and adult anostracan species as it has been shown for Artemia (Bemal & Anil, 2019).…”

“…From day 14, juvenile B. orientalis fed on both zooplankton prey types offered, rotifers and copepods, so its diet became increasingly like adult individuals (> 28 days old; Lukić et al, 2018Lukić et al, , 2020.…”

“…The feeding of an omnivore plays an important role in community structure and stability (Neutel et al, 2007 ; Stouffer & Bascompte, 2010 ; Wootton, 2017 ). Feeding habits of omnivorous organisms can vary over time in response to changes in the local environment as found for diverse aquatic systems [e.g., temperature (Boersma et al, 2016 ), productivity (Diehl & Feissel, 2000 , 2001 ), turbidity (Lukić et al, 2020 )]. Moreover, some animals are ontogenetic omnivores, meaning that they change feeding modes and habits with age, especially taxa that undergo metamorphosis, e.g., insects (Bernays, 1998 ), fish (Persson et al, 2000 ), or amphibians (Pimm & Rice, 1987 ).…”

Where the Little Ones Play the Main Role—Picophytoplankton Predominance in the Soda and Hypersaline Lakes of the Carpathian Basin

“…In the case of Daphnia galeata, a threshold of 25 mg/L was found, above which the clearance rate decreased [39]. A similar phenomenon was described during feeding experiments with five cladoceran species [40,41] as well as in the case of a fairy shrimp [42]. A high TSS content also inhibited the filtration of a rotifer Brachionus calyciflorus and growth of the ciliate Strobilidium gyrans [43,44].…”

Comparisons of fatty acid accumulation patterns of two filter feeders, Branchinella kugenumaensis and Daphnia magna in a controlled environment

“…Daphnids and most anostracans are generally known to be non-selective filter feeders (Brendonck 1993;Hessen 1985). Among the anostracans, some Branchinecta species (B. gigas and B. raptor) show carnivorous feeding (Rogers et al 2006) and Branchinecta orientalis appears to shift from herbivorous to carnivorous with increasing inorganic turbidity in feeding experiments and a field study (Lukić et al 2020). Coexisting daphnids and B. kugenumaensis might compete for diet or have different trophic niches in natural ecosystems owing to environmental factors (e.g., turbidity).…”