The keystone role of anostracans and copepods in European soda pans during the spring migration of waterbirds

Abstract

Summary 1. The European soda pans of the Carpathian Basin provide important stopover sites for several waterbird species. We studied the effect of different invertebrate food types and other characteristics on the habitat choice and distribution of birds on 82 pans (in Hungary, Austria and Serbia) during spring migration. 2. Only three environmental variables proved to be significant determinants of the waterbird communities: pan density (spatial effect) along with the density of Arctodiaptomus spp. and anostracans (local effect). Variance partitioning of the data revealed that aquatic invertebrate food supply (Arctodiaptomus and anostracans) had a greater effect than pan density on the 10 investigated bird species, suggesting a dominant role of species sorting in structuring the communities. Pied avocets (Recurvirostra avosetta) and northern shovelers (Anas clypeata) differed from the other species in their strong association with densities of anostracans (avocet) and Arctodiaptomus (shoveler). 3. Anostracans and microcrustaceans, especially the most frequent Branchinecta orientalis, Arctodiaptomus spinosus and Arctodiaptomus bacillifer, can be regarded as keystone elements of this soda pan habitat because of their bottom‐up role in structuring waterbird assemblages during spring migration.

Morphometric characteristics and COI haplotype diversity of Arctodiaptomus spinosus (Copedoda) populations in soda pans in Hungary

“…Arctodiaptomus spinosus represents an important food source for aquatic bird species in the Kiskunság soda pans [2,3] and this abundant species has a prominent role in the food web, providing a bottom-up effect and structuring aquatic bird assemblages in spring [17]. The colour of Arctodiaptomus spinosus is bright red due to carotenoids (G.-Tóth L. unpublished data) in the studied soda pans.…”

Waterbird-Mediated Productivity of Two Soda Pans in the Carpathian Basin in Central Europe

“…The two pans are located 3 km apart. The pans are situated in the groundwater discharge areas of a closed hydrographic (endorheic) basin, in which groundwater inflow exceeds the surface-related watershed inflow and precipitation (Boros et al 2013). We assume that nutrient input by precipitation, surface and groundwater inflow were the same in both pans.…”

“…Zavarzin (1993) observed that endorheic soda lakes have closed nutrient cycling, where the input of carbon and nitrogen into the ecosystem comes predominantly from CO 2 and N 2 fixation by photosynthetic cyanobacteria. On other hand, the soda lakes are not entirely closed systems because of sometimes vast populations of waterbirds (Brian et al 1998;Sorokin et al 2014).The soda pans of the Carpathian Basin are important breeding and stopover sites for AfricanEurasian migratory waterbirds traversing the Black Sea and the Mediterranean flyway (Boros et al 2013). The aquatic communities of these habitats are strongly linked to waterbirds in three ways: 1) soda pans with high zooplankton biomass attract planktivorous filter-feeding waterbirds (Boros et al 2006a;Horváth et al 2013); 2) wading shorebirds feed on less abundant nektonic and benthic invertebrates (Boros et al 2006b(Boros et al , 2008b; and 3) large-bodied herbivorous bird species (e.g., geese) provide a significantly high external nutrient load of carbon (C), nitrogen (N), and phosphorus (P), which causes hypertrophic conditions (Boros et al 2008a) and may lead to net heterotrophy (Vörös et al 2008).…”

Vanishing world: alkaline, saline lakes in Central Europe and their diatom assemblages

“…The high nutrient availability of these lakes is not necessarily the consequence of anthropogenic pollution; however, most are surrounded by agricultural areas and tilled down to their shorelines. Even so, because of the tens of thousands of birds that populate these lakes during migration (Harper et al 2003, Boros et al 2006, Horváth et al 2013c) and the active maintenance of endemic beef cattle (Bos primigenius) and buffalo (Bubalus bubalis) farms in the regions, mammal and bird populations substantially increase plant nutrient levels through their droppings (Oduor and Schagerl 2007). The average TP concentration is 8 times higher (1989 µg L ) exceed twice that of freshwater concentrations (based on the database of the University of Pannonia, unpublished data).…”