Opposing patterns of zooplankton diversity and functioning along a natural stress gradient: when the going gets tough, the tough get going

Abstract

Salinity represents a major structuring factor in aquatic habitats which strongly affects species richness. We studied the relationships among species richness, density and phylogenetic diversity of zooplankton communities along a natural salinity gradient in astatic soda pans in the Carpathian Basin (Hungary, Austria and Serbia). Diversity and density showed opposing trends along the salinity gradient. The most saline habitats had communities of one or two species only, with maximum densities well above 1000 ind l−1. Similarity of communities increased with salinity, with most of the highly saline communities being dominated by one highly tolerant calanoid copepod, Arctodiaptomus spinosus, which was at the same time the only soda‐water specialist. Salinity obviously constrained species composition and resulted in communities of low complexity, where few tolerant species ensure high biomass production in the absence of antagonistic interactions. The pattern suggests that environmental stress may result in highly constrained systems which exhibit high rates of functioning due to these key species, in spite of the very limited species pool.

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

“…Our results show that turbidity probably does not affect the predation efficiency of anostracans on the IG prey (zooplankton) considerably, but it rather decreases competition for the shared resource (phytoplankton). Turbidity and productivity are typically correlated in soda pans (this study; Horváth et al, 2014), which suggests the importance of turbidity as a stabilising factor in this part of the food web. As chlorophyll a concentrations significantly increase along the turbidity gradient in soda pans , we can exclude that the reason for the predominantly carnivorous feeding of anostracans was resulting from limited amounts F I G U R E 5 A schematic representation of the changes in the relative strength of interactions in the studied intraguild predation system along the turbidity gradient, with anostracans as intraguild predators, zooplankton as intraguild prey, and phytoplankton as shared prey [Colour figure can be viewed at wileyonlinelibrary.com] of phytoplankton available as food.…”

“…stable isotope analyses, we first checked the effect of turbidity on the δ 15 N values of Arctodiaptomus and Branchinecta in two separate LR models. Total phosphorus concentration and chlorophyll a were not included in the initial model because they both showed strong significant positive correlation with TSS at both time points, which is a general pattern in these habitats (see alsoHorváth et al, 2014). For that, we used a stepwise regression with forward selection implemented with the caret, leaps(Lumley & Miller, 2017) and MASS(Venables & Ripley, 2002) packages.…”

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

“…A. sphaerophora indicated the saline type of lakes in the FH region by exhibiting a positive response to high pH and bicarbonate content (Blinn 1993). Cyclotella meneghiniana (indicator species of the FH region) is a suitable and well-known example of species that are physioecologically adapted to high salinity soda pans must survive, either temporarily or permanently, and adapt to special conditions (Oren 1999) such as high salinity, high turbidity (Secchi-transparency of only a few centimeters; Horváth et al 2013a), high nutrient concentrations, high daily temperature fluctuations , and ephemeral features (Cognetti and Maltagliati 2000). Under these conditions, the motile ecological guild has a competitive advantage over either the low-or the high-profile guilds.…”

“…Several algological studies (mostly of phytoplankton) of these soda pans were published (e.g., Kiss 1976, Padisák 1999, Fehér and Schmidt 2003, Fehér 2010, and some studies addressed the diatom floras, or at least included some records of diatom species (Grunow 1860, 1863, Cholnoky 1929, Uherkovich 1965, 1970, Kiss 1971, 1975, 1978, Schmidt and Fehér 1996. With the recognition of the scientific and conservation values of these alkaline lakes, a number of studies have recently been initiated to understand the hydrogeology (Simon et al 2011), water chemistry (Boros 1999), bacterial communities (Rusznyák et al 2011, Borsodi et al 2013, picoplankton (Somogyi et al 2011a, 2011b, 2012, Kürthy et al 2012, Pálffy et al 2013, zooplankton (Horváth et al 2013a), macroinvertebrates (Horváth et al 2013b), and waterfowl (Boros et al 2008). Information on their benthic diatom communities and their ecology has remained scarce, however.…”

Taxonomical and distribution guide of diatoms in soda pans of Central Europe

“…Permanent water cover is more of an exception than rule. When their basin is more or less fi lled with water, they are saline (conductivity ranges from 3,000 to 60,000 μS cm -1 ) and inorganically very turbid (Secchi transparency extends to only a few centimetres (Horváth et al 2013)). Since they serve as resting places of migratory birds (some species are also nesting), phosphorus load by the waterfowl results in permanently high TP values (Boros et al 2006).…”