Structuring forces and β-diversity of benthic diatom metacommunities in soda pans of the Carpathian Basin

Abstract

Small soda lakes represent one of the most vulnerable ecosystem types due to their high hydrological sensitivity to climate change and anthropogenic interventions. Since diatoms are excellent bioindicators, determining the β-diversity and the structuring dynamics of diatom metacommunities can provide valuable information for conservation planning of soda pans. In this study, two diatom metacommunities were surveyed monthly in a one-year period from distinct regions of the Carpathian basin: the Fertő-Hanság National Park (FH) between 2013 and 2014, and the Danube-Tisza Interfluve (DT) between 2014 and 2015. We explored whether β-diversity of diatom assemblages in the two regions is enhanced by species turnover or nestedness (related to richness differences) and investigated the role of deterministic and stochastic processes in shaping β-diversity patterns. Furthermore, we evaluated the contribution of environmental variables, geographic distance and temporal variation to community structure. High β-diversity (> 90%) was revealed for both metacommunities, and was maintained primarily by species turnover. Within the metacommunity of the DT where the natural hydrological cycle of soda pans is not disturbed, diatom communities assembled mainly by the selection force of environment at spatiotemporal scale. In the soda pans located in the habitat reconstruction area of the FH, besides species-sorting, significant temporal variation in community structure appeared due to the water management and periodic water supply. Our results point to the need for a conservation management strategy which maintains the natural hydrological regime of small saline lakes, and therefore their habitat heterogeneity which is of high conservation value.

Realized ecological niche-based occupancy–abundance patterns of benthic diatom traits

“…The possibility of time-dependent dispersal in relatively isolated habitats such as lakes situated in different drainage basins, together with the passive propagation of diatoms leads to an assumption of the negligible effects of metapopulation dynamics on the basis of the conclusions of Heino & Grönroos (2014). In contrast to this, the results arrived at here using the trait-based approach reinforce the conclusions of earlier studies, including those conducted in the same region and focusing on benthic diatom species, in which metacommunity dynamics were recognized in the form of a mass-effect concept (Szabó et al, 2019) and speciessorting (Szabó et al, 2018).…”

Trait‐based diatom functional diversity as an appropriate tool for understanding the effects of environmental changes in soda pans

“…The strong relationship of functional diversity to environmental variables had previously been highlighted by other studies which drew attention to their important role in shaping functional structure (Li et al, ; Teittinen et al, ). This means that in soda pans environment selects, consequently, deterministic processes are characteristic (Szabó et al, ), and environmental filtering causes a functional convergence pattern; species with similar ecological strategies and adaptations (suited traits) coexist (Cornwell & Ackerly, ; Petchey, Evans, Fishburn, & Gaston, ; Weiher & Keddy, ) as is also the case among periphytic algae in a floodplain conservation area (Bichoff, Osório, Ruwer, Dunck, & Rodrigues, ).…”

“…This strong environmental filter causes a low degree of α-diversity in alkaline lakes, not only in the case of benthic communities (Stenger-Kovács, Hajnal, Lengyel, Buczkó, & Padisák, 2016), but also in planktic communities (Nkambo et al, 2015;Vidaković et al, 2019;Vignatti, Paggi, Cabrera, & Echaniz, 2012). However, the degree of β-diversity found in these communities, primarily determined by the environmental variables, is high due to species turnover (Szabó, Lengyel, Padisák, Vass, & Stenger-Kovács, 2018); this is true even in sodic anthropogenic, bomb crater ponds (Vad et al, 2017). The conservation of saline lakes is essential if the loss of biodiversity and the disappearance of these unique habitats are to be limited (Williams, 2002).…”

Environmental changes associated with drying climate are expected to affect functional groups of pro- and microeukaryotes differently in temporary saline waters

“…Even so, saline inland waters have so far received little attention when it comes to the diversity of microbial communities 26 compared to estuaries [27][28][29] and man-made salterns [30][31][32] . Consequently, less is known about temporary saline waters and existing studies are generally limited to specific groups like diatoms [33][34][35] or bacteria 36,37 , based on small spatial scales and a limited number of habitats 26 . Although salinity has been a focal point of studies [38][39][40] , we still have little information about the phylogenetic diversity of microorganisms along salinity gradients in temporary ponds and how community composition or the relative share of multiple functional groups change along these gradients.…”