Unexpected consequences of bombing. Community level response of epiphytic diatoms to environmental stress in a saline bomb crater pond area

Abstract

The spatial response of epiphytic diatom communities to environmental stress was studied in a moderately saline wetland area located in the plain of Danube-Tisza Interfluve, Hungary. The area is characterised by World War II bomb crater ponds and can be regarded as an excellent ecological model system where the dispersion of species is slightly limited by distance. To study the effect of environmental variables on the communities, canonical correspondence analysis was applied. Salinity, pH, total suspended solids, total phosphorous and depth proved to be significant environmental drivers in this analysis. The ecological status of the ponds was assessed with Ziemann’s halobity index, as the trophity-depending metric cannot be applied to these habitats (due to the naturally high phosphorus content). Ponds in “good” ecological status significantly differed from those appertaining to water quality category of “not-good” ecological status considering characteristic of natural astatic soda pans (e.g. salinity, pH, ammonium, total phosphorous concentration, nitrogen:phosphorous ratio and turbidity). The differences between epiphytic diatom communities inhabiting the ponds were detected using non-parametric multidimensional scaling. The samples formed three groups according to the types of ponds (“transparent”, “transitional” and “turbid”) based on the width of the macrophyte belt around them. Indicator species related to the ecological status of the ponds and diatom communities contributing to the separation of groups of ponds were identified. One of the indicator species differed from species already described. Light and scanning electron microscopy features and phylogenetic analyses based on three genes (18S and 28S rRNA genes, rbcL) proved that it was a new species of Nitzschia genus, closely related to Nitzschia frustulum and Nitzschia inconspicua. Therefore, description of a new species, Nitzschia reskoi Ács, Duleba, C.E.Wetzel & Ector is proposed. We concluded that the increasing abundance of Nitzschia reskoi was a signal of the degradation of the intermittent saline wetlands.

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

“…Of the environmental variables, DIN, temperature, pH, conductivity, and DO were the main determinants of the functional diversity metrics as revealed by the RDA analyses. This stands in contrast to the taxonomic diatom assemblages that were chiefly determined by conductivity, bicarbonate, and sulfate concentration (Stenger‐Kovács et al, ) in natural ponds, while, salinity, pH, and turbidity dominated in artificial saline ones (Földi et al, ). All specific functional diversity indices were sensitive to the most important environmental variables of soda pans—conductivity and pH—as has also been found in subarctic ponds (Teittinen et al, ).…”

“…The small cell size and this elongated shape further facilitate their movement among the inorganic sediment particles and their ability to hide in the mud. Small size has also been highlighted in planktic communities (Alfonso, Zunino, & Piccolo, ; Somogyi et al, ) as well as the motile feature (Földi et al, ) in other saline lake ecosystems, where species reduce their cell and pore size due to the osmotic stress (Leterme et al, ).…”

“…As forest shading of streams reduces functional diversity (Taniwaki et al, ), the light climate of soda pans on the basis of their color type (Lengyel et al, ) had a considerable effect on the trait composition and functional diversity, as also experienced in the diatom community composition of artificial bomb crater ponds (Földi et al, ). While the turbidity of lakes reduces light intensity, high levels of humic materials can modify the spectral composition of the incoming light (Kirk, ; V.‐Balogh, Németh, & Vörös, ).…”

Untitled

“…However, these findings, may not be introduced and updated in the OMNIDIA program for a number of years. The OMNIDIA system is used by state institutions in many countries around the world to assess surface water quality (Campeau, Pienitz & Héquette 1999;Rumrich, Lange-Bertalot & Rumrich 2000;Witkowski, Lange-Bertalot & Metzeltin 2000;Gell et al 2005;Potapova & Ponader 2008;Wojtal & Sobczyk 2012;Caballero et al 2013;Żelazna-Wieczorek & Olszyński 2015;Yamamoto, Chiba & Tuji 2017;Lange-Bertalot, Hofmann & Werum 2017;Földi et al 2018;Van de Vijver, Wetzel & Ector 2018). Clearly, if these assessments are based on incomplete or outdated data, assessments of aquatic environments may be fraught with error.…”

“…Nitzschia liebethruthii occurred in environments subjected to periodic drying with a pH close to 7 and high concentration of chloride ions. This species was noted in environments with increased salinity, electrolytic conductivity and high pH value (Rumrich, Lange-Bertalot & Rumrich 2000;Witkowski, Lange-Bertalot & Metzeltin 2000;Lange-Bertalot et al 2017;Földi et al 2018). We propose established new ecological indicator values according to Van Dam et al (1994) assigned to N.liebethruthii: -trophic state: 5 (eutrophic); -moisture aerophily: 4 (aerophilic), and following changes: -pH requirements: 3 (neutrophilic) (changing from 5 to 3); -saprobity: from 2 to 4 (β-mesosaprobe to α-meso-polysabrobe).…”