Az éghajlatváltozás következménye: szikes tavak és algaközösségeinek veszélyeztetettsége

A környezettudatos nevelés egyik formája a terepen, a természetben való ismeretek elsajátítása. A kis szikes tavak és azok mikroszkópikus algavilágának megismerése felejthetetlen élményt nyújt nemcsak a gyermekeknek, de tanáraiknak is, mely során betekintést kapnak a tavak nagyon sajátos tulajdonságainak megismerésébe és megtapasztalhatják a klímaváltozás okozta változásokat

Temporal variability of Achnanthidium minutissimum (Kützing) Czarnecki and its relationships to chemical and hydrological features of the Torna-stream, Hungary

Establishment of indicator values of species used in any kind of environmental quality assessment system has been of essential importance. This need is increased in case of species that are abundant. Achanthidium minutissimum has been, inevitably, one of the most frequently occurring diatom species all over Europe. Some authors list is as r-strategist aquatic weed that idndicates disturbed environment. The aim of our study was to analyze the temporal distribution of A. minutissimum in relation to physical and chemical parameters and to evaluate the data on basis of the existing diatom indices. In 2004-2005, diatom samples were taken biweekly and water samples for chemical analyses were collected once a month in the Torna-stream, W-Hungary. The diatom assemblages showed marked seasonal distribution, and the relative abundance of the A. minutissimum also varied throughout the year. We could find no clear correlation between the relative abundance of the a. minutissimum and either the fluctuation of the nitrogen and phosphorus forms or the major ions. Instead, there was significant correlation with Si content of the water which correlated with the seasonal changes of the discharge. The relative abundance of the A. minutissimum ashowed significant positive correlation with three diatom indices (IBD, EP-D, TDI): the higher abundance of the species resulted in better water quality. Against the IPS index (which is recommended to apply for ecological status assessment of Hungarian streams) we did not find significant correlation, consequently this index does not use the A. minutissimum as a potential indicator species. Based on the data we conclude that the discharge-dependent Si content of the streamwater and the r-strategy of the species determine the distribution of the A. minutissimum; it typically reaches higher dominance after flood periods and therefore indicates natural disturbances. Since flooding is a natural phenomenon existing also in reference state, the species’ abundance can not be used to assess the antropoghenic impacts. According to most diatom sampling protocols for WFD qualification, periods after floods should be avoided. In this view we may conclude that high contribution of A. minutissimum in any sample may indicate a preceding flood and therefore such samples do not provide a reliable basis for ecological status assessment

Kis vízfolyásokra épített tározók ökológiai hatásának bemutatása a Csigere-patak példáján

A kutatás elsődleges célja a kisvízfolyásokra épített tározók ökológiai hatásának vizsgálata, a Csigere-patak kovaalga összetételére és ökológiai állapotára. 2008 májusától 2010 márciusáig a patak tározó alatti szakaszáról hetente történtek fitobenton mintavételek, előzetesen kihelyezett mészkő szubsztrátumokról illetve minden mintavételkor helyszíni mérések és vízminta vétel. A patak legjellemzőbb fajai az Amphora pediculus, Cocconeis placentula és Rhoicosphenia abbreviata, melyek minden mintában előfordultak. A bevonat kovaalga összetétele a szezonalitás mellett jól mutatta a vízszint időszakos változását, mely a Széki- tó működtetésével függ össze. A nyári mintákban, amikor kisebb volt a patak vízhozama, dominánsként jelent meg az időszakos vizeket kedvelő Nitzschia palea. A halas-tó vízszintjének szabályozásával függ össze, hogy a vizsgálat során nagy számban olyan planktonikus kovaalga fajok (Cyclotella meneghiniana és Stephanodiscus nemzetség képviselői) is előkerültek a bevonatból, melyek eutróf tavak indikátor fajai. Ezen fajok relatív gyakorisága szignifikáns kapcsolatot mutatott a kovaalga indexekkel, főbb tápanyagformák koncentrációjával és a Széki-tó vízállásának változásával. Ennek köszönhetően jól alkalmazható a planktonikus kovaalga arány a hidromorfológiai módosítás mértékének leírására. A Csigere-patakra épített halas tó, mint átfolyásos víztározó fő hatása leginkább abból fakad, hogy a patak vízjárását megváltoztatja, illetve pontszerű tápanyagterhelést jelent az alvízre nézve

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

European shallow, alkaline, saline lakes are potential indicators of climate change. Diatoms have often been reported as valuable proxies for different kinds of anthropogenic activities. Diatom assemblages and 14 environmental variables from shallow, alkaline lakes from 2 different regions of the Carpathian basin (Europe) were investigated for 3 years to (1) elucidate the physical and chemical parameters and diatom assemblages of these lakes, (2) select the principle variables affecting the diatom communities, and (3) show the relevance of diatoms as ecological bioindicators. Water chemical characteristics of the lakes in the 2 regions differ significantly in anion concentrations (HCO3-;, SO42-;, and Cl-), platinum (Pt) units (colour), and oxygen saturation. Dominance by the stress-tolerant, motile diatom ecological guild, represented mainly by Nitzschia and Navicula species, was characteristic in these saline, turbid environments. Indicator species of the 2 regions were found to be different. Diatom assemblage composition was chiefly determined by conductivity and HCO3-; and SO42-concentrations. Nutrient loads, extreme weather events, and consequences of habitat maintenance management were unequivocally identifiable by variations in the benthic diatom assemblage composition. Diatoms are valuable indicators for assessment of ecological status of these saline, alkaline lakes. Including these organisms in ecological status assessments of inland saline lakes may improve the effectiveness of directives for conservation management and might be useful in preserving these pristine habitats that depend on natural hydrological processes

Beta-diversity and structuring forces of diatom communities in small lakes of the Carpathian Basin

Investigating the dynamics beyond the patterns (structure, diversity) of microbial communities at regional level in different spatial scales has been a developing area in ecology and studies on diatoms with such approach receive increasing scientific interest. In this study, phytobenthos samples were collected from 41 lakes (<7 km2) in the Carpathian Basin in August 2010 and physical and chemical parameters were also determined simultaneously. Our aim was to quantify the regional species pool (γ-diversity), the local species richness (α-diversity), the dissimilarity among diatom communities (β-diversity) and to assess whether β- diversity is supported by species replacement or richness differences (nestedness). Furthermore, we investigated the local contribution to β-diversity (LCBD) of our sampling sites and that which factors play a key role in establishment of β-diversity. In the study region, we experienced high γ- (a total of 302 diatom species) and α-diversity (average species richness of 45±13). The diatom community was characterised by high β-diversity (> 0.93 multiple-site Sørensen dissimilarity) which was explained mainly by species turnover. Although deterministic processes were more decisive based on null model analyses, stochasticity can also take part in community assembly. The degree of β-diversity (and thus assembly of communities, as well) was related significantly to the local environmental variables, especially to TP content and to the geographical distance between samplig sites. Samples from Kun-Fehér-tó, Pirtói Nagy-tó, Sárkány-tó and Vadása-tó showed significant relative contribution to β-diversity. Cl- and HCO3 - content were determining factors for LCBD, whereas local species richness was related to HCO3 - and water temperature. Moreover, we found a decline in LCBD with the increase of species richness. The study was supported by the National Scientific Research Foundation (OTKA K81599), the Széchenyi 2020 under the EFOP-3.6.1-16-2016-00015 and the ÚNKP-17-3-IV-PE-5 New National Excellence Program of the Ministry of Human Capacities