Ecological Tolerance Research Articles

A palaeontological perspective on the proposal to reintroduce Tasmanian devils to mainland Australia to suppress invasive predators

The diversity of Australia's mammalian fauna has decreased markedly since European colonisation. Species in the small-to-medium body size range have been particularly badly affected. Feral cats and foxes have played a central role in this decline and consequently strategies for reducing their numbers are being evaluated. One such strategy is the reintroduction to the mainland of the Tasmanian devil, Sarcophilus harrisii. Here, we provide a palaeontological perspective on this proposal. We begin by collating published records of devil remains in Quaternary deposits. These data show that the range of devils once spanned all the main ecological zones in Australia. This indicates that they are capable of coping with a wide range of climatic and environmental conditions, and suggests that they could conceivably be reintroduced much more widely than has been thought possible hitherto. Subsequently, we examine fossils and coprolites from two sites in the Willandra Lakes Region World Heritage Area. These specimens not only support the suggestion that devils have wide ecological tolerances, but also suggest that devils can coexist with native small-to-medium species over long periods of time, which addresses one of the major concerns about the proposed reintroduction. We believe these two sets of palaeontological observations add substantial weight to the idea of reintroducing devils to the mainland as a way of suppressing cat and fox numbers.

The Onthophagus fuscus (Coleoptera: Scarabaeidae) species complex: an update and the description of a new species.

The Onthophagus fuscus Boucomont, 1932 (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini) species complex has a total of eight species, one of which is a new species (Onthophagus orizabensis new species) and three are elevated from the subspecies level (O. canescens Zunino Halffter, 1988 new rank; O. mycetorum Zunino Halffter, 1988 new rank; O. parafuscus Zunino Halffter, 2005 new rank). Onthophagus navarretorum Delgado Capistan, 1996 is included, while Onthophagus semiopacus has been removed from the species complex. The distribution map and key for the identification of species in this species complex are updated. Habitat preferences, ecological tolerance, and the restriction of this species complex to the mountains of the Mexican Transition Zone are discussed.

Correlational patterns of species diversity, swimming ability and ecological tolerance of non-marine ostracoda (Crustacea) with different reproductive modes in shallow water bodies of ağrı region (Turkey)

A total of 52 ostracod taxa (35 live spp. 17 subfossils) were collected from 70 shallow aquatic bodies with 11 different habitat types in Ağrı province (Turkey). Fabaeformiscandona acuminata is a new record for the Turkish ostracod fauna while 29 species were new for the province. Three types of habitats (stream, ditch and pond) contained the highest numbers of 24, 15, 11 species, respectively. Species were clustered into four main groups based on their distribution among habitats. Canonical Correspondence Analysis was able to explain 73.9% of the correlation between the 18 most frequently found species and five environmental variables. Water temperature and elevation were found to be the most effective factors on ostracods. Species with and without swimming setae tend to be found mostly in lentic and lotic habitats, respectively. Besides, species with swimming setae showed relatively higher ecological optimum and tolerance values for pH, electrical conductivity and water temperature than species without setae. The numbers of non-swimmer sexually reproducing species were twice the number of parthenogenetic species. Parthenogenetic species tend to have higher tolerance and optimum values for different environmental variables than sexual species. Results suggest a strong correlation among reproductive modes, swimming ability and ecological tolerances of the species.

New remains of Nothrotheriinae (Mammalia, Xenarthra) from Late Pleistocene fluvial deposits of Northern Pampa (Santa Fe Province, Argentina)

In this contribution the record of a Nothrotheriinae (Xenarthra, Tardigrada) ground sloth is reported from the Late Pleistocene of the Northern Pampa of Santa Fe Province, Argentina. The stratigraphic unit where the fossil was collected corresponds to fluvial-palustrine sediments of the Timbúes Formation, outcropping along the Carcarañá River valley. The relative stratigraphic position of this lithostratigraphic unit, observed in several sections mainly on the Paraná River cliffs near Carcarañá River distal area, suggests that it was deposited during the Last Interglacial Stage. The specimen (MPAHND-135), assigned to Nothrotherium cf. torresi, is represented by the proximal two-thirds of a left femur that shows a prominent lesser trochanter and no connection between the third trochanter and the ectepicondyle. The presence of Nothrotherium cf. torresi in sediments related to humid conditions supports the idea that Nothrotheriinae had great ecological tolerance and was capable of inhabiting climates ranging from cold and arid, as was previously proposed, to warm and humid.

To What Degree Can the Specifics of Occurrence of Glacial Relic Betula humilis Schrank Be an Indicator of Habitat Conditions of Moderate Climate Peatlands?

Anthropogenic transformations of habitat conditions in moderate climate peatlands frequently cause a decrease in the number of sites of occurrence and the size of the population of many valuable plant species, including the boreal relic Betula humilis. The objective of this paper was an attempt to relate the specifics of the occurrence of the glacial relic Betula humilis in the peatlands of Central-Eastern Poland, which developed under moderate climate conditions, to the conditions of the natural environment identified through research into the physical and chemical parameters of the groundwater, as well as botanical research into its habitat. The study results confirm that shrub birch has a broad range of ecological tolerance to the majority of the studied factors and can therefore be an indicator of habitat transformation. Important environmental factors affecting its abundance are water relations and the contribution of calcium hydroxide and phosphorus fractions. A condition favouring the proper functioning of individuals of the studied species is TP values lower than other obtained values, in the following range: 0.08–0.32; P-PO4: 0.1; TN: 2.2–21.2; N-NH4: 0.1–0.46; DOC: 24.6–55.9 (mg·dm−3), as well as higher than average pH values, in the following range: 5.34–5.95; Ca: 5.67–28.1; Mg: 0.56–2.41 (mg·dm−3) and EC: 72.1–142.3 (µS·cm−1).

An association between differential expression and genetic divergence in the Patagonian olive mouse (Abrothrix olivacea).

Recent molecular studies have found striking differences between desert-adapted species and model mammals regarding water conservation. In particular, aquaporin 4, a classical gene involved in water regulation of model species, is absent or not expressed in the kidneys of desert-adapted species. To further understand the molecular response to water availability, we studied the Patagonian olive mouse Abrothrix olivacea, a species with an unusually broad ecological tolerance that exhibits a great urine concentration capability. The species is able to occupy both the arid Patagonian steppe and the Valdivian and Magellanic forests. We sampled 95 olive mouse specimens from four localities (two in the steppe and two in the forests) and analysed both phenotypic variables and transcriptomic data to investigate the response of this species to the contrasting environmental conditions. The relative size of the kidney and the ratio of urine to plasma concentrations were, as expected, negatively correlated with annual rainfall. Expression analyses uncovered nearly 3,000 genes that were differentially expressed between steppe and forest samples and indicated that this species resorts to the "classical" gene pathways for water regulation. Differential expression across biomes also involves genes that involved in immune and detoxification functions. Overall, genes that were differentially expressed showed a slight tendency to be more divergent and to display an excess of intermediate allele frequencies, relative to the remaining loci. Our results indicate that both differential expression in pathways involved in water conservation and geographical allelic variation are important in the occupation of contrasting habitats by the Patagonian olive mouse.

Effect of mining site seepage and copper plant waste water on the water quality and epilithic diatom communities in Maden Stream (Elazığ-Turkey)

The present study investigated the effect of pollution caused by mining site seepage, copper plant flotation and domestic wastewaters on the water quality and epilithic diatom communities in the Maden Stream, Elazığ (Turkey). Maden Stream's epilithic diatoms, water chemistry and physical variables were examined between January 2008- December 2008 which identified 4 stream sites taken the samples of montly periods. During the study, a total of 77 diatom taxa belonging to 24 genera were identified. Three of which Cymbella, Navicula, and Nitzschia included the highest number of species. Species dominancy was changed among the stations where the most common species found from first, second, third, and fourth stations were Cymbella affinis, Ulnaria ulna, Achnanthes minutissima and Surirella angustata, and Gomphonema parvulum, respectively. Canonical correspondence analysis (CCA) explained 82.6% of the correlation between 66 species and 12 environmental variables among which EC, pH, DO, and Mn, were the most explanatory variables for species occurrence. Individual species showed different ecological tolerance and optimum levels. Among the species with cosmopolitan characteristics, eight of them (C. cistula, U. ulna, Nitzscia palea, N. sigmoida, G. parvulum, Achnanthes laceolatum, Navicula pupula, and Diatoma tenuis) were the most common species with relatively high tolerance levels to those environmental variables measured.

Phytostimulatory effect of silver nanoparticles (AgNPs) on rice seedling growth: An insight from antioxidative enzyme activities and gene expression patterns

The knowledge on the mode of action, biocompatibility and ecological tolerance of silver nanoparticles (AgNPs) is gradually accumulating over the years with contradictory findings. Most of the studies indicated the toxic impact of AgNPs on plant growth and development, where induction of oxidative stress was considered to be one of the causal factors. The present study demonstrates the phytostimulatory effect of bio-synthesized silver nanoparticles (AgNPs) during seed germination and seedling growth of rice (Oryza sativa L., cv. Swarna) under in vitro condition. All the tested concentrations of AgNPs (10, 20, 40 ppm) promote both the shoot and root growth which was evident from the increased length and biomass of the seedlings. Exposure to AgNPs also significantly increased the chlorophyll a and carotenoid contents. The content and the pattern of distribution of phenolic metabolites among the different treatments are indicative of non-toxic impact of AgNP mimicking mild or no stress to the seedlings. Growth stimulation of rice seedlings by AgNPs was further supported by a low level of reactive oxygen species (ROS) concomitant with decreased amount of lipid peroxidation and H2O2 content, compared to control. In order to unravel the stimulatory impact of AgNPs on rice seedling growth, the present study also describes the AgNPs induced changes in antioxidative enzyme activity and related gene expression levels. Elevated levels of catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) activities were recorded in all the AgNPs treated seedlings with improved growth. The activity of superoxide dismutase (SOD) was not significantly altered at low concentration of AgNPs. It appears that enzymes of ascorbate cycle, APX and GR are more active in ensuring protection against oxidative damage than SOD. There was significant up-regulation of CAT and APX gene expressions in seedlings exposed to AgNPs, whereas the expression level of CuZnSOD gene was decreased gradually with an increase in the concentration of AgNPs. The antioxidant enzyme activities and gene expression patterns coupled with the levels of H2O2 and lipid peroxidation indicates that the efficiency of redox reactions was increased in the presence of AgNPs and that accelerates the seedling growth.

Temporal patterns in the activity density and sex ratio of isopods (Oniscidea, Isopoda) along an urbanization gradient in Denmark

Urbanization effects on terrestrial isopod (Isopoda, Oniscidea) populations were studied in forested areas along a rural-to-urban gradient including a native beech forest, suburban and urban forest fragments in Sorø, Denmark. The seasonal activity patterns of the dominating species (Oniscus asellus, Philoscia muscorum and Porcellio scaber) indicated differences among the areas, but these patterns were idiosyncratic. There were more females than males in most areas. The seasonal patterns of males and non-gravid females were similar and often bimodal; gravid females showed markedly different, usually unimodal activity patterns. Temporal changes of sex ratios were — in each species — characterized by an early summer activity peak of males, followed by the activity peak of gravid females. We suggest that these trends might indicate a reproduction-driven surface activity of males. The small response of the three isopod species to urbanization may reflect their wide ecological tolerance as well as the “soft management” of the urban park.

Let me see your iD: Impacts of Environmental Stressors on Aquatic Ecosystems Assessed by (e)DNA Metabarcoding

Traditionally, taxonomic characterisation of organisms has relied on their morphology; however, molecular methods are increasingly used to monitor and assess biodiversity and ecosystem health. Approaches such as DNA amplicon diversity assessments are a particularly useful tool when morphology-based taxonomy is difficult or taxa are morphologically ambiguous, for example for freshwater bacteria and fungi as well as many freshwater invertebrate species. DNA metabarcoding provides the ability to distinguish cryptic taxa (which can differ markedly in their ecological requirements and tolerances) and in addition it can provide valuable insights into the genetic and ecological diversity of taxa and ecosystems. While DNA metabarcoding has been used mostly on tissue of sampled specimens, recent years have seen an increased use of metabarcoding on environmental DNA samples: DNA extracted not from sampled specimens, but from the surrounding soil or water. However, the ability of metabarcoding of specimens and metabarcoding of environmental DNA (eDNA) to assess biodiversity and the impact of anthropogenic stressors on freshwater ecosystems is largely understudied. In this talk, several studies that document the advantages and still open challenges of (e)DNA metabarcoding for assessing impacts of environmental stressors on aquatic ecosystems will be presented. These studies, performed in Europe and New Zealand, integrate impacts across different biotic groups, i.e. look at stressor effects on bacterial, protist, fungal and macroinvertebrate communities. Specifically, we use various case studies from freshwater ecosystems to address the following questions: whether eDNA samples, which can be relatively quickly obtained from the water, can act as reliable proxies for catchment-level stressor impacts by comparing these to DNA obtained from local bulk samples, and whether DNA metabarcoding data can also provide quantitative information rather than only presence-absence data. In view of the case studies presented, a perspective on the urgent next steps that need to be taken in order to include genetic tools in routine biomonitoring will be derived and linked to the vision of the international network DNAqua-Net.

Response of the aquatic plants and mollusc communities in Lake Kojle (central Europe) to climatic changes between 250 BCE and 1550 CE

Sediments of Lake Kojle, located in the transition zone between the nemoral and boreal biogeographic zones in NE Poland, were analysed to verify the response of the aquatic ecosystem to major environmental changes. High-resolution plant macrofossil, mollusc and pollen data were derived from two replicate parallel cores and revealed several shifts in the biota composition within the littoral zone between 250 BCE and 1550 CE. The reaction of the aquatic ecosystem to temperature changes was found to be minor, which is ascribed to the mitigating influence of water and the wide ecological tolerance of most of the taxa. Najas marina, considered as an indicator of warmer conditions, was the only species that clearly reacted to the long-term climate shifts. We consider lake level changes that resulted from fluctuations in climate humidity and the filling of the lake with sediments as the most important factors that control the presence of macrophytes species from the genera Nymphaea, Nuphar, Typha, and Chara. Mollusc diversity and abundance increased with the increase in the diversity and biomass of submerged vegetation. However, reduced dissolved oxygen within the water column under the floating leaves of Nymphaea alba and Nuphar sp. resulted in the retreat of Planorbis carinatus, a gastropod species sensitive to oxygen shortages. Major shifts in the developments of fauna and flora were parallel in the two studied cores, but some spatial variability was observed. This might be due to the spatial variability of the macrophyte and mollusc communities within Lake Kojle.

Integrative taxonomy of freshwater ostracodes (Crustacea: Ostracoda) of the Yucatán Peninsula, implications for paleoenvironmental reconstructions in the northern Neotropical region

A three-step integrative taxonomy approach combining molecular, morphological and ecological methods was successfully used to delimit species boundaries within three freshwater ostracode taxa of the Yucatán Peninsula (Mexico): Darwinulidae, Cypretta and Cypridopsis. These species groups were selected because they are well-suited paleobioindicators for late Pleistocene-early Holocene climatic reconstructions in the region, but their high inter-population morphological variability in recent communities represents a challenge for accurate transfer of information to fossil assemblages.As a first step, we analyzed the congruence of two genes of different inheritance, the mitochondrial COI (cytochrome c-oxidase subunit 1), and the nuclear 18S rDNA (small-subunit rDNA). Second, we tested the lineages discriminated for concordant differentiation in morphology, using morphometry of the carapace and typological analysis of the appendages. The third step assessed the association of occurrences and abundances of lineages to environmental variables. The integration of these methods revealed six hidden species within clades previously considered as a single widely distributed nominal species. Of these, Cypretta elongata sp. nov. and Alicenula yucatanensis sp. nov. are herein formally named and described given their morphological distinctness. Three species of Cypridopsis: Cypridopsis sp. [Ca1 ECO-CH-Z-09396], Cypridopsis sp. [Ca2 ECO-CH-Z-09398], Cypridopsis sp. [Ca3 ECO-CH-Z-09401] and a species that may represent a new genus, Cyprididae sp. [Ca1 ECO-CH-Z-09402], are allocated to a confirmed candidate full species status. Cypretta maya and Cypretta sp., considered a priori as separate species, are recognized as a single species with phenotypic plasticity, attributed to its broad ecological tolerances. For paleoenvironmental reconstructions these results have relevance because the particular carapace morphology of the new species can be correlated with specific ecological traits, thus constituting a potential tool for refining interpretations of fossil assemblages.

ENVIRONMENTAL ANALYSIS OF HABITATS OF ARTIFICIAL CENOPOPULATIONS OF RARE AND ENDANGERED PLANTS

Ecological analysis was performed for localities of Belarusian rare and endangered plant species created in the Central Botanical Garden of NAS of Belarus. Artificial cenopopulations of Astrantia major L., Allium ursinum L., Lunaria rediviva L., Hedera helix L. were analyzed in ecological space of the Central Botanical Garden by estimating ecological valence, tolerance and biocompatibility. Comparison between ecological amplitudes and optimums of species studied allows environmental stress points to be identified towards their ecomorphs. Представлены результаты экологического анализа местообитаний редких и исчезающих видов растений природной флоры в условиях Центрального ботанического сада НАН Беларуси. Объектами исследования являлись искусственные ценопопуляции Astrantia major L., Allium ursinum L., Lunaria rediviva L., Hedera helix L. Определены следующие количественные показатели: экологическая валентность, экологическая толерантность и бионтность четырех видов. Путем сопоставления экологической амплитуды и экологического оптимума найдены точки напряженности среды по отношению к экоморфам изучаемых видов.

Higher ploidy is associated with reduced range breadth in the Potentilleae tribe.

Polyploids are predicted to have greater niche breadth and larger ranges than diploids because of higher ecological tolerances, self-compatibility, and increased genetic variation. However, empirical support for this prediction is mixed, and most studies compare diploids and polyploids, rather than accounting for quantitative variation in ploidy. We test the prediction that species of higher ploidy have greater range breadth and abiotic breadth than those of lower ploidy. We estimate range breadth (latitudinal range, altitudinal range, and range size) and abiotic breadth (range in temperature, precipitation, and ultraviolet-B irradiance) for 109 species in the Potentilleae tribe of Rosaceae. We assess the contribution of ploidy to variation in range breadth, while accounting for shared evolutionary history and time of species divergence using phylogenetic comparative methods. Ploidy varied widely among species from 2× to 12×. Phylogenetic relatedness explained little of the variation in ploidy, range breadth, and abiotic breadth. Transitions to higher ploidy were associated with reduced latitudinal and altitudinal ranges, smaller overall range size, and reduced abiotic breadth for temperature and UV-B. In contrast to predictions, this study shows that transitions to higher ploidy are associated with reduced range size and abiotic breadth. It also highlights the importance of considering continuous variation in ploidy when evaluating ecological correlates with ploidy. We discuss how genome duplication may contribute to the observed negative relationship between ploidy and range breadth.

Assembly of Alaska‐Yukon boreal steppe communities: Testing biogeographic hypotheses via modern ecological distributions

AbstractBeringia (eastern Asia, Alaska, northwest Canada) has been a land‐bridge dispersal route between Asia and North America intermittently since the Mesozoic Era. The Quaternary, the most recent period of exchange, is characterized by large, geologically rapid climate fluctuations and sea‐level changes that alternately expose and inundate the land‐bridge region. Insights into how Quaternary land‐bridge geography has controlled species exchange and assembly of the North American flora comes from focusing on a restricted community with narrow ecological tolerances: species that are today restricted to isolated steppe habitats (dry grasslands) in the Subarctic. We evaluated (i) potential controls over current spatial distributions of steppe plants and their pollinators in Alaska and Yukon and (ii) their ecological distributions in relation to potential biogeographic histories. Taxa present in North America that are disjunct from Asia tended to have larger altitudinal ranges (tolerating colder temperatures) than taxa disjunct from farther south in North America, which were largely restricted to the warmest, lowest‐elevation sites. Ecological findings support the following biogeographic scenarios. Migration from Asia via the land‐bridge occurred during Quaternary glacial periods when conditions were colder and drier than today. While a corridor for migration of cold‐tolerant species of cold steppe and tundra, the land bridge acted as a filter that excluded warmth‐demanding species. Migration from North America occurred under warm, dry interglacial conditions; thermophilous North American disjuncts taking this route may have long histories in Beringia, or they may have migrated recently during the relatively warm and dry early Holocene, when forest cover was incomplete.

Unravelling the adaptation strategies employed by Glaciozyma antarctica PI12 on Antarctic sea ice

Glaciozyma antarctica PI12, is a psychrophilic yeast isolated from Antarctic sea. In this work, Expressed Sequence Tags (EST) from cells exposed to three different temperatures; 15 °C, 0 °C and −12 °C were generated to identify genes associated with cold adaptation. A total of 5376 clones from each library were randomly picked and sequenced. Comparative analyses from the resulting ESTs in each condition identified several groups of genes required for cold adaptation. Additionally, 319 unique transcripts that encoded uncharacterised functions were identified in the −12 °C library and are currently unique to G. antarctica. Gene expression analysis using RT-qPCR revealed two of the unknown genes to be up-regulated at −12 °C compared to 0 °C and 15 °C. These findings further contribute to the collective knowledge into G. antarctica cold adaptation and as a resource for understanding the ecological and physiological tolerance of psychrophilic microbes in general.

Genotoxicity effects of silver nanoparticles on wheat (Triticum aestivum L.) root tip cells

The distribution and use of nanoparticles have rapidly increased over recent years, but the available knowledge regarding their mode of action, ecological tolerance and biodegradability remains insufficient. Wheat (Triticum aestivum L.) is the most important crop worldwide. In the current study, the effects of silver nanoparticles (AgNPs) obtained from two different sources, namely, green and chemical syntheses, on chromosomal aberrations and cell division were investigated. Wheat root tips were treated with four different AgNP concentrations (10, 20, 40 and 50 ppm) for three different exposure durations (8, 16 and 24 h), and the different concentrations of the nanoparticles were added to the tested grains until the root lengths reached 1.5–2 cm. For each concentration, the mitotic indexes (%) were obtained from an analysis of ~ 2000 cells. The treated root-tip cells exhibited various types of chromosomal aberrations, such as incorrect orientation at metaphase, chromosomal breakage, metaphasic plate distortion, spindle dysfunction, stickiness, aberrant movement at metaphase, fragmentation, scattering, unequal separation, scattering, chromosomal gaps, multipolar anaphase, erosion, and distributed and lagging chromosomes. These results demonstrate that the root tip cells of wheat can readily internalize the AgNPs and that the internalized AgNPs can interfere with the cells’ normal function.

Intraspecific ecological niche divergence and reproductive shifts foster cytotype displacement and provide ecological opportunity to polyploids.

Niche divergence between polyploids and their lower ploidy progenitors is one of the primary mechanisms fostering polyploid establishment and adaptive divergence. However, within-species chromosomal and reproductive variability have usually been neglected in community ecology and biodiversity analyses even though they have been recognized to play a role in the adaptive diversification of lineages. We used Paspalum intermedium, a grass species with diverging genetic systems (diploidy vs. autopolyploidy, allogamy vs. autogamy and sexuality vs. apomixis), to recognize the causality of biogeographic patterns, adaptation and ecological flexibility of cytotypes. Chromosome counts and flow cytometry were used to characterize within-species genetic systems diversity. Environmental niche modelling was used to evaluate intraspecific ecological attributes associated with environmental and climatic factors and to assess correlations among ploidy, reproductive modes and ecological conditions ruling species' population dynamics, range expansion, adaptation and evolutionary history. Two dominant cytotypes non-randomly distributed along local and regional geographical scales displayed niche differentiation, a directional shift in niche optima and signs of disruptive selection on ploidy-related ecological aptitudes for the exploitation of environmental resources. Ecologically specialized allogamous sexual diploids were found in northern areas associated with higher temperature, humidity and productivity, while generalist autogamous apomictic tetraploids occurred in southern areas, occupying colder and less productive environments. Four localities with a documented shift in ploidy and four mixed populations in a zone of ecological transition revealed an uneven replacement between cytotypes. Polyploidy and contrasting reproductive traits between cytotypes have promoted shifts in niche optima, and increased ecological tolerance and niche divergence. Ecologically specialized diploids maintain cytotype stability in core areas by displacing tetraploids, while broader ecological preferences and a shift from sexuality to apomixis favoured polyploid colonization in peripheral areas where diploids are displaced, and fostered the ecological opportunity for autotetraploids supporting range expansion to open southern habitats.

A humid early Holocene in Yemen interpreted from palaeoecology and taxonomy of freshwater ostracods

Abstract. Lake or marsh sediments in the Qa'a Jahran–Dhamār area indicate a period of higher moisture availability in the early Holocene of the highlands of Yemen. Forty-two marl–peat sediment samples from eight stratigraphic sections of that area have been collected and are examined for the first time for their ostracod associations. Eight species belonging to seven genera and four families are reported. Their ecological tolerances and preferences are used to investigate the climatic and environmental changes in the early to mid-Holocene. Our data are compared and correlated with previous archaeological results, particularly from the region of Qa'a Jahran (Dhamār) in the vicinity of the village of Beyt Nahmi. We conclude that the wettest period of the Holocene was from about 7900 to 7400 cal yr BP, when northwards incursion of the Indian Ocean Monsoon caused intensified monsoon precipitation over southern Arabia.

Ciliated protozoa in the impact zone of the Uzhgorod treatment plant

This paper presents the results of studies on the Uzh River (Ukraine, Zakarpattia Oblast) near the effluent point of a sewage treatment plant in Uzhgorod. The samples were taken at various sites of the treatment plant along the stages of purification process, as well as in the river, at a number of different points above and below the wastewater discharge. At each of these objects, the temperature and O2were measured. The structure of ciliate assemblage was analyzed along the stages of the treatment process in the WWTP and in the river before and after the sewage discharge. A total of 26 ciliate taxa were observed and included in the analysis. All the studied stations were considered as a continuum in which populations of protozoa spread freely according to their ecological preferences. The majority of ciliate species were encountered in each of the examined stations, but their quantitative development differed significantly, reflecting their response to the environmental conditions at the stations. The analysis of the qualitative and quantitative distribution of ciliate populations by the stations enabled to group them in respect to the peculiarities of the local conditions. The study showed that the majority of the ciliate species, typical of bioreactors, are equally common at the stations of the Uzh River below wastewater discharges. The ciliate assemblage in the oxygen gradient demonstrated a wide spectrum of ecological tolerance at the species level. These findings confirm that ciliates are very good indicators of the environmental quality, provided that detailed information about their environmental priorities is available.