Planina Cave Research Articles

Microplastic pollution in vulnerable karst environments: case study from the Slovenian classical karst region

Since the start of mass production of plastic materials more than a century ago, the problem of accumulating plastic waste in the environment has reached epic proportions. Recently, the problem of smaller plastic particles (microplastic, MP) in the environment has become a widely studied topic, but the amount and types of MP in karst environments are still poorly known. Thus, the objective of this study was to collect and analyse samples from various karst habitats and to try and determine the scope of pollution in karst springs that are in part used as sources for drinking water. Of the potential pollution sources, we sampled rainwater, two discharges from wastewater treatment plants, and a leachate from a landfill. We conducted polymer analyses of potential MP particles using FTIR-ATR. The results showed that eight samples from the Postojna region (Postojna–Planina Cave System, rainfall sample and surface streams) contain up to 444 MP particles per m3. However, 32 samples taken from the Škocjan–Kačna–Jama 1 v Kanjaducah Cave System contain up to 60,000 MP particles per m3, with the bulk of particles found in the sediment samples from Škocjan Caves – Kačna Cave System. Samples from Postojna region contained mostly PET, PU and PA polymers, with a minor inclusion of polymers of plastic sponge used for cleaning. Samples from Škocjan region contained mostly PP, PET and PE polymers, with some of PA and PU polymers. Sediment samples contained much less MP particles compared to water samples, which indicates fast transport through karst aquifer.

Understanding the temporal variation of flow direction in a complex karst system (Planinska Jama, Slovenia)

Karst aquifers are abundant, but vulnerable water resources. Therefore, a deeper understanding of possible mechanisms that determine the properties of karst springs is crucial. In this work, we present an example of Unica Spring and Malni Spring, the two main outlets of a large karst system in the Notranjska karst region, Slovenia. Although the two springs share same catchment area, the flow distribution between them shows an interesting behaviour: At low-flow conditions, Malni Spring is the main outlet, while Unica spring receives almost no water. During high water events, discharge of Malni Spring stays limited and Unica Spring becomes the main outlet. We relate these observations to the local geometry of the channels and breakdowns in the remote part of the Planinska Jama (Planina Cave), called Mysterious Lake. There, waters from Rakov Škocjan and Javorniki aquifer merge and further diverge to both springs. At low water conditions, the outflow towards the Unica Spring is restricted by the breakdown, so that most of the inflow is directed towards the Malni Spring. With increasing recharge, the level in Mysterious Lake rises until the water starts to flow over the breakdown along a system of large channels (Rak Branch of Planinska Jama) to the Unica Spring. The breakdown level keeps the hydraulic head and the flow towards Malni Spring limited. To verify this scenario, a hydraulic conduit model was made based on the known and predicted channels, and inflows calculated from the historical data of discharge measurements at related springs and ponors. An inversion procedure was used to obtain a satisfactory fit to the observed discharge data and to constrain the selected model parameters. The model accurately reproduced the observed discharge behaviour under low- andhigh-flow conditions.

Biodegradation of the artificial sweetener saccharin in surface waters and groundwaters

The aim of this study was to evaluate the biodegradability of the artificial sweetener saccharin in surface waters and groundwater. Artificial sweeteners are generally persistent under environmental conditions and have been recently classified as emerging pollutants. Biodegradability in three surface waters and one groundwater was tested: the rivers Ljubljanica, Pivka, and Unica, and the groundwater Planina Cave (river Pivka). Under environmentally relevant conditions, saccharin degraded well in hypertrophic water (98%, 14 days) due to high concentrations of phosphorus and nitrogen. There was a longer lag phase and biodegradation time compared to the optimum conditions achieved in the standardized laboratory test. It has been concluded that saccharin is biodegradable in natural waters if said waters contain enough microorganisms and nutrients.

Environmental DNA in subterranean biology update: from “Where?” to “How many?”

Recent records of Proteus anguinus outside its historically known range (Gorički et al. 2017), discovered through detection of its DNA dissolved in groundwater (environmental DNA or eDNA), mark the beginning of a new era in the study and conservation of cryptic subterranean biodiversity. An upgraded technology, droplet digital PCR (ddPCR), initially developed for studies of gene expression, detection of genetically modified organisms and in medical diagnostics, is being tested for improved detection of the much smaller and rare stygobiont, the cave clam Congeria jalzici. In parallel to eDNA assay development for various stygobiotic species of the Dinaric Karst, a groundwater-sample library is being created. The samples will be available for future analysis of their species composition and will also serve as a source of information on any changes in species distribution over time. In another line of eDNA research, the utility of ddPCR for direct quantification of eDNA molecules in groundwater is being explored by using the large, accessible and well-characterized (Zakšek and Trontelj 2017) natural Proteus population in the Planina Cave (Slovenia) as a model. The eDNA methodology may in the future be applied in estimation and monitoring of Proteus population sizes without having to see, mark or otherwise disturb the animals themselves.

Analyzing climate change and surface-subsurface interactions using the Postojna Planina Cave System (Slovenia) as a model system

Worldwide, there are at least 12 ILTER sites with an emphasis on karst, landforms arising from the combination of high rock solubility and well-developed solutional channel porosity underground, but the study of cave ecosystems has been largely neglected. Only two ILTER sites, both in Slovenia, are primarily caves. Caves are under-represented for several reasons, but especially because of the overall difficulty of access and the lack of a clear research agenda for cave ecosystem studies. We review several aspects of long-term studies in Postojna Planina Cave System (PPCS), proposing our approach as a model for ILTER research in caves. In PPCS, analysis of short-term temperature data shows a muted daily cycle and seasonality, and analysis of long-term temperature data shows an increase, largely the result of climate change. Changes in drip rate of epikarst aquifers above the cave are correlated with rainfall but with lags and complications resulting from differences in longer term rainfall patterns. Analysis of discharge rates indicates a rapid response to precipitation not only in the Pivka River at its sinking, but also at Unica Spring, where discharge is augmented from other parts of the aquifer, including epikarst. Quantitative analysis of the obligate epikarst-dwelling copepod community shows that, unlike most cave communities, complete sampling of the fauna is possible. Finally, organic carbon levels in PPCS indicate likely carbon limitation in the system. These five factors (temperature, drip rate, river discharge, epikarst copepod fauna, and organic carbon) are the appropriate variables for capturing the essential long-term trends in cave ecosystems and their causes.

Organic Carbon in Shallow Subterranean Habitats

subterranean habitatsOrganic carbon is likely to be a limiting factor in shallow subterranean habitats (SSHs). Data on dissolved organic carbon (DOC) in three SSHs are reviewed: (1) hypotelminorheic and associated seepage springs (Nanos Mountain, Slovenia), (2) hyporheic zones (Rhône River, France and seepage streams on Nanos Mountain, Slovenia), and (3) epikarst (China, Slovenia, and USA). Hypotelminorheic habitats are superficial groundwater sites less than 1 m below the surface that exit from seepage springs. Hyporheic habitats are the underflow of streams and rivers. Epikarst is the uppermost zone of karst with extensive small cavities and channels. Nanos hypotelminorheic sites that harbored stygobiotic species had organic carbon values averaging 3.4 mg C L−1, and temporal variability was high. For hypoheic sites in the Rhône River basin and on Nanos Mountain, mean values ranged from 1.4 to 3.5 mg C L−1. In the more extensively studied Rhône River basin sites, temporal variability was low. Epikarst DOC ranged from 0.70 to 1.10 mg C L−1 in three caves in China (Shihua Cave), Slovenia (Postojna Planina Cave System) and United States (Organ Cave, West Virginia). These results suggest that organic carbon in aquatic SSHs is lowest in epikarst.Keywords: dissolved organic carbon, epikarst, hyporheic, hypotelminorheic, seepage spring.DOI: 10.3986/ac.v42i2.603

Holocene high floods on the Planina Polje, Classical Dinaric Karst, Slovenia

The Planina Polje is located in the northwestern part of Notranjsko Podolje, Slovenia. Annual floods cover the flattened floor of the polje at elevation 445 m a.s.l. and reach the depth of approximately 8 meters. Loamy sediments which were found on surface and subsurface features from the inflow part of Planina Polje up to the elevations of about 495 m a.s.l., indirectly show that floods in the past must have been much more extensive than the recent ones. Radiocarbon dating of flowstone layer from side passage Tiha Jama in Planina Cave revealed that the last such extreme floods appeared around 5,706 ± 49 BP. The time frame of the flood roughly corresponds with the Altithermal (8,000–5,000 BP). More humid mid-Holocene climate might be the main cause for the high floods on Planina Polje.Keywords: geomorphology, floods, radiocarbon dating (14C), Dinaric Karst, Planina Polje, Planina Cave.

Copepod distribution as an indicator of epikarst system connectivity

The distribution of 27 copepod species was determined in 35 drips in four Slovenian caves (Dimnice, Postojna Planina Cave System, Skocjanske Jame, Županova Jama), and of ten species from 13 drips in one US cave (Organ Cave, West Virginia). The dripping water comes from epikarst, the skin of karst. A significant fraction of the copepod species found (nine species in Slovenia and three in West Virginia) occurred over a maximum linear extent of 100 m. These and other localized distributions probably resulted from colonization of epikarst by an ancestral surface population in a single location, with subsequent lateral spread in the direction of epikarst flow. This suggests that the distribution of copepods could potentially be used to trace major flow paths in epikarst without the need for the injection of dyes or other tracers.

TRACE ELEMENT CONCENTRATIONS IN THE TISSUES OF PROTEUS ANGUINUS (AMPHIBIA, CAUDATA) AND THE SURROUNDING ENVIRONMENT

The concentrations of some essential (Cu, Zn, Se) and some toxicelements (Hg, As) were determined in tissues (liver, kidneys, integument, and muscle) of the endemic cave salamander, Proteus anguinus Laurenti 1768 and Proteus anguinus parkelj ssp.n. captured in the Planina Cave, Kompolje Cave, and Jelsevnik, all situated within the Dinaric Karst in Slovenia. The highest amounts of selenium and mercury were found in the liver of Proteus anguinus specimens from all three localities. Some of the animals from the Planina Cave showed higher concentrations of copper in the liver and muscle. Pigmented subspecies of Proteus from Jelsevnik showedincreased values of arsenic in the integument and of zinc in theliver and integument. The liver of the animals contained the highest amounts of the metals analysed and therefore may be considered as a target organ. Metal levels were also measured inthe cave water and sediments. The waters were not polluted withmetals. However, the metals were relatively high in the sediments, but not to levels considered contaminated. In additionto our study of metal concentrations in Proteus tissues andhabitats, several water quality parameters were measured in the water of each locality. The main differences between the threelocalities concerned dissolved oxygen concentration and saturation, while all other physical and chemical parameterswere characteristic of the aquatic environment in the calcareousKarst region.

Immunocytochemical demonstration of visual pigments in the degenerate retinal and pineal photoreceptors of the blind cave salamander ( Proteus anguinus )

Visual pigments in the regressed eye and pineal of the depigmented neotenic urodele, the blind cave salamander (Proteus anguinus anguinus), were studied by immunocytochemistry with anti-opsin antibodies. The study included light- and electron-microscopic investigations of both the eye and the pineal organ. A comparison was made with the black pigmented subspecies Proteus anguinus parkelj (black proteus), which has a normal eye structure. In the retina of the black proteus, we found principal rods, red-sensitive cones and a third photoreceptor type, which might represent a blue- or UV-sensitive cone. Photoreceptors in the regressed eye of the blind cave salamanders from the Planina cave contained degenerate outer segments, consisting of a few whorled discs and irregular clumps of membranes. The great majority of these outer segments showed immunolabelling for the red-sensitive cone opsin and only a few of them were found to be positive for rhodopsin. An even more pronounced degeneration was observed in the photoreceptors of the animals derived from the Otovec doline, which are completely devoid of an outer segment, most of them not even possessing an inner segment. Even in some of these highly degenerate cells, the presence of rhodopsin could be detected in the plasma membrane; however, immunoreactions with antibodies recognizing cone visual pigment were negative. In the pineals of all studied animals, the degenerate photoreceptor outer segments were recognized exclusively by the antibody against the red-sensitive cone opsin. The presence of immunopositive visual pigments indicates the possibility of a retained light sensitivity in the blind cave salamander photoreceptors.