Lake Kastoria Research Articles

Absolute dating of the European Neolithic using the 5259 BC rapid 14C excursion

Abrupt radiocarbon (14C) excursions, or Miyake events, in sequences of radiocarbon measurements from calendar-dated tree-rings provide opportunities to assign absolute calendar dates to undated wood samples from contexts across history and prehistory. Here, we report a tree-ring and 14C-dating study of the Neolithic site of Dispilio, Northern Greece, a waterlogged archaeological site on Lake Kastoria. Findings secure an absolute, calendar-dated time using the 5259 BC Miyake event, with the final ring of the 303-year-long juniper tree-ring chronology dating to 5140 BC. While other sites have been absolutely dated to a calendar year through 14C-signature Miyake events, Dispilio is the first European Neolithic site of these and it provides a fixed, calendar-year anchor point for regional chronologies of the Neolithic.

Kastoria and Mikri Prespa Lakes: The Impact of Anthropogenic Activities on the Differentiation in the Genotoxic and Toxic Profile of the Surface Water

Urban–industrial and agricultural waste can add significant amounts of pollutants to surface water. Therefore, the surface water from Mikri Prespa and Kastoria lakes was assessed for its toxic, genotoxic, and cytotoxic effects. Water samples were collected during the spring of two different years (S1 and S2) in order to investigate the anthropogenic effects on both lakes. Physicochemical parameters were identified, while significant elements were determined via ICP-MS/MS. The in vitro cytokinesis-block micronucleus (CBMN) assay in cultured human lymphocytes and the Aliivibrio fischeri bioassay were applied to evaluate the genotoxic–cytotoxic and toxic effects, respectively. In the CBMN assay, significant differences were observed in genotoxic and cytotoxic indices between the different time periods. Decreased indices in S2 could be correlated with a potential diminution in the negative human effect on the environment along the lakes. In the Aliivibrio fischeri bioassay, no significant difference in the toxicity of the surface water samples from Mikri Prespa was observed, whereas significant differences were identified in the samples from Lake Kastoria. The differences in toxic, genotoxic, and cytotoxic effects reveal the impact and the influence of anthropogenic activities in the areas of land around the lakes in relation to their surface water quality.

Untargeted and targeted LC-MS and data processing workflow for the comprehensive analysis of oligopeptides from cyanobacteria

Cyanobacteria produce a plethora of structurally diverse bioactive secondary metabolites, including cyanotoxins which pose a serious threat to humans and other living organisms worldwide. Currently, a wide variety of mass spectrometry-based methods for determination of microcystins (MCs), the most commonly occurring and studied class of cyanotoxins, have been developed and employed for research and monitoring purposes. The scarcity of commercially available reference materials, together with the ever-growing range of mass spectrometers and analytical approaches, make the accuracy of quantitative analyses a critical point to be carefully investigated in view of a reliable risk evaluation. This study reports, a comparative investigation of the qualitative and quantitative MCs profile obtained using targeted and untargeted liquid chromatography–mass spectrometry approaches for the analyses of cyanobacterial biomass from Lake Kastoria, Greece. Comparison of the total MCs content measured by the two approaches showed good correlation, with variations in the range of 3.8–13.2%. In addition, the implementation of an analytical workflow on a hybrid linear ion trap/orbitrap mass spectrometer is described, based on combining data-dependent acquisition and a powerful database of cyanobacterial metabolites (CyanoMetDB) for the annotation of known and discovery of new cyanopeptides. This untargeted strategy proved highly effective for the identification of MCs, microginins, anabaenopeptins, and micropeptins. The systematic interpretation of the acquired fragmentation patterns allowed the elucidation of two new MC structural variants, MC-PrhcysR and MC-Prhcys(O)R, and proposal of structures for two new microginins, isomeric cyanostatin B and MG 821A, and three isomeric micropeptins at m/z 846.4715, 846.4711 and 846.4723.

Deep Learning in Water Resources Management: Τhe Case Study of Kastoria Lake in Greece

The effects of climate change on water resources management have drawn worldwide attention. Water quality predictions that are both reliable and precise are critical for an effective water resources management. Although nonlinear biological and chemical processes occurring in a lake make prediction complex, advanced techniques are needed to develop reliable models and effective management systems. Artificial intelligence (AI) is one of the most recent methods for modeling complex structures. The applications of machine learning (ML), as a part of AI, in hydrology and water resources management have been increasing in recent years. In this paper, the ability of deep neural networks (DNNs) to predict the quality parameter of dissolved oxygen (DO), in Lake Kastoria, Greece, is tested. The available dataset from 11 November 2015, to 15 March 2018, on an hourly basis, from four telemetric stations located in the study area consists of (1) Chl-a (μg/L), (2) pH, (3) temperature—Tw (°C), (4) conductivity (μS/cm), (5) turbidity (NTU), (6) ammonia (NH4, mg/L), (7) nitrate nitrogen (N–NO3, mg/L), and (8) dissolved oxygen (DO) (mg/L). Feed-forward deep neural networks (FF-DNNs) of DO, with different structures, are tested for all stations. All the well-trained DNNs give satisfactory results. The optimal selected FF-DNNs of DO for each station with a high efficiency (NSE > 0.89 for optimal selected structures/station) constitute a good choice for modeling dissolved oxygen. Moreover, they provide information in real time and comprise a powerful decision support system (DSS) for preventing accidental and emergency conditions that may arise from both natural and anthropogenic hazards.

Isotope hydrology model and stable isotopes in sediment records from Balkan lakes

<p>Isotope mass balance in lake systems is strongly correlated with several climatic factors such as temperature, evaporation, precipitation and air moisture. On the other hand, the sedimentary budget of lake basins driven by climate, tectonic and/or human impact is an essential pool of environmental records. Precipitation, springs and lake water δD and δ18O isotope data were used in order to understand the key factors for the hydrological balance of Balkan lakes in West Macedonia. In general, it is concluded that the open lake Ohrida and the semi-closed lake Kastoria are more buffered hydrological as karst systems and less sensitive to evaporation effect, in contrast to the closed lake system of Prespes that present a strong dependence on climate seasonality. Based on oxygen isotopes in bulk sediments, it is concluded that in Kastoria lake basin an increased run-off on the land surface, probably under a more humid period, in 2.4 kyr BP disturbed the transition to a drier regime from mid/late Holocene to present.</p>

Plant species richness and composition of a habitat island within Lake Kastoria and comparison with those of a true island within the protected Pamvotis lake (NW Greece).

Lake Kastoria is one of the potentially “ancient” Balkan lakes that has a great environmental importance and ecological value, attracts high touristic interest and is under various anthropogenic pressures. It belongs to a Natura 2000 Special Protection Area and a Site of Community Interest. The city of Kastoria is located at the western part of the lake and just next to it, towards the centre of the lake, is a peninsula, a habitat island. In the framework of research concerning the flora of lake islands of Greece, one of the main objectives of the present study is to fill a gap concerning plant species richness of the habitat island within the protected Lake Kastoria, which is surrounded by the lake except for its north-western part where the border of the city of Kastoria is located. Floristic analysis of the habitat island of Lake Kastoria is in large measure accounted, concerning chorology with emphasis on Balkan endemics (8.7%), life forms, by hemicryptophytes (36.1%), therophytes (33.2%), phanerophytes (16.4%) and geophytes (10.9%) and, for habitats, by taxa preferring agricultural and ruderal ones (53.3%). Another objective is to compare its floristic composition to the one of the island within the protected urban Lake Pamvotis - one of the very few lake islands in Greece - focusing on the influence of urbanisation. The α- and β- diversity are measured in order to reveal floristic differences. Beta diversity partitioning in turnover and nestedness showed that the β-diversity is mostly expressed as compositional turnover. The role of the society in combination with long-term programmes for the study of plant species richness, functional diversity and patterns of species assemblages over time are necessary for the effective management and protection of protected areas, including lake insular areas.

Applying A Modified Contingent Valuation Method (CVM) For The Preservation/Restoration Of The Lake Kastoria In Northern Greece

The preservation/restoration of natural environment is frequently entailing excessive cost (paid by people through taxation) while it is a source of additional income for both, the State and the people, due to tourism. Since the evaluation of this good cannot be in market terms, we apply herein a modified version of the Contingent Valuation Method (CVM), which is used in Experimental Economics in order to investigate the significance that people put on this good and how much they might be willing to pay (WTP) for supporting activities concerning the preservation/restoration of Lake Kastoria. The WTP dependence on (i) external diseconomies, (ii) the expectations for property values’ rise as a result of the restoration, (iii) the proximity of interviewees’ residence to the lake, (iii) the opinion of the interviewee on the time and money spent to visit the lake, (iv) the time and money the interviewees spent to visit the lake, as well as other dependencies (all taken as independent variables) are estimated by means of Logit, Probit, Logistic and Linear Regression Models.

Occurrence and diversity of cyanotoxins in Greek lakes

Toxic cyanobacteria occur in Greek surface water bodies. However, studies on the occurrence of cyanotoxins (CTs) are often limited to mainly microcystins (MCs), with use of screening methods, such as ELISA, that are not conclusive of the chemical structure of the CT variants and can be subject to false positive results. A multi-lake survey in Greece (14 lakes) was conducted in water and biomass, targeted to a wide range of multi-class CTs including MCs, nodularin-R (NOD), cylindrospermopsin (CYN), anatoxin-a (ANA-a) and saxitoxins (STXs), using multi-class/variant LC-MS/MS analytical workflows, achieving sensitive detection, definitive identification and accurate quantitation. A wide variety of CTs (CYN, ANA-a, STX, neoSTX, dmMC-RR, MC-RR, MC-YR, MC-HtyR, dm3MC-LR, MC-LR, MC-HilR, MC-WR, MC-LA, MC-LY, MC-LW and MC-LF), were detected, with MCs being the most commonly occurring. In biomass, MC-RR was the most abundant toxin, reaching 754 ng mg−1 dw, followed by MC-LR (458 ng mg−1 dw). CYN and ANA-a were detected for the first time in the biomass of Greek lakes at low concentrations and STXs in lakes Trichonis, Vistonis and Petron. The abundance and diversity of CTs were also evaluated in relation to recreational health risks, in a case study with a proven history of MCs (Lake Kastoria).

An Application of ‘Willingness to Pay’ Method as a Quantifier for Environmental Impact Assessment

The preservation/restoration of natural environment is frequently entailing excessive cost (paid by people through taxation) while it is a source of additional income for both, the State and the people, due to tourism. Since the evaluation of this good cannot be in market terms, it is applied here in a modified version of the CVM (Contingent Valuation Method), which is used in experimental economics in order to investigate the significance that people put on this good and how much they might be WTP (Willing to Pay) for supporting activities concerning the preservation/restoration of Lake Kastoria. The WTP dependence on (i) external diseconomies; (ii) the expectations for property values’ rise as a result of the restoration; (iii) the proximity of interviewees’ residence to the lake; (iv) the opinion of the interviewee on the time and money spent to visit the lake; (v) the time and money the interviewees spent to visit the lake, as well as other dependencies (all taken as independent variables) are estimated by means of logit, probit, logistic and linear regression models. The optimal concentration Copt of a pollutant in the environment can be determined as an equilibrium point in the tradeoff between (i) environmental cost, due to impact on man/ecosystem/economy; and (ii) economic cost for environmental protection, as it can be expressed by Pigouvian tax. These two conflict variables are internalized within the same techno-economic objective function of total cost, which is minimized. In this work, the first conflict variable is represented by a WTP index. A methodology is developed for the estimation of this index by using fuzzy sets to count for uncertainty. Implementation of this methodology is presented, concerning odor pollution of air round an olive pomace oil mill.

An Application of ‘Willingness to Pay’ Method as a Quantifier for Environmental Impact Assessment

The preservation/restoration of natural environment is frequently entailing excessive cost (paid by people through taxation) while it is a source of additional income for both, the State and the people, due to tourism. Since the evaluation of this good cannot be in market terms, it is applied here in a modified version of the CVM (Contingent Valuation Method), which is used in experimental economics in order to investigate the significance that people put on this good and how much they might be WTP (Willing to Pay) for supporting activities concerning the preservation/restoration of Lake Kastoria. The WTP dependence on (i) external diseconomies; (ii) the expectations for property values’ rise as a result of the restoration; (iii) the proximity of interviewees’ residence to the lake; (iv) the opinion of the interviewee on the time and money spent to visit the lake; (v) the time and money the interviewees spent to visit the lake, as well as other dependencies (all taken as independent variables) are estimated by means of logit, probit, logistic and linear regression models. The optimal concentration Copt of a pollutant in the environment can be determined as an equilibrium point in the tradeoff between (i) environmental cost, due to impact on man/ecosystem/economy; and (ii) economic cost for environmental protection, as it can be expressed by Pigouvian tax. These two conflict variables are internalized within the same techno-economic objective function of total cost, which is minimized. In this work, the first conflict variable is represented by a WTP index. A methodology is developed for the estimation of this index by using fuzzy sets to count for uncertainty. Implementation of this methodology is presented, concerning odor pollution of air round an olive pomace oil mill.

Fish Consumption Patterns of Populations in Vicinities of Lake Kastoria and Lake Pamvotis, Greece

Fish Consumption Patterns of Populations in Vicinities of Lake Kastoria and Lake Pamvotis, Greece

Preface: Biogeography and spatial patterns of biodiversity of freshwater phytoplankton

The 17th workshop of the International Association for Phytoplankton Taxonomy and Ecology (IAP) was held in Greece, in the Municipality of Kastoria from 14th to 21st September 2014, and its main ecological theme was the biogeography of phytoplankton and the importance of spatial scales. The main IAP objectives are to get together preeminent as well as young scientists and students working on various aspects of phytoplankton taxonomy and ecology to discuss topics of current interest, to jointly examine water samples under the microscope and practice species identification under the guidance of leading experts, and to encourage young scientists to engage in taxonomy research—a field where expertise is vanishing. Following the traditions of the IAP, close to 100 participants attended the workshop, more or less equally divided between professional scientists and students. The venue where the meeting was held provided a spectacular site located on the shore of Lake Kastoria surrounded by Macedonian mountains. The microscopy sessions in the afternoons were guided by established taxonomists and attended by keen-to-learn young scientists who jointly examined fresh and preserved samples brought by the participants. The IAP was established in 1979 (Kristiansen, 2003), and since then 16 workshops were held at different locations. Since 1991, each workshop had a well-defined ecological theme, and taxonomic topics. Proceedings of all these workshops have been published in journals with peer-reviewed articles and have played a leading role in advancing phytoplankton community ecology. Since the early 1990s, the following proceedings volumes appeared in special issues of Hydrobiologia:

Plant landscape and land use at the Neolithic lake settlement of Dispilió (Macedonia, northern Greece)

The Neolithic settlement of Dispilió (lake Orestiás, northern Greece) is a unique site due to its continual inhabitation from the Middle Neolithic (5400 BC) to the Chalcolithic (3600 BC) and its exceptional location at the shore of Lake Orestiás (also known as Lake Kastoria). The plant landscape shaping of the area has been examined by correlating pollen and non-pollen palynomorphs from both on-site and off-site records. The examined pollen profiles bear concrete evidence of agricultural activities and land use in the area. The local pollen assemblages identified, each of them corresponding either to a different kind or intensity of exploitation of natural resources, display the diachronic evolution of the cultural landscape during more than 2000 years of human activity. The successive phases of intense human impact on vegetation patterns are in good accordance with the periods of major constructing activities described by the archaeological study of the Dispilió settlement. Finally, the differences on palynomorph accumulation pathways of the examined records made possible the distinction between local and “regional” plant landscapes and related human activities.

Assessment of the typology and the trophic status of two Mediterranean lake ecosystems in Northwestern Greece

The objective of this study is the assessment of the typology and the trophic relevant water quality parameters in two Mediterranean lakes (Lake Ziros and Lake Kastoria) under the view of the WFD. Lake types were identified based on characteristics specified in Annex II of the WFD, while trophic indexes (OECD, TSI Carlson) were used in order to assess their trophic status. A modified TSI index appropriate for warmer lakes was also applied. According to our results, Lake Kastoria is classified as eutrophic lake with a tendency to hypertrophication while Lake Ziros is a mesotrophic ecosystem with clear signals of eutrophication. Both ecosystems are considered “at risk” of not fulfilling the WFD environmental objectives due to the existence of certain anthropogenic pressures.

Molecular detection of potentially toxic cyanobacteria and their associated bacteria in lake water column and sediment

We investigated the molecular diversity of cyanobacteria and bacteria during a water bloom in a lake with a long history of toxic cyanobacterial blooms (Lake Kastoria, Greece). We also tested the hypothesis whether bloom-forming cyanobacteria are preserved in the lake’s sediment 2 years after the bloom. The dominant cyanobacteria during the bloom included the potentially toxin-producing Microcystis aeruginosa and several other Chroococcales forms closely related to the genus Microcystis. This suggests that the use of cyanobacterial-specific primers seems to be very informative in describing the cyanobacteria during the water blooms. The bacterial community showed high diversity, consisting mostly of singleton and doubleton phylotypes. The majority of the phylotypes were typical lake bacteria including some potential pathogens and toxin metabolising bacteria, suggesting that the dominant toxic cyanobacteria did not have any significant effect on the bacterial community structure. In the sediment, 2 years after the water bloom, no bloom-forming cyanobacteria were retrieved, suggesting that they cannot be preserved in the sediment. Similar to the water column, sediment bacterial diversity was also high, consisting mostly of yet-uncultured bacteria that are related to environments where organic matter degradation takes place.

Water Quality Monitoring and Modeling in Lake Kastoria, Using GIS. Assessment and Management of Pollution Sources

Lake Kastoria, is a very fragile aquatic ecosystem, protected by several national and international conventions, situated in the Region of Western Macedonia, Greece. A monthly monitoring program has been operated by the Municipality of Kastoria, during the past 5 years (2002–2007). The water quality parameters monitored, are: Water Temperature (Tw), dissolved oxygen (DO), BOD, COD, pH, water conductivity (ECw), redox potential (RP), nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N), ammonium nitrogen (NH4-N) and orthophosphates-dissolved inorganic phosphorus (PO4-P-DIP). This study focuses on the water quality parameters of Tw, DO, NH4-N, NO3-N and PO4-P. The sampling points are five, scattered in specific positions in the Lake (Sioutista, Xiropotamos, Mavriotissa, Northern Beach and Stavros—Southern Beach). A comparison took place between two spatial–geographic deterministic simulation algorithms “IDW” and “RBF”, using GIS. This resulted in the conclusion that the first algorithm is the most appropriate to formulate the equipotential curves of the selected water quality parameters. Data from two seasons (winter—frozen Lake and summer—high eutrophication level) and 2 years (2005 and 2006) are presented here so the compared periods are February 2005, July 2005, February 2006 and July 2006. The thematic maps obtained indicate the most probable sources of pollution in Lake Kastoria and present the geographic distribution of the water quality parameters using the “IDW” algorithm. The most significant drawback of monthly monitoring is the missing of the data influenced by extreme events. Therefore, the need for daily telemetric monitoring data is suggested, in order to prevent environmental hazards and confront pressures concerning on water quality status. Finally, management strategies of pollution reduction are proposed, in combination with systematic telemetric real time monitoring, in order to upgrade the natural environment of Lake Kastoria.

Raphidiopsis mediterranea Skuja represents non-heterocytous life-cycle stages of Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju in Lake Kastoria (Greece), its type locality: Evidence by morphological and phylogenetic analysis

The taxonomical relationship of Cylindrospermopsis raciborskii and Raphidiopsis mediterranea was studied by morphological and 16S rRNA gene diversity analyses of natural populations from Lake Kastoria, Greece. Samples were obtained during a bloom (23,830 trichomes mL −1) in August 2003. A high diversity of apical cell, trichome, heterocyte and akinete morphology, trichome fragmentation and reproduction was observed. Trichomes were grouped into three dominant morphotypes: the typical and the non-heterocytous morphotype of C. raciborskii and the typical morphotype of R. mediterranea. A morphometric comparison of the dominant morphotypes showed significant differences in mean values of cell and trichome sizes despite the high overlap in the range of the respective size values. Additionally, two new morphotypes representing developmental stages of the species are described while a new mode of reproduction involving a structurally distinct reproductive cell is described for the first time in planktic Nostocales. A putative life-cycle, common for C. raciborskii and R. mediterranea is proposed revealing that trichome reproduction of R. mediterranea gives rise both to R. mediterranea and C. raciborskii non-heterocytous morphotypes. The phylogenetic analysis of partial 16S rRNA gene (ca. 920 bp) of the co-existing Cylindrospermopsis and Raphidiopsis morphotypes revealed only one phylotype which showed 99.54% similarity to R. mediterranea HB2 (China) and 99.19% similarity to C. raciborskii form 1 (Australia). We propose that all morphotypes comprised stages of the life cycle of C. raciborkii whereas R. mediterranea from Lake Kastoria (its type locality) represents non-heterocytous stages of Cylindrospermopsis complex life cycle.

Food web structure and planktonic predator‐prey relationships in two eutrophic European lakes: Stability constraints on carbon fluxes

The food webs in two eutrophic European lakes were analyzed with respect to their stability characteristics. The food web during the summer in Lake Nesjøvatn (Norway) appeared to be stable; its response time to small perturbations was ~12 d. In Lake Kastoria (Greece), the summer food web was almost neutrally stable, with a response time of ~160 d. The major difference in the two systems was the species composition of the phytoplankton community, which was dominated by unicellular cryptophytes in Lake Nesjøvatn and by toxic filamentous and colonial cyanobacteria in Lake Kastoria. The macrozooplankton in both lakes showed a distinct inclination toward carnivory versus herbivory, and the heterotrophic flagellates showed a preference for small phytoplankton versus heterotrophic bacteria as a food source. The requirement for stability of the food webs constrains the grazing rates of predators to values substantially less than those that would maximize the energy flux through the system. This is especially true when a predator preferentially consumes one of several prey species.

Phytoplankton species succession in a shallow Mediterranean lake (L. Kastoria, Greece): steady-state dominance of Limnothrix redekei, Microcystis aeruginosa and Cylindrospermopsis raciborskii

The phytoplankton species composition and seasonal succession were examined in Lake Kastoria during the period November 1998–October 1999. A total of 67 species and 19 functional groups were identified. Only 4 out of the 67 species, all Cyanobacteria, were dominant (Limnothrix redekei, Microcystis aeruginosa, Cylindrospermopsis raciborskii and Aphanizomenon gracile). Diatoms were rare, not only in terms of species number, but also in terms of biomass (contributing <5% to the total phytoplankton biomass) in relation to the rather low silicon concentrations throughout the year. The functional groups S1, SN, M and H1 were found dominant in the lake. The species A. gracile (functional group H1) behaved like the species Cylindrospermopsis raciborskii (functional group SN) which is tolerant to mixing and poor light conditions. The phytoplankton seasonal succession showed similar patterns in all six sampling stations, both at the surface and the bottom water layer, with minor differences during Microcystis aeruginosa dominance. Two steady-state phases were identified within a year lasting for 4 months under relatively stable physical conditions. In these steady-states, the Limnothrix redekei persistent dominance under low light availability and low inorganic nitrogen has been explained by its specific ability such as buoyancy regulation to exploit resources in the water column. Moreover, high population densities over the winter and before the development of daphnids may contribute to the steady-state dominance of Limnothrix. Different niches separated vertically in the water column is one of the explanations for the Limnothrix–Microcystis steady-state when a replacement between the two species was observed in different water layers and areas of the lake. Long lasting steady-states of Cyanobacteria observed in Lake Kastoria and in other Mediterranean and tropical freshwaters may indicate influence of warm climate properties on phytoplankton dynamics.

ΠΕΡΑ ΑΠΟ ΤΟΥΣ ΓΥΡΕΟΚΟΚΚΟΥΣ: ΤΑ ΠΑΛΥΝΟΜΟΡΦΑ ΚΑΙ Η ΣΗΜΑΣΙΑ ΤΟΥΣ ΣΤΗΝ ΕΡΜΗΝΕΙΑ ΤΟΥ ΠΑΛΑΙΟΠΕΡΙΒΑΛΛΟΝΤΟΣ

Non-pollen palynomorphs (ΝΡΡ) are organic-walled microfossils that are frequently discovered in palynological preparations during pollen analysis. Like pollen and spores they are resistant to corrosion and they survive the chemical preparation with heavy acids of pollen samples. NPP include a big variety of microfossils like fungal spores, algal spores and coenobia, animal remains and plant tissues. They provide an alternative source of paleoecological information especially for the Quaternary. A combined approach of pollen and NNP allows the better understanding of paleoecological changes. The study of occurrences of NNP from a series of Holocene deposits in Greece (Lake Kastoria, Skyros Island, Marathon coastal plain) was proved of great importance in the interpretation of paleoenvironmental conditions and the tracing of human activities in the past.