{"id":37814,"date":"2026-02-13T11:07:12","date_gmt":"2026-02-13T10:07:12","guid":{"rendered":"https:\/\/www.vtei.cz\/2026\/02\/environmentalni-cile-a-limity-vodniho-prostredi-pro-raka-kamenace-2\/"},"modified":"2026-02-26T16:32:06","modified_gmt":"2026-02-26T15:32:06","slug":"environmental-objectives-and-aquatic-environment-limits-for-stone-crayfish","status":"publish","type":"post","link":"https:\/\/www.vtei.cz\/en\/2026\/02\/environmental-objectives-and-aquatic-environment-limits-for-stone-crayfish\/","title":{"rendered":"Environmental objectives and aquatic environment limits for stone crayfish"},"content":{"rendered":"

ABSTRACT<\/h2>\n

The\u00a0stone crayfish (Austropotamobius torrentium<\/em>) is a\u00a0critically endangered species listed on the\u00a0Red List of\u00a0Invertebrates of\u00a0the\u00a0Czech Republic. It is protected under Decree No. 395\/1992 Coll. and designated as a\u00a0priority species according to Council Directive 92\/43\/EEC on the\u00a0conservation of\u00a0natural habitats, wild fauna, and flora. It is generally assumed that stone crayfish requires water quality that meets at least the\u00a0emission limits for salmonid waters as defined by Government Regulation No. 71\/2003 Coll., as amended, and also by Government Regulation No. 401\/2015 Coll., as amended. Stable and abundant populations, however, require stricter environmental objectives, both in\u00a0terms of\u00a0limit values and the\u00a0range of\u00a0monitored parameters. To establish these objectives, 14 sites were selected. These sites are either unaffected or only slightly influenced by human\u00a0activities, with confirmed current occurrence of\u00a0stone crayfish or historical presence where disappearance was probably due to crayfish plague. The\u00a0sites were sampled monthly over one year. Using principal coordinate analysis (PCoA) and non-metric multidimensional scaling (NMDS), the\u00a0sites were separated in\u00a0ordination space based on the\u00a0ANC\u2084.\u2085 (Total Alkalinity) (with a\u00a0dividing criterion of\u00a0an\u00a0annual median\u00a0of\u00a02\u00a0mmol\/l) and closely correlated indicators (calcium, magnesium, conductivity). This resulted in\u00a0two groups of\u00a0sites with distinct environmental conditions. Environmental objectives were set separately for these two groups. For sites with low acid neutralization capacity (< 2\u00a0mmol\/l), stricter objectives were applied to parameters indicating pollution. For both groups, some environmental objectives are considerably stricter (e.g. annual median\u00a0BOD5 = 1.2\u00a0mg\/l) than\u00a0the\u00a0limits used for water body assessment under the\u00a0Water Framework Directive (2000\/60\/EC), depending on the\u00a0water type (1.5\u20132.5\u00a0mg\/l). Environmental objectives for some parameters are also stricter than\u00a0those in\u00a0Government Regulation No. 71\/2003 Coll., although direct comparison of\u00a0median\u00a0and C95 values is not possible. For parameters that naturally fluctuate in\u00a0aquatic environments, we consider it is important to use the\u00a0median\u00a0to assess site conditions, rather than\u00a0short-term fluctuations that are not limiting for stone crayfish (e.g., BOD5). In\u00a0contrast, minima and maxima should be applied for parameters where even a\u00a0single exceedance could be harmful (e.g., pH, toxic free ammonia) or to detect accidental pollution events.<\/p>\n

INTRODUCTION<\/h2>\n

The\u00a0stone crayfish (Austropotamobius torrentium<\/em>) is a\u00a0critically endangered species listed in\u00a0the\u00a0Red List of\u00a0Invertebrates of\u00a0the\u00a0Czech Republic\u00a0[1] and is also classified as critically endangered under Decree No. 395\/1992 Coll.\u00a0[2]. At the\u00a0level of\u00a0the\u00a0European\u00a0Union, it is protected as a\u00a0priority species listed in\u00a0Council Directive 92\/43\/EEC on the\u00a0conservation of\u00a0natural habitats and of\u00a0wild fauna and flora\u00a0[3]. To ensure its protection in\u00a0the\u00a0Czech Republic, 13 of\u00a0the\u00a0most valuable sites have been designated within\u00a0the\u00a0Natura 2000 network as Sites of\u00a0Community Importance (SCIs)\u00a0[4]. An\u00a0overview of\u00a0the\u00a0designated SCIs and their basic characteristics is presented in\u00a0Tab.\u00a01<\/em>. However, targeted monitoring has gradually identified additional sites with the\u00a0occurrence of\u00a0the\u00a0stone crayfish (by 2024, a\u00a0further 32 sites had been recorded), demonstrating that the\u00a0designation of\u00a0the\u00a0original SCIs alone is insufficient for the\u00a0effective protection of\u00a0the\u00a0species. In\u00a0order to ensure maximum protection of\u00a0the\u00a0stone crayfish at its sites of\u00a0occurrence, a\u00a0Rescue programme was approved in\u00a02024, which, among other measures, defines the\u00a0water environment conditions necessary for the\u00a0long-term survival of\u00a0the\u00a0species. Rescue programmes aimed at the\u00a0conservation of\u00a0endangered species are a\u00a0widely used tool and are being applied with increasing frequency both in\u00a0the\u00a0Czech Republic and abroad\u00a0[5]. An\u00a0important advantage of\u00a0rescue programmes is that protecting a\u00a0single target species also has a\u00a0positive effect on other species inhabiting the\u00a0same habitat, reflecting the\u00a0umbrella species concept with beneficial impacts on the\u00a0entire ecosystem\u00a0[6].<\/p>\n

Tab. 1. Overview of designated Special Areas of Conservation in the Czech Republic where the stone crayfish is listed as a species of conservation interest (source: Nature Conservation Information System Portal, NCA CR)<\/h5>\n\"\"<\/a>\n

The stone crayfish (Austropotamobius torrentium<\/em>) is among the largest invertebrates inhabiting both flowing and standing waters. Like other crayfish species, it is omnivorous and feeds on a wide range of food items. In freshwater ecosystems, it therefore plays an important role in nutrient cycling by shredding and processing organic matter, thereby making it available to other organisms [7, 8]. The stone crayfish is one of the native crayfish species in the Czech Republic; however, its original distribution range within the country cannot be precisely defined, as the gradual discovery of its occurrence continues to the present day and the original pattern of settlement can no longer be reliably reconstructed. The current distribution of the stone crayfish (Austropotamobius torrentium<\/em>) is concentrated in central, northern and western Bohemia, together with one isolated population occurring in the Krkono\u0161e foothills [9]. It inhabits slightly meandering natural streams flowing through mixed forests, where fast-flowing sections alternate with slower reaches forming pools. The stream bed is typically composed of stones or coarse-grained substrate. Its occurrence is influenced not only by the hydromorphological condition of the site and the quality of the aquatic environment [4, 10], but also by the presence of non-native crayfish species, which act as carriers of crayfish plague. The causative agent of crayfish plague is the fungus-like microscopic pathogen Aphanomyces astaci, which represents one of the most serious threats to native crayfish species. Another major threat to the stone crayfish is the loss of shelter availability, caused both by occupation by invasive species (including non-infected ones) and by insensitive modifications of watercourses, infilling of shelters with fine-grained material originating from agricultural land and fishponds, as well as sludge discharged from wastewater treatment plants. In recent years, climate change has added further pressure, particularly through\u00a0the\u00a0increasingly frequent drying of\u00a0watercourses\u00a0[11]. Additional significant negative impacts may include, for example, pesticides originating from agriculture or industrial applications, which can\u00a0enter watercourses as a\u00a0result of\u00a0improper use\u00a0[12].<\/p>\n

The\u00a0stone crayfish is an\u00a0aquatic organism that is dependent on a\u00a0high quality of\u00a0the\u00a0ecosystem as a\u00a0whole. In\u00a0the\u00a0past, it was considered a\u00a0better bioindicator of\u00a0water quality than\u00a0the\u00a0noble crayfish\u00a0[13], another of\u00a0our native crayfish species. However, recent research shows that the\u00a0water quality requirements of\u00a0both species are approximately the\u00a0same\u00a0[14]. Nevertheless, the\u00a0truth is that at sites where stable populations of\u00a0stone crayfish occur at high abundance, the\u00a0overall quality of\u00a0the\u00a0ecosystem is high, including water quality\u00a0[9].<\/p>\n

Research into the\u00a0water quality requirements of\u00a0the\u00a0stone crayfish in\u00a0the\u00a0Czech Republic began\u00a0after 2000. The\u00a0first studies focused on surveys of\u00a0known sites with occurrences of\u00a0stone crayfish, where water quality monitoring was carried out, including sites where crayfish abundance was very low and water quality poor. At some sites, longer-term monitoring was conducted, but at most of\u00a0the\u00a0other watercourses only two samples per year were taken\u00a0[15]. Data collected by the\u00a0Nature Conservation Agency of\u00a0the\u00a0Czech Republic (NCA CR) and TGM WRI within\u00a0these studies between 2006 and 2010 formed the\u00a0basis for establishing the\u00a0first threshold values of\u00a0the\u00a0aquatic environment for the\u00a0occurrence of\u00a0stone crayfish\u00a0[4, 14, 16, 17]. In\u00a0order to eliminate data representing sites unfavourable for the\u00a0longer-term persistence of\u00a0stone crayfish, sites with long-term reduced water quality, sites affected by episodic pollution incidents, and sites where data were obtained immediately before or during crayfish mortality events were excluded from the\u00a0dataset. From the\u00a0original set of\u00a0sites, 19 sites with stone crayfish were selected, for which mean\u00a0values and interquartile ranges were calculated for the\u00a0most important water quality parameters\u00a0[4, 14, 16]. The\u00a0obtained results were compared with the\u00a0applicable legislation, in\u00a0particular Government Regulation No. 71\/2003 Coll., on the\u00a0designation of\u00a0surface waters suitable for the\u00a0life and reproduction of\u00a0native fish species and other aquatic organisms and on the\u00a0detection and assessment of\u00a0the\u00a0quality status of\u00a0these waters\u00a0[18], as amended. The\u00a0calculated values were closest to the\u00a0target immission limits for salmonid waters (Tab.\u00a02<\/em>); therefore, these limits from the\u00a0government regulation were also adopted in\u00a0the\u00a0Rescue Programme for the\u00a0Stone Crayfish as binding limits. Limits for salmonid waters are also secondarily specified in\u00a0Government Regulation No. 401\/2015 Coll., on indicators and permissible values of\u00a0pollution of\u00a0surface waters and wastewater, the\u00a0requirements of\u00a0permits for the\u00a0discharge of\u00a0wastewater into surface waters and sewerage systems, and on sensitive areas\u00a0[19], as amended..<\/p>\n

Tab. 2. Immission limits set by Government Regulation No. 71\/2003 Coll. [18] and by Government Regulation No. 401\/2015 Coll. [19] for salmonid waters. When assessing according to Regulation No. 71\/2003 Coll., the 95th percentile (C95) is calculated if 12 or more values are available. If fewer data are available, the maximum value is used. When assessing according to Regulation No. 401\/2015 Coll., the annual average is calculated, except for the temperature parameter, where the maximum value is applied<\/h5>\n\"\"<\/a>\n

As subsequent research has shown, the requirements of the stone crayfish do indeed necessitate water quality that meets at least the target immission limits for salmonid waters [9, 16, 17]. However, for crayfish populations to be stable and characterised by high abundance, water quality should tend towards more stringent environmental objectives, both in terms of limit values and the range of assessed parameters. Such environmental objectives were newly defined within the TA CR Beta 2 Project No. TITSMZP701 Methodology for the assessment of the status of protected areas designated under the Water Framework Directive for the protection of habitats or species, which made use of previous extensive datasets and information from reference and other sites obtained within several TGM WRI research projects [11]. Within the TA CR Beta 2 project, these datasets were supplemented by two pilot sites (Chejlava and H\u016freck\u00fd stream), at which monitoring was conducted at monthly intervals from November 2018 to October 2019. On the basis of these data and their evaluation, environmental\u00a0<\/span>objectives were established for a\u00a0set of\u00a0indicators listed in\u00a0<\/span>Tab.\u00a03<\/em>\u00a0[20]. The\u00a0environmental objectives were defined as annual medians of\u00a012 values, or alternatively as maximum or minimum target values, depending on the\u00a0type of\u00a0indicator assessed and its relationship to the\u00a0type and character of\u00a0pollution.<\/span><\/p>\n

Tab. 3. Environmental objectives for aquatic environment quality indicators for the stone crayfish according to the methodology for assessing the conservation status of protected areas [20]<\/h5>\n\"\"<\/a>\n

Even these newly established environmental objectives, however, exhibited lower reliability, as most of\u00a0the\u00a0underlying monitoring data did not include year-round observations. Therefore, within\u00a0the\u00a0research project No.\u00a0SS02030027 Water Systems and Water Management in\u00a0the\u00a0Czech Republic under Climate Change (Water Centre), a\u00a0monitoring campaign was carried out at reference sites and the\u00a0best available sites with documented current or historical occurrence of\u00a0stone crayfish. The\u00a0data obtained formed the\u00a0basis for the\u00a0establishment of\u00a0revised environmental objectives. This article focuses on the\u00a0methodology of\u00a0data collection and evaluation, the\u00a0new setting of\u00a0environmental objectives, and their comparison with previously applied limit values.<\/p>\n

METHODOLOGY<\/h2>\n

The\u00a0refinement of\u00a0environmental objectives for water environment indicators at sites with the\u00a0occurrence of\u00a0stone crayfish was initiated by the\u00a0selection of\u00a0suitable reference sites. On the\u00a0basis of\u00a0available information on both current and historical occurrences of\u00a0stone crayfish, as well as previously measured values of\u00a0physicochemical parameters in\u00a0watercourses, appropriate monitoring profiles were identified. Within\u00a0the\u00a0Czech Republic, a\u00a0total of\u00a014 reference or slightly anthropogenically influenced sites were selected, where the\u00a0long-term occurrence of\u00a0stable populations of\u00a0stone crayfish had been confirmed or where the\u00a0disappearance of\u00a0formerly abundant crayfish populations had apparently been caused by crayfish plague rather than\u00a0by pollution or accidental contamination events. An\u00a0overview of\u00a0the\u00a0monitored sites is provided in\u00a0Tab.\u00a04<\/em> and Fig.\u00a01<\/em>.<\/p>\n

Tab. 4. Overview of reference and best available sites for the stone crayfish used for establishing new environmental objectives<\/h5>\n\"\"<\/a>\n\"\"<\/a>\n
Fig.\u00a01. Location of\u00a0sampled sites for establishing environmental objectives for the\u00a0stone crayfish. BERP \u2013 Bertinsk\u00fd stream, HRAP \u2013 Hr\u00e1deck\u00fd stream, KUBP \u2013 Kublovsk\u00fd stream,
\nLUP \u2013 Lu\u010dn\u00ed stream, MEDP \u2013 Medv\u011bd\u00ed stream, PARP \u2013 Pa\u0159ezov\u00fd stream, PMIT \u2013 M\u00edtovsk\u00fd stream tributary, PNEM \u2013 Nemanick\u00fd stream tributary, PODP \u2013 Podhr\u00e1zsk\u00fd stream, PSKO\u00a0\u2013\u00a0Sko\u0159ick\u00fd stream tributary, RADB \u2013 Radbuza river, UPOP \u2013 \u00dapo\u0159sk\u00fd stream, VALP \u2013 Valdeck\u00fd stream, ZUBR \u2013 Zub\u0159ina river<\/h6>\n

The\u00a0selected sites were monitored at monthly intervals from July 2021 to June 2022. At each site, dissolved oxygen and oxygen saturation, pH, conductivity, and water temperature were measured using a\u00a0field multiparameter probe HQ40d multi (HACH\u2011LANGE), and an\u00a0estimate of\u00a0the\u00a0current discharge was recorded. Simultaneously, a\u00a0grab water sample was collected from the\u00a0main\u00a0current for the\u00a0determination of\u00a0additional physicochemical parameters (BOD\u2085, chlorides, sulphates, ammonium nitrogen, nitrate nitrogen and nitrite nitrogen, nitrates and nitrites, phosphate phosphorus, total phosphorus and phosphates, suspended solids, acid neutralisation capacity ANC\u2084.\u2085, calcium, magnesium, iron, and the\u00a0ammonium ion). The\u00a0set of\u00a0indicators also included water environment parameters whose relationship to the\u00a0occurrence of\u00a0stone crayfish at sites had not yet been documented in\u00a0literature. These indicators (for example iron, magnesium, and sulphates) were included in\u00a0the\u00a0monitoring programme in\u00a0order to verify their potential significance. The\u00a0collected samples were cooled and transported to TGM WRI, where the\u00a0analyses were carried out in\u00a0an\u00a0accredited laboratory.<\/p>\n

The collected data were processed using the software Canoco 5. Principal coordinate analysis (PCoA) was applied, which displays samples in an ordination\u00a0space in\u00a0such a\u00a0way that similar samples are positioned close to each other, whereas dissimilar samples are more distant. For clearer visualisation, non-metric multidimensional scaling (NMDS) was also used. This method does not preserve absolute distances between objects (samples) but represents the\u00a0positions of\u00a0objects from an\u00a0n-dimensional space in\u00a0a\u00a0two-dimensional display as faithfully as possible by maintaining rank-order relationships; thus, distant objects are displayed far apart and similar objects close together. For subsequent analyses of\u00a0groups of\u00a0sites identified during testing in\u00a0Canoco\u00a05, a\u00a0two-sample t-test was applied, as the\u00a0measured data showed a\u00a0normal distribution. This test compares two independent datasets with unequal variances.<\/p>\n

The\u00a0obtained results were further compared with the\u00a0limit values specified in\u00a0Government Regulation No. 71\/2003 Coll.\u00a0[18] and Government Regulation No. 401\/2015 Coll.\u00a0[19], as well as with the\u00a0environmental objectives used for the\u00a0assessment of\u00a0general physicochemical components of\u00a0the\u00a0ecological status of\u00a0water bodies\u00a0[21] and with the\u00a0objectives applied in\u00a0the\u00a0assessment of\u00a0the\u00a0conservation features of\u00a0Natura 2000 SCIs\u00a0[20]. It is necessary to\u00a0bear in\u00a0mind that the\u00a0individual legislative frameworks use different characteristic values: in\u00a0Government Regulation No. 71\/2003 Coll., the\u00a0assessment is based predominantly on the\u00a095th percentile; in\u00a0Government Regulation No.\u00a0401\/2015\u00a0Coll., on the\u00a0annual mean; whereas the\u00a0environmental objectives for stone crayfish were established on the\u00a0basis of\u00a0the\u00a0annual median, or, where appropriate, minimum or maximum values. These methodological differences were taken into account when comparing the\u00a0results.<\/p>\n

RESULTS<\/h2>\n

The\u00a0results of\u00a0sample analyses and field measurements from all 14 sites were evaluated, and basic descriptive statistics (median, minimum, and maximum) were calculated for each parameter. The\u00a0results are summarised in\u00a0Tab.\u00a05<\/em>.<\/p>\n

Tab.\u00a05. Median\u00a0and measured minimum and maximum values for individual indicators at stone crayfish sites<\/h5>\n\"\"<\/a>\n

The\u00a0results of\u00a0the\u00a0principal coordinate analysis (PCoA, Fig.\u00a02<\/em>) and non-metric multidimensional scaling (NMDS, Fig.\u00a03<\/em>) showed that the\u00a014 assessed sites form two clearly separated clusters in\u00a0ordination space. The\u00a0PCoA explained 75.3\u00a0% of\u00a0the\u00a0total data variability (axis 1 = 50.6\u00a0%, axis 2 = 22.6\u00a0%), with the\u00a0most important environmental variables correlating with the\u00a0first and second axes at r\u00a0=\u00a00.98 and r = 0.88, respectively. The\u00a0NMDS analysis produced comparable results and explained 89\u00a0% of\u00a0the\u00a0data variability (axis 1 = 62.6\u00a0%, axis 2 = 31.4\u00a0%), with correlations between environmental variables and the\u00a0first two axes reaching r\u00a0=\u00a00.98 and r\u00a0=\u00a00.94. In\u00a0the\u00a0PCoA plot, samples with the\u00a0highest weights corresponding to the\u00a0first two axes are displayed; samples from the\u00a0Podhr\u00e1zsk\u00fd and \u00dapo\u0159sk\u00fd streams are not shown, as they project along the\u00a0third axis. Both ordination methods revealed a\u00a0consistent structure: five sites (Group 1) are separated along gradients of\u00a0ANC\u2084.\u2085, electrical conductivity and related parameters, while the\u00a0remaining nine sites form a\u00a0less compact cluster. The\u00a0vertical spread of\u00a0this group is primarily driven by the\u00a0markedly higher discharge of\u00a0the\u00a0Radbuza river compared to the\u00a0other, predominantly small watercourses.<\/p>\n\"\"<\/a>\n

Fig.\u00a02. PCoA analysis (Canoco 5) for the\u00a0assessed sites characterized by monthly values of\u00a0measured indicators, 1st and 2nd axes shown, cumulative variability explained by\u00a0the\u00a0displayed axes is 73.12\u00a0%<\/h6>\n
BERP \u2013 Bertinsk\u00fd stream, HRAP \u2013 Hr\u00e1deck\u00fd stream, KUBP \u2013 Kublovsk\u00fd stream, LUP\u00a0\u2013 Lu\u010dn\u00ed stream, MEDP \u2013 Medv\u011bd\u00ed stream, PARP \u2013 Pa\u0159ezov\u00fd stream, PMIT \u2013 M\u00edtovsk\u00fd stream tributary, PNEM \u2013 Nemanick\u00fd stream tributary, PSKO \u2013 Sko\u0159ick\u00fd stream tributary, RADB \u2013 Radbuza river, VALP \u2013 Valdeck\u00fd stream, ZUBR \u2013 Zub\u0159ina river (samples from Podhr\u00e1zsk\u00fd and \u00dapo\u0159sk\u00fd streams are not displayed because they are projected along the\u00a0third axis)<\/h6>\n
\"\"<\/a><\/h6>\n
Fig.\u00a03. NMDS analysis (Canoco 5) for the\u00a0assessed sites characterized by monthly values of\u00a0measured indicators, 1st and 2nd axes shown, cumulative variability explained by\u00a0the\u00a0displayed axes is 94\u00a0%. BERP \u2013 Bertinsk\u00fd stream, HRAP \u2013 Hr\u00e1deck\u00fd stream, KUBP\u00a0\u2013 Kublovsk\u00fd stream, LUP \u2013 Lu\u010dn\u00ed stream, MEDP \u2013 Medv\u011bd\u00ed stream,
\nPARP \u2013 Pa\u0159ezov\u00fd stream, PMIT \u2013 M\u00edtovsk\u00fd stream tributary, PNEM \u2013 Nemanick\u00fd stream tributary, PODP \u2013 Podhr\u00e1zsk\u00fd stream, PSKO \u2013 Sko\u0159ick\u00fd stream tributary,
\nRADB \u2013 Radbuza river, UPOP \u2013 \u00dapo\u0159sk\u00fd stream, VALP \u2013 Valdeck\u00fd stream, ZUBR \u2013 Zub\u0159ina river<\/h6>\n

The\u00a0analysis indicates a\u00a0division into two groups based on alkalinity (parameter ANC\u2084.\u2085) and closely correlated variables (calcium, magnesium, conductivity). As alkalinity is a\u00a0complex parameter that is only weakly influenced by human\u00a0activity and describes the\u00a0natural character of\u00a0a\u00a0site, subsequent analyses were conducted for two groups of\u00a0sites, with the\u00a0dividing criterion defined on the\u00a0basis of\u00a0the\u00a0analysed data as an\u00a0annual median\u00a0ANC\u2084.\u2085 value of\u00a02\u00a0mmol\/L (see the\u00a0clear separation of\u00a0groups in\u00a0Fig.\u00a04<\/em>). For these defined groups, statistical evaluation of\u00a0differences in\u00a0individual parameters was performed using a\u00a0two-sample t-test (comparing two independent samples with unequal variances; a\u00a0significance level of\u00a0p = 0.001 was applied). The\u00a0results of\u00a0the\u00a0testing are summarised in\u00a0Tab.\u00a06<\/em>.<\/p>\n\"\"<\/a>\n

Fig.\u00a04. Boxplot for the\u00a0ANC4.5 indicator with sites divided into groups based on PCoA and NMDS analyses; group 1 = sites with higher base ion content \u2013 ANC4.5 \u2265 2\u00a0mmol\/l, group\u00a02 = sites with lower base ion content \u2013 ANC4.5 < 2\u00a0mmol\/l<\/h6>\n
Tab. 6. Range of values measured in two groups of sites classified by base ion content, with indication of the statistically significant differences in all measured values of the respective parameter between the groups<\/h5>\n\"\"<\/a>\n

Statistically significant differences between the\u00a0groups were identified for calcium, electrical conductivity, pH, chlorides, total phosphorus, orthophosphate phosphorus, and suspended solids. For these parameters, environmental objectives related to the\u00a0stone crayfish were defined separately for each group of\u00a0sites. For the\u00a0remaining parameters (water temperature, dissolved oxygen and oxygen saturation, BOD\u2085, nitrate, ammonium and nitrite nitrogen, free ammonia, and iron), no statistically significant differences were detected at the\u00a0selected significance level of\u00a0p = 0.001; therefore, a\u00a0single environmental objective was applied uniformly to both groups of\u00a0sites.<\/p>\n

The\u00a0resulting environmental objectives, as presented in\u00a0Tab.\u00a07<\/em>, were established with regard to the\u00a0degree of\u00a0anthropogenic influence at the\u00a0sites based on the\u00a0measured parameter values. For indicators documenting the\u00a0impact of\u00a0pollution (in\u00a0particular nutrients and organic matter expressed as BOD\u2085), significantly impacted sites were excluded from the\u00a0dataset and the\u00a0objectives were derived solely from unimpacted sites. Target median\u00a0values were set according to the\u00a0calculated median\u00a0of\u00a0the\u00a0relevant dataset, with expert judgement applied to take into account mean\u00a0parameter values at individual sites and the\u00a0occurrence of\u00a0extreme values. Minimum values were defined based on the\u00a0lowest value in\u00a0the\u00a0dataset (for the\u00a0given group of\u00a0sites or for the\u00a0entire dataset), adjusted by rounding down, while maximum values were set by rounding up.<\/p>\n

Tab. 7. Environmental objectives of selected aquatic environment parameters for the stone crayfish (Austropotamobius torrentium), divided into two groups according to the ANC4.5 indicator; parameters for which a statistically significant difference between the site groups was identified are marked in blue<\/h5>\n\"\"<\/a>\n

DISCUSSION<\/h2>\n

The\u00a0newly derived environmental objectives differ from the\u00a0original objectives presented in\u00a0the\u00a0methodology for assessing the\u00a0status of\u00a0protected areas\u00a0[20] primarily in\u00a0that they are not defined uniformly for all sites, but are divided into two groups according to the\u00a0mean\u00a0ANC\u2084.\u2085 value (alkalinity), which distinguishes sites with high and low concentrations of\u00a0basic ions. Based on statistical testing of\u00a0the\u00a0data in\u00a0both groups, statistically significant differences were identified in\u00a0the\u00a0concentrations of\u00a0certain\u00a0parameters that are related both to the\u00a0natural composition of\u00a0waters and to indicators potentially associated with pollution. In\u00a0the\u00a0previous methodology, environmental objectives were established on the\u00a0basis of\u00a0a\u00a0markedly limited dataset, whereas the\u00a0new monitoring of\u00a0reference and additional sites enabled a\u00a0more robust data analysis and statistical evaluation of\u00a0the\u00a0two resulting groups.<\/p>\n

Compared with the\u00a0objectives specified in\u00a0the\u00a0above-mentioned methodology\u00a0[20], not only the\u00a0absolute target values were revised, but changes were also made to the\u00a0characteristic values, which are now newly determined as limit values. For the\u00a0parameters calcium and ANC\u2084.\u2085, the\u00a0median\u00a0value is no longer used and the\u00a0limit is defined solely as a\u00a0minimum value. The\u00a0median\u00a0is also no longer applied for pH, for which only a\u00a0range between minimum and maximum values is now specified. In\u00a0view of\u00a0the\u00a0nature of\u00a0pollution and the\u00a0risk of\u00a0the\u00a0transfer of\u00a0additional substances from agriculturally managed land, the\u00a0characteristic value used for nitrate nitrogen was also revised. The\u00a0target is now defined as a\u00a0maximum value instead of\u00a0the\u00a0previously used median\u00a0value. For this parameter, the\u00a0requirement for water quality has therefore been made more stringent, bringing it closer to the\u00a0assessment approach applied under the\u00a0so-called Nitrates Directive\u00a0[22]. In\u00a0order to protect crayfish during critical periods of\u00a0the\u00a0year characterised by high temperatures and an\u00a0increased risk of\u00a0free ammonia formation, a\u00a0target value for the\u00a0permissible maximum was newly established for this indicator, while the\u00a0median\u00a0value was retained simultaneously.<\/p>\n

In general, stricter objectives were established for sites with low acid neutralising capacity (annual median ANC\u2084.\u2085 < 2 mmol\/L) for parameters\u00a0characterising anthropogenic pollution. This applies in\u00a0particular to total phosphorus, orthophosphate phosphorus, chlorides and suspended solids. As shown by the\u00a0statistical evaluations performed, the\u00a0ANC\u2084.\u2085 indicator correlates, among other factors, with calcium concentrations in\u00a0waters. Previous studies have shown that crayfish are able to survive even under poorer environmental conditions and tolerate a\u00a0certain\u00a0level of\u00a0pollution if sufficient bioavailable calcium is present in\u00a0their environment\u00a0[4].<\/p>\n

In\u00a0the\u00a0original methodology for assessing the\u00a0status of\u00a0protected areas\u00a0[20], a\u00a0target value was also defined for total iron. At the\u00a0individual reference sites, a\u00a0wide range of\u00a0values was observed without any direct relationship being identified with the\u00a0presence or absence of\u00a0crayfish. Based on the\u00a0results obtained, we conclude that iron does not have a\u00a0direct influence on the\u00a0occurrence of\u00a0the\u00a0stone crayfish at the\u00a0sites, and therefore no environmental objective was defined for this parameter. Similarly, environmental objectives were not established for other measured parameters exhibiting a\u00a0wide range of\u00a0values (magnesium, sulphates, and the\u00a0estimated instantaneous discharge recorded at the\u00a0time of\u00a0sampling).<\/p>\n

Particular attention in\u00a0the\u00a0setting of\u00a0environmental objectives was paid to the\u00a0indicator characterising the\u00a0content of\u00a0readily biodegradable organic matter in\u00a0waters, namely BOD\u2085 values. Previous research and measurements at sites with the\u00a0occurrence of\u00a0stone crayfish indicated that target values should be very low. However, these limit values were derived from datasets that did not include complete year-round measurements but focused solely on seasonal monitoring. Analyses of\u00a0samples from reference sites carried out within\u00a0the\u00a0present study showed that the\u00a0central tendencies of\u00a0the\u00a0datasets point to the\u00a0need to increase the\u00a0environmental objective for this indicator. The\u00a0main\u00a0reason is the\u00a0overall annual dynamics of\u00a0the\u00a0BOD\u2085 indicator, which is related to the\u00a0cycling of\u00a0organic matter in\u00a0watercourses. It is necessary to recognise that, particularly during the\u00a0period of\u00a0leaf fall in\u00a0autumn, a\u00a0large accumulation of\u00a0organic matter occurs within\u00a0watercourses. Crayfish belong to the\u00a0group of\u00a0shredders and, as omnivores, play a\u00a0substantial role in\u00a0the\u00a0breakdown of\u00a0this organic matter. These fluctuations, which are most often manifested by elevated BOD\u2085 values in\u00a0autumn, were recorded in\u00a0all monitored watercourses. Certain\u00a0differences were also identified between sites with the\u00a0presence and absence of\u00a0crayfish. Whereas at sites with a\u00a0current occurrence of\u00a0stone crayfish BOD\u2085 values did not exceed 4\u00a0mg\/l, in\u00a0watercourses where crayfish had disappeared, for example as a\u00a0consequence of\u00a0crayfish plague, these values were higher, in\u00a0some cases reaching up to 10\u00a0mg\/l BOD\u2085. At sites without anthropogenic pollution, elevated BOD\u2085 values during routine monitoring were observed mostly only in\u00a0the\u00a0autumn period, when the\u00a0streambed was covered with fragmented leaf litter. Although these sites met the\u00a0newly established environmental objective for the\u00a0median\u00a0BOD\u2085 of\u00a01.2\u00a0mg\/l, the\u00a0C95 limit for biochemical oxygen demand of\u00a03\u00a0mg\/l for salmonid waters\u00a0[18] was exceeded due to the\u00a0period of\u00a0leaf fall. In\u00a0the\u00a0subsequent months, BOD\u2085 values then declined to the\u00a0usual low level.<\/p>\n

For both groups of\u00a0sites, the\u00a0original requirement of\u00a0the\u00a0methodology for the\u00a0assessment of\u00a0the\u00a0status of\u00a0protected areas\u00a0[20] concerning the\u00a0central value of\u00a0BOD\u2085 was therefore relaxed. Nevertheless, the\u00a0new value (1.2\u00a0mg\/l) remains considerably more stringent than\u00a0the\u00a0limit required under the\u00a0methodology for the\u00a0assessment of\u00a0water bodies according to the\u00a0Water Framework Directive\u00a0[21] (ranging, depending on water type, from 1.5\u00a0mg\/l to 2.5\u00a0mg\/l). The\u00a0new environmental objective values were incorporated into the\u00a0completed Rescue Programme for the\u00a0Stone Crayfish\u00a0[9] and will be applied in\u00a0the\u00a0forthcoming update of\u00a0the\u00a0methodology for the\u00a0assessment of\u00a0SCIs\u00a0[20] planned for 2026.<\/p>\n

The\u00a0importance of\u00a0the\u00a0BOD\u2085 indicator from the\u00a0perspective of\u00a0stone crayfish survival is further demonstrated by the\u00a0assessment of\u00a0water quality in\u00a0the\u00a0Z\u00e1kolansk\u00fd stream SCI. This watercourse ranks among the\u00a0most polluted streams with recorded occurrence of\u00a0stone crayfish. At the\u00a0Dobrov\u00edzsk\u00fd stream site (Dobrov\u00edz downstream) within\u00a0this SCI, high BOD\u2085 values ranging from 9\u00a0to 16\u00a0mg\/l were recorded in\u00a0six samples collected during 2023. These values exceed both the\u00a0new environmental objective for the\u00a0water environment for stone crayfish and the\u00a0limit set by Government Regulation No. 71\/2003 Coll.\u00a0[18], as well as the\u00a0limit required to achieve good ecological status of\u00a0water bodies\u00a0[21]. Although this site was designated as an\u00a0SCI for stone crayfish, in\u00a0recent years the\u00a0stone crayfish has become extinct in\u00a0this part of\u00a0the\u00a0SCI as a\u00a0result of\u00a0severe municipal pollution.<\/p>\n

For the\u00a0reasons outlined above, we consider it important, when assessing the\u00a0status of\u00a0the\u00a0water environment at sites with stone crayfish, to use the\u00a0median\u00a0value as the\u00a0primary environmental objective for pollutants such as BOD\u2085, total and phosphate phosphorus, or chlorides, rather than\u00a0evaluating short-term fluctuations in\u00a0measured values that regularly occur under natural conditions and are not limiting for the\u00a0occurrence of\u00a0stone crayfish. Minimum and maximum values (including the\u00a0C95 value used in\u00a0Government Regulation No. 71\/2003 Coll.\u00a0[18]) are important for capturing extreme conditions, for example during pollution incidents, and it is meaningful to apply them to parameters for which even a\u00a0single exceedance of\u00a0the\u00a0established limit could pose a\u00a0threat to stone crayfish (pH, nitrate nitrogen, toxic free ammonia, etc.). Ideally, therefore, the\u00a0assessment of\u00a0the\u00a0water environment at stone crayfish sites should combine evaluation against both species-specific environmental objectives and the\u00a0objectives defined for salmonid waters\u00a0[18].<\/p>\n

The\u00a0newly established environmental objectives were therefore further compared with the\u00a0target values for salmonid waters, as specified primarily in\u00a0Government Regulation No. 71\/2003 Coll.\u00a0[18] and secondarily in\u00a0Government Regulation No. 401\/2015 Coll.\u00a0[19]. When comparing individual limits from Government Regulation No. 71\/2003 Coll.\u00a0[18] with the\u00a0environmental objectives, it must be borne in\u00a0mind that the\u00a0environmental objectives are based on characteristic values derived from the\u00a0median, minimum, and maximum of\u00a012\u00a0monthly measurements, whereas the\u00a0limits for salmonid waters are based predominantly on the\u00a095th percentile when all 12 values are available, or on the\u00a0maximum when fewer values are available. Direct comparison of\u00a0the\u00a0limits is therefore not possible; nevertheless, when measured data from reference sites were compared, some parameters were found to be set at comparable levels (for example water temperature or ammonium nitrogen), whereas others were more stringent. More stringent environmental objectives were established for free ammonia (NH\u2083), which is highly toxic to aquatic organisms due to its ability to penetrate cell membranes, as well as for nitrites (NO2-) and suspended solids (NL\u2081\u2080\u2085). At sites with crayfish, suspended solids cause increased turbidity, settle on crayfish gills, and also lead to the\u00a0clogging of\u00a0suitable refuges within\u00a0the\u00a0watercourse. The\u00a0upper limit of\u00a0pH has likewise been set more strictly, since pH values above 8.5, in\u00a0combination with higher temperatures, promote the\u00a0dissociation of\u00a0NH\u2084+<\/sup> into toxic NH\u2083. At the\u00a0same time, it should be noted that, compared with Government Regulation No. 71\/2003 Coll.\u00a0[18], the\u00a0new set of\u00a0objectives for stone crayfish includes a\u00a0larger number of\u00a0parameters. The\u00a0government regulation, by contrast, additionally specifies limits for dissolved copper, total zinc, and total chlorine (as HOCl).<\/p>\n

The limits for salmonid waters, which are also secondarily listed in the table of immission limits in Government Regulation No. 401\/2015 Coll. [19], are defined as annual mean values, with the exception of the pH range and water temperature, which is specified as a maximum value. Owing to the use of annual means, however, situations may arise (in contrast to the use of the C95 value in Government Regulation No. 71\/2003 Coll. [18]) in which the established immission limits are formally met even if an accidental pollution event occurs at a site or if a source operates intermittently for only a few months per year. Nevertheless, populations of most aquatic organisms may be severely affected in such watercourses, or even decimated. Although median and mean values may appear to be relatively similar, the mean, unlike the median, is easily influenced by extreme and outlying values. Direct comparison is therefore possible\u00a0only for the\u00a0maximum water temperature limit, which is permitted to be substantially higher under Government Regulation No. 401\/2015 Coll. (29\u00a0\u00b0C), and for the\u00a0pH range, which is specified more broadly in\u00a0this regulation (5\u20139)\u00a0[19]. When median\u00a0and mean\u00a0values derived from measured data at reference sites are compared, the\u00a0immission limits set out in\u00a0this government regulation appear more permissive than\u00a0the\u00a0environmental objectives also for other parameters (BOD\u2085, suspended solids, chlorides, etc.).<\/p>\n

An\u00a0interesting perspective is also provided by a\u00a0comparison of\u00a0the\u00a0newly proposed environmental objectives with the\u00a0limits used for the\u00a0assessment of\u00a0the\u00a0ecological status of\u00a0water bodies for general physicochemical components\u00a0[21]. This methodology was developed for the\u00a0purposes of\u00a0assessing river-type water bodies in\u00a0accordance with Water Framework Directive (Directive\u00a02000\/60\/EC of\u00a0the\u00a0European\u00a0Parliament and of\u00a0the\u00a0Council of\u00a023\u00a0October 2000 establishing a\u00a0framework for Community action in\u00a0the\u00a0field of\u00a0water policy; hereinafter WFD)\u00a0[23]. One of\u00a0its objectives is to achieve at least the\u00a0second class, that is, good ecological status, in\u00a0water bodies, where the\u00a0values of\u00a0biological quality elements of\u00a0a\u00a0given type of\u00a0surface water body show a\u00a0slight level of\u00a0disturbance caused by human\u00a0activity, yet differ only slightly from those that typically occur in\u00a0this type of\u00a0water body under undisturbed conditions\u00a0[23].<\/p>\n

The\u00a0limits established for the\u00a0assessment of\u00a0water bodies under the\u00a0WFD requirements differ among individual water body types. These limits, like the\u00a0environmental objectives, are defined as medians or, where appropriate, as minimum and maximum values, which allows for direct comparison of\u00a0the\u00a0respective values. As noted above, the\u00a0WFD requires that at least good ecological status be achieved. It is therefore relevant to compare the\u00a0values of\u00a0the\u00a0environmental objectives with the\u00a0threshold separating moderate and good ecological status. Water bodies are characterised on the\u00a0basis of\u00a0river basin, altitude, geological substrate, and stream order derived by the\u00a0Strahler method\u00a0[21]. For the\u00a0purposes of\u00a0our comparison with the\u00a0environmental objectives, only altitude can\u00a0be used, as the\u00a0other characteristics (such as river basin) do not affect the\u00a0applicable limit values within\u00a0the\u00a0given altitude range.<\/p>\n

In\u00a0watercourses situated at altitudes above 800\u00a0m\u00a0a.s.l., the\u00a0threshold between moderate and good ecological status for BOD\u2085 is set at 1.5\u00a0mg\/l; for watercourses at 500\u2013800\u00a0m\u00a0a.s.l. at 1.7\u00a0mg\/l; for those at 200\u2013500\u00a0m\u00a0a.s.l. at\u00a02.2\u00a0mg\/l; and for watercourses below 200\u00a0m\u00a0a.s.l. at 2.5\u00a0mg\/l. In\u00a0all cases, these limits are less stringent than\u00a0the\u00a0environmental objective defined for stone crayfish, whose core distribution lies at mid-altitudes, that is, between 200 and 800\u00a0m\u00a0a.s.l. The\u00a0same value of\u00a01.2\u00a0mg\/l for this parameter is specified only as\u00a0the\u00a0boundary between good and very good ecological status in\u00a0watercourses above 800\u00a0m\u00a0a.s.l., that is, in\u00a0very clean\u00a0mountain\u00a0streams without anthropogenic influence. Similarly stringent is the\u00a0environmental objective set for water temperature (9.5\u00a0\u00b0C), whereas the\u00a0annual median\u00a0limit separating moderate and good status according to the\u00a0methodology for the\u00a0assessment of\u00a0water bodies\u00a0[21] is 10, 11, 12, and 13\u00a0\u00b0C for the\u00a0respective altitude categories listed above, and a\u00a0value of\u00a09\u00a0\u00b0C is specified only as the\u00a0threshold between good and very good status for watercourses above 800\u00a0m\u00a0a.s.l.<\/p>\n

Phosphate phosphorus is set more stringently in\u00a0the\u00a0environmental objectives for stone crayfish for watercourses below 500\u00a0m\u00a0a.s.l. in\u00a0both groups of\u00a0sites defined by base ion content; at higher altitudes, the\u00a0limit is already comparable. The\u00a0environmental objective for ammonium nitrogen is more stringent across all altitude categories. A\u00a0stricter maximum value is also defined for nitrate nitrogen (3\u00a0mg\/l) for watercourses up to 800\u00a0m\u00a0a.s.l. (under the\u00a0WFD-based assessment, 4.6\u00a0mg\/l applies for altitudes of\u00a0500\u2013800\u00a0m\u00a0a.s.l. and 5.6\u00a0mg\/l below 500\u00a0m\u00a0a.s.l.). In\u00a0the\u00a0altitude category above 800\u00a0m\u00a0a.s.l., assessment according to the\u00a0methodology for the\u00a0evaluation of\u00a0water bodies\u00a0[21] is more stringent for this parameter, with a\u00a0value of\u00a01.4\u00a0mg\/l. Furthermore, the\u00a0environmental objective for the\u00a0maximum oxygen saturation (105\u00a0%) is set more strictly, whereas the\u00a0threshold between moderate and good ecological status is 125\u00a0%\u00a0for watercourses below 500\u00a0m\u00a0a.s.l. and 120\u00a0% for watercourses between 500 and 800\u00a0m\u00a0a.s.l. For the\u00a0remaining parameters, the\u00a0values of\u00a0the\u00a0environmental objectives and the\u00a0limits under the\u00a0WFD are set at broadly comparable levels.<\/p>\n

CONCLUSION<\/h2>\n

At 14 reference and best available sites suitable for the\u00a0occurrence of\u00a0stone crayfish, year-round monitoring of\u00a0physicochemical water quality indicators was carried out and the\u00a0resulting data were statistically evaluated. The\u00a0evaluation revealed that sites suitable for stone crayfish can\u00a0be divided into two types according to natural conditions, with the\u00a0separating parameter being alkalinity expressed as a\u00a0median\u00a0ANC\u2084.\u2085 value of\u00a02\u00a0mmol\/l. Based on the\u00a0statistical assessment of\u00a0sites within\u00a0these two groups, indicators that differ significantly were identified, for which different environmental objectives can\u00a0be used. At\u00a0the\u00a0same time, the\u00a0remaining indicators were identified for which environmental objectives were set identically for both groups. More stringent requirements for the\u00a0state of\u00a0the\u00a0water environment for stone crayfish were established for the\u00a0group of\u00a0sites with a\u00a0low content of\u00a0base ions.<\/p>\n

From the\u00a0perspective of\u00a0water environment quality, the\u00a0stone crayfish can\u00a0be considered an\u00a0umbrella species only for certain\u00a0parameters. The\u00a0BOD\u2085 parameter can\u00a0be described as strictly limited, as it corresponds to the\u00a0upper limit of\u00a0the\u00a0oligosaprobic level\u00a0[24, 25] and is defined much more strictly than\u00a0the\u00a0limit established for achieving good ecological status for the\u00a0relevant type of\u00a0water body under the\u00a0WFD. From the\u00a0perspective of\u00a0maximum measured values, however, the\u00a0C95 value for salmonid waters under Government Regulation No. 71\/2003 Coll. is also set relatively strictly; this value was exceeded at some of\u00a0the\u00a0monitored reference sites due to elevated BOD\u2085 values during the\u00a0period of\u00a0leaf fall. In\u00a0many cases, these were sites where the\u00a0presence of\u00a0a\u00a0stone crayfish population was not confirmed during the\u00a0sampling period. In\u00a0comparison with the\u00a0limits under the\u00a0WFD, parameters indicating thermal and oxygen conditions, as well as parameters assessing nutrient conditions in\u00a0the\u00a0watercourse, are also limited more stringently. In\u00a0comparison with the\u00a0limits for salmonid waters, the\u00a0environmental objectives are more stringent for free ammonia, nitrites, and suspended solids. Direct comparison, however, is possible only with the\u00a0limits under the\u00a0WFD, where, as in\u00a0the\u00a0case of\u00a0the\u00a0environmental objectives, characteristic values are defined as medians or, where appropriate, as minimum and maximum values. Comparison with Government Regulation No. 71\/2003 Coll. and Government Regulation No. 401\/2015 Coll., which are based on C95 values and annual means, was therefore carried out using data from the\u00a0measured reference sites.<\/p>\n

Acknowledgements<\/h3>\n

This article was written with the\u00a0support of\u00a0projects of\u00a0the\u00a0Technology Agency of\u00a0the\u00a0Czech Republic No. TITSMZP701 Methodology for Assessing the\u00a0Condition of\u00a0Protected Areas Designated under the\u00a0Water Framework Directive for the\u00a0Protection of\u00a0Habitats or Species and No. SS02030027 Water Systems and Water Management in\u00a0the\u00a0Czech Republic under Climate Change Conditions (Water\u00a0Centre).<\/em><\/p>\n

The\u00a0Czech version of\u00a0this article was peer-reviewed, the\u00a0English version was translated from the\u00a0Czech original by Environmental Translation Ltd.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

The stone crayfish (Austropotamobius torrentium) is a critically endangered species listed on the Red List of Invertebrates of the Czech Repub-lic. It is protected under Decree No. 395\/1992 Coll. and designated as a priority species according to Council Directive 92\/43\/EEC on the conservation of natural habitats, wild fauna, and flora. It is generally assumed that stone crayfish requires water quality that meets at least the emission limits for salmonid waters as defined by Government Regulation No. 71\/2003 Coll., as amended, and also by Government Regula-tion No. 401\/2015 Coll., as amended. Stable and abundant populations, however, require stricter environmental objectives, both in terms of limit values and the range of monitored parameters. To establish these objectives, 14 sites were selected. These sites are either unaffected or only slightly influenced by human activities, with confirmed current occurrence of stone crayfish or historical presence where disappearance was probably due to crayfish plague. <\/p>\n","protected":false},"author":8,"featured_media":37812,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[2,86,87],"tags":[4026,4027,3724,301],"coauthors":[2529,403,4008,406],"class_list":["post-37814","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-from-the-world-of-water-management","category-hydraulics-hydrology-and-hydrogeology","category-hydrochemistry-radioecology-microbiology","tag-environmental-objectives","tag-pollution-limits-for-salmonid-waters","tag-stone-crayfish","tag-water-quality"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/37814","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/comments?post=37814"}],"version-history":[{"count":6,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/37814\/revisions"}],"predecessor-version":[{"id":38035,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/37814\/revisions\/38035"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media\/37812"}],"wp:attachment":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media?parent=37814"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/categories?post=37814"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/tags?post=37814"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/coauthors?post=37814"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}