Water parameters and species composition of macrophytes

Macrophytes and selected physical-chemical water properties were studied in 17 post-mining lakes of Jeziórko Sulphur Mine – one of the largest borehole sulphur mines in the world. Artificial lakes were constructed in subsidence depressions during the reclamation process of mining fields. They were characterized by high mineralization – conductivity ranged from 723 to 2295 μS/cm. The reaction was near neutral, or more frequently, slightly alkaline. Concentrations of phosphorus and organic matter were low. In the group of hydrophytes, Ceratophyllum demersum , Myriophyl-lum spicatum , Najas marina , Utricularia vulgaris , Eleocharis acicularis , Potamogeton pectinatus , Potamogeton natans and Potamogeton pusillus were frequently dominant. In several lakes, large macroscopic algae dominated – charophytes forming large, dense Chara meadows. In marsh com - munities, Phragmites australis was the most expansive. Reclamation process had a positive effect on diversity, some of the species found in the study area are regionally rare, including one species which is threatened in Poland ( Najas minor ). No alien species were recorded.

Słowa kluczowe: zbiorniki pokopalniane, górnictwo siarki, rekultywacja, roślinność wodna, spontaniczna sukcesja, Jeziórko, SE Polska INTRODUCTION Mining is one of the human activities which heavily transform the landscape, often on a large scale.The environmental effects of mining depend on the type of extracted deposits, the mining techniques applied and the methods of reclamation used after the mine closure.Sulphur mining using the borehole method has a relatively low environmental impact but also causes soil and ground water pollution, generates terrain depressions, changes hydrographical conditions and damages large areas of vegetation cover (9,21,23).
Anthropogenic lakes and wetlands are common elements of the post-mining landscape, and they can be formed either in mining pits or subsidence depressions.During the reclamation process they can be liquidated or managed in various ways, and sometimes contribute to the development of valuable habitats and increasing local biodiversity (3,17,26,27,28,37).Newly created post-mining lakes are usually oligo-to mesotrophic, and are frequently highly mineralized (7,26).Water bodies in coal mine fields are also characterized by low ph values and heavy metal pollution.Deep opencast lakes are meromictic due to a high concentration of mineral salt (7,36,39).
The development of biological life and ecosystem functioning in the conditions of postexploitation lakes is undoubtedly an interesting research subject.A reasonably large amount of information about the vegetation and planktonic communities of sand pits, peat excavations and quarries are scattered throughout floristic, phytosociological and ecological studies (5,7,29,30,31,34).The limnological research studies conducted in Central Europe in large mining fields of deposits such as coal, lignite or sulphur are less numerous and usually involve plankton (2) or invertebrates (11,18), however, no literature is available concerning aquatic vegetation on land degraded by sulphur borehole mining.
Lake creation was applied as a rehabilitation method in the Tarnobrzeg Sulphur Region (SE Poland), where several dozen reservoirs of various sizes were created between 1996-2013.There are detailed studies of large open-cast mine lakes from this region, concerning hydrochemical conditions (33,39), sediment composition (32), plankton (36,40), benthos (6) and fishes (8).The surface water properties of various types of water body (backwaters, ditches, rivers and artificial reservoirs) in the Jeziórko Sulphur Mine were studied by Martyn and Jońca (22).Single observations of rare entomofauna in this area have also been published (19,20).
The aim of the study was to describe the development of aquatic ecosystems in the early stages of spontaneous primary succession in the reclamation lakes of a closed sulphur borehole mine.The research included measurement of specific physical-chemical water parameters and the determination of the species composition and abundance of macrophytes.Moreover, the results of our research were used to evaluate reclamation effectiveness.

STUDy AREA
The Jeziórko mine is situated in the sub-mountain Carpathian basin in south-eastern Poland (N 50°33ʹ, E 21°48ʹ, altitude 150 m a.s.l.).It is part of a mining complex called the Tarnobrzeg Sulphur Region, where sulphur has been extracted since 1957 using both open-cast and borehole mining techniques.This complex is one of the biggest sulphur extraction areas in the world.In Jeziórko, sulphur deposits were excavated in 1967-2001 using the borehole method.This is the largest sulphur mine using this method in the world -8,450 boreholes were drilled to exploit over 74 mln tons of sulphur (23).As the result of mining works, a large area has been polluted with sulphur compounds and acidulated.Subsidence depressions have developed in mining fields, flooded by extremely acidic water.The maximum level of depressions reached 6 m (9).
To regulate hydrographical conditions during reclamation treatment, a system of surface reservoirs and connecting ditches was built.In this way, the deepest parts of depressions were transformed into artificial lakes.The oldest reservoirs were built in 1996, the youngest in 2013.finally the water was discharged into the reconstructed Żupawka stream.Reservoirs were built using indigenous materials.After lakes were formed, the acidification was neutralized with postflotation sludge containing about 70% CaCO 3 (10)

MATERIALS AND METhODS
The study was carried out in 17 reservoirs located in the former Jeziórko Sulphur Mine.Most of them are artificial water bodies built in subsidence depressions.One study site (number 17) is an old clarifier.Data concerning the morphometry and age of reservoirs were obtained in 2014 from workers of The Mines and Processing Plants of Sulphur "Siarkopol" in liquidation in Tarnobrzeg (Tab.1).
Multiparameter gauge hI 9828 was used to measure the basic physical-chemical properties of water: temperature, ph, dissolved oxygen, oxygen saturation, conductivity, TDS and salinity.Surveys were conducted in June 2014 at three points of the littoral zone for large reservoirs and two points for smaller ones.Additionally, selected chemical analyses were carried out in five lakes.The samples were taken in summer 2012 and analyzed by the Regional Environmental Protection Laboratory in Rzeszów.In this case the following methods were used: biological oxygen demand (BOD 5 ) -electrochemical method; chemical oxygen demand COD-Cr -titration; ammonia nitrogen (N-Nh 4 ), nitrate nitrogen (N-NO 2 ), dissolved phosphates and total phosphorusspectrophotometry; nitrate nitrogen (N-NO 3 ) and sulphates (-SO 4 ) -ion chromatography (IC); total nitrogen -calculation method.
Macrophytes were surveyed in summer 2014.Plants were noted during wading in shallow water (to a depth of 0.7 m) along the banks of the lakes.Plants growing in deeper water away from the banks were sampled about every 250 m of the shoreline, using grapnel.hydrophytes and typical helophytes (according to zarzycki et al. (38)) were taken into account, other species were excluded.Species abundance was estimated with the use of the qualitative Tansley scale: 1 -sporadic, 2rare, 3 -occasional, 4 -frequent, 5 -abundant, 6 -co-dominant, 7 -dominant.Charophytes were determined using the Urbaniak and Gąbka guide (35).

Water properties
The results of analyses of the basic physical-chemical parameters for each single lake were very similar at particular measuring points, except for dissolved oxygen which differed considerably in some cases.In general, the waters of the investigated lakes were characterized by high mineralization.Conductivity ranged from 723 to 2295 μS/cm, which means a salinity of 0.35 -1.18 in PSU.As expected, due to mining pollution, most of the lakes (all but three) are oligohaline.high mineralization is mostly the effect of a high concentration of sulphates (Tab.3).The examined water samples were found to be near neutral or more fre-fig.1. System of water reservoirs and ditches constructed in subsidence depressions of mining fields in Jeziórko quently slightly alkaline, the mean ph value was 7.55 (range 6.88-8.33).Lakes were well oxygenized, with saturation at the bottom range from 22.6% to 92.5% (mean 64.4%).Chemical analysis showed that the concentrations of phosphorus as well as organic matter were low and quite similar in all of the five investigated lakes (Tab.3).The concentration of nitrate nitrogen (N-NO 3 ) differed considerably, and reached relatively high values.As far as lake age is concerned, ph and amounts of dissolved oxygen are lower in older lakes.

Macrophytes
In total, 42 aquatic plants were found in post-mining lakes (Tab.4).Submergent plants were the most numerous among hydrophytes: Ceratophyllum demersum, Myriophyllum spicatum, Najas marina, Utricularia vulgaris, Eleocharis acicularis, Potamogeton pectinatus and Potamogeton pusillus were frequently dominant.from the group of aquatic plants with floating leaves, only Potamogeton natans and Polygonum amphibium fo.natans occurred frequently and developed in large patches, other species were sporadic.In several lakes charophytes were the predominant group, covering large parts of the lake bottom.four species belonging to the Chara genus were found, the most numerous were Chara vulgaris.Pleustonic plants were poorly represented and covered only a small surface area.
helophytes formed a more or less distinct belt of marsh communities.Common reed Phragmites australis was the most abundant species in the examined lakes.Cattails Typha spp.were also noted in most of the lakes, they occurred numerously, and sometimes co-dominated in phytocoenosis.Other helophytes occurred rather rarely and with small coverage.
As far as lake age is concerned, the number of species were higher in young lakes (2-7-year-old), mostly due to the increased number of submergent plants.young lakes were preferred by such species as Potamogeton pusillus, Potamogeton pectinatus, Chara contraria, Eleocharis acicularis, Myriophyllum spicatum, Najas marina, Najas minor and Alisma plantago-aquatica.In the helophyte group, a proportion shift between dominants was observed, the share of Phragmites australis increased over time, while Typha spp.decreased.
Collating the data concerning species composition and salinity level, we found no pronounced relationship between them, but some general remarks can be made.In the most highly mineralized lakes, species from the genus Chara were commonly found, especially Chara vulgaris and Ch.globularis.The highest share of charophytes was in the two lakes with the highest salinity.from the group of vascular plants, salt resistance was shown by Utricularia vulgaris, Typha latifolia, Typha angustifolia, Phragmites australis, Myriophyllum verticillatum, Myriophyllum spicatum, Lemna minor, Potamogeton natans, Potamogeton pectinatus and Schoenoplectus tabernaemontani.
No clear species preferences were observed in the case of ph value, except for Potamogeton pusillus which occurred in alkaline lakes.
The number of studied species found in individual lakes ranged from 2 to 22.The largest diversity was observed in young lakes located in the southern part of the Jeziórko mine, characterized by higher ph and lower salinity levels (lakes 12,13,15,16).

DISCUSSION
The high concentration of dissolved mineral salts that is usually observed in post-mining lakes was also confirmed in the Jeziórko mine (Tab.2).Similar conductivity to that found in anthropogenic reservoirs formed in lignite and coal mines (2,18).Much higher salinity (up to 10 g/dm 3 ) was recorded near the bottom of a flooded opencast sulphur mine (39).Elevated mineralization is also observed in sand and gravel pits (27) and quarries (7).
The current neutral or slightly alkaline character of water in the Jeziórko mine is most probably the effect of liming new reservoirs, as well as the surrounding soils.Ten years earlier Martyn and Jońca (22) recorded a much lower ph in artificial reservoirs in Jeziórko, determining a mean value of 5.2.In deep excavation of an opencast mine in the same sulphur mining region, slightly alkaline water was generated by the limestone base (39).An extremely low ph (<3) was reached by water in lignite open-pits (2), however most anthropogenic water bodies were characterized by neutral or alkaline waters.
Many examples show that a small amount of organic matter and a low concentration of nutrients, especially phosphorus, is typical of newly created anthropogenic reservoirs (2,7,27).All these studies enable us to place such lakes along the trophy gradient in the group of oligo-or mesotrophic habitats.Similar states were observed in our study in the sulphur mine.
Anthropogenic reservoirs as a common element of the post-mining landscape play an important role for biodiversity in the reclamation process.During the colonization of new lakes, species composition is determined by site conditions, dispersal ability and inter-specific interactions -the meanings of these factors change over time, and as succession progresses.Dispersal that enables plants to reach a new site is an obvious and basic element in the initial phase of vegetation development.Landscape parameters and the availability of dispersal vectors determine the species emerging and the rate of succession.Aquatic plants can easily migrate, not only from near surroundings but from long distances (13).In Jeziórko we already found a high number of macrophytes in the 2-3 years after lake creation.Submergent plants dominated, as is characteristic of young water bodies.Charophytes occurred in high abundance in young lakes, they were also found in older ones, but in water with elevated salinity.This corresponds to the well known fact that during the succession process this group is pushed off into less suitable niches.In littoral marshes three common anemochorus species of helophytes were the most numerous (Phragmites australis, Typha latifolia, Typha angustifolia); these species are able to overgrow new sites fast, using vegetative propagation.Common reed is regarded as a very strong competitor that has caused the rapid decline of other aquatic species (4,25); in Jeziórko it took the advantage in older lakes.
Comparing post-mining reservoirs in Jeziórko, which differ slightly in water parameters (especially mineralization), we found no clear reflection of these differences in species composition.But when we analyze diversity on regional scale we can reveal a dissimilarity of post-mining lakes in contrast to other aquatic habitats.Some of the species found in reclamation lakes in high abundance are rare or do not occur in other types of water bodies (old river beds, fishponds) outside the sulphur mine.According to ecological indicator values (38), among the vascular aquatic plants found in Jeziórko 62% are facultative halophytes.for comparison, in old river beds of small and medium rivers of the same region the share of halophytes was about 40% (14,15), which suggests that elevated mineralization can affect vegetation structure.
Taking into account trophy state, it can be hypothesized that nutrient-poor water does not constrain the growing of plants typical of eutrophic habitats.The species observed in the examined lakes with a low concentration of mineral phosphorus are mostly eutrophic or generalist, only a few can be regarded as mesotrophic, e.g.Eleocharis acicularis, Potamogeton trichoides, Bulboschoenus maritimus and Chara vulgaris (1,16,38).
It must be emphasized that none of the examined water parameters reached extreme values, which would certainly have caused a decrease in species richness.for example, a low diversity of phytoplankton was observed in flooded lignite open-pits with a very low ph value (2).
Probably the major effect on species composition and, most of all on diversity, is limited competition, which is typical of the non-equilibrium state of newly created or disturbed lakes.Lack of vegetation or large areas of gaps in the vegetation in the littoral zone enable it to be settled by most of the plants which reach a lake.The habitat conditions of the new lake promote pioneer species, but at the same time do not limit the establishment of strong competitors.however, the importance of interspecific interaction increases over time, and species pools are reducing as a result of competitive exclusion.In 2-7-year-old lakes we noted on average 18 species, while in 11-19-year-old ones, only 8 species.Even if we eliminate small-size lakes from our calculations, the difference is still considerable (18 for young and 11 for older lakes).One of the best examples of the positive effect of excavation on diversity is the flora of a gravel pit flooded by shallow water in french Alps (27), where an extremely high species richness of submerged macrophytes, especially charophytes, was found.In natural landscape this effect is generated by free flowing rivers and their active floodplains (newly created and periodically disturbed river lakes or temporal pools), but river regulation has caused these habitats to be largely lost.Some of the taxa (Chara spp., Potamogeton pusillus, P. trichoides, Najas marina, Bulboschoenus maritimus, Schoenoplectus tabernaemontani) seem to prefer new anthropogenic reservoirs, as they are frequently found in such habitats, while being generally rare.A good example is Potamogeton pusillus -a pioneer species colonizing newly created water bodies in the first years after excavation (5,24,25).Najas marina were found in subsidence depressions and gravel pits (18,27).Chara spp.are quite frequent in peat excavations (29).Communities with Potamogeton pusillus and Chara spp.are also typical of oil sand mine reclamation wetlands in a boreal landscape (28).In natural ecosystems, species such as Chara globularis, Potamogeton trichoides and Bulboschoenus maritimus occur more frequently or exclusively in the young river lakes of active floodplains (14).
In short, the effect of limited competition on young anthropogenic aquatic ecosystem is essential to species composition and diversity; the chemical and physical factors of new anthropogenic reservoirs are less important as long as they WATER PARAMETERS AND SPECIES COMPOSITION Of MACROPhyTES... do not reach extreme levels.Similar conclusions can be drawn from the literature review (26).
Based on the results of our study, an efficacy assessment of reclamation can be made in biological terms.In general, due to aquatic ecosystem loss, most of the native hydrophytes can be regarded as target species in reclamation.Some of the species found in the study area are regionally rare (Najas minor, Najas marina, Potamogeton pusillus, Schoenoplectus tabernaemontani, Chara virgata, Chara contraria) -from this group the first species is listed in the Polish Red Book (12).No alien species were recorded.fast colonization by a large number of indigenous aquatic species and an increase in diversity on a local and regional scale are arguments for applied treatment.It can be concluded that creating artificial lakes which are then left for spontaneous succession is the right course of action in the reclamation of sulphur mining fields.
or commercial lime.Nowadays the lakes are used for public recreation purposes, mainly for fishing.
4ab.4.Aquatic plants found in 17 reservoirs in the Jeziórko Sulphur Mine