doi:10.3723/ut.31.167 Underwater Technology, Vol. 31, No. 4, pp. 167–177, 2013 www.sut.org

Environmental properties of the water-filled Ojamo limestone quarry, southern Finland

1,2 2 1,3 1 2

Ari Ruuskanen* , Kimmo Karell , Solomon Viitasaari , Lari Järvinen and Pirkko Kekäläinen Pa per Technical 1Luksia, Adult Education Institute of Western Uusimaa, 08100 Lohja, Finland 2University of Helsinki, Tvärminne Zoological Station, 10900 Hanko, Finland 3University of Helsinki, Department of Environmental , PO Box 65, Viikinkaari, 00014 Helsinki, Finland

Abstract taken place (Ejsmont-Karabin, 1995). As a result of The present paper presents a survey of the water-filled the decomposition of organic material, anoxia and Ojamo limestone quarry, located in southern Finland and H2S formation may occur in the benthic region, abandoned c. 40 years ago. In order to estimate the bio- especially if water exchange and mixing is restricted geological state of the quarry, the geological and hydro- (Galas, 2003). graphic properties were measured, and phytoplankton and The Ojamo limestone quarry was abandoned in zoobenthos sampling was carried out by . 1965. The quarry consists of an open-pit area and a Ojamo can be considered to be mesotrophic. The zoo­ vast network of tunnels. After abandonment the benthos was lacking bivalves and insects. The Ojamo water mine slowly filled with groundwater and rainwater body had good values owing to its connection to the run-off, creating an artificial lake basin. The mine groundwater. has been submerged for more than 40 years. Dur- ing this period the aquatic flora and fauna have Keywords: quarry, limestone, SCUBA, hydrography, phyto- undergone succession. Biological properties in terms plankton, , zoobenthos of benthic fauna, phytoplankton and hydrographic measurements of this artificial lake have not been 1. Introduction studied before. The present study examines the ecological state Abandoned quarry sites are often filled with ground- of the Ojamo quarry. Hydrographic properties of water and rainwater drainage, leaving behind an the water column and biota were measured in terms artificial lake basin. These man-made lake systems of phytoplankton and zoobenthos composition, as have been studied to document species assem- well as sediment type. blages and limnological properties (Cowell, 1960; Bogaert and Dumont, 1989; Shevenell et al., 1999; Galas, 2003; S´lusarczyk, 2003). 1.1. Site description Despite their artificial origin, the quarry reser- The Ojamo limestone quarry, N60°14,375’ voirs can display similar hydrographic properties E24°02,068’ (WGS84), is part of the Uusimaa Schist known to natural lakes, such as thermal stratifica- zone, which is formed by leptitic rocks and sedimen- tion (Cowell, 1960; Whittier et al., 2002; S´lusarczyk, tary carbonites (Kähkönen, 1998). Ojamo limestone 2003). However, the geomorphology left behind by is heterogeneous, and between the limestone layers previous mining processes shows strong differences lie silica-rich layers, as well as granite and amphibo- between quarry reservoirs and natural lakes, and lite dikes. The layers are thin, as is the whole forma- ultimately affects sediment type. Before submer- tion (Parras and Tavela, 1954). The main rock type sion by water, the quarry area undergoes a succes- of the mine area is coarse-grained calcitic limestone, sion of terrestrial plants (Davis et al., 1985). This is mostly composed of calcium carbonate (CaCO3). followed by a succession of aquatic flora and fauna The mine consists of an open quarry area and and, possibly, eutrophication status after filling has closed caves. Morphometric characteristics of the open part of the quarry are shown in Table 1. Below * Contact author. E-mail address: [email protected] the open-pit part of the mine, former mining shafts

167 Ruuskanen et al. Environmental properties of the water-filled Ojamo limestone quarry, southern Finland

Table 1: The morphometric characteristics of the Ojamo quarry by terrestrial plants, such as trees and vegetation, Area 60,000m2 which formed small patches of forest. These 3–5m Length (max.) 312m tall trees are currently submerged but are still in Breadth (max.) 100m an erect position and hold foliage. The open quarry Max. depth (open part) 40m area has also been filled with aggregate, both Shore line 900m before and after being submerged. Dredging and Altitude above sea level 72m other construction work has been conducted in the area during the last 10 years also. The bottom of form a network spanning tens of kilometres in the lake is heterogenic in terms of geological mor- length altogether and reach a depth of 238m. The phology and sediment type. Primarily, the sediment shafts allow for groundwater to the open consists of solid and fragmented rocky bottom along part of the mine. The surface drainage area of the with patches of soft bottom in areas of former, more lake is small because of high relief. The open part or less decomposed, terrestrial vegetation. is divided into two semi-isolated areas by an old and light conditions of the water mine road which forms a wall reaching up to the body show seasonal variation. In winter, from depth of 0.5m (Fig 1). The Ojamo quarry site serves November to March/April, surface temperature as a training site for Finnish professional and sci- varies from 0°C to 2°C. There are, however, differ- entific diver programmes. Training takes place all ences depending on location. The rim parts of the year round. cave receive permanent ice cover, but the centre stays Before being abandoned and becoming filled with open on mild winters. This is because of an inflow water, the Ojamo mine was exposed to occupation of 4–5°C groundwater from tunnels located in the

(a) 50m (g) O2 (mg/l) 012345678910 Submerged 0 (0.5m) mine road

(h) O2 (mg/l) 1 I 0 1234 4 4,1 4,2 O 2 2 O2 (20m) 4,3 4,4 II VI (5m) 3 4,5 Depth (m) (30m) 4,6 III 4,7 4 4,8 Depth (m) T (5m) IV 4,9 N 5 5 V 5,1 0510 15 20 25 5,2 Temperature (ºC) 5,3

(b) (c) (d) (e) (f) O2 (mg/l) O2 (mg/l) O2 (mg/l) O2 (mg/l) O2 (mg/l) 012345678910 012345678910 012345678910 012345678910 012345678910 1 1 1 1 1 3 3 3 3 3 5 5 5 5 5 7 7 7 7 7 9 9 9 9 9 11 11 11 11 11 13 O 13 13 13 13 15 2 15 15 15 15 17 17 17 17 17 19 19 Depth (m) 19 19

Depth (m) 19 Depth (m) Depth (m) Depth (m) 21 Temperatur e 21 21 21 21 23 23 23 23 23 25 25 25 25 25 27 27 27 27 27 29 29 29 29 29 31 31 31 31 31 0510 15 20 25 0510 15 20 25 0510 15 20 25 0510 15 20 25 0510 15 20 25 Temperature (ºC) Temperature (ºC) Temperature (ºC) Temperature (ºC) Temperature (ºC)

Fig 1: (a) Bottom contours of the lake are shown with dashed lines, the number values in parentheses depicting the approxi- mate depth of a given area. Tunnel entrances are marked by the solid thick arrow. The graphs (b)–(h) display the levels of dissolved oxygen and temperature, and their relation to depth in 1m intervals. The line portraying the sampling location within the lake and roman numerals (I–VI) are symbols of the sampling points. Graph (h) represents a subsection of the graph (g) and illustrates the decline of dissolved oxygen in 10cm intervals to point out extreme conditions. The grey area illustrates area of submerged forest

168 Underwater Technology Vol. 31, No. 4, 2013

middle part of the quarry (Fig 1). In March to April type of sampling carried out are shown in Table 2 when the air temperature rises, the surface water and Fig 1. All the samples were collected between warms, exceeding 24°C in July. During summer, a 26 and 30 July 2010. thermal stratification occurs at the depth of 10–15m. As a result of the submerged forests, a steep vari- Below the in the deepest part of the ation in geomorphology and a heterogenic bottom quarry, water temperature remains around 5°C. type, it would have been difficult to operate effectively A Secchi depth exceeds 13m during winter the traditional surface-operated sampling devices months from December to February and starts to in most areas of the benthos. Therefore, SCUBA decrease in March to April. This is because of the diving techniques were used to collect samples for from the inorganic material which flows qualitative measuring. with the surface run-off from melting snow into the Before sampling, several dives were executed to quarry. During the summer season from May to check the bottom quality in order to choose suita- August, the Secchi depth varies between 2m and ble sampling devices. Since the bottom was muddy 4m, depending on the intensity of the phytoplank- in some locations, control was found to ton production. Fig 2 illustrates the development be imperative in maintaining the visibility and the of surface temperature and Secchi depth from bottom undisturbed. ­February to April 2010. When sampling, bottom guidelines were laid – The origin of the water in the quarry is most a method obtained from techniques – likely groundwater. The quarry has no clear inflow to orientate when carrying the sampling devices. sources. It is uncertain if there is a connection to The dives were made as buddy dives. Basic sam- Lake Lohjanjärvi, which is located above the mine plings took approximately 20 minutes each. Air was tunnel network. There are no measured data used as the gas. regarding the changes in the water level of the Usually Finnish scientific divers carry out their quarry, but visual observations indicate it is no dives using a safety rope connected between the more than a few centimetres. diver and a surface tender. This is a general safety rule. However, while diving in a submerged forest, the safety rope would be risky and was therefore 2. Materials and methods not used. In underwater sampling safety must 2.1. Sampling always come first, thus there was always a dive oper- Hydrographic, phytoplankton and zoobenthos sam- ations leader on site and a safety diver in standby pling and sediment measurements were carried where tethered dives were carried out. Depending out. The locations of the sampling points and the on the location and properties of the sampling

Date 1.2 5.2 9.2 13.2 17.2 21.2 25.2 1.3 5.3 9.3 13.3 17.3 21.3 25.3 29.3 2.4 6.4 10.4 14.4 18.4 22.4 26.4 30.4 0

2

4

6

Visibility is decreased owing to inorganic material which 8 flowed into the cave with melting snow water.

10 Depth (m) / Temperature (ºC)

Thick snow cover on the ice restricted light. 12 Secchi depth Temperature (ºC) 14

Fig 2: Development of temperature and Secchi depth in the Ojamo quarry from February 2010 to the end of April 2010

169 Ruuskanen et al. Environmental properties of the water-filled Ojamo limestone quarry, southern Finland

Table 2: Sampling points, their codes, maximum depth and sampled variables Sampled parameters Sampling point Max. depth (m) Temperature Zoobenthos Hydrography Phytoplankton I 6 x x II 24 x III 30 x x x x IV 21 x x V 20 x VI 5 x x

point, the divers entered the water from the shore, July 2010. The phytoplankton was sampled with a if possible, or from a small boat. Limnos sampler with a volume of 2L, from the During their training scientific diving students depths of 1m, 5m, 10m and 15m. The water from use an Interspiro MK II dive setup. The full face the sampler was poured through a 10mm plankton mask can be equipped with a phone connection to net and the samples were stored in glass bottles and surface, if needed. The gas planning is done in preserved in formaldehyde for the species compo- such a way that a reserve of more than 50bar is sition and the abundance analysis. A volume of always left when the divers resurface. During the 50ml of the sample from each depth was settled for present study, the divers were in the end of their 24 hours in accordance with Uthermöl (1958). The training programme of 18 months and thus rela- samples were examined using a Wild M40 inverted tively skilful in their work. microscope (100x and 400x magnifications).

2.2. Hydrographic and chlorophyll a 2.4. Zoobenthos measurements The bottom sampling was carried out at four sam- The temperature and the dissolved oxygen were pling points, located at the depths of 4m (I), 5m (VI), measured with a YSI 95 device from six locations 20m (IV) and 30m (III) (Table 2, Fig 1). Because of (I–VI) on 30 July 2010 (Table 2, Fig 1a). The meas- the artificial origin of the quarry, sediment suitable urements were carried out at 1m depth intervals for burrowing fauna could only be found in patches. from surface to the bottom. The locations of the These sampling points were chosen where the bot- five sampling points (I–V) were chosen to cover the tom type allowed both the burrowing fauna to exist longest part of the open quarry. One sampling and the core sampling to be carried out. point (VI) was located on a hydrologically isolated From each of the sampling points three replicate area of the quarry. samples were taken except from sampling point The light measurements were carried out using I where only one sample was extractable. The repli- a LiColor light measurement device at the deepest cates were chosen randomly by from sampling point (III) at midday on 30 July 2010. The an area of approximately 10m2. The samples were day was partly cloudy, but measurements were done collected using a Tvärminne sampler, except on during a cloudless period. The first measurement sampling point I where a soft sediment core tube was was 10cm above the surface, and the second 10cm used. This was done between 26 and 30 July 2010. below the surface. The next measurements were car- The Tvärminne sampler, a diver-operated cylinder- ried out at 1m intervals until the lowest possible meas- shaped zoobenthic corer (18.5cm diameter, area urement depth was reached at the depth of 27m. of 270cm2) and the core tube (7cm diameter, area Water chemistry and chlorophyll a samples were of 38.4cm2) are sampling devices designed for taken using a Limnos sampling device, at sampling quantitative sampling from sandy or soft bottom point III on 29 July 2010 at the depths of 0m, 2m, substrata (Boström et al, 1997; 2002). The diver 5m, 10m, 15m, 20m and 25m, which was the bottom. drives the cylinder into the bottom substrate to The samples from each depth were stored in 1L the depth of 20cm, after which the diver closes the and 0.2L bottles in a cool and dark storage box. upper end of the cylinder with a sliding plate or The following eight parameters were measured: a cap. (NO3+NO2)-N; NO2-N; NH4-N; PO4-P; Si; pH; In sampling point I, the bottom consisted of conductivity; and chlorophyll a. boulders of the size of approximately 1 cubic metre and there was a crack in which a diver’s hand and a 2.3. Phytoplankton core tube just fit in. On the bottom of that crack The phytoplankton sampling was carried out at the sediment type allowed sampling. The samples sampling point III (Table 2, Fig 1) at noon on 30 were sieved on the surface using a 0.5mm mesh.

170 Underwater Technology Vol. 31, No. 4, 2013

The sieved samples were stored in a 70% alcohol/ Light (µE) water for further studies. In the laboratory, 0 200 400 600 800 1,000 1,200 1,400 1,600 the species composition was identified and the 0 number of individuals were counted. 1 Secchi depth 2 2.5. Sediment measurement 3 4 10cm 10cm Sediment type was determined from each sample 5 below above after the sample was sieved through a 0.5mm mesh. 6 surface surface 7 The purpose of rough sediment measurement was 8 to make a valid comparison between the occurrence 9 of the zoobenthos in Ojamo and the natural lake 10 11 Lohjanjärvi, since there is a correlation between 12 the bottom sediment and the fauna inhabiting it 13 14

(Gray, 1974; Anderson, 2008). Depth (m) 15 16 17 3. Results 18 19 3.1. Hydrographic and chlorophyll a 20 measurements 21 22 The temperature and oxygen values are shown in 23 Fig 1a–h. Generally, in the open part of the quarry, 24 i.e. open-pit, on sampling points I–V the tempera- 25 26 ture showed parallel distribution between the sam- pling points (Fig 1a–f). The surface temperature Fig 3: Distribution of light in the sampling point was approximately 24°C. At the depth of approxi- III expressed as mE/m2/s. A dotted line mately 4m there was slight thermal stratification, illustrates Secchi depth and below the thermocline the temperature fur- ther decreased to a minimum of 5°C at the depth of 27m. Regarding the vertical distribution of dissolved measurements are shown in the summary (Table 3, oxygen, oxygen levels at the surface were approxi- Fig 4a–j). Regarding the nitrogen, there was a peak mately 9mg/L. Below 4m, the oxygen levels gradu- at the surface and at the depth of 15–20m. The ally decreased down to 4mg/L at the depth of 27m. phosphorous reached its maximum, 20.4mg–l, at the However, there were irregularities in the oxygen depth of 20m. The silicate showed an increasing curve at each sampling point, which can be seen as trend towards deeper water column, whereas pH a zigzag-like pattern. Moreover, at sampling point values were equal through the water column as was IV, oxygen decreased down to 2mg/L at the depth the conductivity. of 20m. In the isolated part of the quarry, in sam- Chlorophyll a showed its maximum value of pling point VI, near-surface temperature and oxygen 14.5mg–l at the depth of 15m. levels were equal to those of the open part. How- ever, there was a drastic decrease in oxygen levels 3.2. Phytoplankton below 4m, where anoxic conditions prevailed near Altogether 14 species of photoautotrophs were and on the bottom (Fig 1g,h). identified. The species composition is shown in The light measurement values are shown in Table 4. The most abundant taxon was Chlorophyta Fig 3. The PAR light was 1,400mE/m2/s at the alti- with a maximum abundance of 8,590 cells/L at the tude of 10cm above the surface. There was a depth of 5m (Table 5, Fig 5). decrease of 30% to the value of 800mE/m2/s in light intensity after the first 10cm below the sur- 3.3. Zoobenthos face. Below the first 10cm the light intensity Altogether seven species were found in zoobenthos decreased slowly and gradually towards the bottom. samples (Table 6). At the depth of 4m there were The only discrepancy to this was the slight increase two species, and at the depths of 20m and 30m in light intensity near the bottom at the depth of three and five species, respectively. The most com- 23m. Below 26m the light decreased close to zero mon group at all depths was Oligochaeta. The most (0.008mE/m2/s). abundant species was Turbellaria tubiflex, 429 indi- The results of the (NO3+NO2)-N, NO2-N, NH4- viduals per m2, at the depth of 4m. At sampling N, PO4-P, Si, pH, conductivity and chlorophyll a point VI, no fauna was found.

171 Ruuskanen et al. Environmental properties of the water-filled Ojamo limestone quarry, southern Finland

Table 3: Depths and values and range of measured parameters from the sampling point III Depth Chl a (NO3+NO2)-N NO2-N NH4-N PO4-P Si pH Conductivity (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mS/cm) 0m 1.2 50.0 0.5 0.2 3.4 3.5 8.47 223.0 2m 1.6 2.4 0.1 1.2 5.4 3.8 8.03 251.9 5m 7.9 2.4 0.6 1.3 6.2 5.2 8.11 246.8 10m 14.5 29.9 0.4 11.8 5.7 7.0 8.21 232.6 15m 9.2 68.0 0.8 20.0 11.9 7.5 7.73 251.1 20m 5.6 117 1.3 15.3 20.4 6.7 7.42 244.7 29m – 79.0 0.2 1.5 17.3 9.0 8.12 183.9 Range 1.2–14.5 2.4–117 0.1–1.3 0.2–20.0 3.4–20.4 3.5–9.0 7.42–8.47 183.9–251.1

Temperature (ºC) O2 (mg/L) Chl a (µg/L) (NO3+NO2)-N (µg/L) NO2-N (µg/L) 0102030 0510 01020 0 100 200 012

0m 0m 0m 0m 0m 2m 2m 2m 2m 2m 5m 5m 5m 5m 5m 10m 10m 10m 10m 10m 15m 15m 15m 15m 15m 20m 20m 20m 20m 20m 29m 29m 29m 29m 29m

NH4-N (µg/L) PO4-P (µg/L) Si (mg/L) pH Conductivity (µS/cm) 02040 02040 0510 0510 0 100 200 300

0m 0m 0m 0m 0m 2m 2m 2m 2m 2m 5m 5m 5m 5m 5m 10m 10m 10m 10m 10m 15m 15m 15m 15m 15m 20m 20m 20m 20m 20m 29m 29m 29m 29m 29m

Fig 4: Vertical distribution of temperature, dissolved oxygen, chlorophyll a, (NO3+NO2)-N, NO2-N, NH4-N, PO4-P, Si, pH and conductivity at the sampling point III. Results on temperature and dissolved oxygen are shown here in the same scale as the other parameters for comparison

3.4. Sediment measurements ral lakes in Finland. Although the surface area of The sediment type varied at each zoobenthos sam- the quarry is relatively small, it reaches the depth of pling point (Table 7). In sampling point VI located some 40m in the open quarry area and 238m in in the shallow, isolated area, the sediment was tunnels, while the average depth of Finnish lakes is mainly clay. In sampling point IV located in the for- approximately 7m. The underwater tunnel network est, the sediment was mainly non-decomposed of the quarry is connected to the regional water detritus. This sediment was most likely deposited table, which allows upwelling or water exchange to through the years when the forest was alive and the open quarry area. above the water level. The light conditions, expressed as Secchi depth, In sampling point III the sediment mainly con- are relatively good in Ojamo. During the winter the sisted of angular sand and gravel. This sampling Secchi depth exceeds 13m with a decline to 2.5m in point was located in the proximity of a mine tunnel the summer months. This is generally equal to oli- entrance and was exposed to material brought gotrophic lakes in Finland (Arst et al., 2008). Light from the tunnels. penetration is restricted efficiently by thick snow cover on ice (Arst et al., 2008); this became evident in Ojamo after a heavy snowfall in February. 4. Discussion The visibility decreases in two phases in Ojamo. The water-filled Ojamo limestone quarry is an excep- Initially, in the spring owing to the meltwater run-off tional water body in terms of geological, hydrographic containing inorganic sediments, which increases and biological properties when compared to natu- turbidity. This can be observed on an hourly scale

172 Underwater Technology Vol. 31, No. 4, 2013

Table 4: Phytoplankton taxon list Cells per litre Cyanophyta 0 2,000 4,000 6,000 8,00010,000 Microcystis reinboldii Cryptophyceae 1m Cryptomonas sp. Katablepharis sp. Cyanophyta Rhodomonas lens Cryptophyceae Dinophyceae Dinophyceae 5m Chrysophyceae Ceratium hirundinella Diatomaphyceae Chrysophyceae Prasinophyceae Pseudopedinella sp. Chlorophyta 10m Diatomaphyceae Depth interval Heterotrophic Asterionella formosa flagellates Fragilaria sp. (12um) Chlorophyta 15m c.f. Chlorella sp. Oocystis rhomboidea Spirogyra sp. Fig 5: Abundances of phytoplankton at different depths Clamydocapsa planctonica Closterium parvum expressed as cells per litre. The arrows point out the main Koliella spiculiformes group Chlorophyta at each depth Nanoflagellates <5mm unidentified nanoflagellates to run-off but have no connection to groundwater,

H2S can occur in the deeper parts of the water body (Bogaert and Dumont, 1989; Galas, 2003). Overall Table 5: Number of phytoplankton cells per litre oxygen values were fair (>2mg/L) in terms of Taxon/Depth 1m 5m 10m 15m required quantity for cellular , although Cyanophyta 28 in the isolated area of the quarry, anoxic conditions Cryptophyceae 56 150 34 66 occurred between the depths of 4.4m and 5.3m, Dinophyceae 295 25 Chrysophyceae 6 which was the bottom. However, it was not meas- Diatomaphyceae 186 234 57 ured whether H2S occurred. Prasinophyceae 2,136 Both the nitrogen and phosphorous displayed Chlorophyta 3,611 7,916 1,478 851 the highest concentration in deeper water at the Heterotrophic flagellates 22 depths of 15–20m, whereas the vertical distribution Total 3,853 8,595 3,701 1,002 of chlorophyll a and the number of Chlorophyta cells per litre, expressing phytoplankton biomass, on warm sunny days in spring. Later, when thermal reached their maximum at approximately 10m. stratification is formed, occurrence of plankton in The nitrate and phosphate values depleted above the upper water layer affects light transparency the depth of 10m suggests that the phytoplankton into the water column. are light-limited to this depth and are unable to During the day of the present study’s light condi- photosynthesise at the nutrient-rich depths of 20m. tion measurements, the Secchi depth curve showed Explanations may be found in diurnal vertical a drastic decrease during the first few centimetres migration of plankton (Bogaert and Dumont, 1989; and the light measurements displayed a 30% drop S´lusarczyk, 2003), or in autotrophic and chemotro- in light levels in the first 10cm of water. An immedi- phic microbial activity from which nitrite and ammo- ate drop of this magnitude is most likely caused by nium are signs (Žic et al., 2011). an inorganic calcite film reflecting light, since the The structure of the phytoplankton community alkalinity is highest in surface water and there is no and dominance of coccal Chlorophytes in the Ojamo strong correlation with chlorophyll a. This was fol- quarry was congruent with summertime observa- lowed by a gradual decrease in light to a depth of tions made by Cowell (1960). Peak in Chlorella sp. about 20m. Interestingly, the light showed an abundances at 1–5m reflect observations that the increasing peak at the depth of 23m. It is assumed optimal pH for the growth of the Chlorella sp. is this increase is owing to a reflection of light from a varying between values of 6.5 and 8.0 (Gehl and calcite rock outcrop near the bottom. Colman, 1985; Rachlin and Grosso, 1991). Slight thermal stratification was found at 4m depth. The trophic status of lakes is estimated using Below this, temperature decreased gradually to 4–5°C averages over the growth season, however, according at the bottom. Oxygen levels decreased gradually to the present study’s one-day observations on with increasing depth in Ojamo, exceeding the ­chlorophyll a and total nitrogen , level of groundwater. In quarries which are exposed Ojamo appears to be mesotrophic. Other quarries,

173 Ruuskanen et al. Environmental properties of the water-filled Ojamo limestone quarry, southern Finland std 21.4 21.4 21.4 21.4 106.8 12.3 12.3 12.3 12.3 98.7 148.0 Average c 0.0 0.0 37.0 37.0 37.0 b 0.0 0.0 37.0 37.0 37.0 a 0.0 0.0 0.0 0.0 222.0 30m std 21.4 20.3 37.0 74.0 12.3 24.7 37.0 Average c 0.0 37.0 74.0 b 0.0 0.0 0.0 a 37.0 37.0 37.0 20m std 150.1 1,082.5 86.7 953.3 866.7 Average c 0.0 0.0 b 0.0 520.0 a 260.0 2,080.0 4m Oligochaeta Total average Total Hydrobia sp. Mollusa Anisus vortex Trichoptera Baetis sp. Hydropsyche sp. Table 6: Abundance of zoobenthos species expressed as individuals per square metre at the depths 4m, 20m and 30m Table Sampling depth Taxon/Replicate Dero sp. unidentified Oligochaeta tubifex Tubifex

174 Underwater Technology Vol. 31, No. 4, 2013

Table 7: Sampling points, sampling depths and measured sediment types Sampling point symbol Depth Replicate Sediment characterisation I 4m a Un-decomposed detritus, minerogenic material (stones, clay) <10% III 30m a Un-decomposed detritus, minerogenic material (sand-stones) <5%, stones CaCo3, plus finer particles b Un-decomposed detritus, minerogenic material (sand-gravel) <5% c Gravelly sand, organic material (un-decomposed detritus) <5% IV 20m a Sand-stones 50%, un-decomposed detritus 50% b Un-decomposed detritus, minerogenic material (sand-stones) <20% c Un-decomposed detritus VI 5m a Clay b Clay c Clay

2,500 drainage area and anthropogenic activities such as agriculture.

2 2,000 Tubifex tubifex The water quality is also affected by the geolo­ Unidentified Oligochaeta gical constituents in contact with the water basin. 1,500 Dero sp. For example, acidity can be neutralised by calcite Baetis sp. 1,000 (Shevenell et al., 1999), which seems evident in Hydropsyche sp. Ojamo where pH is approximately 8 while the lakes Anisus vortex Individuals per m 500 in Finland are naturally more acidic (mean pH var- Hydrobia sp. ies between 5 and 7) owing to the humic acids from 0 forests and peat lands, and the bedrock-derived 4m properties of the soil. 80 In Ojamo, zoobenthos was dominated by the 70 group Oligochaeta, especially by Tubifex tubifex. 2 60 Tubifex tubifex When comparing the functional groups of zoob- 50 Unidentified Oligochaeta enthos to those of the natural Finnish lakes, the Dero sp. 40 groups of bivalves and insects were mostly absent in Baetis sp. Ojamo. In sampling point VI, which displayed 30 Hydropsyche sp. 20 Anisus vortex anoxic conditions, no macrozoobenthos was found Individuals per m 10 Hydrobia sp. at all. It is unclear if this lack is because the clay sediment was impossible for the species to occupy 0 20m or because of the anoxic conditions. In the present study the zooplankton was sam- 250 pled and identified at species level, but not counted. The most common species were Daphnia hyaline, 200 2 Tubifex tubifex Eudiaptomus sp. and Keratella cochlearis. Genus Daph- Unidentified Oligochaeta 150 nia can be found in quarries (S´lusarczyk, 2003). An Dero sp. underwater tunnel network and crystal clear water Baetis sp. 100 makes the Ojamo quarry an excellent attraction for Hydropsyche sp. cave SCUBA diving. Anisus vortex Individuals per m 50 Hydrobia sp. For the present study, the tunnels were surveyed by SCUBA diving hundreds of metres away from 0 the entrance and found the water body visibly free 30m of macroscopic flora and fauna, except that some Fig 6: Number of zoobenthos individuals found in samples at fishes, such as burbot Lota( lota), were observed to different sampling depths aggregate there. The copepods, known to be one of the most abundant types of zooplankton in ponds located in karstic natural caves (Stoch, 1997; Brancelj, however, showed signs of increasing eutrophication 2002; Pipan et al., 2006), were observed near the through time, probably owing to the lack of ground- bottom and between boulders. Overall, man-made water exchange (Ejsmont-Karabin, 1995; Galas, quarries undergo ecological succession, which may 2003; Shevenell et al., 1999). The trophic state of a lead to lower or higher diversity than natural lakes water body is affected by the size of the surrounding (Ejsmont-Karabin, 1995; Whittier et al., 2002).

175 Ruuskanen et al. Environmental properties of the water-filled Ojamo limestone quarry, southern Finland

The Ojamo quarry undergoes relatively large References annual variation in Secchi depth (visibility) and Anderson MJ. (2008). Animal-sediment relationships temperature. These factors are essential in SCUBA re-visited: Characterizing species’ distributions along an diving training. The variation in conditions and environmental gradient using canonical analysis and variety in bottom quality, from muddy open water quantile regression splines. Journal of Experimental and Ecology 366: 16–27. to cave tunnels and submerged forests, makes Arst H, Erm A, Herlevi A, Kutser T, Leppäranta M, Reinhart Ojamo an excellent location for scientific diver A and Virta J. (2008). Optical properties of boreal lake training. However, the bottom is not natural, and waters in Finland and Estonia. Boreal Environment Research succession has not reached the climax in 40 years, 13: 133–158. but is still going on. In the long term this will offer Bogaert G and Dumont HJ. (1989). Community structure and coexistence of an artificial crater lake.Hydrobiologia endless opportunities for future studies. 186/187: 167–179. The sampling was carried out during one week, Boström C and Bonsdorff E. (1997). Community structure and therefore the results reveal the environmental sit- and spatial variation of benthic invertebrates associated uation at that moment in time only. The zoobenthos with Zostera marina (L.) beds in the northern Baltic Sea. community can be considered long-lasting and rela- Journal of Sea Research 37: 153–166. Boström C, Bonsdorff E, Kangas P and Norkko A. (2002). tively stable, thus expressing the biological state of Long-term changes of a Brackish-water Eelgrass (Zostera the quarry. On the other hand, the bottom structure marina L.) Community Indicate Effects of Coastal of the quarry made it difficult or even impossible to Eutrophication. Estuarine, Coastal and Shelf 55: use traditional core sampling methods properly. 795–804. Regarding water chemistry and especially the phyto- Brancelj A. (2002). Microdistribution and high diversity of Copepoda (Crustacea) in a small cave central Slovenia. plankton, the results described the community struc- Hydrobiologia 477: 59–72. ture for the given sampling time. However, the Cowell BC. (1960). A quantitative study of the winter vertical diurnal migration and annual variation were plankton of Urschel’s quarry. The Ohio Journal of Science out of the scope of the present study. 60: 183–191. The zoobenthos shows variation over relatively Davis BNK, Lakhani KH, Brown MC and Park DG. (1985). Early seral communities in a limestone quarry: an exper- long periods of time. In the future, it may be possible imental study of treatment effect on cover and richness to measure the physical and chemical properties of vegetation. Journal of Applied Ecology 22: 473–490. through a whole year to find out annual patterns. Ejsmont-Karabin J. (1995). Rotifer occurrence in relation to Also, the zoobenthos and plankton dispersal in the age, depth and trophic state of quarry lakes. Hydrobiologia tunnels might be interesting to survey. 313/314: 21–28. Galas J. (2003). Limnological study on a lake formed in a limestone quarry (Kraków, Poland). I. Water chemistry. Polish Journal of Environmental Studies 12: 297–300. 5. Conclusions Gehl K and Colman B. (1985). Effect of external pH on the The present study concludes that Ojamo is an excep- internal pH of Chlorella saccharophila. Plant Physiology 77: tional water body, compared to the natural lakes in 917–921. Gray JS. (1974). Animal-sediment relationships. Finland. As a man-made structure, its geomorphology and Marine Biology Annual Review 12: 707–722. differs from the natural lakes. The Ojamo quarry has Kähkönen Y. (1998). Svekofenniset liuskealueet - merestä a relative high fluctuation in temperature and light peruskallioksi. In: Lehtinen M, Nurmi P and Rämö T (eds.). penetration, which is determined by both the inor- 1998: Suomen kallioperä – 3000 vuosimiljoonaa. Helsinki: ganic material from the surface run-off and the pri- Suomen Geologinen Seura, 199–227. (In Finnish.) Parras K and Tavela M. (1954). The limestone deposits in mary production of plankton. Comparing with simi- Lohja. In: Aurola E (ed.). The Mines and Quarries of lar quarries, the others showed signs of increasing ­Finland: Geological Survey of Finland. Geoteknillisiä eutrophication through time, probably owing to lack Julkaisuja 55: 67–74. of groundwater exchange. This was not the case in Pipan T, Blejec A and Brancjel A. (2006). Multivariate analysis Ojamo where oxygen-rich groundwater flows out of of copepod assemblages in epikarstic waters of some Slovenia caves. Hydrobiologia 559: 213–233. the mine tunnels. In Ojamo, zoobenthos was domi- Rachlin JW and Grosso A. (1991). The effects of pH on the nated by the group Oligochaeta. However, when com- growth of Chlorella vulgaris and its interactions with paring with the functional groups of zoobenthos in cadmium toxicity. Archives of Environmental Contamination the natural Finnish lakes, the groups of bivalves and and Toxicology 20: 505–508. insects were mostly absent in Ojamo. Shevenell L, Connors KA and Henry CD. (1999). Controls on pit lake water quality at sixteen open-pit mines in Nevada. Applied Geochemistry 14: 669–687. Acknowledgements S´lusarczyk A. (2003). Limnological study of a lake formed in limestone quarry (Kraków, Poland). I. Zooplankton The authors wish to thank the Tvärminne Zoologi- community. Polish Journal of Environmental Studies 12: cal Station for the chemical analysis. 489–493.

176 Underwater Technology Vol. 31, No. 4, 2013

Stoch F. (1997). A new genus and two new species of Whittier TR, Larsen DP, Peterson SA and Kincaid TM. (2002). Canthocamtidea (Copepoda, Harpacticoida) from caves A comparison of impoundments and natural drainage in the northern Italy. Hydrobiologia 350: 49–61. lakes in the Northeast USA. Hydrobiologia 470: 157–171. Uthermöl H. (1958). Zur Vervollkommung der quantativen Žic V, Truesdale WVW, Cuculicˇ V and Cukrov N. (2011). Phytoplankton-Methodik. Mitteilungen der Internation- Nutrient speciation and hydrography in two anchialine alen Vereinigung für teoreticshe und angewandte. caves in Croatia: tools to understand iodine speciation. Limnologie 9: 1–38. Hydrobiologia 677: 129–148.

177