Late Quaternary Chrysophycean stomatocysts in a ...

Phytotaxa 170 (3): 169–186 www.mapress.com/phytotaxa/ Copyright © 2014 Magnolia Press

Article

ISSN 1179-3155 (print edition)

PHYTOTAXA

ISSN 1179-3163 (online edition)

http://dx.doi.org/10.11646/phytotaxa.170.3.3

Late Quaternary Chrysophycean stomatocysts in a Southern Carpathian mountain lake, including the description of new forms (Romania) ÉVA SORÓCZKI˗PINTÉR1, SERGI PLA˗RABES2,3, ENIKŐ KATALIN MAGYARI4 CSILLA STENGER-KOVÁCS1 & KRISZTINA BUCZKÓ5* Department of Limnology, University of Pannonia, Egyetem u. 10. H˗8200 Veszprém, Hungary CREAF, (Centre for Research on Ecology and Forstry Appilcations) Cerdanyola del Valles, 08193 Catalonia, Spain 3 CSIC-CEAB, Biogeodynamics and Biodiversity group, Acces Cala St Francesc 14, 17300 Blanes, Catalonia, Spain 4 MTA-MTM-ELTE Research group for Paleontology, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary 5 Department of Botany, Hungarian Natural History Museum, Könyves Kálmán krt. 40. H-1476 Budapest, Hungary ([email protected]) *author for correspondence 1 2

Abstract In this study we present results of a low-resolution chrysophyte stomatocyst analysis that followed a high-resolution diatom analysis of a mountain lake sediment sequence from the Retezat Mountains, in the south Carpathians (Romania). The stomatocyst assemblages of the previously distinguished ten diatom assemblage zones of Lake Gales were studied with the aim to describe stomatocyst composition and create a taxonomical basis for detailed stratigraphical analysis in the future. We report 83 stomatocyst forms, and 7 of them are formally described here as new for science. An abrupt shift in cyst as well as diatom assemblages were recorded around 9200 cal yr BP during the 15,000 years long history of the Lake Gales. This Lake Gales event could be linked to the 9.3-ka widespread significant climatic anomaly, which was triggered by a melt water pulse into the North Atlantic. Key words: Chrysophycean stomatocysts, climatic anomaly, diatoms, new morphotypes, 9.3 event, Retezat Mountains, Southern Carpathians

Introduction Chrysophytes are a diverse group of freshwater algae consisting of over 1000 described species (Duff et al. 1995). All chrysophytes are believed to produce siliceous resting stages, which are often well preserved and abundant in the sediments of most lakes. These resting stages are also known as stomatocysts or simply cysts. The number of described morphotypes is over 800 according to our overview of the available literature and database (see the list of References). Cysts are more resistant to dissolution than chrysophyte scales and spines, preserve well in sediments; they have high paleolimnological potential in environmental reconstruction (e.g. Duff et al. 1995, Vorobyova et al. 1996, Kamenik et al. 2001, Pla 2001, Wilkinson et al. 2001, Kamenik & Schmidt 2005a, Pla & Catalan 2005, Huber et al. 2009). Stomatocyst assemblages provide a sensitive biotic proxy of pH and salinity (Facher & Schmidt 1996, Pla et al. 2003, Pla & Anderson 2005), and particularly they have been used to reconstruct cold-season climate variability (e.g. Huber et al. 2009, de Jong & Kamenik 2011, Pla-Rabes & Catalan 2011, de Jong et al. 2013). Most biological proxies (e.g. chironomids, plant macrofossils, pollen) are biased towards the growing season (e.g. Tóth et al. 2012; Magyari et al. 2012, 2013), while chrysophycean stomatocysts are proven to be a useful and unique proxy for assessing the ice cover changes, lake mixing (Kamenik & Schmidt 2005a) and seasonality that is linked to lake stratification patterns (PlaRabes & Catalan 2011). The greatest drawback in paleolimnological studies has been the lack of taxonomic certainty, since for most cysts neither the taxonomic affinity nor the degree of structural variation has been known (e.g. Wilkinson & Smol 1998). From the middle of 1980s intensive studies have been conducted focusing on discovery and detailed description of chrysophycean cyst floras of Arctic and Subantarctic lakes (Duff et al. 1995, van de Vijver & Beyens 1997a, 1997b, Pla & Anderson, 2005) and mountain regions (e.g. Facher & Schmidt 1996, Pla 2001, Cabała & Piatek 2004, Cabała Accepted by Patrick Kociolek: 22 Apr. 2014; published: 26 May 2014

169

2005, Huber et al. 2009, Kamenik 2010), as well as of large lowland lakes (Vorobyova et al. 1996, Firsova et al. 2012). In order to assemble already published information on stomatocyst types, Kamenik (2010) established an internet platform (www.stomatocysts.unibe.ch/wiki/home). In spite of these efforts, the knowledge on geographical distribution and biostratigraphy of stomatocysts has generally remained poor; there are several regions all over the world without any data about cysts. Even though data on cysts is strikingly low, the study of Chrysophyte taxonomy is well advanced in Romania (e.g. Péterfi 1967, Cărăuş 2012). We failed to find any published data of stomatocysts from the Eastern and Southern Carpathians; only scientific-popular papers drew attention to the diverse Holocene cyst flora of Lake Saint Anna in the Eastern Carpathians, (Buczkó 2004, Buczkó & Magyari 2006). A multi-proxy study of mountain lake deposits from the Retezat Mountains (Southern Carpathians) started in 2007 using paleolimnological and paleoecological methods. Four lakes (Lake Brazi, Lake Gales, Lake Lia and Lake Bucura) were chosen for study. Sediment cores were obtained in 2007 and 2008. These sediment sequences provided information on climatic and a biotic changes for the last ca. 15,000 years, and several high-resolution studies were published, but there were conducted mainly on Lake Brazi (e.g. Buczkó et al. 2009, 2012, 2013; Magyari et al. 2009, 2012, 2013, Korponai et al. 2011, Tóth et al. 2012, Braun et al. 2013). Lake Gales is the second lake of the same multi-proxy study project using palaeoecological methods. Up to now, vegetation responses to rapid warming and cooling events during the late glacial and early Holocene have been published on the basis of high-resolution pollen, conifer stomata and plant macrofossil analyses from Lake Gales (Magyari et al. 2012). Moreover, a high-resolution diatom analysis has already been available (Soróczki-Pintér et al. 2012). The most remarkable shift in the diatom profile was found around 9200 cal yr BP suggesting short-term lake level increase and cooling (Soróczki-Pintér et al. 2013). Stomatocyst analysis of the same deposit has been added as a new proxy with an aim to refine the climate reconstruction for the cold season in this deep lake. The objectives of this paper are (a) to document the cyst morphotypes observed in the sediment of Lake Gales; (b) to propose and formally describe new morphotypes from this lake; (c) to present a low resolution record of cysts; (d) to compare the cysts and diatom assemblages; (e) to check floristic and relative abundance changes in the cyst flora around 9200 cal yr BP, when the diatom assemblages showed remarkable and abrupt change. The most important aim of this preliminary work is to create the suitable taxonomical basis for further detailed (high-resolution) stratigraphical stomatocyst analysis in the glacial lakes of the Retezat Mountains.

Material and Methods Study site The Retezat Mountains (Munţii Retezat) are located in the western part of the Southern Carpathians (“Transylvanian Alps”). It is one of the largest sized and highest massifs in Romania. The highest peak is Peleaga (Vârful Peleaga, 2509 m. a.s.l.). The mountain has a versatile alpine and subalpine landscape with alpine meadows, plateaus, rocky ridges, cirque valleys and numerous mountain lakes. Most of them are situated at elevations between 1900 and 2200 m a.s.l. in the cirque valleys. Fifty-eight permanent and forty temporary glacial lakes are known. The climate is typically alpine: the mean annual temperature in the subalpine belt is 6 °C, while at the peaks ˗2 °C. The coldest month is January (under ˗10°C mean temperature), while the warmest month is June (around 6 °C mean temperature) at the peaks of the mountains. In addition, this is the wettest part of the Eastern and Southern Carpathians, with the highest amount of rainfall in June and the lowest in October (Jancsik 2007). The mountain comprises granite and granodiorite blocks, which are embedded in crystal slates (Jancsik 2007). Lake Gales (Lacul Galeş) (45°23’6”N, 22°54’33”E 3.68 ha; 2040 m a.s.l.; max. 20 m water depth) is situated in the alpine belt on the northern slopes ca. 150 m above the upper tree limit. Methods The sediment core from Lake Gales was obtained with a modified Kullenberger piston corer (Kullenberg 1947) (diameter 7 cm) in the deepest part of the lake at a water depth of 19.5 m in August 2007. The 328 cm sediment core was taken in one drive and was stored at 2oC until further treatment. For siliceous algae analyses samples were taken from every 4 cm. A chronological framework of sediments Gales-3 was established using 9 AMS 14C age determinations: on four terrestrial plant macrofossils and five Cladocera remains (mainly eggs) were analyzed. Four tie-points obtained by comparing the pollen spectra of Gales-3 with Lake Brazi (TDB-1) were also used for age-depth modelling in Late Glacial (for details see Magyari et al. 2012). The results of the radiocarbon dating, sediment stratigraphy, organic content measurements (LOI), sediment accumulation rates (SAR) in Lake Gales were described in Magyari et al. (2009, 2012). 170 • Phytotaxa 170 (3) © 2014 Magnolia Press

SORÓCZKI-PINTÉR et al.

The digestion of siliceous algae (chrysophycean cysts and diatoms) followed standard methods (Battarbee 1986). After the acid digestion by HCl and H2O2, the aliquot suspensions were evaporated and embedded in Zrax (R.I=1.7) or Pleurax (R.I=1.73). For light microscope analyses (LM) Leica DM LB2 with 100 HCX PLAN APO equipped with Fujifilm Digital Camera FinePix S2 Pro later VSI-3 OM(H) digital camera were used. For scanning microscope analysis (SEM) cleaned material was allowed to air-dry on aluminum stubs and was sputter-coated with gold-palladium using a XC7620 Mini Sputter Coater for 120 seconds at 16 mA. SEM analyses were performed with a Hitachi S-2600N scanning electron microscope operated at 20 kV and 3–8 mm working distance. Stomatocysts were classified after Duff et al. (1995), Facher & Schmidt (1996), Wilkinson et al. (2001) and Pla (2001). We also used the Stomatocyst database (Kamenik 2010) for identification. On the basis of high-resolution diatom analysis ten diatom zones were distinguished (Soróczki-Pintér et al. 2012). In every diatom zone pictures of a minimum of 300 cysts were taken. A minimum of 200 cysts were counted on each slide along parallel transects under LM, and micrographs were routinely taken to ensure taxonomic consistency and accuracy. The aim of this method was to create a photo database to facilitate the comparison with other lakes and other sediments. A “C” prefix was added for stomatocysts referring to the “Carpathians”. New cysts were described following the International Statospore Working Group (ISWG) guidelines (Cronberg & Sandgren 1986), but only when 3 or more specimens were observed under SEM. The exact number of studied specimens is given in brackets after the cyst name. These new cysts are enumerated from ”500”, and their code starts with ‘‘C’’ (e.g. C500). A suffix (e.g. C057B) means that the cyst could be a variety of a cyst morphotype previously described.

Results The chrysophycean stomatocyst flora of Lake Gales In this preliminary study a total of 83 stomatocysts morphotypes were distinguished in the sediment core samples of Lake Gales. Two morphotypes were only observed under LM, while the other 81 stomatocysts were detected by both microscope techniques. Seventy-one types were regarded to be identical with previously published forms, and if there was a slight difference we added a remark (Table 1). Although 12 morphotypes could be new morphotypes, only seven (C500–C506) of them were considered to be new unambiguously. Five unknown types were recognized, but only one specimen was documented, which is insufficient for formal description. On the basis of the morphological features (cyst including collar and pore shape, size, their ratio, and the ornamentation of cyst wall), seven stomatocysts have been described as new (Figs 1–19). All new cyst morphotypes belong to the group of ornamented stomatocysts with collar. The biological affinities of all new cysts are unknown. The following types are proposed as new ones: Stomatocyst C500 Soróczki-Pintér, Buczkó & Pla (9) Fig. 1. SEM description: This is a spherical to slightly oblate stomatocyst (diameter 5.6–7.4 µm) with abruptly narrowing cylindrical collar (diameter 0.7–1.2 µm; height: 0.7–1.1 µm). The pore can not to be observed. The apex of the collar (width 0.1 µm) is acute; the diameter of the inner margin is 0.4˗0.6 µm. The collar : cyst diameter ratio is ca. 0.15. The posterior hemisphere ornamented splayed projecting element. The morphology of projecting element is unique; splays to the end (width at the base 0.6–1.0 µm) and flared, undulated at the end (maximum width at the end: 2.2 µm; height of element always > 1.3 µm). LM description: The abrupt, cylindrical collar shape and the frippery-like projecting elements are characteristic to this cyst (Figs 8–9), that well visible in LM. Photography file number: Gales16cm4 Locality : Lake Gales, core Gales-3, 16 cm sediment depth References: No similar form is known. Occurrence: This stomatocyst occurred regularly in the sediment, but was more abundant in the upper part of the core (16–140 cm).

Chrysophyten cysts in Retezat Mountain

Phytotaxa 170 (3) © 2014 Magnolia Press • 171

Stomatocyst C501 Soróczki-Pintér, Buczkó & Pla (3) Fig. 2. SEM description: This is an irregular spherical stomatocyst (diameter 10.2–14.3 µm) with a large, obconical collar (diameter at the apex 4.8˗5.2 µm; at the base 3.6˗5.6 µm; collar height 4.0–4.1 µm). The acute collar apex has wavy, thin margin. The collar base is ornamented with strong, parallel struts (struts diameter basal 0.6˗1.1 µm; height 1.0˗2.0 µm; apex diameter 0.25 µm; distance of struts 0.3˗0.6 µm). The smooth surface of the cyst is ornamented with irregularly oriented lunate and wavy ridges (length always max. 2.9 µm, height 0.4˗0.9 µm). The wavy ridges may be interlock to each other. The pattern of surface is various: in the equatorial zone the wavy ridges may frame a circular depression (diameter 0.6˗1.0 µm). Mostly around the poles there are mainly single lunate ridges. LM description: This cyst can be recognized by the large, obconical collar appearing as a thorn˗like projection. Comprising many ridges, the cyst wall is thick and cyst surface can be rough (Figs 10–11). Photography file number: gales16cm8 Locality: Lake Gales at sediment depth 16 cm of core Gales-3 References: This morphotype is similar to Stomatocyst No. 85 Facher & Schmidt (1996), but Stomatocyst No. 85 has higher collar and fine struts on the posterior pole, and it has no ridges on cyst surface. Occurrence: This form is present throughout the core, but rare. Stomatocyst C502 Buczkó & Pla (4) Fig. 3. SEM description: Spherical stomatocyst (diameter 6.8–8.2 μm) with a smooth surface. The collar is cylindrical, very low (< 0.2 μm), wide, (1.8–2.5 μm in diameter). The collar surrounds a small regular pore (diameter 0.3–0.4 μm). The inner margin of this collar slopes down to the pore. Four to eight thick, echinate spines (basal diameter ca. 0.5 μm; length 6–10 μm) are located on the posterior half of the stomatocyst. LM description: The wide collar and long spines are well visible in LM (Figs 12–13). Photography file number: gales172cm002 Locality: Lake Gales at sediment depth of 172 cm of core Gales-3 References: This morphotype resemble to Stomatocyst 331 Wilkinson & Smol 1998, but C502 has a wider collar and its spines are very long and no twist. Occurrence: The presence of this stomatocyst type was documented at 8, 60, 120 and 172 cm by SEM; in LM it was found at 168 and 180 cm. Stomatocyst C503 Buczkó & Pla (5) Fig. 4. SEM description: This is a large, spherical stomatocyst (diameter 11.8–15.0 μm) with a narrow, low, cylindrical to conical collar with a thickened apex (diameter 1.6–2.2 μm; heigth ca. 0.4 μm; collar diameter : cyst diameter ratio 0.1–0.12). The cyst surface is smooth, ornamented by two to three depressions (diameter 0.6–0.8 μm) on the anterior hemisphere. The depressions have small, slightly thickened apex. LM description: The dimension and the 2–3 dots on the cyst surface help in the LM identification (Figs 14–15). Photography file number: gales268cm001 Locality: Lake Gales at 268 cm of core Gales-3. References: This morphotype may resemble to Stomatocyst 62 Duff & Smol 1991, but this cyst is smaller. The depressions in LM can be confused with the broken spines of # 62 in LM. C503 similar to Stomatocyst 103, Duff & Smol emend. Brown & Smol in Brown et al. (1997), but its depressions are less and smaller. Occurrence: This form was found only at 268 cm in core Gales-3, but here it obtained ca. 20% in relative abundance of stomatocysts. Stomatocyst C504 Buczkó & Pla (10) Fig. 5. SEM description: Large, spherical stomatocyst (diameter 9.6–11.0 μm) with a smooth or psilate surface. The collar is abruptly cylindrical, narrow and high, but often broken. The highest, but broken collar height is 2 μm, The basal diameter is 2.0–2.4 μm. The pore is simple, 1.4–1.6 μm in diameter. The ornamentation constrain to the anterior hemisphere of the cyst, close to the collar. Four to ten irregular, small, sometimes hooked spines; the basal diameter is 0.6–1,0 μm, height < 2 μm—surround the collar region. 172 • Phytotaxa 170 (3) © 2014 Magnolia Press


LM description: The cylindrical collar is surrounded by projections, which is well visible in LM. (Fig. 16.). Photography file number: gales236cm003 Locality: Lake Gales at sediment depth 236 cm of core Gales-3 References: No similar form is known. Occurrence: This stomatocyst was found only at 236 cm in Lake Gales, where it is not rare.

Figures 1–19 Scanning electron and light microscope pictures of new morphotypes were found in Lake Gales sediment core (Gales–3) Figs 1–7 Scanning electron microscope Figs 8–19. Light microscope Figs 1, 8–9 C500; Figs 2, 10–11 C501; Figs 3, 12–13 C502; Figs 4, 14–15 C503; Figs 5, 16 C504; Figs 6, 17–18 C505; Figs 7, 19 C506. Scale bar is 10 µm in LM pictures.



Stomatocyst C505 Buczkó & Pla (4) Fig. 6. SEM description: Spherical stomatocyst (diameter 9.5–11.0 μm) with a smooth surface. The collar is abruptly cylindrical, slightly obconical with a thickened, ring-like apex; its basal diameter is 2.8–3.0 μm. The collar height is 1.2–2.0 μm. The pore is regular and simple, 1.0–1.4 μm in diameter. There are three-four long, strong, attenuating, tube-like spines (diameter 1.0–1.2 μm; their height is up to 10 μm) on the posterior hemisphere of the cyst. LM description: This stomatocyst can be easily recognized by its long attenuating spines (Figs 17–18). Photography file number: SEM: Gales168cm016 Locality: Lake Gales at sediment depth 168 cm of core Gales-3 References: This stomatocyst is similar to S355 Pla, but the collar is different, S355 has a cylindrical narrow collar and longer spines. Occurrence: This stomatocyst is present at 60 and 168 cm, where it is not rare. Stomatocyst C506 Soróczki-Pintér, Buczkó & Pla (4) Fig. 7. SEM description: This is a spherical stomatocyst (diameter 5.5–6.6 µm) with regular pore (diameter 0.3˗0.4 µm). The pore is surrounded by a low conical/cylindrical collar (diameter 0.7˗0.9 µm) with a slightly ring˗like apex (max. width 0.1˗0.2 µm). The collar:cyst diameter ratio is 0.13˗0.14. The whole surface of the cyst is ornamented with lacunae˗like indentation (width 0.5˗0.8 µm) scattering irregularly and in different range. The pore is surrounded by coherent lacunae. This indentation could appear as a ring˗like structure as a particular structure consisting of elongated fossae (max. length 1.7 µm; width 1.1 µm; depth ca. 0.1 µm). LM description: The rough surface and the depression of this stomatocyst well visible in LM (Fig. 19.), while the pore is small, dot-like. The combination of features enable to identification of this new morphotype. Photography file number: Gales16cm004 References: We have not found any similar cyst forms. Locality: Lake Gales at sediment depth 16 cm of core Gales-3. Occurrence: This stomatocyst type was found at 16 and 20 cm core depth, but in these layers it is not rare. Stomatocysts assemblages in Lake Gales Siliceous microfossils were scarce and partly degraded in the sediment below 208 cm. SEM analysis revealed partial dissolution in some of these samples indicated by degradation of delicate features, such as small spines and narrow ridges. However, as even the most lightly silicified cysts were present; it seemed unlikely that the poor preservation of cysts in these samples was solely the result of dissolution. Above 208 cm, the cysts were usually abundant and well preserved in the sediment with several densely ornamented, delighted forms. Unornamented Stomatocysts (C001, C009, C049, C125) were present along the sediment core, and usually they were the dominant forms. The proportion of ornamented cysts gradually increased toward the younger sediment core layers. C210 was the most frequent cyst, it was found in all samples. Main cysts types in the diatom assemblages zones In this section we overview the most abundant stomatocyst types according to diatom assemblages zones defined in Soróczki-Pintér et al. (2012). The changes in the diatom assemblages resulted in the delineation of ten diatom assemblage zones (Fig. 20). DAZ-1 276-262 cm; Figs 21–24. Until 276 cm siliceous algae were absent. Above 272 cm the diatom preservation was poor, and only several corroded valves (diatom sternums of Pinnularia Ehrenberg (1843: 45) and Stauroneis Ehrenberg (1843: 45) taxa) were found among the inorganic material. Gomphonema Ehrenberg (1832: 87), Encyonema Kützing (1833: 589) species and Meridion circulare (Greville) C. Agardh (1831: 40) were typical in the upper part of this zone. The C:D ratio was high (60–70%), probably due to better preservation of cysts suggesting that the high C:D ratio can more likely be explained by taphonomy (preservation) than oligotrophy (ecological state). Stomatocysts C001, C057, C116, C210 were the most common morphotypes in this zone. The most densely ornamented form was C300, but most of the cysts in this zone were unornamented. 174 • Phytotaxa 170 (3) © 2014 Magnolia Press


Figure 20. Relative abundances and zonation of the most common diatoms in Lake Gales. Diatoms were ordered according to their occurrences.

DAZ-2 262–246 cm; Figs 25–29. This zone was characterized by a scarce number of siliceous algae remains. A sharp change due to a large increase on the relative abundance of aerophytic taxa (Hantzschia amphioxys (Ehrenberg) Grunow in Cleve & Grunow (1880: 103), Pinnularia borealis Ehrenberg (1843: 420), Orthoseira roseana (Rabenhorst) O’Meara (1875: 255) and Diadesmis Kützing (1844: 109) spp.), defined this zone. This increase on aerophytic taxa, could be related to an increase on seasonal aridity or desiccation of Lake Gales. The C:D ratio was relatively low in this zone (ca. 40%). Stomatocyst C210 showed the highest abundance (ca. 70%). C135 and C009 were frequently observed on all the analyzed samples from this zone. C286 was the largest cyst in this zone. C079 and the unidentified Stomatocyst 14 were found only in DAZ-2. The presences of these last two stomatocysts were only observed under LM. DAZ-3 246–208 cm; Figs 30–33. Between 246 and 208 cm benthic (e.g. Surirella linearis W. Smith (1853: 31)) and periphytic diatoms (Encyonema gaeumannii (Meister) Krammer (1997: 78), with other cymbelloid taxa, Gomphonema spp.) increased their relative abundance. Periphytic and benthic diatoms were distinguished on the basis of their attaching capacity: tube dwelling and stalk-bearing (attached) taxa were marked as periphytic. While of the previously zone dominant aerophytic taxa (Hantzschia amphioxis, Pinnularia borealis, Orthoseira roseana) decreased their contribution in the diatom assemblages. The C:D ratio is high (> 50%). C049, C169, C360 were frequent. Furthermore, the first occurrence of C072 was detected at 216 cm.



Figures 21–40 The most characteristic stomatocysts of Lake Gales according to their occurrences in the first five diatom assemblages’ zones (between DAZ–1 and DAZ–5). Figs 21–24 DAZ–1: Fig. 21. C116—264 cm, Fig. 22. C049—264 cm; Fig. 23. C189—264 cm; Fig. 24; C300B—264 cm; Figs 25–29 DAZ–2: Fig 25. C210—260 cm; Fig. 26. C169—260 cm, Fig. 27. C135—260 cm; Fig. 28. “Unidentified stomatocyst 14”—260 cm; Fig. 29. C079—260 cm; Figs 30–33, DAZ–3: Fig. 30. C189—236 cm, Fig. 31. C318—236 cm; Figs 32–33 C360—236 cm; Figs 34–37 DAZ–4: Fig. 34. C120—196 cm; Fig. 35. C202—196 cm; Fig. 36. C239—196 cm; Fig. 37. C148 note the short, thin spines that are roughly equidistant—196 cm; Figs 38–40 DAZ–5: Fig. 38. C121—188 cm, Fig. 39. C169—188 cm; Fig. 40. C009—188 cm.

176 • Phytotaxa 170 (3) © 2014 Magnolia Press


DAZ-4 208–194 cm; Figs 34–37. The dominance of benthic, mainly fragilaroid taxa (Staurosira venter (Ehrenberg) Grunow (1882: 139), Staurosirella pinnata (Ehrenberg) D.M. Williams & Round (1987: 274)) characterized this zone. In addition, a periphytic taxon Achnanthidium minutissimum (Kützing) Czarnecki (1994: 157) reached higher abundances (up to 13% at 200 cm) in this zone. The abundance of the epipsammic Sellaphora C. Mereschkowsky (1902:186) taxa was also increased at the end of this zone. In DAZ-4 the most common stomatocysts were C210, C072, C148, C042. Stomatocysts C120, C202, C239 were also observed, but in low numbers. The first occurrence of C310 was detected in this zone, at 196 cm. Furthermore, C”17” = Chrysococcus furcatus (Dolgoff) K.H.Nicholls (1981: 18) was also recorded from this zone. (C”17’ was originally described as a stomatocyst, but it is the silicified vegetative cell of C. furcatus. C130, that is a cysts produced by C. furcatus have also been found in Lake Gales.) DAZ-5 194–184 cm; Figs 38–40. The dominant diatoms in DAZ-5 zone were: Staurosira venter, Achnanthes ventralis (Krasske) Lange-Bertalot in Lange-Bertalot & Krammer (1989: 155), Navicula schmassmannii Hustedt (1943: 400), Adlafia minuscula (Grunow) Lange-Bertalot in Lange-Bertalot & Genkal (1999: 32) and epipsammonic Sellaphora. C:D ratio was ca 35%. The ornamented stomatocysts C210 and C072 characterized this zone, but C050, C052 and C009 were the most dominant. The cyst morphotypes C121 and C169 were also observed. DAZ-6 184–178 cm, Figs 41–44. The most remarkable changes in the diatom record have been detected in this zone, when a spine like, lightly silicified diatom, Fragilaria gracilis Østrup (1910: 190), became dominant reaching more than 70% at 9,200 cal yr BP. C:D ratios showed the lower values (ca. 10%) in this period from the entire sediment record. The stomatocyst assemblages also showed a rapid and singular change. C072, a large, ovoid stomatocyst with very special outline and ornamentation reached a peak, and dominate (more than 50%) the entire stomatocyst assemblage. This cyst type was found in high alpine, slightly acid to neutral lakes (Facher & Schmidt 1996). C210, the large C166 and other unornamented forms, such as C050 were also abundant. C121, C112P were sporadic. DAZ-7 178–158 cm; Figs 45–48. In the first part of the zone fragilaroid taxa was dominant (mainly Staurosira venter) but the relative abundance of Aulacoseira Thwaites (1848: 167) taxa (Aulacoseira alpigena (Grunow) Krammer (1991: 93), Aulacoseira ambigua (Grunow) Simonsen (1979: 56), Aulacoseira pfaffiana (Reinsch) Krammer (1991: 94)) gradually increased and replaced the benthic fragilaroid diatoms. The C:D ratio was higher than in DAZ-6, (ca. 35%). In line with the observed shift on diatom composition, the stomatocyst’s composition also changed. First of all the relative abundance of C072 sharply decreased. The abundance of C310 showed a slowly increase, and several cysts ornamented with long spines were observed (C355, C502, C505). This zone was characterized by C355, C505, C166, C210, C345, C057, C001, C198, C148, C337 see also Figs 45–48. DAZ-8 158–74 cm; Figs 49–52. In DAZ-8 small-celled monoraphid taxa (Psammothidium curtissimum (J.R. Carter) M. Aboal in Aboal et al. (2003: 171), Achnanthidium minutissimum, Karayevia oblongella (Østrup) M. Aboal in Aboal et al. (2003: 159)) became more abundant besides Aulacoseira taxa. Diatoma mesodon (Ehrenberg) Kützing (1844: 47) were the characteristic diatom of this zone. The C:D ratio was very high (ca. 70%). The number of ornamented stomatocyst morphotypes such as C004, C057, C166, C180, C272, C324 increased. DAZ-9 74–26 cm Figs 53–56. Remarkable and abrupt changes in the diatom assemblages were observed at 3700 cal yr BP, when planktonic diatoms (Aulacosiera pfaffiana, A. valida (Grunow) Krammer )1991: 484), A. nivalis (W. Smith) English and Potapova (2009: 39), A. alpigena) became dominant. The relative abundance of Diatoma mesodon decreased. Psammothidium Chrysophyten cysts in Retezat Mountain


helveticum (Hustedt) Bukhtiyarova & Round (1996: 8), Encyonema gauemanni and some Pinnularia species had significant contribution to the diatom assemblages. The abundance of fragilaroid taxa in the zone was the lower in the record. The C:D ratio was low, ca. 20%. Some densely ornamented stomatocysts, (C133, C220, C336, C300), and the large C166 were characteristic stomatocyst of this zone together with the planktonic diatoms. The relative abundance of C310 showed an increasing trend, while C072 decreased. The occurrences of newly described forms (C500, C501, and C502) were the highest (Figs 1–3, 8–13) in DAZ–9.

Figures 41–60 The most characteristic stomatocysts of Lake Gales according to their occurrences in the upper five diatom assemblages’ zones (between DAZ–6 and DAZ–10). Figs 41–44 DAZ–6: Fig. 41. C072—180 cm; Fig. 42. C050 —180 cm; Fig. 43. C072—180 cm; Fig. 44. C166—180 cm; Figs 45–48 DAZ–7: Fig. 45. C001—168 cm; Fig. 46. C198—168 cm; Fig. 47. C148—168 cm; Fig. 48. C337– 176 cm; Figs 49–52 DAZ–8 Fig. 49. C057– 104 cm; Fig. 50. C324—168 cm; Fig. 51. C004—88 cm; Fig. 52. C180—104 cm; Figs 53–56 DAZ–9: Fig. 53. C133—48 cm; Fig. 54. C220—56 cm; Fig. 55. C092—168 cm; Fig. 56. C357—48 cm; Figs 57–60 DAZ–10: Fig. 57. C336—2 cm; Fig. 58. C035—2 cm; Fig. 59. C243—2 cm; Fig. 60. C345—2 cm.



DAZ-10 26–0 cm; Figs 57–60. The relative abundance of Aulacoseira taxa slightly decreased, while fragilaroid taxa and Diatoma mesodon became more frequent, as well as, small monoraphids (Achnanthidium minutissimum, Karayevia oblongella, Planothidium Round & L. Bukhtiyarova (1996: 351) spp., Psammothidium (L. Bukhtiyarova & Round 1996: 3) spp.). The C:D ratio sharply increased, and was significantly higher (> 50%) than in DAZ-9. The most frequently observed stomatocysts in DAZ-10 were C310, C035, C169, C345 and C166. The new described stomatocysts (C500 and C501) were often observed in this zone. The portion of ornamented forms was the higher one on the Lake Gales sediment record. Table 1: Stomatocyst morphotypes present in Gales sediments (Retezat Mts, South Carpathians) that were described by Duff et al. (1995), Facher & Schmidt (1996), Wilkinson et al. (2001), Pla (2001) and Kamenik (2010). PEARL refers to Duff et al. (1995), and Wilkinson et al. (2001). Note the different authors use different numbering. C prefix refer to „Carpathians”, * = identification based on Stom@tocyst database (Kamenik 2010). Stomatocyst C001

PEARL #1

Pla S001

Facher & Schmidt Kamenik

#4 #9

S004 S009

n° 60

#15

S015

#29

S029

#35 #49

S035 S049

# 50

S050 S052

C053 C056

Author Duff & Smol, 1988 emend. Zeeb & Smol 1993a Duff & Smol 1988 Duff & Smol, 1988 emend. Zeeb & Smol 1993a Duff & Smol, 1988 emend. Zeeb & Smol 1993a Duff & Smol, 1988 emend. Zeeb & Smol 1993a Duff & Smol 1989 Duff & Smol 1989 Duff & Smol, 1988 emend. Zeeb & Smol 1993a Duff & Smol 1991 Duff & Smol 1991 emend Duff et al. 1995 Duff & Smol 1991 Pla 2001

C057 C064 C072 C079 C084 C092

Duff & Smol 1991 Duff & Smol 1991 Facher & Schmidt 1996 Duff & Smol 1991 Duff & Smol 1991 Facher & Schmidt 1996

#057 #64

C103 C112Z

Duff & Smol 1991 #103 Zeeb et al., 1990 emend. Duff et Smol #112 1994 Pla 2001

C004 C009 C015 C029 C033 C035 C049 C050 C052

C112P C113 C115 C116 C120 C121 C125 C130 C133 C135 C136 C137

Zeeb et al., 1990 Zeeb et al., 1990 Zeeb et al., 1990 Duff & Smol in Duff et al., 1992 emend. Zeeb & Smol 1993 Pla 2001 Duff & Smol in Duff et al., 1992 Duff & Smol in Duff et al., 1992 emend. Duff & Smol 1994 Duff & Smol in Duff et al., 1992 emend. Zeeb et al., subm. emend. Duff & Smol 1994 Duff & Smol in Duff et al., 1992 Duff & Smol in Duff et al., 1992 Duff & Smol in Duff et al., 1992

# 53 #56

#079 #310

#113 #115 #116 #120

#125 #130

ST 149

ST 17

The description fits to Pla, 2001

S056 S057 n° 84 S064 cf. n° 72 S079 n° 62 n° 92

Stomatocysts S056 f. B Pla, 2001

ST 84

ST 150 ST 92

S112 S113

n° 81

ST 152, ST 154

Only in LM cf. Different than S310 Pla, 2001

Identical with S112 Pla, 2001

ST 143

S120 S121 S125 S130

comment

n° 82

ST 151

#133 #135 #136 #137

S135 S137

Only in LM ......continued on the next page



Table 1. (continued) Stomatocyst C148*

Author Kamenik

C149 C160* C166 C169 C178 C180 C189 C198 C202 C207 C210 C214 C220 C223 C231 C232 C239 C243 C272 C286 C298 C300 C318 C319 C320 C324 C331 C336 C336 C337 C340 C345 C357 C360 C392 C404 C”17”

Zeeb & Smol 1993a Kamenik Zeeb & Smol 1993a Zeeb & Smol 1993a Zeeb & Smol 1993a Zeeb & Smol 1993a Zeeb & Smol in Zeeb et al., subm. Pla 2001 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff & Smol 1994 Duff et al., 1995 Duff & Smol in Duff et al., 1995 Gillbert & Smol in Gilbert et al., 1997 Gilbert & Smol in Gilbert et al., 1997 Gilbert & Smol in Gilbert et al., 1997 Pla 2001 Brown & Smol in Brown et al. Pla 2001 Brown & Smol in Brown et al. 1997 Pla 2001 Wilkinson & Smol 1998 Pla 2001 Pla 2001 Wilkinson & Smol 1998 Pla 2001 Pla 2001 Pla 2001 Pla 2001 Pla 2001 Pla 2001 Chrysococcus furcatus (Dolgoff) Nicholls 1981 Wilkinson & Smol in Wilkinson et al. 1996

Unid. 14

PEARL #43, #47, #59, #73

Pla

#166 #169 #178 #180 #189 #198 #202 #207 #210 #214 #220 #223 #231 #232 #239 #243 #272 #286 #298

S166 S169 S178 S180 S189 S198 S202 S207 S210

#318 #142 #331 #337

Facher & Schmidt Kamenik

S149

S223 S231 S232 S239 S243

n° 58

ST 58 ST 162

comment Kamenik database

Kamenik database

ST 124 S198 f. A Pla, 2001

cf. n° 79

n° 101

ST 79

Only in LM Stomatocyst 300 f. B

S319 S320 S324 S336 S336 S340 S345 S357 S360 S392 S404

Stomatocysts S336 f. A Stomatocysts S336 f. B

n° 93 n° 91

cf. Only in LM “Unidentified 14”

Discussion Systematics of stomatocysts There have been several attempts to improve the systematic of stomatocysts. Recently only about 10–15% of stomatocyst morphotypes can be linked to the chrysophycean species that produce them, so there is no option to follow the natural system, to classify the cysts as statospores of their producers (Zeeb & Smol 2001). Several artificial classification systems have been proposed (e.g. Preisig 1995, Cronberg & Sandgren 1986) with artificial genera, but finally instead of the Linnaean binominal nomenclature, the numbering scheme of the forms became accepted and used (Duff et al. 1995, Pla 2001, Wilkinson et al. 2001). For the identification of stomatocysts, authors often use their own systems that cause difficulties in the understanding and comparison of cyst’s floras of different localities. In Atlas I Duff et al. (1995) numbered the forms from 1 to 243 (distinguished 240 forms), and in Atlas II (Wilkinson et al. 2001) the authors continued the numbering, from 244 until 387 (173 stomatocysts were formally described and several emended descriptions were added to the previously defined forms). At the same time, Pla (2001) published his monograph on the stomatocysts from the Pyrenees, where he gave numbers for new types higher than 300, hence the first new cyst of Pla is S300. The highest number in Pla’s atlas is S421. A completely different numbering was introduced by Facher & Schmidt (1996), publishing their paper at the same times than Atlas I (Duff et al. 1995) on the stomatocyst flora of Central European lakes. Kamenik 180 • Phytotaxa 170 (3) © 2014 Magnolia Press


(e.g. Kamenik et al. 2001, Kamenik 2010) partly followed and improved Facher & Schmidt’s system. Recognizing the confusion, an effective and useful database was developed by Kamenik (2010), where all references to a given stomatocyst are available (www.stomatocysts.unibe.ch/wiki/home). In Table 1 we present the known “synonyms” for better comparison of our data to the previously studied stomatocysts assemblages. Stomatocyst richness and diversity Our preliminary results of low-resolution cyst analyses from Lake Gales revealed a similar flora of high mountain lakes with some new entities. The number of new morphotypes discovered seems moderate, given that this was the first taxonomical work on chrysophyte subfossils from the Southern Carpathians. Fourteen percent of all recorded forms proved to be new, and this is a very similar proportion to the one found by Betts-Piper et al. (2004) in the Svalbard sediments where up to 14% of the forms were new ones. This preliminary study suggests that there may exists a distinct “Carpathians” crysophyte flora, including common taxa that are typical of mountain environments in Europe, or that are considered cosmopolitan. The dominance of unornamented forms over ornamented forms appears to be emerging as a characteristic of arctic/mountain environments (e.g. Wilkinson et al. 1997, Stewart et al. 2000, Pla 2001). Similar results have been presented in clear water oligotrophic lakes elsewhere (Betts-Piper et al. 2004). By comparison, stomatocyst richness of lakes reported by Firsova et al. (2012) recovered only thirty-six identified cysts, but among them twenty were new morphotypes from Lake Hovsgol, Mongolia’s largest freshwater lake. In Lake Redo d’Aigüestortes (Pyrennes) 120 different forms were distinguished during the 13,000 year long history of the lake by Pla (2001) and 132 morphotypes in the oligotrophic Lake Redon, Pyreness during 10.000 years (Pla, unpublished data; Pla & Catalan, 2005). The richest stomatocyst assemblages were detected in high-Alpine Lake Silvaplana (Switzerland) by Baumann et al. (2010). They found more than 160 different stomatocyst types, that really seems a remarkable high diversity in comparison with other high-Alpine lakes (e.g. Facher & Schmidt 1996, Lotter et al. 1997, Kamenik et al. 2001, Lotter et al. 2002, Kamenik & Schmidt 2005a, Schmidt et al. 2007). In this context we infer that the stomatocyst flora of Lake Gales must include more morphotypes as the numbers of observed morphotypes have been found to be related to the number of samples (Pla 2001). These examples refer to the number of cysts that were detected during the ontogeny of a lake. For a wider context, stomatocyst richness of different lake districts in the world (summarized in Table 5 in Pla 2001) varies between 100 and 250, but these data usually refer to surface samples and once again the total number of observed morphotypes are related to number of samples that have been analyzed (Pla 2001). For example, a total of 181 morphotypes were identified from 71 lakes in Adirondack Park, USA (Duff & Smol 1995), 137 morphs from 35 ponds on Ellesmere Island in the Canadian high Arctic (Wilkinson et al. 1997) and 126 morphotypes from 50 Central European lakes (Facher & Schmidt 1996). Two-hundred fourty-six cysts from 110 Ontario Lakes were reported (Wilkinson & Smol 1998), which is the most diverse assemblage. According to our unpublished data, other lakes in the Southern Carpathians support different cysts assemblages, suggesting that the stomatocyst richness of Retezat will be similar to other European mountain region’s flora. Regional comparison/dominancy It is premature to present a regional comparison about the common stomatocysts of Europe, but the similarity of cysts of Lake Gales to cysts of the Pyrenees is obvious. The following 14 cysts were found more than 75% of the studied samples in Pyrenees by Pla (2001): S046, S009, S001, S239, S049, S050, S033, S340, S310, S210, S035, S351, S004, S198 (cysts arranged in descending order of their occurrence). All of them, but S351 were common and frequent in our samples as well. S345 and S310 were reported as endemic to the Pyrenees (Pla 2001), but both cysts are common and abundant in Lake Gales and have been recently also found in Norway (Pla unpublished data). Comparison with the other European lakes cyst floras is more difficult, because of the application of collective categories in paleolimnological studies and the different numbering (e.g. Kamenik et al. 2001, Lotter et al. 2002, Kamenik & Schmidt 2005a 2005b). However, on the basis of the Stomatocyst database (Kamenik 2010), in the Nižné Terianske Pleso apart from the collective category composite by #234, #052, #130, 92 Facher & Schmidt, #073, #110 and #239 are common. In Lake Gales apart of #073, #110 was not only observed from the above mentioned common European cysts; the other stomatocysts were also common in Lake Gales, meaning the stomatocyst assemblages of these lakes are similar.



Paleolimnological implication The main aim of this paper was to describe a new stomatocysts and create the taxonomical basis for a subsequent high resolution stomatocyst analyses in the South Carpathians, but the preliminary results allow us to infer some remarkable changes in the stomatocysts community of Lake Gales. According to our unpublished results of this study, chrysophycean cysts in Lake Gales showed obvious changes between the Late Glacial and Holocene assemblages. In the bottom samples we found more unornamented and larger forms, while in the younger layers ornamented forms are more abundant. Hence, cysts with long spines and ridges are the characteristic forms in the upper layers despite the dominance of unornamented forms in the whole sequence.

Figure 61. The relative abundances of some siliceous fossils in Lake Gales, and the ratio of cysts and diatoms.

From paleolimnological point of view, the similar response of siliceous algae (diatoms and stomatocysts) to environmental changes was the most remarkable result of this study. One of the most easily recognizable forms among the stomatocysts of Lake Gales was stomatocyst C072 (Figs 41, 43). The relative abundance of C072 showed a sharp peak around 9200 cal yr BP (Fig. 61). Exactly in this period (DAZ-6 in Figs 20 and 61) a spine-like diatom (Fragilaria gracilis) also became dominant. The ratio of cysts and diatoms showed also a minimum value during this period (Fig. 61). We must emphasize, that two independent samples were dated at 179 cm depth (a Pinus needle and Cladocera remains). Their radiocarbon ages agreed well since both dates are identical within the standard error of the 14 C measurement: 9199±127 and 9155±163 cal yr BP respectively. We inferred high lake level, increasing erosion and decreasing in-lake productivity, which is likely linked to an increase on winter and spring moisture availability and cooling (Magyari et al. 2013). This siliceous algae peak was unique and well-dated. This event could be linked to the cold widespread event around 9.3-ka significant climatic anomaly, which was triggered by a meltwater pulse into the North Atlantic (Fleitmann et al. 2008). The Greenland ice-core records have also demonstrated that marked climatic shifts occurred ca. 9.3 ka ago, which was one of the most remarkable cold events during the Holocene (Lowe et al. 2008). Many high-resolution proxy studies have proved the cooling due to the slow-down of the thermohaline circulation at high and mid-latitudes in the Northern Hemisphere (Fleitmann et al. 2008). We suggest that the abrupt change in the Lake Gales diatom and stomatocyst record could be linked to this short climatic anomaly. In the South Carpathian area, this cold event resulted in an increase on winter and spring moisture availability and a decrease in temperatures. In Lake Gales, all the data refer to the siliceous algae evidenced a for short-term lake level increase.



This study provided the first step in the chrysophycean based paleoenvironmental reconstruction of the South Carpathian Mountains. However, there is clearly a need for further work on both modern (e.g. define the cysts autoecology) and fossil chrysophyte cyst assemblages from the Carpathians for better understanding of the recent and past changes.

Acknowledgements We would like to express our thanks to Pat Kociolek for his support, and the anonym reviewer for valuable and important corrections and advices for improving this work. We acknowledge the support of the Hungarian Scientific Fund (OTKA 83999 and NF 101362). This is a Hungarian Academy of Sciences—Hungarian Natural History Museum Paleo Contribution No. 192. ÉSP was supported by TÁMOP-4.2.4.A/2-11/1-2012-0001 ’National Excellence Program - PhD student personal support system convergence program’ CSK worked within ‘A2-MZPD-12-0296’ in the framework of TÁMOP-4.2.4.A/2-11/1-2012-0001 key project which is realized with the support of the Hungarian Government and the European Union with the co funding of the European Social Fund.

References Aboal, M., Alvarez Cobelas, M., Cambra, J. & Ector, L. (2003) Floristic list of non-marine diatoms (Bacillariophyceae) of Iberian Peninsula, Balearic Islands and Canary Islands. Updated taxonomy and bibliography. Diatom Monographs 4: 1–639. Agardh, C.A. (1831) Conspectus Criticus Diatomacearum. Part 3. Lundae [Lund]: Literis Berlingianus. pp. 33–48. Battarbee, R.W. (1986) Diatom analysis. In: Berglund, B.E. (ed.) Handbook of Holocene Palaeoecology and Palaeohydrology. John Wiley & Sons, Chichester, New York, Brisbane, Toronto, Singapore, pp. 527–570. Baumann, E., de Jong, R., & Kamenik, C. (2010) A description of sedimentary chrysophyte stomatocysts from high-Alpine Lake Silvaplana (Switzerland). Nova Hedwigia, Beiheft 136: 71–86. Betts-Piper, A.M., Zeeb, B.A. & Smol, J.P. (2004) Distribution and Autecology of Chrysophyte Cysts from High Arctic Svalbard Lakes: Preliminary Evidence of Recent Environmental Change. Journal of Paleolimnology 31: 467–481. http://dx.doi.org/10.1023/b:jopl.0000022546.21996.41 Braun, M., Hubay, K., Magyari, E.K., Veres, D., Papp, I. & Bálint, M. (2013) Using linear discriminant analysis (LDA) of bulk sediment geochemistry data to reconstruct Lateglacial climate change in the South Carpathian Mts. Quaternary International 293: 114–122. http://dx.doi.org/10.1016/j.quaint.2012.03.025 Buczkó, K. (2004) Szent Anna cisztái. [Stomatocysts of Lake Saint Anna]. Élet és Tudomány 59: 748–750. Buczkó, K. & Magyari, E. (2006) A Szent Anna-tó a palaeolimnológus szemével. [The Lake Saint Anna in the palaeolimnologists eyes]. Természet Világa 137: 570–571. Buczkó, K., Magyari, E., Soróczki-Pintér, É., Hubay, K., Braun, M. & Bálint, M. (2009) Diatom-based evidence for abrupt climate changes during the Lateglacial in the South Carpathian Mountains. Central European Geology 52: 249–268. http://dx.doi.org/10.1556/ceugeol.52.2009.3-4.3 Buczkó, K., Magyari, E.K., Hübener, T., Braun, M., Bálint, M., Tóth, M. & Lotter, A.F. (2012) Responses of diatoms to the Younger Dryas climatic reversal in a South Carpathian mountain lake (Romania). Journal of Paleolimnology 48: 417–431. http://dx.doi.org/10.1007/s10933-012-9618-1 Buczkó, K., Magyari, E.K., Braun, M. & Bálint, M. (2013) Diatom˗inferred lateglacial and Holocene climatic variability in the South Carpathian Mountains (Romania). Quaternary International 293: 123–135. http://dx.doi.org/10.1016/j.quaint.2012.04.042 Bukhtiyarova, L. & Round, F.E. (1996) Revision of the genus Achnanthes sensu lato section Marginulatae Bukh. sect. nov. of Achnanthidium Kütz. Diatom Research 11: 1–30. Cabała, J. & Piàtek, M. (2004) Chrysophycean stomatocysts from the Staw Toporowy Nizni lake (Tatra National Park, Poland). Annales de Limnologie 40: 149–165. http://dx.doi.org/10.1051/limn/2004013 Cabała, J. (2005) Chrysophycean stomatocysts from Morskie Oko and Żabie Oko lakes in the Tatra National Park, Poland. Acta Societatis Botanicorum Poloniae 74: 305–314. http://dx.doi.org/10.5586/asbp.2005.039 Cărăuş, I. (2012) Algae of Romania—a distributional checklist of acutal algae. In: Studii şi Cercetări Ştiinţifice, Seria Biologie, Universitatea din Bacău, Facultatea de Ştiinţe, Catedra de Biologie, 2002, 809 pp., version 2.3—third revision Cleve, P.T. & Grunow, A. (1880) Beiträge zur kenntniss der arctischen Diatomeen. Kongliga Svenska-Vetenskaps Akademiens Handlingar



17: 1–121. Czarnecki, D.B. (1994) The freshwater diatoms culture collection at Loras College, Dubuque, Iowa. In: Kociolek, J.P. (ed.) Proceedings of the 11th International Diatom Symposium, Memoirs of the California Academy of Sciences. San Francisco. pp. 155–174. Cronberg, G. & Sandgren, C.D. (1986) A proposal for the development of standardized nomenclature and terminology for chrysophycean statospores. In: Kristiansen, J. & Anderson, R.A. (eds.) Chrysophytes aspects and problems. Cambridge University Press, Cambridge, pp. 317–328. Duff, K.E. & Smol, J.P. (1995) Chrysophycean cyst assemblages and their relationship to water chemistry in 71 Adirondack Park (New York, USA) lakes. Archiv für Hydrobiologie 134: 307–336. de Jong, K., & Kamenik, C. (2011) Validation of chrysophyte stomatocysts-based cold-season climate reconstruction from high-Alpine Lake Silvaplana, Switzerland. Journal of Quaternary Science, 26: 268–275. http://dx.doi.org/10.1002/jqs.1451 de Jong, K., Kamenik, C., Westover, K. & Grosjean, M. (2013) A chrysophyte stomatocyst-based reconstruction of cold-season air temperature from Alpine Lake Silvaplana (AD 1500–2003); methods and concepts for quantitative inferences. Journal of Paleolimnology 50: 519–533. http://dx.doi.org/10.1007/s10933-013-9743-5 Duff, K.E. & Smol, J.P. (1991) Morphological descriptions and stratigraphic distributions of the chrysophycean stomatocysts from a recently acidified lake (Adirondack Park, N.Y.). Journal of Paleolimnology 5: 73–113. http://dx.doi.org/10.1007/bf00226558 Duff, K.E., Zeeb, B.A. & Smol, J.P. (1995) Atlas of Chrysophycean Cysts. Kluwer Academic Press, Dordrecht, Netherlands, 189 pp. Ehrenberg, C.G. (1832) Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. Abhandlungen der Königlichen Akademie Wissenschaften zu Berlin, Physikalische Klasse 1831: 1–154, pls I–IV. Ehrenberg, C.G. (1843) Mittheilungen über 2 neue asiatische Lager fossiler Infusorien-Erden aus dem russischen Trans-Kaukasien (Grusien) und Sibirien. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1843: 43–49. Ehrenberg, C.G. (1843) Verbreitung und Einfluss des mikroskopischen Lebens in Süd-und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: 291–466, pls 1–4. English, J. & Potapova, M. (2009) Aulacoseira pardata sp. nov., A. nivalis comb. nov., A. nivaloides comb. et stat. nov., and their Occurrences in Western North America. Proceedings of the Academy of Natural Sciences of Philadelphia 158: 37–48. http://dx.doi.org/10.1635/053.158.0102 Facher, E. & Schmidt, R. (1996) A siliceous chrysophycean cyst˗based pH transfer function for Central European lakes. Journal of Paleolimnology 16: 275–321. http://dx.doi.org/10.1007/bf00207575 Firsova, A.D., Vorobyova, S.S. & Likhoshway, Y.V. (2012) Chrysophycean Stomatocysts in the Upper Pleistocene and Holocene Sediments from Lake Hovsgol, Northern Mongolia. International Journal of Geosciences 3: 664–674. http://dx.doi.org/10.4236/ijg.2012.34067 Fleitmann, D., Mudelsee, M., Burns, S.J., Bradley, R.S., Kramers, J. & Matter, A. (2008) Evidence for a widespread 18 climatic anomaly at around 9.2 ka before present. Paleoceanography 23: PA1102. http://dx.doi.org/10.1029/2007PA001519. Grunow, A. (1882) Beiträge zur Kenntnis der fossilen Diatomeen Österreich-Ungarns. In: Mojsisorics, E. & Neumayer, N. (eds), Beiträge zur Paläontologie Österreich-Ungarns und des Orients 2: 136–159. Huber, K., Kamenik, C., Weckström, K. & Schmidt, R. (2009) Taxonomy, stratigraphy, and palaeoecology of chrysophyte cysts from a Late Glacial sediment core section of Längsee, Austria. Nova Hedwigia 89: 245–261. http://dx.doi.org/10.1127/0029-5035/2009/0089-0245 Hustedt, F. (1943) Die Diatomeenflora einiger Hochgebirgseen der Landschaft Davos in den Schweizer Alpen. Archiv für Hydrobiology 43: 124–197. Jancsik, P. (2007) A Retyezát˗hegység (The Retezat Mountains). Pallas˗Akadémia Könyvkiadó, Csíkszereda, 140 pp. Kamenik, C. (2010) Stom@ocysts & Co—web applications to bring the research community together via the Internet. Nova Hedwigia 136: 311–323. Kamenik, C., & Schmidt, R. (2005a) Chrysophyte resting stages: a tool for reconstructing winter/spring climate from Alpine lake sediments. Boreas 34: 477–489. http://dx.doi.org/10.1080/03009480500231468 Kamenik, C. & Schmidt, R. (2005b) Computer-aided SEM analysis of chrysophyte stomatocysts. Nova Hedwigia Beiheft 128: 269–274. Kamenik, C., Schmidt, R., Koinig, K.A., Agusti-Panareda, A., Thompson, R. & Psenner, R. (2001) The chrysophyte stomatocyst composition in high alpine lake (Gossenköllesee, Tyrol) in relation to seasonality, temperature and land-use. Nova Hedwigia, Beiheft 122: 1–22.



Korponai, J., Magyari, E.K., Buczkó, K., Iepure, S., Namiotko, T., Czakó, D., Kövér, Cs. & Braun, M. (2011) Cladocera response to Late Glacial to Early Holocene climate change in a South Carpathian mountain lake. Hydrobiologia 676: 223–235. http://dx.doi.org/10.1007/s10750-011-0881-3 Krammer, K. (1991) Morphology and taxonomy of some taxa in the genus Aulacoseira Thwaites (Bacillariophyceae). I. Aulacoseira distans and similar taxa. Nova Hedwigia 52: 89–112, pls I–X. Krammer, K. (1997) Die cymbelloiden Diatomeen. Eine Monographie der welweit bekannten Taxa. Teil 1. Allgemeines und Encyonema Part. Bibliotheca Diatomologica 36: 1–382. Kullenberg, B. (1947) The piston core-sampler. Svenska Hydrografisk-Biologiska Kommissionens Skrifter 1: 1–46. Kützing, F.T. (1833) Synopsis diatomearum oder Versuch einer systematischen Zusammenstellung der Diatomeen. Linnaea 8: 529–620, pls XIII–XIX. http://dx.doi.org/10.5962/bhl.title.65634 Kützing, F.T. (1844) Die Kieselschaligen Bacillarien oder Diatomeen. pp. 152, pls 1–30. Nordhausen. Lange-Bertalot, H. & Genkal, S.I. (1999) Diatomeen aus Siberien. I. Insel im Arktischen Ozean (Yugorsky-Shar Strait) [Diatoms from Siberia I - Islands in the Arctic Ocean (Yugorsky-Shar Strait)]. In: (Lange–Bertalot, H. ed), Iconographia Diatomologica Königstein: Koeltz Scientific Books. 6, 303 pp. Lange-Bertalot, H. & Krammer, K. (1989) Achnanthes eine Monographie der Gattung mit Definition der Gattung Cocconeis and Nachtragen zu den Naviculaceae. Bibliotheca Diatomologica, Cramer, Berlin–Stuttgart, 18, 393 pp. Lotter, A.F., Appleby, P.G., Bindler, R., Dearing, J.A., Grytnes, J.A., Hofmann, W., Kamenik, C., Lami, A., Livingstone, D.M., Ohlendorf, C., Rose, N. & Sturm, M. (2002) The sediment record of the past 200 years in a Swiss high˗alpine lake: Hagelseewli (2339 m a.s.l.). Journal of Paleolimnology 28: 111–127. http://dx.doi.org/10.1023/a:1020328119961 Lotter, A.F., Birks, H.J.B., Hofmann, W. & Marchetto, A. (1997) Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. I. Climate. Journal of Paleolimnology 18: 395–420. Lowe, J.J., Rasmussen, S.O., Björck, S., Hoek, W.Z., Steffensen, J.P., Walker, M.J.C., Yu, Z. C. & I. Grp. 2008. Synchronisation of palaeoenvironmental events in the North Atlantic region during the Last Termination: a revised protocol recommended by the INTIMATE group. Quaternary Science Reviews 27: 6–17. http://dx.doi.org/10.1016/j.quascirev.2007.09.016 Magyari, E.K., Braun, M., Buczkó, K., Hubay, K. & Bálint, M. (2009) Radiocarbon chronology of glacial lake sediments in the Retezat Mts (South Carpathians, Romania): a window to Late Glacial and Holocene climatic and palaeoenvironmental changes. Central European Geology 52: 225–248. http://dx.doi.org/10.1556/ceugeol.52.2009.3-4.2 Magyari, E.K., Jakab, G., Bálint, M., Kern, Z., Buczkó, K. & Braun, M. (2012) Rapid vegetation response to lateglacial and early Holocene climatic fluctuation in the South Carpathian Mountains (Romania). Quaternary Science Reviews 35: 116–130. http://dx.doi.org/10.1016/j.quascirev.2012.01.006 Magyari, E.K., Demény, A., Buczkó, K., Kern, Z., Vennemann, T., Fórizs, I., Vincze, I., Braun, M., Kovács, J.I., Udvardi, B. & Veres, D. (2013) A 13,600-year diatom oxygen isotope record from the South Carpathians (Romania): Reflection of winter conditions and possible links with North Atlantic circulation changes. Quaternary International 293: 136–149. http://dx.doi.org/10.1016/j.quaint.2012.05.042 Mereschkowsky, C. (1902) On Sellaphora, a new genus of diatoms. Annals and Magazine of Natural History, Series 7 9: 185–195. Nicholls, K.H. (1981) Chrysococcus furcatus (Dolg.) comb. nov.: a new name for Chrysastrella furcata (Dolg.) Defl. based on the discovery of the vegetative stage. Phycologia 20: 16–21. http://dx.doi.org/10.2216/i0031-8884-20-1-16.1 O’Meara, E. (1875) Report on the Irish Diatomaceae. Proceedings of the Royal Irish Academy, Series 2 2: 235–425, pls 26–34. http://dx.doi.org/10.5962/bhl.title.68743 Østrup, E. (1910) Danske Diatoméer. Kjøbenhavn, Copenhagen, C.A. Reitzels Boghandel. pp. 1–323, 5 pls. http://dx.doi.org/10.5962/bhl.title.1044 Péterfi, L.S. (1967) Studies on the Rumanian Chrysophyceae. I. Nova Hedwigia 13: 117–137. Pla, S. (2001) Chrysophycean cysts from the Pyrenees. Bibliotheca Phycologica, Cramer, Berlin, Germany, 109, 179 pp. Pla, S. & Catalan, J. (2005) Chrysophyte cysts from lake sediments reveal the submillennial winter/spring climate variability in the northwestern Mediterranean region throughout the Holocene. Climate Dynamics 24: 263–278. http://dx.doi.org/10.1007/s00382-004-0482-1 Pla, S., Camarero, L. & Catalan, J. (2003) Chrysophyte cyst relationships to water chemistry in Pyrenean lakes (NE Spain) and their potential for environmental reconstruction. Journal of Paleolimnology 30: 21–34. http://dx.doi.org/10.1023/A:1024771619977 Pla, S. & Anderson, N.J. (2005) Environmental factors correlated with chrysophyte cyst assemblages in low arctic lakes of south-west



Greenland. Journal of Phycology 41: 957–974. Pla˗Rabes, S. & Catalan, J. (2011) Deciphering chrysophyte responses to climate seasonality. Journal of Paleolimnology 46: 139–150. http://dx.doi.org/10.1007/s10933-011-9529-6 Preisig, H.R. (1995) A modern concept of chrysophyte classification. In Sandgren, C.D., Smol, J.E. & Kristiansen, J. (eds.) Chrysophyte Algae: Ecology, Phylogeny and Development. Cambridge University Press, Cambridge, pp. 46–74. http://dx.doi.org/10.1017/cbo9780511752292.004 Round, F.E. & Bukhtiyarova, L. (1996) Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11: 345–361. http://dx.doi.org/10.1080/0269249x.1996.9705389 Schmidt, R., Kamenik, C., Roth, M. (2007) Siliceous algae-based seasonal temperature inferences and indicator pollen tracking 4,000 years of climate/land-use interactions in the southern Austrian Alps. Journal of Paleolimnology 38: 541–554. http://dx.doi.org/10.1007/s10933-007-9089-y Simonsen, R. (1979) The diatom system: ideas on phylogeny. Bacillaria 2: 9–71. Smith, W. (1853) A synopsis of the British Diatomaceae; with remarks on their structure, function and distribution; and instructions for collecting and preserving specimens. 1 pp, 89 pp., 31 pls. London: John van Voorst. Soróczki˗Pintér, É., Buczkó, K., Braun, M. & Magyari, E.K. (2012) Későglaciális és holocén vízszintváltozások a Retyezátban egy gleccsertó kovaalga összetétele alapján. (Late glacial and Holocene diatom based lake level reconstruction in a glacial lake in Retezat Mountains (Romania)). Hidrológiai Közlöny 92: 64–67. Soróczki-Pintér, É., Magyari, E.K. & Buczkó, K. (2013) Preuve fondée sur les algues siliceuses de l’augmentation du niveau d’eau et du refroidissement à court terme autour de 9.2-ka dans les Carpates du Sud, Roumanie. (Siliceous algae based evidence for short-term lake level increase and cooling around 9.2-ka BP in the South Carpathian Mountains, Romania). In.: Rimet, F., Bouchez, A., Ector, L. & Montuelle, B. (eds.) Livre des résumés et programme. 7th CE-Diatom Meeting, 32nd ADLaF Meeting. Thonon-les-Bains, France, 16–20 sept. 2013, 77–80. pp Stewart, K., Gregory-Eaves, I., Zeeb, B.A. & Smol, J.P. (2000) Covariation among Alaskan chrysophyte stomatocyst assemblages and environmental gradients: A comparison with diatom assemblages. Nordic Journal of Botany 20: 357–368. http://dx.doi.org/10.1111/j.1756-1051.2000.tb00750.x Tóth, M., Magyari, E.K., Brooks, S.J., Braun, M., Buczkó, K., Bálint, M. & Heiri, O. (2012) Lateglacial summer temperatures in the Southern Carpathians (Romania): a chironomid-based reconstruction. Quaternary Research 77: 122–131. http://dx.doi.org/10.1016/j.yqres.2011.09.005 Thwaites, G.H.K. (1848) Further observations on the Diatomaceae with descriptions of new genera and species. Annals and Magazine of Natural History, Series 2 1: 161–172, pls XI, XII. Van de Vijver, B. &. Beyens, L. (1997a) The Chrysophyte Stomatocyst Flora of the Moss Vegetation from Strømness Bay Area, South Georgia. Archiv für Protistenkunde 148: 505–520. http://dx.doi.org/10.1016/s0003-9365(97)80026-7 Van de Vijver, B. & Beyens, L. (1997b) The Subfossil Chrysophyte Cyst Flora of Some Peat Samples from Kerguelen Islands. Archiv für Protistenkunde 148: 491–503. http://dx.doi.org/10.1016/s0003-9365(97)80024-3 Vorobyova, S.S., Pomazkina, G.V., Baranova, E.Yu., Likhoshway, Ye.V. & Sandgren, C.D. (1996) Chrysophycean cysts (stomatocysts) from Lake Baikal and Irkutsk Reservoir, Siberia. Journal of Paleolimnology 15: 271–277. http://dx.doi.org/10.1007/bf00213046 Wilkinson, A.N., Zeeb, B.A., Smol, J.P., & Douglas, M.S.V. (1997) Chrysophyte stomatocyst assemblages associated with periphytic, high Arctic pond environments. Nordic Journal of Botany 17: 95–112. http://dx.doi.org/10.1111/j.1756-1051.1997.tb00293.x Wilkinson, A.N. & Smol, J.P. (1998) Chrysophycean stomatocyst flora from south-central Ontario lakes. Canadian Journal of Botany 76: 836–862. http://dx.doi.org/10.1139/cjb-76-5-836 Wilkinson, A.N., Zeeb, B. & Smol, J.P. (2001) Atlas of Chrysophycean Cysts, Volume II. Kluwer Academic Publishers, Dordrecht, 180 pp. Williams, D.M. & Round, F.E. (1987) Revision of the genus Fragilaria. Diatom Research 2: 267–288. http://dx.doi.org/10.1080/0269249x.1987.9705004 Zeeb, B.A. & Smol, J.P. (2001) Chrysophyte scales and cysts. In: Smol, J.P., Birks, H.J.B. & Last, W.M. (eds.) Tracking Environmental Change Using Lake Sediments Volume 3: Terrestrial, Algal, and Siliceous Indicators. Kluwer Academic Publishers, Dordrecht, pp. 203–223.

