Journal of Ecology and Environment

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Published online April 12, 2022
https://doi.org/10.5141/jee.22.004

Journal of Ecology and Environment (2022) 46:10

© The Ecological Society of Korea.

Diversity of phytoplankton from the Nakdong River, South Korea: Euglenophytes

Han Soon Kim *† and Jae Hak Lee

Department of Biology, Kyungpook National University, Daegu 41566, Republic of Korea

Correspondence to:Han Soon Kim
E-mail kimhsu@knu.ac.kr

Han Soon Kim and Jae Hak Lee contributed equally to this work.

Received: January 10, 2022; Revised: February 28, 2022; Accepted: March 8, 2022

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Background: Many investigations on phytoplankton from the Nakdong River carried out. However, since the weirs were constructed, only changes in phytoplankton biomass and dominant species have been restrictively studied in phytoplankton investigations in the Nakdong River. Added to this, any investigation on the phytoplankton flora has not been done in the Nakdong River. The aim of this study is to elucidate the characteristics of phytoplankton communities in the Nakdong River with the weirs built in it.
Results: We observed a total of 103 taxa of Euglenophytes belonging to 8 genera from middle-lower part of the Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, followed Lepocinclis (20), Phacus (17), Strombomonas (14), Euglena (5), Colacium (3), Monomorphina (3) and Menoideum (1). Among them, a total of 22 taxa including Colacium (1), Lepocinclis (8), Phacus (4), Strombomonas (4) and Trachelomonas (5) were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River. All the species are illustrated with photomicrographs, and new to Korean species briefly discussed with regard to their taxonomy together with photomicrographs.
Conclusions: The present study, a total of 22 taxa including one species of Colacium, 8 taxa of Lepocinclis, 4 taxa of Phacus, 4 taxa of Strombomonas and 5 taxa of Trachelomonas were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River.

Keywords: Euglenophytes, phytoplankton diversity, Nakdong River, photomicrographs

The Nakdong River is the second longest river on the Korean peninsula with a length of about 510 km and a watershed area of 23,860 km2. As many as 13 million people reside in the basin area. The Nakdong River provides a source of portable and living water to approximately 10 million citizens in not only metropolitan cities such as Daegu, Busan, and Changwon but also many smaller cities. Sixteen large-scale weirs were built in 2012 as part of the Four Major Rivers Project with eight along the Nakdong River included in it with the goal of securing water quantity, mitigating the consequences of droughts and preventing against flooding. The weir construction project interrupts natural water flow and makes a distinct change in the aquatic ecosystem such as hydrological features, water qualities and aquatic communities including freshwater algae (Cha et al. 2015).

In particular, the eight weirs constructed in the Nakdong River substantially changed the river ecosystem overall in terms of not only epilithic diatom assemblages but also hydraulic and hydrologic factors such as water flow reduction, the consequently increasing hydraulic retention time and physico-chemical properties (Lee et al. 2021; Park et al. 2021). Added to this, every summer sees blue-green algal blooms by dominated species such as Microcystis aeruginosa, Aphanizomenon flos-aquae, Anabaena planktonica in the Nakdong River.

Under these circumstances, the phytoplankton community in the Nakdong River can be affected by hydraulic and hydrological variations such as water flow reduction, an increasing retention time and physico-chemical properties following the weir construction.

Many investigations on phytoplankton flora in Korea have been conducted across various regions since Skvortzow (1929) reported 58 diatoms taxa in Lake Seoho, Suwon. And, most of the studies were carried out in lentic waterbodies such as dams, reservoirs and swamps (Chung 1976; Chung 1979; Chung et al. 1972a; Chung et al. 1972b; Kim 1997; Kim 2013a; Kim 2013b; Kim 2013c; Kim 2014a; Kim 2014b; Kim 2018; Kim et al. 1995; Kim et al. 2009; Kim et al. 2020; Kim and Chung 1993a; Kim and Chung 1993b; Kim and Kim 2017). Meanwhile, investigations have been done relatively on a smaller scale in lotic waterbodies (Cho et al. 1993; Choi et al. 2007; Chung et al. 1965; Chung et al. 1968; Chung et al. 1994; Chung et al. 2013; Jeong et al. 2010; Kim 2003; Kim 2004; Kim and Boo 1996; Kim and Lee 1991; Lee et al. 2002; Lee and Jung 2004; Park et al. 1995; Seo and Chung 1994).

Especially, phytoplankton investigations in the Nakdong River were performed primarily at downstream sections including estuary reservoirs before the weir construction (Cho et al. 1993; Choi et al. 2007; Chung et al. 1994; Kim 2004; Kim and Lee 1991; Seo and Chung 1994). Since the weirs were constructed, only changes in phytoplankton biomass and dominant species have been restrictively studied in phytoplankton investigations in the Nakdong River (Lee et al. 2018). Added to this, any investigation on the phytoplankton flora has not been done in the Nakdong River.

Meanwhile, the first report regarding the distribution of Euglenophytes across Korea was published in 1956 (Chung), and many floristic and taxonomic studies of Euglenophytes have been performed in different regions of Korea, most of which surveyed a regional flora including various habitats such as reservoirs, swamps, ditches and ponds (Conforti and Ruiz 2001; Conforti and Ruiz 2002; Chung 1975; Chung and Chang 1957; Chung and Kim 1992; Chung and Kim 1993; Kim 2013c; Kim and Boo 1996; Kim and Boo 1998; Kim et al. 1998; Kim et al. 2000a; Kim et al. 2000b; Wui and Kim 1987). Over 340 taxa of Euglenophytes are known currently in Korea (Kim 2018; Lee and Kim 2015), 30 of which have been found in the main stream section of the Nakdong River until now (Cho et al. 1993; Choi et al. 2007; Chung et al. 1994; Chung et al. 2000; Chung et al. 2013; Kim and Lee 1991; Seo and Chung 1994).

The aim of this study is to elucidate the characteristics of phytoplankton communities in the Nakdong River with the weirs built in it.

Study site

The Nakdong River is the second longest river in South Korea with a river length of about 510 km flows from north to south of Korean peninsula, and the Nakdong River estuary dam is located in the mouth of the river and eight weirs at middle-lower part were constructed in 1987 and 2012, respectively (Fig. 1). The total watershed area is 23,860 km2 and reside about 13 million person in the basin area. The Nakdong River water used as drinking and living water for approximately 10 million in meteropolitan cities Daegu, Busan and Changwon and many smaller cyties.

Figure 1. Map showing the sampling sites and eight weirs and estuary dam of the Nakdong River. SJ: SangJu; ND: Nakdan; GM: Gumi; CG: Chilgok; GG: Gangjeong-Goryeong; DS: Dalseong; HC: Hapcheon-Changnyeong; CH: Changnyeong-Haman.

Sample collection, identification and water quality parameters

Over 2,500 samples in 10 sites of four weirs–Gangjeong-Goryeong (GG), Dalseong (DS), Hapcheon-Changnyeong (HC), Changnyeong-Haman (CH) and estuary dam were collected from June 2017 to December 2020, at a week to month intervals, from the surface layer, middle and lower water depth using a plankton net (mesh size: 20 µm) and Vandorn sampler (Fig. 1). All living materials were immediately examined, and after an initial examination, materials were fixed with 5% formalin for permanent preservation and detail identification. Microscopic examinations were conducted at a magnification of 400 to 630× using a Zeiss microscope (Axio Imager. A2; Carl Zeiss Microscopy GmbH, Göttingen, Germany), and photomicrographs were taken with an AxioCam HRC camera (Carl Zeiss). Species identification was performed using relevant literatures (Ciugulea and Triemer 2010; Huber-Pestalozzi 1955; Tell and Conforti 1986; Wolowski and Hindak 2005). Water quality parameters used data of the ministry of environmental (National Institute of Environmental Research, NIER) (Table 1).

Table 1 . Physico-chemical and hydrological parameters of the sampling sites from Nakdong River during the surveyed periods.

Sampling sitespHEC (uS/cm)TN (mg/L)NH3-N (mg/L)NO3-N (mg/L)TP (mg/L)PO4-P (mg/L)HRT (day)
St. 18.4246.12.4740.0691.8240.0410.0136.7–16.3
St. 28.1369.23.3230.1082.5610.0460.013
St. 38.3319.33.0650.0862.3740.0430.0133.7–6.1
St. 48.1353.43.2160.0902.3970.0440.0143.9–5.9
St. 57.9308.32.8540.0782.1720.0400.015
St. 67.9288.32.2980.0571.6770.0360.0103.8–5.4
St. 77.8283.12.5760.0551.9400.0350.012
St. 88.0275.12.5710.0611.9060.0390.014
St. 98.0272.92.5140.0651.8770.0390.015
St. 108.0268.42.5210.0961.8360.0360.012

Each environment variable value is presented as the mean.

EC: electrical conductivity; TN: total nitrogen; TP: total phosphorus; PO4-P: phosphate phosphorus; NO3-N: nitrate nitrogen; NH3-N: ammonium nitrogen; HRT: hydraulic retention time.


Environmental characteristics

Water environmental factors in the surveyed region presented in Table 1. The mean nutrients concentration for total nitrogen (TN), nitrate nitrogen (NO3-N), ammonium nitrogen (NH3-N), total phosphorus (TP), and phosphate phosphorus (PO4-P) appeared mesotrophic to eutrophic level. Hydraulic retention time was between 3.7–16.3 days and 15 days (mean 10 days).

Euglenophytes flora in Nakdong River

We observed Euglenophytes of 103 taxa from the middle-downstream section of Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, and were observed 3 taxa of Colacium, Euglena (5), Lepocinclis (20), Menoideum (1), Monomorphina (3), Phacus (17) and Strombomonas (14) (Table 2). A total of 22 taxa; Colacium (1); Lepocinclis (8); Phacus (4); Strombomonas (4) and Trachelomonas (5) were new to Korea. All of the species were illustrated with light-photomicrographs and briefly described with regarded to their taxonomy of the 22 taxa new to Korea (Figs. 2-135).

Table 2 . List of Euglenophytes species found in the Nakdong River.

List of speciesPrevious studyThis studyList of speciesPrevious studyThis study
Astasia lagenula+Trachelomonas abruptaa+
Colacium elongatumb+Trachelomonas alliaa+
Colacium simplexa+Trachelomonas armataa+
Colacium vesiculosuma+Trachelomonas armata var. steiniia+
Euglena desesa+Trachelomonas australica var. rectangularisb+
Euglena ehrenbergiia+Trachelomonas bacilliferaa+
Euglena gaumei+Trachelomonas cerviculaa+
Euglena gracilis+Trachelomonas cordata var. minora+
Euglena oblongaa+Trachelomonas cylindricaa+
Euglena proxima++Trachelomonas cylindrica var. decollate+
Euglena viridis+Trachelomonas dubiaa+
Euglena sp.+Trachelomonas dybowskiia+
Eutreptiella gymnastica+Trachelomonas hexangulata var. repandaa+
Lepocinclis acus++Trachelomonas hispida++
Lepocinclis acus var. hyalinab+Trachelomonas hispida var. coronataa+
Lepocinclis acus var. longissimab+Trachelomonas intermedia++
Lepocinclis constrictab+Trachelomonas klebsiia+
Lepocinclis fusiformisa+Trachelomonas lefevrei++
Lepocinclis fusiformis var. amphyrinchusb+Trachelomonas lemmermanniib+
Lepocinclis fusiformis var. majora+Trachelomonas mirabilis var. affinisa+
Lepocinclis globulus+Trachelomonas novab+
Lepocinclis gracilicaudaa+Trachelomonas oblonga++
Lepocinclis hungpanchiaoensisb+Trachelomonas oblonga var. australicaa+
Lepocinclis marsoniia+Trachelomonas pavlovskoensisa+
Lepocinclis ovum++Trachelomonas pavlovskoensis f. ellipsoideaa+
Lepocinclis ovum var. conicaa+Trachelomonas planctonica++
Lepocinclis ovum var. dimidio-minora+Trachelomonas planctonica var. oblongaa+
Lepocinclis ovum var. ovate+Trachelomonas playfairia+
Lepocinclis oxyuris++Trachelomonas pulcherimaa+
Lepocinclis playfairiana+Trachelomonas pulcherima var. minora+
Lepocinclis reeuwykiana var. kriegerib+Trachelomonas raciborskiia+
Lepocinclis salina++Trachelomonas similisa+
Lepocinclis spirogyrab+Trachelomonas stokesianaa+
Lepocinclis spirogyroidesa+Trachelomonas stokesiib+
Lepocinclis wangiib+Trachelomonas sydneyensis var. minimaa+
Menoidium pelluciduma+Trachelomonas variansa+
Monomophina nordstedtii++Trachelomonas varians var. globosaa+
Monomorphina pyruma+Trachelomonas verrucosa f. irregularisa+
Strombomonas verrucosa var. zmiewikab+Trachelomonas volvocina++
Strombomonas sp.+Trachelomonas woronichinianab+

aIndicates new records for Nakdong River, bindicates new records for Korea.


Figs. 2-15. (2) Colacium elongatum, (3) C. simplex, (4) C. vesiculosum, (5) E. deses, (6) E. ehrenbergii, (7) E. oblonga, (8) E. proxima, (9) E. sp., (10) Lepocinclis constricta, (11) L. conica, (12) L. ovum, (13) L. ovum var. dimidio-minor, (14) L. globulus, (15) L. steinii. Scale bars = 10 μm.

Taxonomic descriptions

Colacium elongatum Playfair (Fig. 2)

Ciugulea and Triemer 2010, p. 5; Huber-Pestalozzi 1955, p. 127, pl. 23, Figure 111.

Cell elongate cylindrical, attached by mucilaginous stalk, group into colonies; chloroplast numerous, disc shaped, with a pyrenoid, periplast fine striated. Cell length 15−30 µm, breadth 8−12 µm.

Lepocinclis acus var. hyalina (Klebs) D.A. Kapustin (Fig. 17)

Ciugulea and Triemer 2010. p. 67.

Figs. 16-29. (16) Lepocinclis acus, (17) L. acus var. hyalina, (18–20) L. acus var. longissima, (21) L. tripteris, (22) Phacus limnophila, (23) Menoideum pellucidum, (24) Lepocinclis caudata, (25) L. gracilicauda, (26) L. fusiformis, (27) L. fusiformis var. amphirhynchus, (28) L. fusiformis var. major, (29) L. hungpanchiaoensis. Scale bars = 10 μm.

Cell narrow, long cylindrical, colorless, rod-like paramylon. Anterior with contractile vacuole. Pellicle strips very fine. Cell length 120−140 µm, breadth 12−13 µm.

Lepocinclis acus var. longissima (Deflandre) D.A. Kapustin (Figs. 18-20)

Wolowski and Hindak 2005, Figures 9, 10.

Cell narrow, long cylindrical, rod-like paramylon. Anterior with eyespot and contractile vacuole. Longitudinal pellicle strips fine. Cell length 260−280 µm, breadth 10−12 µm.

Lepocinclis constricta Matvienko (Fig. 10)

Syn.: Euglena gymnodiniodes Zakrys

Wolowski and Hindak 2005, Figures 66, 67.

Figs. 66-77. (66) Phacus orbicularis, (67) P. platalea, (68) P. triqueter, (69) P. undulatus, (70) P. hamatus, (71) P. pleuronectes, (72) Strombomonas acuminata, (73–76) S. borystheniensis, (77) S. scauinslandii. Scale bars = 10 μm.

Cells gourd-shaped, broad fusiform to longitudinal hexagonal shaped constricted in the middle part of lateral sides; anterior end narrowly projected and truncate; posterior end broadly rounded, with a thin, long straight cauda; periplasts spirally striated; paramylon bodies numerous, globose to ovoid. Cell length 28−31 µm, breadth 14−16 µm, caudal length 8−9 µm.

Lepocinclis fusiformis var. amphyrinchus Nygaard (Fig. 27)

Yamagishi and Akiyama 1998, 20: 42.

Cells broad fusiformis, anterior end conically narrowed and projected into truncately rounded, apex shallowly bilobed; posterior ends conically produced into a short caudal process; lateral sides roundly swelled; periplasts spirally striated; paramylon two, large ring-like plate; chloroplast disc shaped. Cell length 34−38 µm, breadth 21−24 µm.

Lepocinclis hungpanchiaoensis Chu (Fig. 29)

Yamagishi and Akiyama 1995, 14: 32.

Cells broad ovoid, anterior end conically narrowed, shallow prominentally bilobed at one side just below the end; posterior ends gradually narrowed, with a short pointed cauda; lateral sides roundly swelled; periplasts spirally striated; paramylon two, ring-like plate. Cell length 44−47 µm, breadth 21−23 µm. This species only has been known from the east-north Asia (Japan and China).

Lepocinclis reeuwykiana var. kriegeri Conrad (Fig. 36)

Huber-Pestalozzi 1955, p. 147. pl. 28. Figure 140; Yamagishi and Akiyama 1995, 14: 33.

Figs. 30-38. (30, 31) Lepocinclis oxyuris, (32) L. spirogyroides, (33, 34) L. salina, (35) L. marssonii, (36) L. reeuwykiana var. kriegeri, (37) L. spirogyra, (38) L. wangii. Scale bars = 10 μm.

Cells long fusiform; anterior end narrowly produced and truncate, slightly depressed; posterior end gradually narrowed and projected into a long, straight cauda; periplasts spirally striated; paramylon bodies two, ring-like plate. Cell length 54−60 µm, breadth 11−13 µm.

Lepocinclis spirogyra Korschikov (Fig. 37)

Yamagishi and Akiyama 1989, 10: 49, Wolowski and Hindak 2005, Figures 259, 260.

Figs. 39-44. (39) Phacus elegans, (40, 41) P. longicauda, (42) P. helicoides, (43) P. ranula, (44) P. tortus. Scale bars = 10 μm.

Cells fusiform; anterior end slightly narrowed, rounded; posterior end projected into a straight, long cauda; periplasts left-handed striated by rows of small verruca; chloroplasts plate-shaped; paramylon bodies two, ring-like plate. Cell length 45−54 µm, breadth 20−23 µm, cauda 6-10 µm.

Lepocinclis wangii Chu (Fig. 38)

Yamagishi and Akiyama 1989, 10: 53.

Cells broad fusiform; anterior end conically narrowed, rounded, shallow prominently bilobed at just below the end, and one side produced into a beak-like process; posterior ends gradually narrowed in to a long, straight cauda; periplasts spirally striated; paramylon two, ring-like plate. Cell length 50−53 µm, breadth 25−30 µm, cauda 12−13 µm. This species only has been known from the east-north Asia (Japan and China).

Phacus anomalus F.E. Fritsch & M.F. Rich (Figs. 47, 48)

Huber-Pestalozzi 1955, p. 204. Figure 260; Yamagishi and Akiyama 1995, 14: 39.

Figs. 45-65. (45, 46) Phacus acuminatus, (47, 48) P. anomalus, (49) P. curvicauda, (50, 51) P. smulkowskianus, (52) P. inflexus, (53) P. cylindraceus, (54, 55) P. suecicus, (56) P. horridus, (57, 58) P. raciborskii, (59) P. glaber, (60) Monomorphina nordstedtii, (61–63) M. pyrum, (64, 65) M. trypanon. Scale bars = 10 μm.

Cells asymmetric ovoid to broad ellipsoid, with two distinct dissimilar halves-the one half large, thick, the other slightly smaller, thinner and slightly twisted; one face with a broad deep furrow, the other with a shallow one extending entirely, in vertical view asymmetric; anterior ends narrowed, asymmetrically rounded; posterior end broadly, truncately rounded, with a short, oblique cauda; lateral sides slightly swelled; periplasts longitudinally striated; paramylon bodies two, circular plate. Cell length 25−30 µm, breadth 20−22 µm.

Phacus cylindraceus T.G. Popova (Fig. 53)

Popova 1955, p. 213, pl. 86, Figure 11; Yamagishi and Akiyama 1995, 14: 42.

Cells small, long cylindrical to fusiform; anterior ends slightly narrowed, obliquely truncate, shallowly bilobed and one side projected; posterior end gradually narrowed into a obtuse projection; lateral sides nearly straight and parallel or slightly swelled at midregion; periplasts obliquely striated; paramylon bodies two, lod-like, one large and the other small. Cell length 22−25 µm, breadth 6−8 µm.

Phacus glaber (Deflandre) Pochmann (Fig. 59)

Huber-Pestalozzi 1955, p. 238, pl. 55, Figure 340; Ciugulea and Triemer 2010, p. 97, Figures A–C.

Cells broad ovoid to elliptic; anterior ends truncately rounded, slightly concave at center, with a median papilla; posterior end broadly rounded, with a straight or slightly curved cauda; periplasts longitudinally striated, without any granules or spines; paramylon bodies two, large, parietal disc-like plate. Cell length 45−50 µm, breadth 22−24 µm.

Phacus smulkowskianus (Zakrys) W.-H.Kusber (Figs. 50, 51)

Ciugulea and Triemer 2010, p. 121, Figures A–D.

Cells fusiform to long-ovoid, spirally twisted throughout their entire length, 1.5–2 turns; anterior end narrowed and truncate, with a central small papilla; posterior end tapering into a twisted, straight cauda; lateral margins undulated in side view; periplasts spirally striated; paramylon bodies two, circular or ovoidal plate, one large and the other small. Cell length 30−40 µm, breadth 15−18 µm.

Strombomonas australica (Playfair) Deflandre (Fig. 86)

Huber-Pestalozzi 1955, p. 391, pl. 81, Figure 851A.

Figs. 78-89. (78) Strombomonas urceolata, (79) S. verrucosa var. zmiewika, (80) S. napiformia var. brevicolis, (81) S. ovalis, (82, 83) S. triquetra, (84, 85) S. tetraptera, (86) S. australica, (87) S. gibberosa, (88) S. costata, (89) S. maxima. Scale bars = 10 μm.

Lorica long, slender fusiform; anterior ends gradually narrowed, with a long, cylindrical collar, collar mouth irregularly serrated; posterior ends gradually narrowed into a long, straight, conical cauda; wall rough, with irregularly scattered small granules. Lorica length 58−60 µm, breadth 18−20 µm, collar length 11 µm, diameter 6 µm, cauda length 12 µm.

Strombomonas borystehniensis (Roll) Popova (Figs. 73−76)

Syn.: Strombomonas verrucosa var. borystehniensis (Roll) Deflandre

Huber-Pestalozzi 1955, p. 371, pl. 77, Figure 793; Yamagishi and Akiyama 1994, 13: 75; Ciugulea and Triemer 2010. p. 128.

Lorica longer than broad, ellipsoid to ovoid; anterior ends with short collar, posterior ends rounded or slightly narrowed, with very short tail; periplast with many irregular granules; chloroplast numerous discoid. Lorica length 23−32 µm, breadth 18−23 µm.

Strombomonas tetraptera Balech & Dastugue (Figs. 84, 85)

Huber-Pestalozzi 1955, p. 391, pl. 81, Figure 851A.

Lorica twisted, fusiform to cylindrical in lateral view; quadrangular with concaved sides and rounded angular in vertical view; anterior ends slightly narrowed, with short and broad collar, mouth slightly irregular and oblique; posterior ends conically tapered into a short cauda; lateral sides longitudinally swelled or nearly straight and undulated for twisting of the periplast; wall rough, with irregularly scattered verrucae. Lorica length 37−40 µm, breadth 23−26 µm.

Strombomonas verrucosa var. zmiewika (Svirenko) Deflandre (Fig. 79)

Huber-Pestalozzi 1955, p. 370, pl. 77, Figure 791.

Lorica broad ellipsoid to ovoid; anterior end gradually narrowed into a short, broad, cylindric collar; posterior end abruptly narrowed, with a long straight, conical cauda; wall irregularly verrucose. Lorica length 40-45 µm, breadth 20−21 µm, neck length 4−5 µm, diameter 5 µm.

Trachelomonas australica var. rectangularis Deflandre (Figs. 112, 113)

Huber-Pestalozzi 1955, p. 304, pl. 65, Figure 561.

Figs. 90-116. (90) Trachelomonas oblonga, (91) T. oblonga var. australica, (92) T. cordata var. minor, (93) T. verrucosa f. irregularis, (94) T. stokesiana, (95) T. stokesii, (96) T. volvocina, (97, 98) T. woronichiniana, (99) T. acanthostoma var. minor, (100) T. intermedia, (101) T. cylindrica, (102) T. cylindrica var. decollata, (103) T. abrupta, (104) T. klebsii, (105, 106) T. nova, (107) T. cervicula, (108) T. varians, (109) T. varians f. globosa, (110, 111) T. lefevrei, (112, 113) T. australica var. rectangularis, (114) T. hispida, (115) T. hispida var. coronata, (116) T. mirabilis var. affinis. Scale bars = 10 μm.

Lorica broad cylindrical; anterior and posterior ends angularly rounded; lateral sides straight and parallel; flagella apertures without collar, but surrounded by a circle of spines; wall covered with short and sharp minute spines. Lorica length 29−31 µm, breadth 18−20 µm.

Trachelomonas lemmermannii Wolozynska (Figs. 132, 133)

Huber-Pestalozzi 1955, p. 321, pl. 69, Figure 637.

Figs. 117-135. (117) Trachelomonas armata, (118) T. armata var. steinii, (119) T. hexangulata var. repanda, (120) T. pavlovskoensis var. ellipsoidea, (121) T. pavlovskoensis, (122) T. allia, (123) T. raciborskii, (124) T. sydneyensis var. minima, (125) T. bacillifera var. minima, (126) T. planktonica, (127) T. planktonica var. oblonga, (128) T. playfairi, (129) T. similis, (130) T. dybowskii, (131) T. dubia, (132, 133) T. lemmermannii, (134) T. pulcherima, (135) T. pulcherima var. minor. Scale bars = 10 μm.

Lorica cylindrical; anterior ends truncately rounded; flagellum apertures without a collar; posterior ends narrowed into a short, broad conical apex; lateral sides straight and parallel; wall covered with many puncta. Lorica length 26−28 µm, breadth 12−13 µm.

Trachelomonas nova Drezepolski (Figs. 105, 106)

Huber-Pestalozzi 1955, p. 314, pl. 68, Figure 604.

Lorica obovoid; anterior ends slightly narrowed, rounded; posterior ends slightly, conically narrowed; flagellum apertures without a collar, but surrounded by a circle of spines; wall covered with short spines. Lorica length 23−25 µm, breadth 19−20 µm.

Trachelomonas stokesii Drezepolski (Fig. 95)

Huber-Pestalozzi 1955, p. 282, pl. 61, Figure 476.

Lorica obovoid; anterior ends rounded; posterior ends slightly narrowed and rounded; flagellum apertures without a collar; wall finely punctate. Lorica length 14−15 µm, breadth 12−13 µm.

The present study found that phytoplankton communities of the Nakdong River showed a high species diversity (total 769 taxa, unpublished), investigating a total of 103 taxa of Euglenophytes at the middle-lower part of the Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, followed Lepocinclis (20), Phacus (17), Strombomonas (14), Euglena (5), Colacium (3), Monomorphina (3) and Menoideum (1). Among them, a total of 22 taxa including Colacium (1), Lepocinclis (8), Phacus (4), Strombomonas (4) and Trachelomonas (5) were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River. Meanwhile, 12 taxa including Astasia lagenula, Phacus caudatus, Strombomonas girardiana recorded in the previous studies were not observed in this research. Most of the euglenoids species observed in the Nakdong River are known to prefer to small and organically polluted eutrophic environments (Munawar 1972; Padisak et al. 2009; Reynolds et al. 2002; Tell and Conforti 1986; Wolowski and Walne 2007). The highest species diversity of Euglenophytes was observed during summer, especially in July where water temperatures remain high after heavy rain. It is assumed that the species were introduced from small swamps formed on the riverside by heavy rain during summer.

Many floristic and taxonomic studies on euglenophytes have been done across various regions in lentic waterbodies such as swamps, reservoirs and ponds in South Korea (Chung 1975; Chung and Chang 1957; Chung and Kim 1992; Chung and Kim 1993; Conforti and Ruiz 2001; Conforti and Ruiz 2002; Kim 2013c; Kim and Boo 1998; Kim et al. 1998; Kim et al. 2000a; Kim et al. 2000b; Wui and Kim 1987). Over 340 taxa of Euglenophytes have been recorded in Korea (Lee and Kim 2015; Kim 2018). Thirty taxa of Euglenophytes have been found in the main stream section of the Nakdong River (Cho et al. 1993; Choi et al. 2007; Chung et al. 1994; Chung et al. 2000; Chung et al. 2013; Kim and Lee 1991; Seo and Chung 1994).

Also, a great deal of studies have been done on phytoplankton communities in lotic environments of the four major rivers including the Han River and the Nakdong River (Cho et al. 1993; Choi et al. 2007; Chung et al. 1965; Chung et al. 1968; Chung et al. 1994; Chung et al. 2000; Chung et al. 2013; Jeong et al. 2010; Jung et al. 2003; Kim 2003; Kim 2004; Kim and Boo 1996; Kim and Lee 1991; Lee and Chang 1997; Lee and Jung 2004; Lee et al. 2002; Seo and Chung 1994; Son 2013). The total number of phytoplankton species in these lotic river ecosystems varies significantly from 72 taxa to 466 taxa depending on researchers. Also, the species richness of euglenophytes showed a significant difference from 0 to 36 taxa according to researchers (Table 3). It is estimated that the great differences in phytoplankton composition in similar habitats come mainly from different volumes of literature materials, depth of taxonomic knowledge among researchers, research periods and sampling times rather than from differences in practical phytoplankton communities.

Table 3 . Composition of the Euglenophytes of the Nakdong River and another lentic and lotic waters for different periods in South Korea.

ReferencesSiteSampling periodEug. Sp. NumberComposition ratio (%)Tot. Sp. Number
This studyNR2018–202010313.4769 (include Diatoms)
Kim and Lee (1991)NR1988–198942197 (include Diatoms)
Cho et al. (1993)NR1991–199231.3227 (include Diatoms)
Chung et al. (1994)NR19932411.9201 (exclude Diatoms)
Seo and Chung (1994)NR1992–19939186 (include Diatoms)
Kim (2004)NR1995–199636 (no list)7.9456 (include Diatoms)
Lee et al. (2002)NR2000–2001Unknown(include as others)239 (include Diatoms)
Chung et al. (2013)NR1983–2004303.7817 (include Diatoms)
Son (2013)NR2012Unknown(include as others)72 (include Diatoms)
Park et al. (1995)KHR1990–19913115.3203 (exclude Diatoms)
Lee and Chang (1997)HR1995–199632.1145 (include Diatoms)
Jung et al. (2003)HR2001–2002103.7267 (include Diatoms)
Lee and Jung (2004)HR1945–2004123.7332 (include Diatoms)
Kim and Boo (1996)KR1994–199637Only Euglenoid
Jeong et al. (2010)YR2004–2005Unknown(include as others)265 (include Diatoms)
Kim (2003)YR1995–199663 (no list)13.5466 (include Diatoms)
Kim and Chung (1993b)Tchokjibul S.1990–19918027.4292 (exclude Diatoms)
Sajipo S.1990–19919731.2311 (exclude Diatoms)
Kim (2001)Woopo S.19986418.1353 (include Diatoms)
Conforti and Ruiz (2001), Conforti and Ruiz (2002)Chunam R.199196Only Euglenoid
Kim (2018)Cheonjin L20174913.1376 (exclude Diatoms)

NR: Nakdong River; HR: Han River; KR: Kum River; YR: Youngsan River; KHR: Kumho River; S.: Swamp; R.: Reserver; L.: Lake; Eug. Sp.: Euglenophytes Spcies; Tot. Sp.: Total species.



The phytoplankton communities of the Nakdong River after the weir construction significantly changed compared to before they were built. In particular, the total number of all species including Euglenophytes as well as the total amount of biomass saw a remarkable increase. The Euglenophytes community at the middle-lower part of the Nakdong River is similar to that in lentic waterbodies such as shallow eutrophic reservoirs and swamps given the high species diversity and composition ratio (Conforti and Ruiz 2001; Conforti and Ruiz 2002; Kim 2001; Kim and Chung 1993a; Kim and Chung 1993b) (Table 3). The results suggest that water environments in the middle-lower section of the Nakdong River is changing to resemble lentic ecosystems such as swamps and reservoirs given the increasing retention time and nutrient concentration following the construction of the weirs.

The present study, a total of 103 taxa of Euglenophytes were found from middle-lower part of the Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, followed Lepocinclis (20), Phacus (17), Strombomonas (14), Euglena (5), Colacium (3), Monomorphina (3) and Menoideum (1). Among them, a total of 22 taxa including Colacium (1), Lepocinclis (8), Phacus (4), Strombomonas (4) and Trachelomonas (5) were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River.

Syn.: Synonym

Var.: Variety

Fiig.: Fiigure

EC: Electrical conductivity

TN: Total nitrogen

TP: Total phosphorus

PO4-P: Phosphate phosphorus

NO3-N: Nitrate nitrogen

NH3-N: Ammonium nitrogen

HRT: Hydraulic retention time

HSK designed this study and wrote the manuscript. HSK and JHL participated in field works and reviewed/edited the manuscript. All authors read and approved the final manuscript.

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