Journal 
INTRODUCTION
Coasts and estuaries, boundaries between seas and continents, are ecosystem transition areas, with large geomorphic changes and diverse breeding grounds for living organisms (Elliott and Quintino 2007). Overall, species diversity of biological organisms is higher in coastal areas than in ocean or inland waters, and diatoms are no exception, as recent studies have revealed that diatom community structure and diversity are influenced by geographical factors independent of environmental conditions (Eichbaum et al. 1996; Vanormelingen et al. 2008).
The estuary of the Nakdong River is a place where biodiversity is high due to diverse environmental factors and complicated topographical conditions as estuaries, and diatoms are highly diverse in comparison with other regions (Du et al. 2009). More than 350 species of benthic diatoms were already reported in estuarine sediments of the river (Cho 1988).
As a deep and simple coastline, Yeongil Bay is rich in seagrass and is also a place where there are many diatoms related to seagrasses. A number of diatom species were listed in the Environmental Impact Assessment (EIA) conducted 1991-1993 at Yeongil Bay (Cho 1993). EIA was conducted when coastal area of the bay was reclaimed with burial of steel slag, produced by POSCO (Pohang Iron and Steel Corporation).
Previous studies on diatoms in the estuary of Nakdong River have been conducted on plankton in estuarine lakes, and on benthic diatoms in sandy sediments. There were studies on distributions of planktonic diatoms in the estuarine lake (Kim and Lee 1991; Cho et al. 1993). In intertidal sandflats, distribution of benthic diatom on the surface (Cho 1988; Du et al. 2009) and distribution along the depth of sediment layer (Du et al. 2010) were studied. On the other hand, taxonomic studies were conducted recently on diatom species belonging to genus Navicula and Hantzschia (Joh 2013, 2014).
This study extends the diatom species diversity and reduces the number of unrecorded species in the local area. It was conducted as part of a national task, “The Project on Survey and Excavation of Korean Indigenous Species”, supported by the National Institute of Biological Resources (NIBR) under the Ministry of Environment of Korea. The purpose of this study is to find unrecorded species of diatoms, not reported in Korea, at the Nakdong estuary and Yeongil Bay.
MATERIALS AND METHODS
For the study of diatoms, materials were collected from sediments of intertidal sandflats in the Nakdong River Estuary in Busan, and from seagrass and rock in the Yeongil Bay in Pohang (Fig. 1). Benthic diatoms in the estuary were collected four times in the past in 1986, 1991, 2007 and 2013, and materials were taken from 7 sampling sites. In Yeongil Bay, periphytic diatoms were collected from seagrasses and rock in the process of the EIA 1991-1993.
Materials containing diatoms were oxidized using nitric acid and potassium dichromate in hot sand-bath, followed by repeated washing with distilled water (APHA 1995). Permanent specimens of slide glasses were made using Pleurax medium and diatoms were observed and counted by using two types of light microscopes, including an Olympus microscope (Provis AX2; Olympus, Tokyo, Japan), equipped with differential interference contrast (DIC) optics and an Axioplan microscope (Carl Zeiss, Oberkochen, Germany). Diatom frustules were counted 300-350 for each sample to determine frequency and abundance of each species. Many literatures were referred in identifying diatoms and recording taxonomic accounts of species (Cleve-Euler 1952; Krammer and Lange-Bertalot 1986; Witkowski et al. 2000).
RESULTS AND DISCUSSION
Benthic and periphytic diatoms were collected from sediments in the estuarine area of the Nakdong River, and seagrasses and rocks in Yeongil Bay. Selected diatoms are examined based on light microscopy observation and important characters, valve outlines, shapes of valve ends, a number of striae and areola density, and shape of axial and central areas. Morphology of the girdle is an additional character. Morphological characteristics that can be obtained from light microscopy are used to validate diatoms to species level. In this survey, 18 species are identified as unrecorded ones that have never been reported in Korea, however, many diatoms still remain as unresolved ones in the identification. The 18 species were found as new reports to Korea and the basic morphological characters are included in each description. Four genera, Hyalinella, Martyana, Trachysphenia and Nagumoea, are described for the first times in the floristic survey of diatoms.
In this study, 18 diatom species representing 8 genera are newly recorded in Korea. Twelve species occurred in sandy sediments of the Nakdong River Estuary, four species in Yeongil Bay, and two species in both regions. Of the 18 species, 8 are araphid diatoms, 10 are biraphid diatoms.
Genus Fragilaria Lyngbye 1819
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1. Fragilaria cassubicaWitkowski & Lange-Bertalot 1993 (Pl. 1, Figs. 1-5) (Witkowski and Lange-Bertalot 1993, p. 64, Fig. 4a-m; Witkowski et al. 2000, p. 49, Pl. 24, Figs. 28-31)
Synonym:Fragilaria subsalina (Grunow) Lange-Bertalot in Krammer and Lange-Bertalot 1991 (Krammer and Lange- Bertalot 1991, p. 138, Pl. 127, Figs. 9-16, Pl. 118, Fig. 17).
Valves linear-elliptical in outline, but clavately heteropolar with obtusely rounded head and elongated tail, 12-20 μm long, 3-4 μm broad. Frustules in girdle view rectangular to wedge-shaped. Axial area very narrow and linear. Transapical striae parallel throughout the valve, 15-18 rows in 10 μm.
This is widespread on sandy sediments of coastal areas globally (Witkowski et al. 2000). The species occurred rarely on sandflats of the Nakdong River Estuary and on rocks in Yeongil Bay in Pohang, and is newly recorded in Korea.
Genus Hyalinella Witkowski, Lange-Bertalot & Metzeltin 2000
Valves linear to elliptical, ends of the valve rounded. Valve face flat, mantle of the valve deep with a row of large punctas. Frustule structureless and hyaline in LM and SEM. Frustules in girdle view rectangular with rounded corner, the girdle composed of several open bands.
The genus is linked to genus Pteroncola, but largely different in the morphology of the valve and mantle. Pteroncola has ornamented valve, large pore fields, two rimoportulae and the first girdle band, but Hyalinella has not all these features (Witkowski et al. 2000).
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2. Hyalinella lateripunctata Witkowski, Lange- Bertalot & Metzeltin 2000 (Pl. 1, Figs. 18-27) (Witkowski et al. 2000, p. 60, Pl. 32, Figs. 6-18)
Valves linear to weakly elliptical in outline with rounded ends, 2.5-31 μm long, 2-2.5 μm broad. Frustules in girdle view rectangular, but sinuous in large forms and square in small forms. Valve face flat and connected to deep mantle, marked with a row of large punctas. Exterior surface of the frustule hyaline without sculpture.
Species was found abundantly in the Baltic Sea and in fossil sediments, probably cosmopolitan in marine environments, but often overlooked or misidentified with Pteroncola inane (Witkowski et al. 2000). Species occurred eiphytons in sandflats of the Nakdong River Estuary and in seagrasses of Yeongil Bay in Pohang, particularly abundant in sargas sum seagrass of the bay. Valve lengths of local specimens are longer than those (6-16.5 μm) designated by Witkowski et al. (2000). Species is newly recorded in Korea.
Genus Licmophora Agardh 1827
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3. Licmophora gracilis var. anglica (Kützing) H. Peragallo & M. Peragallo 1901 (Pl. 1, Figs. 36-39) (Hustedt 1931, p. 60, Fig. 583; Witkowski et al. 2000, p. 65, Pl. 20, Figs. 11-13)
Basionym:Rhipidophora anglicaKützing 1844.
Valves strongly clavate with circular or broadly rounded head and elongated rostrate tail, 31-37 μm long, 9-10 μm broad. Axial linear and narrow, Transapical striae finely punctate, parallel throughout the valve, 24 rows in 10 μm.
This is common in the coastal area up to the Arctic area (Witkowski et al. 2000). Species occurred as periphytons on rocks of Yeongil Bay in Pohang, and newly recorded in Korea. Local specimens are small, compared to 20-120 μm designated by Witkowski et al. (2000).
Genus Martyana Round in Round, Crawford and Mann 1990
Cells ovate in valve view and oblong to wedge-shaped in girdle view, but more or less isopolar in small forms. The marginal spines of valve lacking and not forming linear colonies. Coarse, slit-like areolae parallel to the apical axis. Narrow, approximately linear axial area and no central area.
The genus Martyana is a freshwater taxon and was erected from largely marine genus Opephora.
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4. Martyana atomus (Hustedt) Snoeijs in Snoeijs, Hallfors and Liskinen 1991 (Pl. 1, Fig. 6) (Snoeijs et al. 1991, p. 166, Figs. 1-18, 23-25)
Basionym:Fragilaria atomusHustedt 1931 (Witkowski et al. 2000, p. 47, Pl. 24, Figs. 32-39).
Valves broadly elliptical in outline, but heteropolar and clavate, and small 6 μm long, 2.8 μm broad. Axial area narrowly linear, but indistinct, transapical striae parallel throughout the valve, 22 rows in 10 μm.
This is widespread in sandy sediments of the coastal area from the Arctic area to subtropical areas (Witkowski et al. 2000). Species are very rare in sandflats of the Nakdong River Estuary, and is newly recorded in Korea.
Genus PseudostaurosiraWilliams & Round 1987
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5. Pseudostaurosira perminuta (Grunow) Sabbe & Vyverman 1995 (Pl. 1, Figs. 7-12) (Sabbe and Vyverman 1995, p. 237, Figs. 1-12; Witkowski et al. 2000, p. 76, Pl. 25, Figs. 35-37)
Basionym:Sceptroneis marina var. perminuta Grunow in Van Heurck 1881.
Synonym: (?)Fragilaria neoellipticaWitkowski 1994.
Valves ovate to clavate in outline, heteropolar with obtusely rounded head and cuneate tail, 5.5-14 μm long, 2- 3.2 μm broad. Frustules in girdle view rectangular, forming small colonial chain with the marginal spines. Axial area linear to broadly lanceolate, transapical striae parallel throughout the valve, 13-14 rows in 10 μm.
This is widespread in brackish waters of Europe (Witkowski et al. 2000). Species occurred in sandflats of the Nakdong River Estuary, and is newly reported in Korea. Fragilaria neoelliptica is a synonym of Pseudostaurosira perminuta by Sabbe and Vyverman (1995) and Witkowski et al. (2000), but Morales (2002) suggested differences between the two species, in valve outlines and forms of closing plate of areola under SEM observations.
Genus Tabularia (Kützing) Williams & Round 1986
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6. Tabularia investiens (W. Smith) Williams & Round 1986 (Pl. 1, Figs. 28-35) (Williams and Round 1986, p. 324, Figs. 39-45)
Basionym:Synedra investiens W. Smith 1856.
Synonym:Fragilaria investiens (W. Smith) Cleve-Euler 1953 (Krammer and Lange-Bertalot 1991, p. 151, Pl. 136, Figs. 12-13; Witkowski et al. 2000, p. 51, Pl. 30, Figs. 15- 19).
Valves elongated, linear to weakly lanceolate in outline, rarely slightly heteroploar, ends of the valve cuneately rounded, 22.5-70 μm long, 2.9-4 μm broad. Axial area variable, linear to broadly lanceolate, transapical striae more or less shortened, parallel throughout the valve, 8-10 rows in 10 μm.Plate 1
This is frequent and common as epiphytons in marine coasts (Witkowski et al. 2000). Species was important in epiphytic diatoms attached to seagrasses in Yeongil Bay in Pohang, and newly reported in Korea.
Genus TrachyspheniaPetit 1877 (Zalat 2001)
Valve elongate in outline, heteropolar and asymmetrical transapically, but variable forms, from linear-lanceolate, rhombic-lanceolate or ovate, ends of the valve broadly to acutely rounded to rostrate head-end and tapered foot-end. The raphe sternum indistinct, transapical striae uniseriate and the punctas of the striae coarse. Frustules solitary or forming short chains.
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7. Trachysphenia acuminata M. Peragallo in Tempère and Peragallo 1910 (Pl. 1, Figs. 16, 17) (Tempère and Peragallo 1910, p. 216, No. 401-402; Witkowski et al. 2000, p. 84, Pl. 24, Figs. 17-19)
Valves broadly elliptical to rhombical in outline, ends of the valve protracted and rostrate, 16 μm long, 4.5 μm broad. Axial area narrow, linear to lanceolate, transapical striae punctate, 12 rows in 10 μm.
This was reported from Atlantic coasts of the U.S. and from Mediterranean Coast (Witkowski et al. 2000), but less common, not abundant. Species was found in a sandflat of the Nakdong River Estuary, and is newly recorded in Korea.
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8. Trachysphenia australisPetit 1877 (Pl. 1, Figs. 13-15) (Petit 1877, p. 190, Pl. 5, Fig. 19a-d; Witkowski et al. 2000, p. 84, Pl. 21, Figs. 14-16, 61)
Valves ovate to clavate in outline with obtusely rounded head and acutely rounded tail, 15.5-27.5 μm long, 4.5- 7.5 μm broad. Axial area narrow, linear, transapical striae coarsely punctate and occasionally alternating along the axial area, 7 rows in 10 μm.
This is common and widespread in the marine coastal area. Species occurred rarely in a sandflat of the Nakdong River estuary, and newly reported in Korea. Sizes of local specimens are much smaller than 30-40 μm designated by Witkowski et al. (2000).
Genus Fallacia Stickle & D.G. Mann in Round, Crawford and Mann 1990
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9. Fallacia clipeiformis (König) D.G. Mann in Round, Crawford and Mann 1990 (Pl. 3, Figs. 22, 23)
Basionym:Navicula clipeiformisKönig 1959 (Hustedt 1964, p. 552, Fig. 1589; Podzorski and Håkansson 1987, p. 76, Pl. 31, Fig. 9).
Valves broadly elliptical in outline, 15.5-21.5 μm long, 10-12 μm broad. Raphe straight, central ends of the raphe distant each other, axial area broadly lanceolate, central area rectangularly developed, a lyre-shaped hyaline area on the both side of the axial area. Transapical striae 16-18 in 10 μm in the middle, 23-23 in 10 μm towards the ends of the valve, striae distinctly punctuate.
Species was observed rarely in coastal areas, Songjeong, near the Sonakdong River Estuary, and is newly reported in Korea.
Genus Amphora Ehrenberg ex Kützing 1844
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10. Amphora graeffeanaHendey 1973 (Pl. 2, Figs. 17-19) (Hendey 1973, p. 317, Figs. 12-19; Podzorski and Håkansson 1987, p. 51, Pl. 16, Figs. 1-2, 5, Pl. 51, Figs. 1-3; Witkowski et al. 2000, p. 138, Pl. 166, Fig. 24, Pl. 172, Figs. 6-9)
Synonym:Amphora graeffeiCleve 1895; non Amphora graeffei Grunow in A. Schmidt et al. 1875 (Schmidt et al. 1875, Pl. 25, Fig. 42).
Valves semi-elliptical to elliptic-lanceolate and moderately dorsiventral, dorsal margin moderately arched, ventral margin nearly straight, central parts of the ventral margin slightly swollen. Raphe slightly biarcuate, axial area in the dorsal side wider than in the ventral side, central area not differentiated. Transapical striae on the dorsal side crossed by a longitudinal hyaline line in the margin, 19-20 rows in 10 μm in the middle, 22 rows in 10 μm in the ends, on the ventral side absent or present only towards ends.
This is widespread in the coastal area of the Atlantic and Indian Oceans (Witkowski et al. 2000). Species occurred rarely in the sandflats of the Nakdong River Estuary, and newly recorded in Korea.
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11. Amphora jostesorum Witkowski, Metzeltin & Lange-Bertalot in Witkowski, Lange-Bertalot and Metzeltin 2000 (Pl. 2, Figs. 1-5) (Witkowski et al. 2000, p. 141, Pl. 171, Figs. 1-9)
Valves semi-lanceolate and slightly dorsiventral, dorsal margin weakly arched, central parts of the ventral margin slightly swollen, ends of the valve slightly produced and acute. Raphe slightly biarcuate, axial area narrow, central area not differentiated. Transapical striae on the dorsal side invisible in LM, 43 rows 10 μm in the middle.
Only known from type locality, Qurum Beach of Oman and another one, the Mississippi Delta (Witkowski et al. 2000). Species was found rarely in sandy sediments of the Nakdong River Estuary, and is newly recorded in Korea.
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12. Amphora ostrearia var. vitrea (Cleve) Cleve 1895 (Pl. 2, Figs. 10, 11) (Hendey 1964, p. 267, Pl. 38, Fig. 11; Podzorski and Håkansson 1987, p. 51, Pl. 16, Figs. 1-2, 5, Pl. 51, Figs. 1-3)
Basionym:Amphora vitreaCleve 1868.
Synonym:Amphora vitreaCleve 1868.
Valves semi-elliptical and moderately dorsiventral, dorsal margin arched, ventral margin slightly convex, ends of the valve acute, 33.5-43 μm long, 6-9.5 μm broad. Raphe biarcuate, axial area in the dorsal side very narrow, central area on the dorsal side extended transversely into a narrow, hyaline fascia. Transapical striae on the dorsal side coarsely punctate, parallel, 11-14 rows in 10 μm in the middle.
This is widespread in marine coastal areas such as Amphora ostrearia Brébisson, and particularly associated with sandy sediments (Hendey 1964). Species occurred rarely on sandflats of the Nakdong River Estuary, and is newly recorded in Korea.
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13. Amphora wisei (Salah) Simonsen 1962 (Pl. 2, Figs. 6-9) (Witkowski et al. 2000, p. 154, Pl. 162, Figs. 18, 19)
Basionym:Amphora turgida var. wiseiSalah 1955.
Valves semi-lanceolate and moderately dorsiventral, dorsal margin arched, ventral margin slightly convex, ends of the valve rostrately protracted. Raphe very close to the ventral margin, axial area in the dorsal side very narrow, central area not developed. Transapical striae on the dorsal side, 18-20 rows in 10 μm in the middle.
This is frequently common in marine coasts worldwide. Species occurred rarely in the sandflats of the Nakdong River Estuary, and is newly recorded in Korea.
Genus Halamphora (Cleve) Levkov 2009 (Spaulding 2011)
Valve dorsiventral, interface of the valve face and margin gradual or smooth without distinct marginal ridge, valve mantle deep on the dorsal margin, but shallow on the ventral margin. A raphe ledge (flap) present on dorsal side of the raphe. A central hyaline area, fascia, mostly absent. Central raphe ends straight or dorsally deflected. Chloroplasts centrally constricted and H-shaped.
A raphe ledge is present on both sides of the raphe in the genus Amphora s.s., but mostly restricted to dorsal side of the raphe in Halamphora. The genus Halamphora further differs from Amphora in areola by simple or covered areolae. Halamphora was originally erected by Cleve (1895) as a subgenus of Amphora and recently elevated to a genus (Levkov 2009). Most of the species within diatoms of the genus Halamphora occur primarily in marine or brackish waters.
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14. Halamphora eunotia (Cleve) Levkov 2009 (Pl. 2, Figs. 12-14) (Levkov 2009, p. 187, Pl. 92, Figs. 1-12, Pl. 243, Figs. 1-4)
Basionym:Amphora eunotiaCleve 1873 (Witkowski et al. 2000, p. 137, Pl. 165, Fig. 14, Pl. 167, Fig. 4).
Valves semi-lanceolate and slightly dorsiventral, dorsal margin slightly arched, ventral margin straight, ends of the valve slightly obtusely produced, 60.5-62 μm long, 7-8.5 μm broad. Raphe nearly straight, axial area in the dorsal side very narrow, central area only in the ventral side. Transapical striae on the dorsal side, 10-11 rows in 10 μm in the middle, a row of punctas on margin of the ventral side, 11- 13 punctas in 10 μm.
Species occurred in sandy sediments of the Nakdong River Estuary as marine and brackish-water species, and is newly reported in Korea.
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15. Halamphora lineata (Gregory) Levkov 2009 (Pl. 2, Figs. 15, 16)
Basionym:Amphora lineataGregory 1857 (Hendey 1964, p. 266, Pl. 38, Fig. 5; Podzorski and Håkansson. 1987, p. 51, Pl. 16, Figs. 1, 2, 5, Pl. 51, Figs. 1-3).Plate 2
Valves linear to semi-lanceolate and slightly dorsiventral, dorsal margin slightly arched, ventral margin straight, ends of the valve slightly obtusely or rostrately protracted. Raphe nearly straight close to the ventral margin, axial area in the dorsal side absent, central area only in the ventral side. Transapical striae on the dorsal side, 12.5-14 rows in 10 μm in the middle, 18 rows in 10 μm in the ends, a row of punctas on the margin of the ventral side.
Species occurred in a few localities, Lamlash Bay in Scotland as a type locality (Gregory 1857), Palawan Island of the Philippines (Podzorski and Håkansson 1987), and Langkawi Island of Malaysia (Salleh et al. 2005). This was found in the Nakdong River Estuary, and newly reported in Korea.
Genus Gomphoseptatum Medlin in Medlin and Round 1986
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16. Gomphoseptatum aestuarii (Cleve) Medlin in Medlin and Round 1986 (Pl. 3, Figs. 12-19) (Medlin and Round 1986, p. 212, Figs. 16-18; Witkowski et al. 2000, p. 222, Pl. 61, Figs. 17, 18)
Basionym:Gomphonema aestuariiCleve 1893.
Valves linear-lanceolate in outline, but slightly clavate with obtusely rounded ends, 13.8-22.5 μm long, 2.5-2.8 μm broad. Raphe straight, central ends of the raphe expanded and distant each other. Axial area narrow, hyaline central area transversely reaching up to the valve margins, transapical striae more or less parallel, punctate, crossed by a longitudinal rib running between raphe and the valve margin, 17-18 rows in 10 μm.
This is frequent and common in marine coasts preferring cold waters (Witkowski et al. 2000). Species was recorded in a coastal area of Gangneung (Lee et al. 2012), and occurred abundantly as epiphytons on seagrasses in Yeongil Bay.
Genus NitzschiaHassall 1845
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17. Nitzschia compositaGiffen 1971 (Pl. 3, Figs. 20, 21) (Giffen 1971, p. 8, Figs. 42, 43; Witkowski et al. 2000, p. 376, Pl. 211, Fig. 12)
Valves lanceolate in outline, ends of the valve broadly rostrate, 47-49 μm long, 5-5.5 μm broad. Raphe eccentric, transapical striae very delicate, 20 rows in 10 μm, fibulae 10-12 rows in 10 μm.
It is a known marine species from South Africa, Namibia and Yemen (Witkowski et al. 2000). Species was found very rarely in seagrass of Yeongil Bay, and is newly recorded in Korea.
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18. Nitzschia littorea Grunow in Van Heurck 1881 (Pl. 3, Figs. 24-28) (Krammer and Lange-Bertalot 1988, p. 67, Pl. 54, Figs. 1-3A; Witkowski et al. 2000, p. 391, Pl. 197, Figs. 15, 16)
Synonym:Nitzschia fogediMøller 1950.
Valves linear-lanceolate in outline, margins of the valve constricted in the middle, the ends of the valve cuneate, rostrate and slightly capitate, 64.5-84 μm long, 4-6 μm broad. Raphe eccentric, fibulae unevenly distant, 6.5-10 rows in 10 μm, transapical striae punctate, 26-28 rows in 10 μm.
This is common in marine coasts of Europe (Witkowski et al. 2000). Species occurred in sandflats of the Nakdong River estuary, and is newly recorded in Korea. Striae of local specimens is coarser (26-28 rows in 10 μm) than the designated data (30 rows in 10 μm).
Genus Nagumoea Witkowski in Witkowski, Kociolek and Kurzydlowski 2011
Valves linear to lanceolate in outlines. Marginal fibulae and portules of the valve robust and strong, raphe canalformed, but no elevated keel on the external valve face.
The genus Nagumoea was erected from the genus Denticula by Witkowski et al. (2011). In the comparison with Denticula, Nagumoea lacks in marginal keel of the valve, and has completely different raphe structure.
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19. Nagumoea neritica Witkowski & Kociolek in Witkowski, Kociolek and Kurzydlowski 2011 (Pl. 3, Figs. 1-11) (Witkowski et al. 2011, p. 173, Figs. 40-66, 95-96)
Basionym:Denticula neritica Holmes & Croll 1982 (Witkowski et al. 2000. p. 358, Pl. 216, Figs. 10-15).
Valves linear to narrowly lanceolate, 4.8-10.2 μm long, 1.5-1.8 μm broad. Raphe straight, transapical striae not discernible in LM, 41-51 rows in 10 μm in SEM, fibulae 5-7 in 10 μm.Plate 3
It was observed in feathers of diving birds and in sediments of the coastal areas (Witkowski et al. 2000). Species was found in seagrasses of Yeongil Bay, and is newly recorded in Korea.
