All samples were collected using 10 μm or 20μm mesh-sized plankton nets with vertical and/or horizontal towing, or submerged benthic or soil algae with spoid or brush. Sampling stations were located throughout the country. The samples of Chlorococcal algae were collected at 33 stations including ponds, swamp, reservoirs, lakes and rivers from May 2009 to April 2013 ( Table 1). Herein I presented the detailed taxonomic information, illustrations, classification, references, synonyms, basionyms and distribution in Korea. The purpose of this study was to newly record some taxa of the families Hydrodictyaceae and Coelastraceae, order Chlorococcales, and class Chlorophyceae representing 5 genera and 46 taxa from the swamps, ponds, reservoirs, lakes and rivers in Korea (Table 1). The genus Ducelleria was not recorded in this study.
The reported taxa belonging to the family Hydrodictyaceae and Coelastraceae in Korea represent 6 genera and 49 taxa, which include the genus Pediastrum (30 taxa), Sorastrum (3taxa), Hydrodictyon (1 taxon), Coelastrum (9 taxa), Actinastrum (1 taxon) and Ducelleria (1 taxon). The family Coelastraceae is also a coccal green algae, which is arranged 3 dimensionally and is spherical (e.g., genus Coelastraceae) or radiating from a center (e.g., genus Actinastrum). The genera Pediastrum and Sorastrum belong to a family that is characterized by the formation of coenobia, which are composed of a characteristic arrangement of cells, morphology of cells, and particular sculptures on the outer cell wall (Komarek and Jankovska 2001). However, the Hydrodictyon species form a net and are benthos. The family Hydrodictyaceae includes coccal green algae, which have microscopic, flat, spherical and circular coenobium. Subsequently, Korean florists reported previously the unreported freshwater algae in Korea from reservoirs, dam lakes, hot springs and other area (Chung and Chang 1957, Kim and Chang 1958, Chung 1968, 1974, 1978, 1981, Chung and Kim 1991, 1992, Chung et al. Previous studies on the flora and taxonomy of freshwater algae in Korea were conducted by a few foreign scholars (Kawamura 1918, Skvortzow 1929, 1932, Yamaguchi 1941, Ueno 1942, Emoto and Hirose 1942, Yamamoto 1941). Ueno (1940) investigated and reported the taxa in Lake Bujeon, swamp Daetaek, the Aprok river, the upper reach of Namdaecheon stream and Jooeul hot springs. Since then, 58 taxa including 1 new species and 1 new variety from Lake Suwon Seoho have been reported by Skvortzow (1929). He first reported the genus Cenritractus in Lake Suwon Seoho. Studies of freshwater algae in Korea were begun by Kawamura (1918). Thus, they play an important role in the primary and secondary successional processes (John and Tsarenko 2002). From the spring to fall, in particular, their reproduction is extensive such that they impart a green vegetation-like color to the water (Hindak 1977). They occur in the plankton and benthos of mesotrophic or eutrophic waters, and are the most diverse with the highest abundance. Chlorococcal algae are mostly unicellular or may form colonies of a definite shape (Prescott 1962).
The Chlorococcales are a large number of species, which are predominantly aquatic system and have the widest distribution among the Chlorophyceae.
Green algae comprise 7 orders (i.e., Volvocales, Tetrasporales, Chlorococcales, Microsporales, Chaetophorales, Oedogoniales and Zygnematales), but one of the orders, Zygnematales is separated into the Class Zygnematophyceae from Chlorophyceae by some researchers (Round 1971, Kenrick and Crane 1997). They are closely related to the higher plants in phylogenetic, which have similar structures in their chloroplasts, and photosynthetic pigments (chlorophyll-a, b and carotenoids) and store of starch (e.g., pyrenoid).
The freshwater green algae have great diversity in their cellular organization, morphological structure, and reproductive processes than that of any other algae (Bold et al. Freshwater green algae (Chlorophyta) are characterized as the largest and most varied algal phylum.
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