Taxonomic And Ecological Studies On Common Epipsammic Diatoms In The Coasts Of China

As a major primary producer,diatom is an important group of the phytoplankton,which plays a very significant role in many marine or freshwater ecosystems.Compared with planktonic diatom,studies on benthic diatom is relatively poor.Benthic diatom can be divided into four different groups depending on the substrate they attached on,which are epiphytic diatom,epilithic diatom,epipelic diatom and epipsammic diatom.So far,most studies on benthic diatom have focused on epipthic diatom and epipsammic diatom has not been well studied in China.In this study,sandy grains samples were collected from the intertidal zone of 12 beaches in 11 cities(Qinhuangdao,Dalian,Qingdao,Zhoushan,Changle,Pingtan,Putian,Xiamen,Dongshan,Shenzhen and Haikou)along the coast line of China seasonally during January 2014 to December 2015.380 diatom samples were observed and photographed using light microscope(LM),scanning electron microscope(SEM)and transmission electron(TEM).Morphological taxonomy and ecological studies on the common epipsammic diatom species in the coast line of China were taken.The taxonomic studies included morphological observation,species identification,description of morphological characteristics,ecological habits and distribution of each species,along with reports on the new species and the new recorded taxa for China.The ecological studies included the species composition and geographical distribution.This study will increase our understanding of the benthic diatom in China.The main results are as follows:1.In total,81 diatom species(including 8 varieties)belonging to 2 classes,6 orders,10 families,27 genera,were identified in this study.Among those,33 species belonging to order Naviculales,2 families and 8 genera(Family Naviculaceae:7 genera 22 species;Family Cymbellaceae:1 genus 11 species).17 species belonging to order Achnanthales,2 families and 7 genera(Family Cocconeiacea:5 genera 8 species;Family Achnanthaceae:2 genera 9 species).15 species belonging to order Surirellales,1 family and 2 genera(Family Nitzschiaceae:2 genera 15 species).8 species belonging to order Coscinodiscales,2 families and 8 species(Family Coscinodiscaceae:2 genera 3 species;Family Thalassiosiraceae:1 genus 5 species).7 species belonging to order Diatomales,2 families and 6 species(Family Cymatosiraceae:1 genus 1 speices;Family Diatomaceae:5 genera 6 species).1 species belonging to order Biddulphiales,1 family and 1 species(Family Biddulphiaceae:1 genus 1 species).Detail morphological characteristics,ecological habits and distribution of each species were described together with 34 plates,298 photos.2.Two species belonging to genus Hippodonta Lange-Bert.,Witkowski&Metzeltin was observed and described.One new species Hippodonta fujiannensis Zhao,Chen&Gao,and one new record from China Hippodonta dulcis(Patrick)Potapova,were found in the intertidal zone from Longfengtou Beach,Pingtan.Hippodonta fujiannensis Zhao,Chen&Gao:cells solitary,valve elliptic-lanceolate to rhombic-lanceolate with broadly rounded ends in smaller frustules and acutely rounded ends in bigger frustules that are not protracted.Valve length 1 1-44 ?m,width 4-8 ?m.Raphe filiform,terminal endings lightly curved towards one valve side in smaller valves.Rows of areolae that go around the valve apices uniseriate.Striae dissymmetrical on the both side of the valve.On one side,one column of lineolae closest to the raphe positioned perpendicular towards remaining lineolae of striae.This column of lineolae also biseriate.One the other side,one or two lineolae close to raphe positioned perpendicular towards remaining lineolae of striae.Prominent hyaline area presents throughout valve mantle.Girdle band quite broad and unornamented.The mainly differences between Hippodonta fujiannensis Zhao,Chen&Gao and the other Hippodonta species are the dissymmetrical valve and the pattern of the striae.75 species belonging to Hippodonta Lange-Bert.,Witkowski&Metzeltin have been reported until now.But only 9 species have been recorded from marine or brackish environment,the two species in this study were both from marine environment,also the first report in China.3.Two another new record of diatom species for China were observed and described.They are Fogedia densa Park,Khim,Koh&Witkowski and Achnanthes kuwaitensis Hendey.4.Among the 81 epipsammic diatom species,the most dominant taxa were order Naviculales,Achnanthales and Surirellales with 33 species,17 species and 15 species respectively,accounting for more than 80%,while the order Diatomales and Biddulphiales were least rorcorded,with 7 species and 1 species respectively.Genera Nitzschia and Navicula were the most common genus,with 14 species and 14 species respectively,followed by genera Amphora and Achnanthes,with 11 species and 6 species respectively.The other genera normally with 5 species or less.5.The geographical distribution of the 81 epipsammic diatom species was as follow:15 species(11 genera)distributed in the cities along the coast line of the Yellow and Bohai Sea(Qinhuangdao,Dalian and Qingdao);77 species(24 genera)in the cities along the coast line of the East China Sea(Zhoushan,Changle,Pingtan,Putian,Xiamen and Dongshan);44 species(16 genera)in the cities along the coast line of the South China Sea(Shenzhen,Haikou).8 species belonging to 6 genera distributed along the whole coast line of China,which are cosmopolitan species or widely distributed in the coasts of China.