.S.No SPECIES St I St II
I Bacillariaphycea(diatoms) Cells/1
  Family:Coscinodisceae    
1  Coscinodiscus apiculatus * a
2  Coscinodiscus centralis * *
3 C. centralis * *
4  C.concetricus * *
5 C.granii a *
6  C.gigas * *
7  C.lineatus * *
8  C.radiatus * *
9  C.thori * *
10 Cyclotella meneghiniana * a
11 C. stylorum * a
12 Cyclotella  sp * *
13 Diploneis sp. * *
14 Planktoniella sol * *
15 Planktoniella sp * *
16  Skeletonema costatum * *
17  Thalassiosira sp * *
II Family: Triceratiinae (Diatoms)    
1 Ditylum brightwelli * *
2 Ditylum sp * *
3  Triceratium reticuatum * *
4  Triceratium sp * *
5 T.favus * *
6  T.robertsianum * a
III Family: Chaetoceraceae (Diatoms)    
1  Chaetoceros affinis * *
2  C. curvicetus * a
3  C.decipiens * *
4  C. messanensis * *
5  C.diversus * *
6  C.coarctatus * a
7  C.peruvians * *
8  C.indicus * *
9  C.comosum * *
10  Bacteriostrum furcatum a *
11  Bacteriostrum hyalinum * *
IV Family: Biddulphoidae (Diatoms)    
1  Biddulphia biddulphia * *
2  B.heteroceros * a
3  B.reticulata * *
4 B.rhombus * *
5 B.sinensis * *
6 B .urita a *
7 B. pulchella * a
8  Odentella sinensis * *
9 O.mobiliensis * *
V Family:Eucambiinae (Diatoms)    
1  Eucambia groenlandica * a
2  Eucambia sp * *
VI Family: Solenoidae (Diatoms)    
1  Leptocylindrus danicus a *
2  Rhizosolenia cylindrus * *
3  R.imbricata * *
4  R. robusta * *
5  R. styliformis * a
6 Bacillaria paradoxa * *
VII Family:Isthiminae    
1 Isthima nervosa * *
VIII Family: Euodicidae (Diatoms)    
1 Hemidiscus hardmanianus * a
2 Hemdiscus sinensis * *
3 Hemdiscus sp * *
IX Order:Pennales (Diatoms)    
  Family: Naviculaceae    
1  Pleurosigma angulatum * *
2  P.elongatum * *
3  P.depressum * a
4  P.normani * *
5  Nitzshia longissima * *
6  N.seriata a *
7 Pseudo-nitzschia sp. * *
8  Navicula sp * *
9 Stephanophysis palmariana * a
X Family:Fragilariaceae (Diatoms)    
1  Thalassionema nitzschioides  * *
2 Thalassiothrix fraunfeldi a *
3 Thalassiothrix sp * *
4  Rhabdonema arcuatum * a
5  Achnantia glacialis * *
(* present of species and aAbsent of species)
Table 1: The study period recorded phytoplankton species in Muthupettai mangrove environment during May 2010- April 2011.