Perspectives on Marine Environmental Change in Hong Kong, 1977-2001

Marine Nanoplanktonic Diatoms from the Coastal Waters of Hong Kong

Perspectives on Marine Environment Change in Hong Kong and Southern China, 1977-2001 (ed . B. Morton). Proceedings o f a n Internationa l Worksho p Reunio n Conference. Hon g Kon g 21-26 October 2001. Hong Kong: Hong Kon g University Press, 2003. MARINE NANOPLANKTONI C DIATOM S FRO M THE COASTA L WATER S O F HONG KON G Ya-Hui Gao , Chang-Pin g Che n and Yan g L i School of Life Sciences , Xiamen University, Xiamen 361005 , China ABSTRACT Marine nanoplanktoni c diatom s hav e bee n eithe r frequentl y underestimate d o r overlooked i n phytoplankto n investigation s du e t o thei r smal l siz e (2-2 0 pm ) whic h will mostl y pas s throug h a regular phytoplankto n ne t o f 7 0 jim pore size . Seventee n water sample s (eac h 700-1000 ml ) wer e collected fro m aroun d Hon g Kon g Island i n September 199 9 fo r nanoplanktoni c diato m identificatio n usin g electro n microscop e (both TE M an d SEM) . Th e result s sho w tha t nanoplanktoni c diatom s (2 0 jum) . In total , 3 1 nanoplanktoni c diato m tax a (incuding 7 unidentified species ) belonging to 1 3 genera were collected: Arcocellulus, Chaetoceros, Cyclotella, Cymatotheca, Fragilaria, Minidiscus, Navicula, Neodelphineis, Nitzschia, Par alia,Skeletonema, Thalassionema and Thalassiosira. The dominant genera were Skeletonema, Thalassiosira an d Cyclotella. Eighteen of the identified specie s are new records for Hong Kong including two species identified a s new records for China , i. e., Thalassiosira tealata Takano and Thalassiosira allenii Takano. The distributions of these two species are described a s are SEM photographs o f their valves. INTRODUCTION Phytoplankton i s an important primary producer in marine waters and diatoms are the most important component of marine phytoplankton, especially in coastal waters (Cheng etal. 1993 ; Fay 1973 ; Gao 1990; Hallegraeff 1981 ; Jiao and Gao 1995). In most studies of marin e phytoplankton, a net with a mesh siz e of 60-7 0 p m is commonl y use d fo r sample collection. Thi s would result in the collection o f phytoplankton particle s onl y larger or a little smaller than 60-70 pm. However, nanophytoplankton (2-2 0 pm) are a 94 Y-H GAO, C-P CHEN& Y. LI significant componen t of the phytoplankton standing crop (accounting for between 50 100 %), contributin g muc h mor e tha n th e netphytoplankto n (20-20 0 \im) an d picophytoplankton ( ) Average:32. 1 range:31-3 4 Temperature (°C ) Average:25. 9 range:25-26. 5 pH Average:8.0 4 range:7.83-8.1 9 Arcocellulus cornucervis Hasle, von Stosc h an d Syvertsen* Chaetoceros sp . Coscinodiscus angustelineatus A. S.* + + + + + + (Table 1 to be continued) MARINE NANOPLANKTONI C DIATOM S 97 (Table 1 continued) Cyclotella atomus Hustedt * Cyclotella cryptica Reimann , Lein and Guillard* Cyclotella sp . Cyclotella striata (Kuetz. ) Grunow Cymatotheca minima Voigt * Fragilaria sp . Minidiscus trioculatus (F.J.R.) Hasle * Navicula climacospheniae Booth * Navicula sp . Neodelphineis pelagica Takano* Nitzschia bicapitata C I eve* Nitzschia constricta (Keutz. ) Ralfe Nitzschia fonticola Grunow * Nitzschia panduriformis var . minor Grunow * Nitzschia sp . Paralia sp. Skeletonema costatum (Grev.) Clev e Thalassionema nitzschioides Grunow Thalassiosira allenii Takano** Thalassiosira binata G. Fryxell* Thalassiosira eccentrica (Ehr.) Clev e Thalassiosira mala Takano * Thalassiosira minima Gaarder* Thalassiosira profunda (Hendey) Hasle * Thalassiosira sp . Thalassiosira subtilis (Osterfled) Gra n Thalassiosira tealata Takano** Thalassiosira tenera Proschkinae-Lavrenko * + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Note: 1 S : surface waters , D : deep waters; * new recor d for Hon g Kong , ** ne w recor d for Chin a 98 Y- H GAO , C-P CHEN & Y. LI ' wF r*£ > H Plate 1 . A , B , Arcocellulus cornucervis Hasle , vo n Stosc h an d Syvertsen ; C , Chaetoceros sp. ; D , Coscinodiscus anguste-lineatus A.S. ; E , F , Cyclotella atomus Hustedt ; G , Cyclotella cryptica Reimann , Lei n an d Guillard ; H , Cyclotella striata (Kuetz. ) Grunow . MARINE NANOPLANKTONI C DIATOM S 99 Plate 2. A , B, Cyclotella sp.; C, D, Cymatotheca minima Voigt; E, Fragilaria sp. ; F, G, Minidiscus triculatus (F.J.R. ) Hasle ; H, Navicula climacospheniae Booth . 100 Y-H GAO, C-P CHEN& Y . LI Plate 3. A , Navicula sp.; B-D, Neodelphineis pelagica Takano; E, Nitzschia bicapitata Cleve; F , Nitzschia constricta (Kuetz. ) Ralfe ; G, Nitzschia fonticola...