The Distribution Of Dinoflagellate Cysts In The Nanji Islands During Spring And Summer And Its Relations To The Environmental Factors

In order to study the relationship between the distribution of the dinoflagellate cysts and its affecting factors from Nanji Islands, the writer of this article has collected the relative data during the investigation on the dinoflagellate cysts in April, June and Autumn of 2014, analyzed the groups of species, the dominant ones,the horizontal distribution and the change of water factors, then drew a conclusion as follows:(1)Six groups and twenty- seven kinds of dinoflagellate cysts are identified in the surface sediments from Nanji Islands. Among those, there are 14 autotrophic cysts and 13 heterotrophic cysts, including 10 Protoperidinioid, 9 Gonyaulacoid, 4 Caleoidinellid,2 Gymndinioid, 1 Tuberculudinioid and 1 Diplopsalid. It is detected that the autotrophic cysts, especially Caleoidinellid and Gonyaulacoid takes up much, while heterotrophic cysts(Protoperidinioid)is less. Those in the fish and shellfish Cultivation Areas from Mazu Ao and Guoxing Ao are high in heterotrophic dinoflagellate cysts proportion. The autotrophic dinoflagellate cyst is abundant in Dasha Ao Scenic Area and the total abundance of dinoflagellate cysts is relatively high. It proves that the eutrophication is serious in Mazu Ao, Guoxing Ao and Dasha Ao, which could have been influenced by the farming pollution and domestic pollution.(2)The abundance of the dinoflagellate cysts is low(2~33cysts?mL-1), and the index of Shannon-Wiener's diversity varies between 0.92 ~ 3.10. The Scrippsiella trochoidea cysts are the absolutely dominant species. The cysts abundance of the area near the shore is higher than the far area in April and Autumn, while during June, the Red tide period, it is lower than the monitoring center in the far sea. This result may be due to the facts that in the area near the shore depth of water is shallow, the water environment can be influenced easily by the outer, and the formation and germination of dinoflagellate cysts are earlier than in the far area. Having been analyzed by the IBM SPSS Statistics 22 software, there are no obvious relationship between the cyst distribution and the main environmental factors(water temperature, depth, salinity, transparency, nutrients, etc.)(P>0.05).(3)Five PSP dinoflagellate cysts(Alexandrium affine, Alexandrium andersonii, Alexandrium pesudogonyaulax, Alexandrium tamarense, Gymnodinium impudicum,) and three cysts producing YTX(Gonyaulax spinifera, Lingulodinium polyedra, Protoceratium reticulatum) have also been found in the surface sediments. Alexandrium spp. distributes widely, with its vegetative cells distributed in the water from all stations. This indicates that besides Gymnodinium mikimotoi, the Alexandrium spp. red tide also have the potential to break out in Nanji Islands.