Biodiversity Of Benthic Dinoflagellates In The Coral Reefs Of Weizhou Island,Guangxi

Benthic dinoflagellates,including the genera of Amphidinium,Coolia,Gambierdiscus,Ostreopsis and Prorocentrum,live on benthos in marine habitats.Unlike dinoflagellates that can form red tides in open waters,they do not form surface algal blooms,but mainly adhere to the surface of macroalgae and hard dead corals.Benthic dinoflagellates play an important role in the primary productivity in the benthic ecosystems,different from the planktonic dinoflagellates,they often co-exist in the benthic ecosystem with different species.On the one hand,many benthic dinoflagellates can produce toxins and active substances,which pose a serious threat to the edible safety of aquatic products when these toxins accumulate and transfer through the food web.On the other hand,some toxins have pharmaceutical potentials.All of these highlight the necessity of the research on benthic dinoflagellates.China has a vast territory across tropical,subtropical and temperate waters combining with considerable amounts of islands.It owns a lot of suitable environment for the growth of benthic dinoflagellates.Weizhou Island in Beibu Gulf,Guangxi,which is located in the north margin of the tropical zone,has a typical coral reef ecosystem and tropical monsoon climate.Ciguatoxin contaminated fish originated from benthic dinoflagellates of Gambierdiscus has been reported in the island.This paper thus aimed to carry out the biodiversity of benthic dinoflagellates in the coral reef seawaters of Weizhou island during 2014-2016.Benthic dinoflagellates cells were harvested from macroalgae and the death of coral reefs by diving into the reef waters,and monoclonal cultures were established under the laboratory conditions.Using microscope and scanning electron microscope,cell shape,size and thecal plates characteristics were collected.In addition,the genes for D1-D3 LSU rDNA,D8-D10 LSU rDNA,ITS,SSU rDNA were sequenced,further performed to construct phylogenetic trees.By combining with the morphology and phylogeny information,the biodiversity of benthic dinoflagellates in Weizhou Island was determined.The main results are listed as follows:1)Clarified the community structure and species diversity on benthic dinoflagellates,and established an algae bank of 67 monoclonal strains of dinoflagellates from 5 genera and 6 species,including A.carterae,A.massartii,C.malayensis,G.caribaeus,Ostreopsis cf.ovata and P.maculosum.Most species are globally distributed.2)Obtained the morphological database of benthic dinoflagellates in the coral reef seawaters in Weizhou Island by using light microscope and scanning electron microscope,as well as D1-D3 LSU rDNA,D8-D10 LSU rDNA,ITS and SSU rDNA sequences information.3)Clarified distribution pattern on benthic dinoflagellates.It showed that the biodiversity of benthic dinoflagellates in the southeast and northwest of the island is higher than that of the other areas,which is thought to be largely driven by the monsoon pattern here,i.e.,summer prevails with the southwest monsoon and winter with northeast monsoon.The monsoon pattern here produces an environment of less disturbance and higher stability in the former versus in the latter;while a stability water is advantageous to the growth of benthic dinoflagellates.For the first time the biodiversity of benthic dinoflagellates in Weizhou Island,Beibu Gulf of Guangxi was studied.It successfully established a species clarified benthic dinoflagellates bank.The result not only provides scientific basis for the Beibu Gulf marine environmental protection such as benthic harmful algal blooms prevention and mitigation,but also builds up a biological resource bank related with benthic dinoflagellates,which is meaningful for future development and utilization on biological resource in the region.Last but not the least,this paper is an active response to the marine phycologists' proposals in recent years for developing the biodiversity research on benthic dinoflagellates worldwide,and is also beneficial to the current weakness knowledge in the field of benthic dinoflagellates in China.