The Carrying Effect Of Waterbirds On Aquatic Microorganisms In Chongming Dongtan Wetland

Birds exhibit multiple ecological functions amongst vertebrates.Dispersal is one of the most important behaviors in birds.Waterbirds may act as important dispersers for aquatic microorganisms.However,the number of studies of waterbirds for the dispersal of aquatic microorganisms through endozoochory and ectozoochory is limited There are mainly the following aspects:(1)Existing research has mainly focused on the simulation experiment in laboratory,which is lack of field research;(2)Most of the research has focused on Anatidae,and there are relatively few studies on shorebirds and herons;(3)Most of the research has focused on only one kind of dispersal mode of waterbirds in detail,which did not conduct a classification study on different samples of the same dispersal mode.In addition,existing research is mainly in Europe and Southern Africa,and is rarely reported in Asia and China.The main objective of this study was to demonstrate the following scientific problems:Whether the waterbirds in Chongming Dongtan Wetland can disperse of aquatic microorganisms through endozoochory and ectozoochory modes;Whether there are differences in the carrying effect of aquatic microorganisms in different samples under the endozoochory and ectozoochory modes;Whether there are seasonal variation in the dispersal of aquatic microorganisms by waterbirdsThis study took Chongming Dongtan,Shanghai as the research site,and took shorebirds and herons as the research objects.The body surface samples of 21 species of shorebirds and the internal samples of Numenius phaeopus and Ardea cinerea were collected from March 2018 to September 2019.The collected samples were separated in the laboratory,and then the isolated aquatic microorganisms were morphologically identified and counted under the optical microscope,of which the resting eggs of the invertebrates were identified by single-egg DNA barcode technology.This study explored the possibility of waterbirds dispersing aquatic microorganisms through ectozoochory and endozoochory.At the same time,this research explored whether there were differences in the carrying effect of aquatic microorganisms in different samples under the endozoochory and ectozoochory modes.In addition,this research compared the differences in the carrying effect of aquatic microorganisms through waterbirds faeces in different seasons.Moreover,this research also explored the secondary dispersal of aquatic microorganisms by Ardea cinerea of piscivorous waterbirds.This study mainly draws the following results1.The ectozoochory effect of shorebirds on aquatic microorganismsThis research collected 497 body surface samples from 21 shorebirds species.Of these body surface samples,9 species of waterbirds carried resting eggs of aquatic invertebrates,and 72 resting eggs of 23 species in 6 taxa were screened out.There were 10 species of waterbirds carrying adult aquatic invertebrates,of which,159 adult aquatic invertebrates of 41 species in 7 taxa were screened out.There were 21 bird species carrying aquatic phytoplankton,of which,32,942 aquatic phytoplankton of 45 species in 7 taxa were screened out.In this study,the body surface samples were divided into feet samples and feather samples.Of the aquatic microorganisms species recorded,a part of were shared between both two body surface samples,but the remainder were unique to each surface samples.These results showed that there were significant differences between the two body surface samples in carrying capacities for aquatic microorganisms.The two body surface samples had different roles in carrying capacities for aquatic microorganisms,also,there were a certain degree of complementarity.A total of 21 body surface samples of shorebirds were collected in this study.The number of bird species carrying phytoplankton was the highest,followed by adult invertebrates,and the resting eggs of the invertebrates was the lowest,which indicated that different species of shorebirds had different carrying capacities for aquatic microorganisms.The results of this study also showed that shorebirds had different carrying capacities for aquatic microorganisms in different groups.Overall,the highest carrying rate and quantity of the body surface samples was phytoplankton,followed by adult invertebrates and the resting eggs of the invertebrates.The above results indicated that shorebirds in Chongming Dongtan area could disperse aquatic microorganisms through ectozoochory,and the two body surface samples had different carrying capacity for aquatic microorganisms.There were also differences in the dispersal of aquatic microorganisms by different shorebirds species through ectozoochory.2.The endozoochory effect of Numenius phaeopus on aquatic microorganismsAmong the collected 152 faecal samples of Numenius phaeopus,there were 142 resting eggs of aquatic invertebrates of 11 species in 7 taxa,792 adult aquatic invertebrates of 11 species in 7 taxa,and 10181 aquatic phytoplankton of 6 species in 4 taxa.Among the collected 48 pellet samples of Numenius phaeopus,there were 15 resting eggs of aquatic invertebrates of 3 species in 3 taxa,58 adult aquatic invertebrates of 7 species in 5 taxa,and 244 aquatic phytoplankton of 5 species in 4 taxa.The above results indicated that Numenius phaeopus could disperse aquatic microorganisms and propagules through endozoochory by faeces and pellets,while the potential of the two endozoochory modes was different.Overall,the carrying rate and quantity of aquatic microorganisms in faecal samples were higher.Of the 31 aquatic microorganisms species recorded,12 were shared between both two internal samples,and 19 were unique to each samples(16 species in faeces,3 species in pellets),which showed that faecal samples and pellet samples played different roles in the dispersal of aquatic microorganisms through endozoochory.These results showed that Numenius phaeopus in Chongming Dongtan area could disperse aquatic microorganisms through endozoochory,and there were differences in the carrying capacity of the two internal samples for aquatic microorganisms.Overall,the carrying capacity of feacal samples was higher than that in pellet samples.3.The endozoochory effect of Ardea cinerea on aquatic microorganismsAmong the collected 186 faecal samples of Ardea cinerea,there were 13169 resting eggs of aquatic invertebrates of 22 species in 9 taxa,52 adult aquatic invertebrates of 14 species in 6 taxa,7149 aquatic phytoplankton of 13 species in 3 taxa These results showed that the carrying rate of different aquatic microorganisms in Ardea cinerea faeces was significantly different,among which the carrying rate of phytoplankton was the highest,followed by the resting eggs of invertebrates,and the adult invertebrates was the lowest.These results indicated that Ardea cinerea had different carrying capacities for aquatic microorganisms in different groups.There were significant differences in the carrying of aquatic microorganisms through Ardea cinerea faeces in different seasons.The number of phytoplankton and the resting eggs of invertebrates in feacal samples were significantly higher in winter than in summer,and the number of adult invertebrates in faecal samples was significantly higher in autumn than in other seasons.This may be the result of the combined effect of seasonal changes in aquatic microorganisms and the diets of Ardea cinerea.In addition,seasonal changes in fish diets may also indirectly cause seasonal changes of aquatic microorganisms in Ardea cinerea faeces.Compared with other species of waterbirds,the quantity and carrying rate of the resting eggs of invertebrates were higher in Ardea cinerea faeces,which may involve in the secondary dispersal of Ardea cinerea to aquatic microorganisms that eaten by fish,therefore,it deserves more attention.The hatching experiment of the resting eggs of invertebrates showed that the aquatic microorganisms propagules carried in Ardea cinerea faeces could be successfully hatched into adults after being digested and discharged through Ardea cinerea intestine,which showed that Ardea cinerea in Chongming Dongtan area for the dispersal of aquatic microorganisms through endozoochory mode was feasible,and provided a strong evidence for this.The results showed that Ardea cinerea could disperse aquatic microorganisms in Chongming Dongtan area,and they had diverse carrying capacities for aquatic microorganisms in different groups.At the same time,there were seasonal differences in the endozoochory of Ardea cinerea to aquatic microorganisms.This study measured the dispersal effect of waterbirds on aquatic microorganisms in Chongming Dongtan and showed that waterbirds in this area could disperse aquatic microorganisms through ectozoochory and endozoochory.This study also proved that different samples had different dispersal effects on aquatic microorganisms under the endozoochory and ectozoochory modes.In addition,there were seasonal differences in the dispersal of waterbirds to aquatic microorganisms.The Ardea cinerea for the dispersal of aquatic microorganisms showed that piscivorous waterbird may play a more prominent role in the dispersal of aquatic microorganisms through the secondary dispersal of aquatic microorganisms eaten by fish.The hatching experiment proved that the dispersal of aquatic microorganisms by waterbirds was feasible,and provided a strong evidence for this.The dispersal of aquatic microorganisms mediated by waterbirds not only plays a role in the dispersal of aquatic microorganisms and the maintenance of diversity,but also provides great assistance for bird migration and bird ecology.Therefore,future studies on related research would be an essential avenue.