Endozoochory Of Aquatic Microorganisms By Watebirds In Shanghai Microwetlands

Waterbirds disperse aquatic plants and invertebrates on mainlands.Most previous studies have only investigated a certain type of organisms mediated by waterbirds.This study quantified multiple groups of aquatic organisms,such as phytoplankton,invertebrate adults,invertebrate resting eggs,mites,and nematodes.The study raised a scientific question whether watebirds in microwetlands effectively carry aquatic microorganisms?The faecal samples were collected from five microwetlands,including Kunxiu Lake Wetland Park,Shanghai Zoo,Binjiang Park,Pujiang Country Park and Nianfeng Park.Five kinds of waterfowl were investigated,including Egretta garzetta,Nycticorax nycticorax,Anser albifrons,Cygnus atratus and Pelecanus crispus.The bird droppings and sediments were collected monthly from July 2018 to October 2019 in five microwetlands.Morphological and molecular identification techniques were used to quantify aquatic microorganisms in bird droppings.The resting eggs were identified and counted to investigate whether resting eggs in faecal samples are related to setiments in sampling sites? The survival of planktons and parasite adults in fresh waterbird faecal samples within 72 hours was observed to investigate whether watebirds effectively carry planktons and parasites? The hatchlings of resting eggs in bird droppings were observed to investigate whether watebirds effectively carry resting eggs? The following results were obtained:(1)This study collected 20 species of phytoplankton from 1141 bird droppings.Percentage of phytoplankton sieved from droppings of Ardeidae was higher than Anatidae and Pelecanidae.Both abundance and richness of phytoplankton were significantly different among bird species,sampling sites and and sampling time.The abundance and richness of phytoplankton were the hightest in feces of Nycticorax nycticorax and Kunxiu Lake Wetland Park.The abundance of phytoplankton was the highest in March and the richness was the highest in October.The difference was mainly caused by cyanophyta and bacillariophyta.The phytoplankton can survive within 72 h in fresh bird droppings.The study showed that waterbirds can effectively carry phytoplankton.(2)The study collected 34 species of aquatic invertebrate adults from waterbird droppings.Percentage of invertebrate adults sieved from droppings of Ardeidae was higher than Anatidae and Pelecanidae.The abundance and richness of invertebrate adults were not significantly different among bird species,but significantly different among sampling sites and sampling time.The abundance of invertebrate adults was the hightest in Cygnus atratus,and the richness was the hightest in Nycticorax nycticorax.Both abundance and richness of invertebrate adults were the hightest in Pujiang Country Park.The abundance of invertebrate adults was the highest in October and the richness was the highest in February.Rotifers and others were the dominant groups in bird droppings.Zooplankton can survive within 72 hours in fresh bird droppings.The survival of zooplankton in Ardeidae was relatively higher,and none of zooplankton was alive in droppings of Anatidae.The study showed that Ardeidae can effectively carry zooplanktons.(3)This study collected 88 species aquatic invertebrate resting eggs from bird droppings.Percentage of resting eggs sieved from droppings of Ardeidae was higher than Anatidae and Pelecanidae.The abundance and richness of invertebrate resting eggs were affected by bird species,sampling sites and sampling time.Both abundance and richness of resting eggs were the hightest in Pelecanus crispus.The abundance of invertebrate resting eggs was the highest in Nianfeng Park,and the richness was the highest in Kunxiu Lake Wetland Park.The abundance of resting eggs was the highest in May and the richness was the highest in September.Insecta and others were the predominant groups in bird droppings.The resting eggs can hatch after passing through bird intestine.It showed that waterbirds can effectively carry resting eggs.In addition,the abundance and richness of resting eggs in bird droppings were not affected by sediments in sampling sites.(4)This study collected 1 specie of arachnid,4 species of nematode adults,11 species of arachnid eggs and six species of nematode eggs from waterbird droppings.Parasite adults and their eggs were significantly different in bird species,sampling sites and sampling times.The abundance of parasite adults and eggs of Ardeidae was lower than Anatidae and Pelecanidae.Both abundance and richness of parasite adults and eggs of Shanghai Zoo were the hightest,which was related to the high-density breeding of birds.The trend of the abundance and richness of parasite eggs in bird droppings over time was inconsistent with that of parasite adults.In addition,the arachnid and nematode adults in fresh fecal samples can survive within 72 h.It showed that waterbirds can effectively carry parasites.In conclusion,waterbirds in microwetlands can effectively carry phytoplankton,invertebrate adults,resting eggs and parasites.This study determined the important role played by Ardeidae in dispersing aquatic microorganisms.DNA barcode identification technology was firstly introduced to regulate the morphological identification results.This study also firstly explored the dispersal of waterbirds on aquatic microorganisms in China,which had accumulated basic data for domestic research.