Dynamics of the Eukaryotic Microbial Community at the Breeding Sites of the Large Yellow Croaker Pseudosciaena crocea in the Southern East China Sea

Clarifying eukaryotic microbial spatial distribution patterns and their determinants is an important idea in ecological research.However,information on the distribution patterns of eukaryotic microbial community structures(EMCSs)within oceans remains unclear.In this study,surface water samples from the southern East China Sea(SECS)were collected to investigate the spatiotemporal variation in EMCSs by using 18S rRNA high-throughput sequencing technology and the impact of this variation on Pseudosciaena crocea during the breeding season.The results indicated that the distribution patterns of the eukaryotic microbial community structure were different among the Sansha Bay,Mindong and Wentai reserves and the offshore East China Sea.In addition,there were notable potential effects of EMCSs on fishery activities.The variation partitioning analysis showed the environmental and spatial factors caused 53.4%of the variation in the EMCSs,indicating that spatially structured environmental factors were the key determinants of the EMCSs spatial heterogeneity in the SECS and may have contributed to the general distribution of P.crocea.In addition,all the environmental factors were the main factors driving the distribution of eukaryotic microbes except for total phosphorus.Furthermore,it was noted some phytoplankton such as Poterioochromonas and Rhizophydium of fungi in Sansha Bay can effectively prevent Cyanobacteria blooms.Chrysophyceae are natural high-quality baits for juvenile fish distributed in Sansha Bay,Mindong and Wentai reserves.This study provides a part of the insight into potential eukaryotic community distributions in large water bodies and how they are affected by environmental factors.

<i>Chroococcidiorella tianjinensis</i>gen. et sp. nov. (Trebouxiophyceae, Chlorophyta), a Green Alga Arises from the Cyanobacterium TDX16

All algae documented so far are of unknown origin. Here, we provide a taxonomic description of the first origin-known alga TDX16-DE that arises from the Chroococcidiopsis-like endosymbiotic cyanobacterium TDX16 by de novo organelle biogenesis after acquiring its green algal host Haematococcus pluvialis’s DNA. TDX16-DE is spherical or oval, with a diameter of 2.0-3.6 μm, containing typical chlorophyte pigments of chlorophyll a, chlorophyll b and lutein and reproducing by autosporulation, whose 18S rRNA gene sequence shows the highest similarity of 99.7% to that of Chlorella vulgaris. However, TDX16-DE is only about half the size of C. vulgaris and structurally similar to C. vulgaris only in having a chloroplast-localized pyrenoid, but differs from C. vulgaris in that 1) it possesses a double-membraned cytoplasmic envelope but lacks endoplasmic reticulum and Golgi apparatus;and 2) its nucleus is enclosed by two sets of envelopes (four unit membranes). Therefore, based on these characters and the cyanobacterial origin, we describe TDX16-DE as a new genus and species, Chroococcidiorella tianjinensis gen. et sp. nov., which sets the basis for multidisciplinary research.