Geographic pattern of phytoplankton community and their drivers in lakes of middle and lower reaches of Yangtze River floodplain, China.

Disentangling the relative contributions of deterministic and stochastic processes was critical to compressive understanding of underlying mechanism governing geographic pattern and assembly of phytoplankton community, while it was seldom performed in connected lakes under human pressure. Here, we investigated phytoplankton community pattern in relation to environmental and spatial factors over 81 lakes located in the middle and lower reaches of Yangtze River (MLYR) floodplain, where many lakes suffered from eutrophication and cyanobacterial blooms. A majority of MLYR lakes had higher phytoplankton abundance surpassing 107 cells/L and were dominated by common bloom-forming cyanobacterial genera, including Pseudanabaena, Microcystis, Merismopedia, Dolichospermum, Limnothrix, and Raphidiopsis. Phytoplankton community exhibited a striking geographical pattern both for taxonomic and functional compositions, while functional groups were less sensitive, and dissimilarity in communities displayed no significant increases with increasing geographical distance. Further, species richness explained much higher percentage of community variations than species turnover, indicating a reduced effect of environmental filtering of phytoplankton species with tolerance to similar environments in connected MLYR lakes. Both deterministic and stochastic processes governed assembly and biogeographic of phytoplankton community. Variation partition analysis showed that spatial factors exhibited greater influence on phytoplankton community compared to environmental variables. The stronger influence of spatial factors was further demonstrated by Mantel test and neutral community model. These findings indicate that deterministic and stochastic processes exhibited similar biogeographic patterns for phytoplankton community in MLYR lakes, but stochastic process was overwhelmingly dominated. Moreover, a large proportion of unexplained variation implies that complex interactions exist to shape assembly mechanism of phytoplankton community in MLYR lakes.

Complete genome sequence and genomic characterization of Microcystis panniformis FACHB 1757 by third-generation sequencing.

The cyanobacterial genus Microcystis is well known as the main group that forms harmful blooms in water. A strain of Microcystis, M. panniformis FACHB1757, was isolated from Meiliang Bay of Lake Taihu in August 2011. The whole genome was sequenced using PacBio RS II sequencer with 48-fold coverage. The complete genome sequence with no gaps contained a 5,686,839 bp chromosome and a 38,683 bp plasmid, which coded for 6,519 and 49 proteins, respectively. Comparison with strains of M. aeruginosa and some other water bloom-forming cyanobacterial species revealed large-scale structure rearrangement and length variation at the genome level along with 36 genomic islands annotated genome-wide, which demonstrates high plasticity of the M. panniformis FACHB1757 genome and reveals that Microcystis has a flexible genome evolution.

Annotated Checklist of Chinese Cladocera (Crustacea: Branchiopoda). Part II. Order Anomopoda (families Macrotrichidae, Eurycercidae and Chydoridae).

About 114 "species" of Macrothrichidae, Eurycercidae, and Chydoridae (Cladocera, Anomopoda), belonging to 39 genera, have been reported from China, with 14 species in 6 genera in Macrothrichidae, 2 species in one genus in Eurycercidae, and 98 species in 31 genera in Chydoridae. In total, 203 species in 62 genera, 13 families and 4 orders have so far been reported from the country. Of these, 187 are tentatively considered as valid, while 16 are incertae sedis. In reality, many records hide taxonomic problems that remain to be settled. Up to 10 percent of this fauna might be endemic at the species level, but we expect this number to increase pending new, comprehensive studies. No endemic genera fall to be recorded. Most of the several hundreds of taxonomic or biogeeographic papers from which this information was extracted suffer from poor or outdated taxonomy, such that up to half of all species are up for re-evaluation. Detailed morphological examination, but also provoked male production, especially in chydorids, are ways to improve identifications and should be stimulated. On the other hand, the inventory is certainly still incomplete with several tropical-subtropical taxa still to be expected in China. The extreme south and islands are among promising sites that remain to be explored, as well as extreme habitats all over the country. Molecular studies in China started around the beginning or the present decade, and should be multiplied.

Annotated Checklist of Chinese Cladocera (Crustacea: Branchiopoda). Part I. Haplopoda, Ctenopoda, Onychopoda and Anomopoda (families Daphniidae, Moinidae, Bosminidae, Ilyocryptidae).

Approximately 199 cladoceran species, 5 marine and 194 freshwater and continental saltwater species, live in China. Of these, 89 species are discussed in this paper. They belong to the 4 cladoceran orders, 10 families and 23 genera. There are 2 species in Leptodoridae; 6 species in 4 genera and 3 families in order Onychopoda; 18 species in 7 genera and 2 families in order Ctenopoda; and 63 species in 11 genera and 4 families in non-Radopoda Anomopoda. Five species might be endemic of China and three of Asia. Many records are suspect at the species level, and numerous taxonomic problems remain to be settled.

Cyanobacterial fossils from 252†Ma old microbialites and their environmental significance.

The end-Permian mass extinction was followed by the formation of an enigmatic rock layer with a distinctive macroscopic spotted or dendroid fabric. This deposit has been interpreted as microbial reef rock, digitate dendrolite, digital thrombolite, dendritic thrombolite, or bacterial deposits. Agreement has been reached in considering them as microbialites, but not in their formation. This study has revealed that the spotted and dendroid microbialites were composed of numerous fossil casts formed by the planktic cyanobacterium, Microcystis, a coccoid genus that at the present-day commonly forms blooms in modern lakes, rivers, and reservoirs. The abundance of the fossils and the diagenesis they experienced has determined the macroscopic fabric: where they abundant, the rock appears as dendroid, otherwise, it appears as spotted. The ancient Microcystis bloom might produce toxin to kill other metazoans, and be responsible for the oceanic anoxia that has puzzled so many researchers for so many years.