Potential Distribution of Seagrass Meadows Based on the MaxEnt Model in Chinese Coastal Waters

Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.

Temporal and spatial variation of fish community and their nursery in a tropical seagrass meadow

Fish species composition and spatio-temporal variability of the community were studied in a tropical seagrass meadow located in a lagoon in the eastern part of North Sulawesi. The diversity of fish community in the seagrass meadows was relatively high, with the Shannon-Wiener index ranging from 1.57 to 3.69. The family Apogonidae was the most dominant in abundance(8.27 ind./(100 m2)) and biomass(28.49 g/(100 m2)). At the species level,Apogon lateralis and Sphaeramia orbicularis were the most dominant species in abundance and biomass,respectively. For spatial distribution on species, the end, middle and mouth of the lagoon clustered together as a whole, which may be due to the substrate types found in those zones. The fish species, fish abundance and fish biomass were greater in the dry and wet seasons than in the transition season, which is explained by the strong monsoon, which provides a more suitable environment and food for the fish. The maximum length of 93.10% of the captured species was less than their length at maturity, indicating that seagrass meadows are nursery habitats for many fishes. Therefore, protection of the seagrass meadows is essential for fisheries and sustainable resource utilization.

Molecular diversity and biogeography of benthic microeukaryotes in temperate seagrass(Zostera japonica)systems of northern China

The productivity and health of seagrass depend on the combined inputs of nutrients from the water and sediments in which they grow and the microbiota with which they live intimately.However,little is known about the composition and diversity pattern of single-celled benthic eukaryotes in seagrass meadows.Here,we investigated how the structure and diversity of the benthic microeukaryotic community vary with respect to season,location,and seagrass colonization,by applying 18S rRNA gene amplicon sequencing for 96 surface sediment samples that were collected from three different seagrass habitats through four seasons.We found that benthic microeukaryotic communities associated with seagrass Zostera japonica exhibited remarkable spatial and seasonal variations,as well as differences between vegetated and unvegetated sediments.Diatoms and dinoflagellates predominated in the benthic microeukaryotic communities,but they were inversely correlated and displaced each other as the dominant microbial group in different seasons or habitats.Mucoromycota was more prevalent in vegetated sediments,whereas Lobulomycetales and Chytridiales had higher proportions in unvegetated sites.Total organic carbon and total organic nitrogen were the most important environmental factors in driving the microeukaryotic assemblages and diversity.Our study expands the available knowledge on the biogeographic distribution patterns and niche preferences for benthic microeukaryotes in seagrass systems.