Seasonal Variation and Spatial Heterogeneity of Water Quality Parameters in Lake Chenghai in Southwestern China

Dissolved organic matter (DOM) is independently stratified in thermally stratified water bodies

Thermal stratification often occurs in deep-water bodies, including oceans, lakes, and reservoirs. Dissolved organic matter (DOM) plays a critical role in regulating the dynamics of aquatic food webs and water quality in aquatic ecosystems. In the past, thermal stratification boundaries have been sometimes used exclusively to analyze the vertical distribution of DOM in thermally stratified water bodies. However, the validity of this practice has been challenged. Currently, there is limited understanding of the formation mechanism and stratification of the vertical distribution of DOM in thermally stratified water bodies, which hinders the analysis of the interactions between DOM and vertical aquatic ecological factors. To address this gap, we conducted a comprehensive study to extensively collect the vertical distribution of DOM in thermally stratified water bodies and identify the primary factors influencing this distribution. We found that DOM was independently stratified in thermally stratified water bodies (including two cases in unstratified water bodies), and that the formation mechanisms and statuses of DOM stratification were different from those of thermal stratification. The boundaries and numbers of DOM stratification were generally inconsistent with those of thermal stratification. Therefore, it is more accurate to divide DOM into different layers according to its own vertical profile, and analyze DOM characteristics of each layer based on its own stratification instead of thermal stratification. This study sheds light on the relationship between DOM and thermal stratification and provides a novel approach for analyzing DOM vertical distribution characteristics and their impact on aquatic ecosystems. This finding also holds significant implications for the design and implementation of environmental management programs aimed at preserving the health and functionality of aquatic ecosystems.

Genomic analysis of the marine yeast Rhodotorula sphaerocarpa ETNP2018 reveals adaptation to the open ocean

BACKGROUND

Despite a rising interest in the diversity and ecology of fungi in marine environments, there are few published genomes of fungi isolated from the ocean. The basidiomycetous yeast (unicellular fungus) genus Rhodotorula are prevalent and abundant in the open ocean, and they have been isolated from a wide range of other environments. Many of these environments are nutrient poor, such as the Antarctica and the Atacama deserts, raising the question as to how Rhodotorula yeasts may have adapted their metabolic strategies to optimize survival under low nutrient conditions. In order to understand their adaptive strategies in the ocean, the genome of R. sphaerocarpa ETNP2018 was compared to that of fourteen representative Rhodotorula yeasts, isolated from a variety of environments.

RESULTS

Rhodotorula sphaerocarpa ETNP2018, a strain isolated from the oligotrophic part of the eastern tropical North Pacific (ETNP) oxygen minimum zone (OMZ), hosts the smallest of the fifteen genomes and yet the number of protein-coding genes it possesses is on par with the other strains. Its genome exhibits a distinct reduction in genes dedicated to Major Facilitator Superfamily transporters as well as biosynthetic enzymes. However, its core metabolic pathways are fully conserved. Our research indicates that the selective pressures of the ETNP OMZ favor a streamlined genome with reduced overall biosynthetic potential balanced by a stable set of core metabolisms and an expansion of mechanisms for nutrient acquisition.

CONCLUSIONS

In summary, this study offers insights into the adaptation of fungi to the oligotrophic ocean and provides valuable information for understanding the ecological roles of fungi in the ocean.