附石生物营养质量对干旱胁迫的响应及机制OA北大核心CSTPCD

Against the backdrop of global warming,droughts are happening more often.The epilithon is crucial to primary production in river ecosystems,forms the cornerstone of material circulation in the food web,and provides carbon source for higher-level consumers.The decline in water area dur-ing droughts inevitably affects the epilithon habitat.Yet,the impact of drought on the nutritional qual-ity of epilithon remains largely unexplored.In this study,we assessed the impact of drought on nutri-tional quality by conducting a mesocosm manipulation experiment,focusing on stoichiometry and polyunsaturated fatty acids(PUFA),particularly eicosapentaenoic acid(EPA)and docosahexaenoic ac-id(DHA).The response and mechanism of nutritional quality in epilithon was then analyzed in terms of the content and composition of fatty acids,algae community structure,ecological stoichiometry,and microbial community using metagenomic sequencing.The mesocosm manipulation experiment in-cluded a drought treatment group and a control group and was run in triplicate.After preculturing for two weeks,an extreme drought was simulated in the treatment mesocosm,while water circulation was maintained in the control group.Epilithon samples were collected on day 0,7 and 14 of the ex-periment for analysis of nutritional quality.This study not only affirmed the observed influence of drought on the nutritional quality of epilithon but also delved into the underlying mechanism by ex-amining community composition and function of epilithon.The findings revealed a significant reduc-tion in DHA and EPA content in epilithon in the drought treatment group.The phosphorus(P)con-tent decreased significantly(P＜0.05),resulting in an increase in the C/P and N/P ratios.Diatoms,the predominant epilithon group,rich in EPA and DHA,exhibited a significant decline in density and abundance after the drought(P＜0.05).Additionally,metagenomic analysis revealed a significant re-duction in fatty acid biosynthesis within the lipid metabolic pathway of epilithon(P＜0.05),accompa-nied by a notable increase in fatty acid degradation(P＜0.05),contributing to the overall decline in EPA and DHA.The study indicates that drought decreases the nutritional quality of basal resource in river ecosystems,potentially influencing the growth and reproductive patterns of consumers in the food web.This study provides a novel perspective on the carbon quality of basal resources and sheds light on the intricate dynamics of food source and nutrient transfer within aquatic ecosystems.