Bioavailability of dissolved organic matter (DOM) derived from seaweed Gracilaria lemaneiformis meditated by microorganisms

• Published in: Marine pollution bulletin Vol. 209; no. Pt B; p. 117243
• Main Authors: Ou, Xiao-Li, Ou, Lin-Jian, Yang, Yu-Feng
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2024
• Subjects: Bacteria - metabolism; bacterial communities; bioavailability; Biological Availability; Carbon - metabolism; dissolved organic carbon; Dissolved organic matter; Extracellular enzyme activity; extracellular enzymes; Gracilaria; Gracilaria - metabolism; Gracilaria lemaneiformis; macroalgae; marine pollution; Microbial community; Microbiota; nitrogen; Nitrogen - metabolism; Organic Chemicals - metabolism; Phosphorus; Proteobacteria; seawater; Seawater - chemistry; Seawater - microbiology; Seaweed; Seaweed - metabolism; tryptophan; UVA; FI; RU; Extracellular enzyme activity; BG; OTUs; CBH; Em; LPS; NPP; Seaweed; Ex; Dissolved organic matter; ANOVA; BX; AMC; DOC; Microbial community; MUF; TDN; Gracilaria lemaneiformis; EEA; RDOC; TDP; DON; DOM; DOP; AG; DIN; DIP; NMDS; EEM; ANOSIM; AP; LDOC; HMW; LDOM; NAG; HIX; RDOM; LMW; PARAFAC; LAP; MCP; FDOM
• ISSN: 0025-326X; 1879-3363; 1879-3363
• DOI: 10.1016/j.marpolbul.2024.117243

Seaweed Gracilaria lemaneiformis, a significant oceanic primary producer, releases substantial dissolved organic matter (DOM) during growth and decay, potentially impacting coastal organic carbon reservoirs and microbial communities. This study aimed to investigate the bioavailability of Gracilaria-derived DOM and its interactions with microbial communities. Laboratory experiments introduced Gracilaria-derived DOM into natural seawater, tracking variations in DOM composition, microbial structure, and eight extracellular enzyme activities over 168 h. The results indicated a rapid breakdown of dissolved organic carbon, nitrogen, and phosphorus, representing 48 % to 90 % of their total concentrations within 168 h, highlighting the high DOM bioavailability. Tryptophan substances were identified as the primary components of Gracilaria-derived DOM, being highly labile and utilized by microorganisms. Within the initial 0–12 h of DOM influx, Proteobacteria significantly increased and dominated in bacterial community, while after 48 h, as DOM decomposed, Desulfobacterota became the dominant group. The labile DOM stimulated bacteria, particularly Proteobacteria, to release substantial extracellular enzymes that peaked within the first 12 h. Subsequent substrate depletion led to decreased enzyme activities. Positive correlations were observed among bacterial abundance, enzyme activities, and tryptophan substances, emphasizing the intricate interplay among microbial communities, labile DOM, and extracellular enzymes. This study underscores the high bioavailability of Gracilaria-derived DOM and its interactions with microbial communities in nearshore environments. •Gracilaria-derived DOM exhibits high biodegradability.•Tryptophan substances are the main, labile DOM components preferred by bacteria.•Gracilaria-derived DOM boosts bacterial abundance and alters community structure.•Bacteria, especially Proteobacteria, use extracellular enzymes to access DOM.•Bacterial consumption facilitates the conversion of labile DOM into refractory DOM.