Undaria pinnatifida exudates trigger shifts in seawater chemistry and microbial communities from Atlantic Patagonian coasts

Abstract

The invasive kelp Undaria pinnatifida has spread from northeastern Asia to temperate coastal environments worldwide, with profound effects on colonized ecosystems. In this work, we analyzed the effect of exudates from U. pinnatifida on the chemical and microbial properties of seawater from a semienclosed gulf from Atlantic Patagonia. Exudates of U. pinnatifida, consisting mainly of carbohydrates, were released at a rate of 1.6 ± 0.8 mg C g -1 algae day -1 , affecting the quality and optical properties of seawater in experimental incubations. Parallel factor analysis based on excitation-emission matrices collected from exudates revealed the presence of two humic-like and one non-humic fluorescent components. Exudate release stimulated microbial growth and polysaccharide degrading activity in seawater. After a 7-day incubation of fresh seawater with the exudates, changes in microbial community structure were analyzed by large-scale 16S rRNA gene amplicon sequencing. Copiotrophic and fermentative genera such as Spirochaeta (Spirochaetes) and Propionigenium (Fusobacteria) increased in the incubations with algal exudates. Genomic potential prediction revealed that the selected bacterial community could have higher ribosome content -an indicator of the potential for reaching higher metabolic rates -and genes for the degradation of complex organic compounds such as polysaccharides and other carbohydrates present in the exudates. Nutrient addition triggered the emergence of other microbial populations with different ecophysiological niches: unclassified Flavobacteriales, unclassified bacteria related to the recently described Phylum Kiritimatiellaeota, as well as potential pathogens such as Vibrio (Gammaproteobacteria) and Arcobacter (Epsilonproteobacteria), suggesting potential synergistic effects between invasive macroalgae and human activities. Keywords macroalgae; bacterial communities; 16S rRNA gene amplicon sequencing; DOM concentration and quality, Southwestern Atlantic .

Microbial degradation of DOC released by the mixed culture of Crassostrea gigas and Undaria pinnatifida

“…Notably, Flavobacteria were predominant at T8, a period of rapid DOC degradation. Studies have demonstrated that Flavobacteria is a member of a rich marine microbial community that is speci cally responsible for the metabolism of algal carbohydrates and plays a key role in the biodegradation of macroalgae-derived complex organic matter through the action of extracellular enzymes (Lozada et al 2021;Mann et al 2013). Ruegeria was observed to increase in relative abundance during the slow DOC decline period to become the dominant genus in this period.…”

Mechanisms of Tolerance in Metal-exposed Brown Algae and the Importance of Monitoring Studies: A Review

“…The importance of speciation and toxicity of Cu in marine macroalgae has been reviewed by Gledhill et al (1997). Marine brown macroalgae are known to release extracellular organic matter, such as humic material, polyphenolic material, and sulfonated polysaccharides (Dogs et al, 2017;Lozada et al, 2021). Schramm (1993) found that organic substances exuded by Fucus vesiculosus and Laminaria saccharina decreased Cu toxicity, thus exhibiting the potential to alter the toxicity of Cu or its bioavailability.…”

Fucanases Related to the GH107 Family from Members of the PVC Superphylum

“…Members of this superphylum are particularly abundant in the marine environment, where they are proposed to play key ecological roles, such as in global nutrient cycling [5][6][7]. They have also been found associated with brown algae within their epiphytic biofilms [8][9][10], where algae exudates may influence the microbial community structure [10,11]. Despite the limited information on the metabolic potential of members of the PVC superphylum, recent studies have suggested that this group includes many members specialized in the degradation of sulfated polysaccharides synthesized by macroalgae [4,12,13].…”