Role of bacterial community composition as a driver of the small-sized phytoplankton community structure in a productive coastal system

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGWe present here the first detailed description of the seasonal patterns in bacterial community composition (BCC) in shelf waters off the Ría de Vigo (Spain), based on monthly samplings during 2 years. Moreover, we studied the relationship between bacterial and small-sized eukaryotic community composition to identify potential biotic interactions among components of these two communities. Bacterial operational taxonomic unit (OTU) richness and diversity systematically peaked in autumn–winter, likely related to low resource availability during this period. BCC showed seasonal and vertical patterns, with Rhodobacteraceae and Flavobacteriaceae families dominating in surface waters, and SAR11 clade dominating at the base of the photic zone (30 m depth). BCC variability was significantly explained by environmental variables (e.g., temperature of water, solar radiation, or dissolved organic matter). Interestingly, a strong and significant correlation was found between BCC and small-sized eukaryotic community composition (ECC), which suggests that biotic interactions may play a major role as structuring factors of the microbial plankton in this productive area. In addition, co-occurrence network analyses revealed strong and significant, mostly positive, associations between bacteria and small-sized phytoplankton. Positive associations likely result from mutualistic relationships (e.g., between Dinophyceae and Rhodobacteraceae), while some negative correlations suggest antagonistic interactions (e.g., between Pseudo-nitzchia sp. and SAR11). These results support the key role of biotic interactions as structuring factors of the small-sized eukaryotic community, mostly driven by positive associations between small-sized phytoplankton and bacteria.Xunta de Galicia | Ref. EM2013/023Xunta de Galicia | Ref. ED481A-2019/290Xunta de Galicia | Ref. ED431I 2020/03Ministerio de Economía y Competitividad | Ref. CTM2017-83362-RMinisterio de Ciencia e Innovación | Ref. PID2019-110011RB-C3

Co-occurrence and diversity patterns of benthonic and planktonic communities in a shallow marine ecosystem

Marine microorganisms are involved in a variety of biogeochemical cycles and live in diverse ecological communities where they interact with each other and with other organisms to guarantee ecosystem functions. The present study focused on a shallow marine environment located in Ría de Vigo (NW, Spain), where sediment and size-fractionated plankton samples were collected from 2016 to 2018. DNA metabarcoding was used to describe the eukaryote and prokaryote composition and diversity in sediments and plankton and to depict possible associations among the most frequent and abundant organisms by co-occurrence network analysis. High eukaryote and prokaryote diversity indices were obtained in all compartments. Significant differences among eukaryote and prokaryote communities were found between sediment and plankton samples, with a high percentage of exclusive operational taxonomic units (OTUs) associated with each compartment, especially from sediment. Despite these differences, shared taxa between water and sediment were also obtained, suggesting a relatively meaningful exchange of organisms between both environmental compartments. Significant co-occurrences were mainly obtained between prokaryotes (41%), followed by eukaryotes–prokaryotes (32%) and between eukaryotes (27%). The abundant and strong positive correlations between organisms, including representatives from the sediment and the water column, suggested an essential role of biotic interactions as community-structuring factors in shallow waters where beneficial associations likely prevail. This study provides a novel approach for the detailed description of the eukaryote and prokaryote diversity and co-occurrence patterns in a shallow marine area, including both the sediment and different water-size fractions. The high diversity obtained and the detection of predominantly coexisting interactions among organisms from sediment and the overlying water column suggest a movement of species between both habitats and therefore confirm the importance of integratively studying shallow marine ecosystems.Xunta de Galicia | Ref. IN606A-2018/020Xunta de Galicia | Ref. IN607B 2019/01Agencia Estatal de Investigación | Ref. CTM2017-83362-RInterreg España-Portugal | Ref. 20200474_BLUEBIOLA

Linking the impact of bacteria on phytoplankton growth with microbial community composition and co-occurrence patterns

The interactions between microalgae and bacteria have recently emerged as key control factors which might contribute to a better understanding on how phytoplankton communities assemble and respond to environmental disturbances. We analyzed partial 16S rRNA and 18S rRNA genes from a total of 42 antibiotic bioassays, where phytoplankton growth was assessed in the presence or absence of an active bacterial community. A significant negative impact of bacteria was observed in 18 bioassays, a significant positive impact was detected in 5 of the cases, and a non-detectable effect occurred in 19 bioassays. Thalasiossira spp., Chlorophytes, Vibrionaceae and Alteromonadales were relatively more abundant in the samples where a positive effect of bacteria was observed compared to those where a negative impact was observed. Phytoplankton diversity was lower when bacteria negatively affect their growth than when the effect was beneficial. The phytoplankton-bacteria co-occurrence subnetwork included many significant Chlorophyta-Alteromonadales and Bacillariophyceae-Alteromonadales positive associations. Phytoplankton-bacteria co-exclusions were not detected in the network, which contrasts with the negative effect of bacteria on phytoplankton growth frequently detected in the bioassays, suggesting strong competitive interactions. Overall, this study adds strong evidence supporting the key role of phytoplanktonbacteria interactions in the microbial communities.Agencia Estatal de Investigación | Ref. CTM2017-83362-RAgencia Estatal de Investigación | Ref. PID2019-110011RB-C33Xunta de Galicia | Ref. ED481A-2019/290Xunta de Galicia | Ref. ED481A-2018/288Universidade de Vigo/CISU

Role of Bacterial Community Composition as a Driver of the Small-Sized Phytoplankton Community Structure in a Productive Coastal System

18 pages, 7 figures, supplementary information https://doi.org/10.1007/s00248-022-02125-2.-- Data Availability: Not applicableWe present here the first detailed description of the seasonal patterns in bacterial community composition (BCC) in shelf waters off the Ría de Vigo (Spain), based on monthly samplings during 2 years. Moreover, we studied the relationship between bacterial and small-sized eukaryotic community composition to identify potential biotic interactions among components of these two communities. Bacterial operational taxonomic unit (OTU) richness and diversity systematically peaked in autumn–winter, likely related to low resource availability during this period. BCC showed seasonal and vertical patterns, with Rhodobacteraceae and Flavobacteriaceae families dominating in surface waters, and SAR11 clade dominating at the base of the photic zone (30 m depth). BCC variability was significantly explained by environmental variables (e.g., temperature of water, solar radiation, or dissolved organic matter). Interestingly, a strong and significant correlation was found between BCC and small-sized eukaryotic community composition (ECC), which suggests that biotic interactions may play a major role as structuring factors of the microbial plankton in this productive area. In addition, co-occurrence network analyses revealed strong and significant, mostly positive, associations between bacteria and small-sized phytoplankton. Positive associations likely result from mutualistic relationships (e.g., between Dinophyceae and Rhodobacteraceae), while some negative correlations suggest antagonistic interactions (e.g., between Pseudo-nitzchia sp. and SAR11). These results support the key role of biotic interactions as structuring factors of the small-sized eukaryotic community, mostly driven by positive associations between small-sized phytoplankton and bacteriaOpen Access funding provided thanks to the Universidade de Vigo/CISUG agreement with Springer Nature. This work was supported by project DIMENSION (grant EM2013/023) from Xunta de Galicia, project INTERES (CTM2017-83362-R) from Spanish Ministry of Economy and Competitivity and project TRAITS (PID2019-110011RB-C33) from Spanish Ministry of Science and Innovation. C. C-S was funded by a predoctoral fellowship (ED481A-2019/290) from Xunta de Galicia, co-funded by FSE Galicia (2014–2020). S. M-G was funded by a Distinguised Researcher contract from Xunta de Galicia (ED431I 2020/03). Open Access funding provided thanks to the CRUE-CSIC agreement with Springer NatureWith the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

Co-occurrence and diversity patterns of benthonic and planktonic communities in a shallow marine ecosystem

Poster.-- Close Encounters IIM (3rd Kind), Vigo, 23 June 2022Shallow marine zones include some of the most dynamic marine habitats, where organisms respond quickly to human influences in the terrestrial ecosystem and interact within and between contrasting environments (e g sediment, water) by contributing to community structure, activity and resistance to environmental changes The study of the taxonomic diversity of small eukaryotic and prokaryotic organisms in marine ecosystems has been growing since the application of high throughput sequencing tools, circumventing the difficulties of isolating and culturing, and thus, improving our knowledge on their ecological role in the environment However, few studies have simultaneously analysed the diversity of microbial communities in shallow waters and sediments. DNA metabarcoding was used to explore the diversity and taxonomic composition of eukaryotes and prokaryotes in sediments and plankton in a shallow area within Ría de Vigo to depict possible associations among the most frequent and abundant organisms by co-occurrence network analysisN

Co-occurrence and diversity patterns of benthonic and planktonic communities in a shallow marine ecosystem

18 pages, 8 figures, 1 table.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)Marine microorganisms are involved in a variety of biogeochemical cycles and live in diverse ecological communities where they interact with each other and with other organisms to guarantee ecosystem functions. The present study focused on a shallow marine environment located in Ría de Vigo (NW, Spain), where sediment and size-fractionated plankton samples were collected from 2016 to 2018. DNA metabarcoding was used to describe the eukaryote and prokaryote composition and diversity in sediments and plankton and to depict possible associations among the most frequent and abundant organisms by co-occurrence network analysis. High eukaryote and prokaryote diversity indices were obtained in all compartments. Significant differences among eukaryote and prokaryote communities were found between sediment and plankton samples, with a high percentage of exclusive operational taxonomic units (OTUs) associated with each compartment, especially from sediment. Despite these differences, shared taxa between water and sediment were also obtained, suggesting a relatively meaningful exchange of organisms between both environmental compartments. Significant co-occurrences were mainly obtained between prokaryotes (41%), followed by eukaryotes–prokaryotes (32%) and between eukaryotes (27%). The abundant and strong positive correlations between organisms, including representatives from the sediment and the water column, suggested an essential role of biotic interactions as community-structuring factors in shallow waters where beneficial associations likely prevail. This study provides a novel approach for the detailed description of the eukaryote and prokaryote diversity and co-occurrence patterns in a shallow marine area, including both the sediment and different water-size fractions. The high diversity obtained and the detection of predominantly coexisting interactions among organisms from sediment and the overlying water column suggest a movement of species between both habitats and therefore confirm the importance of integratively studying shallow marine ecosystemsThis work was supported by the Ministerio de Economía y Competitividad, Spain (CTM2017-83362-R), Consellería de Economía, Emprego e Industria–GAIN, Xunta de Galicia (IN607B 2019/01), Fondo Europeo de Desarrollo Regional FEDER en el marco del programa Interreg V A España – Portugal (POCTEP) 2014-(20200474_BLUEBIOLAB), VIVALDI [678589] (EU H2020), and Controlling Microbiomes Circulations for Better Food Systems” (CIRCLES) [818290] (EU H2020). RR-C wishes to thank the Axencia Galega de Innovación (GAIN, Xunta de Galicia) for her predoctoral contract (IN606A-2018/020)Peer reviewe

Inputs of nutrients and dissolved organic matter control phytoplankton- bacteria interactions in a productive coastal ecosystem

2nd Meeting of the Iberian Ecological Society (SIBECOL), XXI conference of the Iberian Association of Limnology (AIL) and 21st National Congress of the Portuguese Ecological Society (SPECO), 3-8 July 2022, AveiroAnthropogenic alterations of global biogeochemical cycles are changing not only the magnitude but also the nature of matter entering into the ocean, thus increasing the C/P and N/P ratios. Allochthonous inputs are particularly significant in coastal systems and even may equal autochthonous sources. The interactions between phytoplankton and bacteria likely play a major role in the response of primary producers to anthropogenic matter inputs. However, the magnitude and nature of such interactions, as well as the factors controlling their intensity and sign are largely unknown in marine planktonic ecosystems. A set of 18 microcosms (2 L) experiments were conducted to test the hypothesis that the nature of the nutrient inputs modulates the strength and sign of the interaction between phytoplankton and bacteria. The experiments consisted in the addition of nutrients (nitrate, ammonium an phosphate), nutrients and dissolved organic matter (DOM) (glucose and amino acids), or riverine water (10% final concentration) containing different DOM:P proportions to intact microbial communities and microbial communities where bacteria were selectively blocked with a previously tested combination of antibiotics. Sampling was conducted in different seasons in the Ría de Vigo, a highly productive coastal ecosystem located NW Spain. An interaction index was calculated as the quotient between the change in chlorophyll-a concentration after nutrient amendment in the intact communities and the corresponding change in the same community but treated with antibiotics. An interaction index >1 thus indicates a positive effect of bacteria on phytoplankton, while an interaction index <1 indicates an overall negative impact. The interaction index ranged from 0.51 to 1.24. The index was significantly higher in autumn (1.01±0.03) than in spring (0.91±0.02), and winter (0.90±0.03). Overall, treatments with a high DOM:P ratio promoted a strong negative impact of bacteria on phytoplankton (0.84±0.06), indicating a predominance of competitive or antagonist interactions. A significant correlation was found between the interaction index and the concentration of nitrite (r=0.44, p<0.001, n=70), which suggests that phytoplankton-bacteria interactions may be linked to nitrification in this coastal productive ecosystemN