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

Unveiling interactions mediated by B vitamins between diatoms and their associated bacteria from cocultures

Unveiling the interactions among phytoplankton and bacteria at the level of species requires axenic isolates to experimentally demonstrate their mutual effects. In this study, we describe the interactions among the diatoms Pseudo-nitzschia granii and Chaetoceros tenuissimus and their associated bacterial species, isolated from surface water of a coastal upwelling system using coculture experiments. Microalgae growth was assessed in axenic monocultures or in coculture with each of their co-isolated bacteria in the presence or absence of B vitamins. Pseudo-nitzschia granii growth was limited by B-vitamin supply, except when cultured with the bacteria Jannaschia cystaugens, which seemed to provide adequate levels of B vitamins to the diatom. Chaetoceros tenuissimus growth was reduced in the absence of B vitamins. Moreover, the growth of C. tenuissimus was stimulated by Alteromonas sp. and Celeribacter baekdonensis during the exponential growth. These results show a diversity of specific interactions between the diatoms and co-isolated bacteria, ranging from allelopathy to commensalism. Understanding how interactions between phytoplankton and bacteria modulate the structure and function of marine microbial plankton communities will contribute to a greater knowledge of plankton ecology and improve our ability to predict nutrient fluxes in marine ecosystems or the formation of blooms in a context of global change.Xunta de Galicia | Ref. ED481A‐2019/290Agencia Estatal de Investigación | Ref. CTM2017-83362-RAgencia Estatal de Investigación | Ref. PID2019-110011RB-C33Universidade de Vigo/CISU

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

Interaccións entre fitoplancto e bacterias nun sistema costeiro produtivo

In marine environments, the phytoplankton has coexisted with bacteria for millions of years. The interactions between phytoplankton and bacteria are ubiquitous and complex, they encompassing everything from mutualism to competition. Many of these interactions are an exchange of metabolites, which could benefit or harm the involved species. Recent studies suggest that interactions between phytoplankton and bacteria may be the key to keep the productivity in marine systems. It establishes like the main objective of the thesis: to detect relevant interactions between pairs of phytoplankton-bacteria species in coastal water in front of the Ría de Vigo, and to identify the involved metabolites. In a first phase, it will analyse a database of the RNAr-16S and RNAr-18S partial sequences from 42 shelf water samples, which were taking in front of the Ría de Vigo between 2014 and 2015. The database analysis will allow detection of pairs of phytoplankton-bacteria species that co-occur in these coastal waters. In a second phase, it will use a co-culture systems to confirm experimentally if the pairs of co-ocurring species interact with each other. The purpose of the co-cultures is to decide if the phytoplankton growth in a basic culture medium is stimulated or inhibited in the presence of pertinent bacterial specie. In the current thesis, metabolites that may be part of the interactions will also be determined by transcription analysis of the co-culture samples. The research of the seaweed-bacteria interactions has a high number of applications, both to environmental and biotechnological levels. Comprehending the interaction patterns between phytoplankton and bacteria will allow us to better understand and manage the marine resources. This gets a great amount of attention in Galicia, because of the economic repercussions of the massive proliferation of toxic phytoplankton in the aquaculture. An important section inside this investigation project is classified in our findings in a context of global change to understand the response of microplankto to problems, such as the increase of CO2 in the atmosphere or the boost of ocean intakes of anthropogenic nutrients.En ambientes marinos el fitoplancton coexiste con las bacterias desde hace millones de años. Las interacciones entre fitoplancton y bacterias son ubicuas y complejas, abarcando desde el mutualismo hasta la competencia. Muchas de estas interacciones implican el intercambio de metabolitos que pueden beneficiar o perjudicar a las especies implicadas. Estudios recientes sugieren que las interacciones entre fitoplancton y bacterias pueden ser claves en el mantenimiento de la productividad de los sistemas marinos. Se establece como objetivo general detectar interacciones relevantes entre pares de especies fitoplancton-bacterias en aguas costeras frente a la Ría de Vigo, e identificar los metabolitos implicados. En una primera fase, se analizará una base de datos de secuencias parciales de los genes ARNr-16S y ARNr-18S de un total de 42 muestras de agua tomadas frente a la Ría de Vigo entre los años 2014 y 2015. El análisis de estos datos permitirá detectar pares de especies de fitoplancton y de bacterias que co-ocurren en estas aguas costeras. En una segunda fase, se utilizarán sistemas de co-cultivo con el fin de corroborar experimentalmente si los pares de especies co-ocurrentes interaccionan entre sí. La finalidad de los co-cultivos es determinar si el crecimiento de la especie de fitoplancton en un medio de cultivo básico se ve estimulado o inhibido en presencia de la correspondiente especie bacteriana. En la presente tesis se buscarán también cuál/cuáles pueden ser los metabolitos involucrados en las interacciones mediante el análisis transcriptómico de muestras de los co-cultivos. El estudio de las interacciones alga-bacteria, tiene gran número de aplicaciones, tanto a nivel ambiental como biotecnológico. Entender los patrones de interacción entre el fitoplancton y las bacterias, nos permitirá comprender y gestionar mejor los recursos marinos. En Galicia esto es de gran interés, debido a las repercusiones económicas de las proliferaciones masivas de fitoplancton tóxico sobre la acuicultura. Un apartado muy importante dentro de esta investigación, es enmarcar los resultados obtenidos en el contexto de cambio global para entender las respuestas del microplancton a problemas como el aumento de CO2 en la atmósfera y el incremento de las entradas al océano de nutrientes de origen antropogénico.Nos ambientes mariños o fitoplancto coexiste coas bacterias dende fai millóns de anos. As interaccións entre fitoplancto e bacterias son ubicuas e complexas, abarcando dende o mutualismo ata a competencia. Moitas destas interaccións implican o intercambio de metabolitos que poden beneficiar o prexudicar as especies implicadas. Estudos recentes suxiren que as interaccións entre fitoplancto e bacterias poden ser claves no mantemento da produtividade dos sistemas mariños. Establécese como obxetivo xeral detectar interaccións relevantes entre pares de especies fitoplancto-bacterias en augas costeiras fronte á Ría de Vigo e identificar os metabolitos implicados. Nunha primeira fase, analizaranse unha base de datos de secuencias parciais dos xenes ARNs-16S e ARNr-18S dun total de 42 mostras de auga tomadas fronte á Ría de Vigo entre os anos 2014 e 2015. A análise destes datos permitirá detectar pares de especies de fitoplancto e bacterias que co-ocorren nestas augas costeiras. Nunha segunda fase, utilizaranse sistemas de co-cultivo co fin de corroborar experimentalmente se os pares de especies co-ocorrentes interaccionan entre si. A finalidade dos co-cultivos é determinar se o crecemento da especie de fitoplancto nun medio de cultivo básico vese estimulado ou inhibido en presenza da correspondente especie bacteriana. Na presente tese buscaranse tamén cal/cales poden ser os metabolitos involucrados nas interaccións mediante a análise transcriptómica das mostras dos co-cultivos. O estudo das interaccións alga-bacteria, teñen gran número de aplicacións, tanto a nivel ambiental coma biotecnolóxico. Entender os patróns de interacción entre o fitoplancto e as bacterias, permitiranos comprender e xestionar mellor os recursos mariños. En Galicia isto é de gran interese, debido ás repercusións económicas das proliferacións masivas de fitoplancto tóxico sobre a acuicultura. Un apartado moi importante dentro desta investigación, é enmarcar os resultados obtidos nun contexto de cambio global para entender as respostas do microplancto a problemas como o aumento do CO2 na atmósfera e o incremento das entradas ao océano dos nutrientes de orixe antropoxénico.Agencia Estatal de Investigación | Ref. CTM2017-83362-RAgencia Estatal de Investigación | Ref. PID2019-110011RB-C33Xunta de Galicia | Ref. EM2013/023Xunta de Galicia | Ref. ED481A-2019/29

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