Microbiomes have fundamental roles in the functioning of aquatic ecosystems and changes in their configuration could lead to changes in food webs, ecosystem services, and overall ecosystem function, which is of particular concern for the planet (and human) health. Microbiomes vary spatially and temporally, and patterns of variation can be observed on a wide range of scales: spatially, from micro- to planetary scales, and temporally, from seconds to millennia. During the last decades, we started to understand the patterns of variation of microbiomes at different spatiotemporal scales and the ecological processes that drive them: selection, dispersal, drift, and speciation. Yet, knowledge is still limited regarding the main patterns emerging from these processes as well as their operation at different spatiotemporal scales. Much less is known regarding the effects of global change on these processes. Selection can shape microbiomes through abiotic or biotic drivers, and multiple studies have shown how physicochemical variables affect the structure and biogeography of microbiomes. In turn, little is known about how biotic variables influence the configuration of microbiomes, highlighting the large knowledge gap on microbial interactions. Furthermore, while we have a general understanding of how selection over long time scales can lead to diversification, less is known about the action of selection over short time scales potentially leading to the contemporary evolution of microbial populations (months-years). Several studies have contributed to a better understanding of microbial dispersal. Still, many questions remain about this process at planetary scales and across biomes, as well as over large time frames (millennia). Grasping the dispersal capacity of different microbial groups and how global change could affect the overall dispersal of microbes is also among our current challenges. Among the less known mechanisms affecting the structure of microbiomes are drift and speciation. However, recent studies focusing on population genomics are bringing new insights into the fine-grained genomic changes that may lead to population divergence and eventually, speciation. Global change affects aquatic microbiomes (by altering community composition) and microbiomes affect global change (through changes in microbiome function). Ecosystems are changing rapidly due to global change, and predicting future changes in microbiomes will only be possible if we better understand the processes shaping them. This session aims at attracting works focusing on the spatiotemporal patterns of microbiomes, the processes that shape them, as well as their interactions with global change.
Lead Organizer: Ramiro Logares, ICM-CSIC (ramiro.logares@icm.csic.es)
Co-organizers:
Mireia Mestre, MNCN-CSIC (mireia.mestre.martin@gmail.com)
Georgina Brennan, ICM-CSIC (georgina@icm.csic.es)
Carlos Pedrós-Alió, CNB-CSIC (cpedros@cnb.csic.es)
Presentations
05:00 PM
Dark dissolved inorganic carbon fixation by prokaryotes in the Atlantic and Pacific Ocean (5101)
Primary Presenter: Chie Amano, University of Vienna (chie.amano@univie.ac.at)
Dark dissolved inorganic carbon (DIC) fixation in the ocean is mediated by chemoautotrophs and mixotrophs, as well as heterotrophs via anaplerotic metabolism. Organic carbon production by dark DIC fixation processes has long been thought to be negligible compared to phytoplankton primary production. Yet, recent studies indicate that dark DIC fixation in the mesopelagic waters is in the same order of magnitude as heterotrophic prokaryotic production. We investigated the spatial distribution of bulk dark DIC fixation in the Atlantic and Pacific Ocean and the cell-specific bicarbonate uptake rates determined by microautoradiography. Higher bulk DIC fixation and relative abundance of prokaryotes taking up DIC were found in epipelagic waters (~30% of total prokaryotes) than in mesopelagic waters. Meso- and bathypelagic prokaryotes exhibited nearly equal cell-specific DIC uptake rates than the epipelagic communities even though only ~1-5% of prokaryotes took up DIC. These results indicate an active fraction of DIC fixing prokaryotes down to bathypelagic layers.
05:15 PM
Abundance and diversity of aerobic anoxygenic phototrophic communities along the horizontal and vertical gradients in the Atlantic Ocean (5122)
Primary Presenter: Carlota Gazulla, Universitat Autònoma de Barcelona (lotaruiz@gmail.com)
Photoheterotrophic organisms play a significant role in the carbon flow of marine environments. Among them, aerobic anoxygenic phototrophic (AAP) bacteria stand out due to their ability to harvest light using bacteriochlorophyll a. In spite of their relatively low abundances, they are a dynamic group that exhibits faster growth rates than other bacterioplankton groups. Many studies have focused on their temporal patterns and spatial distribution in the surface ocean; however, little is known about their distribution along the water column. We hypothesized that AAP bacteria will follow a strong vertical gradient related to the deep chlorophyll maximum (DCM) structure and, to test it, we analyzed a total of 171 samples along the DCM profile in contrasting trophic zones of the Atlantic Ocean. We combined epifluorescence microscopy for abundance, high-pressure liquid chromatography for pigment analysis, and high-throughput sequencing of the pufM gene, to describe the diversity and abundance distribution of AAP communities. These bacteria follow a marked horizontal and vertical gradient, as seen by differences in the diversity and taxonomic composition of their communities, dominated by different uncultured assemblages that have been barely described previously. Bacteriochlorophyll a and AAP abundances follow the vertical chlorophyll variation, with contrasting changes along the different trophic regimes. The structure of AAP communities is highly dependent on the phytoplankton communities pointing to a strong coupling between both groups.
05:30 PM
MALASPINA MICROBIAL VERTICAL PROFILES METAGENOMES: A DATASET TO DISENTANGLE FUNCTIONAL TRAITS AMONG BACTERIAL AND ARCHAEAL GENOMES THROUGHOUT OCEAN LAYERS. (5310)
Primary Presenter: Pablo Sánchez, Institut de Ciències del Mar, CMIMA-CSIC (pablosanchez@icm.csic.es)
There is a gap in knowledge on broad-scale diversity and functional patterns along the continuum between the photic and the dark ocean microbes, including trends in genome size (GS) and functional diversity. To address this gap, we present the Malaspina Microbial Vertical Profiles Metagenomes dataset, comprising 76 microbial metagenomes (0.2-3um) collected in 11 stations in the tropical and subtropical open oceans from 3 to 4,000 m deep, a 46.3 million gene catalog and 1,228 Metagenome-Assembled Genomes (MAGs). Our results show increased functional richness in the bathypelagic and a strong positive association between GS and depth for the most abundant phyla in samples up to 1,000 m, while this association is absent in the bathypelagic. Conversely, lower abundance taxa displayed a bimodal distribution of GS, with a smaller peak in the mesopelagic and a larger peak in the bathypelagic. Opposing trends were observed for protein-encoding gene density and functional diversity across epipelagic and deep ocean MAGs. Specifically, protein-encoding gene density was higher at the epipelagic and decreased towards the bathypelagic for most of the taxa, pointing out that genome streamlining generally holds true, but it is not universal for all microbes. Larger prokaryotic GS in the bathypelagic was associated with a higher prevalence of prophages and defense systems. We suggest that a combination of factors, including genome streamlining, metabolic diversification, viral infection, and molecular defense systems, drive the genomic diversity of marine prokaryotes across ocean layers.
05:45 PM
Rafting relaxes the microbiome: oceanic dispersal relaxes selective pressures in the microbiome (4816)
Primary Presenter: William Pearman, University of Otago (wpearman1996@gmail.com)
Temporal changes in host-associated microbiomes during host-dispersal processes are almost entirely unexplored, especially for hosts which undergo rare or stochastic dispersal. What little we do know has been gleaned from simulations or examination of microbiomes of hosts undertaking regular migratory movements, which might differ from less regular dispersal events. Here we directly examine the microbiomes of oceanic rafting seaweed, leveraging host genomic analyses, amplicon sequencing, and oceanographic modelling to study the impacts of stochastic ecological dispersal of hosts on the microbiome. We find that during their voyage, rafts tend to shift from a community dominated by core microbes to a community dominated by a few abundant taxa, and many rare taxa. Raft microbiomes rapidly diverge from those of non-rafts, with changes in selective pressures leading to major community changes and increased dysbiosis over the course of oceanic rafting. These data have particular significance under scenarios of increasing environmental variability such as those arising from climate change, where host range shifts are likely to lead to increased movement of hosts along broader ecological ranges.
06:00 PM
COMMUNITY COALESCENCE OF HIPPO GUT AND AQUATIC MICROBIAL COMMUNITIES IN A TROPICAL RIVER ALTERS ECOSYSTEM PROCESSES (5003)
Primary Presenter: Christopher Dutton, University of Florida (cldutton@gmail.com)
The composition of animal gut microbiomes typically differs from that of external environmental microbiota, in part due to biogeochemical differences between the gut and the environment. However, through defecation, animals transfer a portion of their gut microbiome to the environment together with organic matter, nutrients, and metabolic byproducts. These inputs can directly shape the external environment in a way that may support the persistence of gut microbiota outside the host gut. This coupled gut-environment meta-ecosystem – which we term the meta-gut – may allow ex situ gut microbes to persist in the environment and, at sufficiently high densities, influence ecosystem processes. We surveyed hippopotamus pools spanning a gradient of hippo loading in the Mara River, Kenya, for their biogeochemistry, ecosystem function and microbial community composition. We found that hippos alter the biogeochemistry of pools variably depending on hippo number and water residence time, with large inputs of hippo feces under low flow conditions causing pools to switch from an oxic to an anoxic state. These anoxic conditions facilitate the external persistence of hippo gut microbes. 16S rRNA sequencing of the total RNA has shown that the microbial community in the river begins to functionally resemble that of the hippo gut. The presence and activity of hippo gut microbes in the bottom waters of hippo pools could accelerate the decomposition of organic matter, despite the anoxic conditions, and potentially contribute to the higher rates of ecosystem respiration and concentrations of carbon dioxide and methane we have measured in the pools. Understanding the potential influence of animal microbiomes on the environment may be particularly important in systems in which native biodiversity is declining, being replaced by livestock, or being restored.
06:15 PM
TEMPORAL DYNAMICS OF VIBRIO POPULATIONS IN THE BALTIC SEA REGION (5289)
Primary Presenter: Victor Fernandez Juarez, University of Copenhagen (victor.fj@bio.ku.dk)
Elevated sea surface temperatures are increasing the prevalence of pathogenic bacteria at higher latitudes. The recent increase in Vibrio-related wound infections and deaths, the latter often related to Vibrio vulnificus, along the Baltic coasts is therefore of serious concern. Recently, the eelgrass Zostera marina has been suggested to reduce Vibrio spp. abundance on surrounding waters, potentially mitigating the problem at the local scale. In this context, our question was which environmental and biological factors regulate Vibrio dynamics in and outside of eelgrass meadows in the Baltic Sea. For three coastal sites of different salinities (from 6 to 21 PSU) in Denmark, Germany, and Finland we sampled within eelgrass meadows as well as 15 m and 100 m outside, monitoring the absolute and relative abundances of the genus Vibrio and V. vulnificus in the water column and sediment. In contrast to our expectations, we found that Vibrio spp. was usually accumulated in eelgrass meadows. Vibrio vulnificus correlated at salinities of 8–11.4 PSU with warm temperatures, bacterial abundance, and turbidity in July and August, peaking at 104–105 gene copies L-1. Sediment appeared to accumulate V. vulnificus and could be a potential source of this pathogen in the water column. At the conference, a temporal model integrating all measured parameters, explaining the temporal dynamics of opportunistic Vibrio pathogens in coastal Baltic Sea waters, will be presented.
SS026C Aquatic Microbiomes Over Space and Time in a Changing Planet
Description
Time: 5:00 PM
Date: 7/6/2023
Room: Auditorium Mallorca