Community Dynamics of Free-living and Particle-associated Bacterial Assemblages during a Freshwater Phytoplankton Bloom

ABSTRACT Processing of the phytoplankton-derived organic sulfur compound dimethylsulfoniopropionate (DMSP) by bacteria was studied in seawater microcosms in the coastal Gulf of Mexico (Alabama). Modest phytoplankton blooms (peak chlorophyll a [Chl a] concentrations of ∼2.5 μg liter−1) were induced in nutrient-enriched microcosms, while phytoplankton biomass remained low in unamended controls (Chl a concentrations of ∼0.34 μg liter−1). Particulate DMSP concentrations reached 96 nM in the enriched microcosms but remained approximately 14 nM in the controls. Bacterial biomass production increased in parallel with the increase in particulate DMSP, and nutrient limitation bioassays in the initial water showed that enrichment with DMSP or glucose caused a similar stimulation of bacterial growth. Concomitantly, increased bacterial consumption rate constants of dissolved DMSP (up to 20 day−1) and dimethylsulfide (DMS) (up to 6.5 day−1) were observed. Nevertheless, higher DMSP S assimilation efficiencies and higher contribution of DMSP to bacterial S demand were found in the controls compared to the enriched microcosms. This indicated that marine bacterioplankton may rely more on DMSP as a source of S under oligotrophic conditions than under the senescence phase of phytoplankton blooms. Phylogenetic analysis of the bacterial assemblages in all microcosms showed that the DMSP-rich algal bloom favored the occurrence of various Roseobacter members, flavobacteria (Bacteroidetes phylum), and oligotrophic marine Gammaproteobacteria. Our observations suggest that the composition of the bacterial assemblage and the relative contribution of DMSP to the overall dissolved organic sulfur/organic matter pool control how efficiently bacteria assimilate DMSP S and thereby potentially divert it from DMS production.

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Heligmosomoides polygyrusreduces infestation ofIxodes ricinusin free-living yellow-necked mice,Apodemus flavicollis

Parasitology ◽

10.1017/s0031182008005404 ◽

2009 ◽

Vol 136 (3) ◽

pp. 305-316 ◽

Cited By ~ 29

Author(s):

N. FERRARI ◽

I. M. CATTADORI ◽

A. RIZZOLI ◽

P. J. HUDSON

Keyword(s):

Community Dynamics ◽

Tick Infestation ◽

Natural Populations ◽

Negative Relationship ◽

Gastrointestinal Nematode ◽

Negative Association ◽

Host Susceptibility ◽

Apodemus Flavicollis ◽

Free Living ◽

Cross Sectional

SUMMARYFree-living animals are usually inhabited by a community of parasitic species that can interact with each other and alter both host susceptibility and parasite transmission. In this study we tested the prediction that an increase in the gastrointestinal nematodeHeligmosomoides polygyruswould increase the infestation of the tickIxodes ricinus, in free-living yellow-necked mice,Apodemus flavicollis. An extensive cross-sectional trapping survey identified a negative relationship betweenH. polygyrusandI. ricinuscounter to the prediction. An experimental reduction of the nematode infection through anthelmintic treatment resulted in an increase in tick infestation, suggesting that this negative association was one of cause and effect. Host characteristics (breeding condition and age) and habitat variables also contributed to affect tick infestation. While these results were counter to the prediction, they still support the hypothesis that interactions between parasite species can shape parasite community dynamics in natural systems. Laboratory models may act differently from natural populations and the mechanism generating the negative association is discussed.

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Functional similarity of attached and free-living bacteria during freshwater phytoplankton blooms

Aquatic Microbial Ecology ◽

10.3354/ame025103 ◽

2001 ◽

Vol 25 ◽

pp. 103-111 ◽

Cited By ~ 26

Author(s):

J Worm ◽

K Gustavson ◽

K Garde ◽

NH Borch ◽

M Søndergaard

Keyword(s):

Functional Similarity ◽

Phytoplankton Blooms ◽

Free Living ◽

Freshwater Phytoplankton ◽

Living Bacteria

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Abundance-occupancy relationships along taxonomic ranks reveal a consistency of niche differentiation in marine bacterioplankton with distinct lifestyles

10.1101/2021.04.09.439152 ◽

2021 ◽

Author(s):

Dandan Izabel-Shen ◽

Anna-Lena Höger ◽

Klaus Jürgens

Keyword(s):

Community Dynamics ◽

16S Rrna Gene Sequencing ◽

Niche Differentiation ◽

Rrna Gene ◽

Free Living ◽

Lawrence Estuary ◽

Marine Bacterioplankton ◽

Niche Differences ◽

Rrna Gene Sequencing ◽

St Lawrence Estuary

Abundance-occupancy relationships (AORs) are an important determinant of biotic community dynamics and habitat suitability. However, little is known about their role in complex bacterial communities, either within a phylogenetic framework or as a function of niche breadth. Based on data obtained in a field study in the St. Lawrence Estuary, we used 16S rRNA gene sequencing to examine the vertical patterns, strength, and character of AORs for particle-attached and free-living bacterial assemblages. Free-living communities were phylogenetically more diverse than particle-attached communities. The dominant taxa were consistent in terms of their presence/absence but population abundances differed in surface water vs. the cold intermediate layer. Significant, positive AORs characterized all of the surveyed communities across all taxonomic ranks of bacteria, thus demonstrating an ecologically conserved trend for both free-living and particle-attached bacteria. The strength of the AORs was low at the species level but higher at the genus and phylum levels. These results demonstrate that an assessment of the distributions and population densities of finely resolved taxa does not necessarily improve determinations of apparent niche differences in marine bacterioplankton communities at regional scales compared with the information inferred from a broad taxonomic classification.

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Symbiosis increases population size and buffers environmental fluctuations in a physiologically-structured model parameterized for thyasirid bivalves

10.1101/2021.06.02.446784 ◽

2021 ◽

Author(s):

Joany Mariño ◽

Suzanne C Dufour ◽

Amy Hurford

Keyword(s):

Population Dynamics ◽

Community Dynamics ◽

Resource Limitation ◽

Symbiotic Bacteria ◽

Free Living ◽

Additional Energy ◽

Structured Population Model ◽

Dynamic Energy Budget Theory ◽

Budget Theory ◽

Living Bacteria

Symbioses whereby one partner provisions a nutritional resource to the other may alter energy allocation towards reproduction and survival in the recipient partner, potentially impacting population dynamics. Asymbiotic thyasirid bivalves feed predominantly on free-living bacteria, which fluctuate in abundance due to seasonality-driven temperature variations. Symbiotic thyasirids are mixotrophs, gaining nutrients from free-living bacteria and symbiotic bacteria that they host on their enlarged gills. Symbiotic bacteria may function as an additional energy reserve for thyasirids, allowing the hosts to allocate more energy to reproduction. We hypothesize that, for symbiotic thyasirids, the symbionts are a nutritional source that mitigates resource limitation. Using Dynamic Energy Budget theory, we built a physiologically-structured population model assuming equal mortality rates in both species. We find that without seasonal fluctuations, symbiotic thyasirids have higher abundances than asymbiotic thyasirids since the symbionts increase reproduction. Both species have similar population sizes in fluctuating environments, suggesting different adaptations to seasonality: asymbiotic thyasirids have adapted their physiology, while symbiotic thyasirids have adapted through mixotrophy. Our results highlight the significance of linking individual energetics and life-history traits to population dynamics and are the first step towards understanding the role of symbioses in population and community dynamics.

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Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic

Biogeosciences Discussions ◽

10.5194/bgd-11-12223-2014 ◽

2014 ◽

Vol 11 (8) ◽

pp. 12223-12254 ◽

Cited By ~ 4

Author(s):

K. H. Salmon ◽

P. Anand ◽

P. F. Sexton ◽

M. Conte

Keyword(s):

Mixed Layer ◽

North Atlantic ◽

Community Dynamics ◽

Phytoplankton Bloom ◽

North Atlantic Ocean ◽

Planktonic Foraminifera ◽

Upper Ocean ◽

Late Winter ◽

Planktonic Foraminifer ◽

Spring Phytoplankton Bloom

Abstract. Oligotrophic regions represent up to 75% of Earth's open-ocean environments, and are typically characterized by nutrient-limited upper-ocean mixed layers. They are thus areas of major importance in understanding the plankton community dynamics and biogeochemical fluxes. Here we present fluxes of total planktonic foraminifera and eleven planktonic foraminifer species from a bi-weekly sediment trap time series in the oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean at 1500 m water depth, over two ∼2.5 year intervals, 1998–2000 and 2007–2010. Foraminifera flux was closely correlated with total mass flux and with carbonate and organic carbon fluxes. We show that the planktonic foraminifera flux increases approximately five-fold during the winter–spring, contributing up to ∼40% of the total carbonate flux, driven primarily by increased fluxes of deeper dwelling ("globorotaliid") species. Interannual variability in total foraminifera flux, and in particular fluxes of the deep dwelling Globorotalia truncatulinoides, Globorotalia hirsuta, Globorotalia inflata, were related to differences in seasonal mixed layer dynamics affecting the strength of the spring phytoplankton bloom and export flux, and by the passage of mesoscale eddies. The heavily calcified, dense carbonate tests of deeper dwelling species (3 times denser than surface dwellers) can contribute up to 90% of the foraminiferal-derived carbonate in this region during late winter-early spring, implying a high seasonality of the biological carbonate pump in oligotrophic oceanic regions. Our data suggest that climate cycles, such as the North Atlantic Oscillation, that modulate the depth of the mixed layer, intensity of nutrient upwelling and primary production could also modulate the strength of the biological carbonate pump in the oligotrophic North Atlantic.

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