Small-scale and regional spatial dynamics of an annual plant with contrasting sexual systems

Although methane is a widely studied greenhouse gas, uncertainties remain with respect to the factors controlling its distribution and diffusive flux into the atmosphere, especially in highly dynamic coastal waters. In the southern North Sea, the Elbe and Weser rivers are two major tributaries contributing to the overall methane budget of the southern German Bight. In June 2019, we continuously measured methane and basic hydrographic parameters at a high temporal and spatial resolution (one measurement per minute every 200–300 m) on a transect between Cuxhaven and Helgoland. These measurements revealed that the overall driver of the coastal methane distribution is the dilution of riverine methane-rich water with methane-poor marine water. For both the Elbe and Weser, we determined an input concentration of 40–50 nmol/L compared to only 5 nmol/L in the marine area. Accordingly, we observed a comparatively steady dilution pattern of methane concentration toward the marine realm. Moreover, small-scale anomalous patterns with unexpectedly higher dissolved methane concentrations were discovered at certain sites and times. These patterns were associated with the highly significant correlations of methane with oxygen or turbidity. However, these local anomalies were not consistent over time (days, months). The calculated diffusive methane flux from the water into the atmosphere revealed local values approximately 3.5 times higher than background values (median of 36 and 128 μmol m–2 d–1). We evaluate that this occurred because of a combination of increasing wind speed and increasing methane concentration at those times and locations. Hence, our results demonstrate that improved temporal and spatial resolution of methane measurements can provide a more accurate estimation and, consequently, a more functional understanding of the temporal and spatial dynamics of the coastal methane flux.

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Investigating microscale patchiness of motile microbes driven by the interaction of turbulence and gyrotaxis in a 3D simulated convective mixed layer.

10.21203/rs.3.rs-152503/v2 ◽

2021 ◽

Author(s):

Alexander Christensen ◽

Matthew Piggott ◽

Erik van Sebille ◽

Maarten van Reeuwijk ◽

Samraat Pawar

Keyword(s):

Mixed Layer ◽

Fluid Model ◽

Spatial Dynamics ◽

Critical Factor ◽

Trophic Levels ◽

Small Scale ◽

Swimming Velocity ◽

Primary Role ◽

Fluid Surface ◽

Convective Mixed Layer

Abstract Microbes play a primary role in aquatic ecosystems and biogeochemical cycles. Spatial patchiness is a critical factor underlying these activities, influencing biological productivity, nutrient cycling and dynamics across trophic levels. Incorporating spatial dynamics into microbial models is a long-standing challenge, particularly where small-scale turbulence is involved. Here, we combine a fully 3D direct numerical simulation of convective mixed layer turbulence, with an individual-based microbial model to test the key hypothesis that the coupling of gyrotactic motility and turbulence drives intense microscale patchiness. The fluid model simulates turbulent convection caused by heat loss through the fluid surface, for example during the night, during autumnal or winter cooling or during a cold-air outbreak. We find that under such conditions, turbulence-driven patchiness is depth-structured and requires high motility: Near the fluid surface, intense convective turbulence overpowers motility, homogenising motile and non-motile microbes approximately equally. At greater depth, in conditions analogous to a thermocline, highly motile microbes can be over twice as patch-concentrated as non-motile microbes, and can substantially amplify their swimming velocity by efficiently exploiting fast-moving packets of fluid. Our results substantiate the predictions of earlier studies, and demonstrate that turbulence-driven patchiness is not a ubiquitous consequence of motility but rather a delicate balance of motility and turbulent intensity.

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Small-scale convective turbulence constrains microbial patchiness

10.21203/rs.3.rs-152503/v1 ◽

2021 ◽

Author(s):

Alexander Christensen ◽

Matthew Piggott ◽

Erik van Sebille ◽

Maarten van Reeuwijk ◽

Samraat Pawar

Keyword(s):

Aquatic Ecosystems ◽

Spatial Dynamics ◽

Biogeochemical Cycles ◽

Trophic Levels ◽

Small Scale ◽

Primary Role ◽

Biological Productivity ◽

Convective Turbulence ◽

Scale Turbulence ◽

Microbial Model

Abstract Microbes play a primary role in aquatic ecosystems and biogeochemical cycles. Patchiness is a critical component of these activities, influencing biological productivity, nutrient cycling and dynamics across trophic levels. Incorporating spatial dynamics into microbial models is a long-standing challenge, particularly where small-scale turbulence is involved. Here, we combine a realistic simulation of turbulence with an individual-based microbial model to test the key hypothesis that the coupling of motility and turbulence drives intense microscale patchiness. We find that such patchiness is depth-structured and requires high motility: Near the fluid surface, strong convective turbulence overpowers motility, homogenising motile and non-motile microbes equally. In deeper, thermocline-like conditions, highly motile microbes are up to 1.6-fold more patch-concentrated than non-motile microbes. Our results demonstrate that the delicate balance of turbulence and motility that triggers micro-scale patchiness is not a ubiquitous consequence of motility, and that the intensity of such patchiness in real-world conditions is modest.

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Sexual Systems and Population Genetic Structure in an Annual Plant: Testing the Metapopulation Model

The American Naturalist ◽

10.2307/3844758 ◽

2006 ◽

Vol 167 (3) ◽

pp. 354

Author(s):

Obbard ◽

Harris ◽

Pannell

Keyword(s):

Genetic Structure ◽

Population Genetic Structure ◽

Population Genetic ◽

Annual Plant ◽

Metapopulation Model ◽

Sexual Systems

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Small-scale spatial dynamics in a fluctuating ungulate population

Journal of Animal Ecology ◽

10.1046/j.1365-2656.1999.00298.x ◽

1999 ◽

Vol 68 (4) ◽

pp. 658-671 ◽

Cited By ~ 76

Author(s):

Tim Coulson ◽

Steve Albon ◽

Jill Pilkington ◽

Tim Clutton-Brock

Keyword(s):

Spatial Dynamics ◽

Small Scale

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Temporal and spatial dynamics of predation in a robber fly (Efferia staminea) population (Diptera: Asilidae)

Canadian Journal of Zoology ◽

10.1139/z92-213 ◽

1992 ◽

Vol 70 (8) ◽

pp. 1546-1552 ◽

Cited By ~ 4

Author(s):

Kevin M. O'Neill

Keyword(s):

Prey Availability ◽

Spatial Scales ◽

Large Population ◽

Spatial Dynamics ◽

Population Level ◽

Management Program ◽

Small Scale ◽

Generalist Predator ◽

Robber Flies ◽

Temporal And Spatial

To determine the effect of short-term temporal and small-scale spatial variation in availability of specific prey groups, field studies of prey use by a population of the robber fly Efferia staminea were undertaken. In one study, the appearance of mating swarms of winged males of the ant Formica subpolita was associated with a rapid increase in the proportion of E. staminea observed feeding, and an increase in the proportion of these ants taken as prey. The change in diet occurred over the same time scale as the change in the activity of the ants. When the swarms were absent from the same area, the fewer E. staminea observed feeding utilized a greater diversity of prey taxa and sizes. The proportion of conspecifics in prey records during swarms of F. subpolita was only one-tenth of that during non-swarm intervals, suggesting that high alternative prey availability decreases the incidence of cannibalism in this species. In the second study, E. staminea used a wider diversity of prey on an area of grassland with native vegetation than on a nearby area of grassland that had been reseeded with the grass Agropyron intermedium as part of a range-management program. In the latter area, a large population of crambine moths supplied a major portion of the robber flies' diet. The results of this population-level study illustrate the fine scale over which the composition of the diet of E. staminea varies, and show that the diet of a generalist predator is a function of the temporal and spatial scales over which sampling occurs. The implications of the data for interpreting the composition of the diet, population dynamics, and impact upon prey communities of robber flies are discussed.

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