Marine Viruses: Community Dynamics, Diversity and Impact on Microbial Processes

Mechanistic simulation models are an essential tool for predicting soil functions such as nutrient cycling, water filtering and storage, productivity and carbon storage as well as the complex interactions between these functions. Most soil functions are driven or affected by soil organisms. Yet, biological processes are often neglected in soil function models or implicitly described by rate parameters. This can be explained by the high complexity of the soil ecosystem with its dynamic and heterogeneous environment, and by the range of temporal and spatial scales these processes are taking place at. On the other hand, the technical capabilities to explore microbial activity and communities in soil has greatly improved, resulting in new possibilities to understand soil microbial processes on various scales.However, to integrate such biological processes in soil modelling, we need to find the right level of detail. Here, we present a systemic soil model approach to simulate the impact of different management options and changing climate on soil functions integrating biological activity on the profile scale. We use stoichiometric considerations to simulate microbial processes involved in different soil functions without explicitly describing community dynamics or functional groups. With this approach we are able to mechanistically describe microbial activity and its impact on the turnover of organic matter and nutrient cycling as driven by agricultural soil management.Further, we discuss general challenges and ongoing developments to additionally consider, e.g., microbe-fauna-interactions or microbial feedback with soil structure dynamics.

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Dimethylsulfoniopropionate in corals and its interrelations with bacterial assemblages in coral surface mucus

Environmental Chemistry ◽

10.1071/en15023 ◽

2016 ◽

Vol 13 (2) ◽

pp. 252 ◽

Cited By ~ 17

Author(s):

P. R. Frade ◽

V. Schwaninger ◽

B. Glasl ◽

E. Sintes ◽

R. W. Hill ◽

...

Keyword(s):

Host Species ◽

Community Dynamics ◽

Sulfur Compound ◽

Quantitative Polymerase Chain Reaction ◽

Sulfur Compounds ◽

Microbial Processes ◽

Coral Host ◽

Gene Abundance ◽

Coral Surface ◽

Degrading Bacteria

Environmental context Corals produce copious amounts of dimethylsulfoniopropionate (DMSP), a sulfur compound implicated in climate regulation. We studied DMSP concentrations inside corals and unveiled the linkage between DMSP availability and the abundance of DMSP-degrading bacterial groups inhabiting the corals’ surface. Our findings suggest that DMSP mediates the interplay between corals and microbes, highlighting the importance of sulfur compounds for microbial processes in corals and for the resilience of coral reef ecosystems. Abstract Corals produce copious amounts of dimethylsulfoniopropionate (DMSP), a sulfur compound thought to play a role in structuring coral-associated bacterial communities. We tested the hypothesis that a linkage exists between DMSP availability in coral tissues and the community dynamics of bacteria in coral surface mucus. We determined DMSP concentrations in three coral species (Meandrina meandrites, Porites astreoides and Siderastrea siderea) at two sampling depths (5 and 25m) and times of day (dawn and noon) at Curaçao, Southern Caribbean. DMSP concentration (4–409nmolcm–2 coral surface) varied with host species-specific traits such as Symbiodinium cell abundance, but not with depth or time of sampling. Exposure of corals to air caused a doubling of their DMSP concentration. The phylogenetic affiliation of mucus-associated bacteria was examined by clone libraries targeting three main subclades of the bacterial DMSP demethylase gene (dmdA). dmdA gene abundance was determined by quantitative Polymerase Chain Reaction (qPCR) against a reference housekeeping gene (recA). Overall, a higher availability of DMSP corresponded to a lower relative abundance of the dmdA gene, but this pattern was not uniform across all host species or bacterial dmdA subclades, suggesting the existence of distinct DMSP microbial niches or varying dmdA DMSP affinities. This is the first study quantifying dmdA gene abundance in corals and linking related changes in the community dynamics of DMSP-degrading bacteria to DMSP availability. Our study suggests that DMSP mediates the regulation of microbes by the coral host and highlights the significance of sulfur compounds for microbial processes in coral reefs.

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Testing ecological release as a compensating mechanism for mass mortality in a keystone predator

Marine Ecology Progress Series ◽

10.3354/meps13227 ◽

2020 ◽

Vol 637 ◽

pp. 59-69 ◽

Cited By ~ 1

Author(s):

J Sullivan-Stack ◽

BA Menge

Keyword(s):

Community Dynamics ◽

Limiting Factor ◽

Sea Star ◽

Top Predator ◽

Oregon Coast ◽

Ecological Release ◽

Keystone Predator ◽

Pisaster Ochraceus ◽

Wasting Syndrome

Top predator decline has been ubiquitous across systems over the past decades and centuries, and predicting changes in resultant community dynamics is a major challenge for ecologists and managers. Ecological release predicts that loss of a limiting factor, such as a dominant competitor or predator, can release a species from control, thus allowing increases in its size, density, and/or distribution. The 2014 sea star wasting syndrome (SSWS) outbreak decimated populations of the keystone predator Pisaster ochraceus along the Oregon coast, USA. This event provided an opportunity to test the predictions of ecological release across a broad spatial scale and determine the role of competitive dynamics in top predator recovery. We hypothesized that after P. ochraceus loss, populations of the subordinate sea star Leptasterias sp. would grow larger, more abundant, and move downshore. We based these predictions on prior research in Washington State showing that Leptasterias sp. competed with P. ochraceus for food. Further, we predicted that ecological release of Leptasterias sp. could provide a bottleneck to P. ochraceus recovery. Using field surveys, we found no clear change in density or distribution in Leptasterias sp. populations post-SSWS, and decreases in body size. In a field experiment, we found no evidence of competition between similar-sized Leptasterias sp. and P. ochraceus. Thus, the mechanisms underlying our predictions were not in effect along the Oregon coast, which we attribute to differences in habitat overlap and food availability between the 2 regions. Our results suggest that response to the loss of a dominant competitor can be unpredictable even when based in theory and previous research.

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The Township, the Pregnant Girl and the Church: Community Dynamics, Gender and Social Control in Early Nineteenth-century Scotland

Northern Scotland ◽

10.3366/nor.2019.0168 ◽

2019 ◽

Vol 10 (1) ◽

pp. 41-67

Author(s):

Elizabeth Ritchie

Keyword(s):

Nineteenth Century ◽

Rural Communities ◽

Social Control ◽

Community Dynamics ◽

Church Discipline ◽

Sexual Offences ◽

Early Nineteenth Century ◽

Female Community ◽

The Church ◽

Unmarried Girl

In 1814 in a small Highland township an unmarried girl, ostracised by her neighbours, gave birth. The baby died. The legal precognition permits a forensic, gendered examination of the internal dynamics of rural communities and how they responded to threats to social cohesion. In the Scottish ‘parish state’ disciplining sexual offences was a matter for church discipline. This case is situated in the early nineteenth-century Gàidhealtachd where and when church institutions were less powerful than in the post-Reformation Lowlands, the focus of most previous research. The article shows that the formal social control of kirk discipline was only part of a complex of behavioural controls, most of which were deployed within and by communities. Indeed, Scottish communities and churches were deeply entwined in terms of personnel; shared sexual prohibitions; and in the use of shaming as a primary method of social control. While there was something of a ‘female community’, this was not unconditionally supportive of all women nor was it ranged against men or patriarchal structures.

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