%0 Journal Article %J Frontiers in Ecology and Evolution %D 2021 %T The Merits of Loop Analysis for the Qualitative Modeling of Social-Ecological Systems in Presence of Offshore Wind Farms %A Nathalie Niquil %A Scotti, Marco %A Fofack-Garcia, Rhoda %A Haraldsson, Matilda %A Thermes, Maud %A Raoux, Aurore %A Le Loc'h, Francois %A Mazé, Camille %B Frontiers in Ecology and Evolution %V 9 %8 May-02-2022 %G eng %U https://www.frontiersin.org/articles/10.3389/fevo.2021.635798/full %! Front. Ecol. Evol. %R 10.3389/fevo.2021.635798 %0 Journal Article %J The ISME Journal %D 2018 %T Microbial parasites make cyanobacteria blooms less of a trophic dead-end than commonly assumed %A Haraldsson, Matilda %A Mélanie Gerphagnon %A Bazin, Pauline %A Samuele Tecchio %A Télésphore Sime-Ngando %A Nathalie Niquil %X

Les parasites sont présents dans tous les écosystèmes et peuvent être à l’origine de changements dans la structure et le fonctionnement des réseaux trophiques. Cependant, à ce jour, nos connaissances concernant les effets des parasites sur la dynamique des réseaux trophiques restent limitées. Dans cette étude, nous analysons le rôle de parasites microbiens (virus de bactéries, phytoplancton et cyanobactéries, et des chitrides parasites des cyanobactéries) sur le transfert d’énergie et le fonctionnement du réseau trophique au cours d’un bloom de cyanobactérie à l’aide d’un modèle d’Analyse Inverse Linéaire. Cette modélisation a permis de mettre en évidence l’importance du broutage sur les bactéries hétérotrophes à travers la voie microbienne (DOC -> bactéries -> consommateurs), ainsi que la dépendance des consommateurs vis à vis des bactéries notamment pendant les blooms de cyanobactéries. Au fur et à mesure que les bactéries deviennent la principale source d'énergie des consommateurs, le système adopte une structure plus complexe, en réseau, s’accompagnant d’une augmentation de l’omnivorie du système. Cette dernière pourrait être à l’origine d’une augmentation de la capacité du système à résister à l’efflorescence des cyanobactéries. Finalement, nous avons également mis en évidence les effets de la destruction des cellules hôtes des cyanobactéries par les chitrides sur la dynamique du réseau trophique. En effet, cette dernière faciliterait le broutage des cyanobactéries et offrirait des voies alternatives aux consommateurs, ce qui augmenteraient la stabilité du système.

 

Parasites exist in every ecosystem and can have large influence on food-web structure and function, yet, we know little about parasites’ effect on food-web dynamics. Here we investigate the role of microbial parasitism (viruses of bacteria, phytoplankton and cyanobacteria, and parasitic chytrids on cyanobacteria) on the dynamics of trophic pathways and food-web functioning during a cyanobacteria bloom, using linear inverse food-web modeling parameterized with a 2-month long dataset (biomasses, infection parameters, etc.). We show the importance of grazing on heterotrophic bacteria (the microbial pathway: DOC -> bacteria -> consumer) and how consumers depended on bacteria during peak-cyanobacteria bloom, which abundance was partly driven by the viral activity. As bacteria become the main energy pathway to the consumers, the system takes a more web-like structure through increased omnivory, and may thereby facilitate the system’s persistence to the cyanobacteria outbreak. We also showed how the killing of cyanobacteria host-cells by chytrids had important impact on the food-web dynamics by facilitating grazing on the cyanobacteria, and by offering alternative pathways to the consumers. This seemed to increase the system’s ability to return to a mix of trophic pathways, which theoretically increases the stability of the system.

%B The ISME Journal %V 12 %P 1008-1020 %G eng %U https://doi.org/10.1038/s41396-018-0045-9 %R 10.1038/s41396-018-0045-9 %0 Journal Article %J Ecological indicators %D 2017 %T Benthic and fish aggregation inside an offshore wind farm: Which effects on the trophic web functioning? %A Raoux, Aurore %A Samuele Tecchio %A Pezy, Jean-Philippe %A Géraldine Lassalle %A Degraer, Steven %A Wilhelmsson, Dan %A Cachera, Marie %A Ernande, Bruno %A Le Guen, Camille %A Haraldsson, Matilda %A Karine Grangeré %A Le Loc'h, Francois %A Dauvin, Jean-Claude %A Nathalie Niquil %X

As part of the energy transition, the French government is planning the construction of three offshore wind farms in Normandy (Bay of Seine and eastern part of the English Channel, north-western France) in the next years. These offshore wind farms will be integrated into an ecosystem already facing multiple anthropogenic disturbances such as maritime transport, fisheries, oyster and mussel farming, and sediment dredging. Currently no integrated, ecosystem-based study on the effects of the construction and exploitation of offshore wind farms exists, where biological approaches generally focused on the conservation of some valuable species or groups of species. Complementary trophic web modelling tools were applied to the Bay of Seine ecosystem (to the 50 km(2) area covered by the wind farm) to analyse the potential impacts of benthos and fish aggregation caused by the introduction of additional hard substrates from the piles and the turbine scour protections. An Ecopath ecosystem model composed of 37 compartments, from phytoplankton to seabirds, was built to describe the situation ``before{''} the construction of the wind farm. Then, an Ecosim projection over 30 years was performed after increasing the biomass of targeted benthic and fish compartments. Ecological Network Analysis (ENA) indices were calculated for the two periods, ``before{''} and ``after{''}, to compare network functioning and the overall structural properties of the food web. Our main results showed (1) that the total ecosystem activity, the overall system omnivory (proportion of generalist feeders), and the recycling increased after the construction of the wind farm; (2) that higher trophic levels such as piscivorous fish species, marine mammals, and seabirds responded positively to the aggregation of biomass on piles and turbine scour protections; and (3) a change in keystone groups after the construction towards more structuring and dominant compartments. Nonetheless, these changes could be considered as limited impacts of the wind farm installation on this coastal trophic web structure and functioning. (C) 2016 Elsevier Ltd. All rights reserved.

%B Ecological indicators %V 72 %P 33-46 %8 01/2017 %G eng %R 10.1016/j.ecolind.2016.07.037