# Diving deep into kelp forest food webs using dietary DNA metabarcoding

Bonnie Bailet, Jean-charles Leclerc, Thibaut de Bettignies, Pascal Provost, Yannis Turpin, Martial Laurans, Sandrine Derrien-Courtel, Pierre Daniel Thiriet, Erwan Quéméré

► To cite this version:

Bonnie Bailet, Jean-charles Leclerc, Thibaut de Bettignies, Pascal Provost, Yannis Turpin, et al. Div-
ing deep into kelp forest food webs using dietary DNA metabarcoding. 14th International Temperate
Reefs Symposium, Jul 2025, Brest, France. . hal-05149858

HAL Id: hal-05149858

https://hal.science/hal-05149858v1

Submitted on 8 Jul 2025

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# Diving deep into kelp forest food webs using dietary DNA metabarcoding

Bonnie Bailet<fnref n="1" />, Jean-Charles Leclerc<fnref n="2" />, Thibaut de Bettignies<fnref n="3" />,<fnref n="4" />, Pascal Provost<fnref n="5" />, Yannis Turpin<fnref n="6" />, Martial Laurans<fnref n="1" />, Sandrine Derrien⁷, Pierre Thiriet<fnref n="3" />,⁸, Erwan Quéméré<fnref n="1" />

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decod
de la source à l'océan

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CNRS • SORBONNE UNIVERSITÉ
Station Biologique
de Roscoff

## Objectives

Refine our understanding of trophic conditions
supporting the ecological integrity of **Laminaria hyperborea** forests in marine protected areas,
by identifying key 'consumer-prey' interactions.

* Identifying key resources for species of cultural or fisheries importance.

* Assessing their **trophic reliance on kelp forest communities**.

* Delineating **trophic guilds** and analyzing **resource partitioning**.

* Identifying **major trophic linkages** and functional redundancy.

## Methods

Environmental genomics approach based on the **dietary DNA metabarcoding of 18 species** (seals, cormorants, fish and invertebrates, such as urchins, starfish, and crabs).

Two MPAs studied
in Brittany, France

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71% spp. and 77% genera from English Channel kelp forests
with COI sequences available on Barcode of Life Data System (BOLD)

x 20 samples/site

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Dietary composition

> 500 dietary samples analyzed

4100 unique ASVs (COI barcodes)
38% assigned to species (>97% similarity)

> 1,500 trophic interactions identified

Dissection, homogenization
and dietary DNA extraction

Multi-marker COI
metabarcoding

Sequence analysis and
Taxonomic assignment

Species diet and trophic network reconstruction

## Some results...

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Ratio of occurrences at phylum level

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Dietary composition of invertebrates

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## Ressource partitioning between Grey seals and European shags

<figure><img src="image_18.png" /><figcaption>Top 8 most consumed species by sea urchins (Echinus esculentus)</figcaption></figure>

<table><thead><tr><td>Ordre</td><td>Famille</td><td>Espèce</td><td>N occ</td><td>%O</td></tr></thead><tbody><tr><td>Bangiales</td><td>Bangiaceae</td><td>Neoporphyra sp.</td><td>40</td><td>4,21</td></tr><tr><td>Bangiales</td><td>Bangiaceae</td><td>Porphyra umbilicalis</td><td>32</td><td>3,37</td></tr><tr><td>Verrucomorpha</td><td>Verrucidae</td><td>Verruca stroemia</td><td>31</td><td>3,27</td></tr><tr><td>Laminariales</td><td>Laminariaceae</td><td>Laminaria digitata</td><td>31</td><td>3,27</td></tr><tr><td>Haplosclerida</td><td>Chalinidae</td><td>Haliclona sp.</td><td>30</td><td>3,16</td></tr><tr><td>Ectocarpales</td><td>Ectocarpaceae</td><td>Ectocarpus fasciculatus</td><td>30</td><td>3,16</td></tr><tr><td>Sphacelariales</td><td>Stypocaulaceae</td><td>Halopteris filicina</td><td>28</td><td>2,95</td></tr><tr><td>Laminariales</td><td>Laminariaceae</td><td>Laminaria hyperborea</td><td>27</td><td>2,85</td></tr></tbody></table>

## Conclusion

Dietary DNA metabarcoding is a promising tool for biosampling local biodiversity and unravelling trophic interactions in diverse coastal marine ecosystems, offering very high taxonomic resolution and broad taxonomic coverage.

Results suggest that **wrasses** play a **central role in the stability of kelp forest** by regulating numerous benthic invertebrate populations, themselves serving as major source of prey of **shag, sea bass and pollock**.

Dietary DNA from invertebrates, including grazers, suggests a predominant role of kelp and associated epiphytic/epilithic algae at the bottom of the trophic network.

<footnote n="1">¹DECOD, INRAE, Institut Agro, IFREMER, France</footnote>

<footnote n="2">² Sorbonne Université, CNRS, UMR 7144 AD2M, Station Biologique de Roscoff, France</footnote>

<footnote n="3">³PatriNat - Patrimoine naturel (OFB-MNHN-CNRS-IRD), Paris, France</footnote>

<footnote n="4">⁴Centre de Recherche sur la Biodiversité et l'Environnement, Toulouse, France</footnote>

<footnote n="5">⁵ Réserve Naturelle des Sept-Iles ⁷CESCO (MNHN-CNRS-SU), MNHN - Station Marine de Concarneau</footnote>

<footnote n="6">⁶Parc Naturel Marin d'Iroise ⁸Station Marine de Dinard, 38 rue de Port-Blanc, 35800 Dinard</footnote>