Structure and Trophic Niches in Mobile Epifauna Assemblages Associated With Seaweeds and Habitats of Syngnathid Fishes in Cíes Archipelago (Atlantic Islands Marine National Park, North West Iberia)

Cristina Piñeiro-Corbeira,Rodolfo Barreiro,Raquel Nogueira,Marcos Regueira,Sara Campos,Miquel Planas,Arturo Jiménez,Laura Iglesias

doi:10.3389/fmars.2021.773367

Cristina Piñeiro-Corbeira, Rodolfo Barreiro + Show 6 more

Open Access

https://doi.org/10.3389/fmars.2021.773367

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Abstract

Syngnathids are vulnerable fishes closely associated with seaweeds and seagrass, which provide shelter and food resources. Even though most syngnathids commonly feed on small crustaceans, the feeding regimes may differ depending on the species and prey availability. This is the first monitoring study to explain syngnathid abundances and dietary regimes within macroalgal beds in Cíes Archipelago (Atlantic Islands Marine National Park, North West Iberian Peninsula). We sampled the epifaunal assemblages in seaweed communities dominated by the canopy-forming macroalgaeGongolaria baccataandCodiumspp. seasonally during 2 years. The epifaunal structure was mostly represented by harpacticoid copepods, amphipods (especially gammarids) and gastropods. Epifauna exhibited low plant-host specificity and a higher dominance of amphipods on the more structurally complex macroalgaeG. baccata.The epifaunal assemblages and syngnathid specimens were assessed for trophic structure using stable isotopes (δ13C and δ15N). The three syngnathids (Hippocampus guttulatus,Syngnathus acus, andEntelurus aequoreus) inhabiting Cíes Archipelago were sympatric. They occupied highly similar trophic positions (TPs), but differed in niche size, in such a way that the snake pipefishE. aequoreuswould likely feed on smaller prey. The assessment of the feeding regime in the dominant great pipefishS. acusrevealed that amphipods mostly contributed to bulk diet, followed by isopods, carideans, and copepods, whereas mysidaceans were not highly consumed. Seasonal changes in both epifaunal structure and syngnathids abundance confirmed that syngnathids are seasonal residents in Cíes Archipelago, migrating to other areas in autumn when the seaweed cover is drastically reduced and the epifaunal structure modified. This study showed the importance ofGongolariaassemblages in Cíes Archipelago, providing rich dietary sources and potentially contributing to higher abundances and diversity of syngnathids. Ongoing cover reduction inGongolariaassemblages in certain regions (e.g., Mediterranean) should be considered a potential ecological concern for syngnathids and accompanying fauna, requiring further investigations.

Highlights

Marine seaweeds and seagrasses are important benthic primary producers housing a great variety of small motile animals, with many different life forms, ecological characteristics and trophic patterns (Orth, 1973; Adams, 1976; Zimmerman et al, 1979; Orth et al, 1984; Edgar and Moore, 1986; Franco et al, 2006; Horinouchi et al, 2012)
The main aims of our study were: (1) to qualitatively and quantitatively characterize epifaunal assemblages associated with algal communities in marine environments inhabited by syngnathid fishes on Cíes Archipelago (Atlantic Islands National Park, NW Spain); (2) to determine the host-plant specificity of the mobile epifauna in two main foundation seaweeds (G. baccata and Codium spp.); (3) to assess the structure and characteristics of the food web supporting syngnathid fishes, and (4) to evaluate trophic similarities across sympatric syngnathid species present in the National Park
A total of 82 Operating Taxonomic Units (OTUs) or multispecies groupings were identified in epifauna samples seasonally collected in 2017–2018 in Cíes Archipelago (Supplementary Table 2)

Summary

Introduction

Marine seaweeds and seagrasses are important benthic primary producers housing a great variety of small motile animals, with many different life forms, ecological characteristics and trophic patterns (Orth, 1973; Adams, 1976; Zimmerman et al, 1979; Orth et al, 1984; Edgar and Moore, 1986; Franco et al, 2006; Horinouchi et al, 2012). The abundance and distribution of epifauna differ among seaweeds, being strongly influenced by the architecture of the host macroalgae (Viejo, 1999; Villegas et al, 2008; Moore and Hovel, 2010; Png-González et al, 2014; Torres et al, 2015). The abundance of many epifaunal organisms in marine macrophytes may be positively related to the algal biomass (Chen et al, 2020), the root-rhizome mat, and/or the plant canopy (Orth et al, 1984), showing a preference for seaweeds with high morphological complexity (Gee and Warwick, 1994)

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