Sources of organic matter for flatfish juveniles in coastal and estuarine nursery grounds: A meta-analysis for the common sole (Solea solea) in contrasted systems of Western Europe

Abstract

Shallow and productive areas provide the high food supply that allows maximizing juvenile growth and survival in most flatfish species. However, the main organic matter sources at the basis of benthic food webs might differ drastically between estuarine nursery grounds under strong freshwater influences, where food webs are mainly supported by continental organic matter, and coastal ecosystems under limited freshwater influence, where the local marine primary production is the main source of carbon for the benthos. To better understand the links between continental inputs to the coastal zone and stock maintenance in the highly prized common sole, Solea solea (L.), we investigated the variability in the organic matter sources supporting the growth of its young-of-the-year (YoY) in five contrasted estuarine and coastal nursery grounds under varying freshwater influence. Stable isotopes of carbon and nitrogen allowed tracing the origin of the organic matter exploited by YoY soles in the very first months following their benthic settlement, i.e. when most of the juvenile mortality occurs in the species. A mixing model was run to unravel and quantify the contribution of all major potential sources of organic matter to sole food webs, with a sensitivity analysis allowing assessment of the impact of various trophic enrichment factors on model outputs. Thismeta-analysis demonstrated a relative robustness of the estimation of the respective contributions of the various organic matter sources. At the nursery scale, the upstream increase in freshwater organic matter exploitation by YoY soles and its positive correlation with inter-annual variations in the river flow confirmed previous conclusions about the importance of organic matter from continental origin for juvenile production. However, inter-site differences in the organic matter sources exploited for growth showed that, although freshwater organic matter use is significant in all nursery sites, it is never dominant, with especially high contributions of local primary production by microphytobenthos or saltmarsh macrophytes to juvenile sole growth in tidal nursery ecosystems. These patterns stress the need for maintaining both the intensity of freshwater inputs to the coastal zone and of local autochthonous primary production (especially that of the intertidal microphytobenthos) to preserve the nursery function of coastal and estuarine ecosystems

Functional roles of an engineer species for coastal benthic invertebrates and demersal fish

“…One persistent pattern, however, is the exclusion of flatfish from Haploops habitats in the two bays. This agrees with the literature dedicated to flatfish, such as that for S. solea (Kopp, Le Bris, Grimaud, Nerot, & Brind'Amour, ; Le Pape et al., ).…”

“…On the Atlantic coast, the Bay of Concarneau and the Bay of Vilaine are recognized as essential nurseries for many exploited fish species, particularly marine bentho‐demersal species (Beck et al., ; Le Pape et al., , ; Trimoreau, Archambault, Brind'Amour, Guitton, & Le Pape, ). This study focuses on these two coastal bays in the northern Bay of Biscay (southern Brittany; Figure a,b).…”

Identification of the main processes underlying ecosystem functioning in the Eastern English Channel, with a focus on flatfish species, as revealed through the application of the Atlantis end-to-end model

“…dependent functional groups, especially sole and plaice. These results bear out the crucial importance of estuaries on the nurseries productivity (Kostecki et al, 2010;Le Pape et al, 2013;Riou et al, 2001;Rochette et al, 2010).…”

Feeding strategies and body condition of juvenile European flounderPlatichthys flesusin a nursery habitat

“…Carbon (δ 13 C) stable isotope ratios help to explain the diet composition of consumers (DeNiro & Epstein, 1978;Fry & Sherr, 1989), while δ 15 N can also indicate trophic position (DeNiro & Epstein, 1981;Post, 2002). Recently, stable isotope mixing models (Parnell et al, 2013;Phillips et al, 2014) have been used to identify the main prey and organic matter sources (Le Pape et al, 2013;Hoffman et al, 2015;Dias et al, 2017), and to characterize trophic niche widths and niche overlap between species (Kostecki et al, 2012;Vaslet et al, 2015). This information may then be integrated to track movements over variable temporal and spatial scales, and identify key habitats regarding food use (Green et al, 2012;Kopp et al, 2013;Selleslagh et al, 2015).…”