Trophic Relationships within Intertidal Communities of the Brittany Coasts: a Stable Carbon Isotope Analysis

Abstract

More than 100 species belonging to plant and animal taxa that are commonly observed in the intertidal zone were collected on both rocky and soft bottom shores of Brittany, France, to be analysed for their ¹³C/¹²C ratio. Plant material displayed a wide range of ᵹ¹³C values (from -12 to -34‰), with relatively distinct values among producer groups (Chlorophyceæ, Fucales, Laminariales, Rhodophyceæ, seagrasses, plankton), and among strata of intertidal zonation. Animal ᵹ¹³C range was narrower (-15 to -22‰), and in general, values differed more between than within phyla or classes, according to the staple diet of organisms. A good correlation between the ᵹ¹³C values of food and consumers was noted, together with a slight ¹³C-enrichment (≈1‰) with increasing trophic levels from suspension-feeders to predators.