Abstract
Marine wood-borers often live in sympatry, sharing deadwood scattered at sea, both as food and habitat. In this study, carbon and nitrogen isotope compositions were determined to test the hypothesis that the trophic niches of Chelura terebrans, Limnoria quadripunctata, and Nototeredo norvagica obtained from softwood boards maintained in running, unfiltered seawater are different. Comparison of isotope compositions supports niche partitioning, with N. norvagica foraging primarily on wood, and crustaceans foraging on decaying wood. Needs and acquisition routes for nitrogen determine the trophic behavior of the species. Results presented here are valuable for assessing the impact of wood-boring species on each other, but also for evaluating the effect of the separation of carbon and nitrogen sources on the diversity of the interactions between co-existing species belonging to the same trophic guild.
Highlights
Since the Devonian, a large amount of wood produced on land has been entering the sea, where some consumers are specialized to use this organic matter with great efficiency
Visible deterioration remained limited to the surface of the wood pieces and was clearly the result of the activity of the gribble, i.e. the isopod Limnoria quadripunctata Holthuis, 1949 and, to a lesser extent, that of the amphipod Chelura terebrans Philippi, 1839
Our results suggest that this is need by ingesting the microbes that creep into and the case for N. norvagica, given that (1) the δ15N grow on the wood (Cragg et al 1999), leading to value for dissolved marine N2 is about 0.6 ‰ (Sigman et al 2009), (2) the fractionation factor between N2 and the diazotrophs is small (Sigman et al 2009), and higher δ15N values compared to shipworms
Summary
Since the Devonian, a large amount of wood produced on land has been entering the sea, where some consumers are specialized to use this organic matter with great efficiency. Communities depending on large woody debris consist mainly of the amphipods from the family Cheluridae (Barnard 1959), most the representatives of the Teredinidae bivalve family (Distel et al 2017, Velásquez & Shipway 2018), and most isopods of the family Limnoriidae (Cragg et al 1999, Cookson et al 2012) Species belonging to these 3 taxonomic groups often live in sympatry, using deadwood scattered at sea both as food source and habitat (Björdal & Nilsson 2008, Cragg et al 2009, Heise et al 2011, Borges & Costa 2014, Borges et al 2014a,b, Nishimoto et al 2015). Large-size worm-like bivalves, better known as shipworms, dig burrows deep into wood (Turner 1966), small-size limnoriids dig tunnels right below the surface of the wood (Menzies 1952), while chelurid amphipods only produce superficial furrows or widen existing limnoriid tunnels (Barnard 1955) Such differences of behaviors suggest that the co-occurring wood-consumers do not compete for, but rather share the resource
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