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Stable isotope analyses reveal the importance of seagrass beds as feeding areas for juvenile Myrophic punctatus in Florida
Citation:
Vaslet, A., C. France, D. L. PHILLIPS, I. C. Feller, AND C. C. Baldwin. Stable isotope analyses reveal the importance of seagrass beds as feeding areas for juvenile Myrophic punctatus in Florida. JOURNAL OF FISH BIOLOGY. Blackwell Publishing, Malden, MA, 79:692-706, (2011).
Impact/Purpose:
The feeding habits and habitats of the speckled worm eel Myrophis punctatus were studied on the mangrove edge of the Indian River Lagoon (Florida) using stomach contents and stable isotope analyses of carbon (δ13C) and nitrogen (δ15N).
Description:
The feeding habits and habitats of the speckled worm eel Myrophis punctatus were studied on the mangrove edge of the Indian River Lagoon (Florida) using stomach contents and stable isotope analyses of carbon (δ13C) and nitrogen (δ15N). Stomach dietary analyses identified four taxa and the index of relative importance suggested amphipods, microphytobenthos and annelids as the most important food sources in the eel’s diet. To assess the feeding behaviour of the eels after their recruitment in coastal waters, these food sources were collected in mangroves and nearby seagrass beds for isotope analyses. Stable isotopes constitute a powerful tool for discriminating prey items from mangroves (δ13Cmean = -20.5±0.6‰) and seagrass beds (δ13Cmean = -16.9±0.6‰) thus providing good evidence of food-source origins. The 56 eels collected (10 < Total Length < 16.2 cm) presented average isotopic signatures of -16.7±0.2‰ in δ13C and 8.2±0.1‰ in δ15N. A significant depletion in 13C was observed for larger juveniles (LT = 15/16.2cm), suggesting that these eels found a part of their food in mangroves. Estimation of the trophic level from stable isotopes (TLiso) is similar among the different size groups of eels (TLiso = 3.2 to 3.5), therefore M. punctatus is considered as a secondary consumer, which concurs with its benthic diet. The concentration-dependent mixing model SIAR revealed the importance of food sources from seagrass beds as carbon sources for all the eels collected with a slight increase of mangrove prey contributions, such as annelids, in the diet of larger eels. This study highlights the role of seagrass beds as feeding habitats for juveniles of M. punctatus after their recruitment in coastal waters.