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Marine Ecology Progress Series

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MEPS 460:91-100 (2012)  -  DOI:

Epiphytes mediate the trophic role of sea urchins in Thalassia testudinum seagrass beds

Candela Marco-Méndez1,*, Patricia Prado2,3, Kenneth L. Heck4,5, Just Cebrián4,5, Jose Luis Sánchez-Lizaso1

1Departamento de Ciencias del Mar y Biología Aplicada, Universidad de Alicante, Apdo. Correos 99, 03080 Alicante, Spain
2IRTA—Sant Carles de la Ràpita. Ctra. Poble Nou km 5.5, Aptdo. Correos 200, 43540 Sant Carles de la Ràpita, Tarragona, Spain
3Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA
4Dauphin Island Sea Laboratory, 101 Bienville Boulevard, Dauphin Island, Alabama 36528, USA
5Department of Marine Sciences, University of South Alabama, LSCB 25 Mobile, Alabama 36688-0002, USA

ABSTRACT: The trophic role of the sea urchin Lytechinus variegatus (Lamarck) and the importance of epiphytes as mediators of trophic interactions were evaluated in a Thalassia testudinum meadow, St. Joseph Bay, Florida, in fall 2010. Tethering experiments were deployed within the meadow to assess consumption rates, and food choice experiments, with combinations of different types of T. testudinum leaves, green leaves and detached (decayed) leaves, both with and without epiphytes, were carried out with individual urchins in 4 different 24 h feeding trials. Lytechinus variegatus had higher consumption rates on decayed (12.15 ± 1.3 mg DW shoot−1 d−1; mean ± SE) compared to an undetectable consumption of green seagrass leaves, and consistently chose epiphytized leaves of both type. Therefore, consumption rates were highest for decayed leaves with epiphytes. This choice may be related to the significantly higher epiphytic biomass on decayed (3.64 ± 0.28 mg DW cm−2) than on green leaves (2.11 ± 0.25 mg DW cm−2). Stable isotope analyses pointed to epiphytes and green leaves as the main sources of nitrogen and carbon in L. variegatus diet. These results suggest that epiphytes mediate trophic interactions between sea urchins and turtlegrass. Therefore, changes in epiphytes and decayed leaf biomass can regulate sea urchin foraging and its impact on the trophic dynamics of the meadows.

KEY WORDS: Food choice · Lytechinus variegatus · Thalassia testudinum · Epiphytes · Isotopes

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Cite this article as: Marco-Méndez C, Prado P, Heck KL, Cebrián J, Sánchez-Lizaso JL (2012) Epiphytes mediate the trophic role of sea urchins in Thalassia testudinum seagrass beds. Mar Ecol Prog Ser 460:91-100.

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