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Marine Ecology Progress Series

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MEPS 429:45-55 (2011)  -  DOI:

Seagrass selection by omnivorous and herbivorous consumers: determining factors

Patricia Prado1,*, Kenneth L. Heck Jr.2

1Institut de Recerca i Tecnología Agroalimentàries (IRTA), Aquatic Ecosystems, Ctra. Poble Nou km 5.5,
43540 Sant Carles de la Ràpita, Tarragona, Spain
2Dauphin Island Sea Lab. 101, Bienville Boulevard, Dauphin Island, 36528 Alabama, USA

ABSTRACT: Consumers of seagrasses are increasingly recognized for their ability to shape landscape features and regulate energy flux in coastal ecosystems. To date, however, the nutritional characteristics and morphological features by which herbivores and omnivores make feeding decisions are poorly understood. To elucidate how consumers of marine vascular plants discriminate among different food resources, we conducted food-preference assays with seagrass leaves and seagrass-incorporated agar diets of the 3 most common seagrass species of the Gulf of Mexico (Thalassia testudinum, Halodule wrightii and Syringodium filiforme). These 3 species were offered simultaneously to the most abundant local consumers: the omnivorous pinfish Lagodon rhomboides and filefish Stephanolepis hispidus, the herbivorous emerald parrotfish Nicholstina usta, and the herbivorous sea urchin Lytechinus variegatus. Consumption rates (g fresh weight [FW]) of leaves or seagrass-incorporated agar diets were estimated over 24 h periods. Measured plant properties included C:N, N:P, total carbohydrates, protein and lipid concentrations, caloric content, percentage of organic matter, water and ash. Results showed that S. filiforme was preferred by all fish species (81, 60.2 and 59% of total leaf consumption of pinfish, filefish and parrotfish, respectively), whereas sea urchins consumed the highest amounts of H. wrightii (71.2% of total). However, when leaf structure was removed, by incorporating ground leaf tissue into agar matrices, pinfish and filefish did not show any significant dietary preference. In contrast, parrotfish and sea urchins maintained their preferences for S. filiforme and H. wrightii, respectively. Parrotfish preference for S. filiforme coincided with highest lipid and carbohydrate contents, whereas the preference of sea urchins for H. wrightii could be explained by higher levels of the percentage of organic matter and caloric content. Our results suggest that structural plant features (e.g. leaf manipulability and/or visual recognition of resources) are the most important factors driving discrimination between seagrass species by omnivorous fish, whereas strict herbivores make feeding decisions that are highly influenced by nutritional characteristics, presumably as recognized by both olfaction and gustation.

KEY WORDS: Plant structure · Nutritional quality · Fish · Sea urchins · Feeding decision

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Cite this article as: Prado P, Heck KL (2011) Seagrass selection by omnivorous and herbivorous consumers: determining factors. Mar Ecol Prog Ser 429:45-55.

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