Distinctive types of leaf tissue damage influence nutrient supply to growing tissues within seagrass shoots |
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Authors: | Patricia Prado Catherine J Collier Javier Romero Teresa Alcoverro |
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Institution: | 1.Institut de Re?erca i Tecnologia Agroalimentàries,Sant Carles de la Ràpita,Sant Carles de la Ràpita, Tarragona,Spain;2.School of Marine and Tropical Biology,James Cook University,Townsville,Australia;3.Departamento de Ecología, Facultad de Biología,Universidad de Barcelona,Barcelona,Spain;4.Centre d’Estudis Avan?ats de Blanes,CSIC,Blanes, Girona,Spain |
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Abstract: | Herbivory is now recognized as an important structuring agent in seagrass meadows but the attack pattern and tissue damage
of consumers are highly variable. Nutritional preferences of herbivores and/or easy access to resources may cause differences
in biomass loss among tissues that damage the plant in functionally distinctive ways. The two main Mediterranean herbivores,
the fish Sarpa salpa (L.) and the sea urchin Paracentrotus lividus (Lmk.), remove higher amounts of intermediate and external shoot leaves, respectively. To test whether this selective feeding
can have different consequences on the allocation patterns of nutrient within plants, we simulated the effect of both herbivores
by clipping external and intermediate leaves (plus unclipped controls) of Posidonia oceanica (L.) and we measured plant tolerance in terms of shoot growth and leaf nutrient supply to new tissue using isotopic markers.
As expected, control treatments displayed high carbon and nutrient supply from external leaves (83% of the total 15N and 84% of the total 13C incorporated by the shoot). When subjected to clipping, the remaining leaves enhanced carbon and nitrogen supply compared
with the control by 16% of N and 36% of C—in the intermediate clipping—and by over 100% of N and 200% of C—in the external
clipping—to compensate for the nutrient lost. However, only in the case of fish herbivory (intermediate clipping), enhanced
supply alone was able to fully compensate for the nutrient losses. In contrast, this mechanism is not completely effective
when external leaves are clipped (urchin herbivory). Yet, the consequences of this nutrient loss under sea urchin herbivory
are not apparent from the nutrient content of the new tissue, suggesting that there are other sources of nitrogen income (uptake
or reallocation from rhizomes). Our study does not only confirm the tolerance of P. oceanica to herbivory, but also constitutes the first evidence of leaf-specific, compensatory nutrient supply in seagrasses. |
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