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Marine Ecology Progress Series

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MEPS 432:69-82 (2011)  -  DOI:

Top-down and bottom-up regulation in a high nutrient–high herbivory coastal ecosystem

Paulina Martinetto1,2,*, Mirta Teichberg3, Ivan Valiela4, Diana Montemayor1,2, Oscar Iribarne1,2

1Lab. de Ecología, Dpto. de Biología (FCEyN), Universidad Nacional de Mar del Plata, CC 573 Correo Central B7600WAG, Mar del Plata, Argentina
2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Avda. Rivadavia 1917, Buenos Aires, Argentina
3Leibniz-Zentrum für Marine Tropenökologie, Fahrenheitstrasse 6, 28359 Bremen, Germany
4The Ecosystems Center, Marine Biological Laboratory, 7 MBL St., Woods Hole, Massachusetts 02543, USA

ABSTRACT: In this study, carried out in San Antonio Bay (Northern Argentinean Patagonia), we aimed to understand the relative importance of bottom-up and top-down controls on macroalgal blooms in a macrotidal system with high nutrient supply and high consumer abundance. Our results show that nutrients, pH, and O2 concentrations were higher during low tide. A field experiment showed that the biomass accumulation rate of Ulva lactuca ranged from 6 to 12% d–1 and was reduced by herbivory by 60%. The biomass accumulation rate did not differ in thalli with different initial internal nutrient pools. There was a negative relationship between the percentage of algae consumed and the N content in algal tissues, suggesting compensatory feeding by herbivores. Herbivory reduced the biomass accumulation rate of U. lactuca when PO43– or no nutrients were added, but not when NO3 was added. In the absence of herbivory, the addition of nutrients did not increase U. lactuca biomass accumulation rate. These results suggest that nutrients remain high enough for adequate time intervals to be assimilated by macroalgae and support blooms. Large water exchange during tidal changes, however, can diminish the potential negative effects of macroalgal accumulation (oxygen depletion, high ammonium concentrations) on herbivores such that herbivores can have a large impact on macroalgae.

KEY WORDS: Top-down vs. bottom-up controls · Coastal eutrophication · Tidal influence · Ulva lactuca · Nutrients · Herbivory

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Cite this article as: Martinetto P, Teichberg M, Valiela I, Montemayor D, Iribarne O (2011) Top-down and bottom-up regulation in a high nutrient–high herbivory coastal ecosystem. Mar Ecol Prog Ser 432:69-82.

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