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Marine Ecology Progress Series

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MEPS 390:117-128 (2009)  -  DOI:

Caulerpa prolifera stable isotope ratios reveal anthropogenic nutrients within a tidal lagoon

Edward P. Morris1,*, Gloria Peralta1, Javier Benavente2, Rosa Freitas4, Ana Maria Rodrigues4, Victor Quintino4, Oscar Alvarez3, Nerea Valcárcel-Pérez1, Juan José Vergara1, Ignacio Hernández 1, J. Lucas Pérez-Lloréns1

1Department of Biology, and 2Department of Geology, and 3Department of Physical Oceanography, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real (Cádiz), Spain
4CESAM & Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal

ABSTRACT: Mapping of the nutrient content and isotopic composition of the native, rooted, green macroalga Caulerpa prolifera and the seagrass Cymodocea nodosa was conducted in the summer of 2006 within the inner Bay of Cádiz , SW Spain. Isotope values of suspended solids from aquaculture (δ15N = 9 ± 0.88) and urban effluent (δ15N = 7 ± 1.97) were similar to the isotopic composition of the macrophytes (δ15N range 3.4 to 8.1), suggesting the influence of anthropogenic nutrient sources throughout much of the bay. The N content of tissues (C. prolifera 3.0 to 4.9%; C. nodosa 1.8 to 3.0%) was highly associated with their isotopic composition, indicating that nutrient supply strongly influenced plant stoichiometry. Distance from the source, i.e. variation in water column nutrient concentration, which was also highly correlated with median current velocities (0.03 to 0.18 m s–1) and to a lesser extent benthic light dose (1.8 to 10.7 mol quanta m–2 d–1), appeared to determine the mass transfer of N to the benthos. Significantly lower values of C. nodosa N content and δ15N hint at the role strong gradients in environmental conditions may play in promoting the stable coexistence of seagrasses and C. prolifera within the bay. C. prolifera was a useful indicator species that, via the analysis of its tissue composition, can provide a highly effective tool to aid in the management of nutrient inputs within shallow, coastal zones.

KEY WORDS: Macroalgae · Nitrogen · δ15N · δ13C · C:N ratio · Hydrodynamics · Seagrass ·Bay of Cádiz

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Cite this article as: Morris EP, Peralta G, Benavente J, Freitas R and others (2009) Caulerpa prolifera stable isotope ratios reveal anthropogenic nutrients within a tidal lagoon. Mar Ecol Prog Ser 390:117-128.

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