MEPS 324:95-104 (2006)  -  doi:10.3354/meps324095

Effects of sill processes on the distribution of epineustonic competent larvae in a stratified system of Southern Chile

Carlos Molinet1,6,7,*, Arnoldo Valle-Levinson2, Carlos A. Moreno3,7, Mario Cáceres4, Mónica Bello5, Manuel Castillo5

1Instituto de Acuicultura, Universidad Austral de Chile, Los Pinos s/n, Puerto Montt, Chile
2Department of Civil and Coastal Engineering, University of Florida, 365 Weil Hall, PO Box 116580, Gainesville, Florida 32611, USA
3Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla 567, Valdivia, Chile
4Universidad de Valparaiso, Facultad de Ciencias del Mar y Recursos Naturales, Av. Borgoño 16344, Viña del Mar, Chile
5Servicio Hidrográfico y Oceanográfico de la Armada de Chile, Errazuriz 232, Casilla 324, Valparaíso, Chile 6Centro Universitario de la Trapananda, Portales 73, Coyhaique, Chile
7Centro de Investigaciones en Ecosistemas Patagónicos, Bilbao 550, Coyhaique, Chile

ABSTRACT: The inlets of southern Chile are characterized by a well-defined pycnocline which, acting in concert with the biological characteristics of larvae, is believed to influence planktonic larval distribution. Here, we assessed the effects of stratified flow over a sill on the spatial abundance and distribution of epineustonic competent larvae of Concholepas concholepas. We used measurements of velocity profiles using an Acoustic Doppler Current Profiler (ADCP), intensive plankton collections combined with simultaneous conductivity, temperature and depth (CTD) profiles, monitoring of the pycnocline depth, and temperature records from moored thermistors. Evidence of Bernoulli aspiration and an intratidal transient front was observed over the sill from CTD data and an echo-sounder trace. ADCP measurements showed intensified recirculation in the residual flow over the sill. This oceanographic feature coincided with high abundances of epineustonic competent larvae of C. concholepas over the sill area. We found evidence indicating that physical mechanisms related to sill processes can influence epineustonic competent larval distribution in a stratified system. We also propose a conceptual model that brings together larval behaviour and stratified flow patterns to explain the rise of epineustonic larvae to the surface and larval aggregation over a sill.

KEY WORDS: Bernoulli aspiration · Sill · Epineustonic larvae · Stratified system · Southern Chile

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