Breeze conditions as a favoring mechanism of Alexandrium taylori blooms at a Mediterranean beach

Abstract

A study of Santa Ponça Bay (Balearic Islands) was conducted during summer 2002 to understand further the processes controlling recurrent Alexandrium taylori blooms near the beach. These massive algal proliferations (106 cells L−1) have become common in many anthropized pocket beaches of the Mediterranean during the summer season. Nearshore dissolved inorganic nutrient concentrations (DIN) are generally high near the shoreline (avg. DIN at 1.6 μM), yet this factor alone is insufficient to explain harmful algal bloom (HAB) occurrences at some beaches and their absence in others. It is postulated that summer conditions, and particularly, the mild breeze conditions are key factors into understanding these nearshore blooms. The advantages of this coastal environment for a migrating dinoflagellate such as A. taylori are discussed. Resilience to undergo enhanced turbulence episodes, motility, day/night migration and a favorable current regime that produces shoreward transport at sea surface are regarded as concurrent mechanisms that lead to HAB generation and maintenance.