Circulación inducida por el sifón térmico y salino y su influencia sobre la dinámica de las proliferciones de algas nocivas en el Mediterráneo

Harmful algal blooms (HABs) constitute a current scientific problem, in which physical-biological interactions play a fundamental role. Due to its influence on the sun and beach tourism sector, beach proliferations are also a major socioeconomic problem in a community such as the Balearic and other Mediterranean climate zones. SifoMED is a multidisciplinary project that seeks to explain the dynamics of massive proliferations of dinoflagellates occurring in shallow, semi-enclosed and protected areas of the Mediterranean coast. In these areas HABs are developed in very coastal areas and conditions of stability of the water column. There is evidence of the generation of circulation patterns produced by the heating differences in shallow, semi-enclosed and with a bathymetric gradient. Although this mechanism, called 'thermal siphon', could be dominant in the dynamics of these zones, its implications in the development and maintenance of PANs are unknown. In an innovative way, we also suggest that the diffusive contributions of groundwater that have been documented in many coastal areas of the Mediterranean can also produce circulation patterns in these areas. We call saline siphon to this effect, since it shares physical bases similar to those of the thermal siphon. Our starting hypothesis is that, in the absence of more intense processes, the convective circulation produced by the thermal and saline siphon, and its competition with other forcings, such as wind, could be determinant for the dynamics of the phytoplankton proliferations occurring in the shallow and semi-enclosed waters, since it modulates the renewal of coastal waters and, therefore, modifies the relationships between cell growth and advection losses. The importance of this process in the horizontal retention and transport mechanisms of phytoplankton has been obviated to date. SifoMED will analyze the characteristics of the thermal and saline siphon from the experimentation in laboratory tanks and simple models of transport of particles and solutes. This theoretical approach allows to isolate the process from other more complex interactions that occur on the coast. In addition, SifoMED will study the feedback processes that can arise between the thermal siphon and the changes in the absorption of irradiation produced by the vertical migrations of the dinoflagellates, as well as the coupling between the vertical migrations and the variations of the turbulence produced during the diurnal stratification of the water column. During the project, a series of observation campaigns will be carried out to calibrate, verify and evaluate the relative importance of this process in the modulation of coastal flowering. The importance of the thermal and saline siphon could have implications in other aspects of the littoral ecosystem, such as the transport of pollutants or the patterns of self-recruitment and settlement of the larval phases of organisms such as invertebrates and fish larvae. The inclusion of this process in coastal circulation models could improve its predictive capacity of coastal dynamics.