ABSTRACT
Phytoplankton play a central role in marine ecosystems by yielding ca. 50% (~ 50 Gt C/year) of the global primary production (Longhurst et al. 1995, Field et al. 1998). By their central role at the base of the food web these communities shape biogeochemical cycles, carbon export from the euphotic zone to the deep ocean and energy fl uxes through food web networks (Finkel et al. 2010, van de Waal 2010). Whilst in coastal areas, microphytobenthos, macroalgae and halophytes also contribute in carbon fi xation (Kromkamp et al. 2006, Connell and Russell 2010), in the open ocean, phytoplankton constitute the only source of primary production to sustain pelagic food webs (Falkowsky and Oliver 2007, Chavez et al. 2011). In fact, phytoplankton blooms are an essential condition for fi sheries and for the benthic-pelagic coupling in coastal systems (Legendre 1990). These rising biomass events mainly occur in response to changes in light and nutrients driven by the seasonal cycles of radiation, temperature and water column stability; while the end phase has been ascribed to nutrient depletion and zooplankton grazing pressure (Sommer et al. 2012). Spring blooms are
1 Área de Oceanografía Química, Instituto Argentino de Oceanografi a (IADO-CONICET), Camino La Carrindanga km 7.5, CC 804 B8000FWB Bahía Blanca, Argentina.
