, 2001). The C:N ratios give an estimative idea of the origin and quality of the particulate matter (Varela et al., 2004 and reference therein).

Values close to the Redfield ratio (6.7) imply flux of fresh autochthonous pelagic material, as it was observed, for instance, in the southwest Kattegat (Lund-Hansen et al., 2004) and in the Pontevedra Ría (Varela et al., 2004) during phytoplankton blooms, over trap deployments of 24 h. In our study, the C:N ratios in the settled material were on average 13.5, indicating a high proportion of decomposed material and high loads of allochthonous matter (e.g. benthic microalgae and/or decaying organic material of littoral origin) (Heiskanen and Leppänen, 1995, Olesen and Lundsgaard, 1995 and Tamelander and Heiskanen, 2004). The proportion of decomposed BIBF 1120 manufacturer material is in agreement with the high phaeopigments concentration measured in the collectors (higher pha:chl Ribociclib order ratios than in the water surface) and with the fact that the particulate matter had more time to be remineralized considering the relatively long-term deployments performed in this work. Similar findings (C:N ratio closed to 11) were achieved by Fernández et al. (1995) in the Cantabrian Sea. The presence of allochthonous material in the settled material

in the Bahía Blanca Estuary is in agreement with important inputs of detritus into the pelagic environment from the surrounding saltmarshes (Montemayor et al., 2011 and Negrin et al., 2013), antrophogenic inputs as well as with the shallow water column combined with high tidal and wind energies that promote resuspension of bottom

sediments (Guinder et al., 2009b and Marcovecchio et al., 2009). In temperate coastal systems, sedimentation of phytodetritus after the spring bloom contributes with a significant part of the total annual sedimentary input to the bottom (de Jonge and van Beusekom, 1995 and González et al., 2009). In the Bahía Blanca Estuary, the high chl levels and high density of diatoms observed inside the collectors suggest high production and accumulation Arachidonate 15-lipoxygenase of sinking phytoplankton during the winter bloom. The shallowness of the water column might allow an important number of viable cells to reach deeper layers and proliferate massively in relatively dark conditions. Moreover, the presence of viable benthic microalgae growing inside the collectors has revealed important contribution of microphytobenthos to pelagic primary production in the inner zone of the Bahía Blanca Estuary, as it has been observed in other shallow coastal environments (Cibic et al., 2007, Dale and Prego, 2002 and Underwood and Kromkamp, 1999). The preliminary approach presented here contributes to the understanding of the major processes shaping the vertical dynamics of particulate matter in the highly turbid and productive inner zone of the Bahía Blanca Estuary.