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Thls work presents the investigations made on the n e r~t~c suprabenthlc communities of the Portuguese margln (continental shelf and upper slope) exposed to seasonal upwelllng These communitles were sampled dunng the AVEIRO-94 crulse at 5 sites located along an E-W bathymetnc transect from 21 to 299 m depth using a suprabenthlc sled with s u p e~p o s e d nets In the 0 to 100 cm water layer the total denslties ranged from 700 2 to 13591 7 lnd lOOm During daytime the motile fauna was m a~n l y concentrated within the 0 to 50 cm water layer (76 2 to 97 2 % of the total abundance) The night-time sample at the shallower site showed a more even d~stnbution of the fauna in the nearbottom water layers (nocturnal migratory behaviour of some motile species) The Shannon diversity (H') values ranged from 1 8 4 to 3 54 for the shelf sites and increased at the upper slope site (4 15) Mysids and amphipods were generally dominant except for at the middle part of the shelf where the latter was replaced by euphausuds The suprabenth~c fauna off Aveiro was compared with slmilar data from the same bathymetnc samphng levels off Arcachon (Bay of Biscay) Multivanate analysis showed that differences in faunal composition between the 2 geographic areas were smaller than depth-related vanahons within geographic areas The results were discussed in relation to other suprabenth~c communities from the northeastern Atlantic

This work aims to define the factors driving the accumulation of metals in the sediment of the lagoon of Aveiro (Portugal). The role of initial diagenetic processes in controlling trace metal retention in surface sediment is traced by mineralogy, magnetic susceptibility and geochemical analyses. Although several studies have focused on the metal distribution in this polihaline and anthropized coastal lagoon, most of them have been solely focused on the total metal concentrations. This study instead represents the first attempt to evaluate in a vast area of the Aveiro Lagoon the role of biogeochemical processes in metal availability and distribution in three extracted phases: exchangeable cations adsorbed by clay and elements co-precipitated with carbonates (S1), organic matter (S2) and amorphous Mn hydroxides (S3). According to the sediment guideline values, the sediment is polluted by, for instance, As and Hg in the inner area of the Murtosa Channel, Pb in the Espinheiro Channel, Aveiro City canals and Aveiro Harbour, and Zn in the northern area of the Ovar Channel. These sites are located near the source areas of pollutants and have the highest total available concentrations in each extracted phase. The total available concentrations of all toxic metals are however associated, firstly, with the production of amorphous Mn hydroxides in most of the areas and, secondly, with adsorption by organic compounds. The interplay of the different processes implies that not all of the sites near pollution sources have polluted surface sediment. The accumulation of metals depends on not only the pollution source but also the changing in the redox state of the sediments that may cause alterations in the sediment retention or releasing of redox-sensitive metals. Results of this work suggest that the biogeochemical processes may play a significant role in the increase of the pollutants in the sediment of the Aveiro Lagoon.

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