Pollen record of the last 500 years from the Doninos coastal lagoon (NW Iberian Peninsula): Changes in the pollinic catchment size versus paleoecological interpretation

Pollen, diatom, charcoal and sedimentological analyses of a 4.20-m long cor e collected in the margin of the Doninos coastal lagoon, northwest Iberian Peninsula, provide information about the environmental evolution of this la goon during the last 530 yr BP. During this time period, local environmenta l changes, such as changes in the sand-barrier permeability, alluvial sedim entation and/or anthropogenic activity, played a major role in the evolutio n of this coastal system. This scenario allows us to test the degree the po llinic signal recorded in the sediments of coastal lagoons is reshaped by t he influence of local processes. Diatom and sedimentological data as well as historical archives indicate th e development of a lacustrine system at the bottom of the sequence. Therefo re, the coring site might be included in the lagoon itself. Pollen data see ms to reflect the regional vegetation as a consequence of the large pollini c catchment area. Local Castanea cultivation and anthropogenic deforestatio n are also recorded. At the top of the sequence, diatom facies suggest increased marine influenc e at this time as a consequence of the more common events of breaching of a retrograding barrier. This, plus natural silting up by alluvial sedimentat ion and man-induced drying up of the lagoonal margins, lead to a progressiv e decrease in the water body extension. The coring point is now outside of the lagoon, implying a reduction in the pollinic catchment area that gave r ise to a gradual increase in the local pollinic rainfall of periphytic vege tation. From the pollen diagram of this coastal deposit signatures of regional vege tation are swamped by local pollen input. The fluctuations in the percentag es of the different pollen taxa are related to the complex interaction betw een basin size, human activities and breaching of the barrier. Caution must therefore be taken with direct paleoclimatic inferences from pollinic stud ies in coastal lagoons as an alternative where other continental deposits a re lacking.