Importància biogeoquímica del pol·len i les espores en un sistema litoral

Abstract

Aerosols impact the dynamics of marine ecosystems. So far, the main focus has been on inorganic nutrients and metals from mineral sources. However, the role of organicmatter is becoming increasingly important, especially since heterotrophic bacteria seem to show important responses to aerosols. Biogenic components of aerosols have not been given the attention as players impacting the marine ecosystem. We have collected pollen and spores with a Hirst sampler for 2.5 years (May 2013-December 2015) at a coastal site in Blanes (NW Mediterranean, 41°40'59.8>N 2°48'01.0>E). The concentrations in airof pollen and sporeswere estimated daily from microscope counts. Pollen counts were done at the lowest taxonomic level possible for all days. Spores were counted to the lowest taxonomic level only on 33% of the days. For the remainder only Alternaria and Cladosporium were counted and estimates for total spores were calculated using regressions with data from relatively nearby locations and similar vegetation. The most abundant pollen species, comprising 95% or more of the grains for any given season, were identified. Sizes, volumes and carbon (C), nitrogen (N) and phosphorus (P) content were obtained from literature data. Wind intensity and direction were obtained hourly from a nearby weather station and from the NOAA HYSPLIT model (500 and 1000 m a.s.l.) in forward mode. The pollen and spores in the air were assigned to move towards the sea for any given day when the wind was blowing in that direction for 12 h or more. Days favorable for movementtowards the sea were accounted for 60% overall, with spring months being the most favorable. We then estimated monthly deposition over the sea and the relative biogeochemical contribution given climatic element concentrations in water. Annual mass flux to the coastal ocean is relatively small(985,7 mgm-2).However, deposition is largest in spring and summer, when nutrient conditions in the water are most oligotrophic and thus may help fuel marine production, especially heterotrophic bacteria, which show higher activities when grown with pollen in laboratory assays