Despite being the most important source of pollen and spore input into most lakes and near-shore marine sediments, we know very little about fluvial (waterborne) pollen and spore transport. This paper presents the results of a dedicated monitoring programme conducted over 2 years and at a catchment scale in South West England. The land use of the nine sub-catchments monitored was determined using Landsat Thematic Data. At two stations, pollen and spore sampling through storm hydrographs was undertaken whilst at the other 7 sub-catchments only peak flow samples were collected. Samples were also collected from re-suspended bed material, riverbanks and at low flows. Airborne pollen flux was monitored using modified Tauber traps. The results support previous research illustrating how the vast majority of fluvial pollen and spores are transported during floods (in this case 91%) and that the main control on waterborne pollen and spore assemblages is the catchment vegetation. However, strong seasonal effects are shown as well as the importance of distinctive sources, such as the riparian input, bed re-suspension and overland flow into drains and tributaries. Fine sediment in river pools appears to act as a selective store of damaged cereal-type pollen grains in arable catchments and this can reduce the inherent underestimate of arable land from pollen diagrams with a high fluvial input and increase the visibility of early agriculture. In order to simulate the likely result of a flood-dominated influx to a small lake scenario, modelling was undertaken whereby different sub-catchments were substituted in order to represent changes in catchment vegetation under a constant hydrological regime. The results show the dampened response of land use groups to catchment land use change, and the frequent occurrence of anomalous single-level peaks due to seasonal flushes from specific near-stream vegetation types. Both these features are commonly seen in lake pollen diagrams. Fluvial pollen and spore loading is dependant upon discharge and so concentrations in laminated or varved sediments could be regarded as a proxy for flood magnitude. The implications for this study on the interpretation of lake and near-shore marine pollen and spore diagrams are discussed and it is argued that a more quantitative approach to waterborne pollen could improve the estimation of land use from lakes in the temperate zone.

Despite it being a component of the seston we know very little about fluvial (waterborne) pollen and spore (palynomorph) transport. This paper presents the results of a monitoring programme conducted over two years and at a catchment scale in South West England. A hierarchical monitoring network was established with flood peak samples taken at 9 sub-catchments, intra-hydrograph samples taken in two sub-catchments and time-integrated sampling undertaken at one location. In addition sampling was undertaken of probable palynomorph sources such as channel bed and bank sediments, and the airborne pollen flux was monitored using modified Tauber traps. The results support previous research in illustrating how the vast majority of fluvial pollen and spores are transported during floods (91%) and that the main control on waterborne palynomorph assemblages is the catchment vegetation and its spatial distribution but with a long-distance (extra-catchment) component. However, strong seasonal effects are also shown, and the importance of distinctive sources such as the riparian input, bed re-suspension and overland flow into drains and tributaries is revealed. Fine sediment in river pools appears to act as a selective store of damaged cereal type pollen grains derived from arable fields. Although pollen does form part of composite particles the data presented here suggest that the majority of the pollen is transported as single grains. Fluvial palynomorph loading is strongly dependant upon discharge and so concentrations in laminated or varved sediments could be regarded as a proxy for flood magnitude.