Exotic pollen in sediments from the high Arctic lake Tenndammen, Svalbard archipelago: Aspects of potential pollen sources and transportation ways

The problem of extra-regional long-distance pollen component (LDC) has been known since the first attempts of pollen analysis performed in the early 1920s. In addition, the interpretation of pollen analyses of Arctic sediments is complicated by the typically low concentrations of pollen and spores. Furthermore, local/regional pollen production is low in the Arctic that greatly increases the role of LDC.

In this study, we analysed for pollen and spores lacustrine sediments from Svalbard, Colesdalen valley, lake Tenndammen (N 78°06.118; E 15°02.024) as well as ten soil samples collected from the lake’s shores at ca 2-4 m from the water body. Based on pollen origin, we distinguished three groups: (1) regional pollen, which includes pollen and spores of the plants that are known from local flora of the Colesdalen valley or from Svalbard in whole, (2) exotic pollen, which comprises pollen of plants that are not growing in Svalbard, (3) pollen of mixed or unclear origin, which includes several types; where it is difficult to decide on their actual origin, types which can originate from Svalbard but also typical of the  LDC of other Arctic regions as these plants produce massive amount of pollen that travel with winds and marine currents. In total, 56 pollen taxa were identified from the sediments, whilst 35 pollen types were found in the soil samples. Major changes in pollen assemblages after ca 1900 CE were associated with human impact and three pathways of exotic pollen transport were inferred: long distance wind transportation, transport by bird and by human immigration.

Around 1920 CE, the first introduced plant taxa were identified, i.e., presence of Apiaceae and Fabaceae pollen. Large grains with a thick exines and an annulus diameter of 10.6-13 μm, identified as Poaceae/Cerealia type, were continuously present since ca 1920 CE. Moreover, since ca 1200 CE the contribution of regional pollen, long distance extra-regional pollen, and pollen with mixed and unclear origin in Colesdalen has been relatively stable around 1%, 29%, and 70% respectively. These proportions are also supported by our analyse of the previous palynological studies in Svalbard from 46 publications. Other exotic pollen, including Ulmus, Juglans, and the even more unexpected tropical pollen types of Albizia/Mimosa, Eucalyptus, Acalupha, and Passiflora are exclusively found in the sediments dating to the 1930s-1960s. This is the period associated with the most intensive mining activity and human traffic to and from Colesdalen, including a well-tracked transmigration to the sub-tropical regions and resorts of the former USSR. Additionally, the occurrence of Myrica (gale) type, and Erica type in the sediments throughout the ca 700 yr study period and registered in the soil samples are discussed in terms of geese seasonal migration to and from Scotland (UK), Belgium and the Netherlands. The pollen of Apiaceae, Fabaceae, Saxifragaceae, Campanula, Rosaceae, Papaver, Polemonium type, most likely originate from the regional vegetation. This research provides the first comprehensive examination of the LDC problem in Svalbard palynology, and demonstrates how the history of human occupation and transmigration can be directly reflected in lake sediments.