Rates of Holocene isostatic uplift and relative sea‐level lowering of the Baltic in SW Finland based on studies of isolation contacts

Abstract

Southwestern Finland was covered by the Weichselian ice sheet and experienced rapid glacio‐isostati c rebound after early Holocene deglaciation. The present mean overall apparent uplift rate is of the order of 4–5 mm/yr, but immediately after deglaciation the rate of crustal rebound was several times higher. Concurrently with land uplift, relative sea level in the Baltic basin during the past more than 8000 years was also strongly affected by the eustatic changes in sea level. There is ample evidence from earlier studies that during the early Litorina Sea stage on the southeastern coast of Finland around 7000 yr BP (7800 cal. yr BP), the rise in sea level exceeded the rate of land uplift, resulting in a short‐lived transgression. Because of a higher rate of uplift, the transgression was even more short‐lived or of negligible magnitude in the southwestern part of coastal Finland, but even in this latter case a slowing down in the rate of regression can still be detected. We used evidence from isolation basins to obtain a set of 71 14C dates, and over 30 new sea‐level index points. The age‐elevation data, obtained from lakes in two different areas and located between c. 64 m and 1.5 m above present sea level, display a high degree of internal consistency. This suggests that the dates are reliable, even though most of them were based on bulk sediment samples. The two relative sea‐level curves confirm the established model of relatively gradually decreasing rates of relative sea‐level lowering since c. 6100 yr BP (7000 cal. yr BP) and clearly indicate that the more northerly of the two study areas experienced the higher rate of glacio‐isostati c recovery. In the southerly study area, changes in diatom assemblages and lithostratigraphy suggest that during the early Litorina Sea stage (8300–7600 cal. yr BP) eustatic sea‐level rise exceeded land uplift for hundreds of years. Evidence for this transgressio n was discovered in a lake with a basin threshold at an elevation of 41 m above sea level, which is markedly higher than any previously known site with evidence for the Litorina transgression in Finland. We also discuss evidence for subsequent short‐term fluctuations superimposed on the main trends of relative sea‐level changes.

Spectral tuning by selective chromophore uptake in rods and cones of eight populations of nine-spined stickleback (Pungitius pungitius)

“…Three of the habitats (HEL, BOL and WHI) were brackish or saltwater environments, whereas five were freshwater ponds (RYT, PYO, ABB and MAS) or lakes (ISO). Most of these populations have been reproductively isolated for the past 8000years or so (Eronen et al, 2001), except for MAS, which has been separated from WHI for less than a century. On the basis of microsatellite data, the MAS population is indistinguishable from WHI, whereas those of all other ponds and lakes are very different from any other population (Shikano et al, 2010).…”

“…The differences invite a simple generalization based on habitat type. Group 1 consists of populations from freshwater habitats cut off from the sea thousands of years ago (Donner, 1995;Eronen et al, 2001). Group 2 consists of salt-or brackish-water populations plus a population from Mashinnoye pond, which has been separated from the sea for a few decades only (see Materials and methods).…”

“…The Baltic and Fennoscandian region provides a 'natural laboratory' for the study of visual evolution in aquatic animals, offering multiple populations of several species that have become isolated in water bodies with different spectral properties following the retreat of Pleistocene ice sheets during the past ~9000years (Donner, 1995;Eronen et al, 2001). Here, we have studied to what extent and by what mechanisms the visual pigments of nine-spined sticklebacks (Pungitius pungitius) have diverged spectrally in five freshwater and three marine populations.…”

Late-glacial and Holocene palaeoenvironments in the Baltic Sea based on a sedimentary record from the Gda´n%%KERN_ERR%%sk Basin

“…The end of the Littorina Sea period was characterised by a significant decrease in water salinity caused by reduced marine water inflow due to isostatic uplift in the area of the Danish straits (Blazhchishin 1998, Eronen et al 2001, Gelumbauskaite & Šeckus 2005. A significant salinity decrease was identified in core 303700-7 above 217 cm with a minimum of 12 ‰ at 177 to 178 cm (ca.…”

Increasing the illumination slowly over several weeks protects against light damage in the eyes of the crustacean Mysis relicta

“…The two populations were separated as the ice shield receded at the end of the latest glaciation (ca. 9000 years ago; Eronen et al, 2001). Their current habitats are a permanently dark and brown, deep freshwater lake and a long narrow bay of the Baltic Sea with variable, but generally brighter, greenish illumination.…”