We explore the possibility of building a continuous glacier reconstruction by analyzing the integrated sedimentary response of a large (440 km2) glacierized catchment in western Norway, as recorded in the downstream lake Nerfloen (N61°56’, E6°52’). A multi-proxy numerical analysis demonstrates that it is possible to distinguish a glacier component in the ~ 8000-yr-long record, based on distinct changes in grain size, geochemistry, and magnetic composition. Principal Component Analysis (PCA) reveals a strong common signal in the 15 investigated sedimentary parameters, with the first principal component explaining 77% of the total variability. This signal is interpreted to reflect glacier activity in the upstream catchment, an interpretation that is independently tested through a mineral magnetic provenance analysis of catchment samples. Minimum glacier input is indicated between 6700–5700 cal yr BP, probably reflecting a situation when most glaciers in the catchment had melted away, whereas the highest glacier activity is observed around 600 and 200 cal yr BP. During the local Neoglacial interval (~ 4200 cal yr BP until present), five individual periods of significantly reduced glacier extent are identified at ~ 3400, 3000–2700, 2100–2000, 1700–1500, and ~ 900 cal yr BP.

A shallow marine Late Weichselian deposit on the outer coast of western Norway contains both terrestrial plant material and articulated marine shells. We have 14C dated both types of material from eight different stratigraphic levels covering the time interval 12,300 to 11,100 14C yr B.P. The difference between 14C-dated terrestrial plant material and marine shell material (the marine reservoir age) ranges from 200 to 525 yr, with a weighted average of 380 ± 32 yr. This is almost identical to the present reservoir age of 379 ± 20 yr for southern Norway. In the mid-Younger Dryas (YD) interval the reservoir age in the North Atlantic (55°N–65°N) was 700–800 yr, considerably greater than the present reservoir age and the age we have measured for the Bølling–Allerød interval. The reason for this increase during the YD is probably a combination of reduced inflow of surface waters to the North Atlantic and more extensive sea-ice cover. Evidence from marine cores show that the southeastern Norwegian Sea experienced rapid fluctuations in the inflow of warm Atlantic surface water during the period 12,300 to 11,000 yr B.P. However, the reservoir age apparently did not increase during these colder periods (Older Dryas I and II). The reason is probably that, in contrast to the YD, these colder periods did not last long enough and/or were of too limited extent to alter the reservoir age of the ocean. A comparison of the obtained 14C dates with the varve 14C chronology from Lake Suigetsu indicates an age of 12,770 cal yr B.P. for the AL/YD boundary.

Sexual maturation and spawning was followed in one and two year old rope cultured mussels (Mytilus edulis) from April to December. Development of gonad and storage tissue was followed using descriptive categories from histology, and development of total soft tissue was followed using meat yield and condition index.

Both age groups were mature both during spring and autumn and had similar patterns of spawning and maturation. April and May were characterized by scattered spawning activity and accumulation of storage reserves at the same time, resulting in relative constant condition indices during this period. This was followed by ripening of the gonads and an increase in condition index that culminated in a spawning in late June. Parts of the population then entered a resting phase, while a part of the population underwent new maturation towards an autumn spawning in September. In December all the mussels had started the winter maturation.

Condition index and meat yield were higher throughout the season in the one year old mussels. This was probably due to the sum of several factors, including differences in specific feeding rates and biomass density, rather than spawning.

The present study is the first to compare the reproductive patterns over time of one and two year old mussels with reliable age determination, and provide information that there are no obvious differences in neither timing of gonad development nor spawning patterns between the age-classes.