Data files of figures 1, 2 and 3

We investigated optimal conditions for characterization of bioactivity of lytic compound(s) excreted by Alexandrium tamarense based on a cell-bioassay system. Allelochemical response of the cryptophyte Rhodomonas salina indicated the presence oflytic compound(s) in a reliable and reproducible way and allows for quantification of this lytic effect. The parameters tested were the incubation time of putatively lytic extracts or fractions with the target organism R. salina, different techniques for cell harvest from A. tamarense cultures and the optimal harvest time. A three hour incubation time was found to be optimal to yield a rapid response while accurately estimating effective concentration (ECso) values. Harvest of A. tamarense cultures by filtration resulted in loss of lytic activity in most cases and centrifugation was most efficient in terms of recovery of lytic activity. Maximum yield of extracellular lytic activity of A. tamarense cultures was achieved in the stationary phase. Such optimized bioassay guided fractionation techniques are a valuable asset in the isolation and eventual stmctural elucidation of the unknown lytic substances.

Tab. 1+2: C14-dates cf the older and younger emergence periods

In the neighbourhood of Oobloyah Bay various phenomena ean be eneountered whieh point to a ularge-seale uplift of shorelines, i.e. to an emergence of 200 m. Delta terraces, deltaic fan terraces and glacio-marine sands are regarded by the author as being the most reliable evidence of this. The marine limit documented by glacio-marine sand is to be found at ~170 m a.s.l. Hints of ancient shorelines located at a higher level exist only in the shape of badly preserved raised beaches. They were classified as less reliable records of past sea-levels, due to the lack of marine fossils and/or drift wood, and furthermore because those forms had been strongly influenced by periglacial processes. Deltaic deposits are of more importance in this context. The glacio-marine deltaic sands of several terrace levels contain terrestrial plant remnants which delivered C14dates. Using these dates und the relative elevations of terraces the emergenee of the area investigated could be recorded. This occured in a series of phases (and steps) which were summarized into two periods: an early period of emergenee which took place from at least 25 300 years B.P. to later than 17 340 years B.P. and a later one from at least 12 870 years B.P. up to the present day. The emergence seems to represent a discontinuous but regular sequence of relative sea level movements without intermittent submergence. Since the deltaic fans of the early emergence period were accumulated by sediments through glacio-fluvial channels of an adjacent glacier body the appropriate location of this glacial stage for one of the glaciers delivering meltwater (Nukapingwa Glacier) could be reconstructed. This stage of the glacier appears to belong to a retreating phase of the Mid-Wisconsin (?). The later period of emergence resulted in six rather glacio-marine delta terrace generations at the mouths of the main rivers with glaciofluvial regimen debouching into the Oobloyah Bay. A connection of this emergence with the glacial history of the field area is discussed. If one may rely on the age determinations of land derived plant fossils and their application for the climatic history of the area investigated, it must be concluded that the Heidelberg Valley, to a large extent, was alreaely deglaciated 25 000 years ago. The existence of a "Cockburn"-Phase in the sense of a major readvanee in Late Wisconsin times appears to be doubtful, or has been developed rather weakly.