Preservation differences can be used as correction factors to recalculate the relative abundances of each of the five dominant plankton taxa in BAIK38 and are depicted in Fig. 4. The resulting profile shows that Synedra acus is now the dominant taxa in zone 1 of the core, with other taxa being present at abundances generally less than 10%. At the zone 1/2 boundary, S. acus declines and is replaced by Cyclotella minuta and, to a lesser extent, Aulacoseira skvortzowii and Aulacoseira baicalensis. This profile is different from the relative abundance profile in Fig. 3, as S. acus values decline to very low values by c. 1400 AD, and C. minuta increases to peak values between c. 1525 and 1650 AD. Furthermore, the profile indicates that A. baicalensis remains common throughout this zone. Towards the zone 2/3 boundary, taxa more characteristic of warmer waters increase earlier than previously suggested at c. 1750 AD.
Dissolution was high throughout the profile—in most cases, only 10–20% of the valves considered as pristine (Fig. 4). High relative percentages of A. baicalensis and of benthic Fragilaria (sensu lato) were positively correlated (r=0.29 and r=0.26, respectively) to samples with large proportions of pristine valves. There were no significant relationships between this index of dissolution and any of the other dominant taxa. Fragmentation of the valves was also high. On average only 45% of the total count was represented by whole valves (Fig. 4) and high percentages of non-fragmented valves were positively correlated with the percentages of pristine valves. The percentages of pristine valves showed high variation (20–70%) and by contrast with the dissolution index, they were significantly correlated with the variations in percentages of many dominant taxa.
All diatoms in the analysed section were extensively affected by dissolution with only c. 1% of valves in a “pristine” condition. Diatom concentrations were generally extremely low throughout MIS 3 and across the MIS 3/2 transition with samples containing a mixture of extant and extinct species (Fig. 4).
The diatom succession at Academician Ridge is similar to the one from Continent Ridge and the two records, despite having very different sampling resolution, can be easily compared on the basis of their main floristic changes (Fig. 6). BVAR at Academician Ridge is about half that of Continent Ridge. There are also marked differences in the relative abundance of some taxa. At Academician Ridge, S. grandis and A. baicalensis are more abundant and S. formosus and C. sp. cf. operculata are less abundant than at Continent Ridge. The large peak in vegetative cells of A. skvortzowii found at Continent Ridge (DAZ 2) is absent at Academician Ridge, and is the most striking difference between the two records.