Sample 1: a comparison between semi-quantitative data and concentration data Sample 1 is the only sample that is completed This makes it possible to compare the

semi-quantitative data of this sample obtained broadly halfway the picking process with the concentration data from the completed sample (see fig. 6 and appendix 2).

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Sample 1 held a total of more than 4024 identifiable macro-botanical fossils. These fossils include complete specimens and fragments of for instance seeds, achenes, nutlets, sporangia, oospores, endocarps and wood fragments. The total number of taxa is 45.

3.3.1 Observed differences and possible explanations for them

A number of taxa is not present in the semi-quantitative data but is identified in the complete concentration data. Some other taxa were present in the semi-quantitative data but have been identified differently after completion of the picking.

The remains of Hippuris vulgaris (fruit), Myriophyllum spicatum (fruit), Nuphar lutea (seed), Hypericum sp. seed, Monocote (stem fragment), Musci sp. (capsule operculum),

Rumex sp. (nutlet) and Solanum dulcamara (seed) were identified halfway, but are not

present in the concentration data. This is most probably because these remains were put aside with the other indeterminate remains to be looked at after this research. A re- evaluation of all fossils after the completion of all six samples will likely re-identify some of these specimens, whereas other main remain indeterminate.

The seeds tentatively identified as Rubus fruticosus have been included in the Rubus sp. after completion. None of the seeds was complete so it was not possible to firmly identify them to species level.

The fossils of Potamogeton acutifolius have been re-identified as P. trichoides. The endocarps of these two species are very similar so attention is needed when identifying them. For the final identification, more time was taken than during the tentative identification halfway the picking process.

The achenes from Ranunculus subg. Ranunculus have been identified to species level and assigned to Ranunculus sardous. The achenes from Ranunculus sceleratus have been assigned to R. sardous too. So effectively, all achenes from species in the subgenus

Ranunculus have been identified as R. sardous.

The nutlet of Eleocharis sp. has been identified to the species E. palustris.

Seeds of Juncus sp. and caryopses of Poaceae were not identified halfway, but are present in substantial numbers (44 and 134 respectively) in the completed data. This is because the picking of the 250μm fraction, in which most of these remains were found, only started after the halfway identification. The occurrence of sclerotia of the fungus

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Cenococcum geophilum only in the complete data is also explained by the order of

picking.

The nutlets of Cyperus longus were first probably included in the group of Carex sp. triogenous nutlet, but were identified to species level by comparison to modern specimens from the reference collection.

Some endocarps of various Potamogeton species were not preserved well enough to be undoubtedly identified to species level. Therefore, it was decided to only identify them up to genus level resulting in the presence of Potamogeton sp..

During the second half of the picking, one seed of Verbena officinalis was encountered. This species had not been found earlier in the process.

The identification of some bigger wood fragments lead to the addition of cf. Salix sp. to the botanical assemblage.

The biggest difference between the semi-quantitative data and the concentration data of sample 1 is the total amount of fossils. Some examples: the number of megaspores from Azolla filiculoides increased from less than 10 to 33 and those from Salvinia natans went up from around 50 to 389. The number of Sagittaria sagittifolia embryos rose from 1 to 8 and the number of Cyperus fuscus seeds increased from 1 to 66. The amount of

Characeae sp. oospores and cf. Dryopteris sp. sporangia increased the most, each from

around 300 to more than 1000.

3.2.1 Information gain vs. time investment

There is a delicate balance between the information that can be gained by picking an entire sample, and the time that needs to be invested to complete a sample. The lab work on sample 1 (picking and identifying) took an estimated 250 hours. It took so long partially because the students working on it were not very experienced in working with macro-remains, but also because the sample turned out to be very rich.

The comparison between the semi-quantitative data and the concentration data of sample 1 has shown that by completing the sample information was gained in several ways: 1) “new” taxa were added, 2) some fossils were identified to a more precise taxonomic level, and 3) the total amount of remains increased markedly. Despite this, reconsidering the tentative identifications has resulted in some apparent “loss” of information, because several fossils were re-evaluated as being indeterminate or

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identified to genus instead of species level. The indeterminate specimens will be studied later, after which they can be included again in the concentration data.

The information gain of completing the sample compared to the data from halfway is substantial. The “newly added” taxa and better identified taxa provide a more detailed picture of the local vegetation. The concentration data can be used to make a

concentration diagram of the entire sampled sequence once the other five samples are completed as well. It is no problem that some fossils were dubbed indeterminate and left to be looked at again at a later point. Careful identification of hard-to-identify specimens will only benefit the interpretation of the dataset. So completing the sample was worth the effort. If time is short, it is advised to either take a smaller sample (100cc) or to make sure that equal parts of each size fraction are picked.

However, it is an illusion that fully completing a set of samples gives an exact

representation of the vegetation present at the site. For instance, during the sorting of the sieving residues in the 2018 field campaign, several seeds of Celtis cf. australis were identified that originated from unit UA3c (Mike Field pers. comm.). The presence of

Celtis sp. At MAR-1 was already known from previous phytolith analysis, but the seeds

made an identification up to species level possible (Field 2018 pers. comm.).