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1

Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea

Suursaar Ű., Torn K., Martin G., Herkül K., Kullas T.

Oceanologia

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2014

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No. 56 (4)

673--695

EN

The aim of the study was to investigate hydrodynamic effects on the formation of beach wrack at three locations in the northern Baltic Sea and to quantify the differences between the composition of species found in the beach wrack and in the neighbouring sea. Hydrodynamic measurements and modelling indicated that the beach wrack was mostly of local origin and that it was formed during high sea level and wave events. Comparison of the methods of beach wrack sampling and seabed sampling (diver, underwater video) demonstrated that beach wrack sampling can be considered an alternative tool for describing the species composition of macrovegetation in near-coastal sea areas. Although the hydrodynamic variability is greater in autumn and more biological material is cast ashore, the similarity between the two sampling methods was higher in spring and summer.

2

Rough Approximations in Varieties of Regular Languages

Martin G., Steinby M.

Fundamenta Informaticae

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2011

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Vol. 112, nr 4

281-303

EN

We study approximations of regular languages bymembers of a given variety L of regular languages. These are upper or lower approximations in the sense of Pawlak’s rough set theory with respect to congruences belonging to the variety of congruences corresponding to L. In particular, we consider the closest upper and lower approximations in L. In so-called principal varieties these always exist, and we present algorithms for finding them, but for other varieties the situation is more complex. Although we consider just Eilenberg’s +-varieties, the general ideas apply also to other types of varieties of languages. Our work may also be viewed as an approach to the characterizable inference problem in which a language of a certain kind is to be inferred from a given sample.

3

Density dependent growth of the red algae Furcellaria lumbricalis and Coccotylus truncatus in the West Estonian Archipelago Sea, northern Baltic Sea

Kotta J., Paalme T., Kersen P., Martin G., Herkül K., Möller T.

Oceanologia

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2008

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No. 50 (4)

577-585

EN

In an in situ experiment we evaluated the growth of the red algae Furcellaria lumbricalis and Coccotylus truncatus in the Archipelago Sea. The results showed that the growth rates of both species were similar but that growth decreased with increasing algal coverage. The effects were more pronounced for C. truncatus than for F. lumbricalis. Economic analyses aiming to establish sustainable harvesting limits for F. lumbricalis in the study area should take account of the density dependent growth of these red algae.