Deep layer cyanoprokaryota maxima in temperate and tropical lakes

Padisák, Judit and Barbosa, F. A. R. and Koschel, R. and Krienitz, L. (2003) Deep layer cyanoprokaryota maxima in temperate and tropical lakes. ARCHIV FÜR HYDROBIOLOGIE BEIHEFT ADVANCES IN LIMNOLOGY, 58. pp. 175-199. ISSN 0071-1128

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Abstract

Deep layer cyanoprokaryota (Cyanobium, Planktothrix rubescens, Cilindrospermopsis raciborskii, mixed assemblage) maxima were observed in Lake Stechlin (Mecklenburger Lake District, Germany) and in Lake Dom Helvecio and Lake Carioca (Rio Doce Lake District, Brazil). All three of these lakes have trophic states between oligotrophic and mesotrophic and the euphotic depth exceeds the mixing depth in each case. In terms of density gradient stratification, tropical and temperate lakes are in a similar range and the position of the deep chlorophyll maximum (DCM) in upper hypolimnion. At the level of DCM light intensities of about 1% of subsurface irradiation are characteristic and can suffice the light demand of shade adapted species. Availability of phosphate-P was higher int he hypolimnia of the investigated lakes, therefore this can be a selective advantage for DCM populations. Although upper hypolimnia are rather stable habitats that, in theory, would allow the best adapted species to exclude all others, cyanoprokaryotic DCM can be bi- or multispecific. In multispecific DCM, weather-driven irregularities in the stability of the pycnocline might maintain a multispecific DCM assemblage. Co-dominance of Cyanobium and Planktothrix in Lake Stechlin probably exhibited a stable co-existence when one of the species was limited by light and the other by the availability of P. Occurence of DCM by buoyant cyanoprokaryota is probably much more common in lakes of moderate (from ultra-oligortophy to moderate mesotrophy) trophic state independent of latitudinal differences and they may play a key role in matter and energy cycling of freshwater.

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