Abstract Benthic cyanobacterial assemblages from ponds distributed along inland-coastal gradients in the McMurdo Sound region were studied during the 2011/12 Antarctic summer season. Twenty-five ponds were sampled in four distinct geographic locations, including the Lower and Upper Wright Valleys, Ross Island and the McMurdo Ice Shelf. For morphological identification, benthic mat samples were thawed and a subsample was directly observed by light microscopy. Remaining sample material was stored in 50 ml sterile polycarbonate bottles containing the mineral nutrient medium MLA for future studies, maintained at a temperature of 21°C. Ten morphological criteria were used to describe the morphotypes (trichome shape, number of trichomes in sheath, presence or absence of terminal attenuation of trichome, calyptra on mature apical cell, shape of apical cell, presence or absence of constrictions at transverse walls, granules, branching, range in width of trichomes and range of cell length) with reference to available identification literature. All morphospecies were documented using photomicrography. In total, 29 morphospecies were described, four assigned to the order Chroococcales, three to Nostocales and 22 to Oscillatoriales. The four geographic locations had similar taxonomic richness, sharing many morphospecies. However, each also contained distinct floristic elements that were rare or absent from the others.

Resumo A fitorremediação que consiste na utilização de plantas para remoção de íons, tem aumentado nas últimas décadas, tendo em vista a busca por tecnologias de baixo custo para mitigar áreas contaminadas. O objetivo do presente trabalho foi avaliar o potencial das macrófitas aquáticas: Azolla caroliniana Willd, Salvinia minima Baker (Salviniaceae) e Spirodela polyrhiza (L.) Schleiden (Araceae) em acumular manganês (Mn), um elemento que em concentração elevada pode ser tóxico para população humana. As três espécies acumularam Mn em seus tecidos e a absorção foi dependente da concentração do metal em solução. Spirodela polyrhiza acumulou as concentrações mais elevadas de Mn (17,062 mg g-1 MS), seguida por S. minima (4,283 mg g-1 MS) e A. caroliniana (1,341 mg g-1 MS). O excesso de Mn causou redução do conteúdo de clorofila total nas três espécies. O conteúdo de carotenóides diminuiu em A. caroliniana (27,02 %) e S. polyrhiza (25,34 %). Apenas em S. polyrhiza o crescimento foi reduzido significativamente (21,34%). As espécies A. caroliniana e S. minima toleraram excessos de Mn, mas foram ineficientes no acúmulo de concentrações elevadas do metal. O elevado conteúdo de Mn acumulado nos tecidos de S. polyrhiza sugere que a espécie possui capacidade para acumular este elemento. Portanto, apresenta potencial para ser utilizada na fitorremediação e oferece um novo recurso para explorar os mecanismos de acúmulo do Mn.

Abstract The phytoremediation technique, which consists of using plants to remove ions, has been increasingly chosen over past decades due to its low-cost technology to mitigate contaminated areas. The aim of this study was to evaluate the potential of the aquatic macrophytes, Azolla caroliniana Willd, Salvinia minima Baker and Spirodela polyrhiza (L.) Schleiden, to accumulate manganese (Mn), an element which, at high concentrations, may be toxic to human populations. The three species accumulated Mn in their tissues and the absorption was independent of the metal concentration in the solution. Spirodela polyrhiza accumulated Mn at higher concentrations of the ion (17.062 mg g-1 MS), followed by S. minima (4.283 mg g-1 MS) and A. caroliniana (1.341 mg g-1 MS). Manganese excess reduced total chlorophyll content in all three species. Carotenoid content was reduced in A. caroliniana (27.02 %) and S. polyrhiza (25.34 %). Growth was only significantly reduced (21.34%) in S. polyrhiza. The species A. caroliniana and S. minima were able to tolerate excess Mn, but were inefficient regarding the accumulation of high concentrations of the metal. High accumulated Mn content in the tissues of S. polyrhiza suggests that the species is able to accumulate this element. Therefore, it has potential for use in phytoremediation and provides a new resource for exploring the Mn accumulation mechanism.