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Nutrient content in tissues of Groenlandia densa, Myriophyllum spicatum and Zannichellia palustris : an attempt to understand the intercompartmental relationships in a small stream in the Middle Atlas Mountains of Morocco

Nouri Ayoub, Bihaoui Abdesslam, Hammada Soumaya, Chillasse Lahcen

Oceanological and Hydrobiological Studies

2024

Vol. 53, No. 4

355--364

Research has long focused on the relative importance of leaves and roots as sources of nutrient supply for macrophytes, as well as the function each stream compartment plays in their growth and development. This study aims to expand the debate on aquatic ecology and to better understand the connection between compartments in aquatic systems by highlighting the relationship observed in rivers between nutrients in macrophytes tissues, water, and sediments. We measured the concentrations of P-PO4, N-NO3 and N-NH4 in three different compartments of the Amengous stream in the Middle Atlas of Morocco. Myriophyllum spicatum (L.), Groenlandia densa (L.) Fourr. and Zannichellia palustris (L.) were selected as plant species. Our results show that even if the species coexist in the same habitat, they respond differently to nutrient richness. G. densa has a higher nutrient accumulation capacity than M. spicatum and Z. palustris and prefers the water compartment as a nutrient source. Although M. spicatum can accumulate phosphate compounds from water and sediment, ammonium is not its preferred nitrogen source. Z. palustris shows a tendency to accumulate nitrogen compounds through the roots, while it prefers the assimilation of phosphorus compounds through the leaves rather than the roots.

Adaptations of pupae of Chironomidae (Insecta: Diptera) to oxygen-poor habitats

Marziali Laura, Lencioni Valeria, Rossaro Bruno

Polish Journal of Ecology

2006

Vol. 54, nr 4

687-693

Morphological, behavioural and physiological adaptations of chironomids pupae to oxygen-poor habitats, such as the profundal zone of lakes, are discussed. Lentic and oxyregulator species possess developed respiratory organs (thoracic horns) and an extensive anal fringe to perform respiratory movements, whereas in rheophilic and oxy-conformer species these structures are reduced or absent. This led to the hypothesis that the number of thoracic horn branches, the number of anal macrosetae and the body size could consititute a measure of a species' oxygen requirements. These characters were analyzed in 12 species groups collected in 39 Italian lakes. Numbers were correlated to the optimum value of oxygen level, total phosphorus concentration and transparency calculated for each taxon. Taxa with plumose thoracic horns, extensive anal fringe and large body size (Chironomus) inhabited habitats poorer in oxygen than those inhabited by taxa with less extensive respiratory surface and fringe and small body size (Paratendipes, Polypedilum, Microtendipes). Stictochironomus was less tolerant than expected. Further studies are needed into the physiological adaptations of chironomid pupae.