Phytoplankton colonization patterns and the abundance of suitable aquatic ecosystems: the importance of nestedness among freshwaters. 17th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP). Kastoria, Greece, 14-21 September 2014. Book of Abstracts: 34

Species-poor and species-rich phytoplankton assemblages in two Sicilian water bodies (Lake Pergusa and Lake Biviere di Gela) were compared to test the hypothesis that the number of colonization events and the successful establishment of a new species in an aquatic ecosystem may depend on the number and nestedness of water bodies in a given area. The two ecosystems are both natural, shallow lakes and they are protected sites hosting a rich avifauna. Both the lakes had quite high conductivity values (> 2,500 μS cm-1) and both were re-filled with fresh waters (< 400 μS cm-1) after they had disappeared because of the over-exploitation of their main inflows to fulfill agriculture water-demand. However, the Lake Biviere di Gela is located in an area with a high density of temporary ponds, whereas Lake Pergusa is an isolated water body without other aquatic ecosystems being present in its surroundings. Both the water bodies have been sampled for phytoplankton since their re-filling occurred in 2002 (Lake Pergusa) and in 2005 (Lake Biviere di Gela). The results show that Lake Pergusa has a quite species-poor phytoplankton assemblage with periods characterized by the virtual absence of species, whereas Lake Biviere di Gela show a very rich phytoplankton and a quite high rate of floral change from year to year. The composition of phytoplankton samples collected in the nearby temporary ponds suggests that Lake Biviere of Gela and the temporary pond system in its surrounding form a single reservoir of biodiversity which favored the quick re-establishment of a highly diversified phytoplankton in the lake. Conversely, the isolated Lake Pergusa, although its re-filling occurred three years earlier than Lake Biviere di Gela, still shows a very species-poor phytoplankton assemblage and very little inter-annual changes in its composition

The potential of the zooplankton resting-stage bank to restore communities in permanent and temporary waterbodies

We assessed how the viability and diversity of the zooplankton resting-stage bank can be affected by predictable and unpredictable hydroperiods using permanent and temporary lakes. We hypothesized that the zooplankton resting-stage bank in temporary waterbodies would be affected by the length of the dry period (seasonal, intermittent and episodic). We also tested the role of dried macrophyte mats in preserving resting-stage banks in temporary lakes. Laboratory experiments were conducted with sediment samples from two permanent waterbodies and three temporary shallow lakes that undergo dry periods of different lengths (seasonal, intermittent and >10 years dry). The results of the experiments suggested that the dry period length significantly affected the viability and diversity of the resting-stage bank, affecting its potential role in zooplankton community recovery. Longer dry periods also affected the temporal hatching response of resting stages from temporary lakes: species from unpredictably drying waterbodies experienced delayed hatching. Resting-stage viability and richness were largely and positively influenced by dried macrophyte mats, which surpassed the efficiency of the sediment as a substrate for conserving resting stages. Our results provide new insight on the functional role of macrophytes indicating that these beds are pivotal in conserving resting stages and increasing zooplankton community resilience

Potential distribution of the invasive freshwater dinoflagellate Ceratium furcoides (Levander) Langhans (Dinophyta) in South America

Dinoflagellates of the genus Ceratium are predominantly found in marine environments, with a few species in inland waters. Over the last decades, the freshwater species Ceratium hirundinella and Ceratium furcoides have colonized and invaded several South American basins. The purpose of this study was to create a distribution model for the invasive dinoflagellate Ceratium furcoides in South America in order to further investigate the basins at potential risk, as well as the environmental conditions that influence its expansion. This species is known to develop blooms due to its mobility, resistance to sedimentation, and optimized use of resources. Although nontoxic, blooms of the species cause many problems to both the natural ecosystems and water users. Potential distribution was predicted by using a maximum entropy algorithm (MaxEnt). Model was run with 101 occurrences obtained from the scientific literature, and climatic, hydrological and topographic variables. The developed model had a very good performance for the study area. The most susceptible areas identified were mainly concentrated in the basins between southeastern Brazil and northeastern Argentina. Besides already affected regions, new potentially suitable areas were identified in temperate regions of South America. The information generated here will be useful for authorities responsible for water and watershed management to monitor the spread of this species and address problems related to its establishment in new environments.Fil: Meichtry de Zaburlín, Norma. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Biología; ArgentinaFil: Vogler, Roberto Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Biología; ArgentinaFil: Molina, María José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Biología; ArgentinaFil: Llano, Víctor Martín. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Departamento de Biología; Argentin