Worldwide Distribution Patterns of the Planktonic Shelled Protists Radiolaria (Polycystina) and Foraminifera: Similarities and Contrasts

Paleontological Journal - Planktonic Foraminifera and Polycystina (Radiolaria) depict roughly similar—but not identical—worldwide distribution patterns. Discrepancies affect both cold-...     

Annual and non-annual fish assemblages respond differently to environmental and spatiotemporal variations of temporary wetlands from southern Brazil

• The fish community of temporary wetlands is highly dynamic due to the marked seasonal changes in hydrological and limnological conditions. In this study, we evaluated spatiotemporal variation in the fish community and the influence of environmental factors on this variation in temporary wetlands in southern Brazil.
• Two different life cycles—annual and non-annual fishes—were recorded among species. Variation in the fish community appeared to be associated with differences in the life history strategy of species. While species of annual fish were present throughout the hydroperiod, gradually decreasing in density over time, non-annual fish species had an opposite pattern, with higher densities in the final phase of the hydrological cycle.
• Variations in the composition and abundance of fish community in temporary wetlands were related to habitat and landscape attributes (area, number of microhabitats and isolation between temporary wetlands) and climate indicators of water availability (air temperature, average rainfall, and water level of the São Gonçalo channel), but not to water conditions (dissolved oxygen, pH, conductivity and water temperature).
• We concluded that the ichthyofauna of temporary wetlands are composed both of rare species, highly specialised for life within these ephemeral environments, and widespread generalist species that reach the wetlands opportunistically for short periods. Habitat and landscape attributes and changes in climate and hydrological variables over the hydroperiod are the factors that had the greatest influence on spatiotemporal variation of the fish community.
• Maintaining physical characteristics and the hydrological cycle of temporary wetlands is critical for the conservation of fish species inhabiting these vulnerable environments in southern Brazil. Habitat and landscape attributes and climate and hydrology fluctuations affect the annual and non-annual fishes inhabiting temporary wetlands differently.

     

Intraspecific variability in Antarctic tintinnids: the Cymatocylis affinis/convallaria species group

Analyses of the morphometry of 630 loricae belonging to thedescribed species Cymatocylis affinis and Cymatocylis convallariaretrieved from 21 samples collected in the Weddel Sea (6O–73?S)strongly suggest that both taxa, including the four formae intowhich C.affinis was originally divided, are members of a singlespecies. The only feature which varies significantly and consistentlyamong the samples surveyed is the total length of the lorica,lowest average lengths being positively correlated with lowestabsolute abundances of this tintinnid in the waters sampled.This relationship points to some unfavorable factor(s) whichaffects both tintinnid reproduction/ survival and growth; thedata analysed suggest that drops in the availability of foodmight be responsible for the size (and abundance) variationsobserved.     

The invasive freshwater bivalve Limnoperna fortunei in South America: multiannual changes in its predation and effects on associated benthic invertebrates

Hydrobiologia - The invasive golden mussel Limnoperna fortunei is known to strongly affect benthic communities in South American freshwaters, but the evolution of these effects after the early...     

Microzooplankton and tintinnid species-specific assemblage structures: patterns of distribution and year-to-year variations in the Weddell Sea (Antarctica)

Silicoflagellates, large heterotrophic dinoflagellates, radiolarians,tintinnids and micro-crustaceans were counted in 72 screened(15 µm) samples retrieved at 0–150 m from the WeddellSea in January 1989. Tintinnid species were identified and biomassestimates were carried out for all groups on the basis of measurementsof cell dimensions. Dinoflagellates dominated the micro-heterotrophiccommunity at all stations and depths (65% of overall microzooplanktoniccarbon in the 0–150 m interval), followed by the tintinnids(18%), microcrustaceans (16%) and radiolarians (1%). All groups,with the exception of silicoflagellates, peaked noticeably inthe vicinity of the southern end of the transect (76–77°S).Relationships between concentrations of chlorophyll a and microzooplanktonicbiomass were present, yet not altogether consistent, but bothphyto- and microzooplankton seemed to generally respond to regionalenhancements associated with the ice edge. Comparison with similarWeddell and Weddell-Scotia data retrieved in February-March1987 and November 1988-December 1989, respectively, are highlycoherent in terms of microplanktonic abundances, their geographicand vertical distribution patterns, and the specific make-upand distribution of tintinnid assemblages. Analyses of the oraldiameters of tintinnid morphotypes suggest that the latitudinaland vertical distribution of their five dominant taxa (whichaccount for >90% of all individuals) is structured so asto maximize resource partitioning.     

Traits and impacts of introduced species: a quantitative review of meta-analyses

Hydrobiologia - Despite significant growth in the information on introduced species (NIS), agreement on their comparative fitness and effects on native (NAT) communities is heterogeneous....