Experimental sediment disturbances on a tidal flat: Responses of free-living Platyhelminthes and small Polychaeta

Small-scale sediment disturbances on a sandy tidal flat in the North Sea changed the pattern of abundances in free-living platyhelminths (Turbellaria) and small Polychaeta, but not the species composition. Patches of 0.25 m² were made anoxic, were regularly raked at the surface, or the upper layer of sediment was inverted. Recolonization after temporary anoxia proceeded very slowly. Raking caused diatom-feeding platyhelminths and the polychaetes to emigrate. Turning the upper 5 cm of the sediment upside down was harmful to both taxa, but platyhelminths recolonized quickly. Background densities were temporarily surpassed, first by predators, then by diatom feeders. Coherent responses of trophic guilds in platyhelminths do not suggest that release from competition is involved but indicate that such disturbances alter the availability of food resources and the organisms immigrate accordingly.     

Surf zone fish community and species response to a wave energy gradient

Analysis of seine netting data for Algoa Bay, South Africa reveals that species richness and relative abundances of surf zone fishes differ at three beach sites, despite their close proximity. A gradient in species compositional and abundance response to spatially varying wave exposure is proposed as the principle cause. Implications are considered in the context of trophic interaction and impact of individuals and species assemblages upon energy and other resources of the habitat.     

Preparative scale enantioseparation of a chiral epoxide: Comparison of liquid chromatography and simulated moving bed adsorption technology

The feasibility of using simulated moving bed technology (SMB) for chiral separation on cellulose triacetate is demonstrated on the preparative scale: 1 kg of a chiral epoxide has been separated. On comparing SMB technology with conventional liquid chromatography it turns out that the main advantage of SMB lies in the significant reduction of mobile phase consumption. The process design for SMB is made theoretically and the predictions are confirmed by our pilot study. © 1993 Wiley-Liss, Inc.     

Resolving the differences in plant burial responses

Burial is one of the major factors influencing plant ecology in deserts and coastal areas. Consequently, many studies have measured the responses of dune plants to sand burial. However, there remains little agreement about the mechanisms and characteristics constituting the burial response of plants. In particular, stimulation of growth has been reported as the most common plant burial response; however, stimulation has not been reported consistently among studies. Here, a literature survey showed that the depth of burial relative to the height of the plant determined whether the growth of a species was stimulated by burial. Growth stimulation was limited to shallow burial depths, while burial depths greater than the height of the plant consistently resulted in reduced growth. As studies used widely differing burial depths or units of growth measurement, the variation in reported stimulation of plant growth can be partly attributed to differences in experimental procedure. The stimulation of growth in many species was accompanied by an increase in photosynthesis over a limited period and by a shift in biomass allocation from root to shoot. Most plants demonstrated stimulated growth (up to 200%) in response to shallow burial indicating that some burial response mechanisms are general to many species. However, a few specialist dune species displayed a much greater ability to respond to burial (up to 700% stimulation of plant mass). Although allocation shifts and increased photosynthesis have been shown to be associated with dune plant burial response, there remains a need for field measurements that focus on the diversity of mechanisms underlying plant response to burial.     

Transmission of visceral leishmaniasis in a previously non‐endemic region of Tunisia: Detection of Leishmania DNA in Phlebotomus perniciosus

Visceral leishmaniasis (VL) has been endemic in northern Tunisia and has occurred sporadically in the center of Tunisia. Recently, there have been several cases from areas known to be free of VL. We report in this work all human and canine cases of VL recorded between 2003 and 2011 and an entomological study of phlebotomine fauna in a previously non‐endemic region. Sixty‐three cases of VL were diagnosed and identified as L. infantum using several different methods. Eight species of 179 sand flies were caught and identified by both morphological and molecular methods. Two genera were present, Phlebotomus and Sergentomya, with an abundance of the subgenus Phlebotomus (Larrousius) spp., a classic vector of VL in Tunisia. Moreover, Leishmania DNA was detected in seven unfed Phlebotomus pernicousus and L. infantum was identified in three of them. This result confirms the establishment of a transmission cycle of VL in the studied region by the coexistence of infected vectors with infected hosts.