Seasonal patterns of protoplankton and calanoid copepods in the Firth of Forth : an investigation or Copepod grazing and the effect of diatoms upon reproductive processes

Seasonal variability in the zooplankton of the Firth of Forth, including mesozooplankton and microplankton, were investigated across a full annual cycle. Grazing rates and prey selectivity by the dominant calanoid copepods (Acartia discaudata, Acartia clausi, Centropages hamatus and Temora longicornis) were also examined. Investigations were conducted upon Acartia discaudata and field collected prey under simulated diatom bloom conditions, using the species Thalassiosira rotula, in order to test the hypothesis of diatom inhibition of calanoid copepod reproductive processes. There were fundamental differences between the spring and autumn blooms, typical of temperate estuaries. The spring bloom was composed of highly abundant, small cells amounting to less than half the biomass of larger, less numerous microplankton present in autumn. Copepods dominated the mesozooplankton undergoing seasonal shifts in species’ dominance primarily in response to physical factors. Results of grazing experiments indicate a disproportionate preference for motile prey compared to ubiquitous concentrations of diatoms. Copepods switch to blooming diatom species when present in concentrations > 80 cells ml-1. Ciliates generally contributed < 25% to copepod carbon ingestion. Acartia discaudata, Acartia clausi, and Centropages hamatus selectively consumed dinoflagellate and ciliate taxa whereas Temora longicornis remained an indiscriminate grazer during the entire study. Despite increasing rates of egg production in Acartia discaudata, at high concentrations (> 1 x 103 cells ml-1), Thalassiosira rotula inhibited hatching success such that recruitment to naupliar stage 2 was severely impaired compared with eggs hatched from females fed ~0.3 x 103 cells ml-1 concentrations of T. rotula. This is the first recorded evidence of embryogenic inhibition in A. discaudata

Community-acquired bacteremia among hospitalized children in rural central Africa

Objective: To describe the epidemiology of community-acquired bacteremia in children admitted to a rural hospital in central Africa and to identify useful diagnostic signs or symptoms. Methods: On admission, a blood culture was obtained from all children admitted to Children's Hospital of Lwiro between 1989 and 1990. Clinical and biologic signs of infection and nutritional status were recorded. Results: Among the 779 children included in the study, 15.9% were bacteremic on admission. The rate of bacteremia was the highest among children with jaundice (20/56; 35.7%) and fever (119/487; 24.4%). In contrast, children with severe malnutrition had a lower rate of bacteremia (13.2%) than weight growth retarded or well-nourished children (19.5%) (P = 0.046). Fever was the most useful diagnostic criteria (sensitivity and negative predictive value of 96.0% and 97.8%, respectively) even in severely malnourished children (sensitivity and negative predictive value of 96.4% and 99.1%, respectively). Enterobacteriacea, mostly Salmonella spp, caused 73% of the bacteremia. There was a high rate of resistance to ampicillin and chloramphenicol among the responsible organisms. Only 31 (47.7%) of 65 bacteremic children responded to the combination of ampicillin and gentamicin. The presence of bacteremia on admission did not significantly increase the risk of morality during hospitalization (19.4% compared with 13.5%; P = 0.088). Age less than 12 months and jaundice were independent risk factors for deaths in bacteremic children. Conclusions: Community-acquired bacteremia caused by multiresistant Enterobacteriacea is an important problem of hospitalized well-nourished and malnourished children in central Africa. Fever on admission is a sensitive diagnostic sign, even in malnourished children.SCOPUS: ar.jinfo:eu-repo/semantics/publishe