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D.m. Ramsay - One of the best experts on this subject based on the ideXlab platform.

B A Sturt - One of the best experts on this subject based on the ideXlab platform.

Peter H. Becker - One of the best experts on this subject based on the ideXlab platform.

  • Terns in trouble: demographic consequences of low breeding success and recruitment on a common tern population in the German Wadden Sea
    Journal of Ornithology, 2012
    Co-Authors: K. Lesley Szostek, Peter H. Becker
    Abstract:

    The nationally endangered breeding population of Common Terns Sterna hirundo in the German Wadden Sea has been rapidly declining in recent years. In an attempt to identify the causes for this decline we analysed the demography of the Jade Bay population based on the “Banter See” colony. This colony has been intensively studied for over 18 years and has been declining in recent years. We estimated apparent survival rates of breeders and non-breeders of different ages using multi-state capture–recapture models based on individual life histories. The population growth rates of the Banter See colony and Lower Saxony population were estimated, and possible future trajectories were projected using a matrix model approach. Adult survival rates (0.9) have remained constant, but since 2002 subadult survival has decreased significantly (0.36–0.28). We found significantly lower breeding success as well as lower and delayed recruitment. These changes in vital rates probably caused the shift in the Banter See colony growth rate from an increasing phase before 2002 to a declining phase after and most likely occurred due to low pelagic prey fish stocks in the North Sea, the most important food source for terns in the Wadden Sea. Should the population decline continue at the current rates, the Banter See colony could decrease by 11% and the Lower Saxony Wadden Sea population by an alarming 57% between 2009 and 2015. Zusammenfassung Seeschwalben mit Problemen: Demographische Konsequenzen von geringem Bruterfolg und geringer Rekrutierung in einer Flussseeschwalben-Population im Deutschen Wattenmeer Die Brutpopulation der Flussseeschwalbe Sterna hirundo im niedersächsischen Wattenmeer hat in den letzten Jahren einen starken Rückgang erfahren. Diese Entwicklung ist bedenklich, da diese Art seit 2007 auf der Roten Liste als stark gefährdet eingestuft wird. Um Ursachen für den Rückgang in der Zahl der Brutpaare festzustellen, wurde in dieser Studie die Demographie der Flussseeschwalbenpopulation am Jadebusen untersucht, mit besonderem Augenmerk auf die Kolonie „Banter See“ in Wilhelmshaven. Diese Kolonie wird seit über 18 Jahren eingehend untersucht und zeigt ebenfalls einen rückläufigen Trend. Überlebensraten von Brütern und Nichtbrütern verschiedener Altersgruppen wurden anhand eines Multi-State Capture–Recapture Modells, basierend auf individuellen Lebensgeschichten, ermittelt. Die Wachstumsrate der Banter See Kolonie wurde in zwei Phasen unterteilt: eine wachsende Phase vor 2002 und eine abnehmende Phase danach. Diese Entwicklung wurde durch Änderungen in wesentlichen demographischen Raten hervorgerufen, so wie signifikant geringerer Bruterfolg, signifikant weniger und spätere Rekrutierung und signifikant geringere Überlebensraten zweijähriger Vögel seit 2002 (von 36% auf 29%). Die Überlebensraten adulter Vögel (90%) dagegen blieben in dieser Zeit konstant. Die Änderungen in demographischen Raten ist höchstwahrscheinlich auf niedrige Herings—Clupea harengus und Sprottenbestände Clupea sprattus in der Nordsee zurückzuführen, die die wichtigste Nahrungsquelle für Seeschwalben im Wattenmeer darstellen. Andere Flussseeschwalbenkolonien im Wattenmeer erlebten einen wesentlich schlimmeren Rückgang in der Zahl der Brutpaare und haben begonnen sich aufzulösen. Sollte der Rückgang der Brutpaare im derzeitigen Ausmaß weitergehen, könnte sich die Banter See Kolonie bis 2015 um bis zu 11% der Brutpopulation von 2009 verringern, während die gesamte Wattenmeer Population in der Zeit sogar um alarmierende 57% der Bestände von 2008 abzunehmen droht.

  • terns in trouble demographic consequences of low breeding success and recruitment on a common tern population in the german wadden sea
    Journal of Ornithology, 2012
    Co-Authors: Lesley K Szostek, Peter H. Becker
    Abstract:

    The nationally endangered breeding population of Common Terns Sterna hirundo in the German Wadden Sea has been rapidly declining in recent years. In an attempt to identify the causes for this decline we analysed the demography of the Jade Bay population based on the “Banter See” colony. This colony has been intensively studied for over 18 years and has been declining in recent years. We estimated apparent survival rates of breeders and non-breeders of different ages using multi-state capture–recapture models based on individual life histories. The population growth rates of the Banter See colony and Lower Saxony population were estimated, and possible future trajectories were projected using a matrix model approach. Adult survival rates (0.9) have remained constant, but since 2002 subadult survival has decreased significantly (0.36–0.28). We found significantly lower breeding success as well as lower and delayed recruitment. These changes in vital rates probably caused the shift in the Banter See colony growth rate from an increasing phase before 2002 to a declining phase after and most likely occurred due to low pelagic prey fish stocks in the North Sea, the most important food source for terns in the Wadden Sea. Should the population decline continue at the current rates, the Banter See colony could decrease by 11% and the Lower Saxony Wadden Sea population by an alarming 57% between 2009 and 2015.

D. M. Brasher - One of the best experts on this subject based on the ideXlab platform.

William W Barrow - One of the best experts on this subject based on the ideXlab platform.

  • functional cloning of bacillus anthracis dihydrofolate reductase and confirmation of natural resistance to trimethoprim
    Antimicrobial Agents and Chemotherapy, 2004
    Co-Authors: Esther W Barrow, Philip C Bourne, William W Barrow
    Abstract:

    Bacillus anthracis is reported to be naturally resistant to trimethoprim (TMP), a drug that inhibits dihydrofolate reductase (DHFR), a key enzyme in the folate pathway. A microdilution broth assay established that the MIC of TMP for B. anthracis STerne is >2,048 but ≤4,096 μg/ml. A putative DHFR sequence was amplified from B. anthracis STerne genomic DNA. The PCR product was cloned into the Invitrogen pCRT7/CT-TOPO vector, followed by transformation into Escherichia coli TOP10F′ chemically competent cells. Plasmid DNA from a clone showing the correct construct with a thrombin cleavage site attached downstream from the terminus of the cloned PCR product was transformed into E. coli BL21 Star (DE3)pLysS competent cells for expression of the six-histidine-tagged fusion protein and purification on a His-Bind resin column. Functionality of the purified STerne recombinant DHFR (STerne rDHFR) was confirmed in an established enzyme assay. The 50% inhibitory concentrations of TMP and methotrexate for the STerne rDHFR were found to be 77,233 and 12.2 nM, respectively. TMP resistance was observed with E. coli BL21 Star (DE3)pLysS competent cells transformed with the STerne DHFR gene. Alignment of the amino acid sequence of the STerne DHFR gene revealed 100% homology with various virulent strains of B. anthracis. These results confirm the natural resistance of B. anthracis to TMP and clarify that the resistance is correlated to a lack of selectivity for the chromosomally encoded gene product. These findings will assist in the development of narrow-spectrum antimicrobial agents for treatment of anthrax.