This work was funded, in part, by the Great Lakes Fishery Commission and the Annis Water Resources Institute. Use of trade, product, or firm names does not imply endorsement by the U. S. Government. This article is Contribution 1867 of the U. S. Geological Survey Great Lakes Science Center.

1. مختبر التجربة <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> الحصول على الأسماك فريسة لتغذية الأسماك المفترسة أثناء التجربة. ويفضل أن يتم القبض على هذه الأسماك فريسة في الميدان، والمجمدة، وتخزينها في حوالي -30 ° C. النظر في عمليات الصيد التجارية كمصدر محتمل للأسماك الفريسة. </li><li style=";text-align:right;direction:rtl"> إدخال الأسماك المفترسة إلى الخزانات المختبر لاستخدامها في التجربة. ما يصل الى 15 الأسماك المفترسة قد تم ادخالها في كل من الدبابات 870-L، وتصل إلى 30 الأسماك المفترسة قد تم ادخالها في كل من الدبابات 2،380-L في دراسات سابقة 16،18. </li><li style=";text-align:right;direction:rtl"> تأقلم الأسماك المفترسة إلى اتباع نظام غذائي من الأسماك فريسة المحدد. وبمجرد تأقلم، ينبغي أن تظل الأسماك المفترسة على هذا النظام الغذائي لمدة 1-3 أشهر قبل البدء في التجربة. </li><li style=";text-align:right;direction:rtl"> جانبا عينات من الأسماك فريسة عن طريق اختيار عشوائي 10 إلى 20 عينات مركبة من مجموعة من الأسماك فريسة. عدد من الأسماك فريسة في عينة المركبة يمكن أن تتراوح 3-100، اعتمادا على حجم الفريسةالأسماك. يجب أن يكون كل عينة مركبة حصل، المجمدة، وتخزينها في حوالي -30 ° C مزدوج. </li><li style=";text-align:right;direction:rtl"> بدء التجربة عن طريق التضحية 30 إلى 50٪ من الأسماك في كل من الدبابات. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إلى الموت ببطء السمك، مزيج 8 غرام من Finquel مع 45 لتر من الماء في حاوية بلاستيكية كبيرة ثم ضع السمك في وعاء مع الحل Finquel. </li><li style=";text-align:right;direction:rtl"> الموت الرحيم مرة واحدة، ضع كل من ضحى من الأسماك دبابة واحدة في كيس، ثم حقيبة مزدوجة، وتخزينها في حوالي -30 درجة مئوية حتى وقت المعالجة. </li><li style=";text-align:right;direction:rtl"> تزن كل واحدة من الأسماك المتبقية في كل من الدبابات، وتسجيل الأوزان. ومن المرجح أن تكون هناك حاجة إلى مخدر لإجراء زنها. </li><li style=";text-align:right;direction:rtl"> لتخدير السمك، مزيج 4.6 غرام من Finquel مع 45 لتر من الماء في حاوية بلاستيكية كبيرة، ثم ضع السمك في وعاء مع الحل Finquel. </li><li style=";text-align:right;direction:rtl"> انتظر بضع دقائق للمخدر نافذ المفعول قبل وزنها السمك. </li></ol></li><li style=";text-align:right;direction:rtl"> في كل يوم من التجربة، وذوبان الجليدكمية مناسبة من الأسماك تفترس وقطع السمك إلى قطع فريسة وزنها حوالي 1-5 غرام. الموازنة بين كمية الأسماك فريسة لتوضع في كل من الدبابات، ثم إسقاط القطع الأسماك فريسة في كل خزان والسماح للأسماك المفترسة حوالي 1 ساعة لإطعام. ثم إزالة جميع المواد الغذائية غير مأكول، والسماح الطعام في الهواء الجاف لمدة 20 دقيقة، ثم تزن الطعام غير مأكول لكل من الدبابات. تسجيل كمية الطعام وضعت في خزان وكمية من المواد الغذائية غير مأكول لكل من الدبابات كل يوم. ملاحظة: للتجربة تمثيلية، تم تغذية تراوت البحيرة والكثير من الطعام لأنها سوف تستهلك خلال فترة الرضاعة واحدة كل يوم 18. ومع ذلك، يمكن أيضا أن توضع الأسماك المفترسة على حصص ثابتة 16،19. </li><li style=";text-align:right;direction:rtl"> إنهاء التجربة عن طريق التضحية كل من الأسماك المفترسة المتبقية في كل من الدبابات. إلى الموت ببطء السمك، مزيج 8 غرام من Finquel مع 45 لتر من الماء في حاوية بلاستيكية كبيرة ثم ضع السمك في وعاء مع الحل Finquel. سجل ركان وزن كل من الأسماك التضحية. للحصول على نتائج يمكن الاعتماد عليها، يجب أن يعمل التجربة لمدة 100 يوما على الأقل، ويفضل لمدة 130 يوما على الأقل. وضع كل من الأسماك من خزان في كيس واحد، كيس ثم مزدوجة، وتخزينها في حوالي -30 درجة مئوية حتى وقت المعالجة. </li></ol> التجانس 2. السمك <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> اختيار مجموعة من الأسماك المفترسة و / أو المركبة الأسماك فريسة للذوبان. السماح للمركبات لذوبان الجليد جزئيا. قد تتطلب كل مركب 0،5-1 ساعة إلى التجانس. </li><li style=";text-align:right;direction:rtl"> استخدام الخلاطات مناسبة الحجم، التجانس كل من المواد المركبة. لكل مركب، ضع عينة (من 50 إلى 100 غرام) من جناسة في وعاء تنظيفها، تشطف الأسيتون، والمسمى. ثم تتويج جرة وجرة تخزين في حوالي -30 ° C حتى وقت المعالجة. </li><li style=";text-align:right;direction:rtl"> غسل جميع المعدات المستخدمة في التجانس السمك، ثم شطف بشكل صحيح مع الماء المقطر والميثانول، بين العينات. </li></ol> 3. استخراج <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> تزن 20.0 غراممن إذابة أنسجة الأسماك متجانسة في كوب 200 مل. </li><li style=";text-align:right;direction:rtl"> إضافة حوالي 40 غرام من كبريتات الصوديوم وتخلط جيدا مع ملعقة. </li><li style=";text-align:right;direction:rtl"> إضافة حل بديل ارتفاع تحتوي على المتجانسات 30، 61، 161، و166. سبايك بتركيز أن ينتج تركيز النهائي من 20 نانوغرام / مل في استخراج. </li><li style=";text-align:right;direction:rtl"> السماح للعينة لتجف RT في حين خلط كل 20 دقيقة. </li><li style=";text-align:right;direction:rtl"> سماح العينة للوصول إلى اتساق الرمال الجافة، وعند هذه النقطة العينة جاهزة للاستخراج. </li><li style=";text-align:right;direction:rtl"> إعداد جهاز استخراج سوكسليت مع قارورة 500 مل تحتوي على رقائق تفلون يغلي، سوكسليت، والمكثف. </li><li style=";text-align:right;direction:rtl"> يضاف خليط السمك المجفف إلى كشتبان الزجاج مع قرص أسفل fritted الخشنة أو كشتبان الورق. </li><li style=";text-align:right;direction:rtl"> إضافة 150 مل من الهكسان 50٪ و 50٪ ثنائي كلورو ميثان إلى الكأس المستخدمة في عينة ويحرك بينما كشط جدران الكأس مع ملعقة. </li><li style=";text-align:right;direction:rtl"> نقل المذيب إلى أعلى سوكسليت مع قارورة تعلق والسماح لها للتنقل عبر سوكسليت و<html> إلى القارورة. </li><li style=";text-align:right;direction:rtl"> أكرر مرة ثانية مع 150 مل مرة أخرى. </li><li style=";text-align:right;direction:rtl"> وضع سوكسليت مع قارورة تعلق على عنصر التدفئة وإرفاق المكثف. </li><li style=";text-align:right;direction:rtl"> بدوره على عنصر التدفئة وتقديم مذيب ليغلي لطيف، ثم استخراج مدة لا تقل عن 16 ساعة والتأكد من أن يتم توفير الماء البارد للمكثفات. </li><li style=";text-align:right;direction:rtl"> بعد السماح لتبريد المذيب، تحقق لمعرفة ما إذا كان أي من عينة قوارير تحتوي على الماء. بالنسبة لأولئك قوارير تحتوي على الماء، إضافة كبريتات الصوديوم ودوامة حتى يتم امتصاص الماء من كبريتات الصوديوم. </li><li style=";text-align:right;direction:rtl"> تركيز العينة باستخدام عينة المكثف النيتروجين أو Kaderna الدنماركية (KD) إعداد الأواني الزجاجية مع حمام الماء الساخن. </li><li style=";text-align:right;direction:rtl"> السماح للعينة لتتبخر إلى حجم أقل من 2 مل، ومن ثم جلب إلى الحجم النهائي من 5 مل باستخدام الغسيل صغيرة من الهكسان لنقل عينة من الأواني الزجاجية المستخدمة لقارورة حجمية 5 مل. </li><li style=";text-align:right;direction:rtl"> نقل إلى 10 مل قارورة وتسمية بمعلومات العينة. </li></ol>ق = &quot;jove_title&quot;&gt; 4. استخراج النظيفة المتابعة <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> إعداد المحمض هلام السيليكا بإضافة 44 غرام من حمض الكبريتيك المركز إلى 100 غرام من تنشيط هلام السيليكا. </li><li style=";text-align:right;direction:rtl"> إضافة 10 غرام من المحمضة هلام السيليكا في عمود اللوني صغير يحتوي على المكونات الصغيرة من الصوف الزجاجي في الأسفل. </li><li style=";text-align:right;direction:rtl"> إضافة 1 مل من مستخلص العينة إلى العمود بعد التنظيف المسبق العمود مع 10 مل من الهكسان. </li><li style=";text-align:right;direction:rtl"> أزل العمود مع 20 مل من الهكسان وجمع في مدبب 20 مل أنبوب زجاجي. </li><li style=";text-align:right;direction:rtl"> وضع أنبوب زجاجي على جهاز المبخر النيتروجين (N-برنامج عمل فيينتيان) تحت تيار من النيتروجين ومغمورة في الماء الساخن. </li><li style=";text-align:right;direction:rtl"> تتبخر إلى أقل من 1 مل ولكن ليس للجفاف. </li><li style=";text-align:right;direction:rtl"> إزالة من جهاز N-برنامج عمل فيينتيان ونقل إلى قارورة حجمية 1 مل مع الغسيل صغيرة من الهكسان. </li><li style=";text-align:right;direction:rtl"> نقل إلى 1.8 مل الاوتوماتيكى قارورة المسمى مع معلومات العينة. </li><li style=";text-align:right;direction:rtl"> ارتفاع 4 ميكرولتر من معيار داخلي في القارورة. العينة هي الآن جاهزة للتحليل. </li></ol> 5. شرجيysis بواسطة جهاز الكروماتوجرافي الغازي - الطيف الكتلي عن طريق سلبي التأين الكيميائية <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> استخدام معايير لمعايرة العدادات: هي المعايير المتاحة في مخاليط تتكون من مجموعات من المتجانسات فصل جيدا. يمزج 1-5 تتكون من كل من المتجانسين وجدت في Arochlors 1016، 1221، 1232، و 1242، 1248، 1254 تقريبا، ويستخدم 1260. ميكس 1 بأنها مزيج المعايرة متعددة المستويات، وتأكيد النظام الخطي من خلال إعداد ما لا يقل عن خمسة مستويات المعايرة بتركيزات تتراوح بين 2 و 100 نانوغرام / مل. تستخدم يمزج 2-5 والمعايرة نقطة واحدة عن كل متجانس. </li><li style=";text-align:right;direction:rtl"> إعداد اللوني - نظام قياس الطيف الكتلي في وضع التأين السلبي الكيميائية مع الهيدروجين باعتبارها الناقل للغاز (1 مل / دقيقة) والميثان والغاز كاشف. </li><li style=";text-align:right;direction:rtl"> استخدام السيليكا تنصهر، العمود الشعري (60 م × 0.25 مم القطر الداخلي) المغلفة مع DB-XLB عند 0.25 ميكرون سمك الفيلم للانفصال. برنامج فرن درجة حرارة 60-212 درجة مئوية عند 25 ° C / دقيقة، ثم إلى 260 درجة مئوية في 1 ° C / دقيقة، ثم إلى 280 ° C في 4 درجات مئوية / دقيقة، مع وقت الانتظار النهائي 4 دقائق. يجب تعيين حاقن وخط نقل في درجة حرارة 280 درجة مئوية. حقن 1-2 ميكرولتر من العينة باستخدام طريقة الحقن splitless. </li><li style=";text-align:right;direction:rtl"> تحليل جميع المعايير وعينات من الطريقة القياسية الداخلية باستخدام 13 المسمى C decachlorobiphenyl. </li><li style=";text-align:right;direction:rtl"> إجراء فحص على معايرة الأولية عن طريق تشغيل معيار المصدر الثاني وAroclors 1242 و 1260، ومن ثم مقارنة القيم المتوقعة للالأروكلور متجانسا مع المبالغ لوحظ من هذا الإجراء الاختيار. </li><li style=";text-align:right;direction:rtl"> مرة واحدة تم إنجازه إجراء المعايرة الأولي بنجاح، تحليل كامل لجميع العينات. تشغيل المعايرة الاختيار كل عشرة عينات، وذلك باستخدام أي من خليط من معايرة معايرة الأولية. </li></ol> 6. حساب صافي الغذائية كفاءة نقل <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> حساب صافي كفاءة نقل الغذائية، γ، لكل تركيبة سو دبابات وPCB متجانس باستخدام المعادلة التالية: <img alt="المعادلة 1" fo:content-width="2in" src="/files/ftp_upload/51496/51496eq1.jpg" /> حيث [PCB و] هو متوسط ​​تركيز الكلور متجانس من الأسماك المفترسة في خزان في نهاية التجربة، W f هو متوسط ​​وزن السمكة المفترسة في خزان في نهاية التجربة، [PCB ط] هو متوسط ​​تركيز الكلور متجانس من الأسماك المفترسة في خزان في بداية التجربة، W ط هو متوسط ​​وزن السمكة المفترسة في بداية التجربة، ومقدار PCB متجانس بلعها يشير إلى وزن متجانس الكلور بلعها، في المتوسط، قبل كل تراوت البحيرة في الخزان أثناء التجربة. </li><li style=";text-align:right;direction:rtl"> حساب القاسم في المعادلة المذكورة أعلاه بضرب متوسط ​​تركيز متجانس PCB في المركبة الأسماك فريسة على المتوسط ​​مبلغ (الوزن) من الأسماك فريسة تؤكل في الأسماك المفترسة في الدر دباباتجي كامل التجربة. </li></ol>

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P., DeSorcie, T. J., Stedman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ontogenic+and+spatial+patterns+in+diet+and+growth+of+lake+trout+in+Lake+Michigan.">Ontogenic and spatial patterns in diet and growth of lake trout in Lake Michigan.</a> Transactions of the American Fisheries Society. 127 (2), 236-252 (1998).</li><li>Paterson, G., Whittle, D. M., Drouillard, K. G., Haffner, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Declining+lake+trout+(Salvelinus+namaycush)+energy+density:+are+there+too+many+salmonid+predators+in+the+Great+Lakes?.">Declining lake trout (Salvelinus namaycush) energy density: are there too many salmonid predators in the Great Lakes?.</a> Canadian Journal of Fisheries and Aquatic Sciences. 66 (6), 919-932 (2009).</li><li>Madenjian, C. P., O&#8217;Connor, D. V., Nortrup, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+approach+toward+evaluation+of+fish+bioenergetics+models.">A new approach toward evaluation of fish bioenergetics models.</a> Canadian Journal of Fisheries and Aquatic Sciences. 57 (5), 1025-1032 (2000).</li><li>Madenjian, C. P., Pothoven, S. A., Kao, Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reevaluation+of+lake+trout+and+lake+whitefish+bioenergetics+models.">Reevaluation of lake trout and lake whitefish bioenergetics models.</a> Journal of Great Lakes Research. 39 (2), 358-364 (2013).</li><li>Madenjian, C. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+lake+whitefish+bioenergetics+model.">Evaluation of a lake whitefish bioenergetics model.</a> Transactions of the American Fisheries Society. 135 (1), 61-75 (2006).</li><li>Madenjian, C. P., O&#8217;Connor, D. V., Chernyak, S. M., Rediske, R. R., O&#8217;Keefe, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+chinook+salmon+(Oncorhynchus+tshawytscha)+bioenergetics+model.">Evaluation of a chinook salmon (Oncorhynchus tshawytscha) bioenergetics model.</a> Canadian Journal of Fisheries and Aquatic Sciences. 61 (4), 627-635 (2004).</li><li>Madenjian, C. P., David, S. R., Rediske, R. R., O&#8217;Keefe, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Net+trophic+transfer+efficiencies+of+polychlorinated+biphenyl+congeners+to+lake+trout+(Salvelinus+namaycush)+from+its+prey.">Net trophic transfer efficiencies of polychlorinated biphenyl congeners to lake trout (Salvelinus namaycush) from its prey.</a> Environmental Toxicology and Chemistry. 31 (12), 2821-2827 (2012).</li><li>Madenjian, C. P., O'Connor, D. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laboratory+evaluation+of+a+lake+trout+bioenergetics+model.">Laboratory evaluation of a lake trout bioenergetics model.</a> Transactions of the American Fisheries Society. 128 (5), 802-814 (1999).</li><li>Ballschmiter, K., Bacher, R., Mennel, A., Fischer, R., Riehle, U., Swerev, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+determination+of+chlorinated+biphenyls,+chlorinated+dibenzodioxins,+and+chlorinated+dibenzofurans+by+GC-MS.">The determination of chlorinated biphenyls, chlorinated dibenzodioxins, and chlorinated dibenzofurans by GC-MS.</a> HRC Journal of High Resolution Chromatography. 15 (4), 260-270 (1992).</li><li>Madenjian, C. P., David, S. R., Pothoven, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+activity+and+energy+budget+balancing+algorithm+on+laboratory+performance+of+a+fish+bioenergetics+model.">Effects of activity and energy budget balancing algorithm on laboratory performance of a fish bioenergetics model.</a> Transactions of the American Fisheries Society. 141 (5), 1328-1337 (2012).</li><li>Lieb, A. J., Bills, D. D., Sinnhuber, R. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accumulation+of+dietary+polychlorinated+biphenyls+(Aroclor+1254)+by+rainbow+trout.">Accumulation of dietary polychlorinated biphenyls (Aroclor 1254) by rainbow trout.</a> Journal of Agricultural and Food Chemistry. 22 (4), 638-642 (1974).</li><li>Niimi, A. J., Oliver, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+half-lives+of+polychlorinated+biphenyl+(PCB)+congeners+in+whole+fish+and+muscle+of+rainbow+trout+(Salmo+gairdneri).">Biological half-lives of polychlorinated biphenyl (PCB) congeners in whole fish and muscle of rainbow trout (Salmo gairdneri).</a> Canadian Journal of Fisheries and Aquatic Sciences. 40 (9), 1388-1394 (1983).</li><li>Gobas, F. A. P. C., Wilcockson, J. B., Russell, R. W., Haffner, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+biomagnification+in+fish+under+laboratory+and+field+conditions.">Mechanism of biomagnification in fish under laboratory and field conditions.</a> Environmental Science and Technology. 33 (1), 133-141 (1999).</li><li>Dmitrovic, J., Chan, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+polychlorinated+biphenyl+congeners+in+human+milk+by+gas+chromatography+&#8211;+negative+chemical+ionization+mass+spectrometry+after+sample+clean-up+by+solid-phase+extraction.">Determination of polychlorinated biphenyl congeners in human milk by gas chromatography &#8211; negative chemical ionization mass spectrometry after sample clean-up by solid-phase extraction.</a> Journal of Chromatography B. 778 (1-2), 147-155 (2002).</li><li>Zorn, M. E., Gibbons, R. D., Sonzogni, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Weighted+least-squares+approach+to+calculating+limits+of+detection+and+quantification+by+modeling+variability+as+a+function+of+concentration.">Weighted least-squares approach to calculating limits of detection and quantification by modeling variability as a function of concentration.</a> Analytical Chemistry. 69 (15), 3069-3075 (1997).</li></ol>

لتقديرات أكثر دقة من γ، يجب أن يكون المجرب قادرة على تتبع بدقة كل من كمية الغذاء وضعها في كل من الدبابات وكمية من المواد الغذائية غير مأكول في كل من الدبابات أثناء التجربة. ولتحقيق ذلك، يجب أن يكون المجرب قادرة على إزالة جميع المواد الغذائية غير مأكول من الدبابات وتحد...

Of all of the factors affecting the rate at which fish accumulate contaminants, the efficiency with which fish retain contaminants from the food that they eat is one of the most important1-3. Risk assessment models have been developed to predict future risks to both people and wildlife eating contaminated fish under various scenarios of environmental contamination, and the reliability of these predictions critically depends on the accuracy of the estimates of the efficiency at which fish retain contaminants from their food4.
The efficiency with which the contaminant in the food ingested by the predator is transported through the gut wall is known as gross trophic transfer efficiency5. A portion of the quantity of the contaminant transported through the gut wall of the predator may eventually be lost through depuration and/or metabolic transformation. The efficiency with which the contaminant in the food ingested by the predator is retained by the predator, including any losses due to elimination and metabolic transformation, is known as net trophic transfer efficiency6.
Gross trophic transfer efficiency of organic contaminants to fish from their prey appears to vary with the contaminant&#8217;s chemical properties, including lipid affiliation as measured by the octanol-water partition coefficient, Kow3,7. According to an empirical relationship developed by Thomann3, gross trophic transfer efficiency is relatively high when log Kow is equal to a value between 5 and 6. Gross trophic transfer efficiency declines exponentially at a rate of 50% per unit of log Kow as log Kow increases from 6 to 10, according to the Thomann3 relationship.
Nevertheless, the gross and net trophic transfer efficiencies of polychlorinated biphenyl (PCB) congeners to fish from their prey do not appear to follow the Thomann3 relationship in most cases. Although the trophic transfer efficiencies of PCB congeners to lake whitefish (Coregonus clupeaformis) from its food followed the relationship proposed by Thomann8, trophic transfer efficiencies of PCB congeners were either just weakly related or not related at all to log Kow for Atlantic salmon (Salmo salar)9, rainbow trout (Oncorhynchus mykiss)10, coho salmon (Oncorhynchus kisutch)11, and northern pike (Esox lucius)11.
The overall goal of this study was to present a laboratory technique for estimating the net trophic transfer efficiencies of PCB congeners to a piscivorous fish from its prey. Lake trout (Salvelinus namaycush) was chosen as the piscivorous fish for our experiment because lake trout are relatively easy to maintain in laboratory tanks. Bloater (Coregonus hoyi) was selected as the prey fish to be fed to the lake trout because bloater is eaten by lake trout in its natural setting12. In addition, we determined whether the net trophic transfer efficiencies for lake trout estimated from our laboratory experiment followed the Thomann3 relationship. We also determined whether the degree of activity by the lake trout had a significant effect on net trophic transfer efficiency (&#947;) of the PCB congeners. Activity by lake trout in the Laurentian Great Lakes is believed to have recently increased because changes in the food webs have caused lake trout to allocate more energy toward searching for food13. Lake trout were forced to exercise in one set of tanks by subjecting these lake trout to relatively high flow rates, whereas the other lake trout were permitted to remain relatively inactive by subjecting them to relatively low flow rates. Finally, the specific details of our laboratory procedure that need to be carefully followed to ensure the highest degree of accuracy in the &#947; estimates and to make the laboratory results applicable to the field are discussed, as well as future directions for research building on our laboratory technique. Net trophic transfer efficiency can be estimated both in the laboratory and in the field, and advantages and disadvantages are associated with both approaches. Accuracy in the estimate of &#947; depends on the accuracy of the estimate of food consumption. The amount of food eaten by fish in the laboratory can be accurately determined when proper protocols are followed, whereas the amount of food eaten by fish in the field is typically estimated via bioenergetics modeling. Use of bioenergetics modeling to derive the amount of food eaten has the potential to introduce a substantial amount of uncertainty into the estimates of food consumption. Fish bioenergetics models have been shown to estimate food consumption with no detectable bias for the case of lake trout14,15, but considerable bias in bioenergetics model estimates of food consumption has been detected for the case of lake whitefish15,16. On the other hand, estimates of net trophic transfer efficiency estimated in the laboratory may not be applicable to the field due to a difference in feeding rates between the laboratory and the field17. Evidence from both the laboratory and the field suggest that feeding rate can influence &#947;14,17.
The methodology used in the present study for estimating &#947; in the laboratory is applicable to situations where the predator fish is fed prey fish, and the amount of prey fish eaten by the predator can be accurately tracked. To accomplish this, the experimenter must weigh all of the food before placement in the tank; and the experimenter must be able to remove all of the uneaten food from the tank, and then weigh the uneaten food. In addition, an adequate suite of mixers and blenders should be available to obtain a sufficient degree of homogenization of the samples of both predator and prey fish. Finally, the gas chromatography &#8211; mass spectrometry instrumentation used to determine the PCB congener concentrations must be capable of detecting and quantifying individual PCB congeners at relatively low concentrations.

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laboratory estimation of net trophic transfer efficiencies of pcb congeners to lake trout (salvelinus namaycush) from its prey

ووصف أسلوب لتقدير كفاءة المختبر من صافي الغذائية نقل (γ) من ثنائي الفينيل متعدد الكلورة (PCB) متجانسا إلى الأسماك الآكلة للأسماك من فرائسها هنا. خلال تجربة مختبرية 135 يوم، ونحن تغذية الرنجة (Coregonus hoyi) التي كانت قد اشتعلت في بحيرة ميشيغان، وتراوت البحيرة (Salvelinus namaycush) يوضع في ثماني دبابات المختبر. الرنجة هو الفريسة الطبيعية لسمك السلمون المرقط البحيرة. في أربعة خزانات، تم استخدام معدل تدفق عالية نسبيا لضمان النشاط المرتفع نسبيا من سمك السلمون المرقط البحيرة، في حين تم استخدام معدل التدفق المنخفض في خزانات الأربعة الأخرى، مما يسمح لانخفاض النشاط تراوت البحيرة. على أساس دبابة من قبل للدبابات، وسجلت كمية الطعام التي يتم تناولها من قبل تراوت البحيرة في كل يوم من التجربة. كان وزنه كل تراوت البحيرة في بداية ونهاية التجربة. تمت التضحية أربعة إلى تسعة تراوت البحيرة من كل من الدبابات ثمانية في بداية التجربة، وجميع سمك السلمون المرقط البحيرة 10 المتبقية في كل من الدبابات euthanأوتوماتيكية في نهاية التجربة. نحن مصممون تركيزات PCB 75 متجانسا في تراوت البحيرة في بداية التجربة، في تراوت البحيرة في نهاية التجربة، والرنجة في تغذية سمك السلمون المرقط البحيرة أثناء التجربة. وبناء على هذه القياسات، تم حساب γ لكل من PCB 75 متجانسا في كل من الدبابات ثمانية. يعني تم حساب γ لكل من 75 متجانسا PCB للتراوت البحيرة على حد سواء نشطة وغير نشطة. لأنه تم نسخ التجربة في ثماني دبابات، والخطأ المعياري حول يعني يمكن تقدير γ. نتائج من هذا النوع من التجربة مفيدة في نماذج تقييم المخاطر للتنبؤ المخاطر المستقبلية للإنسان والحياة البرية تناول الأسماك الملوثة تحت سيناريوهات مختلفة من التلوث البيئي.

أظهر بحيرة سمك السلمون المرقط كمية كبيرة من النمو خلال التجربة، كما تعني تراوت البحيرة الأولية تراوحت أوزان 694-907 غرام بينما تعني تراوت البحيرة النهائية تراوحت أوزان من 853 إلى 1،566 غرام (الجدول 1). متوسط ​​كمية الطعام المستهلكة من قبل تراوت البحيرة أثناء التج?...

Watch this Scientific Journal Video about Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout Salvelinus namaycush from Its Prey at JoVE.com

Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout Salvelinus namaycush from Its Prey

ويرد تقنية المختبرات لتقدير صافي كفاءة نقل الغذائية من ثنائي الفينيل متعدد الكلورة (PCB) متجانسا إلى الأسماك الآكلة للأسماك من فرائسها. لتحقيق أقصى قدر من قابلية تطبيق النتائج المخبرية إلى الميدان، ويجب أن تغذى الأسماك الآكلة للأسماك الأسماك الفريسة التي تؤكل عادة في هذا المجال.

تقدير مختبر صافي الغذائية الكفاءة نقل المتجانسات PCB إلى بحيرة سمك السلمون المرقط (<em&gt; Salvelinus namaycush</em&gt;) من فريسته

A technique for laboratory estimation of net trophic transfer efficiency (&#947;) of polychlorinated biphenyl (PCB) congeners to piscivorous fish from ...

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Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout (Salvelinus namaycush) from Its Prey

10.9K Views.  U. S. Geological Survey.  ويرد تقنية المختبرات لتقدير صافي كفاءة نقل الغذائية من ثنائي الفينيل متعدد الكلورة (PCB) متجانسا إلى الأسماك الآكلة للأسماك من فرائسها. لتحقيق أقصى قدر من قابلية تطبيق النتائج المخبرية إلى الميدان، ويجب أن تغذى الأسماك الآكلة للأسماك الأسم...

Video: Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout Salvelinus namaycush from Its Prey

Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration.
Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release.
The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.

Lake eutrophication is a water quality issue worldwide, making the need to identify and control nutrient sources critical. Laboratory determination of phosphorus release rates from sediment cores is a valuable approach for determining the role of internal phosphorus loading and guiding management decisions.

التي تحددها المختبر الفوسفور الجريان من بحيرة الرواسب كمقياس للتحميل الفوسفور الداخلية

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) ...

A Fish-feeding Laboratory Bioassay to Assess the Antipredatory Activity of Secondary Metabolites from the Tissues of Marine Organisms

Marine chemical ecology is a young discipline, having emerged from the collaboration of natural products chemists and marine ecologists in the 1980s with the goal of examining the ecological functions of secondary metabolites from the tissues of marine organisms. The result has been a progression of protocols that have increasingly refined the ecological relevance of the experimental approach. Here we present the most up-to-date version of a fish-feeding laboratory bioassay that enables investigators to assess the antipredatory activity of secondary metabolites from the tissues of marine organisms. Organic metabolites of all polarities are exhaustively extracted from the tissue of the target organism and reconstituted at natural concentrations in a nutritionally appropriate food matrix. Experimental food pellets are presented to a generalist predator in laboratory feeding assays to assess the antipredatory activity of the extract. The procedure described herein uses the bluehead, Thalassoma bifasciatum, to test the palatability of Caribbean marine invertebrates; however, the design may be readily adapted to other systems. Results obtained using this laboratory assay are an important prelude to field experiments that rely on the feeding responses of a full complement of potential predators. Additionally, this bioassay can be used to direct the isolation of feeding-deterrent metabolites through bioassay-guided fractionation. This feeding bioassay has advanced our understanding of the factors that control the distribution and abundance of marine invertebrates on Caribbean coral reefs and may inform investigations in diverse fields of inquiry, including pharmacology, biotechnology, and evolutionary ecology.

This bioassay employs a model predatory fish to assess the presence of feeding-deterrent metabolites from organic extracts of the tissues of marine organisms at natural concentrations using a nutritionally comparable food matrix.

مختبر الأحيائي تغذية الأسماك لتقييم آخر Antipredatory من المركبات الثانوية من الأنسجة من الكائنات البحرية

Marine chemical ecology is a young discipline, having emerged from the collaboration of natural products chemists and marine ecologists in the 1980s with ...

Automated Gel Size Selection to Improve the Quality of Next-generation Sequencing Libraries Prepared from Environmental Water Samples

Next-generation sequencing of environmental samples can be challenging because of the variable DNA quantity and quality in these samples. High quality DNA libraries are needed for optimal results from next-generation sequencing. Environmental samples such as water may have low quality and quantities of DNA as well as contaminants that co-precipitate with DNA. The mechanical and enzymatic processes involved in extraction and library preparation may further damage the DNA. Gel size selection enables purification and recovery of DNA fragments of a defined size for sequencing applications. Nevertheless, this task is one of the most time-consuming steps in the DNA library preparation workflow. The protocol described here enables complete automation of agarose gel loading, electrophoretic analysis, and recovery of targeted DNA fragments. 
In this study, we describe a high-throughput approach to prepare high quality DNA libraries from freshwater samples that can be applied also to other environmental samples. We used an indirect approach to concentrate bacterial cells from environmental freshwater samples; DNA was extracted using a commercially available DNA extraction kit, and DNA libraries were prepared using a commercial transposon-based protocol. DNA fragments of 500 to 800 bp were gel size selected using Ranger Technology, an automated electrophoresis workstation. Sequencing of the size-selected DNA libraries demonstrated significant improvements to read length and quality of the sequencing reads.

This manuscript describes an automated gel size selection approach for purifying DNA fragments for next-generation sequencing. The Ranger Technology provides complete automation of the entire process of agarose gel loading, electrophoretic analysis, and recovery of targeted DNA fragments allowing for high-throughput and high quality next-generation sequencing libraries.

جل الآلي الحجم التحديد لتحسين نوعية المكتبات تسلسل الجيل المقبل من إعداد من عينات المياه البيئة

Next-generation sequencing of environmental samples can be challenging because of the variable DNA quantity and quality in these samples. High quality DNA ...

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic&#160;however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

Production bleed water (PBW) was treated with cupric oxide nanoparticles (CuO-NPs) and cellular toxicity was assessed in cultured human cells. The goal of this protocol was to integrate the native environmental sample into a cell culture format assessing the changes in toxicity due to CuO-NP treatment.

إزالة العناصر النزرة التي كتبها نحاسي أكسيد النانوية من اليورانيوم<em&gt; في الموقع</em&gt; استرداد التسييل المياه وتأثيره على بقاء الخلية

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted ...

Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling from hydrothermal sources in the Precambrian ocean was oxidized by molecular oxygen [O2] produced by cyanobacteria. The oldest BIFs, deposited prior to the Great Oxidation Event (GOE) at about 2.4 billion years (Gy) ago, could have formed by direct oxidation of Fe(II) by anoxygenic photoferrotrophs under anoxic conditions. As a method for testing the geochemical and mineralogical patterns that develop under different biological scenarios, we designed a 40 cm long vertical flow-through column to simulate an anoxic Fe(II)-rich marine upwelling system representative of an ancient ocean on a lab scale. The cylinder was packed with a porous glass bead matrix to stabilize the geochemical gradients, and liquid samples for iron quantification could be taken throughout the water column. Dissolved oxygen was detected non-invasively via optodes from the outside. Results from biotic experiments that involved upwelling fluxes of Fe(II) from the bottom, a distinct light gradient from top, and cyanobacteria present in the water column, show clear evidence for the formation of Fe(III) mineral precipitates and development of a chemocline between Fe(II) and O2. This column allows us to test hypotheses for the formation of the BIFs by culturing cyanobacteria (and in the future photoferrotrophs) under simulated marine Precambrian conditions. Furthermore we hypothesize that our column concept allows for the simulation of various chemical and physical environments &#8212; including shallow marine or lacustrine sediments.

Laboratory Simulation of an IronII-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

We simulated a Precambrian ferruginous marine upwelling system in a lab-scale vertical flow-through column. The goal was to understand how geochemical profiles of O2 and Fe(II) evolve as cyanobacteria produce O2. The results show the establishment of a chemocline due to Fe(II) oxidation by photosynthetically produced O2.

محاكاة المختبر من الحديد (II) الغنية نظام الموجات المتقلبة عصر ما قبل الكمبري البحرية لاستكشاف نمو البكتيريا الضوئي

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling ...

Development of Metarhizium anisopliae as a Mycoinsecticide: From Isolation to Field Performance

A major concern when developing commercial mycoinsecticides is the kill speed compared to that of chemical insecticides. Therefore, isolation and screening for the selection of a fast-acting, highly virulent entomopathogenic fungus are important steps. Entomopathogenic fungi, such as Metarhizium, Beauveria, and Nomurea, which act by contact, are better suited than Bacillus thuringiensis or nucleopolyhedrosis virus (NPV), which must be ingested by the insect pest. In the present work, we isolated 68 Metarhizium strains from infected insects using a soil dilution and bait method. The isolates were identified by the amplification and sequencing of the ITS1-5.8S-ITS2 and 26S rDNA region. The most virulent strain of Metarhizium anisopliae was selected based on the median lethal concentration (LC50) and time (LT50) obtained in insect bioassays against III-instar larvae of Helicoverpa armigera. The mass production of spores by the selected strain was carried out with solid-state fermentation (SSF) using rice as a substrate for 14 days. Spores were extracted from the sporulated biomass using 0.1% tween-80, and different formulations of the spores were prepared. Field trials of the formulations for the control of an H. armigera infestation in pigeon peas were carried out by randomized block design. The infestation control levels obtained with oil and aqueous formulations (78.0% and 70.9%, respectively) were better than the 63.4% obtained with chemical pesticide.

Development of Metarhizium anisopliae as a Mycoinsecticide: From Isolation to Field Performance

Here, we report the different stages involved in the knowledge-based development of an effective mycoinsecticide, including the isolation, identification, screening, and selection of the "best-fit" entomopathogenic fungus, Metarhizium anisopliae, for the control of insect pests in agriculture.

تطور ال<em&gt; ميتاريزيوم أنيسوبلياي</em&gt; باعتباره ميكوسكتيسيد: من العزلة إلى الأداء الميداني

A major concern when developing commercial mycoinsecticides is the kill speed compared to that of chemical insecticides. Therefore, isolation and ...

Procedures of Laboratory Fumigation for Pest Control with Nitric Oxide Gas

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on fresh products and procedures for residue analysis and product quality evaluation. An airtight fumigation chamber containing fresh fruit and vegetables is first flushed with nitrogen (N2) to establish an ultralow oxygen (ULO) environment followed by injection of NO. The fumigation chamber is then kept at a low temperature of 2 - 5 &#176;C for a specified time period necessary to kill a target pest to complete a fumigation treatment. At the end of a fumigation treatment, the fumigation chamber is flushed with N2 to dilute NO prior to opening the chamber to ambient air to prevent the reaction between NO and O2, which produces NO2 and may damage delicate fresh products. At different times after NO fumigation, NO2 in headspace and nitrate and nitrite in liquid samples were measured as residues. Product quality was evaluated after 2 weeks of post-treatment cold storage to determine effects of NO fumigation on product quality. Keeping&#160;O2 from reacting with NO is critical to NO fumigation and is an important part of the protocols. Measuring NO levels is challenging and a practical solution is provided. Possible protocol modifications are also suggested for measuring NO levels in the fumigation chambers as well as residues. NO fumigation has the potential to be a practical alternative to methyl bromide fumigation for postharvest pest control on fresh and stored products. This publication is intended to assist other researchers in conducting NO fumigation research for postharvest pest control and accelerating the development of NO fumigation for practical applications.

This paper describes nitric oxide (NO) fumigation protocols for postharvest pest control. Fumigation chambers are flushed with nitrogen (N2) to establish ultralow oxygen conditions before NO is injected. At the end, chambers are flushed with N2 to dilute NO before exposing products to ambient air to prevent exposure to NO2.

الإجراءات المختبرية التبخير للسيطرة على الآفات مع غاز أكسيد النيتريك

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on ...

Adherence of Bacteria to Plant Surfaces Measured in the Laboratory

This manuscript describes a method to measure bacterial binding to axenic plant surfaces in the light microscope and through the use of viable cell counts. Plant materials used include roots, sprouts, leaves, and cut fruits. The methods described are inexpensive, easy, and suitable for small sample sizes. Binding is measured in the laboratory and a variety of incubation media and conditions can be used. The effect of inhibitors can be determined. Situations that promote and inhibit binding can also be assessed. In some cases it is possible to distinguish whether various conditions alter binding primarily due to their effects on the plant or on the bacteria.

An easy method for measuring and characterizing bacterial adhesion to plants, particularly roots and sprouts, is described in this article.

الانضمام للبكتيريا لزراعة الأسطح قياسها في المختبر

This manuscript describes a method to measure bacterial binding to axenic plant surfaces in the light microscope and through the use of viable cell ...

Ecosystem Fabrication (EcoFAB) Protocols for The Construction of Laboratory Ecosystems Designed to Study Plant-microbe Interactions

Beneficial plant-microbe interactions offer a sustainable biological solution with the potential to boost low-input food and bioenergy production. A better mechanistic understanding of these complex plant-microbe interactions will be crucial to improving plant production as well as performing basic ecological studies investigating plant-soil-microbe interactions. Here, a detailed description for ecosystem fabrication is presented, using widely available 3D printing technologies, to create controlled laboratory habitats (EcoFABs) for mechanistic studies of plant-microbe interactions within specific environmental conditions. Two sizes of EcoFABs are described that are suited for the investigation of microbial interactions with various plant species, including Arabidopsis thaliana, Brachypodium distachyon, and Panicum virgatum. These flow-through devices allow for controlled manipulation and sampling of root microbiomes, root chemistry as well as imaging of root morphology and microbial localization. This protocol includes the details for maintaining sterile conditions inside EcoFABs and mounting independent LED light systems onto EcoFABs. Detailed methods for addition of different forms of media, including soils, sand, and liquid growth media coupled to the characterization of these systems using imaging and metabolomics are described. Together, these systems enable dynamic and detailed investigation of plant and plant-microbial consortia including the manipulation of microbiome composition (including mutants), the monitoring of plant growth, root morphology, exudate composition, and microbial localization under controlled environmental conditions. We anticipate that these detailed protocols will serve as an important starting point for other researchers, ideally helping create standardized experimental systems for investigating plant-microbe interactions.

Ecosystem Fabrication EcoFAB Protocols for The Construction of Laboratory Ecosystems Designed to Study Plant-microbe Interactions

This article describes detailed protocols for ecosystem fabrication of devices (EcoFABs) that enable the studies of plants and plant-microbe interactions in highly controlled laboratory conditions.

بروتوكولات النظام الإيكولوجي تلفيق (اكوفاب) لتشييد مختبر النظم الإيكولوجية تهدف إلى دراسة التفاعلات بين الميكروبات والنبات

Beneficial plant-microbe interactions offer a sustainable biological solution with the potential to boost low-input food and bioenergy production. A ...

Laboratory and Field Protocol for Estimating Sheet Erosion Rates from Dendrogeomorphology

Sheet erosion is among the crucial drivers of soil degradation. Erosion is controlled by environmental factors and human activities, which often lead to severe environmental impacts. The understanding of sheet erosion is, consequently, a worldwide issue with implications for both environment and economies. However, the knowledge on how erosion evolves in space and time is still limited, as well as its effects on the environment. Below, we explain a new dendrogeomorphological protocol for deriving eroded soil thickness (Ex) by acquiring accurate microtopographic data using both terrestrial laser scanning (TLS) and microtopographic profile gauges. Additionally, standard dendrogeomorphic procedures, dependent on anatomical variations in root rings, are utilized to establish the timing of exposure. Both TLS and microtopographic profile gauges are used to obtain ground surface pro&#64257;les, from which Ex is estimated after the threshold distance (TD) is determined, i.e., the distance between the root and the sediment knickpoint, which allows de&#64257;ning the lowering of the ground surface caused by sheet erosion. For each profile, we measured the height between the topside of the root and a virtual plane tangential to the ground surface. In this way, we intended to avoid small-scale impacts of soil deformation, which may be due to pressures exerted by the root system, or by the arrangement of exposed roots. This may provoke small amounts of soil sedimentation or erosion depending on how they physically affect the surface runoff. We demonstrate that an adequate microtopographic characterization of exposed roots and their associated ground surface is very valuable to obtain accurate erosion rates. This finding could be utilized to develop the best management practices designed to eventually halt or perhaps, at least, lessen soil erosion, so that more sustainable management policies can be put into practice.

Characterizing erosion from dendrogeomorphology has usually focused on accurately finding the starting time of root exposure, by examining macroscopic or cell level changes caused by exposure. Here, we offer a detailed description of different novel techniques to obtain more precise erosion rates from highly accurate microtopographic data.

المختبر وبروتوكول الميدانية لتقدير معدلات تحات ورقة من ديندروجيومورفولوجي

Sheet erosion is among the crucial drivers of soil degradation. Erosion is controlled by environmental factors and human activities, which often lead to ...