Summary

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

Published: August 29, 2014
doi:

Summary

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.

Abstract

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.

Introduction

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’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 (γ) 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 γ 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 γ 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 γ14,17.

The methodology used in the present study for estimating γ 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 – mass spectrometry instrumentation used to determine the PCB congener concentrations must be capable of detecting and quantifying individual PCB congeners at relatively low concentrations.

Protocol

1. مختبر التجربة 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 للأسم…

Representative Results

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?…

Discussion

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…

Disclosures

The authors have nothing to disclose.

Acknowledgements

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.

Materials

Name  Company Catalog Number Comments
870-L fiberglass tanks Frigid Units RT-430-1
2,380-L fiberglass tanks Frigid Units RT-630-1
Tricaine methanesulfonate (Finquel) Argent Chemical Laboratories, Inc. C-FINQ-UE-100G Eugenol could also be used as an anesthetic.
Ashland chef knife Chicago Cutlery SKU 1106336
Cutting board Williams-Sonoma 3863586
Hobart verical mixer (40 quart) Hobart Corporation
1.9-L food processor Robot Coupe, Inc. RSI 2Y1 
Polyethylene bags (various sizes) Arcan Inc.
I-Chem jars I-Chem 220-0125
Top-load electronic balance Mettler Toledo Mettler PM 6000 
Sodium sulfate, anhydrous – granular EMD SX0760E-3
Glass extraction thimbles (45 mm x 130 mm) Wilmad-Lab Glass LG-7070-114
Teflon boiling chips Chemware 919120
Rapid Vap nitrogen sample concentrator Labconco 7910000
N-Vap nitrogen concentrator Organomation 112
Soxhlet extraction glassware (500 mL) Wilmad-Lab Glass  LG-6900-104
Hexane Burdick & Jackson  Cat. 211-4
Dichloromethane Burdick & Jackson  Cat. 300-4
Silica gel BDH Cat. BDH9004-1KG
Labl Line 5000 mult-unit extraction heater Lab Line Instruments
Agilent 5973 GC/MS with chemical ionization Agilent 5973N
Internal standard solution  Cambridge Isotope Laboratories EC-1410-1.2
PCB congener calibration standards Accustandard C-CSQ-SET
DB-XLB column (60m x 0.25mm, 0.25 micron) Agilent/ J&W 122-1262

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Cite This Article
Madenjian, C. P., Rediske, R. R., O’Keefe, J. P., David, S. R. Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout (Salvelinus namaycush) from Its Prey. J. Vis. Exp. (90), e51496, doi:10.3791/51496 (2014).

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