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 Provette <ol><li> Ottenere il pesce preda da alimentare per il pesce predatore durante l&#39;esperimento. Preferibilmente questi pesci preda dovrebbero essere acquisite in campo, congelati e conservati a circa -30 ° C. Considerate le operazioni di pesca commerciale come fonte potenziale per il pesce preda. </li><li> Introdurre il pesce predatore nei serbatoi di laboratorio da utilizzare per l&#39;esperimento. Fino al 15 predatore pesci sono stati introdotti in ciascuna delle vasche 870-L, e fino a 30 predatore pesci sono stati introdotti in ciascuna delle cisterne 2.380-L in studi precedenti 16,18. </li><li> Acclimatare il pesce predatore ad una dieta del pesce preda selezionata. Una volta acclimatati, il pesce predatore dovrebbe rimanere su questa dieta per 1-3 mesi prima di iniziare l&#39;esperimento. </li><li> Mettere da parte i campioni di pesce preda selezionando in modo casuale 10 a 20 campioni compositi dal lotto di pesce preda. Numero di pesce preda in un campione composito può variare da 3 a 100, a seconda delle dimensioni della predapesce. Ogni campione composito deve essere il doppio insaccato, congelato e conservato a circa -30 ° C. </li><li> Avviare l&#39;esperimento sacrificando 30 al 50% dei pesci in ciascuna delle vasche. <ol><li> Per eutanasia il pesce, mescolare 8 g di Finquel con 45 L di acqua in un grande contenitore di plastica e poi mettere il pesce nel contenitore con la soluzione Finquel. </li><li> Una volta eutanasia, inserire tutti i pesci sacrificato da un serbatoio in un sacchetto, poi doppio sacchetto, e conservare a circa -30 ° C fino al momento della lavorazione. </li><li> Pesare ciascuna del pesce rimanente in ciascuna delle cisterne, e registrare i pesi; un anestetico sarà probabilmente necessario per condurre la pesatura. </li><li> Per anestetizzare il pesce, mescolare 4,6 g di Finquel con 45 L di acqua in un grande contenitore di plastica, e poi mettere il pesce nel contenitore con la soluzione Finquel. </li><li> Attendere qualche minuto per l&#39;anestetico abbia effetto prima di pesare il pesce. </li></ol></li><li> Ogni giorno dell&#39;esperimento, scongelare unadeguata quantità di pesce preda, e tagliare il pesce preda in pezzi del peso di circa 1 a 5 g. Pesare la quantità di pesce preda ad essere messi in ciascuna delle vasche, poi rilasciare i pezzi di pesce preda in ogni serbatoio e permettere al pesce predatore circa 1 ora da sfamare. Quindi rimuovere tutto il cibo non mangiato, permettere al cibo di aria secca per circa 20 minuti, e poi pesare il cibo non consumato per ciascuna delle vasche. Registrare la quantità di cibo collocato nel serbatoio e la quantità di resti di cibo per ciascuno dei serbatoi ogni giorno. NOTA: Per l&#39;esperimento rappresentativo, trota di lago sono stati alimentati con tanto cibo quanto avrebbero consumare nel corso di un periodo di alimentazione ogni giorno 18. Tuttavia, il pesce predatore potrebbe anche essere collocato su razioni fisse 16,19. </li><li> Terminare l&#39;esperimento sacrificando tutti i restanti pesci predatori in ciascuno dei serbatoi. Per eutanasia il pesce, mescolare 8 g di Finquel con 45 L di acqua in un grande contenitore di plastica e poi mettere il pesce nel contenitore con la soluzione Finquel. Record tegli peso di ciascuno dei pesci sacrificato. Per ottenere risultati affidabili, l&#39;esperimento deve funzionare per almeno 100 giorni, preferibilmente per almeno 130 giorni. Mettere tutti i pesci da un serbatoio in un sacchetto, poi doppio sacchetto, e conservare a circa -30 ° C fino al momento della lavorazione. </li></ol> 2 Pesce Omogeneizzazione <ol><li> Selezionare un insieme di pesci predatori e / o compositi pesce preda per lo scongelamento. Lasciare i compositi scongelare parzialmente. Ogni composito può richiedere da 0,5 a 1 ora per omogeneizzare. </li><li> Utilizzando i frullatori appropriate dimensioni, omogenizzare ciascuno dei compositi. Per ogni composito, posizionare un campione (da 50 a 100 g), del omogenato in un barattolo pulito, acetone-sciacquati, ed etichettati. Poi tappare il vaso e conservare il vaso a circa -30 ° C fino al momento della lavorazione. </li><li> Lavare tutte le attrezzature utilizzate per omogeneizzare il pesce, e poi risciacquare bene con acqua distillata e metanolo, tra i campioni. </li></ol> 3 Estrazione <ol><li> Pesare 20,0 gdi pesce scongelato tessuto omogeneizzato in un bicchiere da 200 ml. </li><li> Aggiungere circa 40 g di solfato di sodio e mescolare bene con la spatola. </li><li> Aggiungere la soluzione picco surrogato contenente congeneri 30, 61, 161, e 166 Spike ad una concentrazione che produce una concentrazione finale di 20 ng / ml nell&#39;estratto. </li><li> Lasciare il campione asciugare a temperatura ambiente mescolando ogni 20 min. </li><li> Lasciare che il campione raggiunga una consistenza di sabbia asciutta, a questo punto il campione è pronto per l&#39;estrazione. </li><li> Sistemare il dispositivo di estrazione Soxhlet con un pallone da 500 ml contenente chip Teflon bollire, Soxhlet, e condensatore. </li><li> Aggiungere il composto di pesce essiccato in un ditale di vetro con fondo a disco grossa sinterizzato o carta ditale. </li><li> Aggiungere 150 ml di esano 50% e il 50% diclorometano nel becher usato per il campione e mescolare mentre raschiando le pareti del becher con una spatola. </li><li> Trasferire il solvente per la parte superiore del Soxhlet con il pallone attaccato e permettono di scorrere le Soxhlet e inal pallone. </li><li> Ripetere l&#39;operazione una seconda volta con 150 ml di nuovo. </li><li> Inserire il Soxhlet con la beuta adattata sull&#39;elemento di riscaldamento e collegare il condensatore. </li><li> Accendere l&#39;elemento riscaldante e portare il solvente a lenta ebollizione, poi estrarre per un minimo di 16 ore assicurandosi che l&#39;acqua fredda viene fornita ai condensatori. </li><li> Dopo aver lasciato il solvente raffreddare, controllare per vedere se uno qualsiasi dei flaconi campione contengono acqua. Per i flaconi contenenti acqua, aggiungere solfato di sodio e agitare fino a quando l&#39;acqua viene assorbita dal solfato di sodio. </li><li> Concentrare il campione utilizzando un campione concentratore azoto o un Kaderna danese (KD) installazione cristalleria con un bagno di acqua calda. </li><li> Lasciare il campione evaporare a un volume di meno di 2 ml, e quindi portare ad un volume finale di 5 ml utilizzando piccoli lavaggi di esano per trasferire il campione dalla vetreria utilizzata in un matraccio tarato da 5 ml. </li><li> Trasferimento a 10 ml flacone e l&#39;etichetta con le informazioni del campione. </li></ol><ol><li> Preparare gel di silice acidificato con l&#39;aggiunta di 44 g di acido solforico concentrato a 100 g di gel di silice attivato. </li><li> Aggiungere 10 g di gel di silice acidificato in una piccola colonna cromatografica contenente un piccolo tampone di lana di vetro nella parte inferiore. </li><li> Aggiungere 1 ml di estratto del campione alla colonna dopo il pre-pulizia della colonna con 10 ml di esano. </li><li> Eluire la colonna con 20 ml di esano e raccogliere in provetta conica da 20 ml. </li><li> Posizionare il tubo di vetro sull&#39;apparato evaporatore azoto (N-Vap) sotto flusso di azoto e immerso in acqua calda. </li><li> Evaporare a meno di 1 ml ma non a secchezza. </li><li> Rimuovere dal N-Vap e trasferimento in 1 ml matraccio con piccoli lavaggi di esano. </li><li> Trasferire in un flacone da 1,8 ml autocampionatore etichettati con informazioni sui campioni. </li><li> Spike 4 ml di standard interno nel flaconcino. Il campione è ora pronto per l&#39;analisi. </li></ol> 5. analeYsis mediante gascromatografia - spettrometria di massa Utilizzando Negativo ionizzazione chimica <ol><li> Utilizzare gli standard per calibrare lo strumento: le norme siano disponibili in miscele costituite da gruppi di congeneri ben separati. Miscele 1-5 composto da quasi tutti i congeneri presenti in Aroclor 1016, 1221, 1232, 1242, 1248, 1254, e 1260 Mix 1 è usato come un mix di calibrazione multi-livello, e la linearità del sistema è confermata da preparare almeno cinque livelli di taratura a concentrazioni comprese tra 2 e 100 ng / ml. Miscele 2-5 sono usati come punto di taratura singoli per ogni composto. </li><li> Impostare la cromatografia - sistema di spettrometria di massa in modalità di ionizzazione chimica negativa con idrogeno come gas di trasporto (1 ml / min) e il metano come gas reagente. </li><li> Utilizzare un-silice fusa, colonna capillare (60 m × 0,25 millimetri di diametro interno) rivestito con DB-XLB a spessore del film di 0,25 micron per la separazione. Programma temperatura forno 60-212 ° C a 25 ° C / min, poi a 260 ° C a 1 ° C / min, e poi a 280 ° C a 4 ° C / min, con un tempo di mantenimento finale di 4 min. Temperature dell&#39;iniettore e linea di trasferimento devono essere impostati a 280 ° C. Iniettare 1 a 2 ml di campione utilizzando la modalità di iniezione splitless. </li><li> Analizzare tutti gli standard ed i campioni con il metodo dello standard interno con 13 C-marcato decachlorobiphenyl. </li><li> Eseguire un controllo sulla taratura iniziale mediante l&#39;esecuzione di un secondo livello di origine e Aroclors 1242 e il 1260, e poi confrontare i valori previsti per i congeneri Aroclor con gli importi osservati di questa procedura di controllo. </li><li> Una volta che la procedura di calibrazione iniziale è stata compiuta con successo, un&#39;analisi completa di tutti i campioni. Eseguire un controllo di calibrazione ogni dieci campioni, utilizzando una delle miscele di taratura dalla calibrazione iniziale. </li></ol> 6 Calcolo del Net trofico efficienza di trasferimento <ol><li> Calcola efficienza di trasferimento trofico rete, γ, per ogni combinazione oserbatoio F e PCB composto utilizzando la seguente equazione: <img alt="Equazione 1" fo:content-width="2in" src="/files/ftp_upload/51496/51496eq1.jpg" /> , Dove [PCB f] è la concentrazione media di PCB congenere dei pesci predatori nel serbatoio alla fine dell&#39;esperimento, W f è il peso medio dei pesci predatori nel serbatoio alla fine dell&#39;esperimento, [PCB i] è la concentrazione media di PCB congenere dei pesci predatori nel serbatoio all&#39;inizio dell&#39;esperimento, W i è il peso medio dei pesci predatori all&#39;inizio dell&#39;esperimento, e la quantità di PCB congenere ingerito si riferisce al peso del congenere PCB ingerito, in media, da ogni trota lago nel serbatoio durante il corso dell&#39;esperimento. </li><li> Calcolare il denominatore nell&#39;equazione di cui sopra moltiplicando la concentrazione media del congenere PCB nei compositi pesce preda per l&#39;importo medio (peso) del pesce preda mangiato al pesce predatore nel dur serbatoiozione l&#39;intero corso dell&#39;esperimento. </li></ol>

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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>

Per le stime più accurate di γ, lo sperimentatore deve essere in grado di monitorare con precisione sia la quantità di cibo posto in ciascuno dei serbatoi e la quantità di resti di cibo in ciascuno dei serbatoi durante il corso dell&#39;esperimento. Per fare questo, lo sperimentatore deve essere in grado di rimuovere tutto il cibo non consumato dai serbatoi e determinare con precisione il suo peso. Oltre al monitoraggio accurato del cibo effettivamente consumato dai pesci predatori, stima accurata di γ può dipende...

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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			<td style="width:167px;">Comments</td>
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			<td height="21" style="height:21px;width:259px;">870-L fiberglass tanks</td>
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			<td height="68" style="height:68px;width:259px;">Tricaine methanesulfonate (Finquel)</td>
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			<td style="width:167px;">Eugenol could also be used as an anesthetic.</td>
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			<td style="width:119px;">3863586</td>
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			<td style="width:119px;">RSI 2Y1&#160;</td>
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			<td style="width:119px;">220-0125</td>
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			<td height="20" style="height:20px;width:259px;">Top-load electronic balance</td>
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			<td height="21" style="height:21px;width:259px;">Sodium sulfate, anhydrous - granular</td>
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			<td style="width:119px;">SX0760E-3</td>
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			<td style="width:87px;">Wilmad-Lab Glass</td>
			<td style="width:119px;">LG-7070-114</td>
			<td></td>
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			<td height="21" style="height:21px;width:259px;">Teflon boiling chips</td>
			<td style="width:87px;">Chemware</td>
			<td style="width:119px;">919120</td>
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			<td height="21" style="height:21px;width:259px;">Rapid Vap nitrogen sample concentrator</td>
			<td style="width:87px;">Labconco</td>
			<td style="width:119px;">7910000</td>
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			<td height="21" style="height:21px;width:259px;">N-Vap nitrogen concentrator</td>
			<td style="width:87px;">Organomation</td>
			<td style="width:119px;">112</td>
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			<td height="35" style="height:35px;width:259px;">Soxhlet extraction glassware (500 mL)</td>
			<td style="width:87px;">Wilmad-Lab Glass</td>
			<td style="width:119px;">&#160;LG-6900-104</td>
			<td></td>
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		<tr height="35">
			<td height="35" style="height:35px;width:259px;">Hexane</td>
			<td style="width:87px;">Burdick &#38; Jackson&#160;</td>
			<td style="width:119px;">Cat. 211-4</td>
			<td></td>
		</tr>
		<tr height="35">
			<td height="35" style="height:35px;width:259px;">Dichloromethane</td>
			<td style="width:87px;">Burdick &#38; Jackson&#160;</td>
			<td style="width:119px;">Cat. 300-4</td>
			<td></td>
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			<td height="21" style="height:21px;width:259px;">Silica gel</td>
			<td style="width:87px;">BDH</td>
			<td style="width:119px;">Cat. BDH9004-1KG</td>
			<td></td>
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		<tr height="35">
			<td height="35" style="height:35px;width:259px;">Labl Line 5000 mult-unit extraction heater</td>
			<td style="width:87px;">Lab Line Instruments</td>
			<td style="width:119px;"></td>
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			<td height="35" style="height:35px;width:259px;">Agilent 5973 GC/MS with chemical ionization</td>
			<td style="width:87px;">Agilent</td>
			<td style="width:119px;">5973N</td>
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			<td height="52" style="height:52px;width:259px;">Internal standard solution&#160;</td>
			<td style="width:87px;">Cambridge Isotope Laboratories</td>
			<td style="width:119px;">EC-1410-1.2</td>
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			<td height="21" style="height:21px;width:259px;">PCB congener calibration standards</td>
			<td style="width:87px;">Accustandard</td>
			<td style="width:119px;">C-CSQ-SET</td>
			<td></td>
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			<td height="21" style="height:21px;width:259px;">DB-XLB column (60m x 0.25mm, 0.25 micron)</td>
			<td style="width:87px;">Agilent/ J&#38;W</td>
			<td style="width:119px;">122-1262</td>
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laboratory estimation of net trophic transfer efficiencies of pcb congeners to lake trout (salvelinus namaycush) from its prey

Una tecnica per la stima laboratorio di efficienza di rete trofica trasferimento (γ) dei bifenili policlorurati (PCB) congeneri di pesce piscivori dalla loro preda è qui descritta. Nel corso di un esperimento di laboratorio 135 giorni, ci siamo nutriti aringa (Coregonus hoyi), che era stato catturato nel lago Michigan a Trout Lake (Salvelinus namaycush) tenuti in otto serbatoi di laboratorio. Bloater è una preda naturale per la trota lago. In quattro dei serbatoi, una portata relativamente elevato è stato utilizzato per garantire relativamente elevata attività della trota di lago, mentre una bassa portata è stata utilizzata nelle altre quattro vasche, consentendo bassa attività trota di lago. Su una base serbatoio-by-tank, la quantità di cibo mangiato da trota lago ogni giorno dell&#39;esperimento è stato registrato. Ogni trota di lago è stato pesato all&#39;inizio e alla fine dell&#39;esperimento. Quattro a nove trota lago da ciascuna delle otto serbatoi sono stati sacrificati all&#39;inizio dell&#39;esperimento, e tutti trota lago restante 10 in ciascuno dei serbatoi erano euthanzata alla fine dell&#39;esperimento. Abbiamo determinato le concentrazioni di 75 congeneri di PCB nel trota lago all&#39;inizio dell&#39;esperimento, la trota lago alla fine dell&#39;esperimento, e in bloaters nutriti alla trota lago durante l&#39;esperimento. Sulla base di queste misurazioni, γ è stata calcolata per ciascuno dei 75 congeneri dei PCB in ciascuna delle otto serbatoi. Significa γ è stata calcolata per ciascuno dei 75 congeneri di PCB per trota di lago sia attiva che inattiva. Poiché l&#39;esperimento è stato replicato in otto serbatoi, l&#39;errore standard sulla media γ potrebbe essere stimato. I risultati di questo tipo di esperimento sono utili nei modelli di valutazione del rischio per predire il futuro rischio per l&#39;uomo e la fauna selvatica che mangiano pesce contaminato sotto vari scenari di contaminazione ambientale.

Trout Lake ha mostrato una notevole quantità di crescita durante l&#39;esperimento, come la trota lago iniziali significano pesi variava 694-907 g, mentre le trote lacustri finali il peso medio variava da 853 a 1566 g (Tabella 1). La quantità media di cibo consumato da una trota lago durante il corso dell&#39;esperimento 135 giorni variava da 641 a 2.649 g. Concentrazioni di PCB congeneri media nella trota lago aumentato durante l&#39;esperimento, le concentrazioni di congeneri PCB media variava 0,01-...

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

Una tecnica per la stima laboratorio di rendimento netto trasferimento trofico dei bifenili policlorurati (PCB) congeneri di pesce piscivori dalla loro preda è presentato. Per massimizzare l&#39;applicabilità dei risultati di laboratorio al campo, il pesce piscivori dovrebbe essere alimentato pesce preda che sono tipicamente consumati in campo.

Laboratorio Stima di Net trofiche trasferimento incrementi di efficienza di congeneri di PCB a Lake Trout (<em&gt; Salvelinus namaycush</em&gt;) Dalla sua preda

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

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Environment

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.  Una tecnica per la stima laboratorio di rendimento netto trasferimento trofico dei bifenili policlorurati (PCB) congeneri di pesce piscivori dalla loro preda è presentato. Per massimizzare l'applicabilità dei risultati di laboratorio al campo, il pesce piscivori dovrebbe essere alimentato pesce preda che sono tipicamente consumati in campo. 

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.

Laboratorio-determinato Fosforo Flux dal lago di sedimenti come misura di fosforo interno 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) ...

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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.

Un pesce-alimentare Laboratorio Bioassay per valutare l&#39;attività di antipredatory Secondary metaboliti dai tessuti di organismi marini

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.

Automated Gel Selection Size per migliorare la qualità delle Biblioteche di sequenziamento di nuova generazione Preparato da campioni di acqua ambientale

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.

Rimozione di Oligoelementi per Cupric nanoparticelle di ossido di uranio da<em&gt; In Situ</em&gt; Recupero Bleed Acqua e il suo effetto sulla vitalità cellulare

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.

Simulazione Laboratorio di ferro (II) ricchi di Precambriano Marine Upwelling sistema per esplorare la crescita di batteri fotosintetici

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.

Sviluppo di<em&gt; Metarhizium anisopliae</em&gt; Come micosintetizzatore: dall&#39;isolamento al campo

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.

Procedure di fumigazione di laboratorio per il controllo dei parassiti con Gas di ossido di azoto

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.

Aderenza dei batteri per piantare superfici misurate in laboratorio

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.

Protocolli di fabbricazione (EcoFAB) di ecosistema per la costruzione degli ecosistemi di laboratorio progettato per studiare le interazioni piante-microrganismi

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.

Laboratorio e campo protocollo per la stima di tassi di erosione del foglio da Dendrogeomorphology

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