ASTM_E_1201_-_87_2012.pdf

Designation:E120187(Reapproved 2012)Standard Practice forSampling Zooplankton with Conical Tow Nets1This standard is issued under the fixed designation E1201;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the procedure for obtaining quali-tative samples of a zooplankton community by use of conicaltow nets.Nets will collect most zooplankton,but some formswill avoid nets.1.2 This standard does not purport to address all of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Summary of Practice2.1 The net is attached to a tow line and towed at the desireddepth,using a cable depressor if necessary.After a specifieddistance or period of time,the net is retrieved and the capturedzooplankton are removed from the net.The zooplankton maybe preserved as dictated by the objective of the study.3.Significance and Use3.1 The advantages of using conical tow nets are as follows:3.1.1 They are relatively inexpensive and highly versatile ina variety of inland,estuarine,coastal,and marine waters.3.1.2 They can be used from a small or large powered boatwith a minimum of auxiliary equipment.3.1.3 They can be used to collect qualitative samples andsemiquantitative samples when fitted with a flowmeter andeven better samples when fitted with a companion meter on theoutside of the hoop to monitor filtering efficiency.3.2 The disadvantages of conical tow nets are as follows:3.2.1 When equipped with a flowmeter they require fre-quent maintenance including calibration and,in some types,lubrication.3.2.2 They are effective only where drawn through a streamof water having considerable thickness.They are not suitablefor collecting samples from a small or restricted region.3.2.3 They are not suitable for collecting in very shallowwater.3.2.4 They are clogged by grass beds,coelenterates,andfilamentous algae.3.2.5 When used with a flowmeter,they collect only quali-tative samples,or semiquantitative samples.3.2.6 When sampling discrete depths using a horizontal tow,the sample can be contaminated from other depths during thedeployment and retrieval of the samples if opening and closingdevices are not used.3.3 There are several special considerations that shall beobserved when using conical tow nets.They are:3.3.1 Conical tow net samplers are designed to be towed atspeeds less than three knots;however,greater speeds have beenused for the larger nets with a concomitant increase in capture.23.3.2 A conical tow net 0.5 m in diameter or larger shall beused to reduce avoidance by organisms.23.3.3 The nets shall be washed frequently and inspected forpin-size holes,tears,net deterioration,and other anomalies.3.3.4 Nets should be allowed to dry while suspended fulllength in air and in subdued light prior to storage.3.3.5 Lower catches per sample may result when collectionsare made during the day.These are particularly noted in thelarger zooplanktons.4.Procedure4.1 The conical net samplers are designed to be towed atspeeds of approximately three knots.However,greater speedsof up to five knots have been used with a concomitant increasein organisms captured per unit volume of water filter.34.2 Select the bridle arrangement carefully.The most com-mon arrangement is a three-point attached bridle resulting inconsiderable net avoidance.4An attachment procedure result-ing in no obstruction of the mouth is preferred and can beaccomplished by using a simple gimbaled hoop arrangement,with a depressor at the bottom of the tow line.4.3 Proper placement of the flowmeter within the conicalnet mouth is crucial for sample quantification.In order to1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.24 on Water Microbiology.Current edition approved Dec.1,2012.Published December 2012.Originallyapproved in 1987.Last previous edition approved in 2004 as E1201 87(2004).DOI:10.1520/E1201-87R12.2Schwoerbel,J.,Methods of Hydrobiology(Freshwater Biology),PergamonPress,New York,NY,1968,p.200.3Clutter,R.I.,andAnraku,M.,“Avoidance of Samplers,”UNESCO Monographon Oceanographic Methodology,No.2,1968,pp.5776.4UNESCO,“Zooplankton Sampling,”Monographs on OceanographicMethodology,Unipub,Inc.,New York,NY,1968,p.174.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 obtain an average velocity of water within the net,place themeter at a point one-third of the diameter of the mouth of thenet.4.4 The type and mesh size of the netting used is veryimportant because the most common type of net available is asimple,in