ASTM_E_2122_-_02_2013.pdf

Designation:E212202(Reapproved 2013)Standard Guide forConducting In-situ Field Bioassays With Caged Bivalves1This standard is issued under the fixed designation E2122;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 guide describes procedures for conducting con-trolled experiments with caged bivalves under field conditions.The purpose of this approach is to facilitate the simultaneouscollection of field data to help characterize chemical exposureand associated biological effects in the same organism underenvironmentally realistic conditions.This approach of charac-terizing exposure and effects is consistent with the US EPAecological risk assessment paradigm.Bivalves are useful testorganisms for in-situ field bioassays because they(1)concen-trate and integrate chemicals in their tissues and have a morelimited ability to metabolize most chemicals than other species,(2)exhibit measurable sublethal effects associated with expo-sure to those chemicals,(3)provide paired tissue chemistry andresponse data which can be extrapolated to other species andtrophic levels,(4)provide tissue chemistry data which can beused to estimate chemical exposure from water or sediment,and(5)facilitate controlled experimentation in the field withlarge sample sizes because they are easy to collect,cage,andmeasure(1,2)2.The experimental control afforded by thisapproach can be used to place a large number of animals of aknown size distribution in specific areas of concern to quantifyexposure and effects over space and time within a clearlydefined exposure period.Chemical exposure can be estimatedby measuring the concentration of chemicals in water,sediment,or bivalve tissues,and effects can be estimated withsurvival,growth,and other sublethal end points(3).Althougha number of assessments have been conducted using bivalvesto characterize exposure by measuring tissue chemistry orassociated biological effects,relatively few assessments havebeen conducted to characterize both exposure and biologicaleffects simultaneously(2,4,5).This guide is specificallydesigned to help minimize the variability in tissue chemistryand response measurements by using a practical uniform sizerange and compartmentalized cages for multiple measurementson the same individuals.1.2 The test is referred to as a field bioassay because it isconducted in the field and because it includes an element ofrelative chemical potency to satisfy the bioassay definition.Relative potency is established by comparing tissue concen-trations with effects levels for various chemicals with toxicityand bioaccumulation end points(6,7,8,9,10)even thoughthere may be more uncertainty associated with effects mea-surements in field studies.Various pathways of exposure canbe evaluated because filter-feeding and deposit-feeding are theprimary feeding strategies for bivalves.Filter-feeding bivalvesmay be best suited to evaluate the bioavailability and associ-ated effects of chemicals in the water column(that is,dissolvedand suspended particulates);deposit-feeding bivalves may bebest suited to evaluate chemicals associated with sediments(11,12).It may be difficult to demonstrate pathways ofexposure under field conditions,particularly since filter-feeding bivalves can ingest suspended sediment and facultativedeposit-feeding bivalves can switch between filter-and depositfeeding over relatively small temporal scales.Filter-feedingbivalves caged within 1 m of bottom sediment have also beenused effectively in sediment assessments from depths of 10 to650 m(5,13,14).Caged bivalve studies have also beenconducted in the intertidal zone(15).The field testing proce-dures described here are useful for testing most bivalvesalthough modifications may be necessary for a particularspecies.1.3 These field testing procedures with caged bivalves areapplicable to the environmental evaluation of water andsediment in marine,estuarine,and freshwater environmentswith almost any combination of chemicals,and methods arebeing developed to help interpret the environmental signifi-cance of accumulated chemicals(6,7,9,16,17).Theseprocedures could be regarded as a guide to an exposure systemto assess chemical bioavailability and toxicity under natural,site-specific conditions,where any clinical measurements arepossible.1.4 Tissue chemistry results from short-and long-termexposures can be reported in terms of concentrations ofchemicals in bivalve tissues(for example,g/g),amount(thatis,weight or mass)of chemical per animal(for example,g/animal),rate of uptake,or bioaccumulation factor(BAF,theratio between the concentration of a chemical in bivalve tissuesand the concentration in the external environment,including1This guide is under the jurisdiction ofASTM Committee E50 on En