Water quality - Guidance on methods for sampling invertebrates in the hyporheic zone of rivers

This document provides guidance on methods for sampling invertebrates in the hyporheic zone of wadable rivers. It describes each method, including details of the equipment involved and its use in the field. Guidance is given on developing a sampling strategy and selecting an appropriate survey technique for the purpose of investigation. Benthic macroinvertebrate sampling is covered elsewhere by other published standards (see bibliography). Selected literature with references in support of this document is given in the bibliography.

Wasserbeschaffenheit - Anleitung für die Probenahme von Invertebraten (Wirbellosen) in der hyporheischen Zone von Flüssen

Qualité de l'eau - Lignes directrices relatives aux méthodes d'échantillonnage des invertébrés dans la zone hyporhéique de rivières

Le présent document fournit des lignes directrices relatives à l’échantillonnage des invertébrés dans la zone hyporhéique de rivières prospectables à pied. Il décrit chaque méthode, y compris les détails du matériel nécessaire et son utilisation sur le terrain. Des lignes directrices sont données sur l’élaboration d’une stratégie d’échantillonnage et la sélection d’une technique de sondage appropriée pour l’étude. L’échantillonnage de macro-invertébrés benthiques est traité dans d’autres normes publiées (voir la bibliographie). La littérature choisie dont les références étayent le présent document est indiquée dans la bibliographie.

Kakovost vode - Navodilo za metode vzorčenja nevretenčarjev v hiporeični coni rek

Ta dokument podaja navodila za metode vzorčenja nevretenčarjev v hiporhaičnih conah prebrodljivih rek. Opisuje vsako metodo, vključno s podrobnostmi o vključeni opremi in njeni uporabi na terenu. Podana so navodila o razvijanju strategije vzorčenja in izbiranju ustrezne tehnike raziskovanja za namen preiskave. Vzorčenje bentoških makronevretenčarjev je obravnavano v drugih objavljenih standardih (glej bibliografijo). Izbrana literatura s sklici v podporo temu dokumentu je podana v bibliografiji.

General Information

Status
Published
Public Enquiry End Date
05-Nov-2014
Publication Date
09-Nov-2016
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
07-Nov-2016
Due Date
12-Jan-2017
Completion Date
10-Nov-2016

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.UHNWasserbeschaffenheit - Anleitung für die Probenahme von Invertebraten (Wirbellosen) in der hyporheischen Zone von FlüssenQualité de l'eau - Lignes directrices relatives aux méthodes d'échantillonnage des invertébrés dans la zone hyporhéique de rivièresWater quality - Guidance on methods for sampling invertebrates in the hyporheic zone of rivers13.060.70Preiskava bioloških lastnosti vodeExamination of biological properties of water13.060.10Voda iz naravnih virovWater of natural resourcesICS:Ta slovenski standard je istoveten z:EN 16772:2016SIST EN 16772:2016en,fr,de01-december-2016SIST EN 16772:2016SLOVENSKI

STANDARD
SIST EN 16772:2016
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 16772
April
t r s x ICS
s uä r x rä y r English Version

Water quality æ Guidance on methods for sampling invertebrates in the hyporheic zone of rivers Qualité de l 5eau æ Lignes directrices relatives aux méthodes d 5échantillonnage des invertébrés dans la zone hyporhéique des rivières

Wasserbeschaffenheit æ Anleitung zu Methoden für die hyporheischen Zone von Flüssen This European Standard was approved by CEN on

t r February
t r s xä

egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä

translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä

CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey and United Kingdomä

EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels

t r s x CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN

s x y y tã t r s x ESIST EN 16772:2016

EN 16772:2016 (E) 2 Contents Page European foreword ....................................................................................................................................................... 3 Introduction .................................................................................................................................................................... 4 1 Scope .................................................................................................................................................................... 6 2 Terms and definitions ................................................................................................................................... 6 3 Survey objectives ............................................................................................................................................ 8 4 Sampling strategy............................................................................................................................................ 9 5 Sampling methods ....................................................................................................................................... 10 5.1 General ............................................................................................................................................................. 10 5.2 Karaman-Chappuis pit ............................................................................................................................... 10 5.2.1 Description and operation ........................................................................................................................ 10 5.2.2 Species sampled ............................................................................................................................................ 11 5.2.3 Environmental variables ........................................................................................................................... 11 5.3 Bou-Rouch pump .......................................................................................................................................... 11 5.3.1 Description and operation ........................................................................................................................ 11 5.3.2 Species sampled ............................................................................................................................................ 12 5.3.3 Environmental variables ........................................................................................................................... 13 5.4 Vacuum pump ................................................................................................................................................ 13 5.4.1 Description and operation ........................................................................................................................ 13 5.4.2 Species sampled ............................................................................................................................................ 15 5.4.3 Environmental variables ........................................................................................................................... 15 5.5 Standpipe trap ............................................................................................................................................... 15 5.5.1 Description and operation ........................................................................................................................ 15 5.5.2 Species sampled ............................................................................................................................................ 15 5.5.3 Environmental variables ........................................................................................................................... 15 5.6 Williams corer ............................................................................................................................................... 16 5.6.1 Description and operation ........................................................................................................................ 16 5.6.2 Species sampled ............................................................................................................................................ 16 5.6.3 Environmental variables ........................................................................................................................... 16 5.7 Colonization devices ................................................................................................................................... 17 5.7.1 Description and operation ........................................................................................................................ 17 5.7.2 Species sampled ............................................................................................................................................ 19 5.7.3 Environmental variables ........................................................................................................................... 19 5.8 Freeze coring ................................................................................................................................................. 19 5.8.1 Description and operation ........................................................................................................................ 19 5.8.2 Species sampled ............................................................................................................................................ 20 5.8.3 Environmental variables ........................................................................................................................... 20 6 Sample processing ....................................................................................................................................... 20 Annex A (informative)

Examples of sampling strategies for three different types of investigation .................................................................................................................................................. 21 A.1 Case Study 1 – Assessing regional biodiversity and species richness ....................................... 21 A.2 Case Study 2 – Assessing impacts on fish spawning sites .............................................................. 21 A.3 Case Study 3 – Assessing the impacts of pollution ........................................................................... 21 Bibliography ................................................................................................................................................................. 22

SIST EN 16772:2016

EN 16772:2016 (E) 3 European foreword This document (EN 16772:2016) has been prepared by Technical Committee CEN/TC 230 “Water analysis”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2016, and conflicting national standards shall be withdrawn at the latest by October 2016. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 16772:2016

EN 16772:2016 (E) 4 Introduction WARNING — Safety issues are paramount when surveying rivers. Surveyors should conform to EU and national Health and Safety legislation, and any additional guidelines appropriate for working in or near rivers. The term “hyporheic” is derived from two Greek words: hypo (under) and rheos (flow), and was first used by Orghidan in 1959 [1] to delineate the area of saturated subsurface sediments beneath and lateral to the wetted channel that contains a mix of surface water and groundwater. In the past 50 years, scientific understanding of the hyporheic zone has improved [2] and the term has been modified and expanded by hydrologists, hydrogeologists, chemists and biologists to reflect the importance of: — the upwelling and downwelling of water into and out of the stream bed and the mixing ratio of surface water and groundwater; — the nature and rate of biogeochemical processes resulting from upwelling of interstitial water or downwelling of surface water; — the ecotonal nature of the hyporheic zone which provides important habitat for benthic taxa, specialist hyporheic organisms and groundwater fauna, including macroinvertebrates, meiofauna and microorganisms. Meiofauna includes microcrustaceans, rotifers and nematodes as well early instars of many aquatic insects. In this standard the hyporheic zone is defined as the spatio-temporally dynamic ecotone between the surficial benthic substrate and the underlying aquifer. Within the hyporheic zone, water, solutes and biota are exchanged with the stream above, the groundwater below and the saturated sediments lateral to the channel. The term “hyporheic zone” is applied to the physical habitat while the term “hyporheos” coined by Williams and Hynes in 1974 [3] is used to describe the faunal community inhabiting it. Over the past few decades, the importance of the hyporheic zone has been increasingly recognized, with the vertical dimension added to spatial concepts of lateral and longitudinal connectivity. Together with the temporal dimension this has created a four-dimensional understanding of river ecosystems [4, 5, 6]. As the hyporheic zone is an ecotone between surface water and groundwater, abiotic conditions may reflect a transition between the two. Table 1 provides a general comparison of the physical characteristics of each environment. Table 1 — Physical characteristics of typical groundwater and hyporheic environments compared with surface waters Physical characteristic Groundwater Hyporheic Light Constant darkness Constant darkness Current velocity Much lower Lower Annual and daily temperature range Much smaller Smaller Substrate stability Much higher Higher Approaches to river conservation and management recognize the need for a better understanding of the interactions between surface water and groundwater when undertaking investigations in the field. As the ecotone between the two, the hyporheic zone plays a vital part in ecosystem functioning in many rivers, including a critical role in the flow of energy, cycling of nutrients and organic compounds, as well as pollution attenuation. The hyporheic zone contributes to overall river biodiversity. It also provides a nursery for young life-stages of some fish and invertebrates and a potential refuge for benthos during adverse environmental conditions, such as flooding, low flows, chemical pollution, stream-bed drying or freezing. The hyporheic zone may therefore enhance the recovery of the benthic community following disturbance. SIST EN 16772:2016

EN 16772:2016 (E) 5 An increased interest in the hyporheic zone has resulted, in part, from international legislation, such as EC directives: the Habitats Directive [7], the Water Framework Directive [8], the Groundwater Directive [9] and the Nitrates Directive [10]. Although investigations into the hyporheic zone are not explicit within these directives, they do require national regulatory authorities to adopt a more integrated approach to the management of river catchments as a whole. Consequently, an understanding of the hyporheic zone, including its functions and the potential threats to these, is vital in order to comply fully with the requirements of these directives. Investigations of the hyporheic zone may also be needed more generally for catchment management, river restoration, site-based investigations or for research. Consequently, the purpose of any study should be carefully considered when selecting the most appropriate method for sampling the hyporheos, especially if the collection of water quality and associated sediment data is also required. In addition, the methods described in this standard may require modification to reflect local conditions. SIST EN 16772:2016

EN 16772:2016 (E) 6 1 Scope This European Standard provides guidance on methods for sampling invertebrates in the hyporheic zone of wadable rivers. It describes each method, including details of the equipment involved and its use in the field. Guidance is given on developing a sampling strategy and selecting an appropriate survey technique for the purpose of investigation. NOTE Benthic macroinvertebrate sampling is covered by other published standards (see Bibliography). Selected literature with references in support of this document is given in the Bibliography. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 aquifer underground zone of water-bearing permeable rock or unconsolidated material from which groundwater can be extracted 2.2 benthic relating to the surface substrate 2.3 benthos community inhabiting the surface substrate of rivers 2.4 biofilm coating on a substrate composed of microorganisms, extra-cellular polysaccharides, other materials that organisms produce, and particles trapped or precipitated within the matrix 2.5 biomass total mass of living organisms per unit surface area or volume 2.6 catchment basin area from which precipitation or groundwater will collect and contribute to the flow of a specific river 2.7 diversity taxonomic richness of a community and the distribution of individuals across taxa 2.8 downwelling movement of water in a downward direction, typically from the surface stream to the hyporheic zone or groundwater 2.9 ecotone transition area between two adjacent ecosystems SIST EN 16772:2016

EN 16772:2016 (E) 7 2.10 exposed river sediments particles, typically comprising cobbles, gravel, sand and silt, deposited by flowing water but exposed as water levels fall 2.11 groundwater water that is within the saturated zone below the water table 2.12 hyporheic flow flow of water through the hyporheic zone 2.13 hyporheic zone spatio-temporally dynamic ecotone between the surficial benthic substrate and the underlying aquifer 2.14 hyporheos faunal community inhabiting the hyporheic zone 2.15 interstitial referring to the spaces between substrate particles 2.16 macroinvertebrate invertebrate that is easily visible without magnification (0,5 mm) [SOURCE: EN ISO 10870:2012, 2.8] 2.17 meiofauna invertebrates that pass through a 500-µm or 1-mm sieve but are retained on a 45-µm- or 63-µm sieve 2.18 permeability capacity of a porous medium, either rock or unconsolidated material, to transmit water 2.19 pool habitat feature characterized by distinctly deeper parts of the channel that are usually no longer than one to three times the channel’s bankfull width, and where the hollowed river bed profiles are sustained by scouring [SOURCE: EN 14614:2004, 2.24] 2.20 porosity proportion of a given volume of rock or unconsolidated material that is occupied by pores SIST EN 16772:2016

EN 16772:2016 (E) 8 2.21 reach major sub-division of a river, defined by physical, hydrological, and chemical character that distinguishes it from other parts of the river system upstream and downstream [SOURCE: EN 14614:2004, 2.25] 2.22 riffle fast-flowing shallow water with distinctly broken or disturbed surface over gravel/pebble or cobble substrate [SOURCE: EN 14614:2004, 2.28] 2.23 riparian zone area of land adjoining a river channel (including the river bank) capable of directly influencing the condition of the aquatic ecosystem (e.g. by shading and leaf litter input) [SOURCE: EN 14614:2004, 2.29, modified — the NOTE was not adopted] 2.24 stream ordering methods for classifying rivers and streams related to the complexity of the drainage basin, generally with progressively higher order numbers usually assigned to streams with greater discharge lower down the catchment [SOURCE: EN 14614:2004, 2.37] 2.25 substrate material making up the bed of a river [SOURCE: EN 14614:2004, 2.40] 2.26 upwelling movement of water in an upward direction, typically from the groundwater or hyporheic zone to the surface stream 3 Survey objectives The objectives of the survey should be clearly defined before selecting which method to use for sampling the hyporheic zone, because the suitability of each method varies according to the purpose of study. Table 2 summarizes each sampling method according to its suitability for particular objectives. This includes consideration of: — attributes and variations in hyporheic fauna, substrate and the interstitial environment; — whether the method can be applied instream and/or in the riparian zone; — whether data collected are fully quantitative or semi-quantitative. All methods can be used to describe diversity, taxon richness, abundance and biomass, recognizing their known limitations. SIST EN 16772:2016

EN 16772:2016 (E) 9 Table 2 — Overview of sampling methods described in this standard and their suitability for particular surveys

Karaman-Chappuis pit Bou-Rouch pump Vacuum pump Standpipe trap Williams corer Colonization devices Freeze coring Migration/dispersal No No No Yes No Yes No Spatial heterogeneity No Yes Yes Yes Yes Yes Yes Temporal variability Yes Yes Yes Yes Yes Yes Yes Interstitial sediment transport No No No Yes No Yes No Substrate characteristics No No No No No No Yes Used on submerged substrate No Yes Yes Yes Yes Yes Yes Used in riparian zone Yes Yes Yes Yes Yes Yes Yes Quantitative No No No No Yes Yes Yes Semi-quantitative No Yes Yes Yes Yes No No 4 Sampling strategy The design of a sampling strategy will vary according to the purpose of the investigation. Sampling site location may be influenced by pre-existing monitoring networks or previous investigations. The following should be considered: — sampling method; — number and location of sampling sites; — number of replicates per site required to characterize site heterogeneity (e.g. upwelling and downwelling, substrate characteristics); — sampling frequency; — sampling depth; — seasonal variability; — abiotic data requirements; — spatial and temporal scale of investigation. Scale is important when examining the hyporheic zone, as various processes occur at different spatial scales. For example, at a stream-bed (patch) scale the size, shape, sorting and stability of unconsolidated material are the primary determinants of porosity and permeability. These factors have a major influence on community composition over relatively short distances and methods have been developed to address this [11]. At a broader scale, lateral connectivity (e.g. between the riparian zone and out to the wider floodplain) is a key consideration. Hyporheic flow paths occur at multiple scales, from the stream bed to the catchment. SIST EN 16772:2016

EN 16772:2016 (E) 10 Case studies are presented in Annex A, giving examples of suitable sampling strategies for three different types of investigation. 5 Sampling methods 5.1 General This standard describes only those techniques that are suitable for use in wadable rivers; other approaches are available for sampling in deeper waters. Some techniques (e.g. freeze coring) require a recovery time after the equipment has been installed, allowing organisms to recolonize the sample area. Some techniques work better in fine-grained substrates while others can be used in coarser substrates. Surveyors should carry out a preliminary investigation of the substrates before selecting an appropriate technique. Each method is described in the following sections while Table 3 compares their ease of use, costs, recovery time and the possibility of obtaining repeat samples. Further details on all of these methods can be found in the PASCALIS sampling manual [12] and the Hyporheic Handbook [13]. Table 3 — Practical considerations when selecting sampling methods

Karaman-Chappuis pit Bou-Rouch pump Vacuum pump Stand-pipe trap Williams corer Coloniz-ation devices Freeze coring Minimum number of operators a 1 1 1 1 1 1 2 Equipment cost

(in Euro, 2016) < 200 < 1 000 < 350 < 200 < 1 000 < 500 < 10 000 Installation time ~15 min ~15 min ~15 min ~2 h ~15 min ~1 h ~30 min Time to collect one sample ~5 min ~10 min ~10 min ~10 min ~5 min ~10 min ~45 min Portability High Medium High Medium High Medium Low Typical recovery time after installation None None None 2 weeks None Variable Variable Repeat sampling possible No No Yes Yes No Yes No a Installation of equipment for some methods will require additional help, i.e. for the standpipe traps, colonization devices and freeze coring. 5.2 Karaman-Chappuis pit 5.2.1 Description and operation This is a rapid, qualitative method for obtaining a hyporheic sample from exposed river sediments, particularly in gravel and sand [14]. A pit (~50 cm diameter) is excavated to such a depth that its base is below the water level. Interstitial flow into the pit is maintained by extracting water, using a hand pump SIST EN 16772:2016

EN 16772:2016 (E) 11 or bailer, which is then filtered (using a mesh size appropriate to the study) to collect the invertebrates dislodged by the flow. In addition, small amounts of substrate from the bottom of the pit should be collected and carefully examined to obtain gastropods and bivalves. Pits should be dug on gravel bars or as close as possible to the river, while avoiding the risk of contamination by river water and benthic invertebrates. The method cannot be used during high flows as suitable sample sites will be inundated. Vegetated areas with compacted substrate should also be avoided. This method is suitable for preliminary investigations or as a roaming technique, as it is cheap, quick and easy to use. A disadvantage of this method is that sampling is limited to the shallow portion of the hyporheic zone (~30 cm depth) and to areas of exposed river sediment. 5.2.2 Species sampled A range of macroinvertebrates and meiofauna can be collected using this technique. Pits should be excavated and the sample taken quickly in order to capture all animals present. 5.2.3 Environmental variables A full suite of water chemistry analysis can be undertaken provided that there is no ingress of surface water into the excavated pit. Physical and chemical parameters (e.g. dissolved oxygen and water temperature) should be measured immediately after pit excavation. It may be possible to make estimates of permeability by timing infiltration into the excavated pit. 5.3 Bou-Rouch pump 5.3.1 Description and operation The principle of the method is to create a disturbance and maintain a flow around a pipe, sufficient to dislodge hyporheic organisms for extraction by pumping [15]. A hand-piston pump is fixed on top of a portable stainless steel standpipe that is hammered into the stream bed at various depths (typically 20 cm to 60 cm but occasionally up to 2 m) (see Figure 1). A standard volume should be collected for all samples; usually a minimum of 5 l although samples up to 10 l may be extracted. Sampling efficiency can vary depending upon the volume of water extracted and the nature of the substrate. The method can be used in submerged conditions as well as in exposed river sediments such as gravel bars. Approximately 3 to 5 replicates should be collected at each site, depending on habitat heterogeneity, with a distance of at least 1 m between them. SIST EN 16772:2016

EN 16772:2016 (E) 12 Dimensions in millimetres

Key 1 safety pin 9 bolt 2 lever 10 screen 3 upper piston valve 11 tip 4 liner 12 hand piston pump 5 body of the pump 13 mobile standpipe 6 lower piston 14 hyporheic zone 7 lower valve 15 standpipe with screen with 5-mm diameter holes 8 cap for hammering a sampling depth Figure 1 — The Bou-Rouch pump for sampling invertebrates in the hyporheic zone of rivers [15]; hole diameter and standpipe length can be varied An advantage of the Bou-Rouch pumping technique is that it causes relatively little disturbance to the river. Samples can be taken immediately after the installation of equipment so it can be used rapidly and is suitable for roaming surveys as the equipment is relatively portable. Pipes can also be left in situ for long periods if desired. The main disadvantage is that the method is not strictly quantitative as the sampled volume of hyporheic substrate cannot be measured and may vary depending upon the strength of force applied to the hand-piston pump during operation. Also, the location from which organisms are drawn in is unknown; pore-spaces and flow pathways are complex in the hyporheic zone so organisms may be sucked in from the proximity of the standpipe or from a greater distance. 5.3.2 Species sampled Owing to its high extraction rate the pump samples swimming organisms and those linked to the substrate. Note that the sample passes through the pump itself which can damage the collected SIST EN 16772:2016

EN 16772:2016 (E) 13 organisms. Both macroinvertebrates and meiofauna are captured. However, smaller and more passive species may be preferentially sampled. 5.3.3 Environmental variables Temperature, dissolved oxygen, conductivity and pH can all be measured within the pipe, before water is extracted. Water can also be extracted for further chemical analyses, but water used to prime the pump should be purged first. A semi-quantitative measurement of dissolved/particulate organic matter and fine sediment can also be made. Where pore spaces are completely saturated, a measure of permeability and porosity can be obtained by quantifying the pumping rate, i.e. noting the time taken to pump a certain number of litres. 5.4 Vacuum pump 5.4.1 Description and operation The vacuum pump method uses a similar principle to the Bou-Rouch, except that it creates a vacuum inside a closed bottle to extract and collect the sample (see Figure 2) [16]. An open-ended PVC pipe, with or without perforations (typically 5-mm diameter), is placed onto the end of a stainless steel T-bar, which is then hammered into the substrate to the required depth (typically 20 cm to 60 cm but occasionally up to 1 m). Pipes act as sampling wells, which can remain in situ for the duration of a study. If used in coarse substrates the addition of an outer metal tube can protect the PVC pipe from damage during insertion. Pumping (either manual or automatic) creates a vacuum which maintains an interstitial flow around the pipe that is sufficient to dislodge hyporheic organisms for extraction. It is a self-priming system that does not damage the organisms because they do not pass through the pump itself. A standard volume should be collected for all samples, usually a minimum of 5 l although samples up to 10 l may be extracted. If the pipe is submerged a seal should be made around the top during pumping to prevent benthos from entering. The method is most suitable for use instream, but it can also be used i

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