SIST EN ISO 17805:2026

• Abstract:

  This document specifies procedures for sampling, capture and preservation of environmental DNA (eDNA) in aquatic environments, stemming from organisms that are or have recently been present in a waterbody, have visited it or whose DNA has been introduced to the waterbody through some mechanism. This document also covers procedures for avoiding sample contamination and ensuring DNA quality, key properties of the filtering procedure and equipment and reporting standards. This document does not include the collection of eDNA from biofilms, sediments or similar sample types and does not cover sampling designs.

• Status: Published
• Public Enquiry End Date: 31-Mar-2025
• Publication Date: 26-Aug-2026
• ICS: 13.060.45 - Examination of water in general
• ICS: 13.060.70 - Examination of biological properties of water
• Technical Committee: KAV - Water quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 22-Jul-2026
• Due Date: 26-Sep-2026
• Completion Date: 27-Aug-2026
• Ref Project: EN ISO 17805:2026 - Water quality - Sampling, capture and preservation of environmental DNA from water (ISO 17805:2026)

• Replaces: SIST EN 17805:2023 - Water quality - Sampling, capture and preservation of environmental DNA from water
• Effective Date: 01-Oct-2026

SIST EN ISO 17805:2026 is the CEN adoption of ISO 17805:2026 for water quality work on environmental DNA (eDNA). It specifies how to sample, capture and preserve eDNA from water, how to avoid contamination, and what metadata to report. The standard is for people planning, carrying out or checking eDNA water sampling in biodiversity monitoring, laboratory work and related water assessment tasks.

What does SIST EN ISO 17805:2026 specify?

SIST EN ISO 17805:2026 specifies procedures for collecting eDNA from aquatic environments, preserving it for downstream analysis, and documenting the sample in a usable way. It also sets out contamination control and equipment expectations so that results are less likely to be biased by stray DNA or sample handling.

The scope is focused on water samples. It excludes eDNA collection from biofilms, sediments or similar sample types, as well as passive sampling methods and sampling designs. In practice, that means the document is about how to handle a water sample once the sampling approach has already been chosen.

The document is organized into clauses on scope, references, terms and definitions, principle, procedure, equipment and its use, preservative solutions, sampling report and contamination control. It also has two informative annexes.

Annex	What it covers
Annex A	Filter types suitable for eDNA work
Annex B	Additional metadata that can be recorded

What are the key requirements of SIST EN ISO 17805:2026?

SIST EN ISO 17805:2026 is built around a simple principle: collect a representative water sample, capture the eDNA, keep it intact, and prevent contamination throughout the workflow. That matters because eDNA is usually present in low amounts, so small handling errors can affect detection.

Plan the sampling around the water body and the target organisms

Clauses 5.1 and 5.2 say the sampling location, timing and number of samples should be chosen for the organism and water body being surveyed. The document points to factors such as shedding rates, abundance, spawning time, water volume filtered, spatial representativeness and the number of samples per water body. In practice, this means the sampler needs to think about biology and site conditions, not just collect water at random.

For lentic waters, the document notes that eDNA can be unevenly distributed when water is not well mixed. Representative sampling can be improved by pooling subsamples from different points or by continuous sampling across the water body. For deep waters, sampling should be taken from relevant depths.

Capture eDNA by filtration or other suitable separation methods

Clause 5.4 says eDNA, tissue fragments, cells and, for microbial communities, whole organisms shall be separated from the collected water by filtration or other processes such as gravity filtration or centrifugation where they are shown to work. The clause also notes that pumps, syringes and tubing need to be handled so they do not carry contamination from one sample to the next. In practice, this affects how you set up the field kit and how much of it must be cleaned or replaced between samples.

Preserve the sample quickly and under controlled conditions

Clause 5.5 gives the core preservation rule: separate and preserve the eDNA as soon as possible, ideally in the field. Water should be stored at or below 8 °C and protected from UV light before separation, because DNA breaks down over time. Filters may be preserved by a solution, by freezing at or below -18 °C, or by drying, depending on filter type and the manufacturer’s recommendation.

The standard also says the preservative solution used shall be recorded, because extraction protocols may need to be adjusted later. An internal positive control (IPC) can be added before preservation to monitor degradation during transport and storage. That gives the laboratory a way to judge whether a negative result may be linked to sample loss rather than absence of target DNA.

Use equipment and filters that do not add target DNA

Clause 6 says all field sampling equipment and materials should be target DNA-free. It recommends fresh single-use gloves when handling collection or filtration equipment and when contamination risk changes. It also describes common equipment such as syringes, pumps, tubing, filter capsules, storage tubes, labels, cooler bags and waste bags.

For filters, the document points to pore sizes typically from 0.22 µm to 5 µm, depending on the target organism and ecosystem. It also names suitable membrane materials such as cellulose nitrate (CN), polyethersulphone (PES), polycarbonate track etch (PCTE) and glass fibre. Annex A explains open, housed and enclosed filters and why enclosed filters generally reduce contamination risk.

Use suitable preservative solutions

Clause 7 gives examples of preservative solutions, including ethanol and Longmire’s solution, and says solutions should maintain DNA integrity through the storage and shipping conditions expected for the sample. For in-house preparation, the document says the work should be done in a decontaminated laboratory space and the solution should be checked to be target DNA-free before use. In practice, this is important because preservative choice affects extraction and downstream analysis.

Record the right metadata

Clause 8 separates metadata into required, highly recommended and recommended items. Required items include sample name, longitude, latitude, sampling date, sampled environment and habitat. Highly recommended items include sample size and filter pore size. Recommended items include sample ID, collection method, collection device and sample processing.

That reporting structure matters because eDNA data are only useful if others can interpret where, when and how the sample was taken. Annex B adds further metadata that can enrich the record.

Control contamination at every stage

Clause 9 is explicit that contamination control is not optional. It requires target DNA-free gloves, careful handling of open filters, and clean equipment throughout collection and processing. eDNA field blanks are used to check whether equipment or handling introduced DNA, and they are mandatory in some open-filtration situations.

For equipment that touches the water sample directly, Clause 9.3 says decontamination can use bleach or another proven DNA-destroying solution, followed by thorough rinsing with target DNA-free water. The document warns against using products that only kill microorganisms but do not destroy DNA. Equipment downstream of the filter, such as some pumps and tubing, does not need the same before-each-sample treatment but should be cleaned regularly.

What terms does SIST EN ISO 17805:2026 define?

• Environmental DNA (eDNA) - Nucleic acids from dead or living organisms, including single-stranded and double-stranded DNA from nuclear, mitochondrial, plastid, plasmid or chromosomal sources.
• Cross-contamination - Unintended transfer of DNA from one sample to another.
• Sample contamination - Exogenous DNA introduced to the sample during handling or processing.
• Decontamination - A procedure used to remove traces of DNA from material that may contact the sample.
• Internal positive control (IPC) - A quantified DNA control with a PCR-amplifiable sequence that is not naturally present in the sample and is used to interpret negative results.
• Open filter - A filtering system in which the membrane is removed with tweezers for further processing.
• Housed filter - A filter membrane protected in a solid housing during filtration and then removed for later processing.
• Enclosed filter - A system where the membrane stays encapsulated and the inflow and outflow can be closed for transport and storage.

Who uses SIST EN ISO 17805:2026?

SIST EN ISO 17805:2026 is used by water quality laboratories, environmental monitoring teams, biodiversity surveyors and technical staff who collect or process eDNA from water. It is relevant to people working on organism detection, aquatic ecosystem assessment and biomonitoring where the sample must be traceable and contamination-controlled.

It also matters to quality managers, project leads and buyers who need to check that a water eDNA sampling service follows a recognized procedure. The document is especially useful when a survey needs defensible sample handling, clear metadata and a workflow that supports downstream DNA analysis.

What changed in SIST EN ISO 17805:2026 from the previous edition?

SIST EN ISO 17805:2026 supersedes EN 17805:2023. The CEN endorsement notice states that the ISO text was approved as SIST EN ISO 17805:2026 without modification.

What does the SIST EN ISO 17805:2026 document contain?

SIST EN ISO 17805:2026 contains a clause-by-clause procedure that runs from planning and field preparation through filtration, preservation, reporting and contamination control. Figure 1 gives an overview of the key steps and considerations in the eDNA water sampling process.

The document also includes practical guidance on filter types, preservative solutions, sample report parameters and decontamination methods. Annex A explains the main filter categories used for eDNA work, and Annex B lists additional metadata terms that can be recorded to make datasets more usable.

SLOVENSKI STANDARD
01-oktober-2026
Nadomešča:
SIST EN 17805:2023
Kakovost vode - Vzorčenje, zbiranje in konzerviranje okoljske DNK iz vode (ISO
17805:2026)
Water quality - Sampling, capture and preservation of environmental DNA from water
(ISO 17805:2026)
Wasserbeschaffenheit - Probenahme, Erfassung und Konservierung von Umwelt-DNA in
Wasser (ISO 17805:2026)
Qualité de l'eau - Échantillonnage, collecte et conservation de l’ADN environnemental
prélevé dans l’eau (ISO 17805:2026)
Ta slovenski standard je istoveten z: EN ISO 17805:2026
ICS:
13.060.45 Preiskava vode na splošno Examination of water in
general
13.060.70 Preiskava bioloških lastnosti Examination of biological
vode properties of water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 17805
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2026
EUROPÄISCHE NORM
ICS 13.060.70 Supersedes EN 17805:2023
English Version
Water quality - Sampling, capture and preservation of
environmental DNA from water (ISO 17805:2026)
Qualité de l'eau - Échantillonnage, collecte et Wasserbeschaffenheit - Probenahme, Erfassung und
conservation de l'ADN environnemental prélevé dans Konservierung von Umwelt-DNA in Wasser (ISO
l'eau (ISO 17805:2026) 17805:2026)
This European Standard was approved by CEN on 26 June 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17805:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 17805:2026) has been prepared by Technical Committee ISO/TC 147 "Water
quality" in collaboration with 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 January 2027, and conflicting national standards shall
be withdrawn at the latest by January 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 17805:2023.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 17805 has been approved by CEN as EN ISO 17805:2026 without any modification.

International
Standard
ISO 17805
First edition
Water quality — Sampling, capture
2026-07
and preservation of environmental
DNA from water
Qualité de l'eau — Échantillonnage, collecte et conservation de
l’ADN environnemental prélevé dans l’eau
Reference number
ISO 17805:2026(en) © ISO 2026
ISO 17805:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 17805:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Procedure . 4
5.1 General .4
5.2 Considerations prior to fieldwork .5
5.3 Equipment preparation prior to fieldwork .5
5.4 Sampling the eDNA from water .5
5.5 Preserving the sample .6
5.5.1 General .6
5.5.2 Preserving eDNA in enclosed filters .6
5.5.3 Preserving eDNA in open filters .6
5.5.4 Preserving eDNA in housed filters .7
6 Equipment and its use . 7
7 Preservative solutions . 8
7.1 General .8
7.2 Examples of preservative solutions that can be made in-house .9
8 Sampling report . 9
8.1 General .9
8.2 Required parameters .9
8.3 Highly recommended parameters .10
8.4 Recommended parameters .10
9 Avoiding sample contamination . .11
9.1 General .11
9.2 Contamination that originates from equipment and people during sample collection
and processing .11
9.3 Decontamination procedure for sampling equipment . 12
9.3.1 General . 12
9.3.2 Materials and equipment that are in direct contact with the water sample . 12
9.3.3 Materials and equipment that are not in direct contact with the water sample . 12
Annex A (informative) Filter types .13
Annex B (informative) Metadata .15
Bibliography . 17

iii
ISO 17805:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 5,
Biological methods, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 230, Water analysis, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 17805:2026(en)
Introduction
The monitoring of organisms is key to the assessment of the status of aquatic ecosystems and is required by
national and international legislation such as the European Union Water Framework Directive (2000/60/
EC). A wide range of methods exist that describe how to monitor organisms in aquatic environments (e.g.
[2] [3] [4]
EN 14011 , EN 14757 , EN 15460 ). These approaches, however, necessitate either the capture or
collection, or both, of the organisms of interest, which can be a laborious and time-consuming process.
The possibility either to detect the presence of organisms or quantify relative abundance (e.g. see
Reference [7]), or both, in aquatic environments via the analysis of environmental DNA (eDNA) provides a
novel means to monitor biodiversity across a wide range of taxonomic groups, including microorganisms,
[8][9][10]
plants and animals . This approach allows examination of organismic diversity without the need to
directly isolate and capture organisms and it is expected to play a key role for future biomonitoring aiming
[11]
at species inventories with high temporal and spatial resolution . Albeit the power of the eDNA approach
[12]
has been repeatedly reported , there is a great need for standardizing the application of eDNA-based
[13][14]
assessment of aquatic biodiversity .
This document addresses the first crucial step for any further downstream eDNA-based analyses of
biodiversity. Routine sampling of benthic diatoms from rivers and lakes adapted for metabarcoding analyses
[5]
is given in CEN/TR 17245 .
v
International Standard ISO 17805:2026(en)
Water quality — Sampling, capture and preservation of
environmental DNA from water
WARNING 1 — Persons using this document should be familiar with water sampling protocols used
to assess biological diversity. This document does not purport to address all of the safety problems,
if any, associated with its use. It is the responsibility of the user to establish appropriate safety and
health practices.
WARNING 2 — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be
carried out by suitably qualified staff.
1 Scope
This document specifies procedures for sampling, capture and preservation of environmental DNA (eDNA)
in aquatic environments, originating from organisms
— that are present or have recently been present in a water body, or
— whose DNA has been introduced to the water body through some mechanism.
This document also specifies procedures for avoiding sample contamination and ensuring the integrity
of environmental DNA during water filtration and sample preservation. It also specifies the required
equipment and metadata reporting.
This document excludes:
— methods for the collection of eDNA from biofilms, sediments or similar sample types;
— passive sampling methods;
— sampling designs.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
cross-contamination
unintended transfer of any source of DNA from one sample to another sample

ISO 17805:2026(en)
3.2
decontamination
procedure to remove any source of trace of DNA from material that can come into contact with the sample
3.3
enclosed filter
filtering system where the filter membrane is encapsulated and where the inflow and outflow can be closed
for transport and storage
Note 1 to entry: The eDNA contained on the filter is typically extracted without removing the membrane from the filter
capsule greatly reducing the risk of contamination of samples. See Figure A.1 c) for further description and illustration
of the filter type, filtering and lysis step.
3.4
environmental DNA
eDNA
nucleic acids from dead or living organisms including single-stranded (ss) and double-stranded (ds) DNA
fragment from nuclear and mitochondrial or plastid DNA of eukaryotes as well as plasmid and chromosomal
DNA of prokaryotes
Note 1 to entry: Including DNA from various sources such as unicellular or small multicellular organisms or tissue
particles (e.g. shed cells, faeces), and gametes of multicellular organisms.
3.5
environmental DNA field blank
eDNA field blank
sample obtained from processing target DNA-free water (e.g. molecular grade water) through all the
equipment used and following all procedures involved in the eDNA sampling process to check whether the
equipment and procedures introduced either sample contamination (3.11) or cross-contamination (3.1), or
both
3.6
housed filter
filtering systems in which a filter membrane is protected within a solid housing during the filtration process,
which is opened subsequently to remove the filter membrane with tweezers for further processing
Note 1 to entry: The filters are removed from the housing for eDNA extraction. The housing can be opened and the
filter removed for preservation and later processing. See Figure A.1 b) for further description and illustration of the
filter type, filtering and lysis step.
3.7
lysis buffer
buffer solution to preserve the DNA present in the sample and to lyse or open cells as a first step of the DNA
extraction
3.8
internal positive control
IPC
quantified amount of synthetic or natural DNA containing a PCR-amplifiable sequence that does not naturally
occur in the sample, used to interpret negative results
Note 1 to entry: The IPC can be added to the sample, the preservation buffer or the lysis buffer (3.7) at a known
concentration to verify the efficiency of the entire workflow from DNA preservation to DNA amplification. To
determine the efficiency of specific steps in the workflow such as the DNA extraction or DNA amplification, the IPC is
added prior to the respective step within the workflow.
3.9
open filter
filtering system from which the filter membrane is removed with tweezers for further processing
Note 1 to entry: The filtering system can include vacuum or peristaltic units. See Figure A.1 a) for further description
and illustration of the filter type, filtering and lysis step.

ISO 17805:2026(en)
3.10
pre-filtration
use of a filter membrane, mesh or hose strainer with a larger pore-size than the main filter membrane (used
for capturing the eDNA) through which water is passed first to remove larger particles of sediment, plant
material or algae to increase the volume of water that can be filtered before saturation of the main filter
3.11
sample contamination
process by which exogenous DNA is unintentionally introduced to the sample
Note 1 to entry: DNA that is already present in the water before the eDNA sampling was undertaken is not considered
as contamination.
3.12
target DNA
source or trace, or both, of DNA from the surveyed species or taxa
4 Principle
Environmental DNA is captured and separated from the surveyed water body via a representative water
sample, according to an appropriate sampling design. During the whole procedure, cross-contamination and
sample contamination are avoided and eDNA integrity is maintained.
An overview on the key steps and considerations for the sampling, capture and preservation of eDNA from
water is shown in Figure 1.
ISO 17805:2026(en)
Figure 1 — Key steps and considerations for the eDNA water sampling process
5 Procedure
5.1 General
Water should be sampled to capture and separate eDNA via filtration, centrifugation or gravity filtration.
[15]
The probability of obtaining eDNA from the targeted organism(s) is positively correlated with :
— the optimum sampling location and time point (including season) with regard to the organism(s) eDNA
[16][17]
shedding rates, abundances (also of non-target organisms) including spawning time, metabolic
activity and locomotion;
— the volume of water filtered;

ISO 17805:2026(en)
— the spatial representativeness of the samples;
— the number of samples per water body.
5.2 Considerations prior to fieldwork
Depending on the different applications or goals of each eDNA survey, the most appropriate sampling
conditions and design shall be assessed based on case-by-case evidence to obtain water samples
representative of the water body and the organisms being monitored. These can include hydrological,
meteorological, seasonal or temporal, biological or ecological, and physiological variation.
This is particularly important in lentic (non-flowing) water bodies since eDNA is often unevenly distributed
[18][19]
when the water is not well mixed. Representative sampling can be achieved by merging (i.e. pooling)
subsamples collected at different points in the water body or alternatively by continuous sampling systems
that move across the water body while drawing up water. When surveying deep water bodies and targeting
deep water dwelling organisms, water should be sampled from relevant depths (e.g. with Niskin samplers;
for decontamination processes, see Clause 9).
The following shall be considered when planning where and when to collect samples and subsamples:
— Features of the water body, including its size, depth, flow, stratification and the distribution of
microhabitats as well as inlets and outlets of the water body. If the study requires separate analyses of
subsamples (e.g. biota in different depth layers), new or clean collection vessels shall be used for each
subsample.
[20]
— Biology of all target taxa, including habitat preferences, life cycle and (if known) DNA shedding rates.
[21]
Detection probability for individual species can be increased by timing sampling to coincide with
times of intense activity (e.g. spawning). Temporal variations in the amounts of released eDNA by the
target species needs to be considered. It is also important to consider whether target taxa are likely to
be present in the water body at the time of sampling.
NOTE Pooling of samples can lead to a decreased chance of detecting rare targets.
5.3 Equipment preparation prior to fieldwork
Prior to fieldwork a sufficient number of collecting vessels and equipment shall be cleaned to avoid
contamination (for detailed instruction, see Clause 9).
5.4 Sampling the eDNA from water
Various systems are used for sampling and filtering water. Some involve initially gathering water into a
collecting vessel where it is mixed and then filtered subsequently; other systems filter the water directly as
it is drawn up from the water body. When the water is not filtered directly in the water body, the filtration
can be carried out on the shore, on boats, or in the laboratory.
eDNA, tissue fragments, cells and (in case of microbial communities) whole organisms shall be separated
from the collected water via filtration or other processes (e.g. including gravity filtration and centrifugation).
This can be achieved manually with syringes or using a hand or powered pump or by gravity filtration or
centrifugation, where it has been demonstrated to work. If a pump is used and water passes through a pump
tubing before reaching a filter, then a new or decontaminated pump tubing shall be used for each sample.
If subsamples are being merged into a pooled sample, ensure that they are well mixed before starting to
filter.
When sampling eDNA, precaution measures shall be considered to avoid contamination (for detailed
instruction, see Clause 9).
ISO 17805:2026(en)
5.5 Preserving the sample
5.5.1 General
The eDNA contained in the collected water should be separated from the water immediately in the field.
Note that DNA breakdown will occur when it is not possible to immediately separate and preserve the
collected water sample on-site. The rate at which this breakdown occurs, depends on several parameters
such as chemical composition of the collected water, storage conditions of the water sample, exposure to
sunlight (e.g. UV), as well as the type of organism releasing the eDNA. In general, the longer the period
between collection and preservation, the more eDNA will be broken down. Note that at room temperature,
large amounts of target eDNA can be lost within 12 h to 24 h. When it is not possible to separate the eDNA
from the water on-site, then separation should be undertaken as soon as possible (usually no longer than
[22]
6 hours unless a preservation method is used to elongate the storage period (see e.g. Reference [23]).
Water shall be stored ≤ 8 °C and protected from UV light prior to separating eDNA from the collected water
by filtration or centrifugation. The obtained eDNA sample (e.g. filter, centrifuged pellet) shall be immediately
preserved in the field for transportation to the laboratory and storage prior to eDNA extraction. In case the
eDNA collected on a filter membrane has to be preserved (i.e. is not directly used for lysis), the membrane
shall be either completely covered by preservation solution or be frozen (≤−18 °C), or both, or desiccated,
depending on filter type and manufacturer’s recommendation. Maximum storage time of filters depends on
the DNA preservation method used.
If a preservative solution is used, the solution used shall be clearly recorded because downstream laboratory
protocols for DNA extraction may need to be modified according to the preservative solution used. If
freezing is used for preservation, the filter membrane should either be frozen immediately after filtration is
completed or kept at 5 °C ± 3 °C no longer than 3 h (part of the 6 h mentioned before) and protected from UV
light. Once the filter is frozen, it should remain continuously so until DNA extraction begins.
An IPC should be added before preserving filter samples to allow for monitoring eDNA degradation during
transport and storage of the sample. It is recommended to include an IPC in the preservative solution that
can be quantified after storage and DNA extraction using a quantitative PCR assay (e.g. quantitative PCR or
digital droplet PCR) to track sample degradation. If using freezing or drying and also using an IPC, add the
IPC to the filter membrane with the lysis buffer during the first phase of the DNA extraction and this will
serve only as an indication of successful DNA extraction; it will not serve as a degradation control.
Additional requirements for different filter types are mentioned 5.5.2 to 5.5.4.
NOTE The obtained type of eDNA depends on t
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