EN 17218:2019
(Main)Water quality - Guidance on sampling of mesozooplankton from marine and brackish water using mesh
Water quality - Guidance on sampling of mesozooplankton from marine and brackish water using mesh
This document specifies procedures for sampling of mesozooplankton using nets and continuous ribbon-sampling devices in marine and brackish waters for the purpose of water quality assessment and determination of ecological status of ecosystems.
Guidance on sampling procedures and the subsequent steps of preservation and storage are given. The sampling procedures allow estimates of species occurrence and their abundance (relative or absolute), including spatial distribution and seasonal and long-term temporal trends, for a given body of water.
The described methods are restricted to the sampling of mesozooplankton that inhabit marine and brackish waters and exclude the shallow littoral zones which require a different type of sampling (e.g. zooplankton in salt marshes).
Wasserbeschaffenheit - Anleitung zur Probenahme von Mesozooplankton aus marinen und Übergangsgewässern mittels Netzen
Dieses Dokument legt Verfahren zur Probenahme von Mesozooplankton mithilfe von Netzen und kontinuierlichen Probenahmegeräten in marinen und brackigen Gewässern zum Zwecke der Bewertung der Wasserqualität und der Bestimmung des ökologischen Zustands von Ökosystemen fest.
Es wird eine Anleitung zu Probenahmeverfahren und den anschließenden Schritten der Konservierung und Lagerung gegeben. Die Probenahmeverfahren ermöglichen eine Abschätzung des Vorkommens von Arten und deren Abundanz (relativ oder absolut), einschließlich der räumlichen Verteilung und saisonaler sowie Langzeittrends für einen bestimmten Wasserkörper.
Die beschriebenen Verfahren gelten nur für die Probenahme von Mesozooplankton, das marine und brackige Gewässer bewohnt, und berücksichtigen nicht die flachen Uferzonen, die eine andere Art der Probenahme erfordern (z. B. Zooplankton in Salzmarschen).
Qualité de l'eau - Document d'orientation pour l'échantillonnage du mésozooplancton dans les eaux de mer ou saumâtres à l'aide de filets
Le présent document fournit des procédures pour l'échantillonnage du mésozooplancton dans les eaux marines et saumâtres, à l'aide de filets et de dispositifs d'échantillonnage en continu sur bandes collectrices, dans le but d'évaluer la qualité de l'eau et de déterminer l'état écologique des écosystèmes.
Des recommandations relatives aux procédures d'échantillonnage et aux étapes suivantes de conservation et de stockage sont fournies. Les procédures d'échantillonnage donnent une estimation de l'occurrence des espèces et de leur abondance (relative ou absolue), y compris la distribution spatiale et les tendances temporelles saisonnières et à long terme pour une masse d'eau donnée.
Les méthodes décrites sont limitées à l'échantillonnage du mésozooplancton qui habite les eaux marines et saumâtres et excluent les zones littorales peu profondes qui requièrent un autre type d'échantillonnage (par exemple, le zooplancton des marais salants).
Kakovost vode - Navodilo za vzorčenje mezozooplanktona v morskih in brakičnih vodah s pomočjo mrež
Ta dokument določa metodo za vzorčenje mezozooplanktona iz morskih in brakičnih vod s pomočjo mrež.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2019
Kakovost vode - Navodilo za vzorčenje mezozooplanktona v morskih in brakičnih
vodah s pomočjo mrež
Water quality - Guidance on sampling of mesozooplankton from marine and brackish
water using mesh
Wasserbeschaffenheit - Anleitung zur Probenahme von Mesozooplankton aus marinen
und Übergangsgewässern mittels Netzen
Qualité de l'eau - Document d'orientation pour l'échantillonnage du mésozooplancton
dans les eaux de mer ou saumâtres à l'aide de filets
Ta slovenski standard je istoveten z: EN 17218:2019
ICS:
13.060.10 Voda iz naravnih virov Water of natural resources
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 17218
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2019
EUROPÄISCHE NORM
ICS 13.060.70
English Version
Water quality - Guidance on sampling of mesozooplankton
from marine and brackish water using mesh
Qualité de l'eau - Document d'orientation pour Wasserbeschaffenheit - Anleitung zur Probenahme von
l'échantillonnage du mésozooplancton dans les eaux de Mesozooplankton aus marinen und
mer ou saumâtres à l'aide de filets Übergangsgewässern mittels Netzen
This European Standard was approved by CEN on 15 March 2019.
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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey 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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17218:2019 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Principle . 7
5 Sampling device . 8
5.1 General . 8
5.2 Nets . 8
5.3 Other field equipment . 10
5.4 Preserving solutions and other chemicals . 11
6 Prearrangements of sampling . 12
6.1 Documentation of strategies and methods . 12
6.2 Preparation of sampling equipment . 12
6.3 Safety instructions . 12
7 Sampling procedure . 12
7.1 Investigation programme . 12
7.2 Number and location of sampling sites . 13
7.2.1 General . 13
7.3 Diurnal sampling period . 14
7.3.1 General . 14
7.3.2 Sample size . 14
7.3.3 Geographical localization of sampling sites . 14
7.4 Operating the sampling device . 15
7.4.1 Vertical net hauls . 15
7.4.2 Horizontal tows/hauls . 15
7.4.3 Filling and labelling of sample bottles . 16
7.4.4 Preservation and storage of samples . 17
7.5 Field data recording . 18
8 Quality assurance . 18
Annex A (informative) Examples of sampling devices . 19
A.1 Bongo nets . 19
A.2 Continuous plankton recorder . 19
A.3 WP2 net . 20
A.4 Multinets . 20
A.5 Gulf VII sampler . 21
Annex B (informative) Preservation . 22
B.1 Preservation. 22
B.2 Formaldehyde (formalin) . 22
B.2.1 General . 22
B.2.2 Advantages of formaldehyde . 22
B.2.3 Disadvantages of formaldehyde . 23
B.3 Lugol’s Iodine . 23
B.3.1 General . 23
B.3.2 Advantages of Lugol’s Iodine (over formaldehyde) . 23
B.3.3 Disadvantages of Lugol’s Iodine . 23
B.4 Ethanol . 24
B.4.1 Advantages of ethanol . 24
B.4.2 Disadvantages of ethanol . 24
Annex C (informative) Corrections of depth from wire angle [1] . 25
Annex D (informative) Example of a field data sheet . 26
Annex E (informative) Ribbon-sampling devices . 27
E.1 Continuous plankton recorder (CPR) . 27
E.2 Longhurst Hardy plankton recorder (LHPR) . 27
Bibliography . 28
European foreword
This document (EN 17218:2019) 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 November 2019, and conflicting national standards
shall be withdrawn at the latest by November 2019.
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.
According to the CEN-CENELEC Internal Regulations, the national standards organisations 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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Introduction
The Zooplankton community is an important part of the pelagic food web, since it forms the link
between primary producers and higher trophic levels. Changes in phytoplankton biomass and
species/size composition change mesozooplankton community structure and productivity. Such
changes potentially influence fish stock recruitment and sedimentation (i.e. indirectly affecting oxygen
concentration in the bottom water) [1].
Surveys of zooplankton have provided valuable information for the environmental monitoring of
marine and brackish waters, because this group includes species which:
— occur in a wide range of marine and brackish waters over a large geographical area and at the same
time have specific environmental requirements,
— are relatively well known with regard to their geographical distribution and environmental
requirements, and
— have a generally high capacity for dispersal enabling them to respond rapidly to remedial actions,
while sampling requires only a modest expenditure of time and equipment.
A procedure for analysing zooplankton (identification, counting and biomass determination) in marine
and brackish waters is given in EN 17204 [2]. This procedure comprises how to identify and enumerate
zooplankton collected in nets which is utilized to estimate quantitative information on diversity,
abundance and biomass with regard to spatial distribution and long-term temporal trends for a given
body of water.
WARNING — 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.
1 Scope
This document specifies procedures for sampling of mesozooplankton using nets and continuous
ribbon-sampling devices in marine and brackish waters for the purpose of water quality assessment
and determination of ecological status of ecosystems.
Guidance on sampling procedures and the subsequent steps of preservation and storage are given. The
sampling procedures allow estimates of species occurrence and their abundance (relative or absolute),
including spatial distribution and seasonal and long-term temporal trends, for a given body of water.
The described methods are restricted to the sampling of mesozooplankton that inhabit marine and
brackish waters and exclude the shallow littoral zones which require a different type of sampling (e.g.
zooplankton in salt marshes).
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 terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
pelagic zone
free body of water beyond the bottom
3.2
thermocline
layer in a thermally stratified body of water in which the temperature gradient is at a maximum
[SOURCE: ISO 6107-1:2004, 75]
3.3
habitat
area of the environment in which a particular organism lives, including its characteristic assemblages of
plants and animals
Note 1 to entry: It can be either the geographical area over which it extends, or the particular station in which a
specimen is found.
[SOURCE: EN ISO 10870:2012, 2.6, modified – Note 1 to entry has been added]
3.4
biomass concentration
total mass of living organic matter, measured as wet weight, dry weight or ash free dry weight
−3 −3 −3
Note 1 to entry: Unit: g l , g ml , or g m of carbon.
3.5
plankton
organisms drifting or suspended in water, consisting chiefly of minute plants or animals, but including
larger forms having only weak powers of locomotion
[SOURCE: ISO 6107-5:2004, 41]
3.6
zooplankton
animals present in plankton
[SOURCE: ISO 6107-5:2004, 49]
3.7
mesozooplankton
zooplankton of 0,2 mm to 20 mm size
3.8
sampling site
general area within a body of water from which samples are taken
Note 1 to entry: A site is defined in terms of its location (geographical position, depth) and invariant conditions
(e.g. type of bottom in shallow-water areas) and is delimited on the basis of the accuracy with which these are
given. In cases of doubt when sampling sites have to be re-identified, most weight should be placed on depth and
type of bottom.
[SOURCE: EN ISO 5667-6:2016, 3.10, modified – “or location” is replaced by “within a body of water”
and note 1 to entry has been added]
3.9
sampling station
precise location where samples are collected
Note 1 to entry: A sampling station is defined by its geographical position (latitude, longitude), its depth
(relative to chart datum and normalized to mean low water as given in tide tables) and any other invariant or
physical conditions. The station is delineated using the given level of precision. In cases of doubt, when revisiting
sampling stations, emphasis should be placed on landmarks and water depth.
[SOURCE: EN ISO 16665:2013, 2.2.5]
3.10
trend monitoring
study intended to reveal any changes in variables such as diversity and in the ecological status of a body
of water over time
3.11
preservation
protection from (bio)chemical degradation of organic matter
4 Principle
The sampling strategy determines which information on the current status of the zooplankton
community can be achieved. The selection of sampling sites (numbers and location), sampling depth,
time and frequency of sampling, number of replicates and type of sampling gear is of great importance
for the evaluation of the data collected. As a general guidance EN ISO 5667-1 should be consulted.
5 Sampling device
5.1 General
The choice of the sampling devices to be used depends on the aims of the investigation. This document
provides some general recommendations and then focuses on standard requirements for net sampling.
Table 1 describes advantages and disadvantages of different common zooplankton sampling devices.
Table 1 — Examples of zooplankton sampling devices
Sampling device Advantages Disadvantages
Simple nets Medium amounts of water can be Can be subject to clogging of mesh.
sampled, can operate easily as
vertical hauls or in restricted
areas.
Multiple nets Large amounts of water can be Difficult to operate in restricted areas.
sampled. Sample can be
separated by different filter sizes
to reduce damage and improve
identification. Allows adjustment
of sampling to physical/biological
conditions (e.g. any
stratification).
High speed samplers Can be towed at higher speeds Difficult to operate in restricted areas.
typically around 9 km/h. Increased risk of damage to delicate
e.g. Gulf VII
organisms.
Continuous recorders Provides spatial information Can Semiquantitative, damage to delicate
operate over very large areas and organisms, e.g. gelatinous
— using ribbons of tape
using vessels of opportunity. mesozooplankton. Limited sampling
e.g. continuous
Used for both phytoplankton and depth.
plankton recorder
zooplankton investigations.
NOTE 1 Several overviews exist on the most widely used zooplankton sampling techniques and their
advantages and drawbacks (e.g. [9, 10, 11]).
NOTE 2 Ribbon-samplers have a fixed method which is largely determined by the internal mechanism and
design of ribbon. Continuous plankton recorder (CPR) devices are designed for us on “vessels of opportunity” so
are also restricted in their range and depth, see Annex E.
5.2 Nets
Polyamide plankton nets with a cod-end and a drain cock of various dimensions and mesh sizes may be
used for sampling (Figure A.1). The purpose of the investigation determines the selection of net types
and its mesh sizes. Examples of commonly-used nets are:
a) Bongo net (Figure A.1);
b) MOCNESS (Multiple Opening and Closing Net with an Environmental Sensing System) [12, 13];
c) WP2 net (Figure A.3);
d) Multinet (Figures A.4 and A.5);
e) Gulf VII sampler (Figure A.6).
For details, see Annex A.
It is important that nets should have a large filtering surface relative to their opening in order to ensure
that filtering is as efficient as possible. A net with an opening diameter of 30 cm, for example, should
have a length of about one metre as a minimum. A cylindrical net section above the conical part increase
the filtering area compared with a conical plankton net with the same opening diameter and length.
The size of opening itself can determine what is obtained on the mesh. Smaller openings will limit the
capture of faster moving zooplankton and some larger mesozooplankton can evade 1 m ring net. A flow
meter mounted in the net mouth should be used whenever possible.
Closing nets, as opposed to simple open mouthed nets should be used for sampling along transect such
as at discrete depth layers.
NOTE Closing nets remain open until the haul is complete and the mouth or the entrance to the cod-end is
closed. The design and mechanism vary depending on the sampling device being used [13].
Common mesh sizes are e.g. 100 µm in the Baltic Sea or 200 µm up to 500 µm in the North Sea. If early
developmental stages are to be included, in order to provide information on the population dynamics of
zooplankton, nets with a mesh size of up to 50 µm at a maximum are recommended. Mesh sizes above
200 µm miss a large proportion of the smaller zooplankton. Table 2 gives a summary of mesh
requirements for different zooplankton.
Table 2 — Summary of mesh requirements for different zooplankton
Zooplanktonic group Suitable mesh sizes Mesh arrangement
Rotifers, nauplii of crustacea Approx. 50 µm, but > 40 µm Nets with meshes smaller than
(which mostly belong to the 40 µm will readily become
microzooplankton size fraction) clogged and their use should
normally be avoided, although
they may be useful in
oligotrophic waters.
Crustacean plankton only 50 µm (max. 100 µm)
Rotifers and crustaceans, 45 µm for rotifers, 90 µm for 3 nets with 3 different mesh
including predatory most of the crustaceans, and sizes
species
≥ 150 µm for predatory species
Hydromedusae Non-filtering cod-ends should be
used to reduce damage to these
delicate organisms.
All the mesh sizes mentioned in this document should be regarded as for guidance only. Mesh sizes will
also vary somewhat from manufacturer to manufacturer.
It is recommended that, in the case of vertically stratified habitats, the nets are equipped with a closing
mechanism with case weight and a flow counter with backflow stop to allow stratified sampling.
The ribbon-based samplers such as the continuous plankton sampler (Figure A.2) use a band of gauze
rather than a net. In the case of the CPR this is 300 µm mesh. For more on ribbon-based samplers, see
Annex E.
5.3 Other field equipment
If available, nets should be equipped and deployed with the help of pressure meters so that the actual
vertical position of the net is known.
Field equipment in addition to sampling devices may comprise:
5.3.1 Winch with line-length counter or for coastal areas a line with length markings fitted with a
shackle or similar device to enable the line to be joined to the net.
5.3.2 Flowmeter, either real time or self-logging.
5.3.3 Draining cup with nylon netting, which is capable of being attached to the net either by means
of a tightening strip or tape sewn into the net. The netting of the draining cup should have the same
mesh size as the net. A draining cup with hose and hose clamp can also be utilized.
5.3.4 Weight, e.g. a standard sounding lead weight, in order to minimize wire angles.
5.3.5 Closing device for depth-stratified hauls.
5.3.6 Wire angle blade.
5.3.7 Echosounder or depth finder.
5.3.8 Global Positioning System (GPS).
5.3.9 Sea water connecting tube to flush the net upon retrieval.
5.3.10 Sieves of a mesh size smaller than the net mesh size to concentrate the sample.
5.3.11 Wash bottle with filtrated sea water for rinsing out sieves and draining cups. The sea water
from the sea water hose should be filtrated through a plankton bucket filter, with a small mesh (e.g.
45 µm and always less than the mesh of the sampling devices being used) before filling in the spray
bottle.
5.3.12 Small plastic funnel, may be needed to transfer the sampled material to the sample bottle.
5.3.13 Mixing vessel, e.g. plastic bucket or similar, to combine a number of individual samples into a
single sample in the field. Combining samples may be necessary to reducing analysis times and costs.
5.3.14 Plastic or glass bottles with screw tops for storing samples (e.g. 100 ml, 200 ml or 250 ml,
depending on sampling volume).
5.3.15 Labels or tape to attach to the outside of the sample bottles. Waterproof paper for labels to put
inside the sample bottles.
5.3.16 Marker pen. If ethanol is being used, an alcohol-proof pen or pencil is recommended for both
internal and external marking.
If a volume sampler is being used (with the exception of a Schindler-Patalas trap) filtration equipment
is also required to concentrate the samples. This may take the form of either a plankton net or a large
funnel with draining cup fitted with a netting.
5.4 Preserving solutions and other chemicals
A number of different preserving solutions for different types of applications are available. The
advantages and disadvantages of each of these solutions are defined in Annex B. Preserving solutions
for field use should be kept in small stoppered bottles and should be accompanied by a pipette or safety
dispenser for transferring the solution to the plankton samples. The bottles should be kept in a plastic
box or container with lid during transportation.
5.4.1 Formaldehyde (CH O), 40 % (v/v).
40 % (v/v) formaldehyde is diluted to 4 % formaldehyde (CH O) solution, by mixing 1 part ∽400 ml
−1
l formaldehyde solution and 9 parts water. Before diluting the strong formaldehyde it should be
buffered. Disodium tetraborate (borax) (Na B 0 · 10 H 0) or hexamethly tetramine (C H N ) can
2 4 3 2 6 12 4
be used.
In the case of borax buffering, add 2 g of borax to every 98 ml of 40 % formaldehyde. Borax will be in
excess and raise the pH to 8 to 8.2.
In the case of hexamethyl tetramine buffering, dilute the formaldehyde with demineralized water to
20 % (v/v) to avoid precipitation, and then add 100 g of hexamethyl tetramine and 40 g to 80 g sucrose
per litre of 20 % formaldehyde [11].
WARNING — Formaldehyde may trigger allergies or cancers and should therefore be handled with
care.
5.4.2 Ethanol, (C H OH), 96 % (v/v) or 99 % (v/v).
2 5
5.4.3 Lugol’s Iodine.
Acidified Lugol’s Iodine: Dissolve 100 g KI (potassium iodide) in 1 l of distilled or demineralized water;
then add 50 g iodine (crystalline), shake until it is dissolved and add 100 ml of glacial (anhydrous)
acetic acid. As this solution is close to saturation, any precipitate should be removed by decanting the
solution before use.
NOTE Acidic Lugol’s can dissolve calcareous skeletons of zooplankton.
5.4.4 Saccharose, 40 g to 80 g per litre formaldehyde.
5.4.5 Anti-fungal agents, such as Steedman’s Observation fluid. This fluid combines 0,5 % propylene
phenoxetol and 5 % propane-1-2-diol in distilled water. Which is then added to samples originally
preserved with formaldehyde [14].
5.4.6 Mastail and Battaglia solution. Prepare separate solutions by dissolving 8 g
buthylhydroxyanisol (BHA, C H O) in 500 ml propane-1-2-diol (C H O) and 20 g
22 32 4 3 8 2
ethylenediaminetetraacetic acid (EDTA, C H N O Na · 2 H O) in 500 ml demineralized water. Add
10 14 2 8 2 2
−1
both solutions to 2 L of ∽400 ml l of formaldehyde solution while stirring and buffer to pH 8 with
sodium glycerophosphate (C H Na O P · H O). After buffering add 2 g ascorbic acid (C H O ) and
3 7 2 6 2 6 8 6
demineralized water up to 5 L. Samples are preserved by adding 6 ml of the stock solution per 100 ml of
sample in sea water.
NOTE This solution improves the preservation of chromatophores, which are key features for identification
of decapod larvae or fish eggs and larvae.
6 Prearrangements of sampling
6.1 Documentation of strategies and methods
The following documentation should be available before the start of field work:
a) description of objectives and strategy;
b) description of methods;
c) safety instructions;
d) personnel plan;
e) list of equipment and instruments;
f) registration forms;
g) procedures for the maintenance of records and samples;
h) quality assurance requirements according to EN 14996 and EN ISO/IEC 17025;
i) chemical safety data sheets.
6.2 Preparation of sampling equipment
Nets should be clean to avoid contamination of samples between sites, to avoid the spreading of flora
and fauna between water bodies and to ensure optimum filtration capacity is maintained.
The sampling equipment should be disinfected or washed in freshwater between deployments in the
different waters. Appropriate control measures need to be taken when using disinfectant near to water
bodies to avoid harm to the environment. The nets should be washed in warm freshwater with
detergent or in an ultrasonic water-bath, in order to reduce clogging and ensure optimum filtration, at
regular intervals, e.g. at the end of the survey day.
Check that the netting in the plankton net and draining cups is completely free of holes and tears.
Damaged nets are to be exchanged.
Check that the line is securely attached to the plankton net or volume sampler.
Check that the plankton sampler’s closing mechanism is functioning well and that any seals are in order.
The sample bottles should be labelled and the requisite amounts of preserving solution should be added
to the bottles before the start of fieldwork.
6.3 Safety instructions
Before initiating the survey notify a contact of which localities and areas are to be surveyed on a specific
day. Check the weather forecast in order to ensure safe and effective surveying conditions.
7 Sampling procedure
7.1 Investigation programme
An investigation programme shall be developed according to the investigation aims, required precision
of results, hydrographical conditions in the area, prior knowledge of local pollution sources, results of
previous investigations and any other factors that may be of significance.
Qualitative samples provide information about the species composition, number of species, size
distribution and relative dominance of species and groups of zooplankton.
Quantitative samples also provide information regarding the quantity of zooplankton (individual
density) per unit volume. Quantitative samples also allow calculation of biomass and production for the
zooplankton assemblage as a whole as well as for the individual species.
In production studies (estimates of biomass and secondary productivity) it is essential to obtain
quantitative samples. If the objective is to survey all species in a water body, net hauls are
recommended.
Zooplankton is normally irregularly distributed, i.e. there is often a horizontal and a vertical variation.
Vertical patterns and vertical migration are also common among zooplankton species. To obtain
complete estimates of species composition and abundances, samples should always sample the whole
water column (integrated or depth stratified).
If the aims of the study require information about the horizontal distribution of zooplankton, samples
should be obtained from several locations along a transect. Other horizontal gradients (e.g. salinity) can
also be considered. If information regarding spatial variation or a high level of precision of the estimates
is required, it may be necessary to draw up a sampling programme adapted to the needs (e.g. replicated
or vertical stratified sampling).
7.2 Number and location of sampling sites
7.2.1 General
The number and location of the sampling sites should be determined by the aims of the study and the
level of accuracy in the provided estimates. In general, sites selected should be representative of the
area under consideration.
The samples should be collected at the same site as used for other observations (temperature, Secchi
depth, water chemistry, phytoplankton, etc.).
If the objectives of the study make it important to obtain information regarding the vertical distribution
of the zooplankton, it is recommended to collect samples at a number of depths. Samples may be
collected individually from fixed depths, e.g. from either ~5 m above the bottom to the surface (shallow
stations) or in depth layers (deep stations) as designed and specified by regional monitoring
programmes.
Appropriate sampling intervals and replicates are to be chosen which should keep in mind seasonality,
daily vertical migrations (see 7.3.1, [17]) and swarming.
Studies, which primary target at providing information on species composition and dominance, should
aim at covering population maxima of as many species as possible. It is recommended that samples
should be collected monthly at least in the course of the season depending on the cycles of different
generations of organisms of interest. If, for practical reasons, samples can be collected only twice in the
course of the season, they should be taken in spring or early summer and high or late summer.
Similarly, if only one sampling occasion per season is carried out, the samples should be taken in high or
late summer. Sampling should, however, ideally consider or provide information on variability in the
timing of seasonal development of the zooplankton.
Studies that have the objective of providing information about individual density, biomass and
productivity should at least include samples every second week during the productive period during
the growth season.
NOTE The composition and biomass of the zooplankton community varies widely in the course of the year.
To a great extent, zooplankton overwinters in the form of resting eggs and dormant instars, and to a lesser extent
as active individuals. In the course of the summer in sub polar, boreal or temperate areas, populations grow,
normally reaching a maximum in terms of density and biomass in August until September. Rotifers reach their
maximum density in the spring and early summer. The highest total species diversity is usually found in the mid-
summer and late summer, while samples collected in the spring can provide important information about
individual species (copepods) which have adult individuals early in the season. Adult individuals are often easier
to determine to species level than young individuals.
7.3 Diurnal sampling period
7.3.1 General
Most zooplankton species perform vertical migrations in the course of the day. They are normally found
in the upper part of the water column at night rather than during the day. For studies that involve
comparisons of several water bodies or changes over time (trend monitoring), it is recommended that
samples should be collected at the same time of day in order to reduce variability caused by the
animals’ daily migrations or integrate the complete vertical habitat.
NOTE In marine waters it can be standard to sample at night when the position of migrators is highest in the
water column, for example when the objective is to study a diel cycle on species or populations.
7.3.2 Sample size
Sample size will depend on the aims of the study and the environment under investigation. Estimating
the total density and biomass of zooplankton requires relatively few animals in comparison with
studies of the total species diversity (studies of biological diversity).
Samples should contain a minimum of 300 animals or 100 individuals per each of the three dominant
taxa (for crustaceans: exclusive nauplii) in order to provide a good estimate of numbers and species
composition. If both crustaceans and rotifers are included in the analysis, the samples should contain a
minimum of 200 animals of the group, which has the fewest individuals. Table 3 gives
recommendations of total sample size.
Table 3 — Recommendations of total sample size (may consist of several smaller samples)
Investigation area Vertical net hauls Horizontal net hauls
Waters of high trophic status Whole water column up to 30 m
Waters of moderate trophic status Whole water column 15 m to 20 m
Waters of low trophic status Whole water column 2 m to 10 m
Certain species are normally found in such small numbers (e.g. predators and other large species) that
it is necessary to collect a larger sample (approximately 10 times the volume of an ordinary
zooplankton sample) in order to obtain a good estimate of their numbers.
A net-haul normally contains many more animals than are required for analysis. Before counting and
estimating the occurrence of the more typical species, a representative sub-sample should be analysed
(see EN 17204 [2]).
7.3.3 Geographical localization of sampling sites
Sampling stations should be unambiguously located and in such a way that they can be found
subsequently by other workers. The location of sites should be carried out by means of geographical
coordinates based on a grid reference system (e.g. World Geodetic System: WGS-84) or based on the
Universal Transverse Mercator (UTM) system. Site location should be performed in accordance with
relevant guidelines. The Global Positioning System (GPS) should be used as far as possible for defining
site location.
7.4 Operating the sampling device
7.4.1 Vertical net hauls
The zooplankton can be sampled vertically using a plankton net. The plankton net should be equipped
with a flow counter. The net should be sunk vertically to the desired depth and hauled up again slowly
and smoothly (depending on net type and mesh size). It is important that sufficient material should be
obtained. It may be necessary to make several vertical hauls per sample site. If this is done, the net
should be emptied between each haul.
Vertical net hauls should cover all depths in order to include deep water species. In locations with large
quantities of algae and other particles the net will easily become clogged. In these cases, one should
consider to sample stratified so that the filtered volume for each haul is reduced and quantitative
samples from all depths are gained.
The net weight will be dependent on the design of the net and how it is being used. A net weight should
be added if the angle deviates more than 25° from the vertical. The angle of inclination should always be
recorded. At least distances of 5 m should be pulled. After every sampling the net is to be rinsed
thoroughly from the outside with sea water to rinse the whole catch in the net cup. Information on
correction of depths from wire angles can be taken from Annex C.
For stratified hauls the following intervals should be considered:
— bottom to halocline (included);
— top of halocline to thermocline (included);
— top of thermocline to surface.
If there is no thermocline, the whole water column should be covered.
If there is no halocline, there should be a standard haul of 75 m to the thermocline (included) or to 25 m
if there is no thermocline either.
To control the depth the use of pressure sensors is recommended. In case they are not available, then
the correction should be made as a function of the angle inclination of the winch is determined by
means of Formula (1):
length of line m
[ ]
Depth m = (1)
[ ]
cos angle inclination of the winch
[ ]
With closing hauls only, the part below the closing line is rinsed from the outside with sea water into
the cup at the base (cod-end) of the net.
7.4.2 Horizontal tows/hauls
When sampling in depths of up to 100 m, a ring net sampler [13] can be used. In deeper water, it is
necessary to use a high speed plankton sampler such as a Gulf VII or the slower Bongo sampler. These
should be capable of deployment down to at least 500 m. These samplers generally incorporate
conductivity, temperature, and depth probes (CTDs), and either contain mechanical or electronic
flowmeters to enable the volume of water filtered on each deployment to be calculated. These sensors
either relay 'real time' environmental data back to a shipboard computer display or log the information
ready for downloading once the station has been completed. In either case it is imperative to have ‘real-
time’ monitoring of the depth of the samplers to avoid collision with the sea bed.
Two flow meters are fitted: one mounted inside the aperture (internal) and one mounted on the
sampler frame (external) to measure the volume of water filtered and monitor clogging on each
deployment. Towing speeds depend on the sampler type e.g. it is recommended that a Gulf VII sampler
should be towed at a ships speed of 7,4 km/h to 9,25 km/h; whereas a Bongo sampler should be towed
between 6,5 km/h to 7,4 km/h. An appropriate towing speed for horizontal or oblique tows with a
Multinet will depend on the mesh-size. If towing speeds become too high, bottle effects can be
experienced and increased extrusion of the smallest size organisms due to increased pressure within
the net.
A depth integrated sample should be taken by deploying the Gulf VII or Bongo on a ‘v’ shape dive profile
from the surface to within 2 m of the sea-bed, if bottom topography allows. In deeper water it is
recommended to allow for a greater margin of error.
NOTE Other devices include those which operate using a continuous ribbon of mesh e.g. gauze of silk, which
captures zooplankton (and phytoplankton sequentially). These include the CPR or Longhurst Hardy recorder, see
Annex E.
When large jellyfish appear in the sample, it is recommended to discard the sample and take a new one.
When it is impossible to avoid unwanted jellyfish, they should be rinsed from other mesozooplankton
and then discarded. When applicable, these procedures should be recorded.
When the plankton net has been taken out of the water, all the material hanging on the inside of the net
should be rinsed into the draining cup. The simplest way of doing this is to raise and lower the net
several times through the water surface. In order to empty out animals that remain at the bottom of the
net, water should be poured or hosed over it from the outside, from the top and downwards by use a
hose connected to seawater. The material should then be concentrated on appropriate sieves a
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