The benthic communities of the Wadden Sea comprise about 400 species, of which some 150 live in the littoral area. Benthic macrofauna is less diverse than the benthic meiofauna which counts aver 1200 species.
Input of nutrients, heavy metals and organic micro-pollutants as well as solid wastes are considered to affect the chemistry of the soils, sediments and the water column, the natural biological processes, the individual species and the communities of the Wadden Sea ecosystem.
Monitoring of macrozoobenthos is carried out with the objective
Other anthropogenic influences have to be taken into account when assessing the changes in macrozoobenthos (e.g. by establishing reference areas where human interferences are kept to a minimum). Furthermore, the efficiency of policy targets on the reduction of nutrients has also to be documented by monitoring the macrozoobenthos.
The monitoring can be performed at three different spatial scales:
a. Small scale
Zoobenthos communities at selected stations/transects on intertidal flats: gives information on the seasonal and small scale changes of the communities and selected species
b. Middle scale
Distribution of biotopes/communities within one tidal basin (subtidal and intertidal parts): gives information on the representativity of the permanent stations selected under a. within a larger area). At least one tidal basin per region (NL-west, NL-east, Nds., SH, DK) should be selected taking into account also the watersheds (as important areas for birds).
c. Large scale
Distribution of biotopes (location and area) in the whole Wadden Sea area (intertidal flats): gives information on changes (decrease or increase) of different biotopes on intertidal flats (using remote sensing techniques).
As a minimum program (first step/starting point), only the first type of monitoring (a.) is being carried out: soft bottom macrozoobenthos at selected stations/transects on intertidal flats. This guideline refers to this type of monitoring only. For monitoring of blue mussels, see respective guidelines.
WSP
HD
Macrozoobenthos species as characteristic species of habitat types. Favorable conservation status of habitat types:
Article 11 Surveillance of conservation status of habitats and species
Article 17: Assessment, monitoring and reporting
WFD
Article 8
Annex V, Chapter 1.2.3 and 1.2.4: Morphological conditions
OSPAR
OSPAR Common/Comprehensive procedure
JAMP Eutrophication Monitoring Guidelines: Benthos (1997)
JAMP Theme B. Biological Diversity and ecosystems
OSPAR List of Threatened and/or Declining Species and Habitats
For the TMAP, the macrozoobenthos is defined as that part of the soft bottom fauna which is retained on a sieve with a mesh size of 1 x 1 mm.
[to be amended]
Long-time series in the Wadden Sea during the last 30 years have proofed their value in indicating changes in species composition and biomass although large inter-annual fluctuations have occurred (e.g. due to high spatfall of bivalves) (QSR 2004) and regional differences were observed. The existing time series should be continued with an annual frequency at locations representative for a specific Wadden Sea region (or water body) and, if necessary, supplemented with locations monitored every 3 years to assess the macrozoobenthos development for a larger area (entire tidal basins or water body).
(Table 5.1) Parameters with monitoring locations and frequencies and the relation to the other monitoring requirements.
| Parameters | Description | Location | Frequency | Method | WFD | BD/HD | OSPAR | OTHER | Remark |
| Mandatory TMAP parameters | |||||||||
| Abundance (macrozobenthos) | Number of individuals per species per m² | 1 – 2 transects per region | 1/y,to 3 y | X | X | X | - | - | |
| Biomass (macrozoobenthos) | g AFDW per m² | 1 – 2 transects per region | 1/y,to 3 y | X | X | X | - | - | |
| Species composition (macrozoobenthos) | Number of species | 1 – 2 transects per region | 1/y,to 3 y | X | X | X | - | - | |
| Optional TMAP parameters | |||||||||
| Age (macrozoobenthos) | Age frequency distribution for selected species | 1 – 2 transects per region | 1/y,to 3 y | X | X | X | - | - |
Remarks:
* Contribution to assessment of favorable conservation status of habitat types.
5.1 Parameters
The following parameters of macrozoobenthos shall be monitored:
As a voluntary parameter, the species distribution pattern of the macrozoobenthos should be determined if the sampling strategy allows this analysis. Furthermore, additional interpretation parameters should be measured to enable proper documentation and interpretation of the macrozoobenthos monitoring data.
a. Geographical information
b. Sediment characteristics
During zoobenthos sampling, a small corer sample has to be taken for determination of the sediment characteristics:
c. Weather conditions
The relevant information on the weather conditions should be taken from relevant meteorological reports.
d. Other information
Other relevant information on human use and associated disturbances (e.g. fishery) since the previous sampling occasion has to be compiled.
Sampling strategy
Different sampling strategies can be followed depending on the actual characteristics of the sampling site.
From a statistical point of view, a (stratified) random sampling strategy for monitoring changes in macrozoobenthos is more appropriate. For consistency with already existing long-time series, the sampling strategy at long-term stations/ transects should be kept unchanged if the statistical power is sufficient.
In the already existing programs, such as initiated by the COST 647 program, the following sampling strategies have been used under the assumption that changes which occur in a tidal basin can be observed when sampling on permanent plots or transects:
For each station, it should be checked regularly whether the existing strategies are still appropriate or have to be modified e.g. by analyzing the species-density curves. For details see Annex 2 of the Final Report of the Workshop Benthos/Fish (Marencic et al. 1996).
Sampling instruments and sample size
For intertidal areas, a cylindrical hand-operated corer should be used. The surface area covered by the corer and the number of replicates to be taken is dependent on density and distribution patterns of macrozoobenthos at the sample stations. The relative sampling error can be assessed for different corer sizes and the number of replicates (Essink & Tydeman 1991), and thus be optimized. It is recommended
Sampling depth
Preferably 30 cm deep cores have to be taken. If the sampling depth is not more than 20 cm, it has to be considered that an underestimation of the larger and deeper living specimen may occur, such as Mya arenaria and Arenicola marina. Alternatively, for large species that occur in low density, surfaces of 0.5 m2 may be dug out to a depth of 30 - 40 cm.
Treatment of samples
In general, each sample should be sorted, counted and analyzed separately as far as possible. Pooling of samples before sieving, will decrease the possibilities for statistical analysis and has to be taken into account.
a. Sieving
Sieving in the field should be done with a mesh size of 1 mm. In estuaries, where fine sediment is dominating, a mesh size of 0.5 mm may be appropriate. The use of sieves with round meshes instead of square meshes could be an improvement and should be tested by intercalibration experiments. The sieving of the sample has to be done carefully in order to avoid damage of fragile animals. Visible fragile animals shall be hand-picked during sieving; stones and big shells should be picked out to avoid grinding effect.
b. Fixation
The following methods for fixation of the sieve residues may be used: • buffered 4% formaldehyde solution in seawater (HELCOM 1988) • buffered 4% formaldehyde solution in seawater, followed by storing in deep freezer (Salonen & Sarvala 1985)
Analytical procedures
Preferably, each sample should be analyzed separately. Pooling of samples may be necessary for biomass measurements of small species (to be regarded during the statistical analysis).
a. Sorting and enumeration
The samples shall be washed in the laboratory over a 0.5 mm sieve to remove retained silt and sand. The fixed samples should be washed with tap water thoroughly to avoid human exposure to formalin vapor (appropriate ventilation is necessary).
b. Biomass
For each species and year-class (if analyzed), the biomass shall be determined as ash-free dry weight (AFDW). In addition, biomass bases on dry weight and wet weight can be delivered.
Recommended methods (HELCOM 1988, Essink 1989, Marencic et al. 1996):
AFDW should be estimated after measuring dry weight. It is determined after incineration at 500 - 520 °C in an oven until weight constancy (depending on sample and object size). Check temperature in the oven because temperature gradients can occur (up to 50 °C).
The temperature should not exceed 550 °C since then a sudden loss of weight may happen due to the formation of CaO out of the skeletal material of many invertebrates (can reduce the weight of the mineral fraction by 44%). Before weighing, the samples must be kept in a desiccator while cooling down to room temperature.
Dry weight should be estimated after drying the fresh material at 60 - 65 °C (or by freeze drying), until constant weight is reached.
If necessary, wet weight is obtained by weighing after external fluid has been removed by blot-ting with filter paper. Animals with shells are generally weighed with their shells. Tube-building animals have to be weighed together with their tubes (HELCOM 1988).
c. Calculations
The number and biomass (as AFDW) of species and year classes shall be calculated per square meter.
If only dry weight is being measured, the use of proper conversion factors has to be ensured.
Furthermore, based on these data, the following parameters have to be calculated:
The sampling shall be performed twice per year during low tide:
The exact sampling time depends on the general seasonal cycle of the macrozoobenthos at the respective locations.
For details see [Table 5.1].
The assessment is based on the TMAP hypotheses which have to be further specified if necessary. Based on this, statistical tools have to be elaborated and tuned with the development in the WFD, which has not yet been finalized for the macrozoobenthos assessment tools (Scholle & Dau 2007).
The assessment covers:
With regard to the analysis of changes within the zoobenthos, the relevant monitoring data on nutrient concentration, phytoplankton, contaminants in water, sediment and biota have to be available (see under the respective guidelines).
With regard to zoobenthos, the raw data (number and biomass of each separately analyzed sample) and the calculated data (per square meter) should be stored in electronic data files, so that they can be delivered to the national data base together with information on used methods and any other information relevant for an ultimate assessment of the data. The data should be reported annually to the national databases in coordination with the regulations at the national level.
The national data bases have to make all data, relevant for the TMAP, available to the respective trilateral group which is responsible for the trilateral assessment. This also covers information, e.g. on nutrients, phytoplankton, contaminants, and other anthropogenic influences. The managers of the national data bases are also responsible for the quality of the filed data, and the complete and timely submission to the trilateral level (according to regulations on the national level).
A trilateral data exchange format, as well as a trilateral data catalogue system and a trilateral networking structure are under preparation. The ongoing work of ICES and OSPAR will be taken into account.
The trilateral evaluation of the monitoring data will be performed by the responsible trilateral groups at least every third year as part of the Quality Status Report of the Wadden Sea.
With regard to the elaboration of quality assurance (QA) procedures, the developments within ICES and OSPAR has to be followed (ICES 1994, OSPAR 1997).
Effectively, the QA program should ensure that the data is suitable for the purpose for which it has been collected for, i.e. that they satisfy detection limits and levels of accuracy compatible with the objectives of the monitoring program.
Appropriate QA schemes should be established before the onset of surveys. It is particularly important that adequate resources are allocated for these purposes (e.g. when co-operative studies, involving several institutes, are to be conducted, or when the data is being archived centrally).
The recommendation made in the report of the ICES/HELCOM WG QA on benthic parameters (ICES 1994) and on biological measurements (ICES 1996) should be followed.
Each monitoring institute is requested to take part in regular intercalibration exercises. A system of certifications has to be developed.
The latest taxonomic literature should be used. A list of the taxonomic literature used should be enclosed, when delivering data.
Danmarks Miljøundersøgelser (DMU, NERI)
Landesbetrieb für Küstenschutz, Nationalpark und Meeresschutz (LKN)
Nationalparkverwaltung Niedersächsisches Wattenmeer (NLPV)
Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz (NLWKN)
RWS Rijkswaterstaat Waterdienst
Nederlands Instituut voor Onderzoek der Zee (NIOZ)
Alfred-Wegener Institut für Polar- und Meeresforschung, Wattenmeerstation Sylt
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