DEMNA : MacroInvertebrate occurrences in monitored surface water bodies of Wallonia

Study Extent

The current monitoring network is composed of more than 440 sampling stations distributed among the Wallonia. The concerned habitats includes static water masses, canals, and small streams to largest rivers from the hydrographic districts of the Meuse, the Scheldt, the Rhine and the Seine. The current network and method designs were set up in 2005, but the dataset also includes older data coming from different sampling events performed by the hydrobioloy unit at the department for the study of the natural and agricultural environment.

Sampling

The station is theoretically defined as a section of the watercourse equal to ten times the width of the wet bed. The sampling methodology consists of sampling eight different microhabitats characterized by eight substrate-speed couples. In practice, a section of length equal to 10 times the average width of the station often proves to be too short to find 8 microhabitats in narrow streams (in the order of one meter) and too long in largest streams (Several tens of meters). This value must therefore be adjusted to find 8 microhabitats. The substrate/velocity pairs whose surface in the station is <1/20 m² are not sampled. The 8 microhabitats are distributed between lotic zones and lentic zones, between mineral substrates and vegetable substrates, between the bed, the left and right banks. A push net ('Haveneau') is used. It must be solid, with a maximum 500 μm mesh size, frame width of 25 to 30 cm, frame height 20 to 25 cm, net length 50 to 60 cm, apical width of the net from 7 to 10 cm. In order to sample mineral substrates with particle sizes from 0.1 to 100 mm (corresponding to sands, gravels, stones, rollers), the operator in charge of the net sampling places the net against the current and stirs the substrate upstream with the foot on a surface of about 1/20 m² at a short distance from the net. He repeats this operation 5 times for the same type of substrate/velocity pairs, in 5 different places (for example from one bank to the other). To sample the bryophytes, the operator places the push net net in front of the current and treads a foot for about 1/20 m² in order to extract the macroinvertebrates which are then entrained in the net by the current. To sample the roots, heliphytes of the banks and other emerging spermaphytes, the operator, facing the current, shakes the substrate vigorously in the haveneau net, then examines it and detaches the fixed organisms. Three rows of nets will be applied for the roots, the heliphytes of the banks and the other emergent spermaphytes. The mineral substrates with particle sizes from 100 to 250 mm (corresponding to medium stones) are placed in a bucket of water and cleaned by the hand-picker. About ten stones will be sampled, equivalent to about 1/20 m². Large mineral substrates (granulometry higher than 250 mm, corresponding to "blocks", stones that are only possible to lift with two hands) are hand-cleaned in a bucket of water. Two or three blocks according to their size will be sampled, equivalent to about 1/20 m². To sample the immersed spermaphytes, the operator raises a clump of spermaphytes, pulls it out by hand and transfers it to its bucket. By holding the sample in the bucket, the operator expands the tuft into several fragments, shakes each fragment individually and energetically, and detaches the fixed organisms by hand. Net samples, usually composed of a mixture of plants, mineral fragments, and macroinvertebrates, are dumped into a bucket of water once this part of the sampling is completed. The samples taken by hand are directly transferred to a bucket. The solid contents of the buckets are resuspended and removed with a 500 μm mesh sieve. The sieve is then held in a light stream of water to remove the fine elements (vase, fine sand, etc.). Then, the remaining contents of the sieve are introduced into a flask containing about ten centimeters of water. A rapid visual examination can assess the abundance and diversity of macroinvertebrates, the dominant taxa and the probable indicator group. If the sample contains fragile organisms or very small sized organisms (mainly Peloptera and Ephemeroptera), these organisms can be delicately packaged separately, if necessary in ethanol (Fine Shellfish). The taxa observed with a single specimen or supposed to represent the indicator group are possibly isolated in a pill box, placed in the flask. A sufficient volume of water to cover the sample (5 to 10 cm) is added. The sample is fixed by adding 10% of a neutralized solution of formaldehyde and 90% of water, then it is homogenized carefully and delicately. As far as possible, formalin is added using a 50 ml syringe, otherwise by pouring directly. Protected organisms (Astacus astacus, Dytiscus spp, Hydrophilus piceus, Margaritifera margaritifera, Unio crassus, ...) will be carefully recorded on the field protocol in the boxes "other taxa noticed" and returned to the water . For this purpose, a 10 X magnifier is used.

Quality Control

Field operators determine whether the sample could be identified directly after being sorted. Otherwise, the sorting operator stored the sample in alcohol (10% formalin) pending further identification in the laboratory. The final results are only imported into the unit database ('AQUABIO') once the sampling and determination are deemed valid. The samples are then labeled in 40 * 30 * 12 cm red plastic boxes (Manutan reference A025911 or equivalent) and stored permanently in the collection.

Method steps

1. Selecting the sampling area and preparing the route.
2. Selection of substrates to be surveyed by station.
3. Sampling of substrates.
4. Cleaning the sample.
5. Sample conditioning.
6. Post-sampling identifications/verifications and counting.
7. Report writing.
8. Encoding in the Aquabio database.

Freshwater macroinvertebrates from Wallonia. The observations include more than 670 taxa divided between species (more than 240), genus (more than 250) and families (more than 170). Thus, the dataset includes more taxa than expected for the IBGN/IBGA protocols, due to higher identifications and had hoc observations made by the laboratory staff.

1. Animalia
   common name: animals rank: kingdom
2. Arthropoda
   common name: Arthropods rank: phylum
3. Mollusca
   common name: Molluscs rank: phylum
4. Platyhelminthes
   common name: Flat worms rank: phylum
5. Annelida
   common name: Ringed worms rank: phylum
6. Cnidaria
   common name: cnidarians rank: phylum
7. Bryozoa
   common name: Moss animals rank: phylum
8. Porifera
   common name: Sponges rank: phylum
9. Nematomorpha
   common name: Gordian worms rank: phylum
10. Nematoda
    common name: Roundworms rank: phylum

Wallonia, Southern Belgium. Some exceptional data can be found in neighboring regions (Flanders) or countries (France, Luxembourg, etc.).