Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Ecological analysis of Humidur® coatings (October 12 th 2010)

Part 2 : Sample recovered from a highly brackish en vironment (canal)

Prof. Johan Mertens Dr. Lynda Beladjal

Ghent University Biology Department

Terrestrial Ecology Unit K.L. Ledeganckstraat, 35

9000 GENT

Email : Johan.Mertens@UGent.be Lynda.Beladjal@UGent.be

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Location Scheldt-Rhine junction, Zandvliet ( Belgiu m ) .

The sample was taken on the Canal of the Scheldt-Rhine junction on Belgian territory. The piece was cut out on Monday the 11th of October 2010. The water of the canal is salty. The coating was applied in 1989 and has consequently been exposed to the aquatic environment of the canal for more than 20 years.

1. The Humidur coating is completely covered with a heterogeneous substrate, ± 5 to ± 20 mm thick (Fig. 1), consisting of heterogeneous formation of biocomponents (see item 3), filled in with an abiotic fraction (item 2).

2. The abiotic fraction consists of sand grains and clay. This fraction is glued to the

loose formation of biocomponents (item 3).

3. Components of the formation of biocomponents :

3.1. Calcium tubes of tube worms (Serpulidae, Polychaeta) (Fig. 1, Fig.3) constitute a hard three-dimensional plaiting that is durably glued to the Humidur coating, causing the covering to be lasting and not to come off physically (can only be removed chemically by lowering the pH). From this fact alone it can already be deduced that Humidur is an inert material without any signs of wear, but also without anti-fouling characteristics. This explains the durable adhesion of the tubes. Between and on the tubes, the other biocomponents settle (see below), as well as the abiotic fraction.

3.2. Hydrozoa tubes of monkey hair (Cordylophora caspica). They are

comparatively little abundant and constitute a finer plaiting between the calcium tubes and also directly across the Humidur coating (Fig. 3, Fig. 4). These thread-shaped structures (hydrorhiza) stay present for years on end as a fouling component after the polyps have died off . Their adhesion to the substrate is durable, consequently the covering is resistant and does not let off easily. From this fact too, it can be deduced that Humidur is an inert material without any signs of wear.

3.3. Barnacles (Cirripedia : probably Balanus crenatus) constitute randomly spread aggregates (Fig. 1, Fig. 5) which can stick out up to ± 10 mm above the substrate. The cause the substrate thickness to be heterogeneous (item 1). After they have died off, they stay anchored to the substrate for a long time. After artificial removal in the laboratory, the basal plate stays glued to the Humidur coating (Fig. 6). From this fact too, it can be deduced that Humidur is an inert material without any signs of wear.

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

4. Interstitial biocoenosis (organisms living together between the adhering components described in item 3).

4.1. Crustaceans (Arthropoda) two types of small crustaceans (the amphipod

Orchestia gamarellus and the mud shrimp Corophium volutator) and many copepods (Harpacticoida).

4.2. Diatoms . Different types of flora next to other types of unicellular phytoplankton

(Fig. 7).

5. Thin continuous basal layer (± 50 µ) on the Humidur-coating (item 6). It consists of a very dark organic amorphous debris and unicellular ‘algae’ (Fig. 8a-c).

6. The complete fouling-community, as described in items 1 to 5, adheres to a stable

and intact Humidur coating . It constitutes a continuous solid covering layer on the non-oxidized steel (Fig. 9). Macro- and microscopic observations show that there is no damage at all to the Humidur coating nor any damage that could have been inflicted by microbial corrosion (bacterial and fungal) nor by any macrobial deteriorating effect (impact of animal or vegetable origin). The adhesion of the Humidur coating to the steel surface is solid and continuous.

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Figure 1. Survey of the substrate covering. a: abiotic fraction ; b: tubes of tube worms ; c: barnacles

Figure 2. sandy abiotic fraction and remainders of shells and tube worms

of the biotic component

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Figure 3. three-dimensional plaiting of calcium tubes of tube worms a: worm tube ; b: thread-shaped structures (hydrorhiza) of Cordylophora caspica (monkey hair).

Figure 4. prepared thread-shaped structures (hydrorhiza) of monkey hair Cordylophora caspica

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Figure 5. aggregate of barnacles’ shells (died off).

Figure 6. basal plate of a barnacle

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Figure 7. diatoms (blue-green algae) on a fragment of Cordylophora

Figure 8a. Basal layer of very dark organic amorphous debris and unicellular ‘algae’ on the light-green Humidur coating.

Terrestrische Ecologie K.L. Ledeganckstraat 25 9000 Gent

Figure 8b, c. Microscopic preparation of the unicellular ‘algae’ on the Humidur-coating. b: small enlargement, c: strong enlargement of the most dominant type of algae.

Figure 9. slantwise cutting through the ‘Humidur-steel’ sample with a : basal layer of dark-green organic amorphous debris and unicellular ‘algae’b : Humidur coating c: stainless steel