Data collection mastic asphalt

Experiment at NIOZ Yerseke

Monitoring has taken place over the course of one year, roughly once every three months (table 1). During monitoring, species were determined for biodiversity measures and pictures were taken for detailed determination of coverage. Determination of species and coverage was done visually by the same individual to prevent differences due to changing observers. When uncertain about species, they were double checked by species experts from Stichting Anemoon. Most macro algae species were not determined to species level due to difficulty of determining the differences with juveniles and due to later photograph based analyses where details cannot be observed. Ulva sp. includes both Ulva intestinalis (gutweed) and Ulva lactuca (sea lettuce). The Porphyra (red algae) species identified were most likely Porphyra umbilicalis. Only Fucus vesiculosus (bladder wrack) was identified at the species level due to clear distinction from the other Fucus species, especially in a later stage in monitoring.
Common fauna species were determined to species level: Elminius modestus (the Australasian or New Zealand barnacle; currently named: Austrominius modestus), Littorina littorea (winkle) and Mytilus edulis (mussel).
Coverage determined from photographs was set at a maximum of 100% per tile. Thus flora species overlapped by other flora species will not be identified in coverage per species when not visible on the analysed photographs (Vergouwen et al. 2017).

Table 1: Monitoring data at Yerseke
Time (T)	Date	Month
T0	16 December 2015	0
T1	15 March 2016	3
T2	13 May 2016	5
T3	20 September 2016	9
T4	24 November 2016	11

Field experiment at 'De Val'

The different mastic asphalt surface types were monitored by taking and analysing photographs, and by manual inspection of flora and fauna during transect surveys (table 2). Detailed photographs of quadrants along a transect we taken shortly after, and six and nine months after the application of asphalt. Photographs of the more general and large scale spatial coverage were also taken six and nine months after the application of asphalt. Manual inspection of quadrants along a transect was conducted once, six months after the application of the asphalt .

Table 2: Monitoring at De Val (Zierikzee).
Date	Activity 1	Activity 2	Activity 3
1st week dec 2015	Application of asphalt
17 dec 2015 (T0)	Quadrant photos	-	-
20 jun 2016	-	-	FF - transect survey
28 jun 2016 (T1)	Quadrant photos	Spatial coverage photos	-
22 sep 2016 (T2)	Quadrant photos	Spatial coverage photos	-

In the middle of every section photos were taken of a quadrant of 50 x 50cm at 2m and 4m from the top of the section along a transect line. To be able to consistently take the photos of the same area of the dyke, the top of a transect was marked with blue paint. One transect was used per section of substrate treatment, but because there was only one treatment with oyster shells as the substrate, two transects were used in the same section. Every transect always began at the same height of Nap +1,5m. Photos were used to illustrate the colonization of the algae in detail, and to study the treatments, i.e. the degradation of the treatment material.

To get a full image of every section a dSLR camera was mounted to a 4m long “selfie stick” and a photo was taken of every 2m which overlaped the former photo by 60%. This way it is possible to stitch the images together to get full images of every section. Most macro algae species were not determined to species level due to difficulty of determining the differences with juveniles and due to later photograph based analyses where details cannot be observed. Ulva sp. includes both Ulva intestinalis (gutweed) and Ulva lactuca (sea lettuce). The Porphyra species identified were most likely Porphyra umbilicalis and Fucus was most likely Fucus vesiculosus (bladder wrack). Because of the different colours of Ulva sp. (green) and Fucus sp. (brown) and Porphyra sp. (red) it was possible to use an image color classification in ArcGis to classify the different algal species and thereby calculate an estimated coverage percentage per species from photographs. When combined with height information coverage can also be linked to inundation time.

Flora and fauna transect surveys were carried out in the field to be able to compare species distribution per section and per 50 cm height class. The presence and abundance of flora and fauna was recorded using the Braun-Blanquet cover-abundance scale. This method involves a semi-quantative visual estimation of the coverage or abundance of organisms using an abundance code which is later interpreted into quantitative data. The Braun-Blanquet cover-abundance method is an efficient and sufficiently accurate technique to gain information on abundance and vegetation coverage in the field (Wikum & Shanholtzer, 1978) (Vergouwen et al. 2017).

Referenties

Ecological potential of mastic asphalt for rich revetments, Vergouwen, S., A. van den Brink, L. van Duren, Deltares/HZ, juni 2017.
Application of the Braun-Blanquet cover-abundance scale for vegetation analysis in land development studies, Wikum, Douglas A. and G. Frederick Shanholtzer, juli 1978.

Data collection mastic asphalt

Experiment at NIOZ Yerseke

Field experiment at 'De Val'

Zie ook