10) In our case, in the artificial dune zone, the presence of large geotubes and the amount of disrupted textiles found in the supralittoral zone (see Fig. 1b) led us to hypothesise that amphipods could not burrow in this zone and might therefore avoid this area whenever they needed to recover the optimal zone on the beach.
Accordingly, it is not surprising that the lowest number of individuals in the artificialised area in comparison to the reference one was found both in the spring and summer 2010 sampling periods.
Indeed, statistical tests detected differences in T. saltator densities especially during the warmer season, when this species recruitment occurs on the Western Atlantic coast while during the cooler period (autumn 2010 and winter 2011)
almost no individuals were recorded at either site (Fig. 2d).
Thus, successful employment of artificial dunes in this system could jeopardise the presence of this supralittoral species in this site.
11) Therefore, such behavioural changes linked to the artificial dune zone could be well suited as an early warning signal for wider negative ecological impact (as demonstrated by reduced densities of T. saltator in this zone).
This finding makes this species suitable as a baseline indicator of habitat degradation, given its sensitivity to physical variation in the beach and dune ecological conditions as demonstrated here.
Our results reinforce the notion that T. saltator could be used as a bioindicator of human changes on sandy beaches.