Figure 1.
Human-made, coastal defence infrastructures at Cesenatico, along the Italian shores of the north Adriatic sea.
A) View of the study area and breakwaters from Google Earth. B) View of a breakwater under maintenance (photo L. Airoldi).
Figure 2.
Two-dimensional plots of principal coordinate axes (unconstrained metric multi-dimensional scaling, MDS).
The MDS shows ordination of centroids of assemblages at the landward and seaward sides of replicated control (non-maintained) and maintained (March 2002) breakwaters at Cesenatico in May 2002, August 2002, January 2003 and May 2003. There were 4 control and 4 maintained breakwaters, except for May 2003, when there were only 2 control breakwaters. Analyses were based on Bray-Curtis dissimilarities after 4th-root transformation of cover data. Stress values lower than 0.10 indicate that the ordination is good and that the interpretation of patterns in 2 dimensions is reliable.
Table 1.
Effects of maintenance in relation to the exposure and location of the assemblages on the breakwaters.
Figure 3.
Abundance of most abundant taxa on the study breakwaters at Cesenatico.
Data are average percent covers ±1 SE (n = 32, 8 replicate plots for each of 4 breakwaters; in May 2003 n = 16 for controls, 8 replicate plots for each of 2 breakwaters) of Mytilus galloprovincialis, oysters (a mixture of Ostrea edulis and Crassostrea gigas difficult to separate by visual sampling), macroalgae (mainly Ulva spp., Codium fragile ssp. tomentosoides and filamentous forms), biofilm (a coating of microalgae, juvenile stages of macroalgae and silt) and bare rock (rock non occupied by visible macroscopic forms) at the landward and seaward sides of control (non-maintained) and maintained (April 2002) breakwaters, in May 2002, August 2002, January 2003 and May 2003. Asterisks indicate significant differences between assemblages on maintained and control breakwaters as indicated by a posteriori SNK tests.
Figure 4.
Two-dimensional plots of principal coordinate axes (metric multi-dimensional scaling, MDS).
The MDS shows ordination of centroids of assemblages at the landward and seaward sides of each of 3 breakwaters for each time of disturbance (D1 = April 2003, D2 = August 2003, D3 = January 2004, C = unmanipulated plots). Analyses were based on Bray-Curtis dissimilarities after 4th-root transformation of data collected in May 2004. A Stress value of 0.05 indicates that the ordination is excellent and that the interpretation of patterns in 2 dimensions is highly reliable.
Table 2.
Effects of disturbance applied at different times and in relation to the exposure and location of the assemblages on the breakwaters.
Figure 5.
Abundance of macroalgae in the experimental treatments at Cesenatico.
Data are average percent covers ±1 SE (n = 36, 4 replicate plots for each of 4 blocks for each of 3 breakwaters) of macroalgae (mainly Ulva spp. and Codium fragile ssp. tomentosoides) at the landward and seaward sides of breakwaters for each time of disturbance (April 2003, August 2003, January 2004, Control = unmanipulated plots).