Beach nourishment and groynes building were
implemented to counteract erosion in sandy beaches
located at San Rossore natural park (Tuscany, Italy), near
the mouth of Arno river. From 2000 to 2003, nine groynes
were built along 3.6 km of coastline at intervals of ca.
400 m, and two of the eight beach segments were Wlled
with marble gravel. Here, we analysed the eVects of these
beach changes on the abundance and behaviour of the
amphipod Talitrus saltator, using Weld and laboratory
observations. Sampling with pitfall traps in order to use the
capture frequency as a proxy of abundance was performed
bimonthly from September 2004 to January 2006, and
orientation experiments were carried out in autumn (2004
and 2005), and spring and summer 2005. Physical variables
(beach width, swash width, beach slope, sand penetrability,
mean grain size and salinity) were also recorded. The
abundance of T. saltator increased with the distance from
the river mouth, towards sites with: negligible amounts of
marble locally used for nourishment; higher beach width
and salinity; lower slope and penetrability values; medium
grain sizes, and during the spring/summer seasons. A Generalized
Linear Model with a predictive power of 64.5%
considered three main descriptors in the model as signiWcant:
distance from the river mouth, sand penetrability and
a seasonal factor. Orientation experiments showed a highly
variable behaviour among sites, depending on coastal
stability: at the site stabilized by the concurrent actions of
nourishment and groynes protection measures, sandhoppers
were oriented to the shoreline direction by using a sun
compass; alternatively, at a site situated only 2 km from the
nourished sites, they showed scattered orientation. These
between-site diVerences in orientation, described through
Spherically Projected Linear Models, were consistent
throughout the study period. DiVerent responses obtained at
the individual (orientation) and population (captures) levels
stress the need to account for several bioindicators to characterize
biotic responses to both natural and anthropogenic
changes in sandy beaches
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