monitoring shoreline armouring (Scyphers et al., 2014).
As in other countries, shoreline hardening is expanding along
the coast of Chile (Chilean Ministry of Public Work, MOP, and see
Fig. 1). Most artificial structures are part of urban areas or incorporate
public accesses that facilitate the use of shorelines for activities
such as recreation or fishing. The purpose of this study was
to examine if the abundance of AL is higher on urban coastal
breakwaters than on adjacent, natural rocky platforms, and to
determine if the structural complexity characteristics of both natural
and artificial habitats influences AL distribution on them. We
hypothesized that AL is more abundant on urban breakwaters
compared with adjacent natural rocky platforms, following differences
in patterns of structural complexity between habitats. Coastal
human population density is commonly expected to contribute to
an increase of AL accumulating in natural habitats nearby, with
breakwater spatial extension potentially being directly related to
the total accumulation of AL. Hence, we also examined the relationship
between total AL density in breakwaters and local human
population density and/or breakwater length.