Threats to marine ecosystems include habitat destruction and degradation of water quality, resulting
from land- and ocean-based human activities. Anthropogenic input causing modification of water
quality, can affect primary productivity and thus food availability and quality for higher trophic levels.
This is especially important for sedentary benthic intertidal communities, which rely on local food
availability. We investigated the effect of urbanization on the dietary regime of four species of intertidal
filter feeders (three barnacles and one mussel) at sites close to high-density cities and at sites far from
heavily urbanized areas using fatty acid and stable isotope techniques. d15N was significantly higher at
urbanized sites compared to their corresponding control sites for all species with few exceptions, while
no effect on d13C was recorded. Barnacle fatty acid profiles were not affected by cities, while mussels from
sites close to cities had fatty acid signatures with a higher proportion of polyunsaturated fatty acids
(PUFA). We suggest that the enrichment in d15N at urbanised sites reflects the influence of anthropogenically
derived nitrogen directly linked to wastewater input from domestic and industrial sewage.
Linked to this, the high proportion of PUFA in mussels at urbanized sites may reflect the influence of
increased nitrogen concentrations on primary production and enhanced growth of large phytoplankton
cells. The results indicate that anthropogenic effects can strongly influence the diets of benthic organisms,
but these effects differ among taxa. Changes in the diet of such habitat forming species can affect
their fitness and survival with potential effects on the populations associated with them