Fish-trematode systems as indicators of anthropogenic disturbance: Effects of urbanization on a small stream

VERONICA TAGLIORETTI; ROSSIN, M.A.; JUAN T. TIMI

ECOLOGICAL INDICATORS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 93 p. 759 - 770

1470-160X

Parasites have proven to display high responsiveness to anthropogenic stress, having, therefore a considerablevalue as bioindicators. We analysed the variability in the structure of parasite populations and assemblages of thepoeciliid Cnesterodon decemmaculatus caught at partially urbanized stream along a unidirectional gradient withthe aim of evaluating their utility as indicators of the effect of urbanization. A total of 209 fish were examinedfor parasites; some physical parameters of the stream, including the percentage of urbanization (UR) were alsorecorded. Data were analyzed at the levels of parasite populations and assemblages discriminated by host sex.Fish condition factor was negatively affected by UR, possibly related to flashing hydrology, but it was not relatedto parasite abundance. Different combinations of variables explained the distribution of parasite populations andassemblages along the creek, with UR being recurrently identified among the best predictors of parasite loads atall levels of analyses. Whereas densities of mollusc first intermediate hosts were considered of little relevance forparasite distribution, distribution of definitive hosts, as well as the presence of pollutants and increased flashinessin urbanized sections of the creek were retained as possible explanations to the observed patterns. As thesefactors can act simultaneously, the mechanisms driving differences in parasite dynamics of urban streams aredifficult to individualize, but the effect of urbanization on both hosts and parasites was clearly identified. Parasitesfound, with abundances clearly related to UR, can be considered as good ecological indicators, since theyare broadly distributed in the region, easy to observe and count, their prevalence and abundance allow reliablequantitative comparisons and are sensitive to variations of environmental stress and/or ecological conditions atsmall spatial scales. Consequently the susceptibility of fish-trematode systems to variations in both biotic andabiotic stressors makes them a promising tool for detecting urbanization-related disturbances in streams.