Periphyton colonization and changes in the diatom assemblages of an artificial urban pond

Abstract

Artificial ecosystems are sometimes the only opportunity for citizens to experience nature. Maintaining their quality is essential for continuing to enjoy the ecosystem services. We studied an urban pond in the Northwest Iberian Peninsula (Aveiro, Portugal) as a model for testing the suitability of diatom assemblages and indices of water quality in these particular ecosystems. Weekly sampling of three replicas was performed over 28 days on stones and ceramic tiles in a shaded site (Site-SH) and in a sunnier one (Site-SU). The best model of the distance-based analysis included temperature and NH4+as the variables that best explained the diatom assemblages (R 2= 0.43). Chlorophyll-α taken as a proxy for algae biomass, and ash-free dry mass increased until the third week, when a turbid runoff entered the system. After this disturbance, chlorophyll-α increased only at Site-SH (from 14.4 mg m –2 to 62.4 mg m–2); ash-free dry mass increased at Site-SU (from 7.2 mg m–2 to 42.3 mg m–2). The Specific Polluosensitivity Index of the diatoms showed low values below 16 that further decreased with the incubation time. Shannon diversity did not vary between sites, while ANOSIM (analysis of similarity) enabled the identification of differences in the species composition among sites and over time. Cyclotella meneghiniana and Sellaphora nigri were abundant at both sites, but other species showed a prevalence to one of the sites: Nitzschia amphibia and Gomphonema parvulum dominated at site-SH, whereas Amphora pediculus and Grunowia solgensis were abundant at site-SU. This study provides evidence that the use of benthic diatoms is a useful tool for evaluating the ecological potential of artificial ecosystems. Moreover, such systems in the close vicinity of urban areas need better management and monitoring to reduce the risk of deterioration.