Ostracod communities associated to aquatic macrophytes in an urban park: the example of the Caffarella Valley (Park of the Appia Antica, Rome, Italy.

The relationship between ostracod and macrophyte communities has been seldom studied, especially in urban parks. The main purpose of this research is to explore such a relationship in the area of Rome, and in particular in the Appia Antica Regional Park (Rome, Italy), to provide information about the environmental characteristics influencing both the assemblages and to document for the first time the distribution of freshwater ostracods in an area inside the city of Rome. The survey has considered different water bodies: springs, channels, ditches and a pond. Chemical and physical parameters were measured during the ostracod sampling in 13 sites during the 4 different seasons. The ostracod assemblage includes 11 species whereas the macrophyte community is formed by 17 species. Their link with the measured abiotic parameters has been studied through several statistical analyses: cluster analysis, non-metric multidimensional scaling and canonical correspondence analysis. The results clearly separate the investigated area in one sector where COD and phosphates are the driving factors and another sector where inorganic nitron ions, pH and conductivity are the main influencing factors. To better understand the ostracod-macrophyte interaction, Spearman rank-order correlation analysis was performed, confirming such a link. Although the macrophyte community is clearly affected by human pressure, the relationship with the ostracod assemblages seems well established and identified by exclusive pairs or groups of species. Among them, the Cypria lacustris-Lemna minuta duo is of considerable importance, being L. minuta an exotic species, known as an invasive weed in some areas of Europe and spread in Italy only recently. The fact that the 13 sites were characterized by different public access regulation has been partially mirrored by both ostracod and macrophyte distribution since the majority of the sites characterised by the highest diversity are those with restricted access. In general, notwithstanding the anthropic pressure, the occurrence of different kinds of water bodies has allowed the development of ostracod and macrophyte associations, which are rarely represented in an urban park.