How the diversity of constructed wetlands improves the plankton communities discharged into a protected Mediterranean wetland

Constructed wetlands (CWs) are created to enhance wildlife and improve water quality. These services are especially relevant when the CWs are linked to a natural wetland. The CWs effectiveness in improving water quality has been demonstrated, but their role in enhancing the plankton biodiversity discharged into the wetland has not. To assess this, we analysed the plankton community of three structurally different CWs created within a protected Mediterranean wetland ( Albufera de València Natural Park) over two years (2014–2015). We hypothesize that alpha-diversity in the inlet communities (a species mix from anthropically disturbed environments) will be higher than those from inner and outlet sites where natural assembly processes occur, and the beta-diversity of the Natural Park will increase due to the different communities found within and between the CWs. The first hypothesis was only partially supported: in two CWs the diversity decreased due to the loss of chlorophytes and cyanobacteria, or the dominance of large copepods or cladocerans. However, when organisms in the inlet bloomed, the emerging assemblages within the CW increased the diversity, as occurred in the third CW. The species of the resulting communities were indicative of improved water quality. The second hypothesis was also proved: the CWs contributed to beta-diversity as they functioned as generators of communities. Within the CWs, vegetation and sediment supplied benthic species to the water column. Communities being discharged into the wetland were much more dissimilar than those arriving in the CWs. Therefore, the wetland assemblage beta-diversity increased thanks to the diversity of CWs.