Effects of macrophyte species richness on wetland ecosystem functioning and services

Wetlands provide many important ecosystem services to human society(1-5), w hich may depend on how plant diversity influences biomass production and nu trient retention(4,6-8). Vascular aquatic plant diversity may not necessari ly enhance wetland ecosystem functioning, however, because competition amon g these plant species can be strong, often resulting in the local dominance of a single species(4,9). Here we have manipulated the species richness of rooted, submerged aquatic plant (macrophyte) communities in experimental w etland mesocosms. We found higher algal and total plant (algal plus macroph yte) biomass, as well as lower loss of total phosphorus, in mesocosms with a greater richness of macrophyte species. Greater plant biomass resulted fr om a sampling effect; that is, the increased chance in species mixtures tha t algal production would be facilitated by the presence of a less competiti ve species-in this case, crisped pondweed. Lower losses of total phosphorus resulted from the greater chance in species mixtures of a high algal bioma ss and the presence of sago pondweed, which physically filter particulate p hosphorus from the water(2,10,11). These indirect and direct effects of mac rophyte species richness on algal production, total plant biomass and phosp horus loss suggest that management practices that maintain macrophyte diver sity may enhance the functioning and associated services of wetland ecosyst ems.