Print PageTerrestrial and aquatic systems are linked through an exchange of energy and materials. Despite this, many studies of vernal pools and other temporary wetlands have only focused on within-pool conditions, such as hydroperiod, water chemistry, and the presence of predator fauna. However, canopy cover may also influence wetland organisms, as it can regulate water temperature, as well as plant and algal productivity. Recent studies of vernal pool amphibian communities have noted that some species prefer open canopy habitats, but the large macroinvertebrate communities have not been investigated. In a 2009 field study, we observed that macroinvertebrate biodiversity increased with decreased canopy cover. We further investigated this relationship in 2010 by creating artificial wetlands (mesocosms) with known organism communities and different levels of canopy cover. The wetlands were created using 416L cattle watering tanks with mesh lids made from variable levels (30, 55, and 73%) of shade cloth. The macroinvertebrate assemblages were determined by surveying 10 local vernal pools to ascertain what invertebrates are present in these wetlands and how their communities are structured. Throughout the 12-week experiment, we measured macroinvertebrate biodiversity, zoo- and phytoplankton abundance, water quality, and how these factors changed through time.
Results/Conclusions
Several organisms reproduced in the artificial wetlands, including snails, fingernail clams, and aquatic beetles. Water conductivity and temperature were highly correlated with invertebrate diversity, however, these effects were the most pronounced in the low canopy tanks. In particular, wetlands with only 30% canopy shading had the greatest abundance and diversity of macroinvertebrates, as well as the warmest water temperatures and highest conductivities. Phytoplankton biomass also tended to be lowest in the 30% treatments; however, this may be an indirect consequence of high snail productivity in these wetlands. Repeated measures ANOVA indicated that temporal patterns in the number of macroinvertebrates and water conductivity differed among the shade levels. This work clearly demonstrates that canopy cover influences macroinvertebrate biodiversity, as the number of organisms and families were consistently greater in the 30% shade treatments. Water conductivity was also influenced by canopy shading and may be a consequence of organism activities or photodegradation of leaf litter in the tanks. Altogether, this work suggests that canopy cover can greatly influence macroinvertebrate diversity in temporary wetlands by modifying both the physical and chemical components of these habitats.
