|Abstracts on Global Climate Change|
Response of macroinvertebrates to warming, nutrient addition and predation in large-scale mesocosm tanks
Feuchtmayr, H McKee, D Harvey, IF Atkinson, D Moss, B
HYDROBIOLOGIA 584: 425-432
There is increasing concern about the effect of climate change on aquatic systems. We examined changes in macroinvertebrate communities caused by increased temperature (3 degrees C above ambient during summer only and continuous 3 degrees C above ambient all year round), influences of fish (Gasterosteus aculeatus L.) and addition of nutrients ( nitrogen and phosphorus) in 48 large-scale (3000 l) tanks over a 2 year period. While numbers of Isopoda, Chaoborus, Corixidae, Ephemeroptera, Notonectidae and Odonata were reduced by the presence of fish, nutrient addition caused isopods, corixids, mayflies and odonates to increase in abundance. Impacts of temperature increase were surprisingly low, with only gastropods increasing in heated tanks, suggesting that, overall abundances of most macroinvertebrate taxa will not be severely affected by the predicted temperature rise. To determine if taxa were sampled representatively during the experiment, net sweep samples taken towards the end of the experiment were compared with final macroinvertebrate abundances when the complete contents of each tank were harvested. We found that net sweeping is an appropriate semi-quantitative method for most taxa in mesocosm tanks. However, mites, coleopteran adults and larvae, dipterans and Chaoborus were not adequately sampled. This might explain why we could not detect any treatment effects of temperature, fish or nutrients on mites, coleopterans and dipterans and calls for different sampling techniques for these taxa, especially in ponds with vegetation stands.