Survival and vertical distribution of macroinvertebrates during emersion of sandy substratum in outdoor mesocosms
Poznańska-Kakareko, Małgorzata; Budka, Marta; Żbikowski , Janusz; Czarnecka , Magdalena; Kakareko , Tomasz; Jermacz, Łukasz; Kobak, Jarosław
published: Apr 1, 2017
published online: Mar 13, 2017
manuscript accepted: Feb 28, 2017
manuscript received: Jan 9, 2017
ArtNo. ESP141019001003, Price: 29.00 €
Abstract Benthic invertebrates in shallow or near-shore waters experience emersion during water-level fluctuations. Such events are expected to be increasingly frequent due to climate change and anthropogenic impacts on water resources. Therefore, the research on macroinvertebrate responses to these disturbances in different water bodies and climate zones is needed to understand contemporary aquatic ecosystems. We used 6 outdoor mesocosms to study the survival and vertical distribution of macroinvertebrates (mainly chironomids, oligochaetes, sphaeriid clams) from sandy, near-shore benthic sediments during a 27-day substratum drying event in summer. We also determined the rate of substratum drying in outdoor conditions. Each mesocosm comprised 15 cm of sandy substratum and inhabiting macroinvertebrates. Three mesocosms gradually dried for four weeks in outdoor conditions and three others had a constant water level. The chironomid Stictochironomus sticticus and the oligochaetes Psammoryctides barbatus and Tubifex newaensis were the most resistant to substratum drying, surviving 24, 21 and 12 days of emersion, respectively. Far less resistant species were: Cladotanytarsus mancus group (Chironomidae) as well as Paranais simplex and Potamothrix moldaviensis (Oligochaeta) which survived 3, 3, and < 3 days of emersion, respectively. Only some oligochaetes were noted deeper in the drying mesocosms than in the control treatment. Emersed, sandy near-shore sediments dried out slowly: the water content in the surface 2.5-cm layer was reduced from 16.3 to 2.6 % within 27 days. The rate of drying depended on atmospheric conditions (rain increased humidity, which in turn increased sediment water content). Slower drying is less harmful for benthic macroinvertebrates as some of them can survive as long as the emersed substratum is moist. Nevertheless, prolonged emersion affects negatively these resistant macroinvertebrates even when a relatively high substratum saturation is sustained. In the future, water level fluctuations and substratum drying are expected to play an increasingly important role in the functioning of water bodies. Our research could be helpful in prediction and/or preventing environmental losses caused by this phenomenon.