Effects of Microscale Water Level Fluctuations and Altered Ultraviolet Radiation on Periphytic Microbiota |
| |
Authors: | WE Kahn RG Wetzel |
| |
Institution: | (1) Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0206, USA, US |
| |
Abstract: | Abstract
Microscale fluctuations in water level (1–20 mm) are common on a diurnal basis in shallow (<5–10 cm) wetlands, coupled to
evapotranspiration losses during the daytime in excess of groundwater resupply. These depth variations alter the intensity
of UV irradiance reaching attached periphytic algal and bacterial microbial communities. Effects of alterations of UV irradiance
by micro-changes in water level on periphytic microbiota were examined experimentally. Attached microbial communities, grown
on glass fiber filters in situ in a natural wetland, were exposed experimentally to near-natural levels of UV irradiance of differing spectral quality.
UV intensity was altered by varying the distance of the communities from the light source, changes in UV-attenuating natural
dissolved organic matter (DOM), and small changes in water level (2 or 4 mm). Algal productivity and photosynthetic oxygen
production were significantly reduced by small enhancements of UV-B radiation, by decreased water levels of only 2 mm, and
by reductions in concentrations of DOM. UV-B had only small short-term effects on chlorophyll a, although small increases in water depth and DOM concentration reduced pigment damage. Experimental removal of UV-B during
in situ growth indicated that algae could adapt to UV radiation during growth in natural environments. Microbial oxygen consumption
and bacterial productivity and biomass were also lowered significantly by UV-B exposure, and damage decreased with small (2
mm) increases in water depth or in DOM concentration. Selective inhibitors of algal photosynthesis and production of released
extracellular organic substrates caused a concomitant reduction in bacterial productivity and a significant increase in magnitude
of UV-B damage to bacterial biomass. These effects suggested that metabolic interactions between the periphytic autotrophs
and heterotrophs altered community responses to UV-B radiation. Microscale water level reductions, common on a diurnal basis
in shallow wetlands, and associated increased UV intensity can result in rapid alterations in periphytic metabolism.
Received: 27 January 1999; Accepted: 18 May 1999 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|