Effects of UVB radiation on marine phytoplankton communities

Long-Term UVR Effects Upon Phytoplankton Natural Communities of Patagonian Coastal Waters

“…Studies devoted to evaluate the effects of UVR on phytoplankton communities over long periods of time have highlighted the high variability in responses. Some outdoor mesocosms studies showed little UVR effects on chlorophyll a (Chl a) content (Halac et al 1997;Wängberg et al 1999;Whitehead et al 2000). On the other hand, Forster et al (2001) working with phytoplankton of the Darss-Zingst estuary in the Baltic Sea found higher Chl a concentration in samples that did not receive UVR, as also observed in the experiments www.intechopen.com Long-Term UVR Effects Upon Phytoplankton Natural Communities of Patagonian Coastal Waters 231 carried out by Keller et al (1997) with communities off Narragansett Bay.…”

“…Still, these studies are especially important because they reflect the result of a particular effect caused by UVR as well as potential photoacclimation i.e., short-term experiments frequently overestimate the impact of UVR. One way to evaluate UVR effects on aquatic autotrophic organisms on a long-term basis is by using an "enclosed ecosystem" as a model (named meso-or microcosms, depending on the volume of sample) in which a water parcel is isolated and incubated under conditions similar to those found in the natural environment (Wängberg et al 1996). These setups make feasible to conduct controlled incubations of plankton communities while allowing the manipulation of UVR intensities (i.e., when working with artificial radiation sources) and spectral composition (by covering the containers with different filters / materials).…”

“…At the community level, UVR impact is frequently translated onto changes in the taxonomic composition towards more tolerant species or changes in size distribution. For example, studies carried out by Wängberg et al (1999; found that small phytoplankton were favored by UV-B exposure, and Mousseau et al (2000) reported a shift from diatoms to small naked flagellates that occurred more rapidly under enhanced UV-B than under its natural levels. UVR-mediated community structure shifts may result in an important impact for the whole aquatic system, either by altering the food web structure due to the differential sensitivity to UVR, or by affecting carbon allocation into different biomolecules which in turn is translated into changes of carbon and nutrient cycling in the ecosystem (Mostajir et al 1999;Sommaruga 2003).…”

The effects of ultraviolet radiation on the planktonic community of a shallow, eutrophic estuary: results of mesocosm experiments

“…Daily oxygen production was maximal when incident irradiance was highest, especially at the beginning of Expt III when the lower pH of 9.0 indicated a slightly higher availability of dissolved inorganic carbon than in the other experiments. In another outdoor mesocosm experiment, photosynthetic carbon fixation rates were unaffected by a treatment which enhanced the UV-B fluence rate to twice that of ambient (Wängberg et al 1999).…”

“…However, this effect could not be repeated in the following year. The results of other outdoor mesocosm experiments in an alpine lake (Halac et al 1997), in a mesotrophic lake (Laurion et al 1998) and in a Swedish fjord (Wängberg et al 1999) Fig. 9 Changes in the zooplankton biomass during mesocosm Expt I in 1995 (A) and in 1996 (B).…”