A synthesis on UVR biological effects research in the water column of Potter Cove (original) (raw)
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Impacts of Solar UVR on Aquatic Microorganisms*
Photochemistry and Photobiology, 1997
The impact of Solar UVR radiation (UVR)t on aquatic microorganisms is central to our understanding of how they respond to their environment. Penetration of UVR to depths ~ ~~ *Editor's note: This Invited Review departs from the standard Review format for Photochemisfry and Photobiology in order to provide readers with summaries on diverse aspects of the potential effect of increased solar UVR exposure on aquatic microorganisms.
Overview of the Effects of Increased Solar UV on Aquatic Microorganisms
Photochemistry and Photobiology, 1997
pp. 71-99. Archiv fur Hydrobiologie, Ergebnisse de Limnologie. Karentz, D. and L. H. Lutze (1990) Evaluation of biologically harmful ultraviolet radiation in Antarctica with a biological dosimeter designed for aquatic environments. Limnol. Oceanogr. Regan, J. D. and H. Yoshida (1995) DNA IVB dosimeters. J. Photochem. Phorohiol. B: B i d . 31, 57-61. Fleischmann. E. M. (1989) The measurement and penetration of ultraviolet radiation into tropical marine water. Limnol. Oceanogr. 34, 1623-1629. (1992) Ozone depletion: ultraviolet radiation and phytoplankton biology in natural waters. Scirnce 255, 252-259. Piazena, H. and D.-P. Hader (1994). Penetration of solar UV in coastal lagoons and of the southern Baltic sea and its effect on phytoplankton communities. Photohiol. Photochem. 60, 463-469. Cabrera, S. and G . Pizarro (1994) Changes in chlorophyll a concentration, copepod abundance and UV and PAR penetration in the water column during the ozone depletion in antarctic Lake Kitiesh. 1992. Arch. Hvdrohiol. Ergeh. Limnol. 43, 11-99.
Experimental test of the effect of ultraviolet-B radiation in a planktonic community
Limnology and Oceanography, 1999
Ultraviolet-B (UVB, 280-320 nm) radiation is a natural component of sunlight that harms organisms and disturbs natural communities in surface waters. A natural planktonic assemblage of organisms (Ͻ240 m) was studied in a mesocosm experiment for 7 d under varying conditions of UVB radiation: UVB excluded, natural radiation, and UVB enhanced at two different levels. The dynamics of several populations at different trophic levels comprising heterotrophic bacteria (Ͻ1 m), heterotrophic flagellates (2-10 m), small phytoplankton (Ͻ5 m), large phytoplankton (5-20 m), and ciliates (15-35 m) were monitored during the experiment. Enhanced UVB provoked a significant decrease in the number of ciliates (66%) and large phytoplankton (63%) relative to natural UVB conditions. The severe effects of UVB radiation on ciliates and large phytoplankton communities shown here would strongly limit upward transfer of mass and energy. The decline of predator abundance (ciliates) under UVB stress relative to natural conditions resulted in a positive feedback between enhanced UVB radiation and prey abundances, shown by increased abundances of bacteria (49%), heterotrophic flagellates (up to 300%), and small phytoplankton (41%). Similarly, with respect to carbon partitioning, the decrease in ciliate and diatom carbon biomass (64 and 56%, respectively) under enhanced UVB exposure was balanced by an increase in the carbon biomass of heterotrophic bacteria (48%), heterotrophic flagellates (126%), and autotrophic flagellates (162%). As a manifestation of enhanced UVB at the community level, the ecosystem develops toward a microbial food web in preference to an herbivorous food web. Thus, enhanced UVB radiation can change the structure and dynamics of the pelagic food web.
BENEFICIAL AND DETRIMENTAL EFFECTS OF UV ON AQUATIC ORGANISMS: IMPLICATIONS OF SPECTRAL VARIATION
Ecological Applications, 2001
Solar ultraviolet radiation (UVR) may have beneficial as well as detrimental effects on living systems. For example, UV-B radiation (280-320 nm) is generally damaging, while UV-A radiation (320-400 nm) may cause damage or stimulate beneficial photorepair of UV-B damage. The nature of both direct and indirect effects of UVR in nature depends on both the photon flux density and the spectral composition of the radiation incident on aquatic organisms across environmental UVR gradients in space (depth, transparency, elevation) and time (diel, seasonal, interannual). Here we use the common and widespread freshwater cladoceran Daphnia pulicaria as a model organism to demonstrate the potential importance of these wavelength-specific effects of UVR to the ecology of aquatic organisms. UVR-exposure experiments are used to manipulate both natural solar and artificial UVR sources to examine the beneficial as well as detrimental effects of different wavelengths of UVR. Changes in the spectral composition of solar radiation are also examined along several natural environmental gradients including diel gradients, depth gradients, and dissolved organic carbon (DOC) gradients. The implications of variation in the spectral composition of UVR for aquatic organisms are discussed.
Aquatic Microbial Ecology, 2001
Effects of ambient and enhanced UV-B radiation (UVBR) on marine microbial plankton communities were assessed in a model ecosystem at Kristineberg Marine Research Station (KMRS) on the Swedish west coast. The system consisted of 16 aquaria (40 l) filled with surface seawater and semicontinuously run by replacing 10 l of their contents with filtered seawater twice a day. The aquaria were placed outdoors and the ambient solar radiation was reduced by 70% using neutral screens. Four different levels of UVBR were applied, each in 4 replicates: nothing, ambient, ambient +10% and ambient + 20%. The enhanced UVBR was supplied by fluorescent tubes whose intensity was modulated by the ambient radiation to give a constant percentage increase. Variables measured were nutrients (N, P, Si), composition of phytoplankton species and pigments, bacterial and primary productivity, and bacterial cell numbers. Statistically significant UVBR effects were found for carbon allocation, size distribution of primary productivity and phytoplankton species composition. It was also found that UVBR exposure during the development of the phytoplankton communities increased their sensitivity to UVBR in short-term carbon dioxide fixation measurements. We propose that this was due to an adaptation of the community to UVBR, including an increased production of components within the photosynthetic apparatus damaged by UVBR. The UVBR had no significant effect on the total biomass of phytoplankton and bacteria.
Journal of Photochemistry and Photobiology B: Biology, 2007
Experiments (6-8 days) were carried out during the austral summer of 2005 in Chubut, Argentina (43°S, 65°W) to determine the interactive effects of solar UVR (280-400 nm) and nutrient addition on growth and chlorophyll fluorescence of four species of marine phytoplankton-the diatoms Thalassiosira fluviatilis Hustedt and Chaetoceros gracilis Schü tt, and the dinoflagellates Heterocapsa triquetra (Ehrenberg) Stein and Prorocentrum micans (Ehrenberg). Samples were incubated under three radiation treatments (two sets of each radiation treatment): (a) samples exposed to full solar radiation (PAR + UVR, PAB treatment, 280-700 nm); (b) samples exposed to PAR and UV-A (PA treatment, 320-700 nm) and (c) samples exposed only to PAR (P treatment, 400-700 nm). At the beginning of the experiments, nutrients (i.e., NaPO 4 H 2 and NaNO 3) were added to one set of samples from each radiation treatment (''N'' cultures) whereas in the other, the nutrients concentration was that of the culture medium. At all times, the lowest growth rates (l) were determined in the PAB treatments, where enriched cultures had significantly higher l (P < 0.05) than non-enriched cultures. Daily cycles of photochemical quantum yield (Y) displayed a pattern of relatively high values early in the morning with a sharp decrease at noon; recovery was observed late in the afternoon. In general, higher Y values were determined in enriched cultures than in non-enriched cultures. As the experiments progressed, acclimation (estimated as the difference between Y at noon and that at time zero) was observed in all species although in variable degree. All species displayed some degree of UVR-induced decrease in the photochemical quantum yield, although it was variable among treatments and species. However, this effect decreased with time, and this pattern was more evident in the dinoflagellates, as the concentration of UV-absorbing compounds increased. Thus, under conditions of nutrient enrichment as may occur by river input or by re-suspension by mixing, dinoflagellates outcompete with diatoms because they may have a higher fitness under UVR stress.
Role of ultraviolet-B radiation on bacterioplankton and the availability of dissolved organic matter
Plant Ecology, 1997
Attenuation of ultraviolet (UV)-radiation into the water column is highly correlated with the concentration of the dissolved organic matter (DOM). Thus UV penetrates deeper into marine waters than into freshwater systems. DOM is efficiently cleaved by solar surface radiation levels consuming more oxygen than bacterial metabolism. This photolytically cleaved DOM exhibits higher absorbance ratios (250/365 nm) than untreated DOM. Natural bacterioplankton reach higher abundance if inoculated in previously solar-exposed DOM than in untreated DOM; during bacterial growth the absorbance ratio declines steadily indicating the utilization of the photolytically cleaved DOM. On the other hand, bacterioplankton are greatly reduced in their activity if exposed to surface solar radiation levels. Photoenzymatic repair of DNA induced by UV-A radiation, however, leads to an efficient recovery of bacterial activity once the UV-B stress is released. Turbulent mixing of the upper layers of the water column leads to a continuous alteration of the UV exposure regime. Close to the surface, bacteria and DOM are exposed to high levels of UV-B leading to a reduction in bacterial activity and to photolysis of DOM. Once mixed into deeper layers where UV-B is attenuated, but sufficient UV-A is remaining to allow photoenzymatic repair, the photolytically cleaved DOM is efficiently taken up by bacterioplankton leading to even higher bacterial activity than prior to the exposure. Thus, the overall effect of UV on bacterioplankton is actually an enhancement of bacterial activity despite their lack of protective pigments.
Quantifying effects of ultraviolet radiation in surface waters
2000
Ten years ago, it was well known that ultraviolet radiation (UV) damages DNA, inhibits photosynthesis, and causes other biological effects. The ecological and biogeochemical significance of UV in aquatic systems was essentially unknown, because critical uncertainties prevented quantitative assessment. Consequently, the effects of stratospheric ozone depletion could not be predicted with confidence.
Limnology and Oceanography, 2002
Phytoplankton samples were collected at Bahía Engaño, Chubut, Argentina (43ЊS, 65ЊW) at different times of the year to assess the combined effect of ultraviolet radiation (UVR, 280-400 nm) and vertical mixing (i.e., the depth of the upper mixed layer, UML) on photosynthesis. Samples were exposed to fixed and fluctuating radiation regimes in an illuminated chamber at 15ЊC (photosynthetically available radiation [PAR] ϭ 66 W m Ϫ2 ; UV-A ϭ 15.3 W m Ϫ2 ; UV-B ϭ 0.7 W m Ϫ2 ), receiving either PAR ϩ UVR or PAR only. A comparison between fixed and rotating systems showed that when Z UML /Z Eu ϭ 0.6 (i.e., 60% of the euphotic zone [Eu] was mixed), only postbloom assemblages (codominated by nanoplanktonic flagellates and diatoms [Chaetoceros spp.]) were affected significantly by UVR. Integrated carbon fixation values during pre-and postbloom periods were higher under mixed conditions than under fixed irradiances. However, during the bloom (dominated by the microplanktonic diatom Odontella aurita), phytoplankton exposed to fluctuation radiation regimes had lower integrated carbon fixation. When postbloom samples were exposed to different mixing conditions, integrated UVR-induced inhibition reduced carbon fixation by 11-13% when Z UML /Z Eu ϭ 0.6, whereas when Z UML /Z Eu ϭ 0.91, carbon fixation increased by 7-12%. The differences in responses observed between prebloom, bloom, and postbloom samples can be attributed to a number of factors, such as the light history of cells, taxonomic composition, and size structure of the community and most probably reflect the different inhibition kinetics of these assemblages.