Evaluation of the different levels of variability in the underwater light field of a shallow estuary

被引:95
作者
Schubert, H
Sagert, S
Forster, RM
机构
[1] Ernst Moritz Arndt Univ Greifswald, Inst Okol, AG Pflanzenokol, D-17487 Greifswald, Germany
[2] NIOO, CEMO, NL-4400 AC Yerseke, Netherlands
关键词
ultraviolet radiation; light climate; dissolved organic matter; wave focussing;
D O I
10.1007/s101520000064
中图分类号
Q17 [水生生物学];
学科分类号
071004 ;
摘要
The underwater light climate of a shallow estuary located at the southern coast of the Baltic Sea has been investigated, with special emphasis on the spectral irradiance composition and on short-term irradiance fluctuations caused by vertical mixing and wave focussing. The inherent optical properties of the water body were dominated by phytoplankton pigment absorption in the long-wavelength range and by coloured, dissolved organic matter (cDOM) absorption in the wavelength range <500 nm, including ultraviolet-A (UV-A) and ultraviolet-B radiation (UV-B). Pronounced particulate scattering combined with the absorption values to give very high attenuation coefficients, especially for the shorter wavelengths of UV-B radiation. Photosynthetically active radiation (PAR) was found to be reduced to 1% of the surface value within 0.8 m in the inner, hypertrophic end of the estuary and within 1.9 m in the outer, eutrophic parts of this system, with corresponding 1% penetration depths for UV-B of 0.13 and 0.31 m. During late winter and early spring, the period when reduced atmospheric ozone concentrations and enhanced UV-B have been reported over northern Europe, the irradiance levels in the water column were greatly reduced, due to strong attenuation by ice cover and overlying snow, cDOM concentration of the water was also found to remain at a high level during these periods, and indeed throughout the year, thus reducing the exposure of organisms to UV-R and PAR still further. A complex irradiance regime was found in this system, with irregular and high amplitude fluctuations caused by wind-induced vertical mixing and wave focussing being superimposed upon the solar-angle-dependent seasonal and daily cycles. The methods used to quantify the short-term fluctuations are described, and their relevance to phytoplankton physiology is discussed. The wave-focussing effect is unique to the aquatic environment, and measurements showed that average subsurface irradiances could be increased by up to 5 times for periods lasting for <1 s. The highest irradiances recorded during wave-focussing events reached over 9,000 mu mol photons m(-2) s(-1).
引用
收藏
页码:12 / 22
页数:11
相关论文
共 47 条
[1]  
ALLEN JF, 1998, BIOCHIM BIOPHYS ACTA, P55
[2]  
AUSTIN RW, 1974, OPTICAL ASPECTS OCEA, P316
[3]   TOO MUCH OF A GOOD THING - LIGHT CAN BE BAD FOR PHOTOSYNTHESIS [J].
BARBER, J ;
ANDERSSON, B .
TRENDS IN BIOCHEMICAL SCIENCES, 1992, 17 (02) :61-66
[4]  
BJORN LO, 1985, PHYSIOL VEG, V23, P555
[5]   FURTHER OZONE DECLINE DURING THE NORTHERN-HEMISPHERE WINTER-SPRING OF 1994-1995 AND THE NEW RECORD LOW OZONE OVER SIBERIA [J].
BOJKOV, RD ;
FIOLETOV, VE ;
BALIS, DS ;
ZEREFOS, CS ;
KADYGROVA, TV ;
SHALAMJANSKY, AM .
GEOPHYSICAL RESEARCH LETTERS, 1995, 22 (20) :2729-2732
[6]  
BORNITZ R, 1995, ENTWICKLUNG ERPRONUN
[7]  
DEKKER AG, 1993, THESIS VRIJ U AMSTER
[8]   BIOLOGICAL PHYSICAL INTERACTIONS IN THE UPPER OCEAN - THE ROLE OF VERTICAL AND SMALL-SCALE TRANSPORT PROCESSES [J].
DENMAN, KL ;
GARGETT, AE .
ANNUAL REVIEW OF FLUID MECHANICS, 1995, 27 :225-255
[9]   TIME AND SPACE SCALES OF VERTICAL MIXING AND ADVECTION OF PHYTOPLANKTON IN THE UPPER OCEAN [J].
DENMAN, KL ;
GARGETT, AE .
LIMNOLOGY AND OCEANOGRAPHY, 1983, 28 (05) :801-815
[10]   INFLUENCE OF SPRING-NEAP TIDAL CYCLES ON THE LIGHT AVAILABLE FOR PHOTOSYNTHESIS BY BENTHIC MARINE PLANTS [J].
DRING, MJ ;
LUNING, K .
MARINE ECOLOGY PROGRESS SERIES, 1994, 104 (1-2) :131-137