TY - JOUR
T1 - Community photosynthesis of aquatic macrophytes
AU - Binzer, T.
AU - Sand-Jensen, K.
AU - Middelboe, A. L.
PY - 2006
Y1 - 2006
N2 - We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities ofmacroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relationin all communities and no sign of photosaturation or photoinhibition of photosynthesis at the highest irradiancesof about 2,000 mmol m22 s21. Macrophyte communities displayed much higher maximum gross production(GPmax), respiration, and light compensation point than separate phytoelements because of the multilayeredstructure and extensive self-shading in the communities, whereas light use efficiency at low irradiance (a) was thesame. Although GPmax and a varied extensively among the 190 communities, their upper limits increased linearlyand predictably with community absorption reaching 26.3 mmol m22 s21 O2 and 0.090 mol mol21 photon at100% absorption. The upper limit of a is close to a realistic limit of O2 of 0.10 mol mol21 photon. The upper limitof GPmax, however, is markedly below the theoretically attainable 180 mol m22 s21 O2, reflecting a suboptimalthree-dimensional structure and light distribution. Indirect measures supported this explanation as GPmaxincreased fourfold from communities with a very uneven to a more even light distribution. Photosyntheticcharacteristics of communities are strongly influenced by plant density, absorption, and distribution of light andcannot be interpreted from the photosynthetic behavior of phytoelements. Thus, many examples of carbon andnutrient limitation in experiments with separate phytoelements may not withstand at the relevant ecological scaleof communities where light almost always constrains photosynthetic production.
AB - We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities ofmacroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relationin all communities and no sign of photosaturation or photoinhibition of photosynthesis at the highest irradiancesof about 2,000 mmol m22 s21. Macrophyte communities displayed much higher maximum gross production(GPmax), respiration, and light compensation point than separate phytoelements because of the multilayeredstructure and extensive self-shading in the communities, whereas light use efficiency at low irradiance (a) was thesame. Although GPmax and a varied extensively among the 190 communities, their upper limits increased linearlyand predictably with community absorption reaching 26.3 mmol m22 s21 O2 and 0.090 mol mol21 photon at100% absorption. The upper limit of a is close to a realistic limit of O2 of 0.10 mol mol21 photon. The upper limitof GPmax, however, is markedly below the theoretically attainable 180 mol m22 s21 O2, reflecting a suboptimalthree-dimensional structure and light distribution. Indirect measures supported this explanation as GPmaxincreased fourfold from communities with a very uneven to a more even light distribution. Photosyntheticcharacteristics of communities are strongly influenced by plant density, absorption, and distribution of light andcannot be interpreted from the photosynthetic behavior of phytoelements. Thus, many examples of carbon andnutrient limitation in experiments with separate phytoelements may not withstand at the relevant ecological scaleof communities where light almost always constrains photosynthetic production.
M3 - Journal article
SN - 0024-3590
VL - 51
SP - 2722
EP - 2733
JO - Limnology and Oceanography
JF - Limnology and Oceanography
IS - 6
ER -
