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- Title
SEASONAL VARIATION OF PHOTOSYNTHETIC PERFORMANCE AND LIGHT ATTENUATION IN <em>ULVA</em> CANOPIES FROM PALMONES RIVER ESTUARY.
- Authors
Vergara, Juan J.; Pérez-Lloréns, J. Lucas; Peralta, Gloria; Hernández, Ignacio; Niell, F. Xavier
- Abstract
The primary production of Ulva populations relies on their photosynthetíc performance, which is dependent on the light availability under natural conditions. This study concerns the light attenuation characteristics in Ulva canopies and the seasonal photosynthetic performance of two different species (Ulva rotundata Blid., Ulva curvata (Kütz.) De Toni) blooming in the Palmones river estuary. Light within canopies differed form that reaching the surface. Light availability was reduced through the water column (at high tide) and Ulva canopies, In addition, light was spectrally filtered. As a result, the photosynthetically usable radiation (PUR) was further attenuated through Ulva canopies, increasing the photosynthetically active radiation/PUR ratio. The muddy sediment deposited on and between the Ulva thalli also drastically restricted the light availability. Thick Ulva mats are frequently found covering the intertidal mudflats, and therefore, thalli within these mats may be subjected to steep light gradients. As a consequence, individual Ulva growth rates cannot be extrapolated to estimate the primary production of Ulva canopies. Interspecific differences were observed for light-saturated photosynthetic rates (P[SUBmax]) and light compensation points (L[SUBcp]), with Ulva curvata generally displaying higher values than did U. rotundata. For both species, maxima were recorded in winter for P[SUBmax] quantum yield, chlorophyll content, and absorptance, whereas minima were found in summer. Dark respiration (R[SUBd]) was not seasonally affected, and a maximum L[SUBcp] was found in summer. To extrapolated these data to field situations, the temperature dependence of photosynthesis should be considered. The Q[SUB10] values were 2.44 for R[SUBd] and 1.79 for P[SUBmax] where as the photosynthesis rate at subsaturating light levels was unaffected. The Q[SUB10] values showed an enhanced respiratory rate in summer and a minimum in winter, whereas the seasonal differences on P[SUBmax] were damped.
- Subjects
PALMONES River (Spain); SPAIN; PHOTOSYNTHESIS; PLANT canopies; ULVA; RADIATION; LIGHT
- Publication
Journal of Phycology, 1997, Vol 33, Issue 5, p773
- ISSN
0022-3646
- Publication type
Article
- DOI
10.1111/j.0022-3646.1997.00773.x