caa a22 4500 378931830 CHVBK 20180305123631.0 cr unu---uuuuu 161128e20040701xx s 000 0 eng 10.1515/BOT.2004.036 doi (NATIONALLICENCE)gruyter-10.1515/BOT.2004.036 Importance of within-shoot epiphyte distribution for the carbon budget of seagrasses: the example of Posidonia oceanica [Elektronische Daten] [Teresa Alcoverro, Marta Pérez, Javier Romero] To assess the effects of shading by epiphytes on the carbon balance of the seagrass Posidonia oceanica, we examined the patterns of within-shoot epiphyte abundance on leaves, and their variability with season and depth. Epiphyte biomass was found to depend on leaf age (larger epiphyte load on older tissues), leaf side (more epiphytes on the inner face than on the outer) and depth (more epiphytes in deep meadows). Depth differences were maximum in spring and disappeared in late summer. Percent light absorbed (absorptance) by epiphytes was measured; light absorptance followed an exponential- saturated model with epiphyte biomass. Combining these data of percent light absorbed, within-shoot epiphyte biomass distribution and an existing carbon balance model, we conclude that reduction in carbon gains caused by epiphyte shading is relatively small, and greater in deep meadows (8.8% on average, with values up to 14.2% in May) than that in shallow water (4.7% on average with maximum values of 7% in August). This is mainly due to the accumulation of epiphytes on old tissues, which contribute only marginally to the carbon gain of the plant. Using the same procedure, we modelled the effects of a doubling in epiphyte biomass, conserving the observed within-shoot distribution. The result was a very small additional carbon loss. However, using the same biomass but modifying the distribution (shifting the same abundance towards younger leaf age classes), the reduction in carbon gains was dramatic, particularly in deep meadows (between 21% and 41%, depending on the shift used). Therefore, it is the epiphyte growth timing rate rather than the final biomass reached which seems to be a key control for Posidonia oceanica survival, especially near the deep limit of its distribution. © Walter de Gruyter Hydrobiology nationallicence Mycology, fungi nationallicence Botany & plant sciences nationallicence carbon balance nationallicence irradiance nationallicence Mediterranean Sea nationallicence photosynthesis nationallicence seagrass nationallicence Alcoverro Teresa Centre d'Estudis Avanc¸ ats de Blanes, CSIC, C/ACC Cala St. Francesc, 14, 17300 Blanes, Girona, Spain aut Pérez Marta Departament d'Ecologia, Universitat de Barcelona, Avgda. Diagonal 645, 08028 Barcelona, Spain aut Romero Javier Departament d'Ecologia, Universitat de Barcelona, Avgda. Diagonal 645, 08028 Barcelona, Spain aut Botanica Marina Walter de Gruyter 47/4(2004-07-01), 307-312 0006-8055 47:4<307 2004 47 botm https://doi.org/10.1515/BOT.2004.036 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1515/BOT.2004.036 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Alcoverro Teresa Centre d'Estudis Avanc¸ ats de Blanes, CSIC, C/ACC Cala St. Francesc, 14, 17300 Blanes, Girona, Spain aut NATIONALLICENCE 700 1- Pérez Marta Departament d'Ecologia, Universitat de Barcelona, Avgda. Diagonal 645, 08028 Barcelona, Spain aut NATIONALLICENCE 700 1- Romero Javier Departament d'Ecologia, Universitat de Barcelona, Avgda. Diagonal 645, 08028 Barcelona, Spain aut NATIONALLICENCE 773 0- Botanica Marina Walter de Gruyter 47/4(2004-07-01), 307-312 0006-8055 47:4<307 2004 47 botm CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter