En el ano 2015, en el marco del Convenio 552 entre el Instituto Colombiano de Desarrollo Rural (Incoder) y el Instituto de Estudios Interculturales (IEI) de la Pontificia Universidad Javeriana Cali, se realizaron tres Espacios de Fortalecimiento Organizativo: Derechos y legislacion agraria para el desarrollo rural, dirigido a la Asociacion de Usuarios Campesinos (ANUC) y desarrollado en dos grupos: las macrorregiones Suroccidente y Norte; Derechos del campesinado, legislacion agraria, minera y ambiental, dirigido a la mesa campesina del Comite de Integracion del Macizo Colombiano (CIMA), y el Proceso de Unidad Popular del Suroccidente Colombiano (Pupsoc) en el departamento del Cauca.
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 147:285-294 (1997) - doi:10.3354/meps147285 Response of a mixed Philippine seagrass meadow to experimental burial Duarte CM, Terrados J, Agawin NSR, Fortes MD, Bach S, Kenworthy WJ The effect of burial due to sudden sediment loading was examined in a mixed Philippine seagrass meadow through the experimental deployment of sediment (0, 2, 4, 8, and 16 cm deposited over the experimental plots). The responses in shoot density, vertical growth, and branching of the species present were assessed 2, 4, and 10 mo following disturbance. Shoot density responses were strongly species-specific. The large Enhalusacoroides maintained shoot density at all burial treatments, and only showed evidence of decline by the end of the experiment. Thalassiahemprichii and, to a lesser extent, Cymodocearotundata showed a sharp decline in shoot density even at moderate burial treatments, from which they failed to recover. The accompanying species (Haloduleuninervis, Syringodiumisoetifolium, and Cymodoceaserrulata) showed an initial decline in shoot density followed by recovery. The small Halophilaovalis showed an opportunistic growth in plots receiving intermediate (buried by 4 and 8 cm sediment) disturbance, reaching shoot densities well in excess of those on control plots. The results suggest a pattern of species loss following disturbance by sediment burial corresponding to the sequence, T. hemprichii-> (C. rotundata, S. isoetifolium, H. uninervis) ->C.serrulata->E. acoroides. Vertical growth increased significantly for all species with differentiated vertical shoots, except C. serrulata. The examination of the time course of vertical growth imprinted on the shoots of the dominant species, T. hemprichii, revealed a rapid response to burial through increased internodal length, which was maintained over 8 mo following the disturbance. The resulting cumulative vertical growth along the experiment was linearly correlated with the degree of burial imposed on the plants. Branching of vertical shoots also increased significantly (73 to 96%, depending on the species) with burial. Experimental burial induced changes in shoot age distribution of some of the species, involving rearrangements, through selective mortality or recruitment, of the contribution of young shoots to the populations. The results obtained show major differences in species response to small-scale disturbance, closely linked to predictions derived from consideration of species growth rate and size, and provide evidence of the importance of small-scale disturbance in the maintenance of multispecific seagrass meadows. Seagrass · SE Asia · Disturbance · Sediment burial Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 147. Publication date: February 27, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.
Abstract. The emerging field of blue carbon science is seeking cost-effective ways to estimate the organic carbon content of soils that are bound by coastal vegetated ecosystems. Organic carbon (Corg) content in terrestrial soils and marine sediments has been correlated with mud content (i.e., silt and clay, particle sizes < 63 µm), however, empirical tests of this theory are lacking for coastal vegetated ecosystems. Here, we compiled data (n = 1345) on the relationship between Corg and mud contents in seagrass ecosystems (79 cores) and adjacent bare sediments (21 cores) to address whether mud can be used to predict soil Corg content. We also combined these data with the δ13C signatures of the soil Corg to understand the sources of Corg stores. The results showed that mud is positively correlated with soil Corg content only when the contribution of seagrass-derived Corg to the sedimentary Corg pool is relatively low, such as in small and fast-growing meadows of the genera Zostera, Halodule and Halophila, and in bare sediments adjacent to seagrass ecosystems. In large and long-living seagrass meadows of the genera Posidonia and Amphibolis there was a lack of, or poor relationship between mud and soil Corg content, related to a higher contribution of seagrass-derived Corg to the sedimentary Corg pool in these meadows. The relatively high soil Corg contents with relatively low mud contents (e.g., mud-Corg saturation) in bare sediments and Zostera, Halodule and Halophila meadows was related to significant allochthonous inputs of terrestrial organic matter, while higher contribution of seagrass detritus in Amphibolis and Posidonia meadows disrupted the correlation expected between soil Corg and mud contents. This study shows that mud is not a universal proxy for blue carbon content in seagrass ecosystems, and therefore should not be applied generally across all seagrass habitats. Mud content can only be used as a proxy to estimate soil Corg content for scaling up purposes when opportunistic and/or low biomass seagrass species (i.e., Zostera, Halodule and Halophila) are present (explaining 34 to 91 % of variability), and in bare sediments (explaining 78 % of the variability). The results obtained could enable robust scaling up exercises at a low cost as part of blue carbon stock assessments.
One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic primary production can proceed is poorly quantified. Here, we use a new analysis of satellite (SeaWiFS) data collected between 1998 and 2003 to estimate, for the first time at a nearly global scale, the irradiance reaching the bottom of the coastal ocean. The following cumulative functions provide the percentage of the surface (<i>S</i>) of the coastal zone receiving an irradiance greater than <i>E<sub>z</sub></i> (in mol photons m<sup>−2</sup> d<sup>−1</sup>): <br><br> <i>S</i><sub>Non-polar</sub> = 29.61 − 17.92 log<sub>10</sub>(<i>E<sub>z</sub></i>) + 0.72 log<sub>10</sub><sup>2</sup>(<i>E<sub>z</sub></i>) + 0.90 log<sub>10</sub><sup>3</sup>(<i>E<sub>z</sub></i>) <br><br> <i>S</i><sub>Arctic</sub> = 15.99 − 13.56 log<sub>10</sub>(<i>E<sub>z</sub></i>) + 1.49 log<sub>10</sub><sup>2</sup>(<i>E<sub>z</sub></i>) + 0.70 log<sub>10</sub><sup>3</sup>(<i>E<sub>z</sub></i>) <br><br> Data on the constraint of light availability on the major benthic primary producers and net community production are reviewed. Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m<sup>−2</sup> d<sup>−1</sup> depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m<sup>−2</sup> d<sup>−1</sup>. Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (<i>NCP</i>, the balance between gross primary production and community respiration) is positive. Positive benthic <i>NCP</i> can occur over 33% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, the lack of global information on the benthic nepheloid layer, and the relatively limited biological information available, are discussed.
Use of algal surfaces as substrate for bacterial growth requires colonization of the algal surface.Based on a study of the dynamics of epialgal bacteria during a bloom episode of an enclosed phytoplankton community, we suggest that the colonization process is partially limited by the algabacterium encounter probability.This assertion is based on the demonstration that 86 % of temporal variability in the average number of epialgal bacteria per algal cell can be explained by changes in the abundance of algae and free bacteria, that together constrain the alga-bacterium encounter probabhty.Encounter probability should, therefore, be of paramount importance for bacterial attachment to particles in the sparser communities inhabiting the oligotrophic sea.We postulate that one of the advantages of maintaining a dense, albeit not very active, bacterial population in the sea should be to maximize the probability of encountering algae or other patchy sources of organic carbon.
