Changes in diatom patch-size distribution and degradation in a spatially self-organized intertidal mudflat ecosystem.

Self-organized spatial patterns have been proposed as possible indicators for regime shifts in ecosystems. Until now, this hypothesis has only been tested in drylands. Here, we focus on intertidal mudflats where regular spatial patterns develop in early spring from the interaction between diatom growth and sedimentation but disappear when benthic herbivore abundance increases in early summer, accompanied by a dramatic shift to a bare mudflat. We followed the patch-size distributions of diatom biofilms during this degradation process. As time progressed, we found a temporal change in the spatial configuration occurring simultaneously with the loss of the diatom-sediment feedback. This indicates a gradual failure in time of the self-organization process that underlies regular patterning in this ecosystem. The path to degradation co-occurred with the loss of the larger patches in the ecosystem, which resulted in a decrease of the truncation in the patch-size distribution. Hence, our study in mudflat ecosystems confirms the general hypothesis that spatial patterns can provide important clues about the level of degradation. Nevertheless, our study highlights the need for thorough study about the type of spatial patterns and the nature of the underlying feedbacks before a reliable assessment of ecosystem status can be made, as changes in patch-size distribution differed markedly with those observed in other ecosystems.

[Assessment of nonpenetrating deep sclerectomy with reticulated hyaluronic acid implant SKGEL and/or preoperative application of 5-luorouracil: results of 2 and a half years]. / Intérêt de la sclérectomie profonde couplée à la mise en place d'un implant SKGEL et/ou à une application peroperatoire de 5-fluorouracile: resultats à 2 ans et demi.

PURPOSE: To assess the effectiveness and the safety of deep sclerectomy (DS) with reticulated hyaluronic acid implant (SKGEL) and/or 5-Fluorouracile (5-FU). MATERIAL-METHODS: 42 phakic eyes (42 patients) (mean age: 61.0 +/- 11.5 years) with medically uncontrolled open angle glaucoma and without history of previous filtering procedure were included in this non-randomized retrospective study. According to the peroperative protocol, the patients were categorized into 3 groups: DS + SKGEL (7 eyes), DS + 5-FU (50/mg/ml during 3 minutes) (13 eyes) and group C with SKGEL and 5-FU simultaneously (22 eyes). RESULTS: The mean follow up was 30.6 +/- 9.2 months and was significantly shorter in group C. The 3 groups were comparable with respect to the age of the patients, the severity of glaucomatous defects, the distribution of the target IOP, the mean number and duration of preoperative medications as well as to the mean preoperative visual acuity and IOP. The mean IOP was significantly decreased from 27.3 +/- 3.2 mm Hg to 16.1 +/- 3.7 3.7 mm Hg (p < 0.0001) and was not significantly different between the 3 groups at 24 months follow up (p > 0.05). Mean visual acuity was not significantly altered in the 3 groups (p > 0.05). Complete (target IOP reached without medication or YAG laser goniopuncture) and qualified (target IOP reached with medication and/or YAG laser goniopuncture) final success rates were respectively 33.3% and 83.3%. The frequency of distribution of success was not significantly different between the 3 groups but the percentage of success was 100% in group A, 84.6% in group B and 77.2% in group C. Subconjunctival injections were needed in 33% in the first postoperative month. (group A: 28.5%; group B: 46.2%; group C: 27.2%) (X2 p > 0.05). Postoperative complications were relatively minor and were observed in 66% (P > 0.05 between the 3 groups). YAG laser goniopunctures were performed in 38% (group A: 16.6%; group B: 61.5%; group: 33.3%, X2 p > 0.05). Complete and qualified success probability were better in SKGEL group comparatively with the other 2 groups. CONCLUSIONS: Considering its limitations and with a follow-up of 2 years and half, this study could confirm the safety and the efficacy of DS in return for which topical medication(s) and/or YAG laser gonioperforations were needed in a relatively high percentage of the cases. The benefits of the SKGEL implant on the quality of the IOP control appeared to be higher than 5-FU.