The dilemma of underestimating freshwater biodiversity: morphological and molecular approaches.

BACKGROUND: Anthropogenic impacts on freshwater habitats are causing a recent biodiversity decline far greater than that documented for most terrestrial ecosystems. However, knowledge and description of freshwater biodiversity is still limited, especially targeting all size classes to uncover the distribution of biodiversity between different trophic levels. We assessed the biodiversity of the Lower Rhine and associated water bodies in the river's flood plain including the river's main channel, oxbows and gravel-pit lakes, spanning from the level of protists up to the level of larger invertebrate predators and herbivores organized in size classes (nano-, micro, meio- and macrofauna). Morphological diversity was determined by morphotypes, while the molecular diversity (amplicon sequencing variants, ASVs) was assessed through eDNA samples with metabarcoding targeting the V9 region of the 18S rDNA. RESULTS: Considering all four investigated size classes, the percentage of shared taxa between both approaches eDNA (ASVs with 80-100% sequence similarity to reference sequences) and morphology (morphotypes), was always below 15% (5.4 ± 3.9%). Even with a more stringent filtering of ASVs (98-100% similarity), the overlap of taxa could only reach up to 43% (18.3 ± 12%). We observed low taxonomic resolution of reference sequences from freshwater organisms in public databases for all size classes, especially for nano-, micro-, and meiofauna, furthermore lacking metainformation if species occur in freshwater, marine or terrestrial ecosystems. CONCLUSIONS: In our study, we provide a combination of morphotype detection and metabarcoding that particularly reveals the diversity in the smaller size classes and furthermore highlights the lack of genetic resources in reference databases for this diversity. Especially for protists (nano- and microfauna), a combination of molecular and morphological approaches is needed to gain the highest possible community resolution. The assessment of freshwater biodiversity needs to account for its sub-structuring in different ecological size classes and across compartments in order to reveal the ecological dimension of diversity and its distribution.

Reconstruction of orbital floor fracture with polyglactin 910/polydioxanon patch (ethisorb): a retrospective study.

PURPOSE: We sought to evaluate the effectiveness and the complications related to the use of Ethisorb (resorbable alloplastic material) in the reconstruction of orbital floor fractures. PATIENTS AND METHODS: We retrospectively reviewed the charts of all patients who underwent orbital floor fracture reconstruction with Ethisorb since 2001. We only included patients with a minimum follow-up of 3 months. The following data were recorded for every patient: age, gender, cause of trauma, time from trauma to surgery, signs and symptoms, concomitant ocular injuries, radiographic analysis, pertinent intraoperative findings (including the type of approach), follow-up time, and postoperative complications. RESULTS: Eighty-seven patients were included in the study. Twenty-one patients (24.1%) experienced postoperative complications. Of these, only 3 patients (3.4%) had permanent complications directly related to the Ethisorb membrane (diplopia, enophthalmos). Two of these patients required revision surgery and are discussed in the article. CONCLUSIONS: The results of our study demonstrate the effectiveness of Ethisorb in the repair of small-to-moderate orbital floor fracture defects (up to a maximum size of 2 x 2 cm).