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- A high-precision liDAR-based method for surveying and classifying coastal notchesPublication . Terefenko, Pawel; Wziatek, Dagmara Zelaya; Dalyot, Sagi; Boski, T.; Lima-Filho, Francisco PinheiroFormation of notches is an important process in the erosion of seaside cliffs. Monitoring of coastal notch erosion rate and processes has become a prime research focus for many coastal geomorphologists. Observation of notch erosion rate considers a number of characteristics, including cliff collapse risk, distinction of historical sea levels, and recognition of ongoing erosional mechanisms. This study presents new approaches for surveying and classifying marine notches based on a high-precision light detection and ranging (LiDAR)-based experiment performed on a small region of a coastal cliff in southern Portugal. A terrestrial LiDAR scanner was used to measure geometrical parameters and surface roughness of selected notches, enabling their classification according to shape and origin. The implemented methodology proved to be a highly effective tool for providing an unbiased analysis of marine morphodynamic processes acting on the seaside cliffs. In the analyzed population of voids carved into Miocene calcarenites in a coastal cliff section, two types of notch morphology were distinguished, namely U-shaped and V-shaped. The method presented here provides valuable data for landscape evaluation, sea-level changes, and any other types of analyses that rely on the accurate interpretation of cliff morphological features.
- Holocene evolution of a barrier island system, Ria Formosa, South PortugalPublication . Sousa, Carlos; Boski, T.; Pereira, LauraHolocene evolution of the Ria Formosa barrier island system was studied through the examination of a large subsurface dataset acquired from 191 boreholes and five seismic refraction profiles. Two boreholes with total depths of 26 and 16.5 m were selected for a multi-proxy detailed laboratory analysis, including mean grain size distribution, organic matter (OM) content, color variation, shell identification, and benthic foraminifera assemblages. Selected cores are thought to be representative of the identified depositional sub-basins. Subsurface age data from 16 AMS C-14 dated samples were plotted against depth and resulted in a coherent age model of sedimentary infill. The system evolution was largely controlled by sediment availability, accommodation space, and Holocene sea level rise, first at a rapid rate of 7 mm/yr from 10 kcal yr BP to 7.25 kcal yr BP, followed by a slowdown to 1.1 mm/yr until present. A conceptual model for the origin and Holocene evolution of the Ria Formosa barrier island system implies three main steps, leading to the present system geomorphology: (1) marine flooding of incised palaeovalleys by the rapid transgression of palaeovalleys in the early Holocene
- Simonsenia aveniformis sp nov (Bacillariophyceae), molecular phylogeny and systematics of the genus, and a new type of canal raphe systemPublication . Witkowski, Andrzej; Gomes, Ana; Mann, David G.; Trobajo, Rosa; Li, Chunlian; Barka, Frederik; Gusev, Evgeniy; Dabek, Przemyslaw; Grzonka, Justyna; Kurzydlowski, Krzysztof J.; Zglobicka, Izabela; Harrison, Michael; Boski, T.The genus Simonsenia is reviewed and S. aveniformis described as new for science by light and electron microscopy. The new species originated from estuarine environments in southern Iberia (Atlantic coast) and was isolated into culture. In LM, Simonsenia resembles Nitzschia, with bridges (fibulae) beneath the raphe, which is marginal. It is only electron microscope (EM) examination that reveals the true structure of the raphe system, which consists of a raphe canal raised on a keel (wing), supported by rib like braces (fenestral bars) and tube-like portulae; between the portulae the keel is perforated by open windows (fenestrae). Based on the presence of portulae and a fenestrated keel, Simonsenia has been proposed to be intermediate between Bacillariaceae and Surirellaceae. However, an rbcL phylogeny revealed that Simonsenia belongs firmly in the Bacillariaceae, with which it shares a similar chloroplast arrangement, rather than in the Surirellaceae. Lack of homology between the surirelloid and simonsenioid keels is reflected in subtle differences in the morphology and ontogeny of the portulae and fenestrae. The diversity of Simonsenia has probably been underestimated, particularly in the marine environment.
- Coastal paleokarst landforms: a morphometric approach via UAV for coastal management (Algarve, Portugal case study)Publication . Oliveira, Sónia; Moura, Delminda; Boski, T.; Horta, JoãoKarst landscapes display remarkable morphological diversity and raise challenging management questions. Understanding karst processes is particularly relevant to the management of densely populated rocky coastlines, since sea-level rise influences the erosion rate of potentially hazardous landforms (e.g. sinkholes). Appropriate management strategies are needed to mitigate against property loss and economic impacts on actively eroding karst. Coastal management in these areas should be based on accurate and reproducible measurements of karst features to better understand and predict their behaviour. Due to their inherent instability and frequent inaccessibility, detailed morphometric studies of exposed coastal sinkholes are limited. We demonstrate the utility of using an unmanned aerial vehicle (UAV) to provide rapid and accurate analysis of spatial data on a large density of sinkholes that would otherwise be inaccessible. UAV data were post-processed and analysed using geographical information (GIS) tools to characterize both individual sinkholes and their spatial distribution patterns. Our study was carried out on the rocky coast of the central Algarve (southern Portugal). As stated in many other previous works, sinkholes spatial distribution is mainly controlled by the network of fractures in the host rock that was also observed in our study area. In addition, the geometric properties and their differences between the studied sites are controlled by weathering processes and synoptic conditions. This research emphasises the geomorphic hazard associated with karst landscapes and reinforces the need to include knowledge about these landforms and their vulnerability to sea-level rise in integrated coastal management plans.