Browsing by Issue Date, starting with "2022-11-03"
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- Passive acoustic localization of sperm whales to facilitate ship strike avoidancePublication . Klosner, Michael; Jesus, S. M.Ship strikes are one of the leading causes of premature mortality among whales, accounting for the deaths of approximately 20,000 each year, with untold more being injured. Given the exponential increase in shipping traffic, estimated at 2 - 3% year-over-year, the potential for collisions continues to grow. Due to their large size, preferred habitats and sea surface behavior, the sperm whale is one of the species most vulnerable to ship strikes. In some populations, collisions with maritime vessels are the leading cause of death, premature or otherwise. This is particularly concerning considering that the sperm whale is listed on the IUCN Red List of Threatened Species as “Vulnerable” globally and “Endangered” in the Mediterranean region. Passive Acoustic Monitoring, or PAM, is an environmentally non-intrusive method by which naturally generated underwater sounds, such as the clicks made by sperm whales, are picked up by hydrophones (underwater recording devices) and analyzed to extract a variety of data, including the sound source’s location. In the current research, we use a PAM methodology known as Time Difference of Arrival (TDOA) analysis, whereby different acoustic paths taken by sound waves from their source to a hydrophone are analyzed to extract the differences in time between their arrivals. Extracted TDOAs are compared to a theoretical model (in our case, the Bellhop ray tracing model) to extrapolate the source’s localization, which can then be fed into a live marine traffic system such as MarineTraffic (marinetraffic.com) to alert ships in the area to the presence and locations of the whales, so that they may take preventative action. In this dissertation, I present, inter alia, a working prototype, developed on the Matlab platform, for the detection and localization of sperm whales based on their vocalizations (clicks).
- Pathways and hot spots of floating and submerged microplastics in Atlantic Iberian marine waters: a modelling approachPublication . Rosas, Eloah; Martins, Flávio; Tosic, Marko; Janeiro, João; Mendonça, Fernando; Mills, LaraPlastic pollution has been observed in many marine environments surrounding the Iberian Peninsula, from the surface water to deeper waters, yet studies on their pathways and accumulation areas are still limited. In this study, a global ocean reanalysis model was combined with a particle-tracking Lagrangian model to provide insights into the pathways and accumulation patterns of microplastics originating in southern Portuguese coastal waters (SW Iberian). The study investigates microplastics floating on the surface as well as submerged at different water depths. Model results suggest that the North Atlantic Gyre is the main pathway for microplastics in surface and subsurface waters, transporting the microplastics southwards and eastwards towards the Mediterranean Sea and the Canary Islands. Currents flowing out of the Mediterranean Sea act as the main pathway for microplastics in deep waters, transporting the microplastics along western Iberia. An average residence time of twenty days in the coastal waters suggests that microplastics do not accumulate close to their sources due to their relatively fast transport to adjacent ocean areas. Notably, a significant proportion of microplastics leave the model domain at all depths, implying that SW Iberia may act as a source of microplastics for the adjacent areas, including the Mediterranean Sea, Morocco, the Canary Islands, Western Iberia, and the Bay of Biscay.
- Fish processing and digestion affect parvalbumins detectability in Gilthead Seabream and European seabassPublication . Schrama, Denise; Raposo de Magalhães, Cláudia; Cerqueira, Marco; Carrilho, Raquel; Revets, Dominique; Kuehn, Annette; Engrola, Sofia; Rodrigues, PedroConsumption of aquatic food, including fish, accounts for 17% of animal protein intake. However, fish consumption might also result in several side-effects such as sneezing, swelling and anaphylaxis in sensitized consumers. Fish allergy is an immune reaction to allergenic proteins in the fish muscle, for instance parvalbumin (PV), considered the major fish allergen. In this study, we characterize PV in two economically important fish species for southern European aquaculture, namely gilthead seabream and European seabass, to understand its stability during in vitro digestion and fish processing. This information is crucial for future studies on the allergenicity of processed fish products. PVs were extracted from fish muscles, identified by mass spectrometry (MS), and detected by sandwich enzyme-linked immunosorbent assay (ELISA) after simulated digestion and various food processing treatments. Secondary structures were determined by circular dichroism (CD) after purification by anion exchange and gel filtration chromatography. In both species, PVs presented as α-helical and β-sheet structures, at room temperature, were shown to unfold at boiling temperatures. In European seabass, PV detectability decreased during the simulated digestion and after 240 min (intestinal phase) no detection was observed, while steaming showed a decrease (p < 0.05) in PVs detectability in comparison to raw muscle samples, for both species. Additionally, freezing (−20 °C) for up to 12 months continued to reduce the detectability of PV in tested processing techniques. We concluded that PVs from both species are susceptible to digestion and processing techniques such as steaming and freezing. Our study obtained preliminary results for further research on the allergenic potential of PV after digestion and processing.