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  • 1
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    Online Resource
    Pathological Findings in White-Beaked Dolphins (Lagenorhynchus albirostris) and Atlantic White-Sided Dolphins (Lagenorhynchus acutus) From the South-Eastern North Sea
    Frontiers Media SA ; 2020
    In:  Frontiers in Veterinary Science Vol. 7 ( 2020-5-27)
    Details
    In: Frontiers in Veterinary Science, Frontiers Media SA, Vol. 7 ( 2020-5-27)
    Type of Medium: Online Resource
    ISSN: 2297-1769
    URL: Article
    DOI: 10.3389/fvets.2020.00262
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2834243-4
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  • 2
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    Ultrastructure of the organ of Corti in harbor seals (Phoca vitulina)
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-9-4)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-9-4)
    Abstract: Ultrastructural descriptions of the inner ear of highly sound-dependent mammalian species are lacking and needed to gain a better understanding of the hearing sense. Here, we present the first morphometric descriptions of the sensory cells of the inner ear in the harbor seal ( Phoca vitulina ), a mammal with broadly sensitive amphibious hearing. Scanning electron micrographs of the apical surface of the outer hair cells (OHCs) and inner hair cells (IHCs) within the organ of Corti were obtained from five individuals and analyzed by linear and geometric morphometrics. Measurements were taken at regular locations along the cochlea. The spiral shape of the seal cochlea contained two and a half turns. The organ of Corti had an average length of 27.7 mm with 12,628 OHCs (12,400-12,900). Six linear morphometric parameters showed significant patterns of change associated with their location within the cochlear spiral. Likewise, these trends were similarly expressed in cell configuration (cell blocks with 57 landmarks in 12 representative cells) revealed by geometric morphometry. Cell configuration varied predictably with position in the cochlea according to clustering analyses and Procrustes ANOVA (F= 25.936, p & lt;0001). Changes associated with OHCs were primarily responsible for observed changes in cell configuration. An integration trend in cell shape change was also observed in which IHCs and OHCs share features in their morphological variation by the two-block partial least squares analysis (CR=0.987, p & lt;0.001) and the modularity hypothesis (CV=0.99, p=0.05). These descriptive and quantitative findings provide a baseline for the morphology and morphometry of the sensory cells of the organ of Corti in harbor seals, allowing for comparisons between normal and pathological features. This initial morphological description should enable the correlation between position, morphometric features, and frequency coding along the spiral of the inner ear in this species, whose hearing ability is well studied.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2023.1211556
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2757748-X
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  • 3
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    Table_2.docx
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-8-10)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-8-10)
    Abstract: The only native cetacean in German waters, the harbor porpoise ( Phocoena phocoena ), is impacted by numerous pathological lesions in the respiratory tract mainly caused by parasites or bacteria. Although harbor porpoises have been observed to not use their complete lung volume, it has not been studied whether this insufficiency leads to lower oxygen uptake, impaired diving ability, and, ultimately, reduced foraging success. This project aims to analyze whether harbor porpoises developed novel molecular adaptations to compensate impairments in oxygen supply, thus remaining viable and competitive despite the high parasitic load. Here, initial comparative transcriptome RNA sequencing (NextSeq 2000, Illumina) was performed on muscles of harbor porpoises with a respiratory tract considered as healthy and of harbor porpoises that suffered from more severe lesions and parasitic infestations in the respiratory tract. Our findings suggest an elevated response to oxidative stress in the muscles of parasitic infested harbor porpoises compared with that of healthy animals. Higher antioxidant and antiapoptotic gene expression in the muscles of non-healthy harbor porpoises might function as a compensatory effect to enhanced reactive oxygen species production and accumulation in the muscles. Simultaneously enhanced selective proteasomal degradation and myogenesis suggest a tightly controlled, finely tuned switch of the intrinsic muscle response to stress. Lipid metabolism pathways and rate-limiting transcripts involved in glycolysis were upregulated and may uphold muscle energy supply for tissue function and energy-consuming regenerative and biosynthetic processes. These preliminary results hint at a defined response of the muscle to oxidative stress that may be caused by lung tissue with more severe pathological lesions and may indicate a possible adaptation in cetaceans.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2023.1232305
    DOI: 10.3389/fmars.2023.1232305.s001
    DOI: 10.3389/fmars.2023.1232305.s002
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2757748-X
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  • 4
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    A Result of Accidental Noise Pollution: Acoustic Flowmeters Emit 28 kHz Pulses That May Affect Harbor Porpoise Hearing
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-7-7)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-7-7)
    Abstract: Large rivers like the Elbe or the Weser are periodically entered by harbor porpoises of the North Sea. They may even move 97 km upstream to the port of Hamburg, where their presence is highest in spring. This migration is believed to be related to important anadromous prey species travelling upstream for spawning. An acoustic flowmeter in the port of Hamburg emits signals in the hearing range of harbor porpoises. The pulses have a duration of 0.2 ms, a peak frequency of 28 kHz, a source level of 210 dB re 1 µPa and an inter-pulse interval of 4.2 s. The signals are continuously emitted from both sides of the river at a location where the river is 400 m wide. We evaluated the potential of these signals to induce temporary threshold shift (TTS) in harbor porpoise hearing. Hearing tests with a harbor porpoise in human care were conducted to determine TTS onset. We modelled the acoustic field based on underwater noise measurements. The acoustic flowmeters emit pulses in a highly directional beam with a source level high enough for inducing TTS in harbor porpoises by a single exposure up to a distance of approximately 72 m. The received cumulative sound exposure levels for harbor porpoises travelling along the flowmeters are mainly dependent on the timing and distance to the sound source. Accordingly, a close approach to the flowmeter at the time of transmission should be prevented. This could be the case, if vessels force harbor porpoises to displace closer to the flowmeters. We therefore suggest to decrease acoustic flowmeter source levels. This case study emphasizes the need for a mandatory authorization process prior to the use of underwater sound for any purpose with potential effects on aquatic life. Such an authorization process should carefully consider potential effects for target and non-target species.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2022.892050
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
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  • 5
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    Image_1.JPEG
    Frontiers Media SA ; 2021
    In:  Frontiers in Ecology and Evolution Vol. 9 ( 2021-4-13)
    Details
    In: Frontiers in Ecology and Evolution, Frontiers Media SA, Vol. 9 ( 2021-4-13)
    Abstract: Marine mammals are increasingly threatened in their habitat by various anthropogenic impacts. This is particularly evident in prey abundance. Understanding the dietary strategies of marine mammal populations can help predict implications for their future health status and is essential for their conservation. In this study we provide a striking example of a new dietary proxy in pinnipeds to document marine mammal diets using a dental record. In this novel approach, we used a combination of 49 parameters to establish a dental microwear texture (DMTA) as a dietary proxy of feeding behaviour in harbour seals. This method is an established approach to assess diets in terrestrial mammals, but has not yet been applied to pinnipeds. Our aim was to establish a protocol, opening DMTA to pinnipeds by investigating inter- and intra-individual variations. We analysed the 244 upper teeth of 78 Atlantic harbour seals ( Phoca vitulina vitulina ). The specimens were collected in 1988 along the North Sea coast (Wadden Sea, Germany) and are curated by the Zoological Institute of Kiel University, Germany. An increasing surface texture roughness from frontal to distal teeth was found and related to different prey processing biomechanics. Ten and five year old individuals were similar in their texture roughness, whereas males and females were similar to each other with the exception of their frontal dentition. Fall and summer specimens also featured no difference in texture roughness. We established the second to fourth postcanine teeth as reference tooth positions, as those were unaffected by age, sex, season, or intra-individual variation. In summary, applying indirect dietary proxies, such as DMTA, will allow reconstructing dietary traits of pinnipeds using existing skeletal collection material. Combining DMTA with time series analyses is a very promising approach to track health status in pinniped populations over the last decades. This approach opens new research avenues and could help detect dietary shifts in marine environments in the past and the future.
    Type of Medium: Online Resource
    ISSN: 2296-701X
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/fevo.2021.644019
    DOI: 10.3389/fevo.2021.644019.s001
    DOI: 10.3389/fevo.2021.644019.s002
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2745634-1
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  • 6
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    Variation of blubber thickness for three marine mammal species in the southern Baltic Sea
    Frontiers Media SA ; 2022
    In:  Frontiers in Physiology Vol. 13 ( 2022-11-23)
    Details
    In: Frontiers in Physiology, Frontiers Media SA, Vol. 13 ( 2022-11-23)
    Abstract: Evaluating populational trends of health condition has become an important topic for marine mammal populations under the Marine Strategy Framework Directive (MSFD). In the Baltic Sea, under the recommendation of Helsinki Commission (HELCOM), efforts have been undertaken to use blubber thickness as an indicator of energy reserves in marine mammals. Current values lack geographical representation from the entire Baltic Sea area and a large dataset is only available for grey seals ( Halichoerus grypus ) from Sweden and Finland. Knowledge on variation of blubber thickness related to geography throughout the Baltic Sea is important for its usage as an indicator. Such evaluation can provide important information about the energy reserves, and hence, food availability. It is expected that methodological standardization under HELCOM should include relevant datasets with good geographical coverage that can also account for natural variability in the resident marine mammal populations. In this study, seasonal and temporal trends of blubber thickness were evaluated for three marine mammal species—harbor seal ( Phoca vitulina ), grey seal ( Halichoerus grypus ) and harbor porpoise ( Phocoena phocoena )—resident in the southern Baltic Sea collected and investigated under stranding networks. Additionally, the effects of age, season and sex were analyzed. Seasonal variation of blubber thickness was evident for all species, with harbor seals presenting more pronounced effects in adults and grey seals and harbor porpoises presenting more pronounced effects in juveniles. For harbor seals and porpoises, fluctuations were present over the years included in the analysis. In the seal species, blubber thickness values were generally higher in males. In harbor seals and porpoises, blubber thickness values differed between the age classes: while adult harbor seals displayed thicker blubber layers than juveniles, the opposite was observed for harbor porpoises. Furthermore, while an important initial screening tool, blubber thickness assessment cannot be considered a valid methodology for overall health assessment in marine mammals and should be complemented with data on specific health parameters developed for each species.
    Type of Medium: Online Resource
    ISSN: 1664-042X
    URL: Article
    DOI: 10.3389/fphys.2022.880465
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2564217-0
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  • 7
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    Fatal aspergillosis and evidence of unrelated hearing loss in a harbor porpoise (Phocoena phocoena) from the German Baltic Sea
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-12-21)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-12-21)
    Abstract: Detailed post-mortem investigations including the auditory pathway are needed to advance our understanding of how underwater noise and other stressors affect hearing in cetaceans. A 12-year-old female porpoise ( Phocoena phocoena ) stranded alive in June 2021 at the German Baltic Sea coast and died some hours later. The most significant pathological findings were lesions caused by a severe aspergillosis that spread from the lung and pulmonary lymph node to the cerebellum. Based on molecular sequencing, the fungus was identified as Aspergillus fumigatus. Severe pyogranulomatous and necrotizing inflammation was diagnosed in the lung and the associated lymph node. In the left part of the cerebellum, focal, severe purulent and necrotizing meningoencephalitis with intralesional fungal structures was confirmed histologically. In addition, multifocal, severe, chronic, granulomatous, and eosinophilic gastritis with intralesional parasite structures was found in the stomach. Parallel stripes (linear skin markings) were detected along the caudal part of both body sides, which have not been previously described for harbor porpoises. Inner ear analysis revealed evidence of focal loss of outer hair cells in several regions from 120 to 580 µm from the apex of the right cochlea using immunofluorescence. The evidence of low-frequency hearing impairment was compatible with noise-induced hearing loss. This is the first case of concurrent presumptive noise-induced hearing loss and unrelated aspergillosis in a free-ranging harbor porpoise.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2022.958019
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
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  • 8
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    Data_Sheet_5.docx
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 7 ( 2021-1-7)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 7 ( 2021-1-7)
    Abstract: The North Sea is one of the most heavily used shelf regions worldwide with a diversity of human impacts, including shipping, pollution, fisheries, and offshore constructions. These stressors on the environment can have consequences for marine organisms, such as our study species, the harbor porpoise ( Phocoena phocoena ), which is regarded as a sentinel species and hence has a high conservation priority in the European Union (EU). As EU member states are obliged to monitor the population status, the present study aims to estimate trends in absolute harbor porpoise abundance in the German North Sea based on almost two decades of aerial surveys (2002–2019) using line-transect methodology. Furthermore, we were interested in trends in three Natura2000 Special Areas of Conservation (SACs), which include the harbor porpoise as designated feature. Trends were estimated for each SAC and two seasons (spring and summer) as well as the complete area of the German North Sea. For the trend analysis we applied a Bayesian framework to a series of replicated visual surveys, allowing to propagate the error structure of the original abundance estimates to the final trend estimate and designed to deal with spatio-temporal heterogeneity and other sources of uncertainty. In general, harbor porpoise abundance decreased in northern areas and increased in the south, such as in the SAC Borkum Reef Ground. A particularly strong decline with a high probability (94.9%) was detected in the core area and main reproduction site in summer, the SAC Sylt Outer Reef (−3.79% per year). The overall trend for the German North Sea revealed a decrease in harbor porpoise abundance over the whole study period (−1.79% per year) with high probability (95.1%). The assessment of these trends in abundance based on systematic monitoring should now form the basis for adaptive management, especially in the SAC Sylt Outer Reef, where the underlying causes and drivers for the large decline remain unknown and deserve further investigation, also in a regional North Sea wide context.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2020.606609
    DOI: 10.3389/fmars.2020.606609.s001
    DOI: 10.3389/fmars.2020.606609.s002
    DOI: 10.3389/fmars.2020.606609.s003
    DOI: 10.3389/fmars.2020.606609.s004
    DOI: 10.3389/fmars.2020.606609.s005
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
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  • 9
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    Data_Sheet_1.pdf
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-5-10)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-5-10)
    Abstract: Microplastic ingestion by lower trophic level organisms is well known, whereas information on microplastic ingestion, egestion and accumulation by top predators such as cetaceans is still lacking. This study investigates microplastics in intestinal samples from harbour porpoises ( Phocoena phocoena ) found along the coastline of Schleswig-Holstein (Germany) between 2014 and 2018. Out of 30 individuals found along the North Sea (NS) and the Baltic Sea (BS) coast, 28 specimens contained microplastic. This study found a relationship between the nutritional status of cetaceans and the amount of found microplastics. Harbour porpoises with a good or moderate nutritional status contained a higher number of microplastics, when compared with specimens in a poor nutritional status. In addition, when individuals died accidently due to suspected bycatch in gillnets, where a feeding event is highly assumed or a pharyngeal entrapment happened, the microplastic burden was higher. In total, 401 microplastics (≥100 μm), including 202 fibres and 199 fragments were found. Intestines of the specimens of the BS contained more microplastics than the ones from the NS. Differences in the share of fibres could be revealed: for BS fibres constituted 51.44% and for NS, fibres constituted 47.97%. The polymers polyester, polyethylene, polypropylene, polyamide, acrylic (with nitrile component) and an acrylic/alkyd paint chip (with styrene and kaolin components) were identified. This is the first study investigating the occurrence of microplastics in harbour porpoises from German waters and will, thus, provide valuable information on the actual burden of microplastics in cetaceans from the North and Baltic Seas.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2021.682532
    DOI: 10.3389/fmars.2021.682532.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
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  • 10
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    DataSheet_1.docx
    Frontiers Media SA ; 2024
    In:  Frontiers in Marine Science Vol. 11 ( 2024-3-7)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 11 ( 2024-3-7)
    Abstract: The management and conservation of biodiversity relies on information on both the abundance of species and the potential impact of threats. Globally, one of the largest threats towards marine biodiversity is bycatch in fisheries. Under the Marine Strategy Framework Directive (MSFD), EU Member States are required to assess the status of species, such as the harbour porpoise ( Phocoena phocoena ), in relation to their abundance and mortality due to bycatch every six years. The Vulnerable (HELCOM) Belt Sea population of harbour porpoise has been surveyed to determine its abundance six times using dedicated aerial or ship-based line-transect distance sampling surveys. Here, we estimated the first trend in population abundance over an 18 year period (2005-2022). Using the most recent abundance estimate, we computed a mortality limit applying the modified Potential Biological Removal (mPBR) method based on the regionally agreed conservation objective to restore or maintain 80% of carrying capacity over 100 years with an 80% probability. Over the past 18 years there has been a strong negative trend (-2.7% p.a.; 95% CI: -4.1%; + 1.3%) in abundance, with a 90.5% probability. The mortality limit was estimated to be 24 animals, which the current bycatch estimates (~900 porpoises/year from the commercial Danish and Swedish set net fishery fleets, with no data from Germany and other fishery types) exceed by far. The frequency and quality of data available on abundance for this population are higher than those available for the majority of marine species. Given the observed population decline and likely unsustainable levels of bycatch, the results presented here provide a strong basis to make informed, evidence-based management decisions for action for this population. Such action is needed urgently, before the dire situation of other porpoise species and populations around the globe is repeated.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2024.1289808
    DOI: 10.3389/fmars.2024.1289808.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2024
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