scholarly journals Open water camouflage via ‘leaky’ light guides in the midwater squid Galiteuthis

2016 ◽  
Vol 13 (119) ◽  
pp. 20160230 ◽  
Author(s):  
Amanda L. Holt ◽  
Alison M. Sweeney
Keyword(s):  
Angular Distribution ◽  
Open Water ◽  
Light Environment ◽  
Cross Sectional ◽  
Isotropic Source ◽  
Vertical Range ◽  
Light Guides

Galiteuthis , a midwater squid, has photophores on the ventral surfaces of its eyes. These photophores emit bioluminescence to counter-illuminate the shadows cast by the eyes in downwelling sunlight, thereby hiding the eyes from upward-looking predators. The photophores consist of laminated fibre-like cells with semi-coaxial protein-dense layers around axial cytoplasm. These cells have been suggested to function as light guides: bioluminescence is an isotropic process used to hide in an anisotropic light environment, so any emission must be reshaped to be effective. We found a wide variation in cross-sectional geometries of photophore cells; some were more efficient at light guiding than others. We used a set of optical models to place these photophores in the context of the radiance where Galiteuthis lives and discovered a possible adaptive reason for this variation. In Galiteuthis 's horizontal and vertical range, ocean radiance is also quite variable. For complete camouflage, photophores must reproduce this variation in radiance using an isotropic source. Our models show that variation in the geometry of the photophore light guides reproduces the predicted variation in ocean radiance experienced by this species. By selectively activating geometrically distinct populations of photophore cells, the animal may reproduce the angular distribution of light at all positions in its habitat.

scholarly journals A COMPARISON BETWEEN GERMAN AND NORTH AMERICAN TIDAL INLETS

1988 ◽  
Vol 1 (21) ◽  
pp. 199
Author(s):  
Reinhard Dieckmann ◽  
Manuela Osterthun ◽  
Hans Werner Partenscky
Keyword(s):  
Salt Marshes ◽  
Morphological Structure ◽  
Open Water ◽  
Coastal Structures ◽  
Tidal Inlets ◽  
Cross Sectional ◽  
Short Account ◽  
Shaping Process ◽  
Geomorphological Parameters ◽  
Good Agreement

Initial results are presented relating to an investigation of geomorphological parameters from 26 of a total of 28 tidal inlets and 11 coastal structures similar to inlets along the German Bight. The following parameters were investigated: - tidal prism - inlet area relationship, - cross-sectional form and depth, - location of the channel within the cross-section, - ebb tidal deltas and - the structures of the back barrier regions. The most important parameter governing the shaping process of these coastal structures is considered to be the tidal volume. The results of the investigations were compared with data from American publications. Despite the differences between the regions studied, in overall terms, surprizingly good agreement was obtained between the parameters investigated. Notable differences exist only in relation to the morphological structure of the back barrier regions (tidal flats, salt marshes, open water lagoons). In respect of the latter differences, a short account is given of the biological and climatological influencing factors.

A review of ground-penetrating radar studies related to peatland stratigraphy with a case study on the determination of peat thickness in a northern boreal fen in Quebec, Canada

2013 ◽  
Vol 37 (6) ◽  
pp. 767-786 ◽  
Author(s):  
Sandra Proulx-McInnis ◽  
André St-Hilaire ◽  
Alain N. Rousseau ◽  
Sylvain Jutras
Keyword(s):  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Open Water ◽  
Coefficient Of Determination ◽  
Cross Sectional ◽  
Soil Thickness ◽  
Shallow Subsurface ◽  
Observation Method ◽  
Time Required ◽  
Ground Penetrating

Ground-penetrating radar (GPR) is a non-intrusive geophysical observation method based on propagation and reflection of high-frequency electromagnetic waves in the shallow subsurface. The vertical cross-sectional images obtained allow the identification of thickness and lithologic horizons of different media, without destruction. Over the last decade, several studies have demonstrated the potential of GPR. This paper presents a review of recent GPR applications to peatlands, particularly to determine peat stratigraphy. An example study of acquisition and comparison of peatland soil thickness of a fen-dominated watershed located in the James Bay region of Quebec, using (1) a meter stick linked to a GPS RTK and (2) a GSSI GPR, is given. A coefficient of determination ( r2) of 56% was obtained between the ordinary krigings performed on data gathered using both techniques. Disparities occurred mainly in the vicinity of ponds which can be explained by the attenuation of GPR signal in open water. Despite these difficulties – the higher time required for analysis and the error margin – it seems more appropriate to use a GPR, instead of a graduated rod linked to a GPS, to measure the peat depths on a site like the one presented in this study. Manual measurements, which are user-dependent in the context of variable mineral substrate densities and with the presence of obstacles in the substrate, may be more subjective.

scholarly journals The water temperature characteristics of the Lena River at basin outlet in the summer period

2016 ◽  
Author(s):  
Vera Fofonova ◽  
Igor Zhilyaev ◽  
Marina Krayneva ◽  
Dina Yakshina ◽  
Nikita Tananaev ◽  
...  
Keyword(s):  
Water Temperature ◽  
Observational Data ◽  
Open Water ◽  
Data Series ◽  
Cross Sectional ◽  
Lena River ◽  
Temperature Characteristics ◽  
The North ◽  
Temperature Trends ◽  
Deterministic Modelling

Abstract. The water temperature characteristics of the Lena River at basin outlet during the summer season (June–September) are considered. The analysis is based on a long-term data series covering the period from the beginning of observation (1936) to the present time (2012) at Kusur (Kyusyur) gauging station and complementary data at several stations downstream and one station upstream. These additional data are rarely used, but their analysis is important for understanding processes in the basin outlet area. The differences between the stream surface temperatures at Kusur station and 200 km downstream to the north at Habarova (Khabarova) station have almost always been an anomalously large and negative for the considered period since the beginning of observation during open water season from July to September. The description of this difference and its analysis are presented. To sort the problem out, we consider the observational data in terms of the hydrology and morphology of the Lena River delta and main channel area and apply statistical and deterministic modelling approaches. The inability of water temperature observational data at Kusur station to represent the mean cross-sectional temperature is addressed. The analysis of the water temperature trends at the Kusur and Habarova stations is also presented.

scholarly journals Current Status of Schistosoma mansoni Infections and Associated Risk Factors among Students in Gorgora Town, Northwest Ethiopia

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Tarko Essa ◽  
Yemane Birhane ◽  
Mengistu Endris ◽  
Asmeret Moges ◽  
Feleke Moges
Keyword(s):  
Risk Factors ◽  
Intestinal Parasites ◽  
Open Water ◽  
Water Source ◽  
Northwest Ethiopia ◽  
Current Status ◽  
Stool Examination ◽  
Water Contact ◽  
Cross Sectional ◽  
Associated Risk Factors

Background and Objective. Schistosomiasis is highly prevalent in tropics and causes morbidity and mortality in developing countries including Ethiopia. This study is aimed to assess the current status of S. mansoni infections and associated risk factors among students in Gorgora town, Northwest Ethiopia. Method. A cross-sectional study was conducted from October 2010 to November 2010 at Gorgora, Northwest Ethiopia. All students (579) present during the study period were enrolled. Pretested questionnaires were used to collect sociodemographic data and predisposing factors. Stool examination was performed using wet mount and Kato-Katz techniques. Data were entered and analysed using SPSS version 20.0 statistical software. Result. Among 579 students enrolled, 291 (50.3%) were positive for one or more intestinal parasites. Prevalence of S. mansoni was found to be 20.6% with mean intensity of infection (125 eggs per gram of feces). Lack of awareness and water contact habits such as frequent swimming in the open water source, agricultural activities on bare foot, and washing clothes were also associated with high risk of S. mansoni infection. Conclusion. Even though there seems to be a decline in the prevalence of S. mansoni infections in the study area, the problem still persists and affects students significantly. Therefore, therapeutic intervention and health education are needed.

Nonstationary angular distribution of optical field radiance from an isotropic source in sea water

2020 ◽  
Vol 59 (20) ◽  
pp. 6046
Author(s):  
Alexander G. Luchinin ◽  
Mikhail Yu. Kirillin ◽  
Lev S. Dolin
Keyword(s):  
Angular Distribution ◽  
Sea Water ◽  
Optical Field ◽  
Isotropic Source

Prevalence and severity of external auditory exostoses in breath-hold divers

2008 ◽  
Vol 122 (11) ◽  
pp. 1162-1167 ◽  
Author(s):  
P W Sheard ◽  
M Doherty
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Open Water ◽  
Sea Surface ◽  
Stepwise Multiple Regression ◽  
Breath Hold ◽  
Published Data ◽  
Cross Sectional ◽  
Breathing Apparatus ◽  
Chi Square Analysis

AbstractObjective:To explore the prevalence and severity of external auditory exostoses in a population of experienced breath-hold divers, and to compare these to the same parameters within surfing and self-contained underwater breathing apparatus diving populations.Design:A stepwise, multiple regression analysis of cross-sectional data examining the relative contributions of sea surface temperature, latitude of exposure and years of exposure to the prevalence and severity of stenosis due to external auditory exostoses. A chi-square analysis of the prevalence and severity of external auditory exostosis stenosis in the breath-hold divers was compared with previously published data for surfers and self-contained underwater breathing apparatus divers.Subjects:Seventy-six male and thirty-five female breath-hold divers attending an international ‘freedive’ competition completed a questionnaire describing aquatic sports habits, geography of participation and symptomatology. Those completing the questionnaire (111/154 attendees) were examined otoscopically for evidence of external auditory exostoses. Images were digitally recorded, scored and graded.Results:Exostoses were evident in 87.7 per cent of the 204 ears scored and graded for severity of stenosis due to external auditory exostoses. The prevalence of exostoses was no different from that found in previous studies of surfers and self-contained underwater breathing apparatus divers (p = 0.101). However, the pattern of affliction was more similar to that found in surfers. The severity of exostoses was significantly less than that found in surfing populations (p ≤ 0.001 to 0.007), but greater than that found in self-contained underwater breathing apparatus diving populations (p ≤ 0.001). Sea surface temperature at the location of open-water exposure was the most significant predictor of the prevalence and severity of external auditory exostoses in breath-hold divers (p = 0.019).Conclusion:The prevalence and severity patterns of stenosis due to external auditory exostoses in breath-hold divers are more similar to previously published results for surfing populations than to previously published results for self-contained underwater breathing apparatus diving populations. In breath-hold divers, sea surface temperature is the strongest predictor of severity of stenosis due to external auditory exostoses.

scholarly journals Under-ice mesocosms reveal the primacy of light but the importance of zooplankton in winter phytoplankton dynamics

2019 ◽  
Author(s):  
Allison R. Hrycik ◽  
Jason D. Stockwell
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Food Webs ◽  
Soluble Reactive Phosphorus ◽  
Open Water ◽  
Light Environment ◽  
Zooplankton Grazing ◽  
Ice Dynamics ◽  
Reactive Phosphorus

AbstractFactors that regulate planktonic communities under lake ice may be vastly different than the open-water season. However, under-ice food webs in temperate lakes are poorly understood, despite expected changes in light availability, ice cover, and snowfall associated with climate change. We hypothesized that light limitation (bottom-up control) outweighs zooplankton grazing (top-down control) on phytoplankton biovolume and community structure under ice in a north temperate lake. Using in situ under-ice mesocosms, we found that light had stronger effects on phytoplankton abundance than zooplankton, as expected. Specifically, low light limited growth of diatoms, cryptophytes, chrysophytes, and chlorophytes. Zooplankton, however, also significantly affected phytoplankton by decreasing diatoms and cryptophytes, in contrast to the common assumption that zooplankton grazing has negligible effects under ice. Ammonia and soluble reactive phosphorus decreased in high light treatments presumably through uptake by phytoplankton, whereas ammonia and soluble reactive phosphorus increased in high zooplankton treatments, likely through excretion. In situ experimental studies are commonly applied to understand food web dynamics in open-water conditions, but are extremely rare under ice. Our results suggest that changes in the light environment under ice have significant, rapid effects on phytoplankton growth and community structure and that zooplankton may play a more active role in winter food webs than previously thought. Changes in snow and ice dynamics associated with climate change may alter the light environment in ice-covered systems and significantly influence community structure.

scholarly journals Beneath the surface: mental health, and harassment and abuse of athletes participating in the FINA (Aquatics) World Championships, 2019

2021 ◽  
Author(s):  
Margo Mountjoy ◽  
Astrid Junge ◽  
Christer Magnusson ◽  
Farhad Moradi Shahpar ◽  
Edgar Ivan Ortiz Lizcano ◽  
...  
Keyword(s):  
Mental Health ◽  
Eating Disorders ◽  
Mental Health Problems ◽  
Open Water ◽  
Cross Sectional Study ◽  
Health Issues ◽  
Sectional Study ◽  
Cross Sectional ◽  
Mental Health Issues ◽  
Anonymous Questionnaire

Objective: To assess the mental health and experience of sport-related harassment and abuse of athletes participating in the FINA World Championships 2019, and to analyse it in relation to gender and the aquatic disciplines. Design: Cross-sectional study using an anonymous questionnaire. Methods: During the Championships, registered athletes (swimmers, divers, high divers, water polo players, artistic swimmers, open-water swimmers) completed a survey including the main outcome measures of depression (CES-D-10), eating disorders (BEDA-Q), the subjective need for psychotherapeutic support, and the experience of harassment and/or abuse in their sports environment. Results: A quarter of the athletes (n=62, 24.6%) were classified as depressed and more than a third (n=111, 35.0%) as having an eating disorder. More than 40% of the athletes stated that they wanted or needed psychotherapeutic support for mental health problems. Fifty-one athletes (14.9%) had experienced harassment/abuse in sport themselves, and 31 (9%) had witnessed it in another athlete. The experiences of harassment and abuse ranged from unwanted comments about body or appearance (40.2%) to rewards in sport for sexual favours (2.5%) and rape (0.3%). Athletes who had experienced harassment/abuse in sport themselves had higher average scores for depression and eating disorders, and more of them needed psychotherapeutic support. Up to a third would not talk to anybody if they saw or experienced harassment/abuse, and less than 20% would talk to an official for help. Conclusion: Targeted initiatives are required to address the burden of mental health issues and harassment and abuse in sport in the FINA aquatic disciplines.

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