scholarly journals Occurrence and distribution of different bed types of seagrass Posidonia oceanica around the Maltese Islands

2009 ◽  
Vol 10 (2) ◽  
pp. 45 ◽  
Author(s):  
J.A. BORG ◽  
A.A. ROWDEN ◽  
M.J. ATTRILL ◽  
P.J. SCHEMBRI ◽  
M.B. JONES
Keyword(s):  
Large Scale ◽  
Posidonia Oceanica ◽  
Eastern Coast ◽  
Small Scale ◽  
Northern Coast ◽  
Maltese Islands ◽  
The North ◽  
Bare Sand ◽  
Sandy Substratum ◽  
Continuous Beds

The small-scale distribution of Posidonia oceanica bed types were mapped at four locations off the northern coast of the Maltese Islands, using aerial photography supplemented by surveys using SCUBA diving. Results showed a similar pattern of occurrence of the seagrass at all locations surveyed. In shallow waters (2 m – 4 m), P. oceanicaoccurred as patches of variable size on a rocky and/or sandy substratum. In deeper waters (5 m – 10 m), the patches of seagrass were often replaced by reticulate beds consisting of P. oceanicainterspersed with areas of bare sand. Deeper still (11 m – 13 m), a transition from reticulate to continuous beds occurred. Continuous beds extended to depths of around 25 - 30 m and eventually became reticulate or patchy in deeper waters (>25 m). Values of total seagrass percentage cover increased, while the ratio of fragmented:continuous bed cover decreased for the four study locations on moving southwards (Ramla Bay to St Thomas Bay), indicating that P. oceanica habitat was more abundant and less fragmented in the south-eastern parts of the Maltese Islands. However, values calculated using an exposure index did not did indicate a relationship between exposure and the observed decease in fragmentation of seagrass beds on moving northwest to southwest along the north-eastern coast. Data from the four sites surveyed, together with data from other surveys, were used to show the large-scale distribution of P. oceanica beds around the Maltese Islands. The implications of the study findings for the conservation and management of P. oceanica habitat around the Maltese Islands are discussed.

scholarly journals Internal tide energy flux over a ridge measured by a co-located ocean glider and moored ADCP

2019 ◽  
Author(s):  
Rob Hall ◽  
Barbara Berx ◽  
Gillian Damerell
Keyword(s):  
Energy Flux ◽  
Large Scale ◽  
Low Frequency ◽  
Internal Tide ◽  
Small Scale ◽  
Potential Density ◽  
The North ◽  
Model Study ◽  
Continental Shelves ◽  
Alternative Approach

Abstract. Internal tide energy flux is an important diagnostic for the study of energy pathways in the ocean, from large-scale input by the surface tide, to small-scale dissipation by turbulent mixing. Accurate calculation of energy flux requires repeated full-depth measurements of both potential density (ρ) and horizontal current velocity (u) over at least a tidal cycle and over several weeks to resolve the internal spring-neap cycle. Typically, these observations are made using full-depth oceanographic moorings that are vulnerable to being fished-out by commercial trawlers when deployed on continental shelves and slopes. Here we test an alternative approach to minimise these risks, with u measured by a low-frequency ADCP moored near the seabed and ρ measured by an autonomous ocean glider holding station by the ADCP. The method is used to measure the M2 internal tide radiating from the Wyville Thompson Ridge in the North Atlantic. The observed energy flux (4.2 ± 0.2 kW m−1) compares favourably with historic observations and a previous numerical model study. Error in the energy flux calculation due to imperfect co-location of the glider and ADCP is estimated by sub-sampling potential density in an idealised internal tide field along pseudorandomly distributed glider paths. The error is considered acceptable (

scholarly journals Morphological description of six species of Suberitida (Porifera: Demospongiae) from the unexplored north-eastern coast of Brazil, with emphasis on two new species

2020 ◽  
Vol 100 (3) ◽  
pp. 389-400
Author(s):  
Humberto F. M. Fortunato ◽  
Thierry Pérez ◽  
Gisele Lôbo-Hajdu
Keyword(s):  
Current Knowledge ◽  
Atlantic Coast ◽  
Marine Sponges ◽  
Eastern Coast ◽  
Morphological Description ◽  
Brazilian Coast ◽  
Northern Coast ◽  
Western Atlantic ◽  
The North ◽  
North Eastern

AbstractThe Order Suberitida is defined as a group of marine sponges without an obvious cortex, a skeleton devoid of microscleres, and with a deletion of a small loop of 15 base pairs in the secondary structure of the 28S rDNA as a molecular synapomorphy. Suberitida comprises three families and 26 genera distributed worldwide, but mostly in temperate and polar waters. Twenty species were reported along the entire Brazilian coast, and although the north-eastern coast of Brazil seems to harbour a rich sponge fauna, our current knowledge is concentrated along the south-eastern Atlantic coast. A survey was implemented along the northern coast of Brazil, and the collection allowed the identification of six species belonging to the Order Suberitida. Two of them are considered new to science: Suberites purpura sp. nov., Hymeniacidon upaonassu sp. nov., and four, Halichondria (Halichondria) marianae Santos, Nascimento & Pinheiro, 2018, Halichondria (H.) melanadocia de Laubenfels, 1936, Suberites aurantiacus (Duchassaing & Michelotti, 1864), and Terpios fugax Duchassaing & Michelotti, 1864, are re-described. Taxonomic comparisons are made for Tropical Western Atlantic species and type species of the four genera. Finally, an identification key for the Western Atlantic Suberites species is provided.

scholarly journals Characteristics of shallow thermally driven flow in the complex topography of the south-eastern Adriatic

2010 ◽  
Vol 28 (10) ◽  
pp. 1905-1922 ◽  
Author(s):  
M. T. Prtenjak ◽  
I. Tomažić ◽  
I. Kavčič ◽  
S. Đivanović
Keyword(s):  
Large Scale ◽  
Sea Breeze ◽  
Small Scale ◽  
The South ◽  
Fine Grid ◽  
Easterly Wind ◽  
Sodar Data ◽  
South Eastern ◽  
The North ◽  
Convergence Zones

Abstract. Characteristics of thermally induced flow, namely the sea breeze, are investigated along the south-eastern Adriatic. The chosen period 24–25 April 2006 favoured sea breeze development and simultaneously allowed a comparison of the large-scale wind influence (north-westerly wind versus south-easterly wind) and the complex terrain on the local circulations. Particular attention is paid to the small-scale formation of the wind field, convergence zones (CZs), channelling flows and small scale eddies, especially in the vicinity of two airports in the central part of south-eastern Adriatic. The results are based on wind measurements (from meteorological surface stations, radiosoundings, satellite data and sodar data) and further supplemented by model data at fine grid spacing. This study shows the formation of numerous irregular daytime and nighttime CZs, which occurred along the coastline in the lee of mountains and over the larger, elongated islands. The results show that the above mentioned airports are surrounded by daytime CZ formations within the lowermost 1000 m and associated updrafts of 1 m s−1, especially if CZs are maintained by the north-westerly large-scale winds. Whereas the daytime CZ was generated due to merged sea breezes, the weaker and shallower nighttime CZs were formed by wind convergence of the seaward breezes, and significantly modified by the large-scale flow of the topography (e.g., accelerated flow in the sea channels and substantial swirled flows around the islands). The passes between the coastal mountain peaks changed the inflow penetration, provoking the increase in wind speed of the channelled flow. The strongest sea breeze channelling was observed above the valley of the Neretva River, where the onshore flow reached 40 km inland with a strength of 8 m s−1, and the highly asymmetric offshore part was confined within the sea channel.

scholarly journals Importance of Resolving Kuroshio Front and Eddy Influence in Simulating the North Pacific Storm Track

2017 ◽  
Vol 30 (5) ◽  
pp. 1861-1880 ◽  
Author(s):  
Xiaohui Ma ◽  
Ping Chang ◽  
R. Saravanan ◽  
Raffaele Montuoro ◽  
Hisashi Nakamura ◽  
...  
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Climate Model ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Small Scale ◽  
Low Resolution ◽  
The North ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Local and remote atmospheric responses to mesoscale SST anomalies associated with the oceanic front and eddies in the Kuroshio Extension region (KER) are studied using high- (27 km) and low-resolution (162 km) regional climate model simulations in the North Pacific. In the high-resolution simulations, removal of mesoscale SST anomalies in the KER leads to not only a local reduction in cyclogenesis but also a remote large-scale equivalent barotropic response with a southward shift of the downstream storm track and jet stream in the eastern North Pacific. In the low-resolution simulations, no such significant remote response is found when mesoscale SST anomalies are removed. The difference between the high- and low-resolution model simulated atmospheric responses is attributed to the effect of mesoscale SST variability on cyclogenesis through moist baroclinic instability. It is only when the model has sufficient resolution to resolve small-scale diabatic heating that the full effect of mesoscale SST forcing on the storm track can be correctly simulated.

Interference fold patterns of the early Precambrian Rock Groups in the Songshan area, China

1982 ◽  
Vol 119 (5) ◽  
pp. 433-461 ◽  
Author(s):  
Shutian Suo ◽  
Ruqi Liu ◽  
Xingyuan Ma
Keyword(s):  
Large Scale ◽  
North China ◽  
Small Scale ◽  
Deformation History ◽  
North China Platform ◽  
Early Proterozoic ◽  
The North ◽  
Regional Deformation ◽  
History Of ◽  
Insight Into

SummaryThe Songshan area is located in the southern part of the North China platform, which is one of the most completely cratonized tectonic units of China. Its basement has experienced a complex evolutionary history and was eventually consolidated at the end of early Proterozoic time about 1.7 Ga ago.A systematic study has been made of the deformation history of the lower Proterozoic Songshan Group and the Archean Dengfeng Group. At least two widespread episodes of deformation can be recognised in the early Proterozoic Zhongyue tectonic cycle and three in the Archean Songyang cycle. Large scale and small scale interference patterns of the superimposed folding are investigated with the aim of recognizing possible regularities in their occurrence and of gaining an insight into the regional deformation history. Two important aspects of superimposition relationships are illustrated: the control of earlier structures upon later ones and the reform of the former by thelatter; their geometrical regularities are also dealt with respectively.

scholarly journals KARAKTERISTIK PERIKANAN TERI (ENGRAULIDAE) DI PANTAI UTARA JAWA-MADURA

2021 ◽  
Vol 26 (3) ◽  
pp. 135
Author(s):  
ACHMAD ZAMRONI ◽  
Heri Widiyastuti ◽  
Suwarso Suwarso
Keyword(s):  
North Coast ◽  
Small Scale ◽  
Fishing Gear ◽  
Eastern Region ◽  
Northern Coast ◽  
Catch Per Unit Effort ◽  
Fishing Season ◽  
The North ◽  
Fishing Vessels ◽  
Landing Sites

Perikanan teri berkembang sangat pesat khususnya di perairan utara Jawa Madura pada tahun terakhir ini. Kajian tentang karakteristik perikanan teri (Engraulidae) di sepanjang pantai utara Jawa-Madura dilaksanakan pada tahun 2017-2018, meliputi sebaran usaha perikanan, tipe armada-alat penangkapan ikan, aspek operasional penangkapan, hasil tangkapan-kelimpahan dan musim penangkapan ikan teri. Pengumpulan data pendaratan ikan teri dilakukan melalui survey di 11 lokasi pendaratan ikan. Hasil penelitian menunjukkan terdapat 12 lokasi tempat pendaratan utama ikan teri di sepanjang pantai utara (pantura) Jawa dan Madura. Dua jenis alat dominan digunakan untuk penangkapan teri adalah pukat cincin dan payang; perikanan bersifat skala kecil, melakukan trip harian, dengan armada kapal penangkap berukuran dibawah 20 GT. Jaring umumnya menggunakan waring dengan mata jaring kecil (3/8 inch) di bagian kantong. Daerah penangkapan di perairan pantai yang dangkal, dekat dengan basis perikanan. Musim penangkapan ikan teri bervariasi, di wilayah bagian barat (Pulolampes, Larangan, Morodemak) berlangsung sekitar musim timur/tenggara (Mei Juli), sedangkan di wilayah bagian timur berlangsung pada awal musim timur dan berjalan cukup lama hingga bulan November (musim peralihan 2). Hasil tangkapan per unit upaya (CPUE, sebagai indek kelimpahan) diduga makin ke arah timur semakin rendah namun disertai musim penangkapan ikan lebih lama. Anchovy fishery has grown rapidly, especially in the northern waters of Java-Madura in the last year. The study on the characteristics of the anchovy fishery (Engraulidae) along the northern coast of Java-Madura was carried out in 2017-2018, covering the distribution of fisheries effort, types of fishing gear, operational aspects of fishing, catch-abundance and fishing season. The collection of anchovy landing data was carried out through a survey at 11 fish landing sites. The results showed that there were 12 main anchovy landing sites along the north coast (pantura) of Java and Madura. Two types of dominant fishing gear used for anchovies are purse seine and payang; Fisheries are small-scale, undertaking daily trips, with a fleet of fishing vessels under 20 GT. The nets generally use “waring” with small mesh (3/8 inch) in the codend. Fishing area in shallow coastal waters, close to the fishing base. The fishing season for anchovy varies, in the western region (Pulolampes, Larangan, Morodemak) it takes place around the east / southeast season (May-July), while in the eastern region it takes place at the beginning of the eastern season and lasts quite a long time until November (transition season 2) . The catch per unit effort (CPUE, as an abundance index) is thought to be getting lower eastward but accompanied by a longer fishing season.

scholarly journals Soil cover patterns in the forest-steppe and steppe zones of the East European Plain

2019 ◽  
Vol 70 (3) ◽  
pp. 198-210
Author(s):  
Nikolay Khitrov ◽  
Maria Smirnova ◽  
Nikolai Lozbenev ◽  
Ekaterina Levchenko ◽  
Vasiliy Gribov ◽  
...  
Keyword(s):  
Large Scale ◽  
Soil Cover ◽  
Parent Material ◽  
Soil Mapping ◽  
East European Plain ◽  
Small Scale ◽  
Forest Steppe ◽  
East European ◽  
The North ◽  
Haplic Chernozems

Abstract The soil cover of the forest-steppe and steppe zones of the East European Plain is characterized by diverse soil combinations revealed during large-scale and detailed soil mapping against the background of a traditional zonal sequence of dominant automorphic soils alternating from the north to the south and clearly displayed on small-scale soil maps. The composition, configuration and functioning of particular soil cover patterns are determined by the soil forming factors acting within a given area. The elementary soil areas (detailed scale) and elementary soil cover patterns maps (large scale) of the Central Russian, Kalach, and Volga Uplands are created by both traditional and digital soil mapping methods. Low-contrasting soil combinations with the background Haplic Chernozems (Loamic or Clayic, Pachic) alternating with zooturbated Haplic Chernozems (Loamic or Clayic, Pachic) on convex elements of the microtopography and Luvic Chernozems (Loamic or Clayic, Pachic) on concave elements of the microtopography prevails under conditions of thick clay loamy parent materials and free drainage. Under conditions of shallow embedding by low-permeable clayey sediments, the soil cover includes Chernozems or Chernic Phaeozems with stagnic features in some part of the soil profile or even Mollic Stagnosols. The presence of shrink-swell clays of different ages leads to the formation of Bathyvertic Chernozems, Vertic Chernozems, Vertic Chernic Phaeozems and/or Pellic Vertisols. The presence of soluble salts in the parent material leads to the development of solonetzic soil complexes consisting of Protosodic or Sodic Chernozems and different types of Solonetzes.

scholarly journals PERANAN “BANTAL SOSIAL” PADA MATA PENCAHARIAN NELAYAN SKALA KECIL DI JAWA

2016 ◽  
Vol 11 (2) ◽  
pp. 225
Author(s):  
Budi Wardono ◽  
Akhmad Fauzi
Keyword(s):  
North Coast ◽  
Small Scale ◽  
Northern Coast ◽  
Analysis Model ◽  
The North ◽  
Logistic Analysis ◽  
The Status ◽  
Long Time ◽  
Quantitative Analysis Method ◽  
High Earning

Salah satu alasan yang kuat nelayan tangkap skala kecil tetap melaut meskipun mempunyai risiko tinggi karena peluang/prospek pendapatan/penerimaan yang tinggi pada satu saat. Risiko melaut tidak hanya membuat ketidakpastian tetapi juga karena risiko biaya operasional yang tinggi. Dihadapkan dengan kondisi biaya operasional yang  tinggi, nelayan menggunakan strategi yang berbeda, salah satunya melekat pada peran tengkulak. Dalam pandangan konvensional, pedagang perantara/ langgan sebagai hambatan bagi nelayan untuk menjadi kompetitif di pasar. Namun di negara berkembang seperti Indonesia, mereka memainkan peran penting sebagai "bantal sosial" dalam kehidupan nelayan skala kecil. Tujuan penelitian adalah menyelidiki tingkat kecenderungan keterikatan hubungan langgan/pedagang antara sebagai “bantal sosial” dengan nelayan di dua daerah penangkapan ikan yang menonjol di pantai utara dan pantai selatan Jawa. Analisis data dilakukan dengan metode analisis kuantitatif yaitu model analisis multinomial logistik. Hasil penelitian menunjukkan bahwa nelayan dari pantai utara cenderung sangat kuat hubungannya dengan perantara untuk kelangsungan hidupnya dibandingkan dengan nelayan di pantai selatan. Implikasi dari temuan tersebut bahwa peran sentral langgan/perantara/tengkulak/langgan merupakan bentuk hubungan yang bersifat ekonomi dimana kedua belah pihak bisa mengambil keuntungan. Pola hubungan bukan hanya sekedar sebagai penyangga, namun lebih dari itu yaitu berfungsi sebagai “bantal” sosial (social cushion) para nelayan. Hubungan seperti ini merupakan bentuk layanan dimana para nelayan bisa mendapatkan alternatif layanan jasa “kredit” dari para perantara/langgan/tengkulak. Bentuk layanan seperti yang diperankan oleh langgan/pedagang perantara selama ini belum bisa digantikan oleh lembaga pemerintah yang resmi, dimana pola hubungan tersebut sangat dibutuhkan oleh nelayan skala kecil. Pola hubungan tersebut selain dipengaruhi oleh lokasi, juga dipengaruhi oleh status kepemilikan kapal, lama kepemilikan kapal dan jumlah ABK.Title: The Role “Social Cushion” On The Livelihood Of Small Scale Fishers In JavaOne of the strong reason for small scale fishers to keep fishing despite high risk of fishing, is the prospect of high earning at one moment in time. Risk at fishery not only  create uncertaining but also risk high cost of fishing. Faced with such a high cost, fishers use different strategies, one of which is attached to the middlemen. Convientional views middlemen as an obstacle for fishers to be competitive in the market. Yet in developing country such us Indonesia, they play crucial role as a “social cushion” in the livelihood of small scale fishers. The purpose of research is to investigate the tendency of engagement relationships middleman as "social cushion" with fishermen in the fishing areas that stand out on the north coast and the south coast of Java. Data was analyzed using quantitative analysis method multinomial logistic analysis model. Results of this study show that fishers of the northern coast tend to strongly attach to middlemen for their survival compared with those in the southern coast.  Relationships with fishermen middlemen is a service, where fishermen can get alternative services "credit" from the middleman. Services such as that played by middleman has not been able to replace them by official government agencies, where this kind of relationship is needed by small-scale fishermen. The relationship patterns in addition affected by the location, also influenced by the status of ownership of the vessel, long time ship ownership and the number of crew.  

scholarly journals From Ripples to Large-Scale Sand Transport: The Effects of Bedform-Related Roughness on Hydrodynamics and Sediment Transport Patterns in Delft3D

2020 ◽  
Vol 8 (11) ◽  
pp. 892
Author(s):  
Laura Brakenhoff ◽  
Reinier Schrijvershof ◽  
Jebbe van der Werf ◽  
Bart Grasmeijer ◽  
Gerben Ruessink ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Water Movement ◽  
Small Scale ◽  
Sand Transport ◽  
Influence Model ◽  
The North ◽  
Ebb Tidal Delta ◽  
Transport Patterns ◽  
Set Up

Bedform-related roughness affects both water movement and sediment transport, so it is important that it is represented correctly in numerical morphodynamic models. The main objective of the present study is to quantify for the first time the importance of ripple- and megaripple-related roughness for modelled hydrodynamics and sediment transport on the wave- and tide-dominated Ameland ebb-tidal delta in the north of the Netherlands. To do so, a sensitivity analysis was performed, in which several types of bedform-related roughness predictors were evaluated using a Delft3D model. Also, modelled ripple roughness was compared to data of ripple heights observed in a six-week field campaign on the Ameland ebb-tidal delta. The present study improves our understanding of how choices in model set-up influence model results. By comparing the results of the model scenarios, it was found that the ripple and megaripple-related roughness affect the depth-averaged current velocity, mainly over the shallow areas of the delta. The small-scale ripples are also important for the suspended load sediment transport, both indirectly through the affected flow and directly. While the current magnitude changes by 10–20% through changes in bedform roughness, the sediment transport magnitude changes by more than 100%.

Metasomatism in the Whin Sill of the North of England. Part II: Hydrothermal Alteration by Juvenile Solutions

1929 ◽  
Vol 66 (5) ◽  
pp. 221-238 ◽  
Author(s):  
L. R. Wager
Keyword(s):  
Thin Layer ◽  
Hydrothermal Alteration ◽  
Outer Surface ◽  
Large Scale ◽  
General Character ◽  
Small Scale ◽  
Hydrothermal Solutions ◽  
Vein Quartz ◽  
Columnar Jointing ◽  
The North

In Teesdale and Weardale, at all exposures that have been examined, the Whin Sill is cut by a system of approximately vertical, sweeping, joint planes. These are distinct in general character from, and are on a larger scale than, the columnar jointing which is conspicuous in all vertical scars of Whin Sill. The pattern of the larger scale jointing on a horizontal surface varies with the depth within the sill; Fig. 1 shows diagrammatically the appearance at a depth of about 10 feet below the top of the sill; the inset Fig. 2, of the upper surface of the sill, shows how the joints have a more irregular course in the more rapidly cooled part of the dolerite. The joints do not usually pass from the dolerite into the adjacent sediment and Fig. 2 also shows a thin layer of baked sediment, attached to the outer surface of the sill, which the joint does not penetrate. The large scale jointing is often displaced by the small scale columnar jointing in a way that proves the large scale jointing to be the earlier. For the purposes of this paper, the early, large scale, joints will be referred to simply as the early joints. The walls of the early joints, for a distance of an inch or so, have been altered by hydrothermal solutions, to a rock which, although varying in composition with the distance from the joint, consists essentially of chlorite, quartz, and carbonate. The joint walls are usually about a quarter of an inch apart, and the space between them is filled with calcite and quartz. The calcite is present in greater abundance than the quartz which occurs in well shaped crystals of vein-quartz habit.

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