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Sunday, 7 November 2021

Sandbars

 


Sandbars are the long masses or low ridge of submerged or partially exposed sand built up in the water along a shore or beach. Sandbar also known as the offshore bars. Sandbar form due to action of waves and currents. Sandbar begin forming underwater and they are usually formed by sand or coarse sediment deposition offshore from a beach. Large waves can build sandbars far from shore during heavy storms and it build up until they rise above the water’s surface. Sometimes sandbars are formed in between two nearby beaches forming a connection between the two. Due to backwash and the rip currents of the water body, more and more sand deposition can occur. Normally, top part of the sandbar lies below the water level, and still-water level or the half-wave height is the water level under which the sandbars are normally submerged.

Bay-mouth bars are the one form of sandbars and they are formed extending partially or entirely across the mouth of a bay. Bay-head bars occur at the heads of bays and they form short distance from the shoreline. Barrier bars formed from the exposed sandbars that can have formed during the high-tide season, and those barrier bars are separated from the beaches by shallow lagoons cutting off the beach from the open sea. Barrier bars occurs around the coastal plains off the shore but except the regions which have rocky landforms.

Sand, gravel and other sediments can gather underwater in large amount when waves are large, and it leads to block channels and prevent ships and boats from passing. And also continuous wave actions and storms can build a sandbar until it becomes a barrier island, and this barrier island provide protection for the channel and the mainland shore behind.

 

Famous sandbars (Barrier islands)

·       Miami Beach, Florida, USA

·       Bolivar Island, Texas, USA

There are 4 types of sandbars present in various estuaries. They are compound, U-shaped, linear and sidebar.


The water behind the sandbars can form tidal pools, lagoons, salt marshes and other wetlands, and variety of marine life can grow in these areas. And these areas are home for a variety of fish and shellfish.

Sandbars are either completely or partially submerged landforms of sand and silt sediments but most often they are submerged inside the water. When they are visible and above the water, there are more chance to get it submerged inside the water again. Because of that, sometimes sandbars can be dangerous. But sandbars are very important because they provide stability to the beach as they reduce the energy of the waves by breaking them and they prevent the severe erosion.


Sandbars create beautiful locations. Due to their nature they attract a lot of tourists, and eatery & beverages business have boomed in sandbars areas.  And also, those sandbar beaches are prime locations for shootings and beautiful locations in the movies. 


Article by - Tashani Chandrasiri 

References:

https://www.vedantu.com

http://worldlandforms.com

https://researchgate.net

 

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Sunday, 31 October 2021

Belize Barrier Reef

Belize Barrier Reef, coral reef that is the second largest in the world after Australia's Great Barrier Reef and the largest of its kind in the Northern and Western hemispheres. It stretches for more than 180 miles (290 kilometers) along Belize's Caribbean coast, with an offshore distance ranging from about 1,000 feet (300 meters) in the north to 25 miles (40 kilometers) in the south, except at Rocky Point, where it meets the shoreline. The contiguous Bacalar Chico National Park and Marine Reserve, Blue Hole Natural, Half Moon Caye Natural Monument, Glover's Reef Marine Reserve, South Water Caye Marine Reserve, Laughing Bird Caye National Park, and Sapodilla Marine Reserve protect the 370-square-mile (960-square-kilometer) area (1996).


The reef and its atolls contain nearly 450 mangrove cays and sandy islands of varying sizes, including the Western Hemisphere's only coral atolls. The area is home to several rare and endangered animal species, including the American crocodile and the world's largest population of West Indian manatees. Sea turtles, red-footed boobies, and other seabirds are also common, as are more than 500 species of fish, 65 species of stony corals (Scleractinia), and 350 varieties of mollusks. Above water, there are 178 plant species, and below water, there are 247 types of marine flora; algal varieties abound, as do turtle and manatee sea-grass beds.


The reef's tropical climate, with average temperatures ranging from 61 °F (16 °C) in winter to 88 °F (31 °C) in summer, and its extraordinary fauna have made it a popular tourist destination. Historically, its main draw was as a fishing and trading center; the Maya used it for this purpose from around 300 BCE to 900 CE, and in the 17th century, pirates of Scottish and English descent, who had first sought safety at the reef, exploited its resources as well. Even though it is threatened by the effects of water sports, sightseeing boats (whose anchors tear apart sections of the reef), and fishing, the reef has been kept largely accessible to watercraft due to its importance to the tourism and fishing industries. The reef is a major source of seafood, particularly lobster and conch, and a large portion of it is exported. Every year, between 100,000 and 150,000 tourists visit the area, congregating around snorkeling and diving hotspots like San Pedro, Caye Caulker, and Placencia. In 1996, the Belize Barrier Reef was designated a UNESCO World Heritage site.




Article by - Naveen Lakshitha

References:



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Sunday, 24 October 2021

A “living hell” vs A “never-never land”

 Earlier last May, the MV X-Press Pearl carrying chemicals caught fire off the western coast of Sri Lanka. It has been such an environmental disaster and this might be a difficult decade for marine life. Although the ship has already been sunken off and the thick dark smoke that could see from miles away has been stopped, the problems have only just begun. Most of them are; the highly dangerous chemicals have already leaked into the ocean and occurred a number of deaths of marine animals such as fishes, turtles and dolphins who had beached by turning into a greenish colour, suggesting contamination with chemicals and metals; Nitric acid, Copper and Lead, additionally tons of tiny plastic pellets have already been beached by increasing the number of deaths of fishes by stuck in their gills and dolphins by stuck in their stomachs. The most long- lasting impact is the chemical pollution, which make their way into the bellies of the local marine life. Small fish might be die quickly but the bigger ones are less likely to. When feeding on smaller fish the toxins will slowly build up in their bodies over time.



Not only this disaster but also the human impact on marine life has been the hugest problem for marine animals and habitats in this 21st century where humans are walking through a technologically and scientifically improved world by ignoring that the marine animals are the ancestors of them. Ocean pollution, overfishing and ocean acidification are the main impacts on the marine animals. Mainly, ocean pollution results from the wastes added through land-based activities like industrial, agricultural, and residential by plastic, polythene, fertilizers, oil, chemicals, dirt and gravel etc. These pollutants may degrade or destroy habitat for marine life by contaminating the untreated waste.

Over 300 million of plastic are produced every year, half of them are single-used. Sadly, at least 8 million tons of plastic enter the oceans every year and it is estimated that about 150 million metric tons of plastic exists in our oceans. Plastics are light, therefore much of these can be seen on the surface but plastic trash and particles are now found in marine habitats, including deep sea, coral reefs, beaches etc. This can bring seabirds, whales, fish and turtles to die of starvation with plastic filled stomachs and they can also be suffocated or entangled in these garbage.  


Untreated water is contained excess nutrients such as nitrates and phosphates by dumping of human sewage into water bodies which lead to stimulate algae growth. These algae then die, sink and is decomposed by bacteria in the water. This process consumes oxygen depleting the supply for other marine life and creating what is referred to as a “dead zone”. Dead zones are hypoxic therefore this kills off marine life or forces it to leave the area. This process can be occurred naturally, but human activity has turned this natural process into an environmental problem.

Overfishing is occurring in one third of world fish stocks and it has led to the habitat loss. Significant habitat loss is particularly occurring in seagrass meadows, mangrove forests and coral reefs. Coral reefs are among the more productive and diverse ecosystems on the planet, but one fifth of them have been lost. Seagrass meadows are the provisions of food and habitats for many marine animals but unfortunately seagrass meadows have lost 30,000 km2 during recent decades. One-fifth of the world’s mangrove forests have also been lost.

Ocean acidification is caused mainly by the uptake of CO2 from the atmosphere doe to the burning of fossil fuels. When CO2 dissolves in water it forms hydrogen and carbonate ions by increasing the acidity of sea water and makes harder for marine organisms mainly that depend on calcium carbonate to form their shells and causes coral bleaching.

Now we can comment on whether ocean has been either a living hell or a never-never land for marine animals. Of course it was a never-never land before the industrial revolution; no factories- no environment pollution. But it doesn’t mean that we shouldn’t develop with the technology, with the development we should be able to overcome these issues. There are some proposed solutions for overfishing; make government regulations (fishing quotas, closed seasons, marine reserves etc.), removal of subsidies, minimizing fishing impact, aquaculture, consumer awareness, ocean pollution; only two ways either the human population is reduced or a way is found to reduce the ecological footprint left behind by the average human and ocean acidification; bioenergy with carbon capture and storage, direct air capture to remove CO2 from ambient air, afforestation, reforestation and forest restoration, creating bio char (i.e. in biomass-fired thermal power plants, for mixing into the soil to create terrapreta [black soil]). If we are responsible with the rules and regulations and also with our behaviour, we would be able to make a never-never land definitely for our ancestors; marine life. 

Article by  –  H C Jayani N De Silva

References

1. Ranga Sirilal and Andreas Illmer, BBC News, updated on 10th June 2021 for the details that caused an environmental disaster by the X-Press Pearl

2. UNESCO Natural Sciences, IOC Oceans (pdf), Ocean acidification

3. Patin, S.A. “Anthropogenic impact in the sea and marine pollution” retrieved 1st February 2018

4. Raven, J.A. (2005). Ocean acidification due to increasing atmospheric carbon dioxide. Royal Society, London, UK

5. Warner, Robin (2009). Protecting the Oceans Beyond National Jurisdiction 

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Wednesday, 20 October 2021

Alongshore webinar series 1.0 ; Webinar #5

බොහොමයක් ශාක හා සත්ත්ව විශේෂ වල පැවැත්ම තහවුරු කරමින් පරිසර පද්ධති සඳහා වෙනත් විවිධාකාර සේවාවන් රාශියක් සපයන කඩොලාන ප්‍රජාව, දශක තුනක පමණ කාලයක සිට වනහරණය හා අනිසි භාවිතය හේතුවෙන් පිළියම් කළ නොහැකි ආකාරයෙන් විනාශ වෙමින් පවතියි.  එබැවින් කඩොලාන නිවැරදි ආකාරයෙන් කළමනාකරණය පිළිබඳ අප දැනුවත් විය යුතුව ඇත.

ශ්‍රී ජයවර්ධනපුර විශ්වවිද්‍යාලයේ ජලජ ජීව විද්‍යා ශිෂ්‍ය සංගමය මඟින් සංවිධානය කරනු ලබන සම්මන්ත්‍රණ මාලාව "Alongshore", එහි පස්වන පියවර තබමින් "කඩොලාන තාත්වික කළමනාකරණය සඳහා විද්‍යාව හා පාලනය" පිළිබඳ හරවත්, විද්වත් ඒ වගේම රසවත් කතිකාවතක් ගොඩනගමින් ඔබව දැනුවත් කිරීමට අපි සූදානම් .

මෙවර සාකච්ඡාව සඳහා සම්පත් දායකත්වය, වයඹ විශ්ව විද්‍යාලයේ පශු සම්පත් ධීවර හා පෝෂණ පීඨයේ ජ්‍යෙෂ්ඨ මහාචාර්ය සෙව්වන්දි ජයකොඩි මහත්මියයි.

දිනය        - ඔක්තෝබර් මස 22 වන සිකුරාදා 
වේලාව     - පස්වරු 5 සිට 6 දක්වා 

මාර්ගගත ක්‍රමයන් ඔස්සේ ZOOM තාක්ෂණය හරහා ඔබටත් මේ අගනා අවස්ථාව සමඟ අප හා සම්බන්ධ වීමට හැක.

පහත සබැඳිය හරහා ඔබට එදින සාකච්ඡාවට සම්බන්ධ විය හැක.


Meeting ID    : 646 0048 3443
Passcode     : g@VNJ28f 






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Saturday, 16 October 2021

මුහුදු පතුලේ නත්තල් සිරි මවන නත්තල් ගස් පනුවන් (Christmas tree worm)

Spirobranchus giganteus,  යන විද්‍යාත්මක නාමයෙන් හැඳින්වෙන මෙම ආකර්ශනීය ජීවින් නිවර්ථන කලාපීය මුහුදේ වැඩි වශයෙන් දකින්නට පුළුවන්. විශේෂයෙන් කැරබියන් මුහුදේ සිට ඉන්දු පැසිපික් කලාපය දක්වා වූ මුහුදු තීරයේ කොරල් පර ආශ්‍රිතව මොවුන් බහුල වශයෙන් ජීවත් වෙනවා. නත්තල් ගස් පනුවන් සත්ව රාජධානියේ ඇනලීඩා හෙවත් සඛණ්ඩ පනුවන් වංශයේ පොලිකීටා  වර්ගයට අයත් මුහුදේ වාසය කරන ජීව විශේෂයකි. මොවුන්ගේ දේහයේ ඇති නත්තල් ගස් හැඩය නිසා මොවුන් නත්තල් ගස් පනුවන් ( Christmas tree worm) ලෙස හැඳින්වෙනවා. මොවුන් ඉතාමත් අලංකාර වර්ණ වලින් හැඩගැන්වෙන අතර බොහෝවිට එක් සත්වයෙක් වර්ණ දෙකකින් යුක්ත වෙනවා. ඔවුන්ගේ දේහය සෙන්ටිමීටර් 3.8 ක පමණ දිගින් යුක්තවේ. ඔවුන්ගේ නාළාකාර දේහයේ ඇති වී තිබෙන නෙරායාම් මඟින් ඔටුනු ආකාර ව්‍යුහයක් සැකසී ඇති අතර මධ්‍ය දේහය වටා කේශාකාර උපාංග වෘතාකාරව සැකසීමෙන් ඔවුන්ට මෙම සුවිශේෂි නත්තල් ගස් හැඩය ලැබී ඇත. ඔවුන් මෙම උපාංග ශ්වසනය සහ ආහාර ගොඳුරු කරගැනීමට යොදා ගනු ලබයි. මොවුන් පෙරා බුදින්නන් වන අතර ජලයේ පාවෙන ශාක ප්ලාවංග සහ ක්ෂුද්‍ර ශාක කොටස් තම ආහාර වශයෙන් යොදා ගනු ලබනවා.

මොවුන් ඔත් ජීවිත ගත කරන අතර බොහෝවිට ජීව කොරල් වල ශීර්ෂයට සම්බන්ධ වී කැල්සියම් වලින් සමන්විත නාලයක් තම දේහය වටා ස්‍රාවය කරගනු ලබනවා. ඔවුන් එම නාලය තම නිවස ලෙස ආරක්ෂාවට යොදා ගනු ලබනවා. සතුරු ආක්‍රමණයක සේයාවක් දැනුන විගස තම දේහය එම නාළය තුළ සඟවා ගන්නා අතර එසේ සැඟවුණු පසුව නාළයේ විවරයේ ඇති තියුණු අං හැඩැති පිධානය වැසී යාමෙන් ඔවුන්ට තවදුරටත් ආරක්ෂාව සැලසෙනවා.

මෙම ජීවී විශේෂය ඒක ලිංගික වන අතර ජලයට මුදා හරිනු ලබන ඩිම්බ හා ශුක්‍රාණු සංසේචනය වීමෙන් කීටයකු  වර්ධනය වෙනවා. එම කීටයා සුදුසු කොරල්පරයකට සම්බන්ධ වීමෙන් පසු තවදුරටත් වර්ධනය වී සුහුඹුල් අවස්ථාවට පත්වේ.

මොවුන් කොරල් ආශ්‍රිතව මවන්නාවූ වර්ණවත් රූරටා  නිසාවෙන්ම ජලජ ජීවි ඡායාරූපකරුවන් බොහෝ දෙනෙකු මොවුන්ගේ වසස්ථාන තම සේයාරූ ලබාගැනීම සඳහා යොදාගනු ලබනවා.




රචනය - ඉෂිනි දේවින්දි

 මූලාශ්‍ර:

https://www.marinebio.org/species/christmas-tree-worms/spiro

https://oceanservice.noaa.gov/facts/xmas-tree.html

 

 

 



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