Cyclones of Arabian Sea and Bay of Bengal

by Rajshri Ravichandran

One of the most dangerous weather phenomena are tropical cyclones. They are powerful rotating storms with maximum wind speeds reaching 119 kph and torrential rainfall that develop over warm tropical oceans. Furthermore, secondary phenomena like storm surges, flooding, landslides, and tornadoes cause far more harm to people and infrastructure than wind alone. Based on the region of the world they form, several names are given to tropical cyclones. The Atlantic Ocean and the eastern north Pacific Ocean both experience hurricane occurrence. In the western Pacific Ocean, typhoons emerge. The South Pacific Ocean and the Indian Ocean both have tropical storm formations.

Source: Encyclopedia Britannica

More than 90% of the heat produced by greenhouse gas emissions is absorbed by the ocean and which raises the temperature of the waters.

Increasing temperatures contribute to an increase in the frequency of severe storms since cyclones get their power through warm oceans. Severe storms from cyclones might become much more destructive and devastating as a consequence of increasing sea levels. The Arabian Sea had two to three weak cyclones a year on average. Global warming-related increases in ocean temperature are changing that. The Arabian Sea has had pre-monsoon cyclones for four straight years for the very first time since satellite observations began in India in 1980.

Source: The Economic Times

Over the past two decades, cyclones have formed over the Arabian Sea more frequently and with more force than they have across the Bay of Bengal. According to a study, between 2001 and 2019 there was a 52% increase in the number of cyclones across the Arabian Sea and an 8% drop across the Bay of Bengal. Over the last two decades, there have been 150% more extremely strong cyclones in the Arabian Sea. Global warming has caused a sharp rise in surface warming in the Arabian Sea over the past century. The current temperature is 1.2–1.4 °C warmer than it was forty years ago. Active convection, copious rainfall, and powerful cyclones are all supported by these higher temperatures.

Source: The Hindu

The Bay of Bengal has long been a cyclone potential source. Eight of the 10 most destructive tropical cyclones in history have their origins in this area. In accordance with a study on severe weather events, India was affected by up to 117 cyclones in the 50 years between 1970 and 2019 and more than 4 lakh people perished. Three lahks to five lakh persons were massacred when the Great Bhola Cyclone struck the East Pakistani shores (now Bangladesh) on November 11, 1970. The storm’s death toll is the highest known to date. According to the University of Rhode Island, more than 45% of the city of Tazumuddin’s 1,67,000 inhabitants were murdered. The storm surge’s highest height was reported to be close to 35 feet, resulting in significant damage.

Source: Republic World

An IMD report identifies Sundarbans as India’s cyclone capital, and the South 24 Parganas division of West Bengal, which contains the majority of the Indian Sundarbans, as the region greatest commonly affected by cyclones. The triangular form of the bay, which functions as a vortex and generates significant coastal flooding, can also be blamed for the exceptionally high number of cyclone-related deaths in the Bay of Bengal. The low-lying sections of coastal regions frequently flood because the shallow bay bottom provides for more surges.

India has been able to dramatically lower the death toll from cyclones due to timely warnings, the establishment of disaster relief teams, and an improved escape method, among other factors.

Source: Vox

References

What Vegetation can be Found Along the Coast of the Arabian Sea?

The Arabian Sea, often referred to as Sindhu Sagar, is bordered to the west by the Cape of Africa and also the Arabian Peninsula, to the north by Pakistan and Iran, to the east by India, and to the south by the remaining Indian Ocean. The Arabian Sea is bordered by Konkan Coast in central India and the Malabar Coast in south-eastern India.

Source: iStock

The Malabar Coast was a key hub for international trade and commerce for more than 5,000 years with medieval Mesopotamia, Egypt, Greece, Rome, Jerusalem, and the Arab world. Over these millennia, the majority of the region’s natural forests were removed. The Indian Subcontinent’s western coast, from the modern Mumbai city and its 18 million residents all the down to the southern tip of India, was formerly covered in a compact, rich, constant swathe of rain forest, according to a recreation of the ancient forest landscapes.

Source: Wilderness Travel

Tigers, Asian elephants, leopards, and wild canines previously roamed the forests. In the canopy of lofty trees, boisterous populations of big hornbills with oversize yellow bills and massive black and white Malabar pied hornbills would have been competing for fruit. Unfortunately, just a small portion of these trees and its diversity are still present today, victims of human activity somewhere along coast for thousands of years. Largely mostly to the influence of plantation trees like teak or forest degradation, the native tropical evergreen rainforest has been entirely superseded by a semi-deciduous vegetation. Tetrameles, Stereospermum, Ficus, Dysoxylum, Pterocarpus, Terminalia, Dalbergia, Madhuca, and Mangifera species are the distinctive trees.

Source: eBird

The biological ecosystem of the habitat has undergone substantial destruction or transformation to rice paddies, coconut, rubber, and lumber plantations, with virtually any noticeable areas of pristine forest habitat remaining.

Source: Times of India

Konkan is a region rich in natural beauty, but it also has a lot more to offer. Many indigenous and severely threatened species can be found there, from the elusive Indian gaur to the tiny weaver ants; pangolines are treasured there in order to ensure their survival, and Olive Ridley Turtles are protected. Long stretches of spotless, sandy beaches and vibrant seaside communities like Ratnagiri and Ganapatipule can be found along this coastal stretch of land, which is bordered on the east by the Sahyadri hills and on the west by the Arabian Sea. It is rich in natural resources.

Source: World Atlas

This coastal region is home to a variety of plant species, including Rauvolfia serpentine, Curcuma longa, Mucuna pruriens, Anacardium occidentale, Acalypha hispida, Heliconia rostrata, Dioscoria alata, Artocarpus heterophyllus, Michelia champaca, Piper nigrum, Ensete superbum, Dioscoria alata, and horticulture of coconut, mango, cashew nut, areca palm, jackfruit and etc.

Source: india.gov.in

In order to preserve and maintain the blooming biodiversity of cultivation, which is under threat from rising population, changing land use, deforestation, and development activities, the region should be given priority. The diversity, dominance, and richness of the species that make up domestic gardens’ vegetative components vary, indicating their dynamic nature.

References

How does underwater noise affect marine life?

From a scientific perspective, there is little difference between the terms sounds and noise – essentially being pressure waves created by a vibrating object. In common parlance, however, noise translates into something that is not pleasing to the ear and is hence subjective. The frequency (periodic motion of the vibrating object) and intensity (energy carried by the wave per unit area) of sound is measured in terms of Hertz and Decibels respectively. Whether or not a living being can hear a particular sound depends on the frequency range that the being has the ability to perceive.

While the verbal exchange between humans has evolved over time, animals have always used sounds to communicate with each other. Sound is of particular importance to aquatic life – for instance, blue whales are believed to be able to sense sounds from about a thousand miles away and the auditory cortex and cerebellum (the parts of the brain that process sound) in a dolphin brain are rather larger relative to the human average. Marine animals depend significantly on echolocation i.e., they use sound to navigate, communicate, escape predators, find mates and even get food. It is therefore evident that marine animals are impacted by sounds underwater; whether natural or otherwise.

Let’s try to dive deeper into sounds in seas and oceans to understand this better!

The levels of anthropogenic (human-generated) noise have doubled every decade for the past sixty years in some regions. This picture represents the comparative scale of some known noises underwater:

Some of the natural forces causing noise beneath the water’s surface are ice cracking, rains and storms, earthquakes and the like. Anthropogenic underwater noise is usually due to the following:

  1. ship traffic
  2. seismic surveys using airguns
  3. military SONAR exercises
  4. explosives and
  5. construction work

While there are multiple consequences of underwater noise when it comes to the impact on the auditory faculties of marine animals, it is manifested in two forms:

  1. temporary or permanent loss of hearing and
  2. masking of biologically meaningful sounds, such as the predator or mating calls

These are of particular harm to animals such as dolphins and whales that use echolocation for survival. Echolocation involves making a sound and determining what objects are nearby based on echoes – thereby lowering dependence on sight.

Hearing Loss:

Hearing loss in mammals depends on multiple factors, including the hearing sensitivity of the animal in comparison to the intensity, frequency and duration of exposure to the sound.

According to Discovery of Sounds in the Sea, a website curated to synthesise research and other efforts in underwater acoustics, the softest sound that an animal can hear at a specific frequency is called it’s hearing threshold at that frequency. Sounds below this threshold cannot be heard while those above can be, up to a particular combination of intensity and duration beyond which the threshold of hearing may be temporarily or permanently damaged. When this happens, sounds must be louder in order to be detected. If the threshold returns to near normal levels after some a while, this condition is called a Temporary Threshold Shift (TTS) and if it does not, it results in a Permanent Threshold Shift (PTS).

A recent study undertaken by a collaborative research team including scientists from Woods Hole Oceanographic Institution conducted on turtles demonstrates that not only mammals but also reptiles suffer from such hearing loss.

Masking:

Masking occurs when any kind of noise comes in the way of an animal’s ability to perceive a sound and (similar to hearing loss) is influenced by the intensity, frequency and duration of the noise in comparison with the sound of interest. This phenomenon affects animals most significantly when the noise is at frequencies similar to those of biologically important signals, such as mating calls.

Animals respond to masking noise in one of the following three ways:

  1. stopping vocalisations
  2. increasing the intensity of their vocalisations (Lombard Effect)
  3. changing the frequency of their vocalisations

A good example of these responses would be the study of the effects of noise on the vocal behaviour of beluga whales inhabiting the St. Lawrence River Estuary in Canada.

This region is a significant route for commercial shipping as well as a popular spot for whale watching. The belugas were exposed to noise from a small motorboat and a ferry and were noted to have reduced their calling rate as the boats neared and increased the repetition of certain calls when boats came within a distance of 1 kilometre.

Other consequences of underwater noises include:

  1. stranding – a phenomenon where whales, dolphins, and porpoises (cetaceans) are found dead, either on the beach or floating in the water, or alive on the beach and unable to return to the water and
  2. avoidance behaviour, which can lead to the abandonment of habitat or migratory pathways and disruption of mating, feeding, or nursing

All of the above are likely to alter relationships between species by changing who can effectively catch food, find a mate or hide from predators which is a cause for concern. While mankind has come too far ahead to be able to do without some of the activities that cause noise underwater, we can certainly take steps to regulate the noise generated. To encourage the reduction of the negative effects of underwater radiated noise on marine species, in 2014, the International Maritime Organization (IMO) published Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life. The IMO is the United Nations specialised agency responsible for the safety and security of shipping and the prevention of marine and atmospheric pollution by ships.

Hopefully, over the next sixty years, human-generated noises do not double every decade!

Under the Sea: The Immortal Jellyfish

Do you ever wish you could go back in time to when you were smaller and had absolutely no responsibilities? What would happen if you could hit the reset button every time adult life got a little too stressful? You could potentially live forever!

While humans are yet to figure out how to achieve immortality, here is a tiny jellyfish, only half the width of your thumbnail, that seems to do just that –

Turritopsis dohrnii is a hydrozoan that was first discovered accidentally, by two students – Sommer and Bavestrello in a laboratory. They had collected the specimen, mistaking it for another species (Turritopsis nutricula), and forgot about it in the rearing jar. The next time they checked it, they found a large number of newly settled polyps to be suspicious. Upon further study, they found that under stressful conditions, the mature medusa transforms back to their polyp stage. Initially observed in the Mediterranean sea, they are hitchhikers using ships ballast water, and other marine vessels and can be found in almost all parts of the world. In common jellyfish, the fertilized egg develops into a planula, which then transforms into a polyp that expels more medusae.

But in the case of the immortal jellyfish, when exposed to physical stress factors like starvation, reduction of salinity, temperature changes, and damage from forceps, the medusae curl back into their polyp over a span of 1-2 weeks. It can be compared in simpler terms, to a butterfly turning back into a caterpillar upon maturity. This discovery was revolutionary and initially termed impossible because of the sheer miraculousness of it all!

When the world first heard about this around 20 years ago, the media went into a frenzy because of its revolutionary nature. This process termed ‘cellular transdifferentiation’ may not be our answer to never-ending life but it may certainly help us live a little longer. We could understand better how to repair or regenerate damaged tissues and this in turn may cure diseases like Parkinson’s and cancer. This discovery could potentially change the fields of science and medicine and turn about the very way our lives function!

Source: http://www.science.org.au

The pioneers of this field may be Sommer and Bavestrello but Dr. Shin Kubota in Kyoto University, Japan is a revolutionary in this field with studies that show the animal can go back to its polyp stage almost 10 times over a span of 2 years. Dr. Kubota is so passionate about this animal because he believes they can hold the secrets of human life and perhaps even immortality. He holds the only captive population in the world and spends his mornings catching plankton for them while caring for and studying them the rest of the day. But because he is not so sure that humankind can handle the responsibility of such a precious dream, by night he himself transforms into a popular TV persona, donning a jellyfish cap and a lab coat, who writes and performs songs on this jellyfish to encourage man to live at peace with nature and value it – christening him “The Immortal Jellyfish Man”. One of his many dreams was to travel the seas of the world on a cruise ship, stopping at different points to collect specimens of marine life and at night, to go perform his awareness-creating songs at the karaoke.

There is a possibility of there being other creatures on this planet that hold the secret to living forever but so far, the immortal jellyfish is the only one close to it. There is, however, the obstacle to their survival in captivity. These jellyfish don’t usually thrive under laboratory conditions and as a result, it is difficult to rear and study them. But limiting research to only those creatures that are easy to culture causes us to lose out on those that could hold many revolutionary secrets in the field of science.

While we don’t fully know yet the molecular mechanism by which these creatures are able to completely reset their cells, there is reason to hope for a future where we may be able to live forever. But whether that is a good thing or not, is a whole other dilemma.

Think About It-

  • Why do jellyfish have tentacles?
  • Do jellyfish have a brain?
  • What should we do if we are stung by jellyfish?
  • What do jellyfish eat?
  • Are there any jellyfish at your local beach?

What does Dugongs’ extinction in China mean for its relatives in India? 

Dugongs, vegetarian marine mammals are now officially extinct in the Chinese waters. This piece explores the significance of its existence and extinction and what does this mean to the endangered species’ relatives in India’s Palk Strait?

Dugongs, popularly known as ‘Sea Cows,’ are the only surviving species of aquatic herbivores that belong to the order Sirenia of the Dugongidae family. Unfortunately, they are highly vulnerable to extinction and one among the critically endangered species of the International Union for Conservation of Nature (IUCN). They are positioned on the IUCN’s Red List of threatened species and are hunted to extinction for their precious meat and oil. But why are we discussing dugongs now? That is because these benthic seagrass creatures are officially declared functionally extinct on the Chinese coastline after a recent study in August 2022.

The dugong population in China has been reducing rapidly since the 1970s, primarily due to human-caused problems that led to habitat loss of the species. Besides, the study highlights some major reasons for dugong extinction in the region: overfishing and ship strikes. To understand the dugong population in the region, about 800 fishermen reportedly scattered across the South China Sea were interviewed. Of which only three respondents answered they had sighted dugongs over the last five years at the site. Another substantial piece of evidence that proves dugong’s extinction is the absence of any official field observation record of dugong sightings after 2000. The reason behind dugong extinction is that the area receives massive stress from the fishing industry for housing some of the rarest and the most spectacular marine biodiversity in the world. Hence, these marine species are hunted for their delicious meat. Another important reason for dugong extinction is bottom trawling, one of the most prominent fishing methods in today’s era. This destructive method uses a large net with a wide mouth and a small closure to catch a large quantity of fish. As bottom trawling is indiscriminate with its catches, it destroys the seabeds uprooting innumerable plants, thus, sweeping off natural habitats of dozens of aquatic animals in these nets.

Image 1: A representative image of a dugong Pic: 2g601hto8u_Medium_WW1221.jpg

Nevertheless, what does this mean to the remaining dugongs on India’s coastlines? India is a country known for its rich biodiversity. Since 1983, India has been a non-legal MoU signatory of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) for various species such as Sea turtles, Dugongs, Raptors, and Siberian Cranes. According to the Wildlife Institution of India, there are about 200-250 dugongs in Indian waters, of which 75 are found in Andamans and 150 in the Palk Bay in the Gulf of Mannar. Therefore, in 2021, the Tamil Nadu government initiated the idea of establishing India’s first Dugong conservation reserve in the Gulf of Mannar in the Palk Strait Bay. Consequently, the state government allocated an area ranging around 500 sq. km in the Palk Bay and the Gulf of Mannar biosphere reserve to protect the fragile and stunning biodiversity of the region. In addition, the area houses some rare fishes, sea turtles, and seahorses. The reserve stretches from Adirampattinam in Thanjavur district to Amapattinam, a coastal neighbourhood in Pudukottai district.

But why are Dugongs significant to the marine ecosystem? Dugongs play a crucial role in balancing marine ecosystems. Since these vegetarian marine mammals feed on underwater seagrass, their repeated action promotes the regrowth of plant species. The availability of seagrass will also affect the existence of other sea creatures, such as dolphins, turtles, etc., which also depend on seagrass as a primary food source. Thus, the extinction of dugongs from Chinese waters is an alarming indication to speed up conservation efforts. India’s first dugong conservation reserve in the Gulf of Mannar is a stepping stone in the path of effectively planned conservation.

References

Chaitanya, K. S. V. (2021, September 4). India’s 1st dugong conservation reserve to be in Tamil Nadu. . . The New Indian Express. https://www.newindianexpress.com/states/tamil-nadu/2021/sep/04/indias-1st-dugong-conservation-reserve-to-be-in-tn-2354056.html

Shaji, K. A. (2022, January 16). India’s first dugong reserve will help protect the world’s only herbivorous marine mammal. Scroll.In. https://scroll.in/article/1014882/indias-first-dugong-reserve-will-help-protect-the-worlds-only-herbivorous-marine-mammal

Ives, M. (2022, August 27). The Dugong ‘Sea Cow’ Has Vanished from China’s Waters, Study Says. The New York Times. https://www.nytimes.com/2022/08/26/science/china-dugong-sea-cow-extinct.html

Tidal Energy: A Boon or Bane?

As the demand for clean energy is increasing by the day, various entities are eyeing the renewables. Though wind and solar are already on the run, the race for tidal energy is yet to begin.

Powered by the kinetic energy from the natural rise and fall of ocean currents and tides, tidal energy is a renewable source of energy that is primarily used to generate electricity. It is caused by the gravitational attraction between earth, moon, and sun, thus producing tidal forces. As the earth rotates, these forces correspond to the movements leading to a changing ocean currents’ motion. As a result, tides are stable and predictable and can produce a steady stream of electricity. Therefore, owing to its infinite capacity, it is often considered an inexhaustible renewable energy source for the future.

Image 1: A representative of tidal stream generators. Pic: tidal-energy.jpg

But tidal energy extraction gained momentum only in the early 20th century. In the early 1920s, US and Canada conducted many state-sponsored studies to understand the tidal force’s potential to replace non-renewable energy resources and the developmental costs for the same. Despite being widely accepted as a potential renewable energy source, the amount of power produced from tidal force has been minimal. Even today, there are very few commercial tidal power plants operating worldwide. As tidal energy is relatively new, there are no multiple power-generating techniques to extract tidal energy; nevertheless, there is a prominent use of special energy generators to convert tidal force into electricity. Currently, there are three known methods of tidal energy generation. These include Tidal Turbines, Tidal Barrage, and Tidal Lagoon.

Turbine: A turbine takes energy from flowing fluid; this fluid could be wind or water. A wind turbine converts kinetic energy into electrical energy to generate power from a windmill. Similarly, as tides are fast-flowing waves of water, turbines are placed to capture the kinetic energy of the moving water. As tides are denser than winds, tidal energy produced is more powerful than wind energy. While turbines can operate at any depth, it is best to position them in shallow water. Tidal stream generators use breeze turbines placed in clusters under the water to generate power from underwater currents. Besides, stream generators also include float turbines. These turbines are anchored to the seafloor using cables, and energy is produced from the turbines that rotate due to the water stream movement. As tidal turbine blades are slow in their motion, it is less likely to affect marine biodiversity. However, local conditions and the turbine size are significant in determining the impact of tidal generators. In addition, turbines are large and disrupt the motion of tides and currents; therefore, it becomes difficult for the machines to capture and harness the energy.

Barrage: Barrages are dam-like structures built across rivers or ocean bays for generating power using potential energy. The turbines inside the barrage take advantage of the differences between the high and low tides. Water from the high tide is released through the turbine, generating electricity. The water level changes in the area surrounding a barrage, which changes the water salinity of the region around the barrage. These changing ecosystem conditions might harm the organisms that live in the water body. In the case of a barrage, a cluster of turbines is placed horizontally; with the fast movement of the blades, there is a high likelihood of marine life getting caught in the quick action resulting in injury or loss of life. Consequently, the sea birds in the region whose primary feed is based on fish may migrate as their food source is limited.

Image 2: A representative image of a tidal barrage. Pic: tidal-power-plant.jpg

Tidal Lagoon: Lagoons are large water structures created by reservoirs similar to tidal barrages and seem like separate bodies of water away from the tides. Lagoons are usually constructed alongside natural coastlines. They appear like a seawall at low tides, submerged at high tides, and are enclosed by a human-made or natural barrier. Accelerating turbines attached to the sea walls generate power from the tidal streams. Lagoon power generation involves extracting electricity from the tide when it comes in and goes out. Though the energy produced from a lagoon is considered more eco-friendly than that produced in a barrage, they are less environmentally damaging. This is because lagoons are smaller in size, and due to their size, small fishes thrive in a lagoon, which may attract birds that prey on marine life.

Regardless of the methods and technologies, why is tidal energy still at the start point in the run for renewability and sustainability while wind, solar and nuclear are on their paths to accomplishing their mark? Despite being a clean energy source, why is tidal energy not as popular as the others? Why are only a few industrial units producing tidal energy on a broader scale? It is crucial to find answers to these questions to understand the potential for the large-scale production of this alternative form of energy. Though it is not enough to suffice everyone’s energy demands, it plays a key role in reducing our reliance on fossil fuels and non-renewable energy sources. These projects can be horrific to local communities such as coastal communities involved in marine livelihoods in cases of community displacement. Hence, numerous studies have been conducted to understand the socio-ecological impact of tidal energy.

Most studies show that the environmental consequences are site-specific based on local geography and ecology. Tidal range projects like the barrages are enormous stress on the local environment; these projects alter the water levels, reducing the population of migratory fish in the ecosystem. These projects are located in sites with high tides that generate energy based on high and low tide differences, such as in Canada, South Korea, Russia, China, New Zealand, etc. Furthermore, electricity is generated when the temporarily stored tidal water flows through the turbines, which on fast movement, have the potential to injure or kill marine plants and animals, thereby affecting the bird population that depends on these sea creatures as a source of food. Additionally, as tidal energy equipment is often placed near the shore, there is a possibility that the electromagnetic fields and acoustics may affect marine organizations in the region. Moreover, as these equipment are placed offshore, the soil around the region is also disturbed. Developments in tidal energies are still in their beginning phase; hence, the disposal process of used/old equipment and technologies utilized in energy extraction is not widely discussed. However, newer technologies are being introduced to balance out these negative implications.

One of the reasons why tidal energy is not very prominent is that it is not cost-effective during the initial stages of establishment. Especially, tidal barrages are costlier than the other methods owing to the money involved in constructing dams/reservoirs. Therefore, tidal energy is more expensive than other renewable energies, yet the net energy produced from tides is minimal. Another reason is that the research and developments in the field are still in their infancy stage, so investing in the resource does not guarantee a return. Therefore, given the financial constraints, only developed countries in the Global North are developing tidal energy projects.

These claims show that the current possibilities for full-fledged use of tidal energy resources are pretty bleak. Thus, in conclusion, the takers for tidal energy are divided.

References

National Geographic. (n.d.). tidal energy | National Geographic Society. https://education.nationalgeographic.org/resource/tidal-energy/

The potential of tidal energy production. (2015, August 30). GreenFacts. https://www.greenfacts.org/en/tidal-energy/index.htm#1

Into the Depths of the Indian Ocean

The Indian ocean being the world’s third biggest ocean covering 7,05,60,000 sq km which is 19.5% of Earth’s water surface and 19.8% of the global ocean volume is the least understood ocean among the 5 oceans with complex geomorphology. The Indian ocean has subduction trenches, seamounts, ridges, plateaus, coral atolls, fracture zones and hydrothermal vents but is scientifically neglected for years.

The Java trench is the deepest subduction trench in the Indian ocean and also the only trench which exceeds the hadal zone (more than 6000m water depth). Java trench is also called Sunda trench which is 2000m long and 7290m deep. As a part of the Pacific ring of fire, the Java trench starts from the Lesser Sunda Islands past Java, around the southern coast of Sumatra on to the Andaman Islands, and forms the boundary between Indo-Australian Plate and Eurasian plate.

The study on Java trench is recent and because of its depth this trench has an isolated geographical hadal ecosystem. It has a temperature of 1.54°C with fine grained sediment plateaus. The Java trench has 10 phyla, 21 classes, 34 orders and 55 families. There are 36 chemosynthetic bacteria mat deposits of orange, yellow, and white in color. The trench is populated by hexactinellid sponges. Holothurians like Amperima cf. naresi, Elpidia cf. sundensis, Enypniastes sp., Psychropotes sp., Elpidia cf. sundensis, Munnopsid isopod. Actiniarias like Galatheanthemum and Bathyphellia, Snailfish, Echinoderms like the asteroid Hymenaster sp., unidentified Ophiuroid sp., fragile, semi-transparent Crinoids, unidentified crinoid, and unidentified Ophiuroid sp., the polynoid polychaete, Macellicephaloides. Amphipods like the supergiant Alicella gigantea, Bathycallisoma schellenbergi, the unidentified Stegocephalidae species, and the pardaliscid Princaxelia, the Mysid Amblyops sp., the stalked ascidian, Culeolus sp, echinoderms like ophiuroids or brittle stars (Ophiuroidea), asteroids or sea stars (Asteroidea), and crinoids or feather stars (Crinoidea), 98 unidentified ophiuroids (Ophiuroid sp. 1), Anemone Galatheanthemum, Anemone Bathyphellia, Polynoidae Macellicephaloides, mysid Amblyops sp., Alicella gigantea, Princaxelia, Bathycallisoma schellenbergi, Stegocephalidae sp,. Grimpoteuthis sp., larvaceans, 7 Ophidiidae species, 1 Ateleopodidae species and 1 liparid species are discovered in the deepest point of the Indian ocean. The Java trench is still highly unexplored and has undiscovered and undescribed life forms.

Inside the least studied ocean within the least explored trench with many unidentified species, plastic and man made metal items were found proving that there is no “pristine” wilderness left neither on land nor in the deep oceans.

References:
https://www.frontiersin.org/articles/10.3389/fmars.2022.856992/full?&utm_source=Email_to_aut
hors_&utm_medium=Email&utm_content=T1_11.5e1_author&utm_campaign=Email_publication
&field=&journalName=Frontiers_in_Marine_Science&id=856992
https://en.wikipedia.org/wiki/Sunda_Trench
https://www.britannica.com/place/Java-Trench

Kerguelen Plateau and Its Implications for Climate Change

The Kerguelen Plateau is located in the Indian Ocean, and is the longest continually erupting supervolcano. From 90 to 120 million years ago, basaltic lava eruptions from fissures on the seabed led to the formation of a volcanic plateau that eventually rose above the sea level. The presence of soil layers and charcoal from previous vegetation in the basalt indicates that the Kerguelen Plateau was once above sea level. Due to the volcanic rock sinking slowly, the Kerguelen Plateau is currently oceanic, 1000-2000m below the sea level. The Kerguelen Islands, (French territory) and the Heard and McDonald Islands (Australian territory), are the only parts of the plateau that remain above the sea level (Bressan, 2020).

The Kerguelen Plateau is classified as a Large Igneous Province (LIP). LIPs are formed as a result of massive volcanic events. They are formed due to the accumulation of basalt and volcanic rocks. LIPs can form on existing continents, in the ocean or at tectonic plate boundaries (Coffin, 1994). The Kerguelen Plateau has an area of 1250000 sq km. To put things in perspective, its area can be compared to half the size of the Australian continent.

Location

The plateau is situated in the temperate zone of the Southern Hemisphere. It is a part of the sub-Antarctic shelf (Barnes et al., 2018). On the map, it can be found between Africa and Australia, towards the south of both continents.

Why is there volcanic activity even today?

The unique geological features of Kerguelen Plateau make it conducive for volcanic activity. The edges of three large tectonic plates are found in the Indian ocean – the African, the Antarctic and the Australian plates. The Kerguelen Plateau was initially located in between the Antarctic and Australian plates, which was a hot-spot of volcanic activity. This provided the heat needed to melt the rocks and the magma spread along the ridge between the tectonic plates. The magma cooled and solidified to form the plateau.

The Kerguelen Plateau drifted towards the south across millions of years, moving away from the volcanic hotspot. Thus, though it is still volcanically active due to its location, the frequency of these eruptions has decreased (Bressan, 2020).

Kerguelen ecosystem

The ecosystem comprising the plateau, Kerguelen islands and the Heard and McDonald Islands are isolated from the mainstream human settlements. The plateau is home to rich biodiversity. It supports the growth of these species as the mineral content from the volcanic eruptions make the region nutritious.

The plateau is home to a rare and expensive variety of fish called the Patagonian toothfish. It is also called the Chilean seabass, sold in the market at high prices. The white flesh of these fish is considered as a delicacy and is said to be healthy. The toothfish populations are vulnerable to unsustainable fishing and illegal poaching (Dell, 2019).

Since the toothfish is a top predator, it has ecological importance in balancing the population of other marine species it feeds on, maintaining the food chain and structure of the ecological community.

The banks of the plateau are inhabited by coral species, crustaceans, sponges and anemones. They are slow growing communities, and ecologically sensitive to anthropogenic disturbances.

The plateau intercepts the strong water currents around the south pole. There is an upwelling of cold water from the depths of the sea with volcanic minerals to the surface, which again returns to the bottom. This nutrient transport supports diverse marine life and a food cycle from zooplankton to penguins, albatross, elephant seals and sperm whales. The seabed supports invertebrates and fish species that are only present due to the nutrients from the plateau (Dell, 2019). 

Implication for climate change

Ocean currents from the tropical deep-sea carry nutrients towards the Arctic and Antarctic regions. There are no primary producers at the poles because phytoplankton (consumed by small organisms which are then consumed by the predators) do not survive in the frigid temperatures. So, the nutrients are transported back to the tropical regions by the currents.

In the case of global warming, the poles receive more sunlight because of the melting glaciers. The warming conditions allow for phytoplankton to grow. Therefore, the polar regions and the surrounding oceanic environment will utilize more nutrients and support marine species that migrate to cooler, polar waters.

The location of the Kerguelen Plateau close to the south pole makes it important for scientists to understand the pole-ward shift of marine organisms due to climate change (Dell, 2019). The plateau is being studied to understand how this change will impact oceanic ecosystems near the equator and vulnerable species.

Blue carbon sequestration

Blue carbon sequestration refers to the carbon removed from the atmosphere and stored in coastal and marine ecosystems.

Snowmelt in the polar region results in increased phytoplankton bloom due to the sudden increase in sunlight and heat. This increases the carbon sequestration abilities of the region, which is negative feedback on climate change (i.e., slows the rate of global warming by capturing atmospheric carbon near the poles) (Barnes et al. 2018).

Research shows that the Kerguelen Plateau has potential for blue carbon sequestration in the future while supporting marine biodiversity. There was an increase in organisms at the Kerguelen region across the past decade, suggesting that carbon storage would have also increased (Bax et al., n.d).

Conclusion

Oceans are carbon sinks – dead marine organisms are decomposed and the carbon is sequestered at the seabed. Phytoplankton at the surface of the water uptake carbon for their growth.

The Kerguelen Plateau’s features and location could help provide a better understanding of marine ecology and the changes caused by climate change. There is still a lot of research left to do, and is being undertaken by various international organizations.

The Kerguelen Plateau and its islands are a fragile ecosystem. Since it is isolated from human activity, it is also important from the aspect of biodiversity conservation.

References

Barnes, D., Fleming, A., Sands, C., Quartino, M., & Deregibus, D. (2018). Icebergs, sea ice, blue carbon and Antarctic climate feedbacks. Philosophical Transactions Of The Royal Society A: Mathematical, Physical And Engineering Sciences, 376(2122), 20170176. https://doi.org/10.1098/rsta.2017.0176

Bax, N et al. Carbon storage by Kerguelen zoobenthos as a negative feedback on climate change. The Kerguelen Plateau: Marine Ecosystem + Fisheries Proceedings of the Second Symposium. Retrieved 13 June 2022, from http://heardisland.antarctica.gov.au/__data/assets/pdf_file/0019/229141/18-Bax-EA.pdf.

Bressan, D. (2020). Kerguelen Plateau Is Earth’s Longest Continuously Erupting Supervolcano. Forbes. Retrieved 13 June 2022, from https://www.forbes.com/sites/davidbressan/2020/11/06/kerguelen-plateau-is-earths-longest-continuously-erupting-supervolcano/?sh=118a0ba032c8.

Coffin, M. (1994). Large Igneous Provinces. Retrieved 13 June 2022, from https://www.ldeo.columbia.edu/~polsen/nbcp/lipmc.html.

Dell, J. (2019). Australia’s only active volcanoes and a very expensive fish: the secrets of the Kerguelen Plateau. The Conversation. Retrieved 13 June 2022, from https://theconversation.com/australias-only-active-volcanoes-and-a-very-expensive-fish-the-secrets-of-the-kerguelen-plateau-123351.

The End of Fish?

They are one of the original species that inhabited the earth. They are the main source of protein for 3 billion people. They affect the livelihoods for 600 million people. They play an important role in nutrient cycles that sustain aquatic ecosystems. They are an obstacle against climate change by partaking in carbon sequestration. They are essential contributor to life on Earth. They are on the path to extinction.

Plastic: Nylon fishing nets are an efficient and predominant tool of the trade but also account for roughly 10 percent of the plastic debris. Every year 500,00 to 1,000,000 tons of plastic from fishing gear are discarded into oceans. They harm the underwater ecology in a variety of ways the two most notorious being: the degradation of microplastics and the entanglement of wildlife. The microplastic formation can arise either through discarded fishing gear or simply through prolonged and repetitive use of the gear. The entablement of wildlife happens simply by carelessly or purposefully discarding nets, lines, or ropes into the sea, and the sheer amount discarded causes harm through strangulation, cutting into flesh and muscles severing arteries, and trapping animals underwater that need to surface for air, to a wide variety of marine life ranging from fish to whales.

Overfishing: Catching fish provide a rich source of protein and economic opportunities to a large portion of the human population, so isn’t inherently bad as long as enough time and numbers are present to allow for the species to replenish, this is where the problem of overfishing comes from. Through the advancement in fishing technologies, increasing demand, and illegal fishing, fish and other forms of edible marine life are being caught at an alarming rate. How does this affect the ocean? By significantly affecting the population of one species it creates a domino effect that alters the existence of other species in that food web along with an increase in the growth of algae and a decline in the health of coral, thereby damaging the ocean’s biodiversity for a prolonged period.

Along with the countless targeted fish, other unwanted species and sometimes endangered ones can be thrown back into their habitat unharmed but are at times discarded dead due to a lack of concern on the fishermen’s part, resulting in unneeded causalities along with ones that are overfished. How does this affect people? The fishing industry worldwide currently offers jobs for around 60 million people and supplies the demand for close to 3 billion people. When the species of fish disappear so do the jobs they offer, this is significantly detrimental to developing coastal communities, who do far less damage to marine life than their commercial counterparts due to their small scale, but the overexploitation by the latter will render the former obsolete and will, in turn, affect the protein intake from fish in these communities.

Climate change is another by-product brought about by overfishing that has a circular effect on the fishing industry. Climate change brings about sudden rises in temperatures and acidification of the ocean’s water leading to the degradation of marine habitats and loss of species and in turn overfishing leading to less fish which leads to less carbon sequestration.

Damaging fishing methods: While with regulations, methods such as purse seine, trawling, gillnet, longlines, etc., that are generally associated with overfishing can be eco-friendly, there are some methods practiced that no matter what regulations are made will lead to irreversible damage. Blast fishing, dynamite, or homemade bombs are used to indiscriminately kill a large number of fish and bring about the destruction of the physical environment notably coral reefs. Bottom trawling involves towing a net at the very bottom of the ocean to capture bottom-dwelling fish such as shrimp, cod, squid, and rockfish, as this process is carried out damage is inflicted on the seabed communities. Cyanide fishing is a method used to catch live fish for aquariums, a sodium cyanide mixture is sprayed onto the fish habitat to stum them, there are two adverse effects from this method, one being what the previous two methods lead to which the damage of the targeted fish’s habitat, the other being the mortality rate of the fish within 48hrs of capture is 75 % so in other to compensate this loss is an extra amount of fish are targeted.

According to an article published in 2006 and by the recent Seaspiracy documentary, the oceans are predicated to be empty of fish by 2048, although this date has been disputed by various experts, the underlying concern it carries is still relevant and steps need to be taken to counter the above mentioned sources and various others in order to alleviate us from the possible future.

Sustainability of Seafood

Seafood is a common source of protein and ensures food security in many coastal regions across the world. The seafood industry also has economic importance- serving consumers and exporting delicacies and popular varieties of fish, crab, shellfish, etc. However, overfishing and certain aquaculture practices have raised environmental concerns.

Is seafood sustainable?  Does the seafood industry cause environmental problems? And is seafood better than other types of meat? These are some questions that will be answered subsequently.

Aquaculture is the process of cultivating aquatic life for our consumption. This happens in natural marine habitats or in controlled environments that replicate marine habitats. There are many stages in aquaculture. The first stage is the hatchery (collecting eggs, breeding of fish). The fish are then transferred to the farm where they are grown to their full size. Then they are harvested, processed, packaged and transported to stores and markets (Global Seafood Alliance, 2019).

Environmental impacts of aquaculture

Certain species like salmon consume wild fish as their food. So, it takes more than one kilogram of wild fish to produce one kilogram of salmon (Greenberg, 2014). This leads to overfishing to meet the dietary needs of the species being cultivated.

Aquaculture also generates waste through fecal matter and unused feed. The waste is nitrogen-rich and causes oxygen depletion if they are discarded in marine environments. This would choke aquatic organisms in the ocean. The use of pesticides and antibiotics in aquaculture produces chemical waste that pollutes ocean water.

Shrimp farming mostly occurs in tropical and subtropical ponds, within mangrove forests. When pollutants accumulate in shrimp farming ponds, the ponds are abandoned and cultivation is continued in a new pond. This results in the destruction of mangroves, which also host other species of fish and offer coastal protection against cyclones. Therefore, organic aquaculture has started gaining importance, to protect mangroves and sustain people’s livelihood (Greenberg, 2014).

The fishing industry also removes reproductively mature fish from their natural environment, which leads to population decline of fish. Overfishing can slow down the growth of fish population and disrupt the marine food chain. It threatens the livelihood of small fishermen who depend on the daily catch for food and income (Pariona, 2017).

Harmful fishing techniques

These are two ecologically damaging fishing techniques, that are now being banned by many countries due to the problems they cause.

  1. Bottom trawling – Fishermen drag a net along the seabed. This disturbs the sediments that had settled at the bottom. The sediments are carried to other parts of the ocean by the currents.  Accumulation of sediment creates murky water, which blocks the sunlight from reaching underwater plants, creating oxygen-deficient regions. Pollutants that had settled at the seabed are stirred up and enter the food chain, poisoning marine life.
  2. Blast fishing – Explosives are used to kill large numbers of fish at once. This destroys coral reefs and causes oceanic noise pollution (Greenberg, 2014).

Waste generated by aquaculture

Fodder waste and chemical pollutants not only pollute the local ocean water, but can be transported throughout the ocean, affecting different levels of the food chain. It could affect the growth of plankton, and subsequently reduce biodiversity.

Aquaculture waste, once treated, has many uses and economic potential. Fodder waste can be converted to biogas or as fertilizers for soil.

Chitin, obtained from the exoskeleton of crustaceans (crabs, lobsters, shrimp), is used as an additive in fish food. Chitin also has other applications in the medical field.

The process of obtaining chitin also recovers carotenoids. Shrimp waste has economic potential due to the presence of carotenoids. Carotenoids are responsible for the color in shrimp and shellfish. Once extracted and processed, they are used in the food industry and the cosmetic industry.

Compounds like enzymes and proteins could be used in the pharmaceutical industry, and the methods to extract these from seafood waste are being researched (Arvanitoyannis & Kassaveti, 2008).

Seafood production and climate change

The rising temperature of ocean waters due to global warming has reduced fish productivity and changed the distribution of fish population. This hurts seafood production, especially in the tropical countries who are most dependent on seafood for food and money.

Warmer water increases the risk of algal blooms, which will hamper aquaculture. Aquaculture farms will shift their location depending on the condition of the water and marine productivity (Palardy, 2022).

Yet, seafood has the potential to become one of the most sustainable ways of achieving food security for the future.

Seafood can be sustainable

Currently, the seafood industry is criticized for causing overfishing, water pollution and marine degradation. In spite of these environmental impacts, it has the potential to become sustainable if managed efficiently, with proper waste recycling and treatment, and policy measures to ban hazardous fishing methods and overfishing.

Seafood has higher protein retention compared to other types of meat like pork, chicken and beef. Aquaculture is more resource efficient; it has lower greenhouse gas emissions, water demand and land requirement than land-based meat production (Greenberg, 2014).

Some varieties of seafood have lower environmental impact than other varieties. For example, farmed shellfish, mollusks, sardines, mackerel and herring have low environmental impact compared to catfish aquaculture and shrimp. This is because more energy is used for water circulation in the latter.

Mollusk aquaculture (oysters, mussels, scallops) has a positive impact on marine environment because mollusks absorb excess nutrients from water, that would otherwise harm the ecosystem. Capture fisheries do not use fertilizers and thus generate less pollution compared to intensive fish farming (Ma, 2018).

Therefore, consumers also play an important role in the sustainability of seafood by choosing species that have low environmental impact for cultivation and sourcing their seafood from fisheries that follow sustainable practices.

References

Arvanitoyannis, I., & Kassaveti, A. (2008). Fish industry waste: treatments, environmental impacts, current and potential uses. International Journal Of Food Science &Amp; Technology43(4), 726-745. https://doi.org/10.1111/j.1365-2621.2006.01513.x

Greenberg, P. (2014). Environmental Problems of Aquaculture. Earth Journalism Network. Retrieved 17 June 2022, from https://earthjournalism.net/resources/environmental-problems-of-aquaculture.

Ma, M. (2018). Choice matters: The environmental costs of producing meat, seafood. UW News. Retrieved 17 June 2022, from https://www.washington.edu/news/2018/06/11/choice-matters-the-environmental-costs-of-producing-meat-seafood/.

Palardy, J. (2022). Seafood Production Suffers Under Climate Change, but Sustainable Reforms Can Help Maintain Harvests. Pew. Retrieved 17 June 2022, from https://www.pewtrusts.org/en/research-and-analysis/articles/2022/05/11/seafood-production-suffers-under-climate-change-but-sustainable-reforms-can-help-maintain-harvests.

Pariona, A. (2017). What Is The Environmental Impact Of The Fishing Industry?. WorldAtlas. Retrieved 17 June 2022, from https://www.worldatlas.com/articles/what-is-the-environmental-impact-of-the-fishing-industry.html.

What is Aquaculture, and Why Do We Need It?. Global Seafood Alliance. (2019). Retrieved 17 June 2022, from https://www.globalseafood.org/blog/what-is-aquaculture-why-do-we-need-it/.