Warming of the Indian Ocean and its Impact on Rainfall

The Indian Ocean is extremely important in modulating and regulating the climatic conditions over its rim countries. Many oceanic and atmospheric processes play a vital role in influencing rainfall, drought, cyclones, and other weather patterns, hence supporting diverse ecosystems as well as shaping the agricultural sectors in these countries.

However, with the increases in sea surface temperatures (SST), as a result of climate change and global warming, in the Indian Ocean, these crucial oceanic and atmospheric dynamics are shifting, with unprecedented and devastating effects on the surrounding communities. In fact, “sea surface temperatures in the Indian Ocean have warmed by approximately 1°C since 1950, among the fastest rate of increase in the global oceans” (Wenegrat et al.).

These changes in the temperature of the ocean are having a profound impact on weather patterns worldwide. For instance, in the Indian subcontinent, the cyclone season is becoming more intense as a result of warming ocean temperatures. “A 2016 Nature study found anthropogenic global heating had contributed to the increased frequency of extremely severe cyclonic storms over the Arabian Sea” (Vallangi). India is particularly vulnerable to these intense storms, especially considering that 14% of the entire population lives in coastal areas and will most likely be heavily affected by storms of increased intensity and frequency.

Although this warming trend seems to increase rainfall and storms over the Indian Ocean and in India’s coastal regions, the South Asian monsoon, also referred to as the Indian Summer Monsoon, might weaken over land. It is important to note, however, that although the overall monsoon season is weakening, instances of heavy rains during the season seize. The fluctuation of wind patterns that are caused by global warming will most likely result in short spurts of heavy rainfall amidst a vast dry period with minimal rainfall. These changes in rainfall patterns over South Asia “is a matter of grave concern since the socio-economic livelihood in this region, including agriculture, water resources, and power generation are irrevocably dependent on it” (Jayaraman).

The warming of the Indian Ocean is forecasted to have devastating impacts on the agricultural industry in India, as well as the coastal communities of the country. Considering the above information and evidence, it is of crucial importance to clearly understand the regional impacts of a weakening monsoon season and the onset of longer, more intense storms in order to devise appropriate responses.

Works Cited

Jayaraman, K. S. “Warming Indian Ocean weakens monsoon.” Nature India, 17 June 2015, https://www.nature.com/articles/nindia.2015.81. Accessed 5 May 2023.

Padma, T. V. “Higher Sea Surface Temperatures Could Lead to a Weaker Monsoon.” Eos, 6 April 2022,

https://eos.org/articles/higher-sea-surface-temperatures-could-lead-to-a-weaker- monsoon. Accessed 5 May 2023.

Perinchery, Aathira. “Climate Change is Altering the Dynamics of the Indian Ocean in Enormous Ways.” The Wire, 8 March 2022,


dian-ocean. Accessed 5 May 2023.

Vallangi, Neelima. “Rapid heating of Indian Ocean worsening cyclones, say scientists.” The Guardian, 27 May 2021, https://www.theguardian.com/environment/2021/may/27/rapid-heating-of-indian-o cean-worsening-cyclones-say-scientists. Accessed 5 May 2023.

Wenegrat, J. O., et al. “A Century of Observed Temperature Change in the Indian Ocean.” Geophysical Research Letters, 25 June 2022. Advanced Earth and Space Sciences, https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL098217 :~:text=Sea% 2Dsurface%20temperature%20(SST),et%20al.%2C%202014). Accessed 5 May 2023.

Understanding the Indian Ocean Dipole

The Indian Ocean Dipole (IOD), also referred to as the Indian Niño, is a seasonal climate index that is one of the most vital considerations in seasonal forecasting for the Indian Ocean’s rim countries. The IOD is caused by a variance in sea surface temperatures (SST) and rainfall between the western and eastern parts of the Indian Ocean, resulting in these areas becoming alternatively warmer and then colder. There are three phases of the IOD, neutral, positive, and negative, each of the phases occurring every 3-5 years. Positive or negative IOD phases usually begin in the spring or summer, peak during autumn, and ends in late November.

The neutral phase of the Indian Ocean Dipole is characterized by temperatures that are close to normal across the tropical Indian Ocean. During this phase, water from the Pacific Ocean flows between the Islands of Indonesia, with westerly winds blowing along the equator. The air rises above this area and falls over the western Indian Ocean. During the negative phase of this seasonal climate phenomenon, the westerly winds intensify, resulting in warmer waters concentrating in the eastern Indian Ocean, south of Indonesia, and cooler than normal waters concentrating off the east coast of Africa. As a result of this SST irregularity, heavier rainfall in the eastern Indian Ocean and dryer conditions in the western Indian Ocean ensues. The opposite phenomenon occurs during the positive phase of the IOD, with westerly winds weakening significantly and easterly winds forming. Warmer waters are concentrated off of the African east coast and cooler waters are concentrated south of Indonesia. Consequently, heavier rainfall occurs in countries bordering the western Indian Ocean and countries in the eastern part of the Indian Ocean are subject to dryer weather conditions.

(“Understanding the Indian Ocean Dipole.” YouTube, uploaded by Bureau of Meteorology, 5 July 2016, www.youtube.com/watch?v=J6hOVatamYs.)

Significant effects of the Indian Ocean Dipole anomalies are experienced mostly in Western and Southern Australia and in East Africa. A positive IOD event results in significantly drier conditions and less rainfall in southern and north-western Australia, thus increasing the chances of bushfires in the region. On the other hand, a positive IOD results in significantly increased rainfall during the East African Short Rains (EASR), occurring from October to December. This increased rainfall has resulted in frequent and increased flooding in East African countries. The effects of the Indian Ocean Dipole are felt in India especially when stronger positive IODs occur, leading to exceptionally heavy rainfall across the Indian subcontinent.

Climate change and the resulting climate variability is having a significant impact on the Indian Ocean Dipole and its positive and negative phases, leading to severe weather occurrences, such as megadroughts and deadly floods in countries surrounding the Indian Ocean. As the climate warms across the globe, extremely positive IOD events are increasing in frequency. In fact, four extreme positive events have occurred in the last sixty years, a significant increase in frequency compared to the mere six extreme events that have occurred in the preceding one-thousand years. Currently, such extreme events are occurring at a frequency of once every thirteen years, however, scientists postulate that in the coming future, these events could occur as close as once every six years.

Works Cited

“Understanding the Indian Ocean Dipole.” YouTube, uploaded by Bureau of Meteorology, 5 July 2016, www.youtube.com/watch?v=J6hOVatamYs.

“The Indian Ocean Dipole and Its Impact – | Prof TRACEY ROGERS.” YouTube, uploaded by Tracey Rogers UNSW Sydney, 18 Jan. 2019, www.youtube.com/watch?v=3Dk1r_lid18.

Dutton, Jan. “What Is the Indian Ocean Dipole?” World Climate Service, 2 Sept. 2021, www.worldclimateservice.com/2021/09/02/indian-ocean-dipole/. Accessed 3 May 2023.

“Indian Ocean Dipole: What Is It and Why Is It Linked to Floods and Bushfires?” BBC, 7 Dec. 2019, www.bbc.com/news/science-environment-50602971. Accessed 3 May 2023.

“Sea Level Key Indicators.” NASA, sealevel.jpl.nasa.gov/data/vital-signs/indian-ocean-dipole/. Accessed 3 May 2023.

Siliezar, Juan. “How Climate Change Impacts the Indian Ocean Dipole, Leading to Severe Droughts and Floods.” Brown, 4 Jan. 2023, www.brown.edu/news/2023-01-04/droughts-floods. Accessed 3 May 2023.

Hirons, L. and Turner, A. (2018) The impact of Indian Ocean mean-state biases in climate models on the representation of the East African short rains. Journal of Climate, 31 (16). pp. 6611-6631. ISSN 1520-0442 doi: https://doi.org/10.1175/JCLID-17-0804.1 Available at https://centaur.reading.ac.uk/76818/

Cai, Wenju, et al. “Guest Post: Why Climate Change Will Cause More ‘Strong’ Indian Ocean Dipole Events.” Carbon Brief: Clear on Climate, 30 Nov. 2020,

www.carbonbrief.org/guest-post-why-climate-change-will-cause-more-strong-indian-ocean-dipol e-events/. Accessed 3 May 2023.

Cyclone Freddy – The Longest-Lived Cyclone that Traveled Across the Indian Ocean


Cyclone Freddy was a record-breaking storm of exceptional length, intensity, and lethality, that caused devastating damage to countries across the entire Indian Ocean. The storm formed off the northwestern coast of Australia on February 3rd, 2023, making its first landfall on Madagascar’s eastern coast and then moving west to Mozambique in late February. This cyclone traveled over land as a tropical depression with a center localized near the border between Malawi and Mozambique, wreaking immense havoc in both countries.

Source: United Nations Office for the Coordination of Humanitarian Affairs (UNOCHA)


The storm caused immense damage to Malawi and Mozambique, including the destruction of infrastructure, homes, schools, and public health facilities. 564,000 people were displaced from their homes in Malawi, with the death toll totaling to almost 700. In Mozambique, over 180,000 people were displaced, with at least 184 people killed. The island of Madagascar had a death toll of at least 17.

The agricultural sector in these countries was also significantly impacted as a result of the heavy flooding. “[The] highest reported impact was in Malawi’s agriculture sector, where a total of 2,267,458 people (51% women) lost their crops and livestock as the cyclone destroyed more than 442,000 acres (179,223 hectares) of land” (Tropical Cyclone Freddy). In Mozambique, 92,000 hectares of crops have been affected, resulting in widespread food insecurity in the nation. Already affected by multiple cyclones earlier this year, Madagascar is facing “catastrophic hunger” (Tropical Cyclone Freddy), with 60%-90% of the agricultural land in the country badly damaged.

Role of Climate Change

One of the main questions raised following climate events such as this is how important of a role has climate change played in this storm. Attribution science (also referred to as extreme event attribution) is a “relatively recent field in climate science that tries to quantitatively determine if an extreme weather event was caused or worsened by climate change or was simply due to natural variations” (Menga). It is still too early to determine whether climate change played a crucial role in Cyclone Freddy’s intensity and longevity, but the evidence from past research and analysis of storms such as this is that as the climate warms, more intense storms are more likely to happen. According to the Intergovernmental Panel on Climate Change (IPCC), “There is a projected increase of average tropical cyclone wind speeds and associated heavy precipitation and of the proportion of category 4-5 tropical cyclones” (Tropical Cyclone Freddy may set a new record).

Source: Carbon Brief

Works Cited

Bartlett, Kate. “Cyclone Freddy shattered records. People lost everything. How does the healing begin?” NPR, 17 March 2023, https://www.npr.org/sections/goatsandsoda/2023/03/17/1164256900/cyclone-freddy-shatt ered-records-people-lost-everything-how-does-the-healing-beg. Accessed 3 May 2023.

Menga, Marina. “Climate intelligence at work: the case of Cyclone Freddy – Foresight.” Climate Foresight, 19 April 2023,


-freddy/. Accessed 3 May 2023.

Myronets, Anastasia. “Essential Facts About Tropical Cyclone Freddy.” RainViewer, 5 April 2023, https://www.rainviewer.com/blog/tropical-cyclone-freddy.html. Accessed 3 May


“Tropical Cyclone Freddy.” Center for Disaster Philanthropy, 24 April 2023, https://disasterphilanthropy.org/disasters/tropical-cyclone-freddy/. Accessed 3 May 2023.

“Tropical Cyclone Freddy may set new record | World Meteorological Organization.” World Meteorological Organization |, 10 March 2023, https://public.wmo.int/en/media/news/tropical-cyclone-freddy-may-set-new-record. Accessed 3 May 2023.

The Ulhas River Estuary Story

by Aneesh Parnerkar

An ecological and visual nexus with huge and extremely important social explications, the Ulhas River and its estuary form the impetus of this research paper. The river, rising in Maharashtra’s Sahyadri Mountains, flows through Thane, Raigad, and Mumbai before draining into the Arabian Sea. The estuary of the river, located at the river’s mouth, is an ecological hub home to numerous marine migrants and amphidromous species. Furthermore, The Ulhas River Estuary is a paradise for nature enthusiasts and a treasure trove for local fishing communities.

Source: Menon and Mahajan

The above maps help clarify the bearings of the Ulhas River along the western coast of India. The river fosters a delta as it runs into the Arabian Sea, which is known as the Ulhas Estuary. The estuary is located near the mouth of the Thane Creek, a tidal creek that connects Mumbai to the mainland. Thane Creek is one of the region’s main inlets and is responsible for the tidal changes in the Ulhas River.

The Ulhas River Estuary is a vast expanse of mangrove forests, mudflats, and sandbanks. The mangroves play a significant role in protecting the region from tidal surges while serving as a breeding ground for diverse species of fish and crustaceans. According to a research study published in the Journal of Environmental Biology, “the Ulhas River Estuary was recorded to shelter a total of 105 species, belonging to 4 classes, 19 orders, 44 families, and 75 genera. Based on the estuarine use functional guild categorization, 51.42% of species were marine migrants, followed by amphidromous species.

Source : Lal et al.

The aforementioned research study, among discernible substitutes, signifies the nursery function of the estuary for sustaining commercially important marine fisheries resources” (Lal et al.). It is naturally a source of livelihood for the local fishermen, who rely on the river’s resources for their daily catch. The fishermen use traditional methods of fishing, such as using nets and boats, and are known for their expertise in catching distinct types of fish in the area.

Source: ““Ulhas River Comes close to Danger Mark, Thane on Alert”

As you explore the Ulhas River Estuary, you will notice the vast expanse of the mangrove forests. These forests are a unique ecosystem that supports a diverse range of plant and animal species. The trees have a peculiar root system that grows above the ground, which allows them to absorb nutrients and oxygen from the air. The mangrove forests are also an excellent habitat for the estuary’s wildlife, including reptiles, birds, and mammals. Specifically, the mudflats are also home to many species of migratory birds, making the region a popular destination for bird watchers.

Source: IStockPhoto                                                                           Source : Geography Five

If you’re lucky, you may spot the estuary’s most famous resident, the saltwater crocodile. These reptiles are native to the region and can be spotted basking in the sun on the estuary’s mudflats. While they are usually harmless, it is advisable to keep a safe distance from them.

Source : Thomsen

In conclusion, the Ulhas River Estuary is a true gem of nature that must be explored. Its serene beauty, diverse wildlife, and unique ecosystem make it a must-visit destination for nature lovers and adventure seekers alike. Whether you’re a bird watcher, a fisherman, or just someone who loves to soak in nature’s beauty, the Ulhas River Estuary is an experience you won’t forget.


Works Cited

Five, Geography. “Mumbai’s Mangroves: Mangroves in Mumbai.” Mumbai’s Mangroves, 27 Nov.                                                                                                                                               2015,

mumbaismangroves.blogspot.com/2015/11/map-of-mumbai-area-mangroves-green.html. Accessed 10 May 2023.

IStockPhoto,                https://www.istockphoto.com/photos/estuary-mangrove-tree-land-wetland. Accessed 10 May 2023.

Lal, D. M., et al. “Fish Community Structure as an Indicator of the Ecological Significance: A Study from Ulhas River Estuary, Western Coast of India.” Journal of Environmental Biology, vol. 41, no. 4, July 2020, pp. 745–54, https://doi.org/10.22438/jeb/41/4/mrn-1364. Accessed 10

May 2023.

Menon, J. S., and S. V. Mahajan. “Site-Wise Mercury Levels in Ulhas River Estuary and Thane Creek near Mumbai, India and Its Relation to Water Parameters.” Our Nature, vol. 8, no. 1, Jan. 1970, pp. 170–79, https://doi.org/10.3126/on.v8i1.4325. Accessed 10 May 2023.

“Ulhas River Comes close to Danger Mark, Thane on Alert.” The Indian Express, 31 July 2019, indianexpress.com/article/cities/mumbai/ulhas-river-comes-close-to-danger-mark-thane-on-alert- 5865025/. Accessed 10 May 2023.

Thomsen, Paul. “English: Photographer: Paul Thomsen (WILDFOTO.COM.AU).” Wikimedia Commons,                                        8                                        Nov.                                                         2006, commons.wikimedia.org/wiki/File:Saltwater_Crocodile_on_a_river_bank.jpg. Accessed 10 May 2023.

The Declining Numbers of Olive Ridley Sea Turtles in Orissa

by Jainam S Jain

A single Olive Ridley Sea Turtle can lay about 110–140 eggs, and reports indicate that just one out of every thousand hatchlings that enter the sea grows to full adulthood (Kumar et al 33). In recent years, the Orissa Olive Ridley population has experienced severe mortality with over ten thousand turtles being counted dead on the shore each year just due to fishery-related accidental death. Before reaching the vast oceans, the eggs and hatchlings must survive through a lot of problems. As a result of their exceedingly low survival rate, they have been placed on the International Union for Conservation of Nature’s “red list”. This vulnerability is a result of their habitats being destroyed by various significant activities (Kumar and Ghosh). Unless the situations that threaten their survival and reproduction improve, they might be on the verge of extinction. This paper intends to investigate that it is not only fisheries that are to be blamed for the decline of these vulnerable turtles but factors like climate change, predators, and developmental activities too. Year after year, natural and anthropogenic pressures on the turtle fauna at the rookeries are increasing. Threats to nesting environments are described as any action or procedure that has the potential to modify the sand substrate of the nesting beach, damage or kill sea turtles or their eggs or disturb regular behavior patterns. (Witherington 1). There are numerous other potential reasons associated with the downfall of these turtle populations.

The Pacific Ridley Sea Turtle, often known as the Olive Ridley Sea Turtle (Lepidochelys olivacea), has been on this planet even before dinosaurs existed. These species of turtle belong to the Cheloniidae family. These turtles are the most abundant among all the turtles on the planet and one of the smallest of their kind. Olive Ridley turtles can be found almost anywhere in the world’s tropical waters. These turtles have an obvious global significance of mass nesting rookeries in the tropics, especially in Orissa, known for having the highest number of nesting in the world, La Escobilla in Mexico, and Playa Ostional and Playa Nancite in Costa Rica are also major mass-nesting rookeries (Shanker 3). Gahirmatha marine sanctuary, Rushikulya Rookeries, and the river mouth of Devi are the prominent places where Arribadas occur. The rest of the coastline finds sporadic nesting on them.

Due to global warming, the turtles will be among the first victims of climate change, as the gender of the hatchlings depends a lot upon the temperature. Warm incubation temperatures result in female hatchlings whereas cooler incubation temperatures result in male hatchlings. As sand temperatures rise on nesting beaches, the sex ratio of hatchlings becomes virtually exclusively female and this might create an imbalance in their sex ratio. Sumedha Korgaonkar, who is an expert on Olive Ridley turtles, states that these eggs can withstand a temperature of up to 33 degrees Celsius, and an optimum temperature of 29.5 degrees Celsius is required to keep the sex ratios balanced (qtd. in Gayakwad). This will pose a threat to the turtle population as their process of reproduction will decline.

Apart from the change in the possible sex ratio, climate change affects the turtles’ habitats, food sources, and nesting activities adversely, as the oceans are getting warmer with time. Cooler oceans provide more food sources for sea turtles as they are more suitable for fish to reproduce. Also, oxygen levels in warm waters are less than normal which makes it harder for Olive Ridley turtles to breathe underwater.

The sea level rise is taking away the space that these turtles use for nesting and breeding on beaches, thus resulting in fewer hatchlings. Several observations were made by the scientists present in the Arribadas as the female ridleys started scooping out sand with her flippers for making a pot-shaped chamber to create space for nesting, inadvertently scooping out eggs laid by another female earlier (Mundappa). A female crawled over another female who was busy laying her eggs further ahead. She chose a nest less than a meter away from the first female, and when she began digging, she completely covered her neighbor in the sand (Mundappa).

The abrupt and dramatic changes in coastal morphology are caused by episodic coastal hazards linked with cyclonic storms (Grases 346). Because of the longer monsoon season, the peak hatching period, which usually concludes by the end of March, has been extended until April-May.  The eggs are destroyed by beach erosion induced by southwest winds immediately before they can hatch. Net loss due to inundation and erosion accounted for 23% of overall nesting loss due to natural factors at the Gahirmatha rookery (Behara 438). The Olive Ridleys usually prefer clean and warm beaches to nest but after the cyclones, the beaches are full of debris which makes the location less favorable for them.

On October 29, 1999, Orissa was pummelling by a Super Cyclonic Storm that made landfall near Paradip. The estimated maximum wind speed in the core area was 260-270 kmph, resulting in a massive storm surge that caused a sea-level elevation of more than 20 feet and the loss of approximately 10,000 lives. It was accompanied by unusually severe rainfall, which caused deadly floods and blocked the state off from the rest of the country (Kalsi 1). This Super Cyclone wreaked havoc on the shoreline, eroding beaches and destroying numerous key nesting sites that had been fragmented into islands or were submerged beneath the waves. As a result, many eggs were inundated in the oceans, which did not provide suitable conditions for hatching. Since 1999, mass turtle nestings have happened on alternating years, occasionally after a 2–3-year interval as well.

The Rushikulya rookery on India’s east coast is one of the major mass breeding areas for Olive Ridley sea turtles. This yearly mass nesting event (arribada) is triggered by finely interwound geo-ecological cues, which are frequently interrupted by anthropogenic influences and extreme weather phenomena like tropical cyclones. The impact of category five storm Fani (which made landfall on 03 May 2019, summer rather than autumn) on the Rushikulya rookery was studied for the first time using remote sensing and GIS technology (Mishra), as very severe but untimely cyclones are expected to become more common as a result of climate change. The beach along the Rushikulya rookery withdrew a hundred meters inward as a result of storm Fani (2019), which led to a halt to mass nesting that year (Mishra). The fragmentation of the spit, which appears to be a necessary habitat and protective structure for successful mass nesting, was the most noticeable aspect. Due to the spit’s natural reconstruction and potentially cyclone-driven nutrient enrichment, the next year (2020) saw an extremely successful mass nesting. This study will serve as the first baseline data on the anticipated impact of such extreme weather events on migratory marine turtles in India.

Amlan Nayak, the divisional forest officer (DFO) in Berhampur estimated that 15% – 20% of the record 5.5 lakh eggs deposited by sea turtles in the five-kilometer-long nesting sites from March 28 to April 4 (2022) may have been harmed due to cyclone Asani and beach erosion. Since March 25, around 5.01 lakh sea turtles have come to the Gahirmatha Marine Sanctuary in Kendrapara district for mass nesting (arribada) for over 4 days, he said (India). As the turtle nestings were high this year, there were high expectations of good hatches but due to the cyclone, high tides, and soil erosion, the numbers went lower.

Furthermore, Biswas Pandav in the Indian Ocean Turtle Newsletter has said that Casuarina plantations in Orissa are believed to have had negative impacts on nesting beaches and the process of nesting itself (27). The plantation has disrupted Orissa’s coastal ecology and resulted in environmental degradation of the shore. To mitigate the effects of cyclones in the region, Casuarina was imported from Australia and widely planted on the beaches, which acted as a cyclone barrier and shelter belt, thus preventing beach erosion (Pandav 27, Schmid 215). But the plantations changed the topography of the beach through their root growth. This has the potential to significantly impede natural processes along the coastal system.

Casuarina is recognized to be detrimental to nesting Olive Ridley populations in multiple ways. Devi River mouth has lost much of its nesting habitat due to the plantations. While 50% of Rushikulya’s mass nesting beach is devoid of the plantation, the remaining sections are surrounded by extensive Casuarina plantations (Tripathy 439). The eggs and hatchlings get entangled in the thick root masses and litter fall which destroys them. Natural predators like jackals, hyenas, monitor lizards, wild pigs, crabs, etc. breed in dense vegetation near coastal dunes, putting additional predation pressure on nesting females, eggs, and hatchlings. Jackals and dogs prey on the nests that are built inside the Casuarina plants.

Furthermore, under natural conditions, after they emerge from the nest, the Olive Ridley hatchlings move directly toward the sea. The offsprings need light to follow, so the moonlight on the waves guides them toward the ocean (Pandav 26). On their way to the ocean, most of them die of dehydration and exhaustion or get eaten by predators. Any form of artificial light source present near the nesting beach can interrupt the hatchlings’ sea-finding behavior because they tend to go towards the source of light instead of the sea. The lights installed in coastal regions as a product of development are much brighter than the moonlight, which misdirects them away from the sea. This way the baby turtles either get crushed by the humans or fed on by stray dogs or crows. This effect on the hatchlings is known as Hatchling Disorientation and it happens at Rushikulya rookery to a large extent.

Furthering the coastal development and making the situation worse for the turtles is the construction of new water sports and coastal highways near the nesting habitats (Behara and Tripathy). The seaports are made to connect with landlocked states like Chhattisgarh, Jharkhand, Bihar, and Uttar Pradesh. This is further reducing the area for the turtles to breed and nest. The extensive dredging of shipping channels may influence water turbidity and light penetration, as well as benthic habitat, with possible consequences for the entire food chain, including the Olive Ridley turtles. This development will lead to more infrastructure and tourism on the coastline, further increasing marine and light pollution and making it difficult for the turtles to survive. There are chances of oil spills happening in this region due to the establishment of ports, cargo ships, and many petroleum-based industries.

Turtles graze on some organisms to keep the ecology balanced and they are also a vital source of food for other creatures, especially when they are young and easy to predate. Vultures, frigate birds, crabs, raccoons, coyotes, iguanas, and snakes prey on hatchlings as they make their way across the dunes to the ocean (Tripathy 442). Possible hatchling predators in the water include oceanic fishes, sharks, and crocodiles. Except for sharks, adults have few known predators, although killer whales are occasionally responsible for assaults. Jaguars may pose a hazard to females that are breeding on land. Notably, the jaguar is the only cat with a powerful enough bite to pierce a sea turtle’s shell. This inevitably leads to a significant decline in the number of turtle nests, eggs laid, hatchlings, and turtles.

To conclude the research, the population of the Olive Ridleys has drastically fallen in the last three decades due to changes in the climate causing more frequent cyclones. To mitigate the aftermath of these cyclones, casuarina plantations were brought in. Unfortunately, this backfired on the turtles, resulting in a further decline in their population. In addition to these, developmental activities such as the building of ports and defense facilities, laying of coastal roads, and development to support the increasing tourism, have significantly impacted the population of these turtles. Furthermore, predators have a key role in the decline of these populations as the turtles are the main source of their diet. All these factors have together vastly influenced the population of Olive Ridleys in the seas.


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Tripathy, Basudev & Rajasekhar, P. “Natural and anthropogenic threats to olive ridley sea turtles (Lepidochelys olivacea) at the Rushikulya rookery of Orissa coast, India”. Indian Journal of Geo-Marine Science, 2009, 38, 439-443.

Schmid, Jill L., et al. “The Effect of Australian Pine (Casuarina Equisetifolia) Removal on Loggerhead Sea Turtle (Caretta Caretta) Incubation Temperatures on Keewaydin Island, Florida.” Journal of Coastal Research, vol. 10055, 2008, pp. 214–220., https://doi.org/10.2112/si55-001.1.s

Shanker, Kartik. “Marine Turtles in the Indian Subcontinent: A Brief History.” Marine Turtles of the Indian Ocean, edited by B C Choudhury, Orient Longman Private Limited, Chennai, Tamil Nadu, 2006, pp. 3–16.

Gulf of Mannar, one of the world’s richest Marine Biodiversity

India and Sri Lanka are divided by the Gulf of Mannar, a small body of shallow water off the southern coast of India. Being one of the richest hotspots for marine biodiversity, it has an area of roughly 10,500 square kilometres and is home to a wide variety of marine life.

Source: Drishti IAS

The Gulf of Mannar is home to three distinct coastal ecosystems, including coral reefs, seagrass beds, and mangroves. From the perspective of marine biodiversity, this region is one of the richest in the world. It is renowned for its exceptional biological wealth and is a repository of marine diversity of significant global importance.These reefs are home to a large number of fish species, as well as other marine organisms such as sea turtles, dolphins, and whales. The waters of the Gulf of Mannar are also home to several species of sharks, including the endangered whale shark.

Source: UNESCO

The Gulf of Mannar is also a major fishing ground, with over 500,000 people depending on it for their livelihood. However, overfishing, destructive fishing practices, and pollution have led to a decline in the population of many marine species in the area.

  Source: TheIndia

To protect the marine ecosystem of the Gulf of Mannar, the Indian government has established the Gulf of Mannar Marine National Park, which covers an area of 560 square kilometers. The park includes 21 islands and islets, as well as the surrounding waters. The park is home to several endangered species, including the dugong, a large marine mammal that is often called the “sea cow.”

Source: India.com

Furthermore, initiatives are being undertaken to encourage sustainable fishing methods in the Gulf of Mannar. In order to maintain crucial fish habitats, the government has established marine protected zones, and local populations are being urged to adopt eco-friendly fishing techniques. These initiatives are essential to safeguarding the Gulf of Mannar’s rich biodiversity for future generations.


Arambol, the Sweet Water Lagoon by the Beach

Arambol is a small village located in the northernmost part of Goa, India. It is a beautiful beach town surrounded by greenery and breathtaking views. One of the main attractions of Arambol is the Sweet Water Lagoon. The lagoon is located near the beach and is a popular spot for tourists to visit.

Source: Thrillophilia

The Sweet Water Lagoon is a small lake that is separated from the Arabian Sea by a strip of sand. The water in the lagoon is sweet and is not affected by the tides. The lagoon is surrounded by palm trees, rocks and hills which makes it a perfect spot for those who love nature and scenic beauty. The lagoon is a popular spot for swimming and sunbathing. The water is calm and shallow, making it perfect for children to enjoy. There are also many small shacks located around the lagoon that offer refreshments and snacks.

Source: Wikivoyage

Another interesting activity that tourists can indulge in at the Sweet Water Lagoon is paddle boating. Visitors can rent a paddle boat and explore the lagoon while enjoying the beautiful views. The Sweet Water Lagoon is a great spot to relax and unwind. It is away from the hustle and bustle of the city and is a perfect escape for those who want to be surrounded by nature. It is also a great place for photographers and nature lovers who can capture the beautiful views and scenery of the lagoon.

Source: Dreamstime.com

As for the species that can be found in the area, Arambol is known for its rich marine life. The sea around the beach is home to a variety of fish, including mackerel, tuna, and barracuda. If you are lucky, you may also spot dolphins playing in the water. The lagoon is home to a variety of bird species, including kingfishers, herons, and egrets. You can also find crabs and other small marine creatures in the lagoon.

Source: Goa Water World

In conclusion, Arambol and its sweet water lagoon by the beach are beautiful places to visit if you want to experience nature at its best. Whether you are a wildlife enthusiast or just want to relax on the beach, Arambol has something to offer for everyone.


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


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.


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 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!