Rhodoliths:The Under Sea Red Algae Calcium Deposits

Heard of corals, the creatures found in the ocean? And the answer is, yes! Those coelentrates that build big deposits of calcium, sometimes structures as large as Great Barrier Reef of Australia. Know about algae, the tiny little plants building deposits of calcium around themselves thus creating deposits spreading kilometers of undersea landscape!

These unique plants build their hard layers out of calcium carbonate (CaCO₃), which provides them rigid structure, and gives the beds they are located in structural complexity, and enables them to create stable habitats for other species. Called  rhodoliths, these calcium deposits have been recently reported following a joint study by Conservation International and Brazilian scientists of the Abrolhos Shelf in Brazil. Rhodoliths accounts for approximately 5 percent of the world's total carbonate banks.

 

Undersea exploration of rhodoliths. (Courtesy: Conservation International)

Rhodoliths are colorful, unattached, branching, crustose benthic marine red algae that resemble coral. 

Often mistaken as coral, rhodoliths are roughly spherical objects on the ocean floor that are made of many layers of hard red algae. Together with kelp beds, seagrass meadows, and coral reefs, rhodoliths are one of Earth’s largest seabed primary producer communities. 

 

 A two-year seabed study off the eastern coast of Brazil confirmed that the Abrolhos shelf is home to the largest known continuous bed of rhodoliths in the world. The study  conducted by scientists with Brazil's National System of Biodiversity Research (SISBIOTA) and Conservation International, was published  in April in the online journal PLoS ONE.

 

Using remote operated vehicles (ROVs), side scan sonar and SCUBA diving, the researchers measured the size of the rhodolith bed to occupy 20,902 square kilometers, an area nearly the size of El Salvador.

 

According to Prof. Rodrigo Moura of Rio de Janeiro Federal University and co-author of the study the finding of largest rhodolith bed in the world on the seabed of Brazil’s Abrolhos shelf makes this part of ocean very important. "Rhodoliths play a critical role in a healthy marine ecosystem by providing primary habitat that can yield diverse and abundant communities of fish and invertebrates of high commercial value."

 

"Rhodolith beds like this one are major carbonate factories, and could play a significant role in regulating global climate," said Les Kaufman, a senior marine scientist with Conservation International. "But in order to understand what that role might be, and how significant a role, we must learn more about them."

 

Rhodolith beds face threats from ocean acidification, sedimentation from land-based sources and large scale dredging and mining. Acidification looms the largest and cannot be managed regionally, but the other threats to the health of the rhodolith bed of Abrolhos shelf can be managed on a local scale.

 

The rhodolith bed falls within the Abrolhos seascape, a 9,5000 square kilometer (37,000 square miles) area of ocean where Conservation International works with the Brazilian government and community organizations to conserve and manage ocean resources.

 

Based on high vulnerability of coralline algae to ocean acidification, the rhodolith beds are likely to face profound restructuring in the coming decades, believes the lead author of the study, Gilberto Amado-Filho, a researcher at Rio de Janeiro Botanical Garden. "With the Abrolhos shelf bed producing an estimated 25 million metric tons of calcium carbonate a year, its protection and continued study should be prioritized", says Gilberto.

 

In addition to the rhodolith beds, the study also revealed huge areas of seabed covered by seaweeds, deep holes (buracas) harboring dense clouds of juvenile fishes, and deep reefs composed of corals and coralline algae. With the vast size of rhodoliths  revealed in seascapes, scientists are worried of dangers to the reefs  that hug the coast and islands, nourishing tourism and fisheries in coastal Bahia.

Time for Mangoes: The King of Fruits

Mango brings to mind a mixed feeling of sweet and sour, of a fruit found in hundreds of varieties, of different colour combinations of yellow, red, pink and green. Its size and shape varies with the variety of different tastes. Mango is a fruit which both rich and poor can afford, the only difference could be of the costly or common varieties.

A mango tree with unripe fruits

Mango belongs to the genus Mangifera and family Anacardiaceae. A fruit primarily belonging to Indian subcontinent it has spread to any part of the world which has warm and humid tropical subtropical climate. The Indian species Mangifera indica has hundreds of varieties or cultivars of different attributes.

Mango is a highly respectable tree. It is the national tree of Bangladesh. The mango fruit boasts of national fruit status in India and Pakistan.

The concern here is not of mango as a fruit alone. Visit a mango tree and you could find an awful variety of tiny insects on it, some good for the tree, and some having the distinction of being a pest. The mango farmers are scared of those pests. Some common ones are red ants moving forward and backward on tree trunk, branches and leaves. They even join leaves and make their nests. They are alert and fearsome. If the crop is infested by pests the crop yield can be reduced, and incur losses to the orchard owner.



Mango is an example of nature's ability to evolve and develop diverse life forms, the biodiversity for our benefit, due to its existence in the forms of different cultivars. The fruit is also an example of evolutionary anachronism because the fruit possibly coevolved with the now extinct megafauna of Pleistocene age because the large animals of that time could swallow the fruit and help in its dispersal, similar to Avacado.

True, a mango tree is a world of life forms thriving around it. There are some 492 species on insects, 17 species of mites, 26 species of nematodes which are reported globally to infest mango trees, flower, fruits, and roots. Out of those awesome numbers some 45 per cent are reported to be found in India. Besides mango trees are abode to birds, bats, wasps, bees, ants. Near the tree roots, in moist soil one can locate slugs, tiny mollusks, earthworms, centipedes. Some flies and bees are important to the mango crop as they are the main pollinators. Melipona Sp.  and Trigona Sp. are main pollinators of the mango flowers.

The dreaded pests of mango are: leaf webber (Orthaga euadrusalis), mango hopper (Idioscopus clypealis, Idioscopus nitidulus, Amritodus atkinsoni), mango mealy bug (Drosicha mangiferae), fruitfly (Daccus dorsalis, D. zonalus, D. correctus) which affect mature fruits, the stem borer (Apsylla cistellata), and shoot gall psylla (Apsylla cistellata).

A species of bird, the Asian Koel (Eudynamis scolopaceus) is almost synonymous with the mango season in northern India. Its breeding season coinciding with mango season, repeated male-bird song of Koo.Ooo and the females shrill Kik-Kik-Kik are reminders to the arrival of mango season.

Some 25 kilometers from Lucknow, the capital of India's most populous state, the Uttar pradesh, there is an Institute at Rehman Kheda, which had its beginning in 1972, as a mango research station, but now stands as a tall institution dedicated to research on  subtropical fruits like mango, guavas, papaya, litchi, Aonla, Bael, Jamun. Other fruits are being added to the list for further research and their economic utilization. The  Central Institute of Tropical Horticulture is now a pioneering institute for mango research and has developed several better varieties of mangoes.

Mango is a nutritious fruit full with  vitamin C, vitamin B6, folate, potassium, copper, provitamin A carotenoids, prebiotic dietary fiber, amino acids, omega-3 and-6 polyunsaturated fatty acids. The mango triterpene lupeol is known to be effective in controlling skin and prostate cancers !