Coral Biology & Diversity

The tropical latitudes of the oceans can be called the deserts of the ocean due to their similarity with terrestrial deserts, which are barren and relatively sterile places. The reason for this phenomenon is that the surface waters of the tropical oceans are so warm and thus they tend to float on top of the colder water underneath, inhibiting nutrient upwelling from the deep which brings nutrients to the ocean surface. However, coral reefs are a brilliant exception to the general scarcity of life in tropical oceans; they are known as the oases of ocean deserts

Scleractinian corals

The tropical regions of the oceans are often referred to as the "oceanic deserts" because they share similarities with terrestrial deserts, characterized by barrenness and relatively low productivity. The reason for this phenomenon is that the surface waters of the tropical oceans are so warm. Thus they tend to float on top of the colder water underneath, inhibiting nutrient upwelling from the deep which brings nutrients to the ocean surface. Nevertheless, coral reefs stand out as a remarkable exception to the typical scarcity of life in tropical oceans, earning them the title of "oases" within the oceanic deserts. If we consider the area of coral reefs, it comprises less than 0.2% of the world's ocean, yet it is home to a wide array of marine organisms. Karlson and Cornell (1999) note that when considering the entire marine ecosystem, coral reefs exhibit the greatest diversity per unit area. It is estimated that almost 4-5% of all species or about 91,000 are found on coral reefs. We can find 32 out of 34 recognized animal phyla in coral reefs where there are only 9 phyla in the tropical rainforests (Porter and Tougas, 2001). Although corals are found in polar and temperate waters, coral reefs only develop in the tropics. This is primarily because there are two types of corals: hermatypic corals, which produce reefs, and ahermatypic corals, which do not form reefs. While ahermatypic corals have a worldwide distribution, hermatypic corals are found only in the tropics

Record of a central Indo-Pacific corallimorph in the Lakshadweep atolls and its competition with the hard corals

Coral reefs are disappearing worldwide because of mass bleaching, natural disasters, diseases and anthropogenic stressors. This leaves a large area of unutilised substratum, to which other benthic organisms, like corallimorpharians (CMs), anemones and macroalgae, can move in. In this article, we describe, for the first time, the competition for space between a CM and the hard corals in Kavaratti Atoll in the Indian Ocean. This is the first reported instance of an invasion of CM in the entire Lakshadweep Islands. The CM Rhodactis bryoides Haddon and Shackleton, 1893, is identified by morphological and molecular analysis. The species has not so far been reported from the western Indian Ocean area. We monitored the rate of invasion for six months to figure out the growth rate of CMs. This area did not have any prominent causative factors for CM outbreaks, such as external disturbances and nutrient enrichment. Yet our study showed that CMs are successful in the competition for space. More research needs to be done into the biology of this species, how it interacts with other benthic groups and how the environment facilitates its spread

Sponge fauna of the Lakshadweep Islands of Indian Ocean

The present study deals with four new records of sponges found at Lakshadweep area and a checklist of sponges reported off. The new records are Agelas oroides, Callyspongia (Cladochalina) aculeata, Raspailia (Clathriodendron) arbuscula and Stylissa massa. Details about the species diversity of common sponges, massive sponges, boring sponges of the area are discussed and presented

प्रवाल भित्तियाँ : समुद्र के शानदान जैवविविधता हॉटस्पॉट

महासागर के उष्‍णकटिबंधीय अक्षांशों को समुद्र के रेगिस्‍तान के रूप में जाना जाता है, क्‍योंकि ये स्‍थलीय रेगिस्‍तानों के समान बंजर स्‍थान हैं। इस घटना का कारण यह है कि उष्‍णकटिबंधीय समुद्र गरम होते हैं, ये नीचे ठंडे पानी के ऊपर तैरते हैं। यह पोषक तत्‍वों को गहराई से ऊपर लाने से रोकता है, जो पोषक तत्‍वों को समुद्र की सतह तक लाता है। उष्‍णकटिबंधीय समुद्रों में सामान्‍य तौर पर जीवन की कमी के लिए प्रवाल भित्तियॉं एक शानदार अपवाद हैं। अगर हम प्रवाल भित्तियों के क्षेत्र पर विचार करते हैं, तो यह विश्‍व के महासागर का केवल 3% है, फिर भी यह विभिन्‍न प्रकार के समुद्र जीवों का आवास स्‍थान है। पूरे समुद्रीपारिस्थितिक तंत्र में प्रवालभित्तियों में प्रति इकाई क्षेत्र में सबसे असाधारण जैवविविधता है। यह अनुमान लगाया गया था कि सभी प्रजातियों में से लगभग 4-5% या लगभग 91,000 प्रजातियॉं प्रवाल भित्तियों पर पायी जाती हैं। हालांकि प्रवाल ध्रुवीय और समशीतोष्‍ण जल में पाए जाते हैं, केवल उष्‍णकटिबंधीय स्‍थानों में प्रवाल भित्तियों का विकास होता है। मुख्‍यतः दो प्रकार के प्रवाल होते हैं, जोकि हेर्माटिपिक प्रवाल, जो प्रवाल भित्तियॉं बनाते हैं (चित्र 1) और एहेर्माटिपिक प्रवाल, जो प्रवाल भित्तियॉं नहीं बनाते हैं (चित्र 2)। एहेर्माटिपिक प्रवालों का विश्‍व भर में वितरण होता है, लेकिन हेर्माटिपिक प्रवाल केवल उष्‍णकटिबंधीय स्‍थानों में पाए जाते हैं

Coral growth on entangled ghost nets in a tropical Indian Ocean atoll

Coral growth is subject to large-scale fluctuations induced by natural and anthropogenic effects (Buddemeier and Kinzie 1976). One critical extrinsic factor that can affect coral growth is pollution, which can be caused by nutrient enrichment or marine debris, especially derelict fishing gear that is indiscriminately dumped in the seas. For example, ghost nets that become trapped on healthy corals can hinder their growth, preventing access to sunlight and potentially smothering them, leading to the eventual death of the colony (Valderrama Ballesteros et al. 2018). Similarly, corals in contact with plastic have a significantly higher chance of contracting disease (Lamb et al. 2018). During an underwater survey in February 2021, we encountered a colony of Acropora cf. gemmifera in the Kavaratti Atoll in Lakshadweep (10.567509, 72.626564). A discarded nylon fishing net with a mesh size of approximately 40 mm had become entangled on this colony (Fig. 1). However, rather than growth being hindered, this colony overgrew the fishing net. Although coral overgrowing ghost nets has been reported previously (Valderrama Ballesteros et al. 2018), instances of corals successfully overgrowing nets are uncommon. The ability of A. cf. gemmifera to overgrow the net might be linked to the comparatively faster growth rate of acroporids (100–150 mm/year) versus massive corals (<50 mm/year) (Dullo 2005) and the absence of other stressors that might have interfered with its growth

Seven new distributional records of cryptobenthic reef fishes in Lakshadweep, India

Investigations on the diversity of cryptobenthic reef fishes resulted in observation of seven new geographic records for Lakshadweep waters, India: halfbarred goby Amblygobius semicinctus, target shrimpgoby Cryptocentrus strigilliceps, thread shrimpgoby Ctenogobiops mitodes, eye-bar goby Gnatholepis anjerensis, Miki's dwarfgoby Eviota mikiae, Erythrops goby Bryaninops erythrops, and Enneapterygius sp. Ctenogobiops mitodes is a new record to Indian waters. The genera Cryptocentrus and Bryaninops are reported from Lakshadweep for the first time. The observations were conducted in the lagoon and reef slope of Kavaratti Island, one of the 12 atolls of the Lakshadweep archipelago, from January–March 2021. The cryptobenthic reef fishes were observed and recorded through underwater photography and videography

Diversity and ecology of coral reef fishes

Coral reefs are mainly found in tropical regions of the world and cover approximately 284300 sq.km or 0.1% of the world oceans. However, they harbor about 25% of the marine fish fauna

New Distributional Records of Twelve Reef Fishes from Lakshadweep Waters, India

Previous fish faunal studies have indicated that 144 families, 432 genera, and 856 species are extant in the Lakshadweep archipelago. In the present study, 12 new records are added to the Lakshadweep fish diversity. The new records include Harlequin sweetlips (Plectorhinchus chaetodonoides), Three-stripe fusilier (Pterocaesio trilineata), Hector’s goby (Koumansetta hectori), Large toothed cardinalfish (Cheilodipterus macrodon), Coral hawkfish (Cirrhitichthys oxycephalus), One-spot wormfish (Gunnellichthys monostigma), Imposter fangblenny (Plagiotremus phenax), Disco blenny (Meiacanthus smithi), Maldives damselfish (Amblyglyphidodon indicus), Orange spotted spinefoot (Siganus guttatus), Spotfin burrfish (Chilomycterus reticulatus), and filament finned parrotfish (Scarus altipinnis). Plectorhinchus chaetodonoides, S. altipinnis and G. monostigma are new records to Indian fish fauna. The current study enhances the fish faunal records of Lakshadweep archipelago to being represented by 435 genera and 868 extant species, with Koumensetta, Gunnellichthys and Chilomycterus genera being recorded here for the first time. The observations were made through underwater visual census by SCUBA and snorkeling in the lagoon and fore-reef area of a single island, Kavaratti, one of the 12 atolls of Lakshadweep archipelago, from January to March 2021. Identifications of the new records were confirmed through photography and videography