SDMRI Research Publication No. 9,41 - 48, 2005 Grow mangroves for protecting cord reefs! K, Kathiresan* and N. Rajendran Centre of Advanced Study in Marine Biology, Annarnalai University, Parangipettaa - 608 502, India. "[email protected]; cdl-aucasrn~sanchamet.in Abstract Mangraves do act as a Biofdter' between land and sea, and they protect the coral reef ecosystems. The fishes of commercial importance increase with the area of mangroves. The total area of mangroves in India is 4,482 sq.km. Ofwhich, about 59% are found on the east coast, 23% on the west coast and the remaining 18% on the Andaman and Nicobar Islands. The mangroves in India comprise of 69 species. Total faunal species are high in Sundarbans (14345 and in Andman and Nicobar Islands (914). The east coast and ARdman and Nicobar Islands are richer in biodiversity than the west coast. Some species that inhabit mangrove ecosystems warrant intensive care for immediate conservation; the noteworthy species 1s Pemphis a&dulu (Lythraceae) restricted to the coral sand on the open sea-face. Having an ultunate goal of providing livelihood and ecological securities to coastal people, Govt. of India has taken si@icant efforts. This paper h~ghlightsan urgency of developing the rnanpoves in the coral coasts for protection and conservation of the reef ecosystems. Introduction VaImes of mangroves In pmtecthg corals Mangrove forests are among the Mangroves may play role in world's most productive ecosystems. alleviation of stressoss to coral They enrich coastal biodiversity, yield reef ecosystems. The stressors are commercial forest products, protect sedimentation, storm and wave energy, coastlines, and support coastal fisheries. atmospheric temperature, CO, Jevel, There may be no ather pupof plants ultraviolet and solar radiation (Mc Allister with such highly developed adaptations and Ansula, 1993; Bakus, 1994). to extreme conditions of high salinity, Mangrove forests act as filters extreme tides, strong winds, high between the land and coral reef. Tney temperatures and muddy, anaerobic soils prevent soil erosion and also trap soil [Kathiresan and Bingham, 200 1). The particles. They also filter muddy runoff mangroves grow normalIy in the muddy from rain, and gradually let freshwater intertidal regions of tropical and rnyl with seawater. All these processes subtropical coasts. They do occur in help in supplying the clean, saline and habitats other than muddy ones, such as nutrient-rich water, which are favourable coral coast. In these areas, the mangroves for the coral reef ecosystems.. Cutting grow on peat, which is derived from down mangroves may damage nearby decayed vegetation (Kathiresan, 2003). coral reefs by permitting mud or silt to Value of the mangroves in protection and settle on corals and freshwater to spread conservation of the card reef ecosystems onto the reef (Fig. 1). Further, mangrove has not received due attention. This forests may help protect coast and nearby aspect is highlighted in this paper along reefs from the fiery effects of storms and with the present status, challenges faced typhoons. and strategies followed for conservation The mangroves serve as nursery and management of mangroves in India. ground for many species of coral reef Proceedings of the National Seminar on Reef Ecosystem Remediation and erodmd nd ~~dlrn*nadon Fig. 1.Influence of mangroves and deforestation on seaweed. coral reefs and seagrass ecosystems fishes, For example, the mangroves of Status of mangroves on coral coast Southwest Lagoon, New ~a~edoniaare Information on mangroves near known to hold 262 fish species, including coral formations in India is largely the juveniles of 30% of the reef lacking. In Minicoy island of species (Kathiresan and Bingham, 200 I). hkshadweep has small patches of the Mangrove leaves provide a source of mangrove Bmguiem pamj7om (Untawale energy for small animals, which in turn sand Jagtap, 1984). Pmphis acidula is a feed shrimps and fishes. Mangroves also mangrove species restricted to the coral provide habitats for oysters, mussels and sand on the open sea face. his species cockles (Mc Allister and Ansula, 1993; occurs only along the coral coasts at Sakus, 1994). Manoli, Manoliputti, Poomarichan Mangroves remove CO, through islands, and Hare islands of Gulf of photosynthesis from atmosphere and Mannat of Tmik Nadu. prevent methane from soil, thereby reducing the problems of green house Issues af mangroves on codcoast gases and temperature rise. The Mangrove substrates along the mangroves fur CO, per unit area, greater coral coasts are poor in humus content, than the phytoplankton did in the we11 aerated with high pH with no tropical oceans (Kathiresan and formation of acid sulphate soil. The soil Bingham,- 2001). is always aerated because of the porous of Mangroves exhibit higher tolerance nature the substratum that blocks the and How to sunlight and UV- B than other iron sulphur cycles. the hdophytes (Kathiresan and Moorthy, mangroves are specifically adapted to the on 1993). In fact, seedlings of Rhizophom coral coast? Thie deserves studies exposed to low UV-B radiation (equivalent anatomy and physiology of the plants. to 10% of ozone depletion) show an Growth of trees is slow and closed increase of 45% in net photosynthetic canopy is not famed because of the poar rates. However, under high W-B (40%), levels of soil nutrients rather than any a 59% drop of the photosynthesis occurs other factors, but they compete (Mourthy and Kathiresan, 1997 a, b). Thus favourably with other plant species, the mangroves mitigate the vulnerable because of their salinity tolerance. Hn effect of W at lower intensity. general, temperature favours growth but SDMH Research Publication No. 9, 4 1 - 48,2005 may cause death due to increased are found along the east coast (Bay of evapotranspiration and very high soil BengaI), 23% on the west coast (Arabian salinity, if rain fails. Violent winds and sea) and the remaining 18% on the Bay typhoons are a cause of dwafing and Islands (Andaman and Nicobar Islands in change of shape of the trees, because Bay of Bengd) (Fig. 2). The apical buds are often destroyed. There are three major types of mangroves show bushy rather than coastal settings on which mangroves in elongated tree shape (Mc Allister and India exist and they are (I) deltaic, (11) Ansula, 1993; Bakus, 1994). bac kwater-estuarine and (111) insular On the cord sands, prppagules do types. The deltaic mangroves occur along not easily take root, and sometimes the east coast (Bay of Bengal] where the over-washed during high tide [Bakus, mighty rivers (Ganga, Bsahmaputra, 1994). Seeds and propagules of Mahanadhi, Krishna, Godavari and mangroves may be Iast to the sea before Cauvery) make the deltas. These deltas taking roots, if the sea level rise occurs are nutrient-rich alluvial soil and hence in the Iow lying coral coast. In the Cora1 the mangroves are luxuriant. The Reefs of our Country, the sedimentation backwater-estuarine type of rnangroves is a common issue by pollution. followed that exists in the west coast (Arabian sea) is Mangrove clearing the important issue is characterized by typical funnel-shaped of in the Gulf of Mannar and the Gulf estuaries of major rivers (Indus, Kachchh. artificial planting of Therefore, Narmada, Tapti with delta formation is the propagules is highly necessary along almost absent) or backwaters, creeks, and the coral coasts. neritic inIets. The insular mangroves are Present status of mangroves in India present in the Bay Islands, where many Extent of mangroves tidal estuaries, small rivers, neritic islets India has a total maof 4,482 h2 and lagoons support a rich mangrove under mangroves (Table 1). About 59% Table 1: Extent of Mangroves, floral and faunal species in India (Kathiresan, 2002) State/ Union Area No. of No. of Territory sq. km' mangrove faunal (% of totd) species species East coast: West Bengal Orissa hnd hta PrEtdesh Tam11Nadu Bag Islands: Andaman & Nicobar West coast: Ciuj arat Maharashba & Goa Kamatdca Kcrda Pondieherry Total *Data for area of rnmgoves from FSI (Forest survey of India), 2001 Proceedings of the Nation~llSeminar on 'Reef Ecosystem Remediation Fig. 2. Mangrove areas of India Floral and Faunal Resources Regarding prawns / shrimps, there Mangrove species have been are a total of 53 species in Indian counted as the plant species that exist mangroves, of which 36 (68%) in the east within the limit of saline tidal water flow coast and 22 (42%) in the west coast. and unstable muddy substrates. There are 91 crab species in Indian According to this definition, the mangroves mangroves, of which 67 (74%) in the east in India comprise of 69 species coast and 13 (14%) in the west coast excluding salt -marshes and other (Table 2). Similarly, there are higher associate species, under 42 genera and numbers sf molluscan and fin-fish 27 families. Of these, 63 species (41 species along the east coast than on the genera under 27 families) are present on west coast. the east coast; 37 species (25 'genera and Correlation between area of habitats 16 families) on the west coast; and 44 and biodlversit ies species (28genera under 20 families) on Fig. 3 shows that there is a the Bay Islands (Table 1). The East coast significant positive correlation between has 9 1% of mangrove species and the extent of mangroves and faunal species has west coast 53%. diversity (r = 0.68),extent of mangroves The number of mangrove- and total species diversity (r = 0.68), inhabiting faunal species was 109 1 (74% extent of mangroves and crab species ef total) in the east coast, and 344 (23% diversity (r = 0.7 I), extent of mangroves of total) in the west coast (Table 1). The and shrimp species diversity (r = 0.88), total number of mangrove and faunal as well as between no. of mangrove species was 1538, of which 1154 (75% of species and no.