Enhanced coral larval settlement and coral transplantation as means of promoting coral replenishment in Tanzania

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University of Dar es Salaam
Coral reefs play an important role in the socio-economy of the coastal communities in Tanzania. However, the ongoing degradation of coral reefs caused by anthropogenic disturbances and by natural processes threatens the existence and contribution of coral reef ecosystems. In order to contribute knowledge towards sustainable management of coral reefs, investigations were conducted: (a) on seasonality in seawater temperature, macroalgal abundance and sedimentation rates; (b) on coral larval temporal settlement patterns and how settlement could be enhanced using artificial plates and; (c) on the survival and growth of transplanted coral fragments from different species on degraded reef habitats and on artificial substrates. Results have confirmed the existence of seasonal patterns in seawater temperature, macroalgal abundance, sedimentation rate, and coral larval settlement. Elevated seawater temperature in March-June 1998 corresponded with bleaching and mass mortality of corals. The coral settlement density of 95.5 spats per square meter in three months (m’2 3-mo1) in 1995 decreased after coral bleaching event to 36.4 m'2 3-mo1 and 38.5 m'2 3-mo'1 in 1998/99 and 1999/2000, respectively. The taxa composition of settled coral larval was also influenced by the bleaching event. Settlement density was higher during the northeast monsoon (October-March) period. Survival after settlement appeared to exert a major influence on coral recruitment. Coral transplantation studies revealed that fragments as small as 0.5-5 cm could be cultured. Lesions had no negative effects on transplanted fragments, nor on donor colonies. Fresh cement mixture used as attachment medium was lethal to coral tissues, thus tissue contact must be avoided. The survival and growth of larger coral fragments was higher than that of smaller fragments. Higher survival and growth rates were observed when fragments were cemented on support structures than when unattached. Acroporids, specifically Acropora nobilis, A. austera, A. forskali and A. tenuis, were identified as the most suitable species for increasing coral cover under good conditions (in 1999-2000), though these species were the most susceptible during the 1998 coral bleaching event. The enhancement of the coral reef environment by the use of artificial settlement plates and fragment- support structures in various ways is discussed.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF QH541.5.C7T34M8)
Transplantation, Promoting
Muhando, C.A (2003) Enhanced coral larval settlement and coral transplantation as means of promoting coral replenishment in Tanzania, Doctoral dissertation, University of Dar es Salaam. Dar es Salaam.