Sustainable Ocean Resources Network

Abstract

 

Man-made structures may provide possible interfaces for marine organisms to settle in locations that would never be otherwise successfully colonized in unstable substrates like sand, mud, or rubble. Settling of pioneer communities may attract more communities after a certain period of time ultimately making spectacular ecosystems.

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Present study was conducted between September 2013 and September 2014 in order to monitor the status of the environment of the Hambantota port. Underwater Visual Senses (UVS) were carried out through diving and snorkeling. Belt transect method was used to assess the species composition. Minimum of five quadrate samples were obtained randomly along the 50 m transect. For immobile species, each organism encountered were recorded. Underwater video transects and photo-quadrates were obtained along the line transect for permanent visual record of the data for mobile species.

The remarkable finding of the study is that since the construction of breakwaters, a coral reef has developed along the west breakwater and west bank. Same time, a diverse communities of reef fishes and other invertebrates were also colonized within the developing reefs. One of the remarkable observation is that majority of the fish species recorded were of reef associates. Reef fish assemblage included; 7 species of surgeonfishes (Acanthuridae), Ambasis sp (Ambassidae), 3 species of cardinal fishes (Apogonidae), Arius sp (Ariidae), Crossosalarias macrospilus and Entomacrodus decussatus (Blenniidae), Pterocaesio pisang (Caesionidae), Caranx sp. and Carangoides chrysophrys (Carangidae), 10 species of butterfly and bannerfishes (Chaetodontidae), 3 species of milkfishes (Chanidae), Paracirrhites forsteri (Cirrhitidae), Fistularia commersonii (Fistulariidae), 3 species of gobies (Gobiidae), Plectorhinchus obscurum (Haemulidae), Sargocentron microstoma and Neoniphon aurolineatus (Holocentridae), Labroides dimidiatus and Thalassoma lunare (Labridae), Leiognathus equulus (Leiognathidae), Lutjanus bengalensis (Lutjnidae), Monodactylus argenteus (Monodactylidae), Mugil cephalus and Valamugil buchnani (Mugilidae), Parupeneus indicus (Mullidae), Gymnothorax favagineus (Muraenidae), 9 species of angel, sergeant and damsel fishes (Pomacanthidae), Scarus ghobban (Scaridae), Scatopaghus argus (Scatopigidae), Pterois volitans (Scorpinaedae), 3 species of seabass and groupers (Serranidae), 4 species of siganids (Siganidae), Sphyreana queni (Sphyraenidae), Zanclus cornutus (Zanclidae). In addition, 14 species of gastropods, 3 species of crustaceans, 7 species of crabs, 3 species of bivalves, two species of sponges and 2 feather stars. The structures were also covered in barnacles and what is believed to be the beginnings of soft coral.

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Although the abundance and richness of associated epifauna and fishes on mature man-made structures may approach those of natural rocky reefs, the composition may still differ from those of nearby natural environments. Additionally, the communities of epifauna and algae on man-made structures may easily removed by natural disturbances like cyclones and storms due to smooth texture of concrete and boulders decreases the adhesion of these epifauna. However, it was observed from this study that man-made structure such as breakwaters with developing corals can support coral reef fishes same as natural reefs. Further, mature breakwaters in appropriate locations could provide colonization habitats for marine organisms (especially marine epi-fauna) that need solid surfaces for attachment. Man-made structures can generate possible interfaces for marine organisms to settle in locations that would never be otherwise successfully colonized due to unstable substrates like sand, mud, and rubble. Coral communities on man-made structures have been suggested for possible use in coral restoration or as possible surrogates for lost habitats of coral reef fishes.