Biological survey – Manta Reef N+1
Biological survey report – Manta Reef project at N+1
Coral reef ecosystems, sheltering more than a quarter of the world’s marine biodiversity are, nowadays, threatened in the world’s oceans (Epstein et al, 2001, 2003. Wilkinson 2002; Soong et al. 2003). Different causes are highlighted by region. It can be a pronounced climate event such as El Niño, the result of human activities such as pollution, construction of infrastructure on coastlines, destructive fishing techniques etc …, Therefore the increasing concentration of greenhouse gases in the atmosphere leading to a temperature rise in water and a physico-chemical balance change of carbonates in the ocean (Hoegh-Guldberg 1999 ; Nyström et al. 2000; McClanahan et al 2002. Hughes et al. 2003; Sheppard 2003; Bellwood et al 2004;. Hoegh-Guldberg et al 2007). Indonesia is located in the “Coral Triangle” that houses an outstanding marine diversity. This area is often called the marine Amazon forest by its biological richness. However, some illegal practices, but still in force, are destructive to the reef biodiversity. Fishing with dynamite and cyanide fishing generate large damage (Jones et al. 1999), with irreversible consequences for marine ecosystems. Reef restoration programs as well as awareness and involvement of local communities related are essential activities to develop for future generations.
The active reef restoration is one of the approaches to the conservation of these ecosystems (Rinkevich 2005).
Objectives of the study
This paper presents the results of the Manta Reef project’s biological survey. It is a coral reef restoration program with implantation of three-dimensional structures were twenty-nine species of hard corals were transplanted, about 1,200 cuttings (November 2014). Corals are harvested on dive sites nearby from mother’s colonies broken by boat anchors, diving fins, etc. On this unstable substrate (coral soup due to dynamite fishing) they are condemned to die.
Genus Acropora : Acropora fomosa, Acropora horrida, Acropora azurea, Acropora bushyensis, Acropora carduus, Acropora milepora, Acropora divaricata, Acropora efforescens, Acropora florida, Acropora forskali, Acropora grandis, Acropora kimbeensis, Acropora loripes, Acropora microphthalma, Acropora nana, Acropora nasuta, Acropora nobilis, Acropora robusta, Acropora tricolor, Acropora variabilis.
Genus Anacropora : Anacropora forbesi
Genus Montipora : Montipora capricornis, Montipora danae, Montipora digitata, Montipora foliosa, Montipora spongodes.
Genus Hydnophora : Hydnophora Pilosa
Genus Seriatopora : Seriatopora hystrix
Genus Millepora : Millepora sp (not considered as an hard coral with limestone skeleton. Only one species in this genus).
The first biological survey was conducted prior to the implementation of structures to form an inventory of the fish fauna of the site. One year after the implementation of the project, a second survey was done.
The method of “fish belt transect”, which is to identify all the fish along a 20m long by 4m wide transect and the entire water column (the project being in a shallow area) was selected for this study. It is used, among others, in the following programs: Australian Marine Institute of Marine Science Long-term Monitoring Program of the Great Barrier Reef; Global Reef Monitoring Network.
The readings will be once a year, at the same time to limit the temporal variability due to reproduction and migration. This method is used to determine the abundance and diversity of fish frequenting our study areas. These statements were made by Martin Colognoli on 07.10.2013 and 09.25.2014.
Area and study site
This project was carried out over an area of sand and coral debris due to dynamite fishing on the coast of Gili Trawangan. Indonesia (Latitude: -8.359281 | Longitude: 116.04234).
The control site and the study site both have very similar characteristics in terms of substrate, depth (2-6m) of exposure, distance from the coast and of currents. They are of similar size (approximately 650m² each). The 2013 statement corresponds to the monitoring of “initial state” that is to say before the implementation of restoration structures. 2014 statement is the record N + 1 (one year after the project was done).
Résults and Discussion
In Figure 3, there is an abundance twice as large as numbers of species at the study site after one year of experience. This increase in species richness is due to the implementation of diverse habitats, from the three-dimensional structures installed (supports grills and lanterns) and by corals transplanted them. Indeed, the corals are a source of habitat and / or food for many species of fish and invertebrates.
The statement of July 2013 shows that both sites (control and study) were similar in terms of specific fish wealth (t-test, p = 0.9131) and abundance (t-test, p = 0.6985). These results are logical because they reflect the similarity of the two areas before the establishment of structures and corals.
The mean comparison test (Aspin-Welch) between the control site and the study site for the 2014 survey shows a significant difference in species richness (t-test, p = 0.01996).
Moreover the confidence intervals do not overlap at risk of 5%.
Control 2014 2.697347 11.302653
Site 2014 15.08663 50.91337
On the abundance, the average comparison test does not attest to a significant difference (t-test, p = 0.1248), despite the difference in the results (Table 1). This lack of significance may be due to the weakness of the sample (n = 3 transects). The size of areas limiting the possibilities of setting up more transects, affect the significance of the statistical tests (More the sampling is small, more the differences should be large to attest to the significance).
Abundance and composition of the population.
It is clear that the abundance of fish is significantly more important in the study site after a year of experience.
A family dominates the composition; it is the Pomacentridae (lady fish). Some species of this family, such as Chromis viridis, particularly fond of branching corals, where they shelter them in number. It is part of bio-indicator species of the reef health.
Even apart from this family, we see that the number of fish is greater on the study site in 2014 relative to the site control of the same year, as well as compared to 2013 results.
Figure 6 shows the composition of each site every year except in terms of fish Pomacentridae families (which by their number make it difficult to read graph). It is found that the control sites in 2013 and 2014 as well as the study site in 2013 (before the establishment of structures) are similar in composition of the fish community present respectively on each site. While the statement on the study site in 2014 shows a rich family assembly.
In summary, the conclusion at the end of one year is:
Study site 2013 / 2014:
- Increased in number of species 195.5%
- Increased number of families 133.3%
- Increased in the average number of individuals per 100m² of 1501.1%
In 2014 there was a relationship between the control site and the study site of:
- 238.9% by number of species
- 153.8% by number of families
- 2483.6% in average number of individuals per 100m²
The results of this first year of experimentation is positive, the aim being to restore the destroyed reef areas. Indeed the introduction of three-dimensional structures covered by corals “cutting” allowed a resurgence of abundance and biodiversity of fish after one year. The presence of bio-indicator species like corallivore fish, Chaetodon melannotus, or planctonophage fish (but using healthy branching corals as shelter) as Chromis viridis is also encouraging. The next survey will give us information on the development of this area as well as the durability of the structures. Monitoring of a perfectly healthy reef area and having the same geographic features, topological, and bathymetric courantologique would also be interesting to estimate the distance to go to reach this condition on the restored areas.
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