coral reef insitu observation network
Assessing Real-Time Reef Health
OBJECTIVE
- Calculate the rate of sedimentation by using in-situ erected sediment trap.
- Calculate the rate of sediment transport by using physical parameters such as tide and current pattern.
- To study the relationships between sedimentation rate and health of the coral reef ecosystem.
STUDY AREA
Site Location
METHODOLOGY
Settlement Tripod Model
Contribution of invertebrates observed between inner and outer tiles
Comparison of coral recruitment rate* in different geographic regions
| REGION | PLATE AREA (cm2) | PERIOD (MONTHS) | MEAN # RECRUITS | SOURCE |
|---|---|---|---|---|
| Mid GBR | 225 | 6 | 95 | Fisk and Harriott (1990) |
| Barbados | 225 | 12 | 15 | Tomascik (1991) |
| SE Australia | 225 | 2 | 2.8 | Banks and Harriott (1996) |
| French Polynesia | 225 | 4 | 6.4 | Gleason (1996) |
| S GBR | 400 | 5 | 18 | Dunstan and Johnson (1998) |
| SE Australia | 225 | 6 | 4 | Harriott (1999) |
| Mid GBR | 122 | 2 | 193 | Hughes and Connell (1999) |
| Eliat (Red Sea) | 225 | 5-12 | 0.8 | Abelson (2005) |
| Gulf of Mannar | 225 | 2.5 | 0.4 | Current study |
Invertebrates observed in the recruitment/settlement plates of Kurusadai Island, Gulf of Mannar
Invertebrates observed in the recruitment/settlement plates exposed in the marine environment of Olaikudah, Palk Bay
Hydrodynamic Modelling
Summary
Coral reefs are one of the most diverse ecosystems in the world. They are home to about 25% of all marine life. Hence it acts as the “rainforests of the ocean”. In India, Palk Bay and Gulf of Mannar consist of a rich diversity of coral reef ecosystems located in South East coast of Tamil Nadu. Assessment of recruitment patterns of different invertebrates settled on the ceramic tiles (measuring 15 x 15 cm) carried out through microscopic examinations. These ceramic tiles are attached to the settlement tripod and exposed for four months at a depth of 3-5m underwater. The recruitment rate and availability of coral spat and its competitors (other invertebrates) were studied. The impact of circulation pattern (by using physical variables such as tide, wind and current) on these recruitment patterns of invertebrates was studied and analyzed. Moreover, the biophysical status of the selected study sites was found to be in correlation with the recruitment pattern in order to study the coastal ecosystem health.
The dynamics of the flow conditions help us to understand the characteristics of the coral spat on the tiles. The simulation of hydrodynamic model provided the flow conditions for different seasons. In the pre- and monsoon seasons, the circulation features are keenly understood and are vary from the minimal to maximum range of 0.12 - 0.16 m/s at Olaikudah Island and is similarly predicted in the range of 0.04 - 0.12m/s at Kurusadai Island of southern Tamil Nadu region.
The gradient in the flow filed is not very much significant to disturb the coral spat on the tiles, however minor impact can be noticed during the monsoonal period when compared to the pre-monsoonal period. Hence the model predictions about the components of currents showed the favor for the growth and health condition of coral reef in Kurusadai and Olaikudah Islands in the southern Tamil Nadu region.
The strong circulation features and high magnitude of the currents observed in the Olaikudah location as compared to the Kurusadai Island. It is directly impacts on the marine environment of biological species in the area. It is strongly supported to the marine biological studies which clearly revealed that the formation of coral spat on the tiles is not favorable at Olaikudah region in the Rameshwaram Island and more favorable in the Kurusadai Island.