Reef health research

ReefDoctor’s reef health research programme focuses on using standard survey techniques to provide reliable information on the current status of the reef’s biodiversity enclosing the Bay of Ranobe, and on artificial habitat experiments that might help the local community manage fishing resources.

Coral is the foundation of any reef system. The skeletons of corals formed over generations create the limestone structures on which the reef flourishes and grows, while the living corals covering the skeletons are an integral part of the reef’s complex ecosystem. Without the continued health of this part of the ecosystem, coral reefs begin to degrade affecting all the other organisms that make up life on the reef.

ReefDoctor’s current assessments are sited in three distinct regions within and around the southern portion of the Bay of Ranobe: patch reefs, spur and groove areas, and deep exterior reefs. At present, this encompasses ten sites, to provide comparative data over time.

Transect surveys
ReefDoctor’s transect surveys are designed to monitor animals and plants living in the area of the Bay of Ranobe. Through these surveys, ReefDoctor monitors plant life, corals, invertebrates and fish.

By quantifying and identifying life in this way, we are able to analyse the data collected and assess the health of the reef. Over time, this data can be used to monitor changes in coral and plant cover, coral health, and invertebrate and fish populations and diversity.

Sedimentation studies
The Bay of Ranobe is the outlet for two rivers in south-western Madagascar. In addition, deforestation inland, local agriculture and residential and tourism development along the coastline means that the risk of pollution and increased sedimentation within the Bay of Ranobe may be having an impact on the overall health of the reef.

To monitor this, ReefDoctor began a one year study of sedimentation within the Bay in 2005. This involved the collection and analysis of sediment from traps situated in our transect survey locations.

In this way, we are able to establish what sediment is present and in what quantities. Placing this alongside the data from transect surveys, it is possible to examine if the level of sedimentation is having an effect on the marine life in the area.

Coral studies
ReefDoctor’s coral studies focus on three areas: quantifying the larval supply of coral species through the use of settlement plates for analysis by microscope; monitoring the growth of young corals at selected sites within the Bay of Ranobe; and monitoring the annual coral spawning.

Seagrass surveys
The lagoon of the Bay of Ranobe is comparatively shallow and home to large areas of seagrass meadows. The function of such meadows is to reduce the impact of waves on the seabed, to help filter sediment from the water, to provide feeding and shelter for many juvenile reef fish and to stabilise bottom sediment. They may also act as a nutrient sink by filtering nutrients and chemicals from the marine environment.

ReefDoctor is currently developing a programme of seagrass meadow mapping and assessment for the Bay of Ranobe. This will enable us to establish the current extent and health of the meadows and, over time, to assess the impact of sedimentation, pollution and local practises such as beach seine netting on the juvenile fish grounds (fishing by dragging nets through the seagrass on the seabed).

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