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Institute for Coastal and Marine Research

 

EBSA overview  |  Delineation |  Proposed description

 

 

EBSA overview

Secret Reef is a newly discovered biogenic coral reef structure that is outside of the trawl footprint on the shelf edge of the South African south coast, and high in live coral cover. Such features are relatively rare in the area. The EBSA spans this reef and a slightly broader area that covers a relatively large depth range (‑150 to -800 m) despite its relatively small size. Notably, it contains dense communities of fragile and sensitive coral and bryozoan species. Three of the five ecosystem types represented in the EBSA have been assessed to be Vulnerable, but are mostly in good ecological condition. Further research is encouraged for this site, particularly for Secret Reef itself.

 

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Delineation

Open or collapse the legend as a sidebar by clicking the icon in the top left corner of the map. In the legend you can turn on/off the old/new extents of the EBSA. You can zoom in/out using the mouse or the +/- buttons on the map, and click on the features for more information.

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Proposed EBSA description

NOTE: Read this here, or download the Word document on the right sidebar.

Summary

Secret Reef is a newly discovered biogenic coral reef structure that is outside of the trawl footprint on the shelf edge of the South African south coast, and high in live coral cover. Such features are relatively rare in the area. The EBSA spans this reef and a slightly broader area that covers a relatively large depth range (‑150 to -800 m) despite its relatively small size. Notably, it contains dense communities of fragile and sensitive coral and bryozoan species. Three of the five ecosystem types represented in the EBSA have been assessed to be Vulnerable, but are mostly in good ecological condition. Further research is encouraged for this site, particularly for Secret Reef itself.

 

Introduction

bathyal zones of the South African south coast, in the Agulhas Current. Given its position, despite being a relatively small EBSA, it spans a broad depth range of -150 to -800 m. The features within the EBSA are largely benthic, and include fragile and sensitive corals and byrozoans. The bulk of the ecosystem types represented in the EBSA are Vulnerable, but in good ecological condition (Sink et al., 2012). The Secret Reef EBSA also had high selection frequency in a national systematic conservation plan (Sink et al., 2011; SANBI unpublished results in analysis for Madjiedt et al., 2013), suggesting that it is an important area in which to meet biodiversity targets.

 

The reason this site was not included among the initial set of EBSAs proposed for the Southern Indian Ocean is because this site was not yet discovered, and thus the information was not available at the Southern Indian Ocean Regional Workshop to Facilitate the Description of Ecologically or Biologically Significant Marine Areas (UNEP/CBD/RW/EBSA/SIO/1/4) in 2013. Because this is a discrete site that is centred around the reef and its associated fragile and sensitive species, it is presented as a Type 1 EBSA (sensu Johnson et al. 2018).

 

Description of the location

EBSA Region

Southern Indian Ocean

 

Location

Secret Reef lies on the Grue Bank, about 100 km offshore of Knysna, approximately half way along the South African south coast in the Agulhas Current. The EBSA falls entirely within South Africa’s EEZ on the shelf edge and upper bathyal.

 

Feature description of the proposed area

Secret Reef is a newly discovered biogenic coral reef structure on the shelf edge and upper bathyal area (Sink 2016), and thus the EBSA is most important for benthic features, although the overlying water column is also relevant. It includes threatened benthic habitats and vulnerable, sensitive and vulnerable species, such as: scleractinian corals, stylasterine corals, bryozoans, molluscs, and crabs sampled in the focus area (Sink 2016). The habitats include confirmed hard shelf edge, and biogenic coral mound types, the bulk of which have been assessed as Vulnerable, but still in good ecological condition (Sink et al., 2012). Because this area is so recently discovered, there is very little information available about the site, other than the data that were collected on the cruise when the reef was found (Sink 2016).

 

Feature condition and future outlook of the proposed area

Overall, Secret Reef is currently in good ecological condition, however, there are portions of it that are in poor ecological condition. The primary pressures in the area are from fishing for large pelagic fish, and demersal and pelagic sharks, with some influence from shipping and other fishing industries to a lesser degree. The reef itself is outside of the trawl footprint so the site is high in live coral cover (Sink 2016). Research was recently conducted in the area as part of a larger programme to survey South Africa’s marine environment (Sink 2016). No future research is currently planned, although has been strongly recommended (Sink 2016).

 

References

Johnson, D.E., Barrio Froján, C., Turner, P.J., Weaver, P., Gunn, V., Dunn, D.C., Halpin, P., Bax, N.J., Dunstan, P.K., 2018. Reviewing the EBSA process: Improving on success. Marine Policy 88, 75-85.

Majiedt, P., Holness, S., Sink, K., Oosthuizen, A., Chadwick, P. 2013. Systematic Marine Biodiversity Plan for the West Coast of South Africa. South African National Biodiversity Institute, Cape Town.

Sink, K.J., Attwood, C.G., Lombard, A.T., Grantham, H., Leslie, R., Samaai, T., Kerwath, S., Majiedt, P., Fairweather, T., Hutchings, L., van der Lingen, C., Atkinson, L.J., Wilkinson, S., Holness, S., Wolf, T. 2011. Spatial planning to identify focus areas for offshore biodiversity protection in South Africa. Unpublished Report. Cape Town: South African National Biodiversity Institute.

Sink, K., Holness, S., Harris, L., Majiedt, P., Atkinson, L., Robinson, T., Kirkman, S., Hutchings, L., Leslie, R., Lamberth, S., Kerwath, S., von der Heyden, S., Lombard, A., Attwood, C., Branch, G., Fairweather, T., Taljaard, S., Weerts, S., Cowley, P., Awad, A., Halpern, B., Grantham, H., Wolf, T. 2012. National Biodiversity Assessment 2011: Technical Report. Volume 4: Marine and Coastal Component. South African National Biodiversity Institute, Pretoria.

Sink, K. 2016. Deep Secrets: the outer shelf and slope ecosystems of South Africa. Cruise Report: ALG 230 – ACEP_DSC.

 

Other relevant website address or attached documents

Summary of habitat types and threat status for the Secret Reef EBSA. Data from Sink et al. (2012).

Threat Status

Ecosystem Type

Area km2

Area (%)

Vulnerable

Agulhas Hard Outer Shelf

105.9

7%

 

Agulhas Hard Shelf Edge

521.4

33%

 

Agulhas Sandy Shelf Edge

365.5

23%

Vulnerable Total

 

992.8

64%

Least Threatened

Agulhas Sandy Outer Shelf

277.1

18%

 

Southwest Indian Upper Bathyal

288.9

19%

Least Threatened Total

 

566.0

36%

Grand Total

 

1,558.9

100%

 

Status of submission

Area to be submitted to the Conference of the Parties for acknowledgement of meeting EBSA criteria once review process is finalized.

 

COP Decision

Not yet submitted.

 

Assessment of the area against CBD EBSA Criteria

C1: Uniqueness or rarity Medium
 
Justification
The coral mound is a relatively rare feature in the broader area. It also had high selection frequency in a national systematic conservation plan (Sink et al., 2011; SANBI unpublished results in analysis for Madjiedt et al., 2013), suggesting that it is an important area in which biodiversity targets need to be met.
 
 
C2: Special importance for life-history stages of species Data deficient
 
Justification

Further research is required to determine if this site supports important life-history stages of species.

 
 
C3: Importance for threatened, endangered or declining species and/or habitats Low
 
Justification

The site includes portions of three ecosystem types that have been assessed as Vulnerable (Sink et al., 2012), namely Agulhas Hard Outer Shelf, Agulhas Hard Shelf Edge and Agulhas Sandy Shelf Edge. It is not yet known whether or not this site is important for threatened or declining species, and this would require more research in the area.

 
 
C4: Vulnerability, fragility, sensitivity, or slow recovery High
 
Justification
Secret Reef is a biogenic coral mound that has fragile scleractinian corals, stylasterine corals, and bryozoans (Sink 2016).
 
 
C5: Biological productivity Low
 
Justification

Time-averaged MODIS Aqua data on chlorophyll concentration (NASA Giovanni Portal: https://giovanni.gsfc.nasa.gov) shows that productivity inside Secret Reef is not higher compared to that of the surrounding area.

 
 
C6: Biological diversity Medium
 
Justification

Because the area is outside of the trawl footprint, reef diversity inside the EBSA is relatively higher than that in the surrounding area (Sink 2016).

 
 
C7: Naturalness Medium
 
Justification
 
Secret Reef itself is outside of the trawl footprint, so this feature itself is close to pristine and high in live coral cover (Sink 2016). The broader EBSA focus area is mostly in good ecological condition based on a national assessment of cumulative pressures on the marine environment, although some areas (21%) inside the EBSA are in poor ecological condition and a similar area (20%) is in fair condition (Sink et al., 2012).

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