Change the world

Institute for Coastal and Marine Research

 

EBSA overview  |  Delineation |  Summary of description updates  | Revised description

Submit feedback on the delineation and description  |  OBIS biodiversity data
 

 

EBSA overview

The outer margin along the southern tip of the Agulhas Bank represents a dynamic offshore area with high productivity and high pelagic and benthic habitat heterogeneity. The Agulhas and Southern Benguela ecoregions meet at this point, and sporadic shelf-edge upwelling enhances the productivity along the outer margin. The area is recognized as a spawning area for sardine, anchovy, horse mackerel and hake, and this apex area of the Agulhas Bank is recognized as a critical area for retention of spawning products. Eddies in this area help recirculate water inshore and link important nursery areas with spawning habitat on the shelf edge. The EBSA focus area also contains the Mallory, Shackleton and Natal Seamounts and the Mallory Trough Segment of the Agulhas-Falkland Fracture Zone. This area was identified as a priority through a national spatial plan because of high habitat diversity. Since the original description, the boundary of this EBSA has been refined to better represent the underlying EBSA features. Although a recent cruise surveyed two sites at the northern edge of the EBSA, deteriorating weather conditions limited operations; further research and in situ surveys of the unexplored hard shelf edge and seamounts are recommended in this area.

[Top]

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.

 

[Top]

Summary of updates and revisions to the EBSA description

Boundary, name, description and criteria ranks all updated.

[Top]

Revised EBSA description

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

 

General Information

Summary

The outer margin along the southern tip of the Agulhas Bank represents a dynamic offshore area with high productivity and high pelagic and benthic habitat heterogeneity. The Agulhas and Southern Benguela ecoregions meet at this point, and sporadic shelf-edge upwelling enhances the productivity along the outer margin. The area is recognized as a spawning area for sardine, anchovy, horse mackerel and hake, and this apex area of the Agulhas Bank is recognized as a critical area for retention of spawning products. Eddies in this area help recirculate water inshore and link important nursery areas with spawning habitat on the shelf edge. The EBSA focus area also contains the Mallory, Shackleton and Natal Seamounts and the Mallory Trough Segment of the Agulhas-Falkland Fracture Zone. This area was identified as a priority through a national spatial plan because of high habitat diversity. Since the original description, the boundary of this EBSA has been refined to better represent the underlying EBSA features. Although a recent cruise surveyed two sites at the northern edge of the EBSA, deteriorating weather conditions limited operations; further research and in situ surveys of the unexplored hard shelf edge and seamounts are recommended in this area.

 

Introduction of the area

The Agulhas Slope and Seamounts includes the outer margin along the southern tip of the Agulhas Bank in South Africa. It is a dynamic offshore area with high pelagic and benthic habitat heterogeneity. The area includes outer shelf, shelf edge, slope and seamount habitats, and a trough as part of the Agulhas-Falkland Fracture Zone that has a slope as steep as 20° in some places (De Wet 2012). The Agulhas and Southern Benguela ecoregions (Sink et al., 2012) meet at this point, and sporadic shelf edge upwelling enhances the productivity along the outer margin (Lagabrielle, 2009, Roberson et al., 2017). The area is recognized as a spawning area for sardine, anchovy, horse mackerel and hake, and this apex of the Agulhas Bank is recognized as a critical area for retention of spawning products (Hutchings et al., 2002). Eddies in this area help recirculate water inshore and link important nursery areas with spawning habitat on the shelf edge. Leatherback turtles also frequent these seamounts along their migrations (Harris et al., 2018). This area was identified as a priority through a national plan to identify focus areas for offshore protection (Sink et al., 2011) because it has relatively high habitat diversity and can meet multiple benthic and pelagic habitat conservation targets in a small area.

 

Description of the location

EBSA Region

Southern Indian Ocean

 

Description of location

The EBSA focus area is at the apex of the Agulhas Bank at the southern tip of the continental shelf edge off southern Africa. It lies directly south of Mossel Bay in the Agulhas-Falkland Fracture Zone, and is entirely within South Africa’s EEZ. It contains the Mallory, Shackleton and Natal Seamounts, and Mallory Trough.

 

Geo-Location

SIO_2_EBSA.geojson

 

Area Details

Feature description of the area

The area includes benthic and pelagic features, including shelf edge, slope and seamounts, shelf-edge driven upwelling, and fragile and sensitive habitat-forming species. Habitat diversity is thus particularly high, with four pelagic habitat types and ten benthic habitats occurring in this dynamic area. It consequently supports numerous ecological processes, such as spawning and foraging, and comprises a rich diversity of both resident (e.g., benthic gorgonians) and transient (e.g., migrating leatherbacks) species. Two sites at the northern edge of the EBSA were recently surveyed; however, deteriorating weather conditions limited research operations (Sink 2016). Nevertheless, the sites were reported to be less muddy than expected, and samples of yellow scleractinian coral, stylasterine corals and bryozoans were collected (Sink 2016).

The delineation of this EBSA was refined since its first description, and although is now a very different shape, the area is approximately the same. The revision was based on high selection frequency of sites in the two systematic biodiversity plans covering the area, tighter alignment to the benthic slope, seamount and trough topography, new focus areas for MPA expansion in South Africa, presence of fragile and sensitive habitat-forming species, and presence of threatened benthic ecosystem types. Effectively, these new data helped to improve the precision of the EBSA boundary so that it better reflects the underlying features.

 

Feature conditions and future outlook of the proposed area

The shelf edge, trough and seamounts have not been sampled, although in-situ research is recommended in this area. Nevertheless, there are various fisheries operating in the area, but some of the hard grounds represented in the EBSA are outside of the trawl footprint. Broadly speaking, there is relatively little pressure in this area at present, and the ecosystem types are in good condition.

 

References

De Wet, W. 2012. Bathymetry of the South African Continental Shelf. MSc dissertation. University of Cape Town, South Africa.

Harris, L.R., Nel, R., Oosthuizen, H., Meyer, M., Kotze, D., Anders, D., McCue, S., Bachoo, S. 2018. Managing conflicts between economic activities and threatened migratory marine species towards creating a multi-objective blue economy. Conservation Biology, 32, 411-423.

Hutchings, L., Beckley, L.E., Griffiths, M.H., Roberts, M.J., Sundby, S., van der Lingen, C. 2002. Spawning on the edge: spawning grounds and nursery areas around the southern African coastline. Marine and Freshwater Research, 53: 307-318.

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.

Lagabrielle, E. 2009. Preliminary report: National Pelagic Bioregionalisation of South Africa. Cape Town: South African National Biodiversity Institute.

Lutjeharms, J.R.E., Cooper, J., Roberts, M. 2000. Upwelling at the inshore edge of the Agulhas Current. Continental Shelf Research, 20: 737 – 761.

Roberson, L.A., Lagabrielle, E., Lombard, A.T., Sink, K., Livingstone, T., Grantham, H., Harris, J.M. 2017. Pelagic bioregionalisation using open-access data for better planning of marine protected area networks. Ocean & Coastal Management, 148: 214-230.

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

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.

 

Other relevant website address or attached documents

Summary of habitat types and threat status for the Mallory Seamount, Trough and Slope Complex EBSA. Data from Sink et al. (2012).

Threat Status

Ecosystem Type

Area km2

Area (%)

Vulnerable

Agulhas Hard Outer Shelf

102.8

0%

 

Agulhas Hard Shelf Edge

1,496.1

7%

 

Agulhas Muddy Shelf Edge

81.0

0%

 

Agulhas Sandy Shelf Edge

432.3

2%

Vulnerable Total

 

2,112.1

10%

Least Threatened

Agulhas Sandy Outer Shelf

193.8

1%

 

South Atlantic Abyss

2,839.3

13%

 

South Atlantic Lower Bathyal

623.1

3%

 

South Atlantic Upper Bathyal

196.9

1%

 

Southwest Indian Abyss

6,463.2

30%

 

Southwest Indian Lower Bathyal

4,407.4

20%

 

Southwest Indian Seamounts

3,009.7

14%

 

Southwest Indian Upper Bathyal

1,942.7

9%

Least Threatened Total

 

19,676.0

90%

 

Status of submission

The Agulhas Slope and Seamounts EBSA was recognized as meeting EBSA criteria by the Conference of the Parties. The revised Mallory Seamount, Trough and Slope Complex EBSA name, description, and boundaries still need to be submitted to COP for approval.

 

COP Decision

dec-COP-12-DEC-22

 

Assessment of the area against CBD EBSA criteria

C1: Uniqueness or rarity High

Justification

This area includes 3 of 4 known seamounts within the Davie Seamount cluster (Sink et al., 2011, 2012). These seamounts are relatively isolated and are thus likely to host distinct communities. The steep slope (20°) of Mallory Trough is the steepest portion of the entire South African continental shelf. It is also the only trough system in the Benguela region, and slopes as steep as 20° are globally very rare.

 

C2: Special importance for life-history stages of species High

Justification

The Agulhas Slope and Seamounts is recognized as a spawning area for small pelagic fish (sardine, anchovy, horse mackerel) and hake (Hutchings et al., 2002, Sink et al., 2011). This apex area of the Agulhas Bank is also recognized as a critical area for retention of spawning products. Eddies in this area help re-circulate water inshore and link important nursery areas with spawning habitat on the shelf edge. The shelf edge constitutes foraging area for offshore seabirds (Birdlife data, see references below).

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

Justification

Threatened habitat types in this area include Agulhas hard outer shelf and shelf edge, Agulhas muddy outer shelf and Agulhas sandy shelf edge (Sink et al., 2012.). Regionally Critically Endangered leatherback turtles frequent this area (Petersen et al., 2009a; Harris et al., 2018), and the shelf edge is a feeding area for offshore seabirds (Petersen et al., 2009b). One of the pelagic habitat types characterised by elevated productivity and frequent fronts (Lutjeharms et al., 2000, Lagabrielle 2009, Roberson et al., 2017) due to shelf edge upwelling is also considered threatened (Sink et al., 2012).

C4: Vulnerability, fragility, sensitivity, or slow recovery High

Justification

This area includes hard shelf edge and seamounts (some of the hard grounds are untrawled). These are likely to support fragile long-lived biota. Video images of the shelf edge show cold-water corals, gorgonians and large sponges (Sink et al., 2011). Vulnerable biota that use this area include long-lived seabirds, turtles and sharks, and the area has been identified by analyses aimed at identifying priority areas for reducing by-catch in the large pelagic fishery (Sink et al., 2011.)

C5: Biological productivity High

Justification

There is higher productivity here, which is related to the eastern limit of the Benguela upwelling on the outer shelf (Pelagic habitat type Ab3) and very frequent SST and chlorophyll fronts (Lutjeharms et al., 2000, Lagabrielle 2009, Sink et al., 2011, 2012, Roberson et al., 2017). Cool productive water is advected onto the shelf in this sheer zone through Agulhas Current–driven upwelling cells (Lutjeharms et al., 2000).

C6: Biological diversity High

Justification

This area has high pelagic and benthic habitat heterogeneity. Four pelagic habitat types (Ab3, Bc1, Cb3 and Cb4) and ten benthic habitats occur in this dynamic area, leading to its selection in a national systematic plan (Sink et al., 2011, 2012).

C7: Naturalness High

Justification

Rough grounds and strong currents already offer some protection from pressures to this area (Sink et al., 2011, 2012). Relatively lower levels of disturbance occur in this area (Sink et al., 2012), and most of the local hard areas fall outside of the hake trawl footprint (Sink et al., 2011).

[Top]

Files you can download