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

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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. Importantly, the EBSA includes the Mallory escarpment and trough segment of the Agulhas-Falkland Fracture Zone. This is a unique feature in the region, and certainly slopes as steep as this one (20°) are globally very rare. The area was identified as a priority through a national spatial plan because of high habitat diversity. Since the original description (of Agulhas Slope and Seamounts), the boundary has been refined and split into two to better represent the underlying EBSA features. No ecological research has been conducted in this EBSA but is strongly recommended.

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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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Summary of updates and revisions to the EBSA description

Boundary, name, description and criteria ranks all updated.

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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. Importantly, the EBSA includes the Mallory escarpment and trough segment of the Agulhas-Falkland Fracture Zone. This is a unique feature in the region, and certainly slopes as steep as this one (20°) are globally very rare. The area was identified as a priority through a national spatial plan because of high habitat diversity. Since the original description (of Agulhas Slope and Seamounts), the boundary has been refined and split into two to better represent the underlying EBSA features. No ecological research has been conducted in this EBSA but is strongly recommended.

 

Introduction of the area

Mallory Escarpment and Trough includes the outer margin along the southern tip of the Agulhas Bank in South Africa, chiefly encompassing the key features of the Agulhas-Falkland Fracture Zone, including 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, resulting in a dynamic offshore area with high pelagic and benthic habitat heterogeneity. Further, 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 this area 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. It also contains regionally unique, globally very rare features.

 

Description of the location

EBSA Region

Southern Indian Ocean

 

Description of location

The EBSA is at the apex of the Agulhas Bank at the southern tip of the continental shelf edge off southern Africa. It is directly south of Cape Infanta and Cape Agulhas in the Agulhas-Falkland Fracture Zone, and is entirely within South Africa’s EEZ. It contains the Mallory escarpment and trough, and lies immediately west of the Shackleton Seamount Complex EBSA.

 

Geo-Location

SIO_2_EBSA.geojson

 

Area Details

Feature description of the area

The area includes benthic and pelagic features, including: the shelf edge, a very steep slope and a trough as part of the Agulhas-Falkland Fracture Zone; shelf-edge driven upwelling; and fragile and sensitive habitat-forming species. Habitat diversity is thus particularly high for a location this far offshore. This dynamic area 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.

The delineation of this EBSA was refined since its first description, and is now split into two EBSAs: one for the seamounts, and one for the escarpment and trough features. The revision was based on high selection frequency of sites in the two systematic biodiversity plans covering the area, tighter alignment to the benthic topography (from a new national dataset: De Wet 2012), new focus areas for MPA expansion in South Africa, presence of fragile and sensitive habitat-forming species, and new delineation of the constitutent ecosystem types. Effectively, these new data helped to improve the precision of the EBSA boundary so that it better reflects the underlying features. It is presented as a Type 2 EBSA because it contains “spatially stable features whose individual positions are known, but a number of individual cases are being grouped” (sensu Johnson et al., 2018).

 

Feature conditions and future outlook of the proposed area

The shelf edge, slope and trough 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, the ecosystem types are in good ecological 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.

Sink, K.J., van der Bank, M.G., Majiedt, P.A., Harris, L.R., Atkinson, L., Karenyi, N., Kirkman, S. (eds) 2019. National Biodiversity Assessment 2018 Technical Report Volume 4: Marine Realm.  South African National Biodiversity Institute, Pretoria.

 

Other relevant website address or attached documents

Summary of habitat types and threat status for the Mallory Escarpment and Trough EBSA. Data from Sink et al. (2019).

Threat Status

Ecosystem Type

Area (km2)

Area (%)

Least Concern

Agulhas Basin Abyss

7799.9

59.7

 

Cape Basin Abyss

357.1

2.7

 

Southeast Atlantic Lower Slope

527.7

4.0

 

Southeast Atlantic Mid Slope

3.0

0.0

 

Southwest Indian Lower Slope

3487.2

26.7

 

Southwest Indian Mid Slope

898.0

6.9

Grand Total

 

13072.9

100.0

 

Status of submission

The Agulhas Slope and Seamounts EBSA was recognized as meeting EBSA criteria by the Conference of the Parties. The revised Mallory Escarpment and Trough 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

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).

 

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

Justification

One of the pelagic habitat types in the area is characterised by elevated productivity and frequent fronts due to shelf edge upwelling (Lutjeharms et al., 2000, Lagabrielle 2009, Roberson et al., 2017). Consequently, 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 threatened seabirds such as Albatross (Petersen et al., 2009b).

 

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

Justification

This area includes hard shelf edge and a very steep slope. 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 for an offshore site, comprising six ecosystem types at the confluence of the Indian and Atlantic Ocean basins. The very steep slope is also expected to host a rich diversity of species because it spans a very large depth range over a proportionately small area.

 

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).


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