Figure 1.
The framework used to classify ecosystems within the Southern Ocean.
Ecoregions were defined on the basis of important environmental drivers and their potential to prevent dispersal. Biogeographic patterns identified in the literature were also incorporated. A hierarchical approach was then applied within each ecoregion, nesting the two main habitat types (geomorphic features within bathomes) to identify environmental types.
Table 1.
Circumpolar datasets used within the classification.
Table 2.
Benthic bathomes and the ecological and biological events used to define them.
Table 3.
The geomorphic features of the Southern Ocean classified according to the attributes of the seabed surface substratum.
Figure 2.
The benthic ecoregions, restricted environments and marine protected areas identified within the Southern Ocean.
An environmental type is a unique combination of an ecoregion, bathome and geomorphic feature. Existing marine protected areas and regions where planning processes are underway to propose future representation, were identified. Where large gaps in existing and proposed representation were found, the locations of geographically restricted environmental types were identified. These restricted environments indicate areas of potential future marine protected area selection since there are limited spatial options for protecting the biodiversity for which these environments are a surrogate.
Figure 3.
Environmental types and the bio-physical data used to drive the classification.
A) The 562 environmental types (in colour) and ecoregion outlines (refer to figure 2 for names) broadly reflect the underlying data used within the classification B) Bathomes derived from bathymetry and species-depth relationships C) Geomorphic features; Abyssal Plain (1), Bank (2), Canyon (3), Cliff (4), Coastal (rugged) Terrane (5), Contourite Drift (6), Cross Shelf Valley (7), Fracture Zone (8), Island Arc (9), Island Coastal Terrane (10), Lower Slope (11), Marginal Ridge (12), Marginal Plateau (13), Mid-Ocean Ridge Rift Valley (14), Ocean Trough (15), Plateau (16), Plateau Slope (17), Ridge (18), Rugose Ocean Floor (19), Seamount Ridges (20), Seamount (21), Shelf (22), Shelf Deep (Depressions) (23), Structural Slope Region (24), Trench (25), Trough Mouth Fans (26), Upper (Continental) Slope (27), Volcano (28) D) Seabed temperature E) Duration of the year where more than 85% of the region is covered by sea ice F) High positive and negative values indicate areas of consistently high and low summer productivity respectively. Values approaching zero indicate areas that vary greatly between years.
Table 4.
Benthic ecoregions and their features (see Fig.2 for the location of each ecoregion).
Figure 4.
Marine protected areas and their spatial coverage of ecoregions and representation of environmental types.
A) The proportion of the seafloor and the proportion of environmental types included either partly or wholly within existing MPAs are displayed within four broad geomorphic classes. These classes are further described in Table 3 and are represented within the plots from top to bottom as Abyss (white), Slope (light grey), Oceanic Shallow (dark grey) and Continental Shelf (black). B) The total number of environmental types and seafloor area for each geomorphic class are also shown. The incomplete bars within PAR and AB have values of 2.95 E6 km2 and 6.59 E6 km2 respectively. The ecoregion code names are: SOI (South Orkneys Islands), SA (South Atlantic), RS (Ross Sea), PAR (Pacific-Antarctic Ridge), O (Oates), K-KP (Kerguelen-Kerguelen Plateau Subregion), K-DK (Kerguelen-Deep Kerguelen Subregion), DC (Del Cano), AP (Antarctic Peninsula), AB (Atlantic Basin), A (Amundsen).