Potential sites for suitable coelacanth habitat using bathymetric data from the western Indian Ocean

Green, A.; Uken, Ron; Ramsay, Peter J.; Leuci, Rio; Perritt, Samantha

doi:10.4102/sajs.v105i3/4.68

Cited by 3 publications

(4 citation statements)

References 11 publications

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“…33 The slump features may also pose new exploration sites for coelacanth. 34 These features occur between two known living coelacanth habitats at Sodwana Bay 35 and Mzumbe 36 , and at a depth similar to habitats reported elsewhere 37 .…”

Section: Outer Shelf and Slopesupporting

confidence: 70%

Lifting back the waters: Marine geophysics provides new insights into the uThukela Banks Marine Protected Area

et al. 2022

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Using the first high-resolution geophysical data set collected from the uThukela Banks Marine Protected Area (MPA), we reveal a plethora of hitherto unknown or poorly resolved seabed features. In tandem with several remotely operated vehicle dives, we improve on the previous National Biodiversity Assessment map for the area and reveal a more complex picture of the seabed geology and geomorphology on which the MPA is predicated. The upper slope (-120 m and deeper) is dominated by small canyons, gullies and rills that occasionally extend to the shelf edge and form a series of slumps. Suspected cold-water corals were imaged on the interfluves of the Thukela Canyon. The mid to outer shelf (-60 to -100 m) is mostly rocky, and is composed of Pliocene-age siltstones for the most part. Aeolianite shorelines are found at depths of 60 m and 100 m, in which palaeo-lagoons and parabolic aeolian dune systems are also preserved. These features provide habitat for mesophotic corals and demersal fishes. Overlying and abutting hard rock substrates are unconsolidated sandy sediments that are mobilised by the inshore movement of the Agulhas Current. An inshore mud belt characterised by pockmarks associated with free gas expulsion is mapped for the first time. A well-developed palaeo-drainage pattern is also revealed, posing exciting new opportunities for the study of benthic communities associated with palaeo-estuaries and lagoons now exposed at the seabed. Several new habitats, both inside and out of the MPA boundaries, should form the basis for future research within the MPA, in addition to informing expansions of the MPA.

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Section: Outer Shelf and Slopesupporting

confidence: 70%

Lifting back the waters: Marine geophysics provides new insights into the uThukela Banks Marine Protected Area

et al. 2022

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“…periods needed for a change in morphology) would typically be longer. 5 The important preservation factors for such relict seafloor topography are thus surmised as:…”

Section: Discussionmentioning

confidence: 99%

“…Despite several investigations, 1,2,3,4 the seafloor morphology of many areas off KwaZulu-Natal is poorly resolved or often completely unknown. Many of the bathymetry charts in use today are based on very simple echosounding, 5 in which complex seafloor morphology is often not revealed as a result of the poor resolution of the data. Recently collected multibeam bathymetric data from the Durban Bight in KwaZulu-Natal reveal an unprecedented glimpse of Number One Reef, a drowned calcarenite barrier complex 3 offshore of Durban Harbour (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Number One Reef: An overstepped segmented lagoon complex on the KwaZulu-Natal continental shelf

Green

Leuci²,

Thackeray³

et al. 2012

S Afr J Sci

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This study of the bathymetry of the mid-shelf of the Durban Bight, KwaZulu-Natal revealed a series of previously undocumented seafloor features. These features were mapped using a high-resolution multibeam bathymetric echosounder and a detailed map of the seafloor topography was produced. We recognised several features that closely resemble features of contemporary segmented lagoon and lake systems: semicircular seafloor depressions, arcuate ridges, cuspate spits and prograding submerged barriers. Based on the striking similarity in morphology to Kosi Bay -a segmented lagoon system from the sandy northern KwaZulu-Natal coastal plain -a similar evolutionary model is proposed. This model is of an incised valley formed following a sea level lowering to the Last Glacial Maximum at about 18 000 BP. Thereafter, continued transgressive infilling occurred to a point where an extensive lagoon and back-barrier system was established. At this point, sea levels remained static, causing the net segmentation of the system and the slow closure of the tidal basins or circular depressions. This type of seafloor topography is rarely preserved and is the result of fortuitous cementation after deposition and the later removal of sediment that would ordinarily bury such features.

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“…Research to date has focused primarily on canyons in the eastern margin at depths of ca. 150 m, as these are more accessible on the narrow continental shelf and thus more easily sampled (Bang, 1968;Sink et al, 2006;Green and Uken, 2008;Wiles et al, 2013;Green, 2011), and are home to the rare coelacanth (Venter et al, 2000;Green et al, 2009). Comparatively little is known, however, about the Cape Canyon system on the western margin.…”

Section: Introductionmentioning

confidence: 99%

Benthic species patterns in and around the Cape Canyon: A large submarine canyon off the western passive margin of South Africa

Filander¹,

Smith

Cawthra

et al. 2022

Front. Mar. Sci.

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Although submarine canyons are internationally recognized as sensitive ecosystems and reported to be biological hotspots, regional studies are required to validate this consensus. To this end, hydrographic and benthic biodiversity data were collected during three cruises (2016-2017) to provide insights on the benthic patterns within South African canyon and non-canyon offshore areas. A total of 25 stations, sampled at 200-1000 m depth range, form the basis of the multivariate analysis. Diversity gradients were calculated and then differences were compared across substrate types and depth zones represented within 12 canyon and 13 non-canyon stations. Significant differences in both substrate and depth were evident, despite measures being highly variable. This observation of varying diversity in different substrates is in line with previous studies. No clear pattern was observed for species diversity (delta+). However, non-canyon stations overall showed a higher diversity in comparison to canyon stations. A notable peak in diversity is observed in canyon areas in the 401-500 m depth zone. Species richness followed an opposing pattern, as it decreased with depth and was consistently higher in canyon areas. These results align with the well-defined influence of depth-related variables on the distribution of taxonomic groups and the substrate available, at various scales. The eutrophic characteristic of the Benguela region may have attributed to the insignificant diversity differences between canyon and non-canyon stations. To assess the benthic species structure in canyon and non-canyon areas, we converted the 108 benthic species into a gamma+ matrix. We then modelled the biological response to predictor variables (substrate and depth). Although the canyon and non-canyon areas have an overlapping species composition, the main effects (canyon vs. non-canyon, depth, and substrate) showed significant differences. Thirteen species were characteristic of canyon areas, whilst only three distinguished non-canyon areas. The region has a long history of anthropogenic activities, so the observed benthic profiles may already be altered. The current study therefore provides the first detailed taxonomic description and analysis of benthic species profiles in the Cape Canyon, and advances important baseline information necessary for understanding the ecological importance of the Cape Canyon.

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Potential sites for suitable coelacanth habitat using bathymetric data from the western Indian Ocean

Cited by 3 publications

References 11 publications

Lifting back the waters: Marine geophysics provides new insights into the uThukela Banks Marine Protected Area

Lifting back the waters: Marine geophysics provides new insights into the uThukela Banks Marine Protected Area

Number One Reef: An overstepped segmented lagoon complex on the KwaZulu-Natal continental shelf

Benthic species patterns in and around the Cape Canyon: A large submarine canyon off the western passive margin of South Africa

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