Environmental Variation and How its Spatial Structure Influences the Cross-Shelf Distribution of High-Latitude Coral Communities in South Africa

Coral communities display spatial patterns. These patterns can manifest along a coastline as well as across the continental shelf due to ecological interactions and environmental gradients. Several abiotic surrogates for environmental variables are hypothesised to structure high-latitude coral communities in South Africa along and across its narrow shelf and were investigated using a correlative approach that considered spatial autocorrelation. Surveys of sessile communities were conducted on 17 reefs and related to depth, distance to high tide, distance to the continental shelf edge and to submarine canyons. All four environmental variables were found to correlate significantly with community composition, even after the effects of space were removed. The environmental variables accounted for 13% of the variation in communities; 77% of this variation was spatially structured. Spatially structured environmental variation unrelated to the environmental variables accounted for 39% of the community variation. The Northern Reef Complex appears to be less affected by oceanic factors and may undergo less temperature variability than the Central and Southern Complexes; the first is mentioned because it had the lowest canyon effect and was furthest from the continental shelf, whilst the latter complexes had the highest canyon effects and were closest to the shelf edge. These characteristics may be responsible for the spatial differences in the coral communities.

Download Full-text

Coral dominance at the reef - sediment interface in marginal coral communities at Sodwana Bay, South Africa

Marine and Freshwater Research ◽

10.1071/mf02049 ◽

2003 ◽

Vol 54 (8) ◽

pp. 967 ◽

Cited By ~ 21

Author(s):

M. H. Schleyer ◽

L. Celliers

Keyword(s):

South Africa ◽

High Latitude ◽

Slow Growth ◽

Coral Community ◽

Reef Complex ◽

Tolerant Species ◽

Coral Communities ◽

Disturbed Environment ◽

Sediment Interface

Sedimentation is an important factor that influences the composition of coral communities. The high-latitude, marginal coral community in the central reef complex at Sodwana Bay, South Africa, is subjected to sedimentation at the reef–sediment interface. A lens of bioclastic sediment surrounds the sandstone reefs in the area and acts as a scouring and smothering agent. This affects the composition of the subcommunity on the reef margin at the reef–sediment interface. The interface was studied on two reefs in the complex and their subcommunities did not differ. Alcyoniidae and Scleractinia (34.4% and 34.4% cover, respectively) are the dominant taxa in the reef–sediment subcommunity, which includes genera such as Sinularia, Lobophytum, Sarcophyton, Montipora, Favia and Astreopora (in decreasing order of abundance). Sediment-tolerant species are prevalent, the Alcyoniidae being the most prominent and tolerant by virtue of their morphology. Corals in this environment are generally flat and fairly rigid colonies of Lobophytum and Sinularia spp. (14% and 10% cover, respectively), some with lobes to channel the movement of surge-driven sediment, or are erect, soft and pliable forms such as Sarcophyton spp. (10% cover) that easily shed sediment. Their dominance in this constantly disturbed environment may also be attributable to the low mortality, slow growth and overall persistence of the Alcyoniidae described in the literature.

Download Full-text

Exploring the Potential for Internal Tides to Reshape the Continental Shelf Edge Seafloor

Progress In Oceanography ◽

10.1016/j.pocean.2021.102575 ◽

2021 ◽

pp. 102575

Author(s):

Weifeng Gordon Zhang ◽

Zhen Cheng ◽

Andrew D. Ashton

Keyword(s):

Continental Shelf ◽

Internal Tides ◽

Shelf Edge

Download Full-text

Temporal movement of free-swimming fishes and their response to environmental variables in some of the rivers of Kruger National Park, South Africa

Environmental Biology of Fishes ◽

10.1007/s10641-021-01178-5 ◽

2021 ◽

Author(s):

Matthew J. Burnett ◽

Gordon C. O’Brien ◽

Bayanda Sonamzi ◽

Victor Wepener ◽

Colleen T. Downs

Keyword(s):

South Africa ◽

Environmental Variables ◽

National Park ◽

Kruger National Park ◽

Free Swimming

Download Full-text

Distribution of paracalanidae species (Copepoda, Crustacea) in the continental shelf off Sergipe and Alagoas States, Northeast Brazil

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592006000300001 ◽

2006 ◽

Vol 54 (4) ◽

pp. 173-181 ◽

Cited By ~ 12

Author(s):

Hortência Maria Pereira Araujo

Keyword(s):

Continental Shelf ◽

Rainy Season ◽

Environmental Variables ◽

Dominant Species ◽

Seasonal Distribution ◽

Northeast Brazil ◽

Oceanic Water ◽

Density Values ◽

Oceanic Species ◽

Parvocalanus Crassirostris

The spatial and seasonal distribution of the Paracalanidae species were studied in eighteen stations in the continental shelf off Sergipe and Alagoas States, northeast Brazil, in December, 2001 and 2003, and in June, 2002 and 2003. The Paracalanidae family was constituted by coastal and shelf species such as Parvocalanus crassirostris, Paracalanus quasimodo, P. indicus and P. aculeatus and oceanic species, Calocalanus pavo and Acrocalanus longicornis. Density values were higher in stations located at 10 m isobath with respect to those located at 20 and 30 m depths. Paracalanidae abundance presented differences between seasons with values higher in June (2002, 2003) than in December (2001, 2002). All species were more abundant in the rainy season except Parvocalanus crassirostris. Paracalanus quasimodo was the dominant species with average densities of 949, 740 and 41 ind.m-3 in December months and 4231, 2389 and 1185 ind.m-3 in June months, at stations with local depths of 10, 20 and 30 m, respectively. Canonical correspondence analysis showed that salinity and temperature were the environmental variables that presented significant correlation with the distribution of Paracalanidae species, probably because these variables are influenced by the estuarine waters and by the dynamic of oceanic water masses in the continental shelf.

Download Full-text

Submissions to the UN Commission on the Limits of the Continental Shelf: The Practice of Developing States in Cases of Disputed and Unresolved Maritime Boundary Delimitations or Other Land or Maritime Disputes. Part Two

The International Journal of Marine and Coastal Law ◽

10.1163/15718085-12341296 ◽

2013 ◽

Vol 28 (4) ◽

pp. 615-679

Author(s):

Barbara Kwiatkowska

Keyword(s):

South Africa ◽

Continental Shelf ◽

Trinidad And Tobago ◽

North Africa ◽

Law Of The Sea ◽

Basic Principles ◽

Maritime Boundary ◽

State Practice ◽

Maritime Disputes ◽

Present Part

Abstract This is the second part of a two-part article surveying state practice regarding Disputed and Unresolved Maritime Boundary Delimitations or Other Land or Maritime Disputes under the Rules of the Commission on the Limits of the Continental Shelf (CLCS). It reviews basic principles and the interpretation of the 1982 UN Law of the Sea Convention and the CLCS Rules. As the 2006 Barbados/Trinidad and Tobago Award and the 2012 ITLOS Bangladesh v. Myanmar Judgment reaffirmed, the CLCS Recommendations must in no way prejudice existing and prospective boundary delimitations, nor must they prejudice other land or maritime disputes. All practical means of giving effect to such “without prejudice” principles are carefully analysed. Part One covers Latin America and the Wider Caribbean, Northeast and Southeast Asia, and the South Pacific. The present Part Two covers South Asia and the Middle East, East Africa-Indian Ocean, South Africa, West Africa and North Africa.

Download Full-text

Influences of environmental variables in the spatial and temporal distribution of fishery resources of the continental shelf in the northeast of Brazil

Frontiers in Marine Science ◽

10.3389/conf.fmars.2016.05.00193 ◽

2016 ◽

Vol 3 ◽

Author(s):

Nobrega Marcelo ◽

Oliveira Jorge Eduardo

Keyword(s):

Continental Shelf ◽

Environmental Variables ◽

Temporal Distribution ◽

Spatial And Temporal Distribution ◽

Fishery Resources

Download Full-text

Dissolved Inorganic Nitrogen Fluxes at Sediment-Water Interface in Yangtze Estuarine Tidal Flat

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.288 ◽

2013 ◽

Vol 726-731 ◽

pp. 288-295 ◽

Cited By ~ 1

Author(s):

Huan Guang Deng ◽

Dong Qi Wang ◽

Zhen Lou Chen

Keyword(s):

Tidal Flat ◽

Environmental Gradients ◽

Inorganic Nitrogen ◽

Yangtze Estuary ◽

Water Interface ◽

Dissolved Inorganic Nitrogen ◽

Overlying Water ◽

Spatial Differences ◽

Estuary Sediment ◽

Temporal And Spatial

Yangtze estuary data, collected over three years, indicates that the temporal and spatial distributions of the environmental gradients reflect complicated seasonal changes and spatial differences in the exchange flux of the dissolved inorganic nitrogen (DIN= NH4++ NO3-+ NO2-) across the sediment-water interface. Overall in northern sites of Yangtze estuary, sediment was a source of ammonium (NH4+) (-3.67~10.65 mmol·m-2·d-1) probably because of higher salinities. Sediment was a sink for NH4+ in southern sites (-18.45~3.33 mmol·m-2·d-1) during most years. The exchange behavior of nitrate (NO3-) showed temporal and spatial variation from the upper to lower estuary and ranged from-32.8 mmol·m-2·d-1 to 35.8 mmol·m-2·d-1. The interface exchange direction of ammonium was affected by NH4+ concentration, but the relationship between NO3- concentration and the direction of flux was not obvious. The concentration of nitrite (NO2-) was very low and its interface flux was not related to DIN concentration. Overall, the sediment of Yangtze Estuarine tidal flat was a source of DIN to overlying water in the spring, but a sink for DIN during the other three seasons of the year.

Download Full-text

Responses of plant functional types to environmental gradients in the south-west Ethiopian highlands

Journal of Tropical Ecology ◽

10.1017/s0266467410000799 ◽

2011 ◽

Vol 27 (03) ◽

pp. 289-304 ◽

Cited By ~ 5

Author(s):

Desalegn Wana ◽

Carl Beierkuhnlein

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Relative Abundance ◽

Environmental Variables ◽

Environmental Gradients ◽

Plant Functional Types ◽

The South ◽

Ethiopian Highlands ◽

South West ◽

Functional Types

Abstract:Plant functional types across environmental gradients can be considered as a powerful proxy that reveals vegetation–environment relationships. The objectives of this study were to investigate the response in the relative abundance of plant functional types along altitudinal gradients and to examine the relationship of plant functional types to environmental variables. The study was conducted in the Gughe-Amaro Mountains, in the south-west Ethiopian highlands. We established 74 plots with an area of 400 m2(20 × 20 m) each along altitudinal ranges between 1000 and 3000 m asl. Data on site environmental conditions and on the abundance of plant functional types were analysed using the constrained linear ordination technique (RDA) in order to identify the relationships between plant functional types and environmental variables. Altitude, soil organic carbon, soil sand fraction and surface stone cover were significantly related to the relative abundance of plant functional types across the gradient. Tussocks and thorns/spines were abundant in lower altitudinal ranges in response to herbivory and drought while rhizomes and rosettes were abundant at higher altitudes in response to the cold. Generally our results show that topographic attributes (altitude and slope) as well as soil organic carbon play an important role in differentiating the relative abundance of plant functional types in the investigated gradient. Thus, considering specific plant functional types would provide a better understanding of the ecological patterns of vegetation and their response to environmental gradients in tropical regions of Africa prone to drought.

Download Full-text