Oceanographic Research Institute

Durban, South Africa

Oceanographic Research Institute

Durban, South Africa
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Porter S.N.,Oceanographic Research Institute | Schleyer M.H.,Oceanographic Research Institute
Coral Reefs | Year: 2017

Dynamics in reef cover, mortality and recruitment success of a high-latitude coral community in South Africa were studied over 20 yr with the aim to detect the effects of climate change. Coral communities at this locality are the southernmost on the African continent, non-accretive, attain high biodiversity and are dominated by soft corals. Long-term monitoring within fixed transects on representative reef was initiated in 1993 and has entailed annual photo-quadrat surveys and hourly temperature logging. Although sea temperatures rose by 0.15 °C p.a. at the site up to 2000, they have subsequently been decreasing, and the overall trend based on monthly means has been a significant decrease of 0.03 °C p.a. Despite this, minor bleaching was encountered in the region during the 1998 El Niño–Southern Oscillation event, again in the summer of 2000/2001 and in 2005. A significant decreasing trend of 0.95% p.a. in soft coral cover has been evident throughout the monitoring period, attributable to significant decreases in Sinularia and Lobophytum spp. cover. In contrast, hard coral cover gradually and significantly increased up to 2005, this being largely attributable to increases in cover by Acropora spp. Recruitment success and mortality of both soft and hard corals has displayed high inter-annual variability with increasing but non-significant trends in the last 5 yr. The reduction in soft coral cover has been more consistent and greater than that of hard corals, but it is difficult at this stage to attribute this to changes in water quality, acidification-linked accretion or temperature. © 2017 Springer-Verlag Berlin Heidelberg

Ayers M.J.,University of KwaZulu - Natal | Scharler U.M.,University of KwaZulu - Natal | Fennessy S.T.,Oceanographic Research Institute
Marine Ecology Progress Series | Year: 2013

Penaeid prawns are targeted in the Thukela Bank shallow-water trawling grounds in south-eastern Africa. Based on previous studies, these targeted prawns are assumed to primarily use 2 large estuaries (St. Lucia and Richards Bay/Mhlathuze) as nurseries on the KwaZulu-Natal (KZN) coast, which comprise over 80% of the estuarine habitat in the region. However, St. Lucia has been closed to the Indian Ocean since 2002 due to continued separation from the Mfolozi River, cessation of dredging required to open the inlet, reduced freshwater flow and drought conditions. To study the effects of prawn trawling and prawn nursery loss on the ecosystem, Ecopath with Ecosim models of the Thukela Bank were constructed. Models were fitted to total catch (t) for 1990 to 2009, and biomass trends were estimated by scaling Ecosim feeding interaction parameters to prey trophic level. Prawn trawling was modelled using fishing effort data. Prawn recruitment was modelled via the 'hatchery stocking' function in Ecosim simulating nursery loss along the KZN coast. Various prawn recruitment and trawling effort levels were simulated from 2010 to 2040. Decreasing prawn recruitment positively affected benthic fish and carnivorous benthos biomass and negatively affected prawn, commercial crustacean and benthopelagic fish biomass. Negative effects were exacerbated and positive effects were decreased by high versus low trawling effort. The results suggest that indirect anthropogenic and environmental factors, such as recruitment from estuarine nursery areas, can impact offshore fisheries catches. Therefore, when modelling and managing marine ecosystems, it is important to couple processes between adjacent systems, particularly for critical life-history stages. © Inter-Research 2013.

Green A.N.,University of KwaZulu - Natal | MacKay C.F.,Oceanographic Research Institute
African Journal of Marine Science | Year: 2016

This paper examines the distribution of unconsolidated sediment in the KwaZulu-Natal Bight located along the east coast of South Africa. Results show that there is a general shelf-wide sediment distribution of coarser grain sizes between depths of 60 and 100 m, punctuated by a broad swathe of mud offshore of the Thukela River. Seasonal changes in sediment distribution patterns are small, being restricted to seaward fining on the inner shelf off the fluvial sources. Sediment distribution reflects a partitioning between sediment populations that are current- influenced and relict (palimpsest) populations associated with submerged shorelines. Wave ravinement during the deglacial transgression, the reworking of submerged shorelines during sea-level stillstands and, to a lesser extent, the Agulhas Current system, are the dominant controls on sediment distribution. © 2016 NISC (Pty) Ltd.

Fennessy S.T.,Oceanographic Research Institute | Roberts M.J.,Branch Oceans and Coasts | Paterson A.W.,South African Institute For Aquatic Biodiversity
African Journal of Marine Science | Year: 2016

This introductory paper lays the basis for this supplementary issue by briefly presenting the state of knowledge on the KwaZulu-Natal (KZN) Bight at the start of this multi-disciplinary, multi-institutional, ship-based research project that ran from 2009 to 2013. The rationale and aims of the project are also described. The project was a major component of the South African Department of Science and Technology’s African Coelacanth Ecosystem Programme (ACEP), which has been prominent in supporting research on the east coast of South Africa and the wider South-West Indian Ocean. Pivotal to this was the RS Algoa, which was made available for two 30-day surveys (winter and summer) in the KZN Bight by the Department of Environmental Affairs. Although some aspects of the bight ecology are known, much of the research is dated and fragmented, and required refreshing and consolidation in order to produce a platform upon which the understanding of the region’s ecosystem functioning could be established. Much of the oceanographic knowledge is also dated, with no dedicated surveys and significant measurements undertaken since 1989. The overarching theme of the KZN Bight project was to examine the relative importance of sources of nutrients to the central KZN coast and how these are taken up and recycled in the ecosystem, and to describe aspects of the benthic biodiversity, which is poorly described in much of this region. An ambitious project, its accessibility to a ship-based research platform and the diverse scientific skills of the participating scientists allowed considerable success, as reflected in the papers that follow. © 2016 NISC (Pty) Ltd.

Maggs J.Q.,Oceanographic Research Institute | Mann B.Q.,Oceanographic Research Institute | Cowley P.D.,South African Institute For Aquatic Biodiversity
Fisheries Research | Year: 2013

A key element of an ecosystem-based approach to fisheries management is the use of marine protected areas (MPAs) as part of a holistic management strategy. This study, based in the South-West Indian Ocean, evaluated the benefits of area closure to vulnerable fishery species, which have been depleted by overfishing. A controlled fishing survey was conducted seasonally between 2006 and 2011 in the Pondoland MPA on the East Coast of South Africa. The MPA includes a 400km2 no-take zone where all forms of vessel-based exploitation are prohibited. Three endemic sparids (slinger Chrysoblephus puniceus, Scotsman Polysteganus praeorbitalis and poenskop Cymatoceps nasutus) and one widely distributed serranid (yellowbelly rockcod Epinephelus marginatus) were chosen as study species. These are slow growing, high trophic level species, which are prominent on rocky reefs in the Pondoland area and have been depleted by overfishing. Relative abundance was estimated using catch-per-unit-effort (CPUE) and length frequency distributions were used to determine the size structure of fish populations. The relative abundance and the mean length of all four species were significantly greater in the no-take zone. Over the 5-year study period, CPUE of C. puniceus and C. nasutus in the no-take zone increased as did the mean length of all species, except C. nasutus. This study presents clear evidence that the Pondoland MPA no-take zone is providing insurance against the depletion of vulnerable fishery stocks in fished areas, thereby establishing the basis for the enhancement of adjacent fisheries. © 2012 Elsevier B.V.

Steyn E.,Oceanographic Research Institute | Schleyer M.H.,Oceanographic Research Institute
New Zealand Journal of Marine and Freshwater Research | Year: 2011

A tagging study was undertaken on Blood Reef off Durban, South Africa, to investigate movement patterns of Panulirus homarus rubellus as well as inshore/offshore population differences. Lobsters were collected by SCUBA divers and baited traps. Traps caught larger lobsters than divers and trap catches were somewhat male-dominated (40% female:60% male). Lobsters were predominately resident with only 3% of recaptured lobsters moving over 500 m. Long shore movements were probably related to foraging behaviour and sanding and scouring of reefs. Larger lobsters were caught on offshore reefs (>10 m depth) than on inshore reefs (<10 m depth). The absence of large lobsters (>100 mm carapace length, CL) on inshore reefs may be related to fishing mortality. Low juvenile numbers (<50 mm CL) on offshore reefs suggest that post-larval lobsters settle on inshore reefs. An exponential decay model indicated that a small percentage of the population (males: 1.3%; females: 2.5%) move offshore with females mainly moving at 3 years of age and males between 1 and 3 years of age. © 2011 The Royal Society of New Zealand.

Fennessy S.T.,Oceanographic Research Institute
African Journal of Marine Science | Year: 2016

The project entitled Ecosystem Processes in the KwaZulu-Natal Bight, part of the African Coelacanth Ecosystem Programme (ACEP), enabled the description of demersal fish communities over soft sediments, including from some areas that have rarely been explored in the subtropical waters of the east coast of South Africa. A total of 165 fish taxa from 78 families were caught, and were dominated by the Sparidae (five species), Triglidae (four species), Acropomatidae (three species), Macrouridae (eight species), Chlorophthalmidae (one species), Paralichthyidae (three species) and Sciaenidae (six species), which together contributed 75% and almost 60% to numbers and weight, respectively. The most ubiquitous species were Chlorophthalmus punctatus and Pagellus natalensis. Species composition was structured mainly by depth, and proximity to the Thukela River, the latter being particularly influential on the adjacent Thukela Bank that harbours a unique community. There are close affinities between KZN Bight soft-sediment fish communities and those off Western Australia, and particularly with communities from East Africa. The unique nature of fish communities off the Thukela River is part-motivation towards the establishment of a large marine protected area in the northern part of the KZN Bight, which is increasingly the focus of disruptions such as impoundments and mining. © 2016 NISC (Pty) Ltd.

MacKay C.F.,Oceanographic Research Institute | Untiedt C.B.,Oceanographic Research Institute | Hein L.,Oceanographic Research Institute
African Journal of Marine Science | Year: 2016

The relatively wide KwaZulu-Natal Bight between St Lucia and Durban on the north-east shelf of South Africa is characterised by several circulation features driven by the Agulhas Current, wind and coastal inputs. A large multidisciplinary programme investigated the sources and relative influences of nutrients on the shelf. Within this, and to address a critical knowledge gap, this study describes macrobenthic (<1 mm) composition and frequency from 16 stations, assigned amongst four oceanographic focus areas. The areas were predetermined across the disciplines to represent upwelling, outwelling and a semi-persistent eddy, with nutrients and primary productivity being measured at each. Environmental variables such as sediment distribution, sediment TOC and bottom water physico-chemistry were determined at a significantly larger spatial scale. Our study postulated that oceanographic focus areas support significantly different macrobenthic assemblages, and that composition and relative distribution is due to measurable habitat attributes at each. Macrofauna were relatively abundant and particularly rich at >1 000 taxa. Annelida, Arthropoda, Mollusca, Echinodermata, Sipuncula and Cnidaria (>50 taxa each) were the dominant macrobenthic groups in the bight. Annelida were dominated by the polychaete families Spionidae, Terrebelidae and Cirratullidae, which were generally associated with outwelling and a mud depocentre off the Thukela River. Two unique and distinctive assemblages were found, one in the Thukela Mouth focus area and another on the midshelf between Thukela and Durban. The latter is influenced by poorly sorted, coarse sand and with probable influences from the Durban Eddy. There assemblages were abundant, rich and specific to this habitat. Correlation, PERMANOVA and CAP analyses showed assemblage fidelity to the focus areas. Medium sand, fine sand, mud and the variance of overall sediment type were the habitat drivers underlying macrofaunal abundance distributions. © 2016 NISC (Pty) Ltd.

Untiedt C.B.,Oceanographic Research Institute | MacKay C.F.,Oceanographic Research Institute
African Journal of Marine Science | Year: 2016

The composition and distribution of macrobenthic communities was investigated in three areas in the KwaZulu- Natal Bight, a section of shelf off the east coast of South Africa. Areas were pre-selected on the basis of three known oceanographic features, posited to deliver land- or Agulhas Current-derived nutrients onto the shelf and to drive ecosystem functioning in this region. Replicate sediment samples were collected with a 0.2 m2 van Veen grab, during two surveys (A, B) corresponding with normal periods of high and low rainfall, respectively. A subset of the full station array was selected across the shelf in an arrangement of increasing depths (inner-, mid- and outer shelf) through each feature area to investigate the spatial distribution and feeding modes of macrobenthic taxa. The two periods showed some differences in abundance and numbers of macrobenthic taxa, but were not statistically different. Total macrobenthic abundance from Survey A was 20 215 individuals from 642 taxa, decreasing to 18 000 individuals from 503 taxa during Survey B. Polychaeta and Crustacea were the dominant taxa sampled; abundance of the latter was attributed largely to a proliferation of Paguristes sp.1 at inner-shelf samples in the midbight (Thukela) region during Survey B. Similarity classification distinguished seven sample groups reflecting differences in feature areas and shelf positions under investigation. The Thukela River midshelf community supported the highest macrobenthic abundance, while the midshelf off the southern bight (Durban region) was most species rich. Findings were attributed to the habitat complexity of the midshelf which includes a palaeo-dune cordon at the 60 m isobath. Functionally, the community was dominated by interface- and deposit-feeding fauna, emphasising the importance of trophic plasticity in an environmentally variable and heterogeneous shelf environment. © 2016 NISC (Pty) Ltd.

MacKay F.,Oceanographic Research Institute | Cyrus D.,University of Zululand | Russell K.-L.,Oceanographic Research Institute
Estuarine, Coastal and Shelf Science | Year: 2010

St Lucia, the largest estuarine lake complex of its type in Africa, is characterised by natural physico-chemical spatial and temporal fluctuations. This estuary functions as an important nursery area making use of a number of different habitat types and associated environmental conditions. The system has been subject to a number of natural episodic events such as cyclonic flooding and cyclical droughts, the most current has persisted since 2001, resulting in almost permanent mouth closure. Furthermore, high levels of evaporation have reduced lake levels and resulted in compartmentalisation of the system for up to several years at a time. St Lucia is sensitive to evaporation and therefore to vast salinity fluctuations and hypersaline conditions. The upper reaches in North Lake are particularly sensitive to drying out and extended hypersaline events. The macrobenthos has been well studied, but no studies have concentrated on the entire system for such an extent of time. Macrobenthic samples were initially collected in 2004, again in 2005 and biannually from 2006 to 2008. This study was part of a larger multidisciplinary programme aimed at determining the effects of long term drought conditions on the ecology of the St Lucia system, and increasing current understanding of the system response to future catastrophic climatic events. Three areas were sampled (North and South Lake and Estuary) at five sites per area, over five years. Data were analysed by representing communities through time series depictions and discriminating sites and sampling periods to test multidimensional relationships. Linkages between biological distribution and selected environmental forcing variables were investigated. The system was found to be highly variable and supporting a large number of different habitats and co-occurring environmental conditions. This variability makes it difficult to discern spatial or temporal patterns in environmental conditions and macrobenthic ecology. However, some level of resilience to wide ranging environmental changes associated with drought is maintained. This study was able to determine that there exists a core of taxa able to persist even under shallow depth conditions and prolonged hypersalinity. These taxa clearly have a self recruiting strategy and are therefore not reliant on mouth opening to re-establish local populations. This finding alone has important bearing for future studies and management of the system under similar adverse conditions. © 2010 Elsevier Ltd. All rights reserved.

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