Trophic functioning of ecologically different kelp bed communities in South Africa
Kelp bed communities are vital ecosystems in shallow coastal habitats along the cooler coastlines of the world’s oceans, typically where upwelling is prevalent. On the south-western and west coast of South Africa, these macroalgae form complex 3-dimensional habitats which are home to diverse faunal assemblages that depend directly or indirectly on these organisms. Kelp primarily enters the marine food web in the form of detrital particles which are continuously generated from the erosion of the distal portions of the kelp fronds. These particles enter the water column and become available to kelp associated filter-feeders which, as a consequence, often dominate the faunal biomass of these habitats. Some of these particles are also exported and utilised in adjacent marine systems, and thus kelp beds have a far-reaching influence on various marine food webs. Kelp beds are ecologically variable in the south-western Cape region, varying in faunal and floral assemblages, as a result of a multitude of natural and anthropogenic factors. Our current understanding of their functioning is therefore limited, as it is based solely on a single historic model of a west coast kelp bed. Understanding how the different organisms interact within these systems, with particular focus on food web dynamics and the relative role of phytoplankton and POM derived from kelp decomposition, will provide key insights into the functioning of these habitats.
In summary, this project aims to improve our understanding of the flow of organic matter through ecologically different kelp bed communities which dominate the shallow coastal regions around the Cape Peninsula and on the south-western coastline of Southern Africa.
Thermal characteristics of the South African nearshore
A study conducted by Smit et al. in 2013 comparing coastal in situ and satellite data found a consistent warm bias occurring along the coast of South Africa in which satellite data were found to be as large as 6ºC warmer at certain sites. These findings are supported by similar studies in the international literature. In lieu of this and other discoveries, researchers are placing more emphasis on the use of in situ data for studies in the nearshore (<400 m) region. To do so a comprehensive in situ dataset must be compiled and verified against itself as well as multiple satellite datasets. Robert Schlegel is creating the code necessary to build, test and monitor this dataset, which will be named the South African Coastal Temperature Network (SACTN). He will then be using the SACTN for three primary investigation: further understanding sub-mesoscale coastal temperature structures, thermal impact on structuring biogeographical patterns of kelp, other seaweeds and a range of inshore animal species. Upon completion all code created will be made publicly available for the programming language R on GitHub and CRAN.
Association between the brown alga, Splanchnidium rugusom, and its bacterial symbionts
My research focus is on the surface associated symbiotic bacteria on the marine macroalga Splachnidium rugosum. The microbial community that colonises the surface acts as a membrane between the environment and host alga as such it has a direct impact on the lifecycle, health and physiological development of its host. Many of the bacteria associated with S. rugosum are known to produce various secondary metabolites and enzymes involved in cell signalling, polysaccharide modification and novel xenobiotic pathways. Through culture independent techniques such as metagenomics and 454 next generation sequencing the bacterial community composition in response to various environmental shifts as well as the interactions between the host and its unique surface symbionts can be explored. The association between polysaccharide composition within the host macroalga and the enzyme cocktail produced by various bacterial symbionts is exploitable in various industries ranging from pharmaceuticals to biofuels. Harnessing the potential of biological systems can be achieved by applying the knowledge of how the microbial community interacts with the surrounding environment, its host as well as itself.
Stephen Mackey (PhD candidate)
Tamsyn Livingstone (PhD candidate)
An offshore bioregional classification on the east coast of South Africa and its validity as a biodiversity surrogate in marine conservation planning
This project aims to develop a biogeographic classification for the water offshore of the KwaZulu-Natal province using available oceanographic and benthic data as surrogates for biodiversity pattern. The validity of the classification will then be tested with in situ data in order to gain insight into the best parameters to use when developing biogeographic classifications as well as to test whether the surrogate data accurately reflect the benthic biological communities on the continental shelf.
Ecophysiology of two kelp species: cellular responses to environmental stressors
My work is using eco-metabolomics as an approach to determine changes in the biochemistry of kelp species in response to environmental shifts. This work will use a non-targeted analysis of a metabolite extract from each of the kelp species. The data resulting from the analysis of the metabolite composition will produce a fingerprint of the kelp’s metabolome, providing a novel approach to analysing an organism’s physiology. The analysis of the kelps’ metabolite data will take place within the context of corresponding morphological and environmental data, making it possible to link changes in the kelp metabolites to environmental cues. The end result will be a MSc that will provide insights in to the biochemistry of the kelp species in response to thermal stress, but also act a “proof of concept,” setting the stage for eco-metabolomics as a insightful and important tools in the furutre of marine photo-autotroph ecophysiology.
The effect of kelp removal on species composition on Ecklonia maxima forests on the coast of South Africa, and the effect of environmental variables on kelp recovery and species composition
Kelp forests are important systems from both a biological and socio-economic perspectives. Kelp forests are highly productive, and not only provide a habitat for various economically important fauna, but also act as a source of energy to adjacent marine ecosystems. There is increasing evidence to suggest that kelp forests are under threat due to rising sea temperatures – since temperature is one of the main drivers of kelp ecology and distribution, ocean warming above kelp’s optimum range may have detrimental effects for these ecosystems. This study aims to determine the community composition and environmental drivers of three contrasting kelp communities on the coast of South Africa (Odekraal, Betty’s Bay and Bortjies reef). Ecological sampling will take place seasonally (winter and summer), and the methodology used will be based on that of the Kelp Ecosystem Ecology Network (KEEN). For the purpose of this work we will focus on the KEEN control plots only, which will allow for comparison of ecological data between the contrasting kelp sites with the intention to use continuously monitored environmental variables (thermal regime; wave exposure; light availability; ect.) and ecophysiological responses (from a sister study) to explain the kelp’s ecological performance.
Keshnee Pillay (MSc candidate)
Using stable isotopes to understand trophodymanics on the southern Benguela ecosystem
One approach to analyse ecosystems is to establish the feeding interactions between different species i.e. food webs. These interactions are variable over time and space as food webs have many associations between a diversity of consumers, producers and resources each forming a different trophic level and filling a specific trophic position. There are three different paths through which energy could flow within a food web i.e. top-down (web controlled by predatory activities), bottom-up (web controlled by producer activities) and wasp-waist control (mid-web control e.g. by small pelagic organisms within a pelagic system). This study focuses on understanding the trophic relationships off the west coast of South Africa. This is an area characterized by seasonal coastal upwelling, resulting in high primary and secondary production which in turn supports a high abundance of tertiary consumers including commercially exploited species such as the Cape hakes (Merluccius paradoxus and Merluccius capensis), sardine (Sardinops sagax) and anchovy (Engraulis capensis), by-catch species such as kingklip (Genypterus capensis), monk (Lophius vomerinus) and cape horse mackerel (Trachurus capensis), and protected species such as cape fur seal (Arctocephalus pusillus), cape gannet (Morus capensis) and the humpback whale (Megaptera novaeangliae). Trophic interactions within the Benguela ecosystem and trophodynamics of economically and ecologically important species have been acknowledged to be an important component towards ecosystem understanding and resource management however there is still limited qualitative data in this area. The traditional methods of understanding such interactions (trophodynamics) are gut content analysis, direct observations in laboratories and/or field and tracer techniques. As effective as these methods are in answering some trophic-related questions they lack the ability to determine large scale, ecosystem-level patterns in feeding. One technique used to grasp the interactions between components of the marine trophic web is that of stable isotope analysis (SIA). The advantages of SIA, with respect to marine ecology, are that information generated is not only of ingested prey but also of assimilated diet, represents long-term feeding behaviours and can be used to distinguish between offshore or inshore feeding patterns by following the natural abundance of particular elements, in this case carbon (δ13C) and nitrogen (δ15N).
Sam Bolton (MSc candidate)
Mapula Mkwena (MSc candidate)
Tevya Lotriet, Janine Greuel, and Rudolph Philander (BSc (Hons) candidates)
Population studies of the kelps Laminaria pallida and Ecklonia maxima along a thermal gradient in False Bay
The Cape Peninsula is an area where the cold Benguela and the warm Agulhas Current meet, resulting in a temperature gradient. Kelp ecosystems occurring in the False Bay area are important as they support a variety of marine fauna and flora, both directly and indirectly. The thermal gradient experienced in False Bay could affect the population structure of macroalgae occupying this region.
Studying the population structure and fecundity of kelp in this area will provide new knowledge about the temperature on the kelp populations. Within the False Bay area, various sampling sites will be set up and temperature recorders installed. Various morphological measurements will be recorded in order to determine differences among the study sites representing the thermal gradient exist. To identify differences in the fecundity along the gradient, the amount of zoospores released at the various study sites will be measured. The study will be focused on Ecklonia maxima and Laminaria pallida.
Identification of benthic reef community structures to test validity of defining biozones using physical characteristics as proxies for biodiversity patterns
This study aims to investigate the validity and robustness of habitat and environmental surrogates for biodiversity mapping to be used for marine conservation planning off the KwaZulu-Natal offshore environment. A number of benthic and pelagic offshore biozones have been defined as a basis for conservation planning analyses using remote sensing techniques and existing sea-bed data. The study will form part of a larger ACEP Surrogacy project that tests the validity of defining the biozones using physical characteristics as proxies for biodiversity patterns. This honours study will focus on the identification of community structures of the benthic reef environment using Remotely Operated Underwater Vehicle (ROV) footage, collected during the 2014 ACEP research cruise, for the quantification of the epifaunal species composition. This will provide data for verification of habitat type, description of offshore habitats and validate the surrogacy approach previously used to define benthic habitat types in this region. The knowledge generated through this thesis will support the National Marine and Coastal Ecosystem Classification and Map which will feed into further spatial assessments and plans at a national and provincial or regional level.
Janine Cunningham (BSc (Hons) candidate)