Shining new light on South African rivers, estuaries and rocky shores

18 June 2014


The NMMU research team on the coast near Port Elizabeth.  Dr Miranda (left), holding the BenthoTorch, Prof Perissinotto (centre) and Jacqueline Raw (right)

A portable scientific instrument, known as the BenthoTorch (manufactured by bbe Moldaenke, Germany)  is providing a diverse group of South African aquatic scientists with the means to measure algal growth off living cells in their natural habitat.  Various algal species have adapted their nutrient uptake systems enabling them to survive in shallow water close to the shoreline, where sunlight still penetrates to the sea or river bed. This habitat is home to benthic algae, ranging from the microscopic to the enormous. Such flora play an essential role in primary production.   The ability to measure the level of algal growth, in situ, as well as the dominant groups present (the BenthoTorch can distinguish the pigment signatures of green, blue-green and diatom algae), is of enormous importance for assessing the condition and ecosystem health of streams, rivers, estuaries and coastal shorelines.

Traditional methods include sampling of benthic algae by scraping surface materials or rapid deep-freezing and subsequent chlorophyll extraction. However, these methods cannot determine different algal groups. Alternatively, the use of time-consuming microscopy is limited to accessible objects rarely found in the field. Benthic algae measurements have, therefore, become much easier with the development of the BenthoTorch, which enables quick and easy analysis of benthic algae in real time and in situ by utilising the fluorometric characteristics of the different algal pigments in the intact cell. Thus, no sample preparation is needed. 


Andrew de Villiers using the BenthoTorch to sample periphyton biomass in the Umgeni River in South Africa. (Photo: Mark Graham)

In South Africa, GroundTruth Consulting are using the BenthoTorch – with a standardised sampling method they devised – for the proposed Lesotho Polihali IFR (in-stream flow assessment) setting and a variety of local studies. With funding received from the Water Research Commission the scale of the project has been increased, and an MSc student is using the BenthoTorch to understand periphyton dynamics in open canopy wadable rivers in a summer rainfall environment.  Related work is being undertaken with another BenthoTorch by Justine Ewart-Smith (Freshwater Research Centre).


Andrew de Villiers using the BenthoTorch in the Senqu River (Lesotho)

In the marine environment, Professor Renzo Perissinotto and Dr Nelson Miranda of the Nelson Mandela Metropolitan University (NMMU) in Port Elizabeth have, for some time now, been using the BenthoTorch‘s big brother, the Fluroprobe.  The Bentho-fluoroprobe has been used to collect data from St Lucia Estuary (KwaZulu-Natal), since 2004, by their UKZN research group.  Dr Miranda  has been collecting data since 2009 as part of a project titled ‘‘Climate Change and the Management of KZN estuaries: St Lucia Estuary’’, under a Research Agreement with  the iSimangaliso Wetland Park Authority.   Prof Perissinotto is currently the holder of the DST/NRF Research Chair in Shallow Water Ecosystems, housed at NMMU, as well as Professor Emeritus at UKZN.  After the establishment of the Research Chair last year, Dr Miranda became involved and used the Bentho-fluoroprobe in a project addressing the recently discovery of tufa stromatolite ecosystems on the south coast (Eastern Cape), in collaboration with Tommy Bornman of SAEON, Rosemary Dorrington of Rhodes University, David Bell of NMMU and others.  A scientific publication on their work is imminent.  Both projects are ongoing and Dr Miranda now uses the BenthoTorch and the older Fluoroprobe in a dedicated pelagic mode.

Corina Carpentier of Benten-Water using the BenthoTorch in the Danube River in the Netherlands.

Corina Carpentier of Benten-Water using the BenthoTorch in the Danube River in the Netherlands.

The South African researchers, who also include Toni Belcher from the company BlueScience, have been fortunate to link up with the experience of Corina Carpentier who works in the Netherlands and has just completed her PhD – with the marvellous title of “Carpet of the Sun: On the Quantification of Algal Biomass“. Corina will be visiting Bill Harding (DH Environmental Consulting) and Andrew de Villiers (GroundTruth) in South Africa later this year.  Last year, the BenthoTorch was used in a large study of the Danube River (the largest river in Europe), and this resulted in a dataset of over 100 sampling points along 2,500 km of river (left and right bank, and tributaries). Parameters included in the study were phytobenthos biomass and biodiversity, phytoplankton biomass, benthic invertebrates, fish, nutrients (N, P), flow velocity, transparency of the water, general physico-chemical parameters (pH, T, Oxygen, EC, etc.), and a huge number of chemical parameters (pesticides, industrial chemicals, etc.).

The BenthoTorch embodies the following features: no sample preparation needed; automatic substrate correction; integrated instrument display; GPS sensor; cable-free operation; data logger function; rechargeable (internal) battery and USB connection.  Anyone who has utilised chlorophyll data in their monitoring and/or research will know the frustration of not being able to have instantaneous measurements.  Well, the BenthoTorch and the AlgaeTorch, a similar instrument that allows for rapid measurement of chlorophyll signatures from phytoplankton in lakes and reservoirs, provide just this: instantaneous readings off living cells!  As demonstrated in the research cited hereunder, the BenthoTorch provides a non-destructive means of sampling sensitive and/or rare communities such as stromatolites.

Here are two links to research articles in which the BenthoTorch played an important role: Link 1   Link 2


In South Africa the AlgaeTorch and BenthoTorch are supplied by DH Environmental Consulting (Pty) Ltd.  (   (see previous post on the AlgaeTorch instrument).




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