Can Diatoms Help Save Hewitt’s Ghost Frog?

Vidette sampling diatoms at Geelhoutboom River

We have recently brought in a new monitoring tool to help devise conservation management actions for Hewitt’s Ghost Frog: a full spectrum diatom analysis of the Geelhoutboom River. But firstly, what is a diatom? Diatoms are microscopic, one-celled algae that can be found in colonies or as single cells and are usually abundant in aquatic systems. A diatom forms a cell wall made of silica and we identify different species by the unique cell wall patterns, cell size, and shape.

We propose a study of diatoms can benefit tadpole conservation. The presence of heavy metals and toxins can interrupt diatom cell wall formation, this along with the fact that diatoms rapidly respond to environmental change due to species specific needs (pH, nutrients, etc.) make them excellent bio-indicators. Furthermore, because diatoms are primary producers at the foot of the aquatic food-web, they have a direct relationship to environmental stressors making them even better monitors. Conservationists seek more environmental information in order to make measured decisions, regarding the future wellbeing of the endangered Hewitt’s Ghost Frog our current work could become a useful tool for them.

For this project, Vidette Botha, a post-grad student, set out to assess the diatom composition of the Geelhoutboom River and to compare differences in species abundance and diversity during seasonal cycles.

Vidette first had to establish if ghost frog tadpoles do indeed feed on diatoms. For this she had to analyze the stomach contents of tadpoles. The result indicated that diatoms make out a large part of their diet. She then compared this against the diatoms available in the rivers. This study is still underway but has already produced some interesting findings. For example, we have found that the dominant diatom species found in the Geelhoutboom River include many Eunotia species, which are indicatory of acidic habitats that are electrolyte-poor. Another species equally dominant to all the Eunotia species is Nupela schoemaniana which is associated with clean water, and good quality habitats.

However, signs of cell wall defamation slightly above environmental norm did occur. This might be due to the presence of toxins in the water and requires further investigation. The forestry industry makes use of a toxin called Kilomax which is labeled ‘Frog friendly’, however it is unknown if this toxin is harmful to other morphological stages or diatoms. Another significant find is the species Peronia fibula which was present in both Geelhoutboom River sites and has been found less than 5 times in South Africa.

Diatom species found in the study

We hope this study will continue to provide interesting findings and provide us with a new tool in the conservation planning for Hewitt’s Ghost Frog.


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  1. georgia said,

    on October 27th, 2012 at 2:43 pm

    Is there any evidence or data to illustrate that this conservation method is benefiting/increasing the numbers of ghost frogs in the area?

  2. David said,

    on November 13th, 2012 at 5:20 pm

    how did you analyse the stomach?did you have to sacrifice the animal or was another method used?

  3. werner said,

    on November 14th, 2012 at 10:03 am

    Hi Gerorgia, the data only illustrates that tadpoles do eat diatoms and the diatoms in turn is an indicator of environmental health. Thus we can look at the diatoms to asses the conditions of the rivers.

    Hi David, unfortunately we had to euthanize some tadpoles for the project, but all at a good cause.


  4. gabriella said,

    on December 10th, 2012 at 9:40 pm

    Is there any evidence that this is benefiting the hewitt ghost frogs? What is the next step for this investigation?what will you do next to help the frogs?

    And I was curious about the VIE marking blog; how is this benefiting the hewitt ghost frog, and is there any evidence to support this?

    Thanks, and good luck with the rest of your research

  5. louisa said,

    on December 11th, 2012 at 10:00 pm

    Hi, I was curious as to how many tadpoles were involved in this study?

  6. werner said,

    on December 16th, 2012 at 8:31 am

    gabriella – this techniques (diatom and VIE) is just tools that we use to understand the needs and conservation status of the frogs better. It have no direct benefit to them.

    louisa – we sacrificed only two tadpoles per site, we had four sites, thus eight tadpoles in total.

  7. Andrew said,

    on February 20th, 2014 at 4:30 pm

    Hiya! I was wondering what the status of the Hewitt ghost frog was at present? hows the research going? are their numbers increasing?

    also have you started monitoring the chytrid fungus? is there any evidence to prove this is affecting the frogs numbers?

    Thanks, this is very interesting!

  8. werner said,

    on March 12th, 2014 at 8:16 am

    Dear Andrew, currently the IUCN status of Hewitt’s Ghost frog is Endangered and it seems the population is stable. Due to funding the project has been downgraded to only absence/presence monitoring. Initial chytrid swabs showed a high chytrid prevalence to up to 80% (see:;jsessionid=8119BB795A92844194D89D7468B3FC48). We not sure how this affects the adult numbers or metamorphing frogs.

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