December 2023 Newsletter

Hello Everyone,

If you’ve been down to Die Oog recently you would have noticed that the water has risen to levels last seen prior to the 2017-2019 drought. We have not received this much rain during a winter season in many years.

Good winter rains

The chart below shows rainfall measured at Constantia SAEON station, which may be considered representative of rainfall received at Die Oog. Rainfall received to date for 2023 is highlighted on the chart and referenced to 2014 (similar rainfall almost a decade prior) and 2017, when the drought was at its worst. Looking at other stations around the Cape Town area which show rainfall history dating back to the 1980s, you’d be interested to find the last winter seasons with this level of rainfall were recorded during 1987 and 2001, respectively.

Bird life at Die Oog

The good winter rains brought Die Oog to life and springtime was enjoyed by many who came to see the weavers building their nests and the newly hatched chicks from the coot and geese family. We appreciate all photographers that came to visit and shared beautiful photographs!

City council work at Die Oog

This year FODO has needed assistance from the City Council and they have responded timeously on every occasion. During June they sent a team with a dredging excavator, which was tasked with removing debris and sludge from the banks of the pond and around the island so that the water can once more reach the sanctuary area at the back of the island. They were also tasked with removing invasive plant species such as Typha Capensis and Tradescantia Zebrina.
A combination of removing these invasive plant species, coupled with a sewer overflow in the residential area neighbouring Die Oog, unfortunately created an ideal environment (high nutrient levels and no competition for growing space) for another highly invasive freshwater floating fern, Salvinia Molesta (or more commonly called the Kariba weed), which took over the entire water surface of Die Oog by end July 2023.

Considering that, at the time, Western Leopard Toads had begun migrating to other water bodies in the Cape, Friends of die Oog met with the City Council’s management team as a matter of urgency on Friday 11 August. Several items were discussed with the excessive Kariba Weed growth being addressed. Its ability to engulf the water surface, blocking sunlight needed by other aquatic plants and algae to carry out photosynthesis, poses a threat biodiversity by lowering oxygen levels in the water.

A team from the council arrived at Die Oog just 4 days later, working for 8 days straight, including a rainy weekend, clearing the water surface by 23rd August.

Breeding season kicks off during super blue moon

The pond had been cleared just in time ahead of the migration of the Western Leopard Toads to Die Oog which coincided with the super blue moon on the nights of 30-31 August. The toads appear to have selected a full moon to migrate to Die Oog during 2022 as well (Sept 7-10, 2022). It’s not to say that Western Leopard Toads will migrate on the evening of a full moon, but it appears that something in the gravitational forces may encourage collective migration when they are ready to breed.

Water quality at Die Oog around the time of Western Leopard Toads

Water sampling data from Die Oog shows clearly the spike in e-coli levels subsequent to a sewer overflow being reported around end May. This coincided with unsatisfactory levels of chlorophyll and elevated un-ionized ammonia, both indicators of poorer water health.

Increased Chlorophyll is indicative of phytoplankton abundance and biomass in the water. It is considered an effective measure of trophic status.
Un-ionised Ammonia is calculated using the measured soluble ammonia, temperature, pH and conductivity values. The target water quality range is < 0,007 mg/l.

You can find more data on all inland water bodies around the Cape here

While the sewer overflow likely triggered the excessive growth of Salvinia molesta, it was not all bad news. The growth of the Salvinia Molesta (Kariba weed) has been proven to extract both nutrients and pollutants from the water. This can clearly be seen in the water sample data from Die Oog, where e-coli levels dropped back down to below 100 CFU/100ml from August and they were as low as 15 (insignificant) during the time when the toads were breeding at Die Oog (water sample was collected during the first week of September 2023).

Nonetheless, it was imperative that we remove the weed, since excessive growth along the water surface blocks sunlight penetration over time which can impact photosynthesis and therefore oxygenation of the water below. Samples from Die Oog show lower levels of oxygen saturation in the water column (range from 24% to 67%) from April 2023, while oxygen saturation readings had typically ranged from 60% to 100% from 2020 to end 2022.

The toadlet migration from Die Oog

The development of the eggs into tadpoles and then into baby toads (metamorphosis), takes more than 10 weeks. The toadlets have started emerging from early December.

Please do not return toads or toadlets to Die Oog. Western Leopard Toads live in surrounding gardens and wild vegetation and ONLY come to Die Oog to breed.

How you can help to save the toadlets in your garden

Cover drains with mesh, install a toad saver in your pool or garden ponds (this could just be a net hanging over the edge into the water), consider putting a strip of mesh or a stone on the side of dog water bowls.

A small vegetable patch can create the ideal home for little toadlets. There are plenty of insects for them to eat, it’s cool from the watering. They protect the veggies from being eaten by insects.

A compost heap (where you throw fruit and vegetable matter) is also a mutually beneficial opportunity to attract biodiversity to your garden.

Photographs courtesy of Zandvlei Trust

Friend of Die Oog Cards

Please reach out to us (admin@dieoog.org.za cc ajmkhodge@yebo.co.za) if you’d like to purchase a pack of custom-made cards featuring endemic fauna residing at Die Oog. They were beautifully designed and painted by Michelle Liebenberg. The proceeds net of the artist’s charges are used for maintenance and care of Die Oog.

Security and maintenance

An important aspect of our role as Friends of Die Oog (FODO) is to engage with the city council and relevant organizations like WESSA for the overall maintenance and improvement of our beautiful City.

Positive work by the council includes the clearing of plant overgrowth in and around the dam, maintaining the fence around Die Oog and along the wetland towards the M3, the creation and maintenance of fire breaks.

In addition, we employ a gardener who usually comes weekly but due to current low funds we are reconsidering this arrangement.

Please support die Oog by ordering some notelets

45% of the proceeds go towards maintenance of Die Oog
R60 for a set of 3 with envelopes

PLEASE NOTE
Gate times are daily from
6:30am to 6:30pm.

Many hands make light work

We would like to extend a heartfelt thank you to all our loyal members for their support during this year. Without your help, we would not be able to maintain this precious spot.

Please check your inbox for a renewal notice if you have not renewed this year’s membership.

You can also help grow our membership base by extending an invite to family and friends. Annual membership for the whole family is only R100.

Please click on this link for membership renewal or donations. You are also welcome to email us at admin@dieoog.org.za if you have any questions.

From all of us on the Friends of Die Oog committee, may you and your loved ones have a blessed festive season and a happy 2024.

Best Regards,
Keryn Tsimitakopoulos
Co-chair for Friends of Die Oog