Friends of Rietvlei
Member of the Wildlife & Environment Society of South Africa Western Cape Region
Newsletter June 2011
We are commemorating World Environment Day on 5 June 2011 with a beach walk in the Coastal section between Dolphin Beach and Sunset Beach.
Join us for the walk and contribute to World Environment Day by helping to clean up litter along the way.
Meet at the Dolphin Beach Parking Area (next to the hotel) at 14h30 on Sunday, 5 June 2011.
PLEASE CONTACT Pauline on 083 255 2537 if you require further information.
On Sunday afternoon 17 July we will be having an Indigenous Garden work party. Our indigenous garden at the entrance to Rietvlei is being revamped, as was reported in our previous newsletter, but we need to get some hands in there to help with some weeding and clearing in general. More details about this later.
The WESSA Friends Groups meeting on Saturday 14 May was attended by about 25 people, representing various Friends groups and WESSA staff members. We started off the programme with a short presentation on various challenges Friends of Rietvlei has and how we are dealing with these. Then representatives of several of the Friends groups, inter alia Zoarvlei, Bracken, Liesbeeck River and Tokai Forest, reported back on their activities and some of the problems they have.
Tony Rebelo from Friends of Tokai Forest gave a presentation on the introduction of iSPOT, a web-based system of recording sightings of plants and animals. This is developing rapidly in the UK, and a South African section is also being tested; if all goes well the system will be fully implemented towards the end of the year.
After a light lunch, many of the participants joined us for a walk to the two bird hides. The water levels were very low and because of this, the bird hides were not really the most suitable places to view birds; but on the way to the bird hides there were a large number of birds on the central pan. A large flock of flamingos decided to give us a fly-past show and thrilled us with their display, wheeling and turning right over where we were standing at the time.
Thanks to all our members who assisted to make this a memorable day.
The Estuarine Tube Worm
At our AGM a member of the Milnerton Canoe Club raised the issue of the problems caused by tube worms in the lower estuary, particularly in the vicinity of the two bridges at Woodbridge Island. We did some background reading to find out more about this little pest.
The Estuarine Tube Worm or Australian Tube Worm, Ficopomatus enigmaticus, comes from Australia and was first noticed in South Africa in the Cape Town area in 1951; probably introduced on the hulls of ships. It now occurs in estuaries in the Cape Peninsula and along the south coast. The tube worm has spread to many countries and most often causes problems by blocking intake and discharge pipes of power plants and also interferes with the operation of locks.
Ficopomatus enigmaticus is a small polychaete which builds and lives in a white calcareous tube about 2mm in diameter and 2 cm long. The worm feeds by extruding 12-20 branching gill plumes out of the open end of the tube filtering small food particles and passing them down to the mouth at the base of the plumes. At the same time blood passing through the gill plumes is oxygenated. When disturbed the plumes are withdrawn into the tube and the entrance sealed with a tough spiny operculum at the end of a modified gill plume.
The estuarine tube worm lives mostly in shallow water on rocks, concrete, wood, shells and other hard surfaces. It can occur as single, separate tubes, or as tangled, agglomerate masses forming incrustaceans up to 10cm or more thick. It does survive in sea water, but can only grow and reproduce in lower salinities of about 10-30 ppt (sea water is 35ppt or parts per thousand), and in water temperatures above 18C. Eggs and sperm are released into the water and the larvae live in the plankton, settling on a hard surface to start building a tube after 20-25 days.
The ecological effects of the tube worm in an estuary has not been studied in detail, however it does remove suspended particulate matter, reduces excess nutrients and improve oxygen levels in waters with poor water quality, particularly enclosed waters like boat basins and docks. Very high populations could compete for available food sources with other filter feeders.
In the Milnerton Lagoon the presence of Ficopomatus enigmaticus is mainly a nuisance where it grows under the wooden bridge and the road bridge. At the wooden bridge the colonies on the stones under the bridge is obstructing the free passage of canoes, particularly when the water levels are low. Fortunately it is quite easy to control colonies can be removed mechanically or by hand; but recolonisation occurs quickly because of the highly mobile larvae and rapid growth rate.
The ultimate solution in this estuary would be to return the estuary to its natural state with a natural salinity regime while this may not completely destroy the colonies, it will certainly slow down their growth and reproduction so that they will decrease to more manageable levels. This is of course a major objective of the Diep Estuary Management Plan, and the implementation of the plan is imperative to resolve issues like this infestation of Ficopomatus enigmaticus.
On Thursday 19 May Niel van Wyk took to the pink road for a trip to town. Here he relates his experience:
I have to go into the City Centre at least once a week on business, and on Thursday 19 May decided that I must use the new BRT system. I live in Royal Ascot, just more than 1 km from the Racecourse Bus Station, and about 14km from the City Centre.
It was a lovely sunny morning so I decided to walk to the station, arriving there at about 10h30. Having bought my ticket, the MyCiti bus arrived shortly afterwards and I boarded it for the drive to the City. There were about 20 people on the bus already, and at all the stations between Racecourse and Lagoon Beach people were disembarking and/or getting on. However after that, right through Paarden Island and Woodstock, no more passengers either got on or off the bus.
We arrived at the Civic Centre station about 20 minutes after leaving Racecourse, and I transferred to the Gardens intercity service as I wanted to be up in Loop Street in the vicinity of the Vlaeberg Post Office. The wait at the station for the Gardens bus was about 25 minutes, slightly longer than the scheduled 20 minute interval in the service (between 09h00 and 15h30 there should be a bus every 20 minutes). Eventually the bus arrived and I travelled up Long Street without having to worry about whether I would find parking. I disembarked at the Dorp Street stop and walked up to Loop Street; and, having concluded my business caught the bus in Loop Street back to the Civic Centre where I transferred to the Table View bus.
At the Racecourse and Civic Centre stations there were plenty of very friendly and helpful staff who really went out of their way to assist the passengers; advising which way to go, what to do, etc. When I paused to look at the mural on the wall in the Civic Centre station, a friendly voice immediately asked whether I needed assistance and where I wanted to go.
The trip back was quick, and I was back home just before 12h30. The whole trip thus took me nearly two hours, but keep in mind that I walked to the station and back, that is about 25 minutes in total. If I had taken my car into town, the round trip would probably have taken me about 50 minutes, so the bus experience was about 45 minutes longer.
Comparing the costs of the bus to travelling by car proves that it does pay to take the bus. My car runs on diesel, and with the help of the AA vehicle operating cost formulae, I worked out that the fuel alone for a trip straight there and back (no driving around in town) is about R26.39 at current fuel prices. However, using the formula for determining total vehicle operating costs, a trip to town and back in my car costs R42.00, more than 1 times the R20.00 cost of a return ticket to the City Centre. Just to break even on the fuel, the price of diesel will have to drop to below R7.80 per litre, a price I dont think well see soon, even then the total vehicle cost for the trip will be R35.56.
Taking the MyCiti bus on the pink road to the City Centre does pay, and you do not have the hassles of coping with irresponsible drivers or the problem of finding convenient parking in town. You may have to walk a bit to get to your destination, but that can only be good for your health. The service is good, apart from a few teething problems in the inner City routes, but in time this will improve and we will have a really great public transport service.
I can certainly recommend the MyCiti bus service to people living in our area; I know that Ill be using it regularly.
Environmental Education Centre 021 521 9900
Entrance Gate 021 557 5900
Emergencies and standby number 071 268 9637
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