Mangrove Swamps, KZN

This month was time for my annual Unisa practical and this year it was in Winkelspruit which is at Illovo Beach in KwaZulu Natal.  Seventy-five odd students checked in at the Natalia Resort on Sunday the 18th of August and settled into our 5 person flatlets.  I managed to get a room with my friends, Amanda Mileson, Rehenza Le Roux, Elzanne van Zyl and new friend Sue Gallagher.  We had a seaview room and the sunrises and sunsets were something spectacular!

The first day was taken up by lectures from Prof Tikki who gave us the low down on estuaries.  That night we had to do a poster on what we had learned. It felt a bit like we were back at Primary school to be honest.

The next day we went on a field trip to the Beechwood Mangrove Swamps which was very interesting.  I have never been to a mangrove swamp before so there was lots to see.

First stop was at this section of White Mangroves (Avicennia marina).  They are the one's with pencil roots that stick up straight out of the anaerobic mud to get their oxygen.  They get rid of their salt by extruding it on the back of their leaves.  We all had a go at licking dusty leaves to taste the salt... the things we do in the name of knowledge!

I was very interested in these Climbing Whelks (Terebralia palustris) that live on the side of the mangrove trees to escape predators.  

This is a Black Mangrove (Bruguiera gymnorhiza).  It has knee roots for obtaining air.  They are photo-inhibited which means they cannot grow in sunlight so they grow in the shade of the White Mangroves.  They get rid of their salt by sending it to the old yellow leaves which then fall down.

Beneath the White Mangroves, hundreds and hundreds of Red Mangrove crabs are found in their little holes.  They eat the leaves of the White Mangrove and are the only vegetarian crabs known.

Under the Black Mangroves were the Uca Fiddler Crabs where the males have one very large chelea which they wave about to defend territory and to attract females.  They are much smaller than the Red Mangrove Crabs.

There are only 3 species of Mangrove trees in South Africa.  All 3 are found here and the last one we saw was the Red Mangrove (Rhizophora mucronata). Their name is derived from their leaves which have the little spike at the end called the Mucro.  The leaves also have a salt gland which helps them get rid of their salt.  They have prop roots which help them stay up in very wet soil and which also breath for the tree.

Have you ever seen a tree ant nest?  This was also a new one for me.  This nest was in a Hibiscus tiliaceus tree, South Africa's only indigenous  hibiscus.

It was then across the river to the other side to do a bit of fishing.  Prof Tikki put a net out and we rounded up hundreds and hundreds of tiny fish.  Fish use the estuary as a nursery as it is more protected from predators than the open ocean.  The entire area is so full of litter and rubbish though, it was quite disappointing.

One of the most interesting fish we found was this Purse mouth.  It has an extendible section which moves out and away from its mouth to help it feed on the bottom of the estuary.  

After our fishing, we had to make our way back across the river and the tide had risen quite significantly by then.  I was literally waste deep at that point.

We had work to do back at the resort so we made our way back to the bus and back home. After supper we had to do yet another Primary School poster, this time about the Food web in an estuary.  This time, we did not have present on the poster, but we peer-reviewed each others posters.  

The day was done and tomorrow it was off to the rocky shores, an outing I was really looking forward to.