The fascinating world of Umlalazi’s Mangroves

No other kinds of tree are as well adapted to an existence in salty, tidal estuaries as the mangroves. Their roots are specifically adapted to not only anchor them in the muddy substrate but also allow them to “breathe” by sticking up above the mud and prevents the tree from drowning. Known as “pneumatophores”, these roots look different in the various genera of mangroves – those of the white mangrove (Avicennia marina) look like pencils sticking straight up out of the mud, the black mangrove (Bruguiera gymnorrhiza) has knee-like structures protruding before going back into the mud, and the red mangrove (Rhizophora mucronata) grow “struts” straight from the trunk. They have to contend with excessive salt in their tissues, and concentrates this in old leaves that are continuously shed and replaced. Mangrove fruit are also very interesting; seeds germinate while still attached to the flower, and some, like the black and red mangroves, even grow a cigar-shaped “root”, or “hypocotyl”, that is designed to anchor the seed in the muddy substrate when it drops from the tree.

These adaptations of the mangroves benefit the entire ecosystem by trapping silt, stabilising the substrate, and feeding the food chain. Mangrove snails (Cerithidea decollata) cling to the trunks of the trees during high tide, safely out of reach of estuarine fish that move in with the tide. At low tide, they then descend to feed on the muddy surface. Crabs abound in the mangroves. Sesarma is a genus of land-based crab that digs holes up to 2m deep into the mud and avidly collects fallen leaves into their burrows. Fiddler crabs (Uca-species), known for the males having one enormous pincer which which they display to one another and to interested females, feed by rolling scoops of mud into balls in their mouths, with the discarded balls leaving tell-tale trails where the crab has moved. Mudskippers, those uniquely adapted amphibious fish that seem to be as at home out of the water as in it, must be among the most curious of the mangrove swamps’ denizens. Estuaries in general and mangrove stands in particular are extremely important refuges and nurseries for several kinds of fish and crustaceans, making their protection an economic imperative if fisheries are to be sustained into the future and highlighting the value of conserved areas like Umlalazi.

Many kinds of wading birds feed on the rich invertebrate fauna in a mangrove swamp, with the woolly-necked stork being the most obvious at Umlalazi. The reserve’s mangroves also forms an important winter habitat for the mangrove kingfisher. Mangrove swamps, with their dense stands of trees and muddy terrain, are difficult areas for large mammals, with the exception of monkeys, to utilise.

At Umlalazi, a boardwalk constructed through a mangrove swamp allows easy access to this fascinating world – if you have only a little bit of time to explore Umlalazi, this is undoubtedly where you should spend it!

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32 thoughts on “The fascinating world of Umlalazi’s Mangroves

    1. de Wets Wild Post author

      Thanks AJ. Indeed, all three mentioned do occur at Umlalazi, though in the areas we traversed the black and white kinds dominated and the reds were much harder to see.

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  1. scrapydo2.wordpress.com

    Sjoe dis interessant. Het wat Christina en jy skryf ook gelees oor al die dinge wat dieselfde is. Ek het gehoor dat Suid Afrika en Australië baie dieselde omstandighede het. Aardrykskunde was my hoofvak vir my graad studie. Dit interesseer my nog steeds baie.

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    1. de Wets Wild Post author

      Aardrykskunde en biologie was my twee gunstelingvakke op skool, en fassineer my ook nogsteeds Ineke. As jy vir my n kaart in die hand stop sal ek ure uit jou hare wees 🙂

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      1. scrapydo2.wordpress.com

        KLink bekend! Ons het natuurlik van kleins af padkaarte gebruik om te ry as ons met vakansie gegaan het. Pa het bestuur en ons het die pad gelees!My hoërskool het nie Aard aangebied nie en ek moes van grond af werk tot my derde jaar. Dit was egter lekker om te doen. Biologie was ook my vak wat meeste tyd gekry het.

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  2. MJF Images

    Great one Dries! They are so important and so threatened. They protect against coastal erosion by storms and are natural ways to protect against tsunamis. And they’ve been wiped out on a large scale by coastal development, everything from palm oil plantations in SE Asia to resorts in countries around the Caribbean.

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  3. Pat

    There is so much about a mangrove forest that is unique, I’m always amazed by what goes on there. The snails really grabbed my attention. That we’ve figured out that they know how far they’ve climbed by measuring their own energy use is mind-boggling. Maybe someday we’ll figure out how they can predict the height of the tide in a place where it is so irregular. Then maybe we’ll turn that science around and figure out ways to predict tides and save some lives. Can you tell I’m a science geek?

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  4. Christina B

    Die natuur is so slim en aanpasbaar. In die noorde van Wes-Australië by Broome is daar ook sulke mangrove swamps. Dit fassineer my om te dink dat die twee kontinente op ‘n stadium vas aan mekaar was. Hier is bv ook baobab bome in die noorde (word hier boab genoem) en plante van die protea familie.

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          1. Christina B

            Definitief, maar om dit te beleef moet ons ver ry (seker maar soos meeste mooi dinge). Nog ‘n ding: Perth lê op ‘n sandvlakte net soos die Kaapste vlakte. Sulke grys sand wat olierig is sodat die water daarvan afloop en nie mooi dreineer nie, wat ook bitter min voedingswaarde het. En rondom Perth is wat bekend staan as die “Wheatbelt” wat baie soos die Swartland en Overberg lyk, dis net baie groter.

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            1. de Wets Wild Post author

              Is dit nou nie interessant nie! As ek reg onthou is daar ook n varswatervissie, die galaxias, wat hier by ons net in die Kaap voorkom maar ook volop is in Australie se riviere – nog n aanduiding dat die twee kontinente eens aaneen was.

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