,Um protruding stakes 1 he method 

 " J, d.sadwnw&e Ihjri ihfl 6Wk» 



2, ..^uMaM. ccUt.cs which .uod.lv 

 El P»VtW« 0« accretion, and the 



Big U« <" kcn on| y c,s " hroad 



of the scale ol changes 

 ' ', juried. Monthly mcasurc- 

 ZtSU dOliflfl r«8 showed irregular 



Saltol W»J ^Vl' ' rTnnt'hs 



H,rfaW lowcimg: over II months 



ven ol the sites showed net accrc- 

 m (maximum 4.4 cm.) add Ovc del 

 L-rftJg (maximum 2.8 em J. There 

 w .», no'cvidcnee lor widespread con- 



;;,„„, accretion over the area 

 .,„.i.'.ed IhC Chwitf* registered ou 

 i| lC stakes hcinu due to movements 

 jj mud shuaK to and I'm across the 

 riUdjtaS by wave action. One Snfe, 

 „„|, , sparse Zowo cover, received 

 capping of mud Up to Scm. thick 

 dOllllg October U»$, hut this had 

 largely dispersed <i month later. It 

 w; ,s noted that when onshore winds 



Ju.mpanted a rising tide there was 

 fleJfotitE movement of mud tow. mis 

 0 d into the zone occupied hv man 

 piovcy 



\< C Rl 1 .ON l NDI.R M INGROVt* 



Vertical accretion was measured 

 w.thin the mangrove fringe with 

 r.-tcrcnee to Livers ol brick dust 

 sin Cad on the surface at ten sites 

 .luring April 1967. The hnck dust 

 IAS disturbed hv burrowing crabs.. 

 Imi persisted sufficiently for measure- 

 ment- io he mailt over the suceeed- 

 .rtc three vcurs Us persislanee w..s 

 IB hhIk- .non ol the relative sialuhty 

 of lhe surface under the mangroves, 

 compared with the mudflats a heady 

 aesenbed. 



Sites near the inner I landward ) 

 margin ol lhe mangroves showed 

 slow mud accretion (up lo 0.7 cm 

 over three years), and sites in the 

 omtre of the mangrove zone (at high 

 neap lidc level) showed more rapid 

 mm! -tv.el.vm fun to 2-4 cm we. 



July, 1971 



three yenrs). Towards the outer (sea 

 ward)' margin there was much varia- 

 hou, from i minimum of 0.4 cm. to 

 a maximum of 4.6 cm. mud accre- 

 tion over three years. As all of the 

 sues measured showed a consistent 

 rise in mud level there can he no 

 doubt that vertical accretion is taking 

 place within the mangrove fringe at 

 the present lime. 



Mud accretion has proceeded nunc 

 rapidlv among .he pneumatophores 

 and around the trunks of each man- 

 grove plant (Hale 5 1 . raising the 

 surface up to 15 cm. above the inter- 

 vening areas of soft wet mud. In 

 this way, mangroves diicctly influence 

 (he pattern ol rnud accretion A similar 

 effect was obscivcd at Stony Point, 

 where mangroves have recently spread 

 on D9 a sandy foreshore area, and 

 patches of mud have accumulated 

 aromnl I he pneumatophores. When 3 

 network of pegs was nnplanted in 

 the sand here m simulate the effects 

 nt pncumalophorcs, il produced a 

 p.ueh of mud up to 0,3 em. thick 

 wuhin a month, lhe peg?; were then 

 removed, and the mud soon washed 

 away. Sedimentation among the 

 pneumatophores results from lhe fact 

 ihai they produce a calm-water 

 environment conducive lo dcposiumi 

 of muddy sediment thai would 

 otherwise remain in suspension, oi be 

 c-.Tied away. 



Within the mangrove commumiy 

 the ebb and How ol odes is confined 

 mainlv to intricately -branching creek 

 systems, in contrast with the smooth 

 and almost featureless lopographv of 

 lhe adjacent mudflats. Accretion of 

 mud around mangrove planls builds 

 up the suilacc on cither side of low 

 corridors, which gradually become 

 well-defined channels The creek sys- 

 icm is thus correlated with patterns 

 of mud accretion that arc detci mined 

 by ihc presence of mangroves. 



195 



