AACL BI OFLUX
Aqu a cu lt u r e , Aqu a r iu m , Con se r va t ion & Le gisla t ion
I n t e r n a t ion a l Jou r n a l of t h e Bioflu x Socie t y
Se dim e n t gr a in - size dist r ibut ion in t he La k e La u t
Ta w a r , Ace h Pr ov ince , I n don e sia
1
Syahr ul Pur nawan,
1I chsan Set iawan,
2Z ainal A. Muchlisin
1
Depart m ent of Marine Science, Facult y of Marine and Fishery Sciences, Syiah Kuala Univ ersit y , Banda Aceh 23111, I ndonesia; 2 Depart m ent of Aquacult ure, Facult y of Marine
and Fisheries, Syiah Kuala Univ ersit y , Banda Aceh 23111, I ndonesia. Corresponding aut hor: S. Pur naw an, sy ahrulpurnaw an@unsy iah.ac.id
Abst r a ct. The obj ect ive of t he pr esent st udy was t o evaluat e t he gr ain size dist ribut ion in Lake Laut Tawar . The st udy was done in May and June of 2012 at 5 locat ions: Boom , Klit u, Uj ung Mum par , Bint ang and Tower an. The sam ples wer e collect ed using a gr ab sam pler . The collect ed sam ples fr om t he r espect ive locat ions wer e sun dr ied and t hen sieved t o exam ine t he gr ain- size dist r ibut ion. The r esult showed t hat t he sedim ent t ypes wer e divided int o t hr ee cat egor ies: gr avel, sandy gr avel and gr avelly m ud. The Boom locat ion h ad gr avelly m ud ( pr edom inant ly m ud) t hat was well sor t ed, while gr avel was a m aj or por t ion of t he sedim ent in Uj ung Mum par and it was m oder at ely well sor t ed. I n addit ion, all of t he locat ions had negat ively skewed values, which indicat es a coar se- skew par t icle dist r ibut ion.
Ke y W or ds: gr anulom et r ic analysis, geost at ist ics, lake sedim ent , sor t ing, skewness.
I n t r odu ct ion. Grain size is one of t he m ost im port ant sedim ent param et ers and it is necessary t o int erpret t he deposit ional environm ent s ( Friedm an & Sanders 1978) . Variat ions in grain size dist ribut ion of lak e sedim ent s m ay reflect t he eart h’s surface processes such as t he dev elopm ent al processes of landform s t hrough changes in precipit at ion ( Siv asam andy & Ram esh 2014) . The grain size dist ribut ions are affect ed by v arious fact ors including t ransport at ion by rolling, suspension and salt at ion ( I nm an 1952; Dy er 1986; Folk 1974) . Crit ical st udies of t he sedim ent grain size hav e been carried out by Udden ( 1914) and Went w ort h ( 1922) , w ho int roduced t he Udden- Went w ort h scale. Furt herm ore, Friedm an ( 1961) dev eloped sedim ent st at ist ical review s based on arit hm et ic and m om ent m et hods, w hile Folk & Ward ( 1957) approached grain size dist ribut ion t hrough a graphical m et hod. Frequency dist ribut ions of sedim ent grain size ( nam ely m ean, sort ing, sk ew ness, and k urt osis) w ere used frequent ly t o int erpret t he precipit at ion of sedim ent w hen t hey re- ent er t he nat ural environm ent ( Folk & Robles 1964; Dy er 1986; Wacheck a- Kot k ow sk a & Kot k ow ski 2011; Welt j e & v on Ey nat t en 2004) .
Lak e Laut Taw ar is one of t he oldest v olcanic caldera in I ndonesia and it has an im port ant ecological role as t he habit at for som e endem ic species of fishes i. e. Rasbora t aw arensis and Poropunt ius t aw arensis ( Muchlisin & Sit i- Azizah 2009; Muchlisin et al 2012; Muchlisin et al 2015) . This lak e is sit uat ed about 1200 m abov e sea lev el. I t is 16 k m long and 4 k m wide and surrounded by m ount ains reaching abov e 2000 m . The w at ershed is cov ered by rain forest s w hich are ex t rem ely affect ed by deforest at ion and agricult ural act ivit ies ( Muchlisin et al 2010) . Adhar ( 2008) st at ed t hat t he erosion condit ion of Lak e Laut Taw ar w as in a poor st at e and t his has led t o silt ing t he bott om of t his lak e. I n addit ion, Set iaw an ( 2013) carried out a st udy of grain size in Laut Taw ar Lak e, but did not com prom ise t he grain dist ribut ion analy sis based on t he st at ist ical approach. Hence, t his paper ex am ines st at ist ical analysis of t he sedim ent grain size based on a prev ious st udy report ed by Set iaw an (2013) .
2014) , for ex am ple in guppies, Poecilia ret iculat a t hat t urbidit y could lead t o a decreased collect iv e response t o predat ors and a loss of t he prot ect iv e benefit s of shoaling ( Kim bell & Morrell 2015) . I n addit ion, it w as st rong int eract ions bet w een t urbidit y, prey densit y and subst rat e t y pe on shrim ps predat ion by Thorn fish Terapon j arbua ( Macia et al 2003) . Ferrari et al ( 2010) st at ed t hat t urbidit y alt ers t he qualit y and quant it y of visual inform at ion receiv ed by t he m innow s, elim inat ing t heir abilit y t o generalize learned recognit ion of som e predat ors. This paper prov ides t he underst anding t he sedim ent ary deposit ional processes in t he Lak e Laut Taw ar, t his inform at ion is crucial in relat ion t o plan a bet t er conserv at ion st rat egy of Lak e Laut Taw ar.
M a t e r ial an d Me t h od
Se dim e n t sa m plin g. Lake Laut Taw ar is locat ed in Cent ral Aceh, Aceh Province, approx im at ely 1200 m abov e sea lev el. Sev eral short t ribut aries discharge int o Lak e Laut Taw ar, w hich are affect ed by deforest at ion and agricult ural land conv ersions ( Muchlisin et al 2010) . The sedim ent sam ples w ere collect ed from May t o June in 2012 at 5 st at ions in Lak e Laut Taw ar at t he dept hs of 1. 2 t o 2. 4 m et ers: Klit u ( N 4° 38’16” : E 96° 54’04” ) , Bint ang ( N 4° 35’31” : E 96° 59’35” ) , Tow eran ( N 4° 36’19” : E 96° 53’49” ) , Boom ( N 4° 37’50” : E 96° 51’33” ) and Uj ung Mum par ( N 4° 37’44” , E 96° 56’39” ) ( Figure 1) .
Figur e 1. The m ap of t he st udy area shows t he sam pling locat ions: Boom , Klit u, Uj ung Mum par, Bint ang, and Toweran.
Se dim e n t a na lysis. The sam ples w ere t ak en by using a grab sam pler of sedim ent , and t hen w ere dried t o rem ov e t he m oist ure. Approx im at ely 500 g of dried sam ples w ere t ak en and t hen siev ed using six lev els of siev e m esh size: 4. 75 m m , 1. 7 m m , 0. 85 m m , 0. 25 m m , 0. 15 m m and 0. 063 m m . The ret ained sam ples in t he respect ive m esh sizes w ere w eighed using a digit al balance. Grain size dist ribut ion analy sis consist s of m ean (xa) , sort ing (σa) , sk ew ness (Ska) , and k urt osis (Ka) deriv ed from a st at ist ical approach
and m om ent m et hod following Friedm an ( 1961) :
Where, f is w eight frequency ( % ) in each class, mm is m edian in each class.
Based on Folk & Ward ( 1957) t he sort ed condit ion is cat egorized at sev en lev els: < 0. 35 is v ery w ell sort ed, 0. 35- 0. 50 is w ell sort ed, 0. 50- 0. 70 is m oderat ely w ell sort ed, 0. 70-1. 0 is m oderat ely sort ed, 70-1. 0- 2. 0 is poorly sort ed, 2. 0- 4. 0 is very poorly sort ed, > 4. 0 is ex t rem ely poorly sort ed. Furt herm ore, t he skew ness v alues were divided int o fiv e lev els: st rongly fine sk ew ed ( > + 0. 3) , fine sk ewed ( + 0. 3 t o + 0. 1) , near sy m m et rically ( + 0. 1 t o – 0. 1) , coarse sk ew ed ( - 0. 1 t o - 0. 3) and st rongly coarse sk ew ed ( < - 0. 3) .
Re su lt s a n d D iscu ssion
Se dim e n t ological ch a ra ct e rist ic. The result s show ed t hat grav el w as predom inant at t he four locat ions Klit u, Uj ung Mum par, Bint ang and Tow eran, w hile Boom w as dom inat ed by m ud. The st udy show ed t hat t he percent age of grav el w as higher in Uj ung Mum par ( 98. 80% ) and t herefore t he sedim ent t y pe in t his locat ion w as classified as grav el. The t y pe of sedim ent sam ples w ere defined by t he Folk t riangle ( Folk 1974) and t hus fall int o t he cat egories of grav elly m ud, sandy grav el, and grav el, as show n in Table 1. All param et er v alues obt ained for t he grain size dist ribut ion param et ers t hrough t he st at ist ical and m om ent m et hods are present ed in Table 2.
Table 1 Grain size dist ribut ion according t o sam pling locat ions
Weight percent age frequency ( % ) St at ion
> 4.75 1.7- 4.75 0.85- 1.7 0.25- 0.85 0.15- 0.25 0.063- 0.15 < 0.063 Ty pe
Boom 9. 13 8. 37 2. 85 2. 66 0. 95 1. 52 74. 52 Gravelly m ud
Klit u 45. 65 17. 67 13. 41 20. 78 1. 55 0. 8 0. 14 Sandy gravel
U. Mum par 92. 05 6. 75 0. 64 0. 33 0. 06 0. 09 0. 08 Gravel
Bint ang 42. 95 22.17 10. 98 13. 33 7. 56 2. 61 0. 4 Sandy gravel
Tow eran 44. 21 12. 73 6. 6 22. 89 5. 73 6. 94 0. 9 Sandy gravel
Table 2 Grain size st at ist ical analy sis
St at ion Mean Sort ing Skew ness Kurt osis
Boom 0. 8183 1. 5938 - 0. 0848 4. 8029 Klit u 3. 1417 1. 9135 - 0. 7347 1. 3731 U. Mum par 4. 8304 0. 6269 - 3. 1983 24. 0817
Bint ang 3. 0940 1. 9216 - 0. 7742 1. 4789 Tow eran 2. 8508 2. 1046 - 0. 6154 1. 2000
Received: 04 May 2 015. Accept ed: 03 June 2 015. Published on line: 15 June 2 015. Aut hor s:
Syahr ul Pur nawan, Depar t m ent of Mar ine Sciences, Facult y of Mar ine and Fisher ies, Syiah Kuala Univer sit y, Jl. Put r oe Phang, Kopelm a Dar ussalam , Banda Aceh, I ndonesia, 2 3111, e- m ail: syahr ulpur nawan@unsyiah. ac. id I chsan Set iawan, Depar t m ent of Mar ine Sciences, Facult y of Mar ine and Fisher ies, Syiah Kuala Univer sit y, Jl. Put r oe Phang, Kopelm a Dar ussalam , Banda Aceh, I ndonesia, 2 3111, e- m ail: ichsan. set iawan@unsyiah. net Zainal A. Muchlisin, Depar t m ent of Aquacult ur e, Facult y of Mar ine and Fisher ies, Syiah Kuala Univer sit y, Jl. Put r oe Phang, Kopelm a Dar ussalam , Banda Aceh, I ndonesia, 2 3111, e- m ail: m uchlisinza@unsyiah. ac. id lizadam at @gm ail. com
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