Tp ch: Khoa hc t, ISSN 0868-3743, s 37nh hng ca cht lng nc n a
dng sinh hc to ct sng bm trn mt s h thng mng thy li Trnh Quang
HuyNguyn Th Thu H(1)(1) B mn Cng ngh mi trng, khoa Ti nguyn v Mi
trng, trng H Nng nghip HN1. GII THIUTrong mi trng sng, mi loi sinh
vt c yu cu nht nh v iu kin sinh thi lin quan n nhu cu dinh dng, hm
lng oxi cng nh kh nng chng chu mt lng nht nh cc yu t c hi trong mi
trng sng v do s hin din ca chng biu th mt tnh trng v iu kin mi trng
sng. S hin din v c trng ca cc loi sinh vt ny biu th cht lng mi trng
nm trong gii hn nhu cu v kh nng chng chu ca sinh vt . i vi mc ch nh
gi cht lng nc, hin nay c kh nhiu loi sinh vt ch th c pht hin v ng
dng thnh cng nhiu vng trn th gii. Cc nhm sinh vt thy sinh thu ht
nhiu s quan tm ca cc nh nghin cu ch th sinh hc l ng vt ni, ng vt y,
c v cc nhm to trong c to ct sng bm.To ct sng bm c u im hn so vi cc
nhm sinh vt khc ch chng l loi sinh vt d thu mu, thnh phn loi v mt
ca chng c nhiu nh khoa hc trn th gii nghin cu lm c s cho vic xy dng
ch th sinh hc. Tuy nhin, mi loi sinh vt ch th c c im thch ng v phn
b khc nhau nn mt i tng c kh nng lm sinh vt ch th vng ny th cha chc
thch hp lm sinh vt ch th ti vng khc. Kh khn trc mt khi ng dng sinh
vt ch th ti Vit Nam cng nh nhiu nc thuc vng nhit i l ch cc h thng
phn loi nhim bn cc thu vc theo ch th sinh hc u l nhng dn liu c
nghin cu vng n i, hon ton khc vi iu kin t nhin cng nh c tnh sinh hc
ca cc thu vc nc ta. Bn cnh , nh gi phn ng ca sinh vt i vi iu kin mi
trng bin ng lin tc ca cc h thng thy li l mt qu trnh kh khn v phc
tp. Trong yu cu xy dng mt b ch th sinh hc s dng to ct nh gi cht lng
nc vng nng thn, th yu t tin quyt l phi xc nh c mi quan h gia sinh
vt v mi trng trc ht l nh gi c phn ng ca khu h sinh vt vi iu kin mi
trng lun lun bin ng. 2. I TNG V PHNG PHP NGHIN CUNghin cu ny c p
dng nh gi a dng sinh hc trn cc h thng knh mng in hnh cho loi hnh h
thng thy li vng nng thn ng bng Sng Hng (h thng Bc ung v h thng Bc
Hng Hi). Mu nc v mu to ct c thu thp trn mt s v tr thuc mi h thng
knh mng c trng cho loi ngun thi c trng ca vng nng thn: nc thi canh
tc la, nc thi sinh hot, chn nui nh gi cht lng nc: ly 3 im i din trn
mi on mng, s dng phng php ly mu nc mt theo TCVN 5996-1995. Tn sut
ly mu 1 tun/ln i vi mu nc v mu to, thi gian quan trc 52 tn t thng
2/2009 n thng 2/2010. Cc thng s phn tch gm: DO, pH, Eh c o trc tip
ti hin trng; BOD5 c xc nh bng phng php nui cy; COD c xc nh bng phng
php chun ; N-NH4+ c xc nh bng phng php so mu Nessler; N-NO3- c xc
nh bng phng php so mu; P-PO43- c xc nh bng phng php Oniani. To ct c
thu thp v x l theo quy trnh phn tch a dng sinh hc to ct nc ngt ca
Nht Bn. Thu thp mu to: Bng by to bm vi din tch b mt 0,03 m2X l s b:
Chuyn ton b sinh khi to vo nc, bo qun bng fomalin 10%Xc nh mt to:
Mt to ct c xc nh bng phng php soi m ti theo tiu chun ca APHA, 10300
mc C vi knh hin vi quang hc phng i ca vt knh: 40x. X l mu lm tiu bn
gm cc bc oxy ha v lm sch mu v lm tiu bnnh loi to bm: c thc hin vi
tiu bn theo tiu chun phn tch ca APHA, 10300 mc D di knh hin vi
quang hc phng i ca vt knh l 100xnh gi to ct da vo cc ch s a dng: Ch
s a dng bnh qun (H): H Shannon-Weaner (1949), Mt s ch s a dng (D):
D Simpson (1949), D Margalef (1958), D Odum (1960), D Menhinick
(1964), Ch s giu loi (E): E Pielou (1966) v ch s u th (C): C
Simpson (1949).3. KT QU V THO LUN3.1. Cht lng nc cc h thng knh mng
thy liTrn cc h thng knh mng thy li Bc ung v Bc Hng Hi, la chn cc
mng ch nhn nc thi canh tc, nc thi chn nui v nc thi sinh hot. Gi tr
trung bnh ca cc thng s quan trc trong 52 tun c trnh by trong bng
1:Bng 1. Cht lng nc cc h thng mng nhn nc thi khc nhau:Loi ngun
thiThng sNc thi canh tcNc thi chn nuiNc thi sinh hot
Bin ngTBBin ngTBBin ngTB
pH6,328,087,280,416,828,317,410,316,818,187,330,77
Eh (mV)-2429017662-13427614980-197236109105
DO (mg/l)1,207,523,441,521,227,143,571,530,677,052,741,58
N-NH4+
(mg/l)0,0120,52,804,080,4320,85,024,200,1328,97,446,81
N-NO3-
(mg/l)0,031,050,200,210,041,300,320,340,010,750,210,15
P-PO43-
(mg/l)0,011,460,360,320,022,530,700,620,042,060,620,48
BOD5 (mg/l)1,833,816,55,89,959,024,49,98,451,920,78,4
COD (mg/l)161295425171586226161576131
Ghi ch: Khong bin ng biu din bng: gi tr nh nht gi tr ln nhtGi tr
trung bnh biu din bng: trung bnh lch chunCht lng nc cc h thng knh
mng thy li thuc h thng Bc ung v h thng Bc Hng Hi c tnh cht tng t
nhau trong h thng Bc ung (h thng knh mng thy li ni ng x Ph ng) c
cht lng tt hn. Trong , nc thi chn nui v nc thi sinh hot nh hng ti
cht lng nc trong h thng knh mng nghim trng hn c bit l i vi hm lng
cht hu c (BOD5 v COD) trong khi dinh dng ha tan ca nc (Nit, Photpho
c bit dng NH4+ v PO43-) c th do nh hng ca phn bn trong nc thi canh
tc la.3.2.1 Cu trc khu h to ct sng bm ti cc h thng knh mng Trn hai
h thng knh mng trong sut thi gian nghin cu c c tng s 131 loi xut
hin thuc v 22 chi vi hai lp chnh: To ct trung tm (Centrales) v To
ct lng chim (Pennales). Trong c 05 loi (02 chi Thalasiosira v
Cyclotella chim 3,82%) thuc To ct trung tm; 126 loi (20 chi cn li
chim 96,18%) thuc To ct lng chim. Bng 2. S lng loi xut hin trn cc h
thng knh mng nghin cuSttTn chiLoi nc thi nh hng n mng
Canh tc laChn nuiSinh hotTon khu vc
1Navicula25172129
2Nitzschia22202728
3Gomphonema14101317
4Pinnularia831112
5Achnanthes6456
6Amphora4324
7Eunotia4134
8Stauroneis414
9Cyclotella3333
10Gyrosigma1223
11Surirella313
12Caloneis2112
13Cymbella22
14Diploneis12
15Encyonema22
16Frustulia212
17Synedra212
18Thalasiosira2212
19Cocconeis11
20Hantzschia111
21Peronia11
22Plagiotropis111
Tng1086698131
Trong s cc chi xut hin trn a bn nghin cu, a dng nht v thnh phn
loi l Navicula vi 29 loi, tip l Nitzschia vi 28 loi, Gomphonema vi
17 loi, Pinnularia vi 12 loi v Achnanthes vi 6 loi. 5 chi a dng nht
k trn bao gm 92 loi chim n 70,23% s loi xut hin. Cc chi cn li nh
Eunotia, Stauroneis, Cyclotella, Surirella, Frustulia, Peronia,
Thalasiosira xut hin vi s lng loi hn ch hn (thng ch gm t 1 n 4 loi
trong mt chi). Trong s 131 loi xut hin c 111 loi chim 84,73% c ghi
nhn l cc loi c phn b a l rng t n i n nhit i. Khi xem xt ng thi c
tnh a dng v loi v tnh phong ph v s lng c th xut hin trn a bn nghin
cu, c th xc nh c cc nhm to ct ng vai tr quan trng trong cu trc khu
h to ct sng bm l Nitzschia, Navicula, Gomphonema, Achnanthes,
Pinnularia, Cyclotella, k n l Amphora, Eunotia, Cymbella,
Thalasiosira Trong ton b thi gian quan trc s lng loi xut hin cc h
thng knh mng khng ging nhau. H thng Bc Hng Hi gm 108 loi trong khi
h thng Bc ung gm 112 loi xut hin. Trong , cc mng nhn nc thi canh tc
la a dng nht v thnh phn loi vi 118 loi xut hin (20 chi, khng tm thy
s xut hin ca Cymbella v Diploneis). Mng nhn nc thi chn nui c s lng
loi thp nht (vi 66 loi thuc v 11 chi). Ti mng tiu nhn nc thi sinh
hot ghi nhn s xut hin ca 98 loi (thuc v 19 chi, trong khng c s xut
hin ca Encyonema, Cocconeis v Peronia). ng vi cht lng nc ca cc khu
vc nghin cu, khi cht lng nc bin ng t nhim bn dinh dng v c n nhim bn
dinh dng hu c, quyn u th tnh theo chi s thay i theo xu hng sau y:
Chi khc Gomphonema Navicula/Nitzschia Achnanthes Cyclotella. Cc loi
xut hin u th (t 9,1 n 2,8%) trn h thng thy li Bc Hng Hi l Nitzschia
frustulum, Cyclotella meneghiniana, Nitzschia palea, Amphora
libyca, Cyclotella atomus, Gomphonema pseudoaugur, Nitzschia
fonticola, Navicula sp.-1, Gomphonema clavatum, Navicula
cryptocephala v Navicula cryptotenella. Trong khi , trn h thng Bc
ung gm nhiu (t 21,5 n 2,4%): Cyclotella meneghiniana, Nitzschia
palea, Navicula sp.-1, Navicula subminuscula, Achnanthes exigua,
Nitzschia fonticola, Nitzschia frustulum, Amphora montana v
Gomphonema parvulum var.parvulum. i vi nc thi t hot ng canh tc, cc
loi u th (14 n 3%) l: Nitzschia frustulum, Nitzschia palea,
Nitzschia fonticola, Navicula cryptocephala, Gomphonema
pseudoaugur, Navicula cryptotenella, Amphora libyca, Eunotia
binularis, Gomphonema clavatum v Nitzschia capitellata. i vi nc thi
giu hu c, cc loi u th l: Cyclotella meneghiniana, Nitzschia palea,
Navicula sp.-1, Achnanthes exigua, Cyclotella atomus, Nitzschia
fonticola, Nitzschia frustulum, Navicula subminuscula, Amphora
libyca, Gomphonema parvulum var.parvulum, Gomphonema parvulum var.
lagenula.Nh vy, nu ch xt n vn ngun thi i vo trong i tng mi trng nc,
c th nhn thy rng cc loi Cyclotella meneghiniana, Nitzschia palea,
Achnanthes exigua, Cyclotella atomus, Nitzschia fonticola,
Nitzschia frustulum, Gomphonema parvulum var. lagenula l cc loi
chng chu tt ti cc mi trng c mc nhim hu c cao. Trong khi Nitzschia
frustulum, Navicula cryptocephala, Navicula cryptotenella,
Gomphonema pseudoaugur, Amphora libyca, Eunotia binularis,
Gomphonema clavatum v Nitzschia capitellata c th l nhng loi thch
nghi hn vi iu kin nhim hu c thp trong khi nng cc cht dinh dng N v P
c th mc trung bnh n cao. Trong sut ton b thi gian quan trc, mt to
ct trung bnh l 17.712 t bo/m2 dao ng trong khong 200 n 197.600 t
bo/m2 trong cao nht h thng knh mng nhn nc thng xuyn t sng ung (M3
trung bnh 22.300 t bo/m2) thp hn h thng knh mng nhn nc t sng Cu By
(M1 trung bnh 14.200 t bo/m2) v thp nht h thng knh mng khng c s
trao i nc thng xuyn vi h thng thy li chnh ca khu vc (M2 trung bnh
7.600 t bo/m2). Mt t bo to c s khc bit ng k gia cc v tr tin hnh ly
mu: gi tr mt rt thp ca cng thi c ngun gc chn nui hoc sinh hot
(trung bnh 4.200 t bo/m2) kh cao nhng vc gn ngun cp nc v d u cc trm
bm (trung bnh 16.800 t bo/m2) v cao nht cc vng nc n nh vi trong cao
v dng chy chm (24.600 t bo/m2). Theo thi gian, mt to ct c s bin ng
ng k gia cc i tng v v tr quan trc, v d: i vi cc mng nhn nc thi sinh
hot v chn nui, mt cao nht thng xy ra vo ma H, ti nhng thi im ny cng
ghi nhn v bng n mt ru to khin cho nc mu xanh, c vng.
Hnh 1. Bin ng v mt to ca cc i tng nghin cu theo thi gianTrong
thi gian 52 tun quan trc, s lng loi xut hin c s khc bit ng k theo
thi gian. Trong ma Xun c 112 loi, s lng loi trung bnh xut hin trn
mt mu l 43 loi dao ng trong khong 24 n 64. Ma H c s lng loi dao ng
trong khong 27 n 61, trung bnh l 40 loi, tng s loi xut hin trong ma
l 108. Trong ma Thu xut hin trung bnh 36 loi (16 52) vi tng s 89
loi. Ma ng xut hin s loi t nht vi tng s 77 loi, trung bnh 31 loi ti
mt thi im quan trc (dao ng trong khong 16 n 56). Do nh hng ca ch cp
nc, mt s loi to ct ch xut hin vo mt ma nht nh trong nm, nhng thi
gian khc khng tm thy s xut hin ca chng hoc s xut hin ca chng l khng
ng k. Cc loi to ct tiu biu cho thi im cp nc thy li (u Xun v cui H)
l Diploneis eliptica, Frustulia rhomboides, Gomphonema affine, G.
gracile, G. parvulum, G. subclavatum, Nitzschia gracilis, Nit.
nana, Nit. perminuta, Peronia fibula, Pinnularia acrosphaeria, P.
braunii, P. lundii, P. subcapitata v Surirella linearis. iu ny c th
c gii thch bng c im sinh hc v sinh thi hc mi trng ca cc loi ny, a s
chng u l cc loi nhy cm. Theo thi gian hoc theo chiu dng chy, khi
cht lng nc suy gim, cc loi ny suy gim hoc b tiu dit nhng ch cho cc
loi khc thch nghi hn.Ngc li vi xu hng bin ng ca cc loi nhy cm vi
nhim theo ma, cc loi chng chu tt vi nng oxy thp, dinh dng v c v hu
c cao li c xu hng gia tng vo cui Thu n u Xun nm sau. Trn thc t, kh
nng xut hin hin cng nh mt ca chng hu nh khng c s thay i ng k theo
thi gian quan trc gm: Achnanthes hungarica, Cyclotella
meneghiniana, Gomphonema pseudoaugur, Navicula goepertiana, N.
gregaria, N. minima, N. seminulum, N. subminuscula, N. venata,
Nitzschia acicularis, Nit. capitellata, Nit. palea v Nit. umbonata.
3.3. Hin trng v bin ng mc a dng sinh hc to ct Bin ng mc a dng ca tt
c cc mu thu thp c trn ton b chng trnh quan trc (137 mu) khc nhau cc
loi ch s khc nhau. a dng trung bnh (H) ca khu h to ct dao ng trong
khong 1,87 n 4,94 c bin ng (CV% c tnh bng phn trm lch chun chia cho
gi tr trung bnh) l 17,29%. Ch s a dng tnh theo Margalef bin ng
khong 32,93%; tnh theo Menhinick l 75,22%; theo Odum l 28,49%; theo
Simpson ln lt l 8,5 v 43,9%. Ch s bnh qun cc qun th c lin quan n kh
nng xut hin cc loi u th (E) theo Pielou c bin ng 11,17%. Cui cng l
ch s u th ca Simpson bin ng trong khong 57,57%. Bng 3. Kt qu cc ch
s a dng sinh hc nh gi cht lng khu h toCh sTrungbnhKhongbin ngTheo
ngun nc thiTheo ma
CTCNSHXunHThung
Shannon-Weaner3,89 0,671,87 4,944,303,753,654,134,103,833,54
D Margalef11,0 3,633,69
23,9011,7611,3910,0213,5911,3110,179,16
D Menhinick0,94 0,710,06 3,960,651,420,771,330,900,820,75
D Odum0,38 0,110,16 0,640,450,330,350,440,400,360,32
D Simpson 10,87 0,070,55 0,960,910,860,850,890,900,870,83
D Simpson 211,2 4,922,24
22,214,4810,648,7913,0612,1211,009,11
E Pielou0,75 0,080,47 0,890,790,750,710,760,780,750,71
C Simpson0,13 0,070,04 0,450,090,140,150,110,100,130,17
Ghi ch: CT = Canh tc, CN = Chn nui, SH = Sinh hotKt qu c tnh ton
vi tng s mu n = 137Gi tr trung bnh biu din bng: trung bnh lch chun
Khong bin ng biu din bng: gi tr nh nht gi tr ln nhtTheo thi gian
quan trc, ma Xun v ma H thay nhau l ma c mc a dng sinh hc cao hn so
vi hai ma cn li v l nhng ma c mc a dng sinh hc cao nht trong nm. iu
ny ph hp vi quy lut pht trin ca to ni ring v sinh vt sn xut ni
chung do thi gian ny trong nm c nhit , nh sng v cc iu kin khc m bo
tt nht cho s pht trin ca thc vt. Nhiu ti liu khc cng ghi nhn kh nng
n hoa ca to nc ngt (trong to lam, to lc, to ct l nhng nhm quan
trng) cao nht vo cui Xun cho n cui H. Nhng thi im khc trong nm bt u
t cui ma thu, mt mt iu kin mi trng khng phi l nhng thi im thch nghi
nht ca to, mt khc do khng c qu trnh cp nc mi vo h thng thy li, nn a
dng sinh hc ca to ct suy gim ng k. Khi cht lng nc suy gim, a dng
sinh hc ca hu ht cc h thng knh mng u gim trong khi mc u th ca mt
nhm loi li tng. iu ny chng minh cho gi thuyt t ra ban u trong nghin
cu ny, l tn ti cc loi to ct u th c kh nng ch th cho cht lng nc cc h
thng knh mng thy li trn.Nh vy, hin trng a dng sinh hc ph thuc cht
ch vo loi ngun thi hay ni chnh xc hn l ph thuc vo cht lng nc ca h
thng knh mng thy li. iu ny ng ngha vi vic cht lng nc mc tt (mng nhn
nc thi canh tc) gm a dng v phong ph cc loi nhy cm v ngc li, cht lng
nc mc trung bnh n xu gm phong ph cc loi chng chu tt vi nhim hu c
(nc thi sinh hot v chn nui).Bng 4. Danh mc cc loi u th cc loi hnh
thy vc nhn nc thi khc nhauLoi ngun thi nh hng n cht lng nc mng
Nc thi canh tc(n = 16; < 0,1)Nc thi sinh hot(n = 42; <
0,05)Nc thi chn nui(n = 78; < 0,05)
Diploneis elipticaAchnanthes lanceolataAchnanthes hungarica
Frustulia rhomboidesCocconeis linearisCyclotella
meneghiniana
Gomphonema affineNavicula gregariaNavicula confervacea
Gomphonema gracileNavicula pupulaNavicula goepertiana
Gomphonema parvulumNavicula venataNavicula minima
Gomphonema subclavatumNitzschia acicularisNavicula seminulum
Nitzschia gracilisNitzschia amphibiaNavicula subminuscula
Peronia fibulaNitzschia inconspicuaNitzschia filiformis
Pinnularia acrosphaeriaNitzschia paleaceaNitzschia palea
Pinnularia brauniiNitzschia trybliformisNitzschia sigma
Pinnularia subcapitataPinnularia mesoleptaNitzschia umbonata
Surirella linearisStauroneis phoenicenteronPinnularia gibba
4. KT LUN V KIN NGHVi 131 loi to ct xut hin, trn a bn Gia Lm
trong thi gian 1 nm nhn thy c nhng bin ng ng k v cu trc khu h v a
dng nm mc trung bnh n cao. a dng sinh hc cao nht v ma Xun, H v nhng
thi im thp nht thng ri vo ma Thu, ng do kh ph hp vi bin ng cht lng
nc theo thi gian v i tng nghin cu. M phng cht lng nc thng qua cc ch
s a dng c nh gi l kh ph hp vi cc iu kin mi trng h thng knh mng la
chn. Trong c hai h thng Bc ung v Bc Hng Hi u c mc a dng sinh hc cao
tng ng vi s lng loi xut hin trong 52 tun quan trc cao (tng ng 112 v
108 loi). a dng sinh hc cao nht knh mng nhn nc thi canh tc v thp
nht knh mng nhn nc thi chn nui v sinh hot cho thy khi cht lng nc
tt, a dng sinh hc cao v ngc li. Trong , lng hu c nh hng nghim trng
n cc loi nhy cm trong khu h to ct.
TI LIU THAM KHO1. American Public Health Associations (APHA),
American Water Works Association (AWWA) and Water Pollution Control
Federation (APCF), Standard Methods for the Examination of Water
and Wastewater, 18th edition, APHA, Washington, D.C, 19922. Choi Je
Sin, Park Jung Won, Lee Kyung Lak, Yang Myung Sook, Kim Han Soon -
Seasonal Variation of Epilithic Diatom Community and an Assessment
of Water Quality by DAIpo in the Water System of Ulleung Island,
Department of Biology, Kyungpook National University, Daegu 701 -
702, Korea3. Guy Bate, Pat Smailes and Janie Adams - A Water
Quality Index for Use with Diatom in the assessment of river4.
Jenifer G.Winter and Hamish C.Duthie - Epilithic diatom as
indicator of stream total N and Total P concentration, 20005. Ruth
Patrick, Charles W. Reimer, The diatoms of the United States, The
Academy of Natural Science of Philadelphia, 19666. Taisuke Ohtsuka,
Sakae Kudoh, Satoshi Imura, Shuji Ohtani - Diatom composing benthic
microbial mats in fresh water, 20067. Winfried Lampert, Ulrich
Sommer - Limoecology The Ecology of Lakes and Streams
SUMMARY: Influence of water quality to biodiversity of epilithic
diatoms of some system of irrigation canalsBiodiversity of a
community is an important factor in building environmental
bioindicator. Diatoms were studied on a representative number of
canals for both irrigation systems Bac Hung Hai and Bac Duong. On
the whole monitoring period, including 112 species of diatoms on
the canal system Bac Duong and 108 species on Bac Hung Hai (total:
131 species) is the most widespread species. Spring and summer are
the time of highest biodiversity, but in the autumn and winter
often have lower levels of diversity. When good quality water
(canals receiving farm-wastewater), the dominant species of diatoms
are sensitive species. Conversely, when the irrigation system
receiving domestic-wastewater or animal-wastewater, pollution
tolerant diatoms are highly dominant species.
