CATEGORIZATION
OF BIOLOGICAL WATER QUALITY USING DIATOMS ON EXAMPLE OF
NICOLLE PAVLIK1, JöRN
KASBOHM1,
ĐẶNG DIỄM HỒNG2, LÊ THỊ LÀI3,
1Institute of
Geography and Geology, Greifswald, Germany;
2Institute of Biotechnology, VAST, Hà
Nội, Việt
Nam;
3Institute of Geological Sciences, VAST, Hà
Nội, Việt
Nam
Abstract:
In
I. INTRODUCTION
The
investigation of the water quality in settlements of province
II. STUDY AREA
For the analysis of the diatom population
suitable water bodies were selected in
III. CLIMATE
IV. METHODS AND MATERIALS
In research as also in practice diatoms are
used for evaluation of water bodies since beginning of 20th century.
Diatoms react on environmental change with characteristic shifts in the species
assemblage as in the relative frequency of species. They are very practical as
bio indicators because they react immediate and sensitive on several physical,
chemical and biological changes in different habitats. Diatoms present the
largest and most wide spread species of algae in water bodies. In every season
they are present abundant and species-rich in all aquatic and wet sub aerial
habitats. They make up the bulk of biomass in those habitats [21].
Diatoms are used mainly to characterize the
trophic state and the saproby system of lentic or flowing water bodies [21,
23]. They are also used to estimate several other parameters as temperature and
oxygen content [2], salinity [6, 25] as also pH value and acidification,
respectively [6, 22].
The methods are based on the fact that
different organisms prefer different environmental conditions. Each organism
has its own ecological niche. If the demands on water are known for different
organisms, they can be used as bio indicators for evaluation of water bodies.
Rott et al. [19] developed a saproby index for
phytobenthos that is calculated according to the formula by Zelinka &
Marvan [24] and shows analogies to the water quality categories of the saproby
system.
In this paper we present the saproby index for
processing the diatom population. This index is an empirical derived value
representing the relation between waters contamination and the biological
populations. With this index water quality categories are determined.
SI: saproby
index
Si: saproby
value of taxoni
Gi:
indication weighting of taxoni
Ni:
abundance of taxoni
n: number of
taxons
The determination of the
abundance (relative frequency) of single algae species is required for
quantification and characterization of the taxa in the investigated water
bodies. The
correlation according to Tumpling et al. (1999) is essential:
0 £ Ni £1
Ni : abundance of
taxoni
Si : number of
valves of taxoni
Stotal : total
number of determined valves
The
classification results in 4 water quality categories that are additional subdivided
into 3 sublevels. The following explanations of water quality categories are
mainly based on Rott et al. [19] and Lawa [16].
Water
quality category I is characterized by non to very low contamination by organic
materials and their decomposition products. The water is nearly saturated with
oxygen and content of nutrients is low. The BSB5 is 1.0 mg/l, NH4
appears only in traces. The minimum for O2 should exceed 8.0 mg/l.
The water body should be populated with alga and larvae.
Water quality category I-II is
characterized by low contamination by organic
materials and their decomposition products that do not cause any remarkable
oxygen depletion. The BSB5 ranges between 1.0 and 2.0 mg/l, NH4-N
approximately 0.1 mg/l. The minimum for O2 should exceed 8.0 mg/l.
The population of the water body shows high density and high biodiversity.
The general character of water quality category II
is defined by a modest contamination by organic material and their
decomposition products, a good oxygen supply and a very high species diversity
and individual density of alga. The oxygen content shows
strong fluctuations due to waster water load and alga development, the mean
value is 6.0 mg/l. The maximum content of ammonium is 0.3 mg/l, the BSB5
ranges from 2.0 to 6.0 mg/l.
The water quality category
II-III includes also water body sections with a higher charge of oxygen
depleting organic materials, which can muddy the water slightly. The oxygen
content in the water body declines to 50 % of the saturation value, ammonium is
below 1.0 mg/l, BSB5 ranges between 5.0 and 10.0 mg/l.
The water quality category III
is characterized by high contamination of the water body by organic materials
and their composting products. Digested sludge appears localized. The value of
BSB5 ranges between 7.0 and 13.0 mg/l, NH4-N values range from 0.5
to several mg/l. The oxygen content is low with a minimum exceeding 2.0 mg/l.
The abundance of waste water bacteria exceeds alga and plant populations.
Water quality category III-IV
is characterized by high to very high contamination by organic materials and
their decomposition products. Turbidity caused by suspended solids from waste
water is often observed, living conditions are limited. The value of
BSB5 ranges between 10.0 and 20.0 mg/l, NH4-N amounts to
several mg/l. From time to time total oxygen loss appears, the O2 is
below 2.0 mg/l, sediments of digested sludge appear extensive.
Water quality category IV is
characterized by a very high contamination by organic material and their
decomposition products. Decomposition processes are predominant. The BSB5
value exceeds 15.0 mg/l, NH4-N value amounts to several mg/l. The
oxygen content is very low during a long period of time or even zero. The O2
minimum is below 2.0 mg/l. Bacteria are predominating, additional toxic charges
lead to total biological desolation.
Between 06.12.2006 and 21.12.2006 phytoplankton as
well as phytobenthos was sampled and tested. For sampling of phytobenthos, a
plankton net with a mash width of 20 µm was used. The plankton net was fixed to
a rope and thrown into the water body. After it sank below the water surface it
was reeled in again immediately. Subsequent the sample was filled into a sample
bottle.
For the sampling of the phytobenthos a glass was
fixed on a rope with a stone for submerging. After it was thrown into the water
body the glass sank to the ground and was careful pulled across the bottom. The
collected phytobenthos was filled in a sampling bottle, subsequent. The
sampling procedure was repeated until 400 ml of sample were collected. The
sample was preserved immediately with 50 ml formaldehyde (4 vol. %),
subsequently.
According to Kelly [8, 9] for a reliable interpretation of environmental
conditions of water bodies repeated, timed samplings over many years are
necessary. This is important to capture the total variability at a sampling
point.
For the analysis the preserved samples had to be
concentrated. Therefore after 24 h settling time, excess water was removed.
Afterwards the concentrated sample was transferred to another sample bin. The
microscopic analysis of single diatom species was conducted on microscope Leica
DMSL with 10x and 12,4x oculars and 10x, 20x, 40x and 100x lenses. The sample
was pipetted onto a sample holder and covered with a glass cover. The diatoms
were classified mainly according to Cox [3] and Nguyen [18] but also
according to Krammer & Lange-Bertalot [10, 11] and
Lange-Bertalot [14].
For counting the diatoms and non-diatoms
Neubauer-counting chamber with a chamber depth of 0.1 mm was used. During the
counting single valves (eptheca, hypotheca) of the frustules and girdles were
determined. Diatoms with not-determinable girdles or valves were classified
according to the genus. Broken pieces were only recognized if their size was
> 50% of the original part. Statistical means were calculated based on 3
countings of one diatom sample.
Because micro-organisms react
rapidly on changes in environmental conditions the analysis of non-fixed
samples after a time-lag of several days can cause incorrect results [1]. The identification and the
counting of species and genus of the diatom population should be conducted
immediately after sampling in non-fixed condition. This avoids problems in the
identification of diatoms by changed appearance of e. g. chloroplasts due to
conversation.
V.
In the samples of
For the
investigated section of
The results reveal a high
species diversity of diatoms in
The application of the saproby
index in combination with the general applied parameters for evaluation of
water quality categories is a progress of the method. For lentic water bodies
in Việt
We observed that diatoms are very suitable to
evaluate the water quality category of water bodies, especially bodies of
flowing water, in Việt
VI. FIGURES AND TABLES
Table 1. Categorization of saproby index (SI) and potential analogies to water quality categories (according to Lawa [16, 19]).
|
Saproby index SI |
Saproby level |
Contamination |
Water quality category |
Mapping colour according to [16] |
|
1,0 - 1,34 |
oligosaprobic |
low to
very low |
I |
Dark blue |
|
1,35 -
1,74 |
oligo- to β-mesosaprobic |
low |
I - II |
Light blue |
|
1,75 -
2,14 |
β-mesosaprobic |
modest |
II |
Blue green |
|
2,15 -
2,54 |
β-α-mesosaprobic |
modest to
strong |
II - III |
Yellow
green |
|
2,55 -
3,04 |
α-mesosaprobic |
strong |
III |
yellow |
|
3,05 -
3,44 |
α-meso- to polysaprobic |
strong to
very strong |
III - IV |
orange |
|
3,45 - 4,0 |
polysaprobic |
very
strong |
IV |
red |
Table 2. Water
quality categories of water courses (according to [16, 19])
|
Water quality category |
Saproby index SI [19] |
BSB5 (mg/l) |
NH4-N (mg/l) |
O2-Minima (mg/l) |
|
I |
1,0 - 1,34 |
1,0 |
in traces |
> 8,0 |
|
I - II |
1,35 -
1,74 |
1,0 - 2,0 |
approx.
0,1 |
> 8,0 |
|
II |
1,75 -
2,14 |
2,0 - 6,0 |
< 0,3 |
> 6,0 |
|
II - III |
2,15 -
2,54 |
5,0 - 10,0 |
< 1,0 |
> 4,0 |
|
III |
2,55 -
3,04 |
7,0 - 13,0 |
0,5 to
several mg/l |
> 2,0 |
|
III - IV |
3,05 -
3,44 |
10,0 -
20,0 |
several
mg/l |
< 2,0 |
|
IV |
3,45 - 4,0 |
> 15,0 |
several
mg/l |
< 2,0 |