Waterquality-bioindication versus chemical parameters, a study of the
river *la Sorge*, Lausanne, Switzerland.

Bossert Henri^†^, Gingins François^†^, Johannot Débora, Müller Anaïs,
Riat Carole, Seppey Bénédicte

Gymnase de Beaulieu, Switzerland

### Introduction.

Water is one of the most abundant and important substances on the Earth.
It constitutes 50 to 90 percent of the weight of all living organisms,
and sustains plant and animal life. Water plays a key role in the
formation of weather, helps to shape the surface of the planet through
erosion and other processes, and covers roughly 70% of the Earth\'s
surface.

Water continually circulates between the Earth\'s surface and its
atmosphere in what is called the hydrologic cycle (figure 1). The
hydrologic or water cycle, is one of the basic processes in nature.

Figure 1: The hydrologic cycle

![](media/image1.png){width="5.46875in" height="3.1770833333333335in"}

Water participates in many important chemical reactions, and most
substances are soluble in water. Due to its effectiveness as a solvent,
truly pure water rarely occurs in nature. Water carries many natural and
human-introduced impurities as it travels through the hydrologic cycle.
These impurities give each water its distinctive chemical makeup, or
*quality*.

### The studied site, description and situation.

During two months (april, may 2003), the sampling was done on a river in
the west of *Lausanne*: the *Sorge*. This river flows from the hill in
the north of *Lausanne* to the Lake of Geneva. It has a rocky bed and
its flow is approximately always the same, except when it rains either a
lot or not. During the dry season (july, august) it is nearly dry, and
in coldest winter time (January, february), the water can freeze for
some days.

For each river, the samplings were made in three different places; one
in the spring, an other in the middle and the last in the mouth of the
river. For the *Sorge*, the spring is in *Villars*
(46°33'17.2''N/6°34'14.3''E) the middle in *Ecublens* (46°32'24.1''N/
6°34'8.7''E) and the mouth in *Dorigny* (46°31'27.1''N/6°34'16.7''E).

### Working Method

Bioindication of saproby macroinvertebrates.

The study of macroinvertebrates living in water can be used to determine
the quality of this water. Each individual specie found in water is fed
on decomposed organic material or minerals present in the biotope. Thus,
they become representative for the presence of these materials in water.
The sensitivity of each specie against the level of pollution is
indicated by the saproby index, which is a characteristic value of the
specie. Typical saproby indexes of 1 to 1.8 are given for most sensitive
species that are found onely in very clean water. Indexes higher than
3.5 are given for the most resistant species that are found in very
highly polluted waters. The saproby degree (SD) is representative for
the quality of water and depends directly from the abundance and variety
of the fauna found that lives in (Table 1).

Table 1. Saproby degree (DS) and pollution level of water.

+-------------+-------------+-------------+-------------+-------------+
| #### Sap    | 1.0 -- 1.8  | 1.8 -- 2.7  | 2.7 -- 3.5  | 3.5 -- 4.0  |
| roby degree |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| ***Class of | I           | II          | III         | IV          |
| quality***  |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| ***Interp   | Clean       | Medium      | High        | Very high   |
| retation*** |             | pollution   | pollution   | pollution   |
+-------------+-------------+-------------+-------------+-------------+

Sampling of the macroinvertebrate fauna was performed in three different
places of the river (spring, middle, mouth). In every place, we gathered
a lot of small water invertebrate, lifting up the river's bed. As we
said, the individuals show the river quality.

Numbering and classification of individuals was performed in laboratory
using magnifying glass and microscope, to determine the number and the
genus and specie of each. Then an abundance index (AI) was attributed,
depending on the number of individual found for each specie (table 2). A
saproby index (SI) was assigned to each species, according to a value
table (table 3).

Table 2. Abundance index

  --------------- ------- ------- ------- ------- -------- --------- -------
  Nb. Of          1-2     3-10    11-30   31-60   61-100   101-150   \>150
  individuals                                                        

  Abundance index 1       2       3       4       5        6         7
  --------------- ------- ------- ------- ------- -------- --------- -------

Finaly the saproby degree which indicates the water quality was
calculated for each of our sampling spots on the *Sorge* river. For
this, the taxon value for each specie must be first calculated for each
place. The taxon value is found by multiplying the abundance index with
the saproby index. Then, the saproby degree (SD), which gave us the
water quality for each place is found by dividing the sum of the taxon
values by the sum of the abundance values (formula 1).

##### Σ (SI•AI)

SD = \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- (formula 1)

Σ AI

Table 2. Bioindication results and saproby degree for the river *Sorge*,
Lausanne (Switzerland)

  --------------- ----------------- ------- ------------ -------- ---------- ------------ -------- ---------- ----------- -------- ----------
  **Sampling                                **Villars                        **Écublens                       **Dorigny            
  place**                                   (spring)**                       (middle)**                       (mouth)**            

  **Order /       **Genus**         Sapr    Count        Abund.   Taxon.     Count        Abund.   Taxon.     Count       Abund.   Taxon.
  Family**                          index                index    value                   Index    value                  Index    value

  Gasteropodia    anisus                    1            1        0          0                     0          0                    0

                                                                                                                                   

  Crustacea       gammarus          2,1     306          7        14,7       60           4        8,4        30          3        6,3

                                                                                                                                   

  Annelida        tubifex           3,5     76           5        17,5                             0                               0

                  lumbriculus       3       0                     0          1            1        3          1           1        3

                                                                                                                                   

  Diptera         tipula                    5            2        0          0                     0          0                    0

                  chironomus        3,3     0                     0          0                     0          1           1        3,3

                  von dicranda              0                     0          0                     0          2           1        0

                  zuckmuckenlarve   3,3     0                     0          0                     0          4           2        6,6

                  f\. chironomida   3,3     0                     0          0                     0          17          3        9,9

                                                                                                                                   

  Ephemeroptera   ecdyonorus        1,7     6            2        3,4        0                     0          0                    0

                  baëtis            2,3     4            2        4,6        7            2        4,6        6           2        4,6

                                                                                                                                   

  Tricopterae     tinodes           2       1            1        2          0                     0          0                    0

                  rhyacophila       1       0                     0          0                     0          1           1        1

                  lepidostoma       1,9     18           3        5,7        0                     0          9           2        3,8

                  lymnephilidae             1            1        0          0                     0          0                    0

                                                                                                                                   

                  Total count                            24       47,9                    7        16                     16       38,5

                  **Saprobie                                      **2,00**                         **2,29**                        **2,41**
                  degree**                                                                                                         
  --------------- ----------------- ------- ------------ -------- ---------- ------------ -------- ---------- ----------- -------- ----------

Chemical analysis.

For the chemical measurement, Globe hydrology protocols were used. Water
temperature was measured directly in the water stream. Water alkalinity
was determined by the standard acid titration method, as describe in
Globe hydrology protocols. The water pH value was determined with pH
paper strips (Universalindikator pH 0-14, *Merck*, 1.09535.0001).
Dissolved oxygen values, were determined by using the tabulated values
depending from the water temperature and the altitude found in the Globe
hydrology protocols. For nitrate and nitrite, a paper strips nitrate
test kit (Nitrate--Nitrite Test, Quantofix, *Macherey-Nagel*) was used.
Finaly, all the measures were recorded in the GLOBE-database et plotted
with the GLOBE-graphs tool.

## **Analysis**

Water acidity, pH

Through the chemical experiences, we found that all the pH measures were
between 6.5 and 10, so the PH of the water varied between acidity and
basic water (see graph 1). The low pH episode corresponds to a rainy
period, so large amount of rain water was carried to the river. It is
known that rain water is slightly more acid, due to the presence of more
dissolved atmospheric carbon dioxyde.

Graph 1. pH of *la Sorge*

![](media/image2.png){width="3.933333333333333in"
height="3.0166666666666666in"}

Water alcalinity

Alkalinity of the water was situated between 200-450 mg/l CaCO~3~. The
plotted values for alkalinity show a dependance of the meteorological
conditions. During a rain period, the alkalinity level went down, due to
dilution of carbonates by large amounts of drained rain water (Graph 2).

![](media/image3.png){width="3.933333333333333in"
height="3.0166666666666666in"}

Graph 2. Water alcalinity

Water temperature

Temperatures varied between 8°C and 15°C, and average temperature is
around 13°C for this period. The graph shows that the water is colder at
the spring (Sorge 1) than in other places, and the temperature felt at
its minimun in may, when the weather was cold (Graph 3). All the rivers
we analysed were situated in a forest, so the sun couldn't easily shine
on it. That's why the temperature varied just a little.

Graph 3. Water temperature °C

![](media/image4.png){width="3.933333333333333in"
height="3.0166666666666666in"}

Dissolved oxygen concentration

Dissolved oxygen values were found from 9 mg/l to 13mg/l (Graph 4).
Theses analysis showed a high level of saturation in oxygen. In all
cases, the level was higher than 8mg/l, which is a limit for the most
sensitive species living in this water. Again a concentration peack was
reached during the cold weather period.

![](media/image5.png){width="3.933333333333333in"
height="3.0166666666666666in"}Graph 4. Dissolved oxygen concentration

Nitrate

The nitrate and nitrite rates varied between 2.2-3.4 mg; except a few
values, there was no phosphate in the water.

## **Conclusion**

Through the biological methods, we found the saproby rates: they were
situated between 1.7-3.5. We've effectively found a lot of species so,
according to the chart below (Table 4), the water is averagely polluted.

Acidity of the water was stable during the studied period. The pH values
were always in a weak alcaline range which is suitable for developpement
of most organisms. The alcalinity showed that the water contains
variable amont of carbonate ions due to the nature of the ground
(limestone).

The water temperature of the river remains cold enough to maintain a
high concentration of dissolved oxygen. These two factors are
interdependant, and a high level of oxygen is a guarantee for an
abundant developpement of fauna, in particular macroinvertebrates. This
particular fauna contributes directly to the absorption and
decomposition of organic materials. Thus dissolved oxygen directly
contributes to the \"self cleaning\" of water by the mean of its fauna..
A lot of different species of small water invertebrates (insects grub,
worms, shellfish) survive and can develop, it means the water is clean.
In general, in the Swiss lakes, the content of oxygen is never below 4-6
mg/l. In our rivers, this rate was situated between 9-13 mg/l because
the mixing of water was more intense because they were less than 1m
deep.

The absence of nitrates, nitrites and phosphates in the water shows that
there are no excess of detergent or farm products (fertilisers). These
two parameters are important, because abundance of these minerals leads
to eutrophysation of water, by boosting the developpement of alguaes.
Eutrophysation causes a maximal oxygen consumption and leads to asphyxy
of the water\'s fauna.

The absence of nitrate can be explained by the geological nature of the
river\'s bassin and Lausanne\'s area which is located on a rocky ground
made of sandstone. There is no groudwater that can store the nitrate
coming from agricultural activities. For the phosphate, swiss law has
forbidden the use of phophate in cleaning powder since 1986. Domestic
and industrial waste water must be cleaned, including chemical
dephosphatation, prior to its release in nature. These water protection
actions, show to be effective.

Chemicaly and according to the chart below, this oxygen's rate means
that the water is clean (Table 4).

Table 4. Saproby degree, dissolved oxygen and water quality.

+-------------+-------------+-------------+-------------+-------------+
| Quality     | # Clean     | Averagely   | Hardly      | Extremely   |
| class       |             | polluted    | polluted    | polluted    |
+-------------+-------------+-------------+-------------+-------------+
| Saproby     | 1.0-1.8     | 1.8-2.7     | 2.7-3.5     | 3.5-4       |
| index       |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| Dissolved   | \>8         | \>6         | \>2         | \<1         |
| oxygen      |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+

The biological method gave us a global information about the
environment, so allowed us to characterize a big area without having to
calculate anything. These results informed about the environment during
a long period of time. Whereas the chemical method gave us precise
values about specific factors, so that we needed mathematics to analyse
them; moreover, they gave us a localized information and only about the
instantaneous state. Besides, biology informed about combined effects of
the different factors. Chemistry could only give informations about one
factor.

Finally, the biological method was simple, cheap and required no
apparatus expect a microscope to determinate the water animals, on the
contrary the chemical method required expensive materials which could
break down. These differences between chemical and biological methods
explain how they are complementary to determinate the water quality.

# 

# **Discussion**

To have more reliable chemical results, we should use more precise
material than colour test, for the PH, nitrite and nitrate. We should
also do more samplings by week and on a longer period of time.

On the contrary, we don't think we could improve the biological results.

# 

# **Bibliography**

-   MIRAM Wolfgang & SCHARF Karl-Heinz, *Biologie: des molécules aux
    écosystèmes*, © LEP, Loisirs et Pédagogie, Lausanne 1998.

-   OLSEN L.-H & SUNESEN J. & PEDERSEN B. V.' *Les petits animaux des
    lacs et rivières*, © Delachaux et Niestlé SA, Lausanne/Paris, 2000.

-   NAGEL Peter, *Bildbestimmungsschlüssel der Saprobien*, © Gustav
    Fischer Verlag, Stuttgart/New-York, 1989.

-   GLAUSER Peter, *Environnement Suisse: Statistiques et Analyses*, ©
    OFS, Neuchâtel, 2002.

-   www.swiss-globe.ch

-   www.globe.gov