Lade Inhalt...

The Vertical Distribution of the Quagga Mussel in Harbours. From Ecological Research to Bilingual Teaching at Secondary Level

Magisterarbeit 2008 55 Seiten

Didaktik - Biologie

Leseprobe

Contents

1. Abstract

2. Introduction
2.1 Ecological and economical damages
2.2 Aim of this study

3. Materials and Methods
3.1 Industriehafen Mannheim
3.2 Method of sampling
3.3 Measurement and identification
3.4 Morphological differences between Zebra and Quagga mussels

4. Results
4.1 Relative abundance of Dreissena polymorpha and Dreissena bugensis
4.2 Population density of Dreissena polymorpha and Dreissena bugensis
4.3 Vertical distribution of Dreissena polymorpha and Dreissena bugensis

5. Discussion
5.1 Methods
5.2 Results
5.2.1 Vertical distribution
5.2.2 Age structure
5.3 Conclusion

6. Didaktische Begründung.
6.1 A bilingual project?
6.2 Ideen zur Gestaltung - a bilingual project
6.3 Medienkompetenz.
6.4 Biologie und Sprache

7. Acknowledgement

8. References
8.1 Books, articles and further reading
8.2 Web links
8.3 Figures
8.4 Appendix

1. Abstract

In June 2008 samples were taken from four different sites in the Industriehafen Mannheim (Germany), to describe the abundance and vertical distribution of the non-indigenous species Dreissena bugensis (ANDRUSOV 1897) and D. polymorpha (PALLAS 1771). The species were compared in their relation in abundance, size and vertical distribution. The Quagga mussel is the dominating species, covering an average of 65% to 100% of the sampled substrate in water depths of 2.5m to 5m, whereas the density of the Zebra mussel has declined to a minimum of 0% to 20%. The maximum population density could be found between 3 - 4.5 m, where individuals of the Quagga mussel with sizes below <10mm were dominant, whereas individuals below <15mm dominated the Zebra mussel population. In deeper water regions (4m to 5m), where anoxic mud was the dominating substrate, Dreissena polymorpha showed a minimal density with <5%, whereas Dreissena bugensis colonized an average of 65% to 85% of the scarce solid materials that could be found. The vertical distribution of D. rostriformis bugensis shows an interesting pattern that could help to determine the initial period of its settlement.

2. Introduction

The Quagga mussel (Dreissena bugensis rostriformis) is a non-indigenous species that has been recorded in Germany for the first time in the Main river, east of Würzburg in 2007 (VAN DER VELDE & PLATVOET 2007). In October 2007 the Quagga mussel has been recorded at several harbors of the upper Rhine as in the Rheinhafen Karlsruhe, the Ölhafen and the Industriehafen Mannheim (MARTENS et al. 2007), latter being the locality were samples were taken for this study. D. rostriformis bugensis is closely related to the Zebra mussel (Dreissena polymorpha), which has been recorded in the upper Rhine close to Mannheim around 1840 (REY et al. 2004).

Both species are so called “invasive species” defining them as animals, which “have entered an environment after 1492 (beginning of modern times), that has not been accessible before, to establish new potential populations. This progress happens intended or unintended with direct or indirect involvement of human being” (own translation from German; KINZELBACH 1996)

Invasive species are found in many various fauna groups and they often differ in their invasive strategy. D. polymorpha and D. bugensis are both examples of r - strategy; animal groups with a high reproductive potential, which are usually undemanding generalists (REY et al. 2004).

The origin of the Zebra and the Quagga mussel is the northwestern part of the Black Sea and some estuaries (ORLOVA et al. 2004, VAN DER VELDE & PLATVOET 2007). The natural dispersal of Dreissenidae happens mainly by larval drift enhanced by currents, or water birds which spread larvae attached to them. But human influence allows these species to cope with larger distances and to cross their natural barriers. Veliger larvae of Dreissenidae can settle on boats or they are being transported within the ballast water of ships, allowing them to move upstream. So shipping has been identified as the primary dispersal mechanism for both invasive freshwater Dreissenids (JOHNSON et al. 2001; ORLOVA et al. 2005). There are two main canals connecting the Pontocaspian region with the region of Western Europe. The navigable waterways of the interconnected rivers Dniepr, Prypet, Bug, Vistula, Oder, Rhine and German canals (Midland canal etc.) constitute a northern invasion route, and the Danube a southern route to western Europe (MÜLLER et al. 2002).

The harbors where the Quagga mussel is recorded usually have a high volume of cargo and the species has not been found in the open waterways of the Rhine so far. D. bugensis prefers standing water bodies and adults attached to ships most probably spawn during the lay days in harbors and not whilst movement of the ship (MARTENS et al. 2007).

2.1 Ecological and economical damages

D. bugensis is not long known in Western and Central Europe, whereas in Northern America this species has been recorded in 1988 (MACKIE & SCHLOESSER 1996) and is widely observed as it has caused financial damage of several milliards of Dollar (e.g. MILLS et al. 1996; WARD & RICCIARDI 2007). It is also invasive in Eastern Europe (e.g. ORLOVA et al. 2004). D. bugensis often co-occurs with D. polymorpha but after a period of settlement it dominates and displaces D. polymorpha and other Bivalvia (MILLS et al. 1996; ORLOVA et al. 2004).

D. polymorpha and D. bugensis both have byssal threads and spread with veliger larvae and as fast growing filter feeders that are attached solidly to their substrate and have a hard shell and high biomass they change their environment immensely (WARD & RICCIARDI 2007). Due to their byssal threads often clumping emerges and the mussels can build up several layers (figure 1).

illustration not visible in this excerpt

Figure 1: Dreissena polymorpha and Dreissena bugensis covering a lifted rip rap stone with several layers through clumping (original).

Being filter-feeders with a high biomass with population densities of up to a maximum of 900.000 individuals / m² (CAMPBELL & REECE 2003) they have an influence on the food web close to the ground (MACISAAC 1996) and also indigenous species are in danger of extinction (BURLAKOVA et al. 2000) or their population is heavily constricted (RICCIARDI 2004) as for example other Bivalvia species . D. polymorpha colonizes their shell and prevents them to reopen (figure 2) (MACISAAC 1994; RICCIARDI et al. 1997).

illustration not visible in this excerpt

Figure 2: Unionid mollusk, Potamilus alatus, infested with zebra mussels collected near the head of the Detroit River (SCHLOESSER et al. 1998)

Both species directly influence water transparency. The visibility range in the Erie lake in North America has doubled by direct influence of Dreissena, allowing algae to grow in deeper water regions and when dying or being eradicated and washed ashore causing displeasing conditions ashore (MACISAAC 1996) Some species also benefit from their new “guest” as waterfowl and some fish, providing them with a nutritional source of food during winter months (MACKIE et al. 1996). At the Bodensee in south Germany, Dreissena populations are annually decimated to a depth of about 8 meters (which is the diving depth of diving ducks) below that multilayered Dreissena beds can be observed with perennial age structure. (REY et al. 2004)

D. polymorpha rapidly became a plague after its introduction in North America. Due to clogged water pipes and industrial machinery the Zebra mussel has already cost many thousands of dollars in damage. Also in drinking water treatment and power stations, financial damages of several milliards of dollars ensued. Through biofouling, filters and pipes are clogged. The investment made for the prevention of such damages caused by D. polymorpha, make the biggest part (CONELLY et al. 2007). After the first recording of the Quagga mussel in Germany in 2007 it was of high interest to prevent its dispersal into the Bodensee, as it is an important water reservoir. The Zebra mussel has been no threat for the water pipes in the Bodensee so far as it doesn`t settle in the depths where water is taken from, but the Quagga mussel has been found in depths exceeding 150 m and is reported to grow and also to reproduce in softer sediments where the temperature never exceeds 12°C (MACKIE et al. 1996).

The Quagga mussel and the Zebra mussel have a similar ecology and live in similar habitats, but D. bugensis is the dominating species, displacing D. polymorpha after a relatively short period of settlement. Here is a conclusion of advantageous adaptations of the Quagga mussel;

- D. bugensis can colonize deeper water than D. polymorpha (up to 130m in the Great lakes) (MILLS et al.1996; MILLS et al 1993)
- D. bugensis tolerates other temperature levels and spawns at lower temperatures (MACKIE et al. 1996; MILLS et al. 1993)
- Quagga mussels are more efficient filter-feeders (higher filtration rate) and are better adapted to acquiring food resources when food is scarce or when food quality is low (RICCIARDI & WHORISKEY 2004)
- Quagga mussels have lower respiration rates and larger body size compared to Zebra mussels, which devote a greater proportion of body tissue to reproduction (they release more eggs) (RICCIARDI & WHORISKEY 2004)
- Quagga mussels settle at larger size than Zebra mussels making them more successful as later invaders (RICCIARDI & WHORISKEY 2004)
- Quagga mussels can survive, grow, and feed better that Zebra mussels with lower temperatures ( ORLOVA et al. 2005; MILLS et al. 2002)

2.2 Aim of this study

This study is supposed to be a review of the general condition of Dreissenae populations in the Upper Rhine (Mannheim) and its aim is to observe the vertical distribution of Zebra and Quagga mussel adults in relation to their abundance, as this could help to determine the initial phase of settlement of the Quagga mussel and to understand the displacement of the Zebra mussel more detailed. Studies from North America show that the Quagga mussel usually colonizes deeper regions first and displaces the Zebra mussel due to its advantageous adaptations after several years (RICCIARDI & WHORISKEY 2004). This should be shown by a pattern of vertical distribution, as the density of taller individuals should reach its maximum in deeper water regions. However a seasonal shift of age in the main belts of occurrence has been recorded in North America, which is caused by the ability of the species to migrate (MACKIE et al. 1996; KLOIDT 2008).

3. Material & Methods

3.1 Industriehafen Mannheim

The samples were taken at four sampling spots in the Industriehafen, Mannheim (008°18´E49°31´N) (figure 3)

illustration not visible in this excerpt

Figure 3: Samples were taken in the basin of the Industriehafen Mannheim

(008°28´E49°31´N) (scale 1:25.000 Landesvermessungsamt Baden Württemberg 2003)

This area was optimal as both Dreissena species have been recorded there in 2007 (MARTENS et al. 2007) The Industriehafen Mannheim is part of a huge and important inland port area covering about 2.68 square kilometers of water and about 8.63 square kilometers of dockland. About 500 enterprises with about 20.000 jobs are established on the dockland. Since 1996 the port has an average volume of cargo of about 8 million tons per year and ships from the Netherlands and Belgium make the biggest part of international imports (HÖRNER 2008 (html)). The Industriehafen is situated in an old river channel of the river Rhine, latter being straightened between 1817 and 1876 (BERNHARDT 2000 (html)). The construction of the Industriehafen was finished in 1907, being one of the older parts of the inland port of Mannheim. Through a lock it is connected to the Neckar which is connected with the Rhine after 50 meters.

First recordings of the Quagga mussel in Western Europe were made in Holland, Willemstad in the Holland’s Diep in April 2006 (MOLLOY et al. 2007). Of course this could give a hint about the origin of the young local Quagga mussel population, but of course it is not possible to determine exactly from where the species has been introduced. As there are no individuals found in the open waterway, the initial phase of settlement most probably started inside the harbor. The patterns of size and density of D. bugensis found in this study underline that.

An alternative or additional sampling sight would have been the Rheinhafen, Karlsruhe, as both species also occur there and could be in an earlier phase of settlement compared to Mannheim (MARTENS et al. 2007), but due to longer absence of the research ship “Max Honsell”, the required equipment was not available to collect an adequate number and variety of samples.

3.2 Method of sampling

The vertical distribution of D.polymorpha and D.bugensis should be observed to a depth of 6 m. This could not be done manually so the LUBW (Regional Office of Baden Württemberg concerning environment, measurement and environmental conservation) was contacted and kindly agreed to be available with its research vessel “Max Honsell” to take samples for this study.

Samples were taken on June 3, 2008. Jens Storck, a staff member of the LUBW, already had experience about the distribution of the Dreissena species in the harbor basins of Mannheim and could help me to choose sample spots where both D. polymorpha and D. bugensis have been found before.

We profiled the depth of each sampling point with the sonar of the vessel, attached to the front and the back of the ship. Therefore the vessel stopped in vertical direction to the shore and we could define the shallowest and deepest measuring point. As there is no drift in the basins we could use an iron pendulum attached to a rope, which was divided into 50cm sections to define the depth profile (compare figures 10 & 11).

With a hydraulic shovel, stones and other substrate was taken from the ground and put on the ship for collecting species (figure 4). At each sampling point 6 samples were taken, ranging from a depth of 50cm to 5.50m. The water level was 5.76m (water level Maxau, June 3, 2008).

illustration not visible in this excerpt

Figure 4: substrate was lifted with a hydraulic shovel (original).

The sampled stones and other substrate were investigated on the relative density of Quagga and Zebra population. After that, samples of 0 - 500 individuals were carefully scraped off with a knife from different parts of the substrate. The samples were categorized and put in preserving glasses with river water. For further measurement and identification they were put in 70% ethanol the next day.

3.3 Measurement and identification

As next step the length of between 100 and 200 individuals per sample was measured with a sliding ledge and divided in several size ranges to define the abundance and relation of

D. bugensis and D. polymorpha (figure 5).

illustration not visible in this excerpt

Figure 5: Mussels were measured with a sliding ledge (original)

5 size ranges were chosen; 0-5mm, 0-10mm, 0-15mm, 0-20mm, 0-25mm and the abundance of the Zebra and the Quagga mussel was defined. Other species were noticed but not taken into further consideration.

The identification of both species caused no problems, however, to identify small individuals (<10mm) a magnifying glass was used (x10). For identification, criteria summarized in PATHY & MACKIE 1992, and MACKIE & SCHLOESSER 1996, were consulted.

3.4 Morphological differences between Zebra and Quagga mussels

The Zebra and the Quagga mussel belong to the family of Dreissenidae mussels and have their origin in the Black Sea, Pontocaspian region. The wide variability in coloration and the stripe pattern of both, the Zebra and the Quagga mussel can lead to uncertain identification of the species as long as one is not familiar with the distinguishing shape of the shell. The coloration pattern of both species has a high variability reaching from all black to all cream and brown. Both species also show a pattern of stripes in different kind of variability including smooth stripes, jagged stripes, reminding one of the zebra stripes and single, longitudinal stripes (figure 6 & 7). Quagga mussels show some different stripe patterns and variability of coloration, the characteristic “zebra stripes” are missing (MARTENS et al. 2007). There is one distinguishing pattern consisting of lateral black and white stripes, interrupted by a longitudinal white line ( MAY & MARDSEN 1992).

illustration not visible in this excerpt

Figure 6: variations of D.polymorpha and D.bugensis, one can see the characteristical ridges of the Zebra mussel (original).

[...]

Details

Seiten
55
Jahr
2008
ISBN (eBook)
9783656845775
ISBN (Buch)
9783656845782
Dateigröße
5.9 MB
Sprache
Englisch
Katalognummer
v284096
Institution / Hochschule
Pädagogische Hochschule Karlsruhe – Biologie
Note
2,0
Schlagworte
Invasive species dreissena polymorpha dreissena bugensis Dreikantmuschel Zebramuschel Quaggamuschel Invasive species rhine Invasive Arten Eingeschleppte Arten Rhein Muscheln Rhein Neozoen Neozoen Rhein Neozoen Karlsruhe Mollusken Rhein

Autor

Teilen

Zurück

Titel: The Vertical Distribution of the Quagga Mussel in Harbours. From Ecological Research to Bilingual  Teaching at Secondary Level