Submerged vegetation

General

Section
Column width 80% General characteristics   Common name Submerged aquatic plants Region The Netherlands, Europe Water system Lakes, rivers Nature parameter Macrophytes Factsheet made by K.E. van de Wolfshaar Column width 20%

Description Habitat

Occurrence

Up to now, only fresh water plants are registered under submerged aquatic plants. Within the Water Framework Directive, the area of submerged aquatic plants is one of the measures for the biological quality element "macrophytes and fytobenthos".

Environmental boundary conditions

The light climate is the main determining factor for macrophyte growth in Dutch fresh water lake systems. As a number of different characteristics, such as algae growth, suspended particles, detritus, humic acid and background extinction, determine the light climate, different depths can be found for the various lake types. Grazing by herbivorous birds can sometimes be impediment to growth in shallow water.
The species composition is influenced by sediment type and salinity, and to a lesser extent by the total area of submerged aquatic plants. Fetch is not considered a limiting factor for submerged aquatic plants. Schutten (2005), on the other hand, states that besides light climate biomechanical disruption is an important factor for macrophytes. Especially in late summer and spring, when the macrophyte growth spurt has stopped, they are vulnerable to feed and surge.

Control and growth opportunities

Submerged aquatic plants are sensitive to changes in salinity. A salinity of 0,6gCl/L reduces the suitability. With a salinity of 1gCl/L, the suitability is zero (Figure 4.2.1, left panel). Aquatic plants need a minimum percentage of light to reach the bottom. Dredging outside the growth season can help to control the plants.

Dose-effect relations

The dose-effect relations are derived from an extended study commission by RIZA. The literature list used in this study can be found in report #2.

Section

Column width 50% Chart dataDisplay true legend false xlabel %SI type xyline title Percentage of light reaching bottom dataOrientation vertical yLabel HSI %SI HSI 0 0 1 0.4 4 0.8 7 1 100 1 Reference: #1, #2 Column width 50% Chart xlabelOrientation vertical dataDisplay true legend false xlabel Salinity (g Cl/L) type xyline title Salinity dataOrientation vertical yLabel HSI Salinity (g Cl/L) HSI 0 1 0.6 1 1 0 5 0 Reference: #2

In addition to the above-mentioned relations, dose effect relations are also available from the Macromij model. This model also contains floating aquatic plants. The percentage of light that reaches the bottom can be calculated through %Surface Irradiance=exp(-k*H) k = light extinction, H= depth.

Uncertainty and validation

The dose-effect relations have been validated for the IJsselmeer district and the Friese boezemmeer De Leijen #2.

Applicability

The dose-effect relations can be applied to all Dutch fresh waters.

Exemplary project

Volkerak-Zoommeer Habitat analysis #1 and the IJsselmeer district and Friese boezemmeer De Leijen reference #2.

References

1

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Haasnoot, M. en Van de Wolfshaar, K.E.. Habitat analyse in het kader van de Planstudie/MER voor Krammer, Volkerak en Zoommeer. WL report Q4015. 2006 (Download rapport van pagina met toepassingen)
2

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Penning, W.E., Haasnoot, M., Kuijper, M. en Van Buren, R. Rekenregels voor macrofyten in meren ten
behoeve van de KRW. WL | Delft Hydraulics rapport Q4058, Delft. 2006 (Download rapport van pagina met toepassingen)