**4.7 Benthic invertebrates**

84 Studies on Environmental and Applied Geomorphology

The number of measuring points for water velocity on every vertical is dependent on the

Monitoring of the ground water level (GWL) of the ground water facilities (boreholes, wells) was executed occasionally (once per month) in the 12 month period (from March 2010 to February 2011). The measuring was performed using an electrical water level meter (type GTS, made in Italy) equipped with lightening and sonorous signal. In the case of the presence of artesian ground water level (which is expected in Pl3 sediments – GW6), the

Monitoring of macrophytes in Lake Prespa was performed in the period from April to May 2010 and from August to September 2010 on five locations along the Macedonian coastline:

The macrophytes field survey methods which have been used in the biological monitoring of Lake Prespa were consistent with the Water Framework Directive: a) **characteristic zonation -** determination if all type-specific vegetation zones for this Lake; b) **preparing the lists of species present in a lake (floristic inventories) -** determination of collected plant species using different floras and keys; c) **determination of vegetation density -** which focuses on the overall abundance of macrophytes. Abundance were estimated on a fivepoint scale (Braun-Blanquet 1964) where 1 = very rare, 2 = infrequent, 3 = common, 4 = frequent and 5 = abundant. The vegetation density is the result of different pressures, such as alteration of the shoreline, artificial water level fluctuations, artificial wave action and the trophic state; d) **mapping of lake's vegetation** (phyto-littoral mapping) - according to this method, the qualitative composition and distribution of aquatic vegetation was investigated.

Fish for analyses were collected with various fishing gear in day and night time experimental fishing. A cast net was also used for day time fishing with mesh size of 13 mm, whereas the night time fishing was performed with bleak nets (mesh size from 12 mm and 13 mm), and barbell nets with mesh size of 22 mm, 24 mm, 26 mm and 28 mm. The height of each fishing gear was basically a hundred heights per each mesh and the length was about 50 metres. All nets were set between 3 and 6 pm, fished overnight and lifted between 8 and

10 am in order to ensure that the activity peaks of each fish species was included.

• For profile of 10 m 3 to 5 verticals • For profile of 10 to 50 m 5 to 7 verticals • For profile of 50 to 100 m 7 to 9 verticals • For profile of more than 100 m 9 to 15 verticals

• On verticals up to h≤30 cm depth one point on 0.5 h

and bottom

• On verticals from h≤30 to >30 <100 cm three points: 0.2; 0.6 and 0,8h • On verticals from h≤30 and the bottom in four points: 0.2; 0.6; 0.8 h

monitoring was executed by measuring the natural capacity [l/sec] of the well.

Stenje, Golema River, Krajnska River, Brajcinska River and Dolno Dupeni.

depth of that vertical, such as:

**4.4 Hydrogeology** 

**4.5 Macrophytes** 

**4.6 Fish** 

Benthic invertebrates from the Prespa Lake and its main tributaries were collected according to the requirements of the EU Water Framework Directive (WFD) 2000/60/EC.

From the Prespa Lake itself, the collection of bottom fauna samples was performed by several different devices: Ekman grab, sediment corer, triangle bottom dredge and hand net. Macroinvertebrate standard methods applicable to lakes were used (ISO 9391:1995 and ISO 7828:1985). Concerning to the main tributaries of Prespa Lake, benthic invertebrate samples were collected with a Surber sampler or hand-net following standard methodology for collection of bottom fauna (ISO 8265:1988 and ISO 7828:1985). For preservation of biological samples 70% ethyl-alcohol or 4% formaldehyde were used, samples properly labelled and additionally processed in the laboratory.

In the laboratory, the animals were flushed with tap water through a standard sieve (280 μm pore size). Material was divided by groups, for further determination, mainly to the lowest taxonomic level (genus/species). Generally, determination to the species level is recommended because the species level logically provides the most detailed and sound information about autecological demands of a certain animal species. Determination was performed using identification manuals. Based on WFD principles, data informing on the communities' taxonomic composition, abundance, diversity and sensitive taxa were taken into consideration, both for Prespa Lake and its tributaries. Biotic indices that are suitable for Prespa Lake and its watershed monitoring purposes were used.
