Results for lakes of the I1 action group

INHABIT project

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Results for lakes of the I1 action group

Lakes - Selection of study sites

Study lakes are 13 , including natural and heavily modified waterbodies, and are located in the two regions of Piedmont and Sardinia: 7 lakes in Piedmont and 6 in Sardinia 6. Six lakes were initially planned for each region, including the only natural lake in Sardinia: Lake Baratz . After the first sampling campaign in Sardinia, we became aware of the presence of unexploded ordnance on the bottom of the lake. Judging dangerous to work on its sediments in the vicinity of the bottom, it was decided to continue the work on the four biological parameters in another lake, Lake Piccolo di Avigliana, a Piedmont natural lake, which is located in a regional park reserve and is of particular ecological interest.
However, it was decided to keep the sampling of Lake Baratz for those parameters that are not considered hazardous (phytoplankton and macrophytes): this only natural lake in Sardinia is of particular importance for the Region.
The waterbodies chosen were therefore , in Piedmont: 5 lakes Piccolo di Avigliana , Candia, Sirio and Viverone and two heavily modified water bodies : Morasco , in the basin of the Toce and Serrù in the Gran Paradiso National Park, both hydropower reservoirs.
In Sardinia 5 reservoirs were investigated: Bidighinzu, Sos Canales, Liscia and Torrei; mainly used for drinking, and Posada also used for agriculture.

Lakes - selection of study sites - Piedmont       Lakes - selection of study sites - Sardinia

Detailed descriptions of studied lake and reservoirs are reported in deliverable I1d1.

Lakes - field campaigns in Piedmont and Sardinia

Field campaigns were carried out for the application of the Lake Habitat Survey and sampling of the four biological quality elements required by the WFD 2000/60 , according to the criteria and procedures set out in the national protocols for sampling. These campaigns have been carried out by CNR ISE, supported by ARPA Piemonte in natural lakes and by ENEL and IREN in reservoirs in Piedmont. In Sardinia sampling was supported by ENAS in reservoirs and the University of Sassari for lake Baratz.
In the reservoirs, macrophytes were generally absent, because of the large level variability, that also caused the impossibility to sample macrobenthos in the littoral zone, because the nature of substrate does not allow the application the sampling methods standardized for lakes.

Lakes - Data collection in the field

We studied the four biological elements required for the evaluation of the quality of lakes and reservoirs: macroinvertebrates , phytoplankton, macrophytes and fish fauna, and we applied Lake Habitat Survey (LHS).
Each biological element was investigated in a specific sampling periods:

  • macrobenthos in spring and in autumn;
  • macrophytes in the period of maximum vegetative growth of the plants;
  • phytoplankton collected periodically during the whole year;
  • fish fauna sampled once, between spring and fall.

Macrophytes and macrobenthos were sampled along transects (lines  perpendicular to the shore), phytoplankton at the deepest point of the lake at different depths, and fish were collected with nets and by electrofishing.
In addition to the biological parameters, we also investigated the hydromorphological characteristics of each lake, using the Lake Habitat Survey (LHS), developed for the English lakes and standardized at European level. In the INHABIT project , the LHS method has been validated in the Italian lakes. Sampling methods are described in detail in deliverable I1d1.

Lakes - Databases

A relational database was built for high-resolution data from lakes within the project INHABIT . To avoid the use of proprietary software , the database was written using the software PostgreSQL , a relational database available with Open Source license .
A final database was prepared on the basis of a biological and a hydromorphological databases (deliverables I1d2 and I1d3 ) to store together all the data relating to the description of the lacustrine habitat collected according to the Lake Habitat Survey, and the high-resolution data collected in the field. At the end of the project , the database has hydromorphological data for 13 lakes or reservoirs, for a total of 170 observations and 170 specific habitat descriptions of the shore between a detection point and the following. The database also contains the results of the chemical analyzes of 258 water samples from 13 lakes of the project.
For the biological quality elements , data were stored at the species level for phytoplankton (58 samples and 281 taxa), macrophytes (94 samples and 20 taxa) and benthos (28 samples and 177 taxa). In the case of fish fauna, stored data contain information about each specimen (607 fish of 29 species in 16 samples).
The database is described in deliverable D1d2.

Lakes - Validation of sampling methods for lakes and reservoirs

Natural variability of the biota, particularly for elements showing seasonal cycles, may lead to significant changes in the species composition and biomass . This means that the choice of the sampling frequency and distribution of samples during the year may represent a critical factor for assessing the ecological quality from the biological communities.
Of the four biological elements used to classify the lakes, three (phytoplankton, macrophytes and macroinvertebrates) show a marked seasonality and some spatial variability.
For phytoplankton, we analyzed three metrics defined by national law (composition indices, chlorophyll concentration and total bio-volume), comparing the anthropogenic (expressed by the gradient of total phosphorus ) and natural  variability (seasonality) and estimating the uncertainty in the classification with different sampling frequencies.
In the case of macrophytes, methods of monitoring and classification were analyzed considering the accuracy of the assessment and the sampling effort provided by the monitoring protocols, to verify if it is adequate to the needs of the classification.
Our analysis showed that the variability of phytoplankton metric reflects the trophic gradient and is significantly larger than that accounted for by seasonal variations, indicating the robustness of the indicators used and the stability of phytoplankton assemblages.
Conversely, the general formulation of the index based on macrophytes may need to be refined in order to better understand the differences in ecological quality between lakes. Furthermore, in the case of the macrophytes, a significant reduction of the effort of sampling does not seem possible without compromising the quality of the classification, while, for phytoplankton, it would be acceptable to reduce the number of annual samples from 6 to 4 without compromising the result of the classification.
The details of this activity are reported in deliverable I1d5.