13.07.2015 Views

Report on Harmonisation of freshwater biological methods

Report on Harmonisation of freshwater biological methods

Report on Harmonisation of freshwater biological methods

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

64. In general, this technique is the most comm<strong>on</strong> sampling procedure and applied in30 <strong>methods</strong> using a hand-net. The nets used differ in size <strong>of</strong> the opening and mesh.Net-openings specified by the assessment <strong>methods</strong> vary between approximately 600and 900 square centimetres. In half <strong>of</strong> the schemes, animals are retained by meshsizes<strong>of</strong> about 500 µm.65. The procedure <strong>of</strong> quantitative sampling is standardised by the guidance ISO 8265(1988) or EN 28265 (1994) Methods <strong>of</strong> <strong>biological</strong> sampling: Guidance <strong>on</strong> the designand use <strong>of</strong> quantitative samplers for benthic macro-invertebrates <strong>on</strong> st<strong>on</strong>y substratain shallow <strong>freshwater</strong>s. Surber samplers are most comm<strong>on</strong>ly used for quantitative,area-related sampling. The recommendati<strong>on</strong>s <strong>of</strong> this standard for maximum aperturesize <strong>of</strong> the net range between 250 to 750 µm. The models currently applied in variousnati<strong>on</strong>al watercourse m<strong>on</strong>itoring programmes differ in sampled area (0.01 to 0.12 m²)and mesh-size (100 to 500 µm).66. In deeper streams benthic macroinvertebrates are taken using <strong>of</strong> grabs, dredgesand artificial substrates. The applicati<strong>on</strong> <strong>of</strong> these devices is standardised in ISO 9391(1993) or EN ISO 9391 (1995). These are the same standards as the previous <strong>on</strong>es.The difference in dates is caused by the different dates <strong>of</strong> publicati<strong>on</strong> by the twoorganisati<strong>on</strong>s.67. ISO and CEN standards for sampling invertebrates are currently under revisi<strong>on</strong> tomake them more WFD compliant, but the timescale for publicati<strong>on</strong> will be severalyears.68. Sampling varies from seas<strong>on</strong>al collecti<strong>on</strong>s to procedures c<strong>on</strong>ducted every fiveyears. Annual sampling is the most comm<strong>on</strong> interval applied in river m<strong>on</strong>itoring. Insome m<strong>on</strong>itoring programs observing the sapro<strong>biological</strong> water quality sampling isseas<strong>on</strong>al. This inevitably influences the degree <strong>of</strong> uncertainty <strong>of</strong> the resultingecological classificati<strong>on</strong>s, i.e. the likelihood <strong>of</strong> the banding allocated69. Nearly 60 percent <strong>of</strong> the <strong>methods</strong> applied determine at least selected orders <strong>of</strong>benthic invertebrates to species- or species groups-level. The remainingapproximately 40 percent <strong>of</strong> <strong>methods</strong>, identify organisms to genus or family. It mustbe noted that in several assessment <strong>methods</strong> taxa are identified to lower levels thanrequired to adequately compute the respective quality index.17

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!