Survey Planning; Alternative Methods To Consider - Planet WGSW-24010 User Manual

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SURVEY PLANNING

This chapter describes the steps which should be taken when planning MTR surveys and should
be read before the surveys are undertaken. The first step is to check that the MTR method is
appropriate for the use required (see 2.3 and 2.4). The next steps are to consider alternative
methods, devise a suitable sampling strategy, plan the logistics of the surveys (when and where
to survey and what resources are required) and collect ancillary data. These steps are described
below.
3.1 Alter native methods to consider
When planning biological surveys to assess river trophic status, it is important to choose the most
appropriate methodology. Method selection requires recognition of the various options available
and an understanding of their comparative strengths and deficiencies under a range of
circumstances. This section outlines the available options and lists criteria to consider when
choosing which option(s) to adopt.
3.1.1 Options
There are two biological methods recommended for the assessment of the trophic status of rivers:
the macrophyte-based Mean Trophic Rank and the diatom-based Diatom Quality Index (a
transformation of the Trophic Diatom Index). An introduction to the MTR is given in Section
2.1 and an outline of the DQI/TDI is given below. Although experienced biologists may also
glean information on trophic status from other riverine biota, for example the benthic macro-
invertebrate community, there is no validated standard method to do this. Use of such
information should thus be used with caution and only to support evidence gained from one or
both of the recommended methods below.
3.1.2 Tr ophic Diatom Index (TDI) & Diatom Quality Index (DQI)
The Trophic Diatom Index (TDI) was developed by Kelly and Whitton (1995a & b) for the NRA
as part of an investigation into the use of plants to monitor rivers and in response to the needs of
the UWWTD. It was further refined by Kelly (1996a, b & c), following testing by practitioners
in Agency regions.
The method is designed for monitoring the trophic status of rivers and streams, and uses benthic
diatom communities rather than the macrophyte assemblages used in the MTR system. Diatoms
are widely used for monitoring water quality on the continent (Whitton & Kelly 1995), for
palaeoecological studies of lake acidification in the UK (Battarbee 1984) and, more recently, lake
eutrophication. In one instance (Anderson & Rippey 1994), a change from eutrophic to
mesotrophic conditions following diversion of a nutrient input from a lake in N. Ireland was
observed in a single season. As diatoms derive their nutrients directly from the water column and
have generation times measured in days rather than months or years, it was thought that these
might constitute a reliable tool for assessment of eutrophication in rivers.
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