Specific Issues In Sampling And Monitoring

Temporal and spatial scales of zooplankton sampling and monitoring in fresh water depend on the type and extent of ecological concern, issues and hypotheses that are going to be put forward and tested. The general

Table 7.6. Key to phyla of protozoans (modified from Jahn et al. 1979) (Figure 7.8).

1a Body with cilia or tentacles Phylum Ciliophora (often called ciliates)

Epistylis (Figure 7.8c), Frontonia, Paramecium, Paradileptus (Figure 7.8e), Vorticella and others

1b Body without cilia or tentacles ->■ 2

2a Body with other structures for locomotion -► 3

2b Body without obvious structures for locomotion ->■ 4

3a Body with one or more flagella Phylum Mastigophora (often called flagellates)

Ceratium, Euglena, Peridinium and others

3b Body with pseudopodia Phylum Sarcodina (often called amoebae)

Arcella (Figure 7.8a), Cyphoderia (Figure 7.8b), Euglypha (Figure 7.8d), Difflugia, amoebae without a rigid test (Figure 7.8f) and others

4 Movement by body flexions; Phylum Sporozoa all parasitic

Plasmodium (the causative organism of malaria) and others

Figure 7.8 Protozoans. a) Arcella mitrata - Body with test. Test circular from above, dome-like on top. Small central opening. Scale bar 50 pm; b) Cyphoderia sp. - Body with test. Test oval, short cylindrical neck. Round opening (O) oblique to body of test. Test with a yellow-brown matrix. Scale bar 30 pm; c) Epistylis sp. - Bell-shaped body (B), with a stalk (S). Stalk splits into two branches and cannot contract. Scale bar 100 pm; d) Euglypha sp. - Body with oval test, made of scales of equal sizes. Opening (O) terminal. Some with spines (S) on test. Scale bar 20 pm; e) Paradileptus sp. - Body with cilia. Relatively large protozoans. Scale bar 50 pm; f) Amoeba (unidentified) - Body with no test and no cilia. Note pseudopodia (P). Scale bar 100 pm.

Figure 7.8 Protozoans. a) Arcella mitrata - Body with test. Test circular from above, dome-like on top. Small central opening. Scale bar 50 pm; b) Cyphoderia sp. - Body with test. Test oval, short cylindrical neck. Round opening (O) oblique to body of test. Test with a yellow-brown matrix. Scale bar 30 pm; c) Epistylis sp. - Bell-shaped body (B), with a stalk (S). Stalk splits into two branches and cannot contract. Scale bar 100 pm; d) Euglypha sp. - Body with oval test, made of scales of equal sizes. Opening (O) terminal. Some with spines (S) on test. Scale bar 20 pm; e) Paradileptus sp. - Body with cilia. Relatively large protozoans. Scale bar 50 pm; f) Amoeba (unidentified) - Body with no test and no cilia. Note pseudopodia (P). Scale bar 100 pm.

framework of ecological sampling and monitoring and statistical considerations are applicable to zooplankton sampling and monitoring (such as the original BACI design or its modifications and trend analyses). A pilot sampling and monitoring program is always helpful in determining the methods of sampling (for example, plankton net versus plankton trap) and in providing basic data on species composition, density, biomass and their variability.

There is a large diversity of types of gear currently available for the collection of larval fish in freshwater habitats. The most commonly used types of gear are designed to filter volumes of water through fine mesh, including drift nets, trawl nets, seines and pumps with fitted mesh nets (Kelso and Rutherford 1996). Electrofishing gear modified for sampling small-bodied fish has also recently been used increasingly in freshwater habitats (Copp 1989; King and Crook 2002). There are also a range of more passive collection gears, such as light traps, baited traps and activity traps - where fish are either attracted into the trap or are captured while moving through the habitat. However, knowledge of the target fish reproductive life history and larval behaviour and ecology is required in the choice of collection methods, gear types, sampling periodicity and sampling habitat.

For other types of zooplankton, a conical plankton net is often useful in collecting pelagic species (Table 7.7). Depending on the mesh size and specifications of the plankton net used, the net may clog partially or fully after towing certain distances and its filtering efficiency may drop dramatically. The clogging of a net is primarily due to collection of phytoplankton and detrital particles that are larger than the mesh size. This problem is often encountered in eutrophic waters as well as highly turbid waters. The volume of water filtered by the net needs to be calibrated with a flow meter if zooplankton are need to be collected quantitatively (see Chapter 4).

Zooplankton are seldom distributed uniformly within a water body. Some species exhibit a diurnal vertical migration - often concentrating in deep waters during the day and in surface waters during the night (see Chapter 2). Zooplankton samples should be collected in a depth-integrated manner from the bottom to the surface or from multiple discrete depths.

It is difficult to properly tow a plankton net in the littoral zone - often resulting in the collection of large amounts of aquatic-plant debris that clog the net. Specialised sampling devices and techniques are recommended to use in collecting littoral zooplankton (Campbell et al. 1982; Sakuma et al. 2002).

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