A Methods Manual for the Collection, Preparation and Analysis of ...

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SECTION 2: FIELD PROCEDURESTo facilitate the reading of this document references have been kept to a minimum. Howeverit should be mentioned that the methods described below have been based on several keydocuments including: Kelly et al. (1998), CEN (2003), DARES (2004) and Taylor et al.(2005).Health and safety of field operators (practical advice)Diatom sampling should be both enjoyable and informative, however, there areattendant risks involved with these activities. The following points should be noted:1. Always wear thigh waders or some other form of protection for your feet.2. Always wear a life jacket while sampling.3. Never sample in parts of the river which are out of your depth.4. When sampling rivers which may be heavily polluted or polluted with faecal matter,be sure to always wear gloves.5. When sampling in regions such as KwaZulu Natal, Limpopo and Mpumalanga careshould be taken to avoid crocodiles and hippopotami. Great care should beexercised when sampling. These animals pose a very real threat to people and areattracted to activities at the sides of rivers and lakes.6. In some rivers leeches may also be abundant.1. Habitats for diatom-based water quality monitoringThe four distinct diatom assemblages that occur closely associated with particularmicrohabitats are generally recognised as the:Epipelon that frequents the surface of the sedimentsEpipsammon that occurs on and between the sand particlesEpilithon that inhabit gravel, stone and bedrockEpiphyton that is attached to macrophytic plantsDiatom community structure is governed to some extent by substrata associations but thereare other important influences on community composition, namely:Chemical constituents in the waterWater turbulence and disturbance (mainly from floods)Resource supply (mainly from inorganic nutrients)Grazing by micro-organismsLight regime within microhabitats11
1.1 Preferred substratumCobbles and small boulders (rocks) are the preferred substratum for monitoring diatoms inthe riverine environment, and almost all diatom indices throughout the world can be appliedto the community (i.e. the epilithon) that is found on this substratum.The most important reasons for this choice of substratum can be summarised as follows:Cobbles and small boulders are generally widely available (riffles, cobble beds, benchesand shelves), throughout the length of a river from headwaters to lowland stretches, andthroughout the year.The type of stone sampled can usually be discounted when assessing the flora at aparticular site.The performance of major diatom-based indices on this substratum is well understood.The ecology of the epilithon is better known than any other group.1.2 Alternative substrata (in order of preference)Man made objects (bricks, pieces of concrete, bridge supports, cannel walls etc.).Emergent macrophytes, such as Typha spp. or Phragmites spp.Submerged macrophytes, such as Potamogeton spp, Ceratophyllum spp. etc. may be usedas an alternative substratum.1.3 Introduced substrataIf pebbles, cobbles, boulders or macrophytes are absent from the sample site, artificialsubstrata may be introduced into the stream. However sampling should only be attempted ifthey have been submerged for at least four weeks.The advantages of using introduced substrata include:the ease of sampling from smooth surfaces,greater control over the exact area of sampling,standardisation of substrata,less contamination by macrophytic algal growth andthe introduced substratum can be positioned exactly.Some disadvantages to using artificial substrata include:The community will be somewhat unnatural and biased towards those diatoms which arefast growing and can attach to flat, smooth surfaces,12
Page 1 and 2: A Methods Manual for theCollection,
Page 3 and 4: This report is part of a set on Dia
Page 5 and 6: FOREWORDThis method manual is inten
Page 7 and 8: TABLE OF CONTENTSNOTE TO THE USER .
Page 9 and 10: GLOSSARYAerophilic - Depending on f
Page 11 and 12: Phytoplankton - The phytoplankton c
Page 13 and 14: photomicrographs earned high praise
Page 15 and 16: 2. How do you recognise diatoms in
Page 17 and 18: 4. Diatoms - Colony formation and a
Page 19 and 20: 5.1 Pennate and Centric diatomsPenn
Page 24 and 25: depending on the period of exposure
Page 26 and 27: 2.3.2 Examination of fresh material
Page 28 and 29: 3. Toolkit for Fieldwork (field app
Page 30 and 31: 5. Site selection for water quality
Page 32 and 33: 6. Sampling locality details and fi
Page 34 and 35: 8. Choice of substrata (detail)Samp
Page 36 and 37: 10 Preservation of diatom material
Page 38 and 39: 1: Micro-pipette 1 ml with disposab
Page 40 and 41: 1.2 Pre-preparation examination of
Page 42 and 43: 1.3.2.3 Shake the sample well and p
Page 44 and 45: one is available the peroxide can b
Page 46 and 47: 2 Preparation of diatom slidesHealt
Page 48 and 49: 2.1.9 After the diatom-coated cover
Page 50 and 51: 4. ArchivingIt is important to reta
Page 52 and 53: affected at counts of 300 and above
Page 54 and 55: 6. Counting records (electronic and
Page 56 and 57: The main source of variability is,
Page 58 and 59: 11. Key reference worksThere are se
Page 60: HARDING WR, ARCHIBALD CGM, TAYLOR J

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