[en] The processing of benthic diatoms is tedious and involves several potentially damaging steps for cells. Although the preservation of siliceous frustules is of paramount importance in the implementation of biotic indices, only few studies quantified treatment-induced cell losses. We assumed that commonly used treatments may lead to mechanical (centrifugation, sedimentation, boiling, sonication and mounting in Naphrax) and chemical (cold H2O2 digestion) damages on diatoms. We analysed the potential adverse effects of these treatments and the cleaning efficiency of H2O2 and incineration in order to find out the most suitable technique to process lightly silicified Mediterranean populations. Results showed that successive resuspensions of material after each concentration treatment (sedimentation and centrifugation) and low speed centrifugation did not alter the physical integrity of frustules. In contrast, boiling and sonication exhibited adverse effects especially on the preservation of large frustules and Naphrax mounting proved to be the most damaging step whatever the size of diatoms. For cleaning treatments, incineration provided the most satisfactory results and acted on a non-selective way as opposed to hydrogen peroxide which led to either a large number of non-cleaned frustules or dissolved valves. Our recommendations for processing samples of lightly silicified Mediterranean benthic diatoms include the use of low speed centrifugations, dehydration at room temperature, incineration and dry mounting.
Research center :
MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
Abrantes F, Gil I, Lopes C, Castro M (2005) Quantitative diatom analyses-a faster cleaning procedure. Deep-Sea Res 52: 189-198.
AFNOR NF EN 13946 (2003) Qualité de l'eau-Guide pour l'échantillonnage en routine et le prétraitement des diatomées benthiques de rivières. AFNOR, Saint Denis la Plaine.
Agatz M, Asmus RM, Deventer B (1999) Structural changes in the benthic diatom community along a eutrophication gradient on a tidal flat. Helgol Mar Res 53: 92-101.
Battarbee RW, Jones VJ, Flower RJ, Cameron NG, Bennion H, Carvalho L, Juggins S (2001) Diatoms. In: Smol JP, Birks HJB, Last WM (eds) Tracking environmental change using lake sediments, Volume 3: Terrestrial, algal, and siliceous indicators. Kluwer Academic, Dordrecht, pp 155-202.
Blanco S, Álvarez I, Cejudo C (2008) A test on different aspects of diatom processing techniques. J Appl Phycol 20: 445-450.
Brandini FP, da Silva ET, Pellizzari FM, Fonseca ALO, Fernandes LF (2001) Production and biomass accumulation of periphytic diatoms growing on glass slides during a 1-year cycle in a subtropical estuarine environment (Bay of Paranaguá, southern Brazil). Mar Biol 138: 163-171.
Busse S, Snoeijs P (2002) Gradient responses of diatom communities in the Bothnian Bay, northern Baltic Sea. Nova Hedwigia 74: 501-525.
Chessman BC, Bate N, Gell PA, Newall P (2007) A diatom species index for bioassessment of Australian rivers. Mar Freshwat Res 58: 542-557.
Clarke KR, Gorley RN (2006) PRIMER v6: user manual/tutorial. PRIMER-E, Plymouth.
Conley DJ, Kilham SS, Theriot E (1989) Differences in silica content between marine and freshwater diatoms. Limnol Oceanogr 34: 205-213.
Dela-Cruz J, Pritchard T, Gordon G, Ajani P (2006) The use of periphytic diatoms as a mean of assessing impacts of point source inorganic nutrient pollution in south-eastern Australia. Freshwat Biol 51: 951-972.
Flower (1993) Diatom preservation: experiments and observations on dissolution and breakage in modern and fossil material. Hydrobiologia 269/270: 473-484.
Gómez N, Licursi M (2001) The Pampean Diatom Index (IDP) for assessment of rivers and streams in Argentina. Aquat Ecol 35: 173-181.
Gurrieri JT (1998) Distribution of metals in water and sediment and effects on aquatic biota in the upper Stillwater river basin, Montana. J Geochem Explor 64: 83-100.
Hart TJ (1957) Notes on practical methods for the study of marine diatoms. J Mar Biol Assoc UK 36: 593-597.
Hasle GR, Fryxell GA (1970) Diatoms: cleaning and mounting for light and electron microscopy. Trans Am Microsc Soc 89: 469-474.
Hasle GR, Syvertsen EE, Steidinger KA, Tangen K (1996) Identifying marine diatoms and dinoflagellates. In: Tomas CR (ed) Identifying marine phytoplankton. Academic, New York, pp 387-584.
Hendey NI (1964) An introductory account of the smaller algae of British coastal waters: V. Bacillariophyceae (diatoms). Fishery Investigations Series IV. Her Majesty's Stationery Office, London, p XII.
Hickman M (1969) Methods for determining the primary productivity of epipelic and epipsammic algal associations. Limnol Oceanogr 14: 936-941.
Hillebrand H, Sommer U (2000) Diversity of benthic microalgae in response to colonization time and eutrophication. Aquat Bot 67: 221-236.
Karsten U, Schumann R, Rothe S, Jung I, Medlin L (2006) Temperature and light requirements for growth of two diatom species (Bacillariophyceae) isolated from an Arctic macroalga. Polar Biol 29: 476-486.
Kelly MG (2003) Short term dynamics of diatoms in an upland stream and implications for monitoring eutrophication. Environ Pollut 125: 117-122.
Kelly MG, Cazaubon A, Coring E, Dell'Uomo A, Ector L, Goldsmith B, Guasch H, Hürlimann J, Jarlman A, Kawecka B, Kwandrans J, Laugaste R, Lindstrøm EA, Leitao M, Marvan P, Padisak J, Pipp E, Prygiel J, Rott E, Sabater S, van Dam H, Vizinet J (1998) Recommendations for the routine sampling of diatoms for water quality assessments in Europe. J Appl Phycol 10: 215-224.
Martin-Jézéquel V, Hildebrand M, Brzezinski MA (2000) Silicon metabolism in diatoms: implications for growth. J Phycol 36: 821-840.
MacLulich JH (1987) Variations in the density and variety of intertidal epilithic microflora. Mar Ecol Prog Ser 40: 285-293.
McBride TP (1988) Preparing random distributions of diatom valves on microscope slides. Limnol Oceanogr 33: 1627-1629.
Munda IM (2005) Seasonal fouling by diatoms on artificial substrata at different depths near Piran (Gulf of Trieste, Northern Adriatic). Acta Adriat 46: 137-157.
Muniz P, Venturini N, Hutton M, Kandratavicius N, Pita A, Brugnoli E, Burone L, Garcia-Rodriguez F (2011) Ecosystem health of Montevideo coastal zone: a multi approach using some different benthic indicators to improve a ten-year-ago assessment. J Sea Res 65: 38-50.
Owen BB, Afzal M, Cody WR (1978) Staining preparations for phytoplankton and periphyton. Br Phycol J 13: 155-160.
Pan Y, Stevenson RJ, Hill BH, Herlihy AT (2000) Ecoregions and benthic diatom assemblages in Mid-Atlantic Highlands streams, USA. J N Am Bentholl Soc 19: 518-540.
Pickett-Heaps JD (1998) A rapid, highly efficient method for collecting, fixing, and embedding planktonic and other small cells for electron microscopy. J Phycol 34: 1088-1089.
Prygiel J, Coste M (1993) The assessment of water quality in the Artois-Picardie water basin (France) by the use of diatom indices. Hydrobiologia 269/270: 343-349.
Prygiel J, Coste M, Bukowska J (1999) Review of the major diatom-based techniques for the quality assessment of rivers-state of the art in Europe. In: Prygiel J, Whitton BA, Bukowska J (eds) Use of algae for monitoring rivers III. Agence de l'Eau Artois-Picardie, Douai (France), pp 224-270.
Reid FMH (1978) Permanent records. In: Sournia A (ed) Phytoplankton manual. UNESCO, Paris, pp 113-118.
Round FE, Crawford RM, Mann DG (1990) The diatoms: biology and morphology of the genera. Cambridge University Press, London.
Ryves DB, Battarbee RW, Juggins S, Fritz SC, Anderson NJ (2006) Physical and chemical predictors of diatom dissolution in freshwater and saline lake sediments in North America and West Greenland. Limnol Oceanogr 51: 1355-1368.
Sabater S, Gregory SV, Sedell JR (1998) Community dynamics and metabolism of benthic algae colonizing wood and rock substrata in a forest stream. J Phycol 34: 561-567.
Taylor JC, De la Rey PA, van Rensburg L (2005) Recommendations for the collection, preparation and enumeration of diatoms from riverine habitats for water quality monitoring in South Africa. Afr J Aquat Sci 30: 65-75.
Taylor JC, Prygiel J, Vosloo A, De la Rey PA, van Rensburg L (2007) Can diatom-based pollution indices be used for biomonitoring in South Africa? A case study of the Crocodile West and Marico water management area. Hydrobiologia 592: 455-464.
Totti C, Cucchiari E, De Stefano M, Pennesi C, Romagnoli T, Bavestrello G (2007) Seasonal variations of epilithic diatoms on different hard substrates in the northern Adriatic Sea. J Mar Biol Assoc U K 87: 649-658.
Underwood GJ, Phillips J, Saunders K (1998) Distribution of estuarine benthic diatom species along salinity and nutrient gradients. Eur J Phycol 33: 173-183.
US Geological Survey (1987) Methods for collection and analysis of aquatic biological and microbiological samples. In: Britton LJ, Greeson PE (eds) Techniques of water-resources investigations of the United States Geological Survey. Chapter A4. US Geological Survey, Golden, pp 127-150.
Vermeulen S, Sturaro N, Gobert S, Bouquegneau JM, Lepoint G (2011) Potential early indicators of anthropogenically derived nutrients: a multiscale stable isotope analysis. Mar Ecol Prog Ser 422: 9-22.
Zoto GA, Dillon DO, Schlichting HE (1973) A rapid method for clearing diatoms for taxonomic and ecological studies. Phycologia 12: 69-70.
