Preprint volume - SIBM
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Preprint volume - SIBM

Preprint volume - SIBM Preprint volume - SIBM

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19.06.2013 Views

Pre-print Volume – Posters PLANKTON COMMITEE G. BOTTINELLI, T. DI FESTA, A.M. PASTORELLI, N. UNGARO, M.R. VADRUCCI * ARPA Puglia – Regional Agency for the Environmental Protection and Prevention, Dipartimento Provinciale di Bari, Via Oberdan, 18 - 70126 Bari, Italia. a.pastorelli@arpa.puglia.it * ARPA Puglia, Dipartimento Provinciale di Lecce, Via Miglietta, 2 - 73100 Lecce, Italia. NUMERICAL ABUNDANCE AND NUMBER OF TAXA IN PHYTOPLANKTON SAMPLES: PRELIMINARY COMPARISON BETWEEN TWO DIFFERENT COUNTING STRATEGIES DETERMINAZIONE DELLA DENSITÀ CELLULARE E DEL NUMERO DI TAXA IN CAMPIONI DI FITOPLANCTON: CONFRONTO PRELIMINARE TRA DUE STRATEGIE DI CONTEGGIO Abstract – The comparison between two different counting procedures for the analysis of phytoplankton samples was reported in this study. The comparison was made on 10 seawaters samples, collected monthly from October 2009 to December 2009 in the marine coastal waters of the Apulia region (southern Italy). The samples were analyzed according to the Utermöhl’s method using two counting procedures of the sedimentation chambers: counting random field and counting sectors. The results showed significant differences between the two counting procedures. Key-words: phytoplankton, counting procedures, Mediterranean Sea, Adriatic Sea, Ionian Sea. Introduction – Phytoplankton is one of the Biological Element considered suitable for the assessment of the environmental status of marine coastal waters, as it was stated by the Water Framework Directive (EC/2000/60) and other National Acts. As a consequence, the monitoring of phytoplankton guilds (abundance and composition) is currently carried out by the Regional Agency for the Environmental Protection and Prevention (ARPA) along the Apulia marine coastal areas. Phytoplankton guilds were analyzed following the Utermöhl’s method (1958), currently certified by UNI-EN 15204 (2006). In this study, preliminary results about the statistical comparison between two different counting procedures are reported. Materials and methods – Seawater samples were collected monthly from October 2009 to December 2009 in 7 stations, 5 located along the Adriatic coast (Ofanto river mouth, Bari, Monopoli, San Cataldo and Alimini lagoon mouth) and two along the coast of the Ionian Sea (Porto Cesareo and Ugento). Seawater samples were collected by means of a Niskin bottle in the sub-surface layer (0.5 m), kept in PET dark bottles, fixed with Lugol's solution and analyzed within one month from the sampling. The comparison of the two counting procedures was carried out only on 10 seawater samples collected for phytoplankton analysis. After cell settlement, in 25 ml or 10 ml sedimentation chambers, each sample was counted by means of two different counting procedures envisaged by the Utermölh’s method: 1) counting on random fields; 2) counting on portions of the sedimentation chambers (sectors). For the former counting procedure, a number of random fields were counted until a total of 400 cells were reached (corresponding to 5-10% accuracy). On the contrary, the second counting procedure is a modification of counting the whole chamber procedure, considered more appropriate for water samples with low phytoplankton densities (EN 15204). The whole sedimentation chamber was divided into 8 sectors. 41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010 335

Pre-print Volume – Posters PLANKTON COMMITEE The cells were counted in a number of sectors until reaching at least 400 cells and, in any case, until the end of the sector or sectors included in the analysis. The cell densities was calculated according to the formula: N=(n*1000/v)*f, where: N = number of cells per unit volume; n= number of cells counted; v=volume of sedimentation chambers; f=total sectors/number of the counted sectors. In both procedures, rare species were counted on the whole chamber. The results of total cell density and number of taxa obtained using the two alternative methods were compared using the regression analysis. Results –Cell density values showed significant differences between the two counting methods. Cell density values observed using the “fields” counting procedure appeared to be higher than those obtained by counting phytoplankton cells on “sectors”. Regression analysis was positive and highly significant: r=0.999, p

Pre-print Volume – Posters<br />

PLANKTON COMMITEE<br />

The cells were counted in a number of sectors until reaching at least 400 cells and, in<br />

any case, until the end of the sector or sectors included in the analysis. The cell<br />

densities was calculated according to the formula: N=(n*1000/v)*f, where: N =<br />

number of cells per unit <strong>volume</strong>; n= number of cells counted; v=<strong>volume</strong> of<br />

sedimentation chambers; f=total sectors/number of the counted sectors. In both<br />

procedures, rare species were counted on the whole chamber. The results of total cell<br />

density and number of taxa obtained using the two alternative methods were compared<br />

using the regression analysis.<br />

Results –Cell density values showed significant differences between the two counting<br />

methods. Cell density values observed using the “fields” counting procedure appeared<br />

to be higher than those obtained by counting phytoplankton cells on “sectors”.<br />

Regression analysis was positive and highly significant: r=0.999, p

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