Microphytobenthos in mussel farms - North Adriatic Sea (SosteMiTS Project) 2008-2009

Study Extent

The study was carried out in September 2008 and March 2009 in a coastal area of the Gulf of Trieste. Four sites, characterised by similar biogeochemical and geomorphological features, were chosen because subjected to a different degree of potential impact due to mussel farming: a twenty-year farm (45 45.140 N, 13 38.590 E); a four-year farm (45 45.060 N, 13 38.660 E); a farm disused for more than 12 years (45 44.930 N, 13 39.090 E) and a control site located 250 m ca. away from the farms (45 44.820 N, 13 39.060 E). In each site, sediment samples were collected at 5 stations (A, B, C, D, and E) located along the direction of the dominant current flux. The distance among stations was 6 m ca. At each station, 3 points (e.g. A1, A2, and A3), 1.5 m away from each other, were sampled.

Sampling

At each point, scuba divers collected 3 virtually undisturbed sediment cores using polycarbonate sample tubes (12.7 cm I.D) with a sample area of 127 cm^2. Subsamples of the upper 1.5 cm were taken for microphytobenthos analysis.

Method steps

1. For the microphytobenthic analyses, aliquots of 2 cm^3 of homogenised sediment were withdrawn using a syringe and directly fixed with 10 ml of formaldehyde (4% final concentration) buffered solution CaMg(CO3)2, in pre-filtered bottom seawater (0.2 ml filters). After manual stirring, 20 microlitter aliquots of the sediment suspension were drawn off from the slurries and placed in a counting chamber. Only cells containing pigments and not empty frustules were counted under a Leitz inverted light microscope (Leica Microsystems AG) using a 32X objective (320X final magnification) (Utermöhl, 1958).

1. Bacillariophyta
   common name: Diatoms

Gulf of Trieste: http://marineregions.org/mrgid/3385