European Ocean Biodiversity Information System

On October 25, 1994, the N.R.P. "S. Miguel," which was carrying a large amount of old military equipment, was sunk. The ship was sunk in the waters of the Portuguese continental EEZ, near the EEZ's outer edge and the Lisbon parallel. This sinking, which was attempted under controlled conditions under the Oslo Convention for the Prevention of Marine Pollution, was marred by a mishap, and the ship burst on the surface of the sea before sinking. In addition to the immediate impact of the N.R.P. "S. Miguel" explosion, which was attempted to detect based on a possible decrease in zooplanktonic biomass values in the surface water bed (200 m) in the immediate sinking area, it was also intended to know some "normal" bio-oceanographic conditions in order to detect possible future changes caused by pollutants on board the N.R.P. "S. Miguel". The epizooplanktonic material was sampled in oblique trawls up to a depth of 200 m using a Bongo 60 net (circular double-mouth net 60 cm in diameter and fitted with two mesh bags of 335 and 505 m aperture). The volume of water sampled in each haul was calculated using the readings of flowmeters attached to each net's mouth. Mesozooplankton was collected using a 10 m2 mouth area Isaacs-Kidd Midwater Raul (IKMT) net with a 505 m mesh bag. The hauls took around 30 minutes to complete at the desired depth. Study Extent The epizooplankton was collected in 12 sampling stations, which were distributed as follows: Three stations along the Portuguese coast, one at the sinking site, four surrounding the sinking site and ten miles apart, two at the Josephine bank and one at the Bank Gorringe. Method step description: All zooplanktonic material collected was kept in 4 percent neutral formalin, with the exception of a tiny portion of the material collected with IKMT that was frozen for examination of the concentration of heavy metals and PCBs. The biovolume of plankton samples was computed in the lab using the volume of water displaced by the organic material after large organisms (> 1 cm in epizooplankton and > 2.5 cm in mesozooplankton) were removed, and its abundance was calculated per 100 m3 of filtered water. Using a magnifying glass and a binocular microscope, species identification and enumeration were carried out in a counting chamber.