Settlement and growth of the mussels (Mytilusgalloprovincialis,Lamarck, 1819) on different collectors suspended from an offshore submerged longline system in the Black Sea

A study of spat settlement of a submerged longline mussel culture system was carried out in Sinop area, Black Sea, between May 2008 and May 2009. The effects of six different types of collectors on spat settlement and growth were investigated. Six different types of spat settlement rope were used as polypropylene ropes with 18 mm diameter, 18 mm diameter timeworn silk rope, 22 mm diameter rope made from old hawser (OSR), 22 mm diameter ropes made from old anchovy net without pegs, 18 mm diameter old used nylon ropes and 18 mm diameter tasselled polypropylene ropes. Monthly temperature, salinity, chlorophyll‐a, total suspended matter, inorganic matter and organic matter were determined during the experimental period. The best settlement was observed on the OSR type when measured per metre (3450.00 ± 125.83 ind m^?1). Consequently, the findings showed that settlement preference of spat occurred according to rope structure, and if ropes are designed to combine numerous well‐fixed tassels, spat settlement can increase. Spat growth was affected by environmental factors and rope structure. In addition, the study revealed a negative relationship between density and growth.     

Studies of forest floor biological activities in an area previously damaged by sulphur dioxide emissions

As part of an environmental control program aimed to assess possible future effects of air contaminants from a new destruction plant for hazardous chemical residuals in Central Sweden, a study was undertaken the year before the plant went into operation to collect base-line information on biological activities in the soils of the surrounding forests. Measurements were made of N-mineralization, respiration, phosphatase-, dehydrogenase-, and nitrogenase activity on sieved samples from the forest floor (0 to 3 cm). The results were evaluated in relation to a previous contamination of the area by air pollutants from a plant for oil production. This plant produced oil from the local alun shale between 1942 and 1966. During these years somewhere between 6 × 10⁵ and 1.2 × 10⁶ tonne of S, mainly in the form of SO₂, were released into the atmosphere. The results showed that the forest floor was not especially acid when compared to similar sites in locally unpolluted areas. The concentration of Cu, however, was five times higher than expected. No disturbances could be detected as regards N-mineralization, respiration or phosphatase activity. Dehydrogenase- and nitrogenase activity were much more difficult to evaluate. A suppression of dehydrogenase activity was indicated on the study plots closest to the previous plant. In the case of nitrogenase activity no appropriate reference material was available to judge whether disturbances existed.