The rot disease of Laminaria occurs often in nurseries of sporeling and commercial cultivation in the sea and results in economic loss greatly.Usually the disease outbreaks accompanied with massive multiplication of alginic acid decomposing bacteria.From the section of the decaying Lamuutria which resulted from the inoculation of alginic acid decomposing bacteria,it was observed that the bacteria invaded the epiderm of the Laminaria surface at first,then entered the ex-odermis,endodermis and pith.In addition,there were a great amount of bacteria in the intercellular region and a lot of free cells of the algae in the decaying areas.The wall of some free cells was decomposed,which led to soft tissue or disintegration.Alginic acid decomposing bacteria are normal epiphytic microorganisms growing on Lamuutria surface.These bacteria do not cause disease at normal environmental conditions.The experiments showed that the unfavourable conditions,e.g.,wounding,overcrowding,high temperature reduced the ability of antibacterial activity and made the algae more susceptible to the pathogens and favoured the multiplication of alginic acid decomposing bacteria and finally led to the disease outbreat.1le unfavourable environmental factors which resulted from a variety of reasons were the main cause of the disease.
Immediately following a spill at sea, released oil-ranging from diesel to light crude and diluted bitumen, will initially weather through evaporation, resulting in an elevated concentration of light hydrocarbons in the air. As part of oil spill response operations, first responders use hand-held devices to monitor airborne concentrations when approaching a spill. The feasibility of using numerical modelling as an additional tool to assess potential flammability and plan response operations in the spill area was explored in this study. The Lower Explosive Limit (LEL) is defined as the minimum concentration of a gas in air, in this case a mixture of evaporated hydrocarbons, which can produce a flash fire in the presence of an ignition source. This ignition source could be triggered by the vessel itself or by spill response operations. A framework was put into place, utilizing a three-dimensional hydrodynamic model (H3D), an oil spill model (SPILLCALC), and an air dispersion model (CALPUFF) to assess the risk of possible ignition of the hydrocarbon vapour in the event of a spill. The study looked at a hypothetical credible worst case tanker spill (16 500 m3) of diluted bitumen (cold lake winter blend) occurring at Arachne Reef in Haro Strait, British Columbia, Canada. SPILLCALC provided one-minute averaged vapour fluxes from the water surface for each of 17 modelled pseudo-components which were used as inputs to CALPUFF. Using the predicted airborne concentrations of each pseudo-component, time-scaled to one-second averages, the flammability potential in the immediate spill area was determined at each grid point using Le Chatelier's mixing equation. The approach describe here was developed as a proof of concept, and could be established as a real-time system, bringing valuable information in addition to hand-held devices during a spill response, or during a response exercise. This modelling study was conducted as part of Kinder Morgan's Trans Mountain Pipeline Expansion Project. There are a number of commercially available oil spill models but few if any are equipped with the ability to model air dispersion and forecast hazardous conditions as discussed in this paper.