The effects of prolonged darkness on temperate and tropical marine phytoplankton, and their implications for ballast water risk management.

Phytoplankton assemblages from tropical (Goa) and temperate (UK) locations were exposed to a 28 day dark period, followed by a period of re-exposure to light. During this time phytoplankton survival and changes in nutrient concentrations were mapped. The tropical plankton water samples showed high nutrient levels after the dark period which were utilised by cells during the re-exposure period. UK experiments looked at the effect of three different water types on population recovery after the 28 day dark period, and differences due to seasonal effects. The population growth observed during the re-exposure period in the tropical population was comparable to that of the temperate population. Water type affected recovery and of the three tested media fresh seawater promoted the highest levels of growth. Seasonality had a significant influence on species survival. Understanding the effects of all these factors can aid the development of effective risk assessments in ballast water management.

The measurement of the drag characteristics of tin-free self-polishing co-polymers and fouling release coatings using a rotor apparatus.

An experimental study was carried out to compare the drag characteristics of a tin-free self-polishing co-polymer (SPC) and a foul release coating. Rotor measurements were carried out using different cylinders coated with both paint types. The experiments showed that the frictional resistance for the foul release test cylinders was lower than for the tin-free SPC cylinders. The drag characteristics were related to the roughness parameters of the tested surfaces measured with an optical measurement system. The measurements indicated that the texture of the foul release surface was significantly different from SPC systems. The findings show that the drag of a foul release coating will only correlate with a characteristic roughness measure that takes both the amplitude and the texture of the surface into account, and that is calculated at bandwidth parameters which depend on the degree of roughness.