Aerial green algae

Aim follow the biological effects of mainly nitrogen and acidifying pollutants on an epiphyte which is almost wholly dependent on nutrients from the atmosphere Green algae, mainly Protococcus viridis (or Pleurococcus vulgaris or Desmococcus viridis), are sensitive to atmospheric deposition and especially favoured by nitrogen. Among other places they grow on needles of Norway spruce, which constitute a homogeneous substrate on which their amount and rate of colonisation may be easily described in a standardised way. The amount of needle-inhabiting algae and bark-inhabiting lichens and the number of annual whorls with needles left are observed annually on about twenty small spruces at each site. On each spruce three branches at eye-height are observed.   Variables thickness/amount (1-3) of algae/lichens and age of the youngest shoot carrying algae/lichens and number of annual shoots retaining living needles

Green algae, mainly Protococcus viridis establish themselves on needles of Norway spruce provided the climate is favourable and a supply of nutrients, mainly nitrogen, available. They are observed using a magnifying glass. (Söderåsen.)