Samples were collected as part of a FRST-funded freshwater biodiversity programme, between 1998 and 2004. Samples were collected from a range of freshwater habitats throughout New Zealand. Diatom species were listed from permanent slide mounts of diatom frustules (extracted from each sample by removing organic material using strong oxidisers). In most cases, the relative abundance of each species was noted using a scale of 1 (rare) to 5 (dominant). The slide collection is held at NIWA, with slides referenced by the sample number. Photographs of each specimen identified are held on NIWA's Atlas database.

Non-quantitative algae samples were collected from about 140 sites in ~45 wetlands throughout New Zealand. The wetlands sampled represented the "best available" in the regions sampled (i.e. all were relatively unimpacted). In general samples were from the west of the country as no eastern areas were considered to have unimpacted wetlands. At each site, where possible, an algae sample was collected from the benthos (sediment) and from submerged plants (epiphytic). The data on diatoms were obtained from counts of species on permanent slides prepared from the samples by acid-cleaning. The data are reported as relative abundnaces (%). The project was aimed at decribed the biodiversity of algae in wetlands and relating this to wetland characteristics.