Periphyton monitoring at Te Moenga Bay, 1985-1991

"This report is provisional only and should not be quoted without consulting the author or Director"

2 refs; 10 figs; 6 tables

Since 1984, a monitoring programme has been carried out on the periphyton of Te Moenga Bay (NZMS N94 513362). The aim of the programme was to identify any changes occurring in the periphyton in response to the expected enrichment of the bay, resulting from groundwater contamination following the construction of the Acacia Bay sewage works in its catchment (NZMS N94 508364). Early investigations in the project involved descriptive surveys of the area, and establishment of a control area unaffected by the development further north along the shore (NZMS N94 523369). These were followed by a series of point transects perpendicular (from 0 to 0.65 m depth) and parallel (10, 50 and 100 cm depth) to the shore, where the presence or absence of major periphyton communities were recorded. In addition, quantitative data on the biomass of #Enteromorpha nana# was obtained by clearing a series of quadrats and measuring dry weight. The biomass of epilithic cyanobacterial/diatom communities were estimated by measuring areal carbon content of epilithic communities. Samples were also examined qualitatively for species composition. In August 1985 a low intensity sampling strategy was drawn up which has continued to 1991. This involves 6-weekly sampling. At each sampling date duplicate water samples are collected for nutrient analyses at 10, 50 and 100 cm depth. From December 1986 the stream flowing into the bay (NZMS N94 451361) was also sampled, as this was expected to receive contaminated groundwater. Water temperatures are recorded (and sometimes light penetration), periphyton samples are taken from 10, 50 and 100 cm for qualitative species identification, and 15-20 quadrat samples are taken in 1m water depth along a line parallel to the shore, for #Enteromorpha# dry weight determination. This report summarises the information available to date. (auths.)