Appendix 1: Glossary of common limnological terminology used in this report
- Epilimnion
- The surface water mass in a lake above the thermocline (see stratification), which is well mixed and therefore of uniform temperature; the surface mixed layer.
- Eutrophic
- High in nutrient concentration (hence eutrophication – nutrient enrichment of a waterbody, usually leading to growth and proliferation of plant material). See Table 4 for definitions of other trophic states in lakes.
- Hypolimnion
- The deepwater layer below the thermocline (see stratification) in a stratified lake.
- Littoral zone
- The shallow or inshore regions of a lake, defined as water shallow enough for the lake to be colonised by aquatic macrophytes.
- Monomixis (adj. monomictic)
- Mixing once a year. Water in monomictic lakes usually stratifies into layers over summer and mixes in autumn and winter. Most of the deeper lakes in New Zealand are monomictic.
- Oligotrophic
- Low in nutrients, hence with relatively low organic productivity; the opposite of eutrophic.
- Photic zone
- The surface waters of a lake where penetrating light has sufficient intensity to allow photosynthesis by aquatic plants.
- Polymixis (adj. polymictic)
- Frequent mixing; ie, lakes in which the water column undergoes frequent periods of stratification and re-mixing. Typical of shallow lakes, especially in lowland regions.
- Profundal zone
- The bottom of a deep lake, below the euphotic and littoral zones.
- Stratification
- Separation of layers of water in lakes because of different densities. Classically described from temperature effects, where water layers of approximately uniform temperature (the epilimnion and hypolimnion) are separated by a steep temperature gradient (the thermocline); it may also be driven by differences in salinity.
