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What are algae? Algae are plant-like aquatic organisms, many of which are single-celled, but others grow in mats or filaments. Algae are the basis of most aquatic food webs, they produce oxygen to the atmosphere, absorb nutrients and can be a good indicator of water quality.

Why are we recording the current state of our freshwaters? We measure the current state of our rivers, streams and lakes to get an idea about whether our water is suitable for use for various purposes, and about the effect of different pressures (e.g. urbanisation, farming, etc.) on the condition of...

A trend in water quality data indicates that measured values have been overall rising or falling over a time period.  LAWA displays trends for the last 5, 10 and 15 years for the river and lake water quality data. A trend may be classified as indeterminate if there is insufficient evidence to determ...

Chlorophyll a is the green pigment in plants and algae that is used for photosynthesis. Measuring how much of this pigment is in the water provides a good indicator of the total amount (or biomass) of algae in a lake.  View a factsheet on Algae and Cyanobacteria in Lakes.

The Trophic Level Index (TLI) is a method of characterising the ecological health of lakes based on the amount of nutrients and algae growing in them.  It provides an integrated measure of water quality that can be tracked over time and that can be used to estimate biological productivity.  It is pr...

New Zealand Lakes Lakes are localised bodies of water that are surrounded by land. They may be fed by, or feed into rivers or may be maintained by rainfall and groundwater inputs. Lakes exist in all shapes and sizes and may be natural (for example formed by glaciation or landslides) or man-made (for...

What are marine algal blooms? Algal blooms can appear in the marine environment when weather conditions like wind and water currents are favourable. Areas with slow water circulation and high water temperatures can often experience bloom events. Algal blooms are comprised of algae, or aquatic plants...

Most estuary monitoring is carried out by regional councils and unitary authorities, who are responsible for managing the sustainable use of natural resources in their region and have a duty to gather and record information on the State of the Environment (SOE).  Other agencies that undertake monito...