Seagrasses and algae

Tuggerah Lakes contains a diverse array of plant life (or "primary producers") that are the base of the food chain and perform many other important roles. Seagrasses and macroalgae, often mistakenly referred to as "weed", are two conspicuous primary producers that have very different characteristics.

The presence of seagrasses in the lakes indicates that the lakes are a relatively healthy ecosystem. Seagrasses are the ‘good guys’ when it comes to aquatic plants. Macroalgae and microalgae (tiny cells floating in the water column) are ‘good guys’ too when they grow at naturally low levels. Poor water quality, that is, high levels of nutrients/pollutants/sediment in the lake, favours the rapid growth of algae leading to macroalgal blooms in the nearshore zone and high levels of microalgae in the lake water. Reducing the amount of nutrients, pollutants and sediment in stormwater entering the lakes is the single most important way to improve the water quality in Tuggerah lakes.

Facts about seagrasses

eelgrass bed near Canton Beach

An eelgrass bed near Canton Beach

 

Seagrasses are flowering plants that evolved on land and moved to the oceans during the Cretaceous Period

  1. Three species are found in Tuggerah Lakes: eelgrass (ribbonweed), stackweed, and breamweed (paddleweed)
  2. Light, temperature, salinity, wave action, and sediment type all determine where they can grow
  3. They provide food and shelter for many birds, fish, invertebrates, and shellfish
  4. They stabilise the sediment, helping maintain clear water
  5. In the 1960s, seagrasses covered large areas of Tuggerah Lakes but as runoff from the catchment increased, light levels decreased, pushing seagrasses into the shallows.

Facts about macroalgae

photo of macroalgae. Photo courtesy of Office of Environment and Heritage

A species of green macroalgae.

 

Just like seagrasses, algae can be mistaken for a ‘weed’ too. In the Tuggerah Lakes the most visible algae are the large mats of macroalgae which the local fishermen call ‘wool’ or ‘slime’

  1. Macroalgae are a more primitive type of plant that does not flower or use a root system
  2. 30+ species are found in Tuggerah Lakes, from green “woolly” types to brown “leafy” types
  3. Light, temperature, salinity, wave action, and nutrient availability determine where they can grow
  4. They provide food and shelter for some juvenile fish and invertebrates
  5. Large “blooms” can occur when nutrients are available, which tends to indicate poor water quality.

 

 

 

Species of macroalgae

closeup_red_macroalga_Gracilaria. Photo courtesy of Office of Environment and Heritage

Gracilaria