Lake Joondalup is a shallow body of fresh water in a calcareous stable dune system 6 km from the ocean. The fringing and aquatic vegetation is described. Cation ratios resemble sea water apart from relatively high calcium, attributed to leaching from limestone. Seasonal changes in volume greatly affect ionic concentrations. A bloom of the green alga Dispora coincides with low volume and high ion levels. Total nitrogen is relatively high compared with phosphorus. The surrounding land is becoming urbanized, and the data provide a baseline for future reference
