The feasibility of submerged macrophyte re-establishment in Kaituna Lagoon, Lake Ellesmere (Te Waihora)

Abstract

Submerged macrophytes play an important role in the ecology of many lakes, especially shallow wind-swept lakes such as Lake Ellesmere (Te Waihora) in the South Island of New Zealand. Since their destruction in the 1968 Wahine storm, the submerged macrophyte beds of Lake Ellesmere have not recovered to their past distribution, due to unfavourable within-lake conditions. This study addressed the feasibility of re-establishing the submerged macrophytes in Kaituna Lagoon, a part of the lake, using P. pectinatus as a facilitating plant. The effects of light and salinity on P. pectinatus growth were investigated in a 20 week growth experiment, along with salinity exposure experiments. Habitat surveys were carried out to determine growth conditions within Kaituna Lagoon.

Salinity and light limitation were important stress factors for the submerged macrophytes in this study. The lagoon experiences wide salinity and depth fluctuations, and has very low water clarity, hence low light penetration. It was concluded that Kaituna Lagoon was not a favourable site for submerged macrophyte re-establishment in Lake Ellesmere (Te Waihora) under current conditions.