Shoot and abundance characteristics of the seagrass Heterozostera tasmanica in Westernport estuary (south-eastern Australia)

Abstract

From March 1998 to 1999, the spatial and temporal variation in shoot and abundance characteristics of the seagrass, Heterozostera tasmanica (Martins ex Aschers) den Hartog were examined in Westernport, an estuarine embayment in south-eastern Australia. Seagrass characteristics were investigated at three sites: Charing Cross; Crib Point; and Newhaven. In the north (Charing Cross), waters are highly turbid and subject to high nutrient inputs from catchment sources, while in the south (Newhaven) waters are primarily oceanic. Crib Point represents an intermediary region in water quality. Temporal patterns in shoot parameters (leaf weight per shoot, leaf and stem weight per shoot, number of clusters per shoot and leaf surface area per shoot) of H. tasmanica were highly site dependent and were generally 2–4-fold higher at Newhaven compared to Charing Cross; consistent with improved water quality from north to south in Westernport. Seagrass abundance parameters (above-ground biomass and shoot density) also differed between sites with 1–2-fold higher values at Newhaven relative to the other sites. Relationships between shoot and physico-chemical parameters indicate that light availability is the primary factor influencing the growth of intertidal H. tasmanica meadows in Westernport.