Abstract
Macroalgae play a critical role in the functioning of many coastal ecosystems, from rocky reefs to soft sediment environments. In the past, research focus has been placed predominantly on rocky reef systems with soft sediment habitats being relatively poorly understood. Soft sediment habitats can host extensive and diverse algal meadows that may serve as sites of significant ecological importance. This study examined the community dynamics of soft sediment macroalgal habitats in Otago Harbour, New Zealand. Adamsiella chauvinii, an endemic red alga, forms extensive meadows in soft sediment environments. The meadows play a key role in nutrient cycling, sediment stabilisation, and are known to support elevated species diversity including species of fisheries importance. Seasonal and spatial surveys were undertaken to assess biomass, community composition and species diversity within A.chauvinii beds in Otago Harbour, along with key predictors of algal growth (light, temperature and nutrient concentrations). Results show strong seasonal variation with biomass being the highest in autumn, along with a strong spatial variation with outer harbour recording higher biomass and species diversity. Environmental drivers of these patterns will be discussed. An unexpected finding across multiple sites was the presence of the invasive macroalgae Undaria pinnatifida which utilises A.chauvinii blades as a substrate for holdfast attachment and growth. This study provides detailed data about community composition, diversity, and distribution patterns across time and space, key information for driving effective ecosystem-based coastal management.
Oral presentation.