Date of Award

1996

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Science, Technology and Engineering

First Advisor

Dr Paul Lavery

Second Advisor

Dr Sjaak Lemmens

Abstract

Sabella spallanzanii, a filter feeding, sabellid polychaete worm which is common in the Mediterranean Sea, was recently discovered in Cockburn Sound, Western Australia. The species has been in Port Phillip Bay, Victoria for about 10 years, where it has spread widely, competes with native species and has economic impacts on the local scallop fishery. In Cockburn Sound, S. spallanzanii has colonised a shallow, sandy area known as the Southern Flats, reaching a mean biomass of 258 gDW m2 , as well as almost all artificial structures such as jetties and navigational marker pylons. A large biomass of this introduced filter feeder may have a considerable filtration capacity which could control levels of phytoplankton in the Sound. This study measured the biomass and filtration rate of S. spallanzanii to determine its potential to effect phytoplankton levels in Cockburn Sound through filter feeding. The results suggest that these polychaetes have a substantial filtering capacity, capable of filtering the water-column above them at the Southern Flats (5m depth) 4.6 times daily. To determine the feeding efficiency of S. spallanzanii (volume of water filtered per metabolic demand), the oxygen consumption and filtration rate were measured. Feeding efficiency, which may provide an indication of the potential spread of S. spallanzanii to less eutrophic waters, increased with temperature from 13°C, reaching an optimum at 22°C. Between 22 - 27°C the feeding efficiency decreased sharply, indicating that its upper temperature limit is approached. To meet its metabolic requirements, S. spallanzanii requires a phytoplankton concentration with a chlorophyll a level of 1.42 µg L1 in winter (17°C) and 0.73 µg L1 in summer (22°C). It was concluded that the feeding efficiency of S. spallanzanii may limit it to eutrophic harbours with a high level of phytoplankton.

Share

 
COinS