Abstract:
Bivalves are considered to be ecosystem engineers, and an important component in New Zealand’s marine diversity. It is well supported that through the filter feeding processes of such organisms, excess nutrients and heavy metals are removed from the surrounding marine environment, often improving water quality. A series of tests were performed to discover the utility of bivalve aquaculture in urban environments within New Zealand. Initially a field experiment was trialed, however after biological and logistical difficulties, a laboratory based approach was adopted. A comparative study between the Green Lipped Mussel (Perna canaliculus), Pacific Oyster (Crassostrea gigas) and the M. galloprovincialis (Xenostrobus neozelanicus) was performed. Inductively coupled plasma mass spectrometry (ICP-MS) techniques were used to measure levels of selected elements (Mg, Al, Cd, Zn, Pb, Cu, Ni). A focus was then taken to the utilization of New Zealand’s native aquaculture species P. canaliculus to better understand the interactions between this species and an urban setting. Laser ablation inductively coupled plasma mass spectrometry techniques were used to measure the levels of elements (Mg, Al, Cd, Zn, Pb, Cu, Ni) retained by this species after 6 months of feeding in an urban marine environment. For the purpose of the study, four mesocosms were set up at Kelly Tarlton’s Aquarium, and water samples were measured on a weekly basis. This demonstrated the clearance rate of P. canaliculus over a period of 25 weeks, which was then used to better understand growth and feeding rates of the species within such an environment. Results demonstrated some statistical significance between the means of the species heavy metal uptake, however results between analytes vary. Furthermore, there was no statistical significance to show any increase in heavy metal accumulation within an urban environment measured over 25 weeks (P. canaliculus). Clearance rate shown by P. canaliculus increased over a period of 25 weeks, typical behaviour of bivalves from winter to summer seasonal changes. Results are consistent with current scientific publications, displaying promise that bivalve aquaculture has a positive effect on water quality.