The Effect of Suspended Sediment Loads on the Growth, Oxygen Consumption and Mucus Production of Pāua (Haliotis iris)

Land based-effects, including sedimentation are threatening estuarine and coastal systems globally. Ecological systems are faced with significant pressures from human activities including toxic pollution, eutrophication, habitat fragmentation and sedimentation. In recent years sediment inputs into marine systems have been greatly accelerated through land-based activities such as urban-land use, agriculture, coastal developments, large scale land clearances and farming. Effects of sedimentation on marine organisms include suffocation, reduced foraging efficiency and clogging of the gills of filter feeders.  In New Zealand, sedimentation is the most important land-based stressor on the coastal marine environment. The pāua (Haliotis iris), is an important macroalgal grazer and is one of New Zealand’s top 10 seafood exports. However, little is known about the effects suspended sediments have on H. iris. The aim of this thesis is to experimentally test the effects of suspended sediment on the growth, oxygen consumption and mucus production for H. iris, using sediment concentrations that would naturally occur within Wellington Harbour, New Zealand.  Suspended sediment had no significant effect on H. iris growth or oxygen consumption. However, exposure to suspended sediments significantly reduced mucus production in H. iris. There were also trends in the data to suggest that respiration in smaller H. iris was reduced by suspended sediments.  Limited studies have explored the effect of suspended sediments on gastropods, even though sedimentation is one of the most significant land based stressors on the marine environment, not only in New Zealand, but also worldwide. This study has led to a better understanding of the potential implications suspended sediment may incur for not only H. iris, but also Haliotis species in general.