Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 209-228). Also available via the World Wide Web.

Thesis (Ph.D.)--University of Waikato, 2006. / Includes bibliographical references (leaves 135-150)

Coastal metal pollution is a major concern to the health and well-being of aquatic organisms. Bioindicator organisms such as mussels have the potential to monitor coastal metal pollution. In New Zealand, the feasibility of employing green-lipped mussels, Perna canaliculus as a bioindicator species is yet to be investigated. This thesis focuses on applying a suite of biomarkers on green-lipped mussels exposed to cadmium (Cd) to evaluate the utility of the biomarkers and investigate the utility of the mussels in assessment of metal pollution. Cd is a non-essential metal and is known to be highly toxic to many aquatic organisms. This research consisted of a laboratory study to understand the mechanistic effects of Cd toxicity in green-lipped mussels. Physiological, biochemical, immunocytotoxic and cytogenotoxic biomarker responses were measured in mussels exposed to acute (96 h; 2000 µg L⁻¹ and 4000 µg L⁻¹) and subchronic (28 d; 200 µg L⁻¹ and 2000 µg L⁻¹) Cd treatments. The 96 h LC₅₀ value for P. canaliculus was 8160 µg L⁻¹, indicating that the green-lipped mussels were relatively tolerant to Cd exposure. Results from the Cd exposures, indicated that Cd had a negative impact on physiological processes such as feeding and oxygen consumption. Cd-induced physiological impairments caused an imbalance between energy gain and energy loss in the mussels that led to negative scope for growth. Detoxification (metallothionein-like protein) and defence mechanisms (catalase) were induced in the mussels to provide protection against the toxic effects of Cd. However, the defence mechanisms were not sufficient to protect the mussels from damage due to lipid peroxidation. DNA damage was also observed in the haemocytes of mussels as a result of Cd exposure. Cellular homeostasis (alkaline phosphatase) mechanisms were also perturbed. The immunocytotoxic endpoints reflected differences in haemocyte proportions in the haemolymph of Cd-exposed mussels. Exposure to Cd also led to the formation of several nuclear aberrations in the gill cells of mussels. Overall the laboratory study highlighted toxic effects of Cd on green-lipped mussels that were dependent on the dose and/or the duration of exposure to Cd. Among the biomarkers tested, clearance rate, metallothionein-like protein induction and the formation of nuclear aberrations in mussel gill cells correlated strongly to Cd accumulation levels and reflected Cd exposure effects. The feasibility of employing green-lipped mussels as bioindicators was tested during the field study. Green-lipped mussels were collected from different coastal sites along the South Island in NZ. Metal concentrations in the sediment and in four different mussel tissues were analysed. The findings indicated a significant geographical difference in metal concentration in the environment and in the metal accumulation levels in the mussels. Overall, the field study indicated that the green-lipped mussel, Perna canaliculus has the potential to be used as a bioindicator species for assessment of coastal metal pollution levels in NZ.

Biofouling pests, including non-indigenous species, can have significant impacts on anthropogenic activities. This is particularly true for aquaculture industries, where biofouling communities grow on crop species and infrastructure, potentially reducing revenue and increasing processing and production costs. It is of interest to marine farmers and scientists to gain a better understanding of the processes facilitating the regional proliferation and spread of biofouling pests. The structure of biofouling communities associated with marine farms in New Zealand’s main mussel growing region, Pelorus Sound, are characterised in this thesis. The patterns of connectivity and gene flow among biofouling populations are also investigated. Images and video footage of biofouling on mussel farms (Perna canaliculus) indicate strong spatial variation in the structure of biofouling communities, with a dominance of known problematic taxa and high wave energy tolerant species, such as the brown alga Undaria pinnatifida and the calcareous tubeworm Pomatoceros sp., near the entrance of Pelorus Sound. Genetic analyses and simple GIS-based modelling of a case study biofouling organism, Didemnum vexillum, revealed genetic differentiation among populations with extreme outcrossing and low levels of connectivity. Genetic analyses also suggest that anthropogenic-assisted dispersal may be vital for connecting certain D. vexillum populations compared to natural spread. The present study illustrates how multidisciplinary research approaches can be used to identify geographical areas that are less prone to biofouling and to inform the management of biofouling pests and invasive species in aquaculture environments.

The current explanation for the absence, or low abundance, of filter-feeding invertebrates from some rocky shores is that because of local variation in nearshore oceanographic conditions, larvae do not arrive in sufficient numbers to establish populations. One putative consequence of this is that macroalgae are able to establish dominance in areas where filter-feeders (especially mussels) do not recruit well. While macroalgae have been transplanted to mussel-dominated shores with varying success, the survival, growth and reproduction of transplanted mussels has not been tested in areas dominated by macroalgae. To determine specifically what tips the balance between shores dominated by filter-feeding invertebrates and those dominated by macroalgae, I monitored the recruitment of intertidal mussels at four sites on the Kaikoura coast: two with mussels present and two algal-dominated. No significant differences in mussel recruitment rates were found between habitats and recruitment intensity at all sites was found to be very low. Recruitment limitation is not the reason for the absence of mussels from algal dominated shores but some form of limitation does occur to reduce the number of arriving mussels. Predation effects were examined by transplanting juvenile mussels into caged, uncaged and control treatments. No significant differences in predation rates between habitats were found and transplanted mussels in open cages at all sites were removed within 3 days. Mobile fish predators appeared to be the most likely cause of this intense predation. Growth of transplanted mussels into algal and mussel habitats was found to be significantly different. Mussels grew faster in mussel dominated habitats and after 6 months in algal dominated habitats, all mussels had died. The outcome of these experiments indicates that there is a close relationship between recruitment, survival and growth which tips the balance and allows the existence of mussel beds along the Kaikoura coastline.

The current explanation for the absence, or low abundance, of filter-feeding invertebrates from some rocky shores is that because of local variation in nearshore oceanographic conditions, larvae do not arrive in sufficient numbers to establish populations. One putative consequence of this is that macroalgae are able to establish dominance in areas where filter-feeders (especially mussels) do not recruit well. While macroalgae have been transplanted to mussel-dominated shores with varying success, the survival, growth and reproduction of transplanted mussels has not been tested in areas dominated by macroalgae. To determine specifically what tips the balance between shores dominated by filter-feeding invertebrates and those dominated by macroalgae, I monitored the recruitment of intertidal mussels at four sites on the Kaikoura coast: two with mussels present and two algal-dominated. No significant differences in mussel recruitment rates were found between habitats and recruitment intensity at all sites was found to be very low. Recruitment limitation is not the reason for the absence of mussels from algal dominated shores but some form of limitation does occur to reduce the number of arriving mussels. Predation effects were examined by transplanting juvenile mussels into caged, uncaged and control treatments. No significant differences in predation rates between habitats were found and transplanted mussels in open cages at all sites were removed within 3 days. Mobile fish predators appeared to be the most likely cause of this intense predation. Growth of transplanted mussels into algal and mussel habitats was found to be significantly different. Mussels grew faster in mussel dominated habitats and after 6 months in algal dominated habitats, all mussels had died. The outcome of these experiments indicates that there is a close relationship between recruitment, survival and growth which tips the balance and allows the existence of mussel beds along the Kaikoura coastline.

Although there are no authenticated records of human illness due to PSP in New Zealand, nationwide phytoplankton and shellfish toxicity monitoring programmes have revealed that the incidence of PSP contamination and the occurrence of the toxic Alexandrium species are more common than previously realised (Mackenzie et al., 2004). A full understanding of the mechanism of uptake, accumulation and toxin dynamics of bivalves feeding on toxic algae is fundamental for improving future regulations in the shellfish toxicity monitoring program across the country. This thesis examines the effects of toxic dinoflagellates and PSP toxins on the physiology and behaviour of bivalve molluscs. This focus arose because these aspects have not been widely studied before in New Zealand. The basic hypothesis tested was that bivalve molluscs differ in their ability to metabolise PSP toxins produced by Alexandrium tamarense and are able to transform toxins and may have special mechanisms to avoid toxin uptake. To test this hypothesis, different physiological/behavioural experiments and quantification of PSP toxins in bivalves tissues were carried out on mussels (Perna canaliculus), clams (Paphies donacina and Dosinia anus), scallops (Pecten novaezelandiae) and oysters (Ostrea chilensis) from the South Island of New Zealand. Measurements of clearance rate were used to test the sensitivity of the bivalves to PSP toxins. Other studies that involved intoxication and detoxification periods were carried out on three species of bivalves (P. canaliculus, P. donacina, P. novaezelandiae), using physiological responses (clearance and excretion rate) and analysis of PSP toxins in the tissues over these periods. Complementary experiments that investigated other responses in bivalves fed with the toxic cells were also carried out. These included byssus production, and the presence of toxic cells in the faeces of mussels, the siphon activity and burrowing depth in clams and the oxygen consumption in scallops. The most resistant species to PSP toxins were the mussel, Perna canaliculus and the clam, Dosinia anus. Both species fed actively on toxic dinoflagellates and accumulated toxins. The intoxication and detoxication rate of the mussel was faster than the other species of bivalve studied (P. donacina and P. novaezelandiae) which confirm mussels as a good sentinel species for early warning of toxic algal blooms. The clearance rate of the clam, Paphies donacina decreased when fed on Alexandrium species but the effect of the PSP toxins on this physiological response was not confirmed. Over the detoxification period of 8 days, this clam did not detoxify which suggests that its ability to retain high level of toxins for an extensive period may be critical for public health management. The scallop, Pecten novaezelandiae was clearly the most sensitive species to the PSP toxins and the clearance rate was significantly lower in the presence of the toxic dinoflagellate A. tamarense. Although the clearance rate was low, the scallops still fed on the toxic dinoflagellate and accumulated PSP toxins in the tissues. The scallops detoxified slowly which would affect the market for this bivalve in the presence of a toxic algal bloom. This bivalve would retain PSP toxins for longer period of time than other species such as mussels. The oyster, Ostrea chilensis, had erratic clearance rate and did not respond clearly to any of the variables tested over the time. Oysters accumulated more toxins than the sensitive species, but they had been exposed to two more days of feeding with A. tamarense; therefore this species may actually have a similar intoxication responses to P. novaezalandiae and P. donacina. The results from this thesis suggest further directions for the aquaculture sector and ongoing research in this field, which in future will lead to a better selection of suitable species for culture as well as species for monitoring of PSP toxins. In the future, research that integrates field and controlled laboratory studies will expand to other species of interest and a more complete record will in time be available in order to manage more efficiently the negative effects that harmful algal blooms may have in New Zealand.

The biogeographic distribution of organisms is determined by physiological characteristics that enable a population to persist in a specific location. Global climate change effects are anticipated to increase the physiological stress experienced by organisms. Consequently, it is important to understand physiological responses to environmental stress and the mechanisms used by animals to cope with variable conditions. I investigated the physiological response to environmental stress in two species of mussel from New Zealand, Perna canaliculus and Mytilus galloprovincialis, using quantitative PCR and ecological field experiments. A series of laboratory and field experiments were done to manipulate stress levels and the expression levels of three heat shock protein genes (hsp24, hsp70, hsp90) were measured. A transcription regulatory gene (elf2) and a cell cycle regulatory gene (tis11d) were also measured. The dynamics of stress response gene expression in response to acute stress and gene expression changes in the natural population due to varying forms of environmental stress were tested. Between-zone translocations of different sized M. galloprovincialis and P. canaliculus were done at two sites in both east and west regions of the South Island of New Zealand. Site was found to be the most important factor in stress response. Apparent low food and high exposure stress interacted to create the particularly elevated stress response at the Timaru site. The adaptive ability of mussels transplanted between sites with varying environmental conditions was also tested. Results suggest that acclimation may be limited under stressful conditions. Furthermore, I found that P. canaliculus, the predominantly low-zone species, had a lower stress response than M. galloprovincialis, which was contradictory to predictions. The investigations described in this thesis suggest that interactive effects of abiotic stress and food limitations are particularly challenging for animals. With the severity of climate change scenarios predicted, changes in water quality and aerial and seawater temperature suggest mussel populations are likely to be negatively affected in the future. This work also illustrates the great potential to utilise molecular techniques for analysis of physiological processes of non-model organisms in a real-world setting.