A. Lincoln MacKenzie

Algal blooms and climate anomalies in north‐east New Zealand, August ‐December 1992

Abstract A raphidophyte‐dominated phytoplankton bloom extended discontinuously along the northeastern coastline of New Zealand, from Bream Tail, north of Leigh, to the western coast of the Coromandel Peninsula from late August until December 1992. The bloom was associated with an “El‐Nino” phase of the Southern Oscillation, resulting in unusually cold sea temperatures. The dominant bloom species in the north was Fibrocapsa japonica and in the south Heterosigma akashiwo. Associated species included the coccolithophorid Gephyrocapsa oceanica and the naked form of the silicoflagellate Dictyocha speculum. By December, numbers of the armoured form of D. speculum had increased, as those of raphidophytes and coccolithophorids declined. Bioassays to test for shellfish biotoxins were negative and Artemia salina bioassays, indicators of ichthyotoxicity, were negative except for Heterosigma akashiwo cultures, isolated from Coromandel water samples.

Coccolithophores Gephyrocapsa oceanica and Emiliania huxleyi (Prymnesiophyceae = Haptophyceae) in New Zealand's coastal waters: Characteristics of blooms and growth in laboratory culture

Abstract Gephyrocapsa oceanica and Emiliania huxleyi were major components of extensive blooms in New Zealands coastal waters from September to February, 1992/93. Unusually cold sea surface temperatures at that time were related to the El‐Nino phase of the Southern Oscillation and consequent climatic patterns. G. oceanica co‐dominated with Fibrocapsa japonica (Raphido‐phyceae) along the north‐east coast (spring‐early summer) in a bloom which immediately preceded a toxic dinoflagellate event. E. huxleyi bloomed in the colder waters of Big Glory Bay, Stewart Island, where a significant water column temperature gradient and depleted nitrate and phosphate concentrations were recorded. An isolate of E. huxleyi from Big Glory Bay grew optimally at a salinity of 29 × 10−3, pH of 7.5–8.9, and temperature of 15–25°C. An isolate of G. oceanica from Leigh grew optimally at salinity 17–29 × 10−3, pH 8.4–8.9, and 20–25°C. G. oceanica grew with ammonium chloride, urea, or potassium nitrate as nitrogen source; E. huxle...

The risk to New Zealand shellfish aquaculture from paralytic shellfish poisoning (PSP) toxins

New Zealands reputation as a supplier of high quality food products is vital to the national economy; international consumers are acutely aware of food safety issues and markets are increasingly demanding higher standards. Filter feeding bivalves are particularly sensitive to the nature of the environment in which they are grown, and quality assurance is a major preoccupation of the shellfish aquaculture industry. With the exception of a couple of incidents, most notably the Gymnodinium catenatum blooms in 2000–2003, paralytic shellfish toxin (PST) contamination has, to date, not had an important effect on the economics and sustainability of the industry. However, the dinoflagellate species responsible for producing these toxins are not uncommon in New Zealand coastal phytoplankton communities, and it is important that awareness of the potential risk is maintained. This review summarises what we know about the causes and incidence of PST contamination from research and monitoring over the last 20 years, since it was first identified in New Zealand. It describes the dynamics of major events and their consequences, and evaluates what is likely to happen in the future as aquaculture expands into new areas with known histories of this problem.

Microbial activity in natural and organically enriched intertidal sediments near Nelson, New Zealand

Abstract Two measures of microbial activity were used to characterise a variety of sediment habitats in three intertidal inlets in the Nelson region, South Island, New Zealand. Rates of microbial mineralisation potential and epibenthic microalgal production were compared with sediment textures, concentrations of photosynthetic pigments, ATP concentrations, and organic and inorganic nutrients. Baseline ranges for these parameters were established for relatively undisturbed estuarine sites for assessing future environmental deterioration and for comparison with sites affected by organic enrichment. Sediment mineralisation rates were increased more than 1000‐fold by enrichment from a fruit processing plant and microalgal production was enhanced by more than 50‐fold at a site exposed to slaughterhouse wastes. The remaining variables, although often strongly correlated with activity measurements, were not as sensitive as measures of enrichment. Sediment microbial activity measurements are proposed as a means o...

Nutrients, and microplankton biomass off the New Zealand South Island north‐west coast, January 1982

Abstract A survey during the summer of 1982 revealed riverine outwelling and the upwelling of waters from aphotic depths at different locations on the Westland shelf. This led to nutrient enrichment of the euphotic zone and resulted in elevated phy to‐plankton and bacterioplankton biomass estimates. At most stations subsurface chlorophyll a maxima existed near the base of a nitrogen‐ depleted euphotic zone and near the boundary of the nitracline. Total N and total P concentrations in the euphotic zone (2.4–10.6 and 0.3–1.0 mmol m‐3, respectively) never exceeded the concentrations within the aphotic zone (9.0–16.1 and 0.7–1.3 mmol m‐3, respectively) at any station. Molar ratios revealed the larger proportions of the total nitrogen and phosphorus pools that existed in an organic form in the euphotic than in the aphotic zones. The relative depletion of dissolved inorganic nitrogen (DIN) compared to dissolved reactive phosphorus (DRP) as shown by DIN/DRP ratios in the euphotic zone (1.5–12.5) versus the aphot...