Text-figs. 1-7)Twenty-one species of female decapod Crustacea with gravid ovaries were collected from the field and spawned naturally in the laboratory. Newly spawned eggs and incubating females were kept at temperatures between 3 °C and 24 C C constant at 3 C C increments until the eggs hatched after completing their embryonic development.Observations on developing eggs confirmed that in decapods which hatch at a zoea stage, the pre-zoeal cuticle is associated with the metanauplius stage relegated to embryonic life, rather than to the preceding nauplius. During embryonic development, the rate of egg volume increase (elsewhere attributed to osmotic uptake of water) is considered slower in the eggs of species with a long development period than in those which develop rapidly. In all species here studied the rate of increase of egg volume accelerated during development, especially in the latter stages. The rate of yolk metabolism varies from species to species according to the time taken for egg development, but in all species it was slower during early development than during the last few days before hatching. In very early development (around gastrulation), the eggs of four unrelated species were found to possess a form of diapause which could not be shortened significantly by raising the water temperature. It is suggested that diapause has evolved in certain species as a response to the availability of food in the plankton and to enhance larval survival.The development times from spawning to hatching of eggs (D), are described as functions of temperature (T) by Belehradek's temperature equation D= a (T-

Wellington Harbour is a large (~85 km 2 ), semi-enclosed temperate ecosystem. We used unpublished baseline data from 6 subtidal and 1 intertidal harbour stations to quantify the ecological effects of the naturally occurring toxic bloom of the naked dinoflagellate Karenia brevisulcata (Chang) G.Hansen & Moestrup during February and March 1998. Species richness decreased at 6 stations and increased at 1 station, numbers of individuals decreased at 4 of 4 stations, species diversity decreased at 5 of 5 stations, evenness decreased at 2 and increased at 2 stations, and biomass decreased at 2 of 3 stations. These data indicate that the K. brevisulcata bloom of late summer 1998 resulted in a mass die-off of the subtidal benthic invertebrates over a large area of Wellington Harbour, as well as of the flora and fauna at 1 intertidal location studied. Four major phyla (echinoderms, molluscs, polychaetes and crustaceans) were equally affected by the bloom, although different species within each phylum were differentially affected (regardless of phylum, small and shallowburrowing individuals were most affected). Multivariate statistical analyses of these data identified 3 clusters composed of 4 subtidal stations which showed the highest level of impact by the bloom and were based on a spatial/environmental component (location in the northern harbour; greater depth; low current/wave energy) as well as a temporal component (pre-vs post-bloom). The remaining 3 subtidal stations were less affected by the bloom and each formed a separate cluster according to spatial/environmental rather than temporal effects. This event has permitted us to quantify, for the first time, the effects of a natural toxic bloom on a large-scale temperate harbour ecosystem and to relate the magnitude of these effects to the geographic and environmental properties of different locations within that ecosystem. bloom, large quantities of dead and dying shellfish, in particular the greenshell mussel Perna canaliculus and the venerid clam Paphies australis were washed up on Petone and eastern harbour beaches (see Fig. 1). This toxin (which is presently uncharacterised) also had a direct effect on microalgal growth in the water column (Chang 1998), and during SCUBA observations of the substrate at 5 to 10 m depth we noted that the sediments were coated with a khaki-coloured film and that there was no evidence of recent bioturbation. This was the first time that an algal bloom in Wellington Harbour had been linked to mass destruction of the marine fauna, and is the first quantitative record of the direct effect of a natural toxic algal bloom upon the benthic invertebrates of a large (~85 km 2 ) temperate marine ecosystem.The sequence of events leading up to the bloom and during its period of influence was documented by Chang (1998). The Wellington Harbour bloom followed earlier reports of mortalities among fish and other marine fauna along the southern North Island east coast during January and February 1998, and has been attributed to the effects ...

Contamination of drinking and recreational water bodies by toxic cyanobacteria is a significant water management issue in many countries. Until recently, knowledge of the occurrence of cyanotoxins and species responsible for cyanotoxin production in New Zealand was limited. In this study

Microcystin concentrations in cyanobacteria and their accumulation in rainbow trout (Oncorhynchus mykiss) and freshwater mussels (Hyridella menziesi) in Lakes Rotoiti and Rotoehu (New Zealand) were investigated. Hatchery rainbow trout were added to an enclosure in Lake Rotoiti where concentrations of microcystins in the phytoplankton and cyanobacterial cell concentrations could be closely monitored. Rainbow trout that were free to roam in the entire area of each lake were also included in the study. Freshwater mussels were suspended subsurface in cages in the enclosure. Phytoplankton samples, rainbow trout liver and muscle tissue, and the tissues of mussels were analyzed for microcystins using the ADDA-ELISA method, and selected samples were analyzed using LC-MS. A maximum concentration of microcystins in the phytoplankton samples of 760 microg L(-1) was recorded in Te Weta Bay, Lake Rotoiti, in March 2004. ELISA results confirmed microcystin immunoreactivity in rainbow trout liver and muscle tissues and in freshwater mussels. The microcystin congeners LR, YR, RR, AR, FR, LA, and WR were detected by LC-MS in caged freshwater mussels in Lake Rotoiti but were not detected in either muscle or liver tissue of rainbow trout. The daily tolerable intake limit of microcystins for human consumption recommended by the World Health Organisation is 0.04 microg kg(-1) day(-1). Modeling was carried out for the human intake of microcystin compounds from rainbow trout muscle tissue, and the potential health risks were estimated, assuming the ADDA-ELISA was determining compounds of toxicity equivalent to microcystin-LR.

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