The risk of harmful algal blooms (HABs) in the oyster-growing estuaries of New South Wales, Australia

Abstract

The spatial and temporal variability of potentially harmful phytoplankton was examined in the oyster-growing estuaries of New South Wales. Forty-five taxa from 31 estuaries were identified from 2005 to 2009. Harmful species richness was latitudinally graded for rivers, with increasing number of taxa southward. There were significant differences (within an estuary) in harmful species abundance and richness for 11 of 21 estuaries tested. Where differences were observed, these were predominately due to species belonging to the Pseudo-nitzschia delicatissima group, Dinophysis acuminata, Dictyocha octonaria and Prorocentrum cordatum with a consistent upstream versus downstream pattern emerging. Temporal (seasonal or interannual) patterns in harmful phytoplankton within and among estuaries were highly variable. Examination of harmful phytoplankton in relation to recognised estuary disturbance measures revealed species abundance correlated to estuary modification levels and flushing time, with modified, slow flushing estuaries having higher abundance. Harmful species richness correlated with bioregion, estuary modification levels and estuary class, with southern, unmodified lakes demonstrating greater species density. Predicting how these risk taxa and risk zones may change with further estuary disturbance and projected climate warming will require more focused, smaller scale studies aimed at a deeper understanding of species-specific ecology and bloom mechanisms. Coupled with this consideration, there is an imperative for further taxonomic, ecological and toxicological investigations into poorly understood taxa (e.g. Pseudo-nitzschia).

Monitoring of freshwater toxins in European environmental waters by using novel multi‐detection methods

“…No toxins were detected in samples F1 through F6 from France, which encompass 6 mo of municipal tap water samples collected from January to November 2013. In the case of DA, although some species producing this toxin have been described in brackish waters (and are usually identified in estuaries and bay waters, where the salinity is not as high as in marine environments), to our knowledge the toxin has never been reported in fresh waters [27,51,52]. No traces of CYN or DA were detected in any of the samples.…”

Recent Trends in Marine Phycotoxins from Australian Coastal Waters

“…Alexandrium minutum , A. pacificum , A. ostenfeldi and A. australiense are known to be distributed along the east coast of mainland Australia from northern NSW to Victoria [12,13,14,16,17], whilst A. fundyense has only been identified in Tasmania thus far [14]. The seasonal occurrence for A. pacificum is most commonly in spring/summer, A. fundyense in winter/spring and A. minutum in early summer/autumn.…”

“…In New South Wales, Gymnodinium catenatum has also been found sporadically at several estuarine sites: Manning River, Brisbane Water, Hawkesbury, Jervis Bay, Tuross Lake, Nelson Lagoon and Merimbula Lake [16]. Generally, it has been present in low abundances, although it did exceed the health department’s action limits four times between 2005 and 2009 in New South Wales [16]. …”

“…These toxins enter the food chain through herbivorous fish that graze micro-algae and are then bio-accumulated and bio-transformed to more toxic forms as they move up the food chain. Gambierdiscus are epiphytic dinoflagellates, well known in tropical reef areas, and although their increasing presence in temperate Australia has now been documented [16,74], a species that consistently produces CTXs has yet to be identified from Australian waters [74,75,76]. …”

“…Moreover, elevated cell concentrations of Pseudo-nitzschia are commonly reported in the southeastern Australian oyster-growing estuaries [16]. In 2010, Pseudo-nitzschia cuspidata was responsible for the largest and longest toxic Pseudo-nitzschia blooms to date, closing the Sydney rock oyster ( Saccostrea glomerata ) harvest areas for 16 weeks (max.…”