Changes in concentrations of microcystins in rainbow trout, freshwater mussels, and cyanobacteria in Lakes Rotoiti and Rotoehu

Abstract

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.

Widespread Distribution and Identification of Eight Novel Microcystins in Antarctic Cyanobacterial Mats

“…The reconstituted extracts for samples collected in 2006 and selected samples from Bratina Island were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS-MS) for 13 MC variants and nodularin (51). MCs were separated by LC (Alliance 2695; Waters Corp., MA) using a 5-m Luna C 18 column (150 by 2 mm) (Phenomenex, CA) with a water-methanol-acetonitrile gradient containing 0.15% formic acid (0.2 ml min Ϫ1 ; 10-l injection).…”

Detection, identification and toxigenicity of cyanobacteria in New Zealand lakes using PCR-based methods

“…It is categorised as eutrophic with decreasing water quality. Health warnings are commonly issued in summer because of high concentrations of potentially toxic cyanobacteria (Wood et al 2006a). Surface water samples were collected weekly between 19 February 2007 and 27 March 2007 from one sampling site at each lake: Okawa Bay (Lake Rotoiti), Ohau Channel (Lake Rotorua) and Otautu Bay (Lake Rotoehu).…”

“…to blooms mainly containing toxic Microcystis spp. in the course of just 2 weeks (Wood et al 2006a). …”

“…and Microcystis spp. accounted for 90% of the cyanobacterial cell abundance in Lakes Rotoiti and Rotoehu (Wood et al 2006a). In 2007, blooms in Lake Rotoiti were composed primarily of Microcystis spp.…”

Costs of harmful blooms of freshwater cyanobacteria

“…CyanoHABs can have severe direct impacts on freshwater fisheries as a result of fish kills (Barica, 1978), as well as indirect effects relating to accumulation of cyanotoxins (microcystins) in fish (Wood et al, 2006) or shellfish tissue (Falconer, Choice, and Hosja, 1992). Pretty et al (2003) estimated a loss of £29-118,000 per annum for commercial fisheries in the United Kingdom based on damages incurred from cyanoHABs.…”