| Popis: |
Nodularin (NODLN) is a pentapeptide produced by the filamentous cyanobacterium Nodularia spumigena that is a bloom-forming species in the Baltic Sea. NODLN is an intracellular hepatotoxin, which can have a negative effect on aquatic life including fish. Toxins are released into the water when cells are lysing, e.g. during a decaying bloom. N. spumigena filaments have previously been shown to have a negative effect on perch egg development and perch larval survival. Coastal fish such as perch (Perca fluviatilis) have suffered from recruitment problems in the Baltic Sea the last decades. However, little is known about the impact of toxic cyanobacteria on juvenile perch. In the autumn of 2007, 1+ perch were exposed, during 29 days to either whole live cells (WC) or a crude extract (CE) of broken N. spumigena cells. Chlorophyll a concentrations in the aquaria were 50 µg L -1. Perch were fed chironomidae larvae twice a day. Unexposed perch either fed (CoF) or without food (Co) served as controls. Length and weight of perch were measured at onset and termination of experiment. NODLN content was measured in N. spumigena filaments, crude extract and perch liver samples using liquid chromatography-mass spectrometry (LC-MS). Total lipids (TL) were extracted and quantified from whole-body lyophilised perch excluding livers. No significant differences for length and weight of perch were found between treatments and fed control. NODLN was detected in the crude extract samples, while no NODLN was detected in the perch livers. Moreover TL determination revealed no significant differences between treatments and fed control. Nodularia spumigena did not affect perch in this experiment, probably due to that the critical period of the first year for the perch was exceeded. Therefore, 1+ perch was not as susceptible to the cyanobacterium as eggs, larvae and younger juveniles of fish found in the literature. Perch liver did not contain NODLN, thus either the toxin was detoxicated with no recorded energetic cost or it was not ingested. The variables studied here did not show any effects of NODLN. However, other chemical methods such as enzymatic activity may disclose effects of NODLN. |
