Although it is widely assumed that temperature affects pollutant toxicity,
few studies have actually investigated this relationship. Moreover, such research
as has been done has involved constant temperatures; circumstances which
are rarely, if ever, actually experienced by north temperate, littoral zone cyprinid
species. To investigate the effects of temperature regime on nickel toxicity in
goldfish (Carassius auratus L.), 96- and 240-h LCSO values for the heavy metal
pollutant, nickel (NiCI2.6H20), were initially determined at 2DoC (22.8 mg/L and
14.7 mg/L in artificially softened water). Constant temperature bioassays at
10°C, 20°C and 30°C were conducted at each of 0, 240-h and 96-h LCSO
nickel concentrations for 240 hours.
In order to determine the effects of temperature variation during nickel
exposure it was imperative that the effects of a single temperature change be
investigated before addressing more complex regimes. Single temperature
changes of + 10°C or -10°C were imposed at rates of 2°C/h following
exposures of between 24 hand 216 h. The effects of a single temperature
change on mortality, and duration of toxicant exposure at high and low
temperatures were evaluated.
The effects of fluctuating temperatures during exposure were investigated
through two regimes. The first set of bioassays imposed a sinewave diurnal
cycle temperature (20.±.1DOC) throughout the 10 day exposure to 240-h LeSO
Ni. The second set of investigations approximated cyprinid movement through
the littoral zone by imposing directionally random temperature changes (±2°C
at 2-h intervals), between extremes of 10° and 30°C, at 240-h LC50 Ni. Body
size (i.e., total length, fork length, and weight) and exposure time were recorded
for all fish mortalities.
Cumulative mortality curves under constant temperature regimes
indicated significantly higher mortality as temperature and nickel concentration
were increased. At 1DOC no significant differences in mortality curves were
evident in relation to low and high nickel test concentrations (Le., 16 mg/L and
20 mg/L). However at 20°C and 30°C significantly higher mortality was
experienced in animals exposed to 20 mg/L Ni. Mortality at constant 10°C was
significantly lower than at 30°C with 16 mg/L and was significantly loWer than
each of 2DoC and 39°C tanks at 20 mg/L Ni exposure.
A single temperature shift from 20°C to 1DoC resulted in a significant
decrease in mortality rate and conversely, a single temperature shift from 20°C
to 30°C resulted in a significant increase in mortality rate. Rates of mortality
recorded during these single temperature shift assays were significantly different
from mortality rates obtained under constant temperature assay conditions.
Increased Ni exposure duration at higher temperatures resulted in highest
Diurnally cycling temperature bioassays produced cumulative mortality
curves approximating constant 20°C curves, with increased mortality evident
after peaks in the temperature cycle. Randomly fluctuating temperature regime
mortality curves also resembled constant 20°C tanks with mortalities after high
temperature exposures (25°C - 30°C).
Some test animals survived in all assays with the exception of the 30°C
assays, with highest survival associated with low temperature and low Ni
concentration. Post-exposure mortality occurred most frequently in individuals
which had experienced high Ni concentrations and high temperatures during
assays. Additional temperature stress imposed 2 - 12 weeks post exposure
resulted in a single death out of 116 individuals suggesting that survivors are
capable of surviving subsequent temperature stresses.
These investigations suggest that temperature significantly and markedly
affects acute nickel toxicity under both constant and fluctuating temperature
regimes and plays a role in post exposure mortality and subsequent stress
The export option will allow you to export the current search results of the entered query to a file. Different
formats are available for download. To export the items, click on the button corresponding with the preferred download format.
By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.
To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export.
The amount of items that can be exported at once is similarly restricted as the full export.
After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.