Interactive effects of temperature and food ration on growth and mercury concentration in eastern brook trout

Warming temperatures predicted under global climate change will alter the
dynamics of secondary production and trace element accumulation and may
interact with environmental factors such as food resource availability to
influence growth and bioaccumulation. We conducted laboratory experiments
to assess the role of temperature and food ration on Brook Trout growth
and mercury (Hg) concentration. Across a range of temperatures (16 –
24°C), Brook Trout growth rate decreased, and Hg concentration increased
with temperature. We observed the lowest Hg concentrations in fish under
the low temperature (15°C), high ration treatment, and the highest
concentrations in the high temperature (22°C), zero ration treatment. The
relative growth rank of individual fish was a significant predictor of Hg
concentration, with fast-growing individuals having lower Hg. Based on
structural equation modelling (SEM), the strongest relationship between
Brook Trout Hg and the temperature/ration treatments was through an
indirect pathway mediated by Brook Trout growth rate. Our results provide
support for a link between warming temperatures, growth, and
bioaccumulation rates in upland stream food webs, with implications for
wildlife and human health.