How Freshwater Fish Build Up Metals and Recover After Floods

Jim Crocker
4th March, 2024

How Freshwater Fish Build Up Metals and Recover After Floods

Image Source: Natural Science News, 2024

Key Findings

  • Alpine bullheads in lakes have more mercury and zinc than those in streams
  • A 2018 flood caused a quick, significant increase in mercury in stream bullheads
  • Zinc levels in stream bullheads dropped by 70% in under five years
Mercury and other heavy metals in our environment pose a significant threat to both aquatic life and human health. While some metals are naturally occurring, human activities have accelerated their release into ecosystems, where they can accumulate in fish, potentially leading to serious health consequences for those who consume them. Understanding how these metals distribute and transfer within aquatic ecosystems is crucial for managing their impact. Recent research by scientists at the University of Žilina has shed light on this issue by examining how metals move from alpine terrestrial systems into fish populations in both lakes and streams[1]. The study focused on the Cottus poecilopus, commonly known as the alpine bullhead, a fish species found in the West Carpathian mountain range. Researchers collected 66 wild fish from different alpine lakes and the Javorinka stream to measure the concentrations of mercury, zinc, molybdenum, rubidium, and strontium. The findings were revealing: bullheads in alpine lakes had higher levels of metals compared to those living in mountain streams, with mercury and zinc concentrations being particularly elevated in lake-dwelling fish. A key insight from this research is the impact of environmental disturbances on metal accumulation. A major flood in July 2018 in the Javorinka area caused a significant spike in mercury content within the bullhead population. This spike was not a slow build-up; the bioaccumulation occurred rapidly after the flood and remained high in the subsequent year. However, by 2021-2022, mercury levels in these fish had decreased by up to 70%. The study also observed fluctuations in other metals. Molybdenum and rubidium levels in stream bullheads dropped sharply after the flood but returned to pre-flood levels within two years. Strontium concentrations, on the other hand, showed more complex patterns of change over the four years following the flood, suggesting that multiple factors influence its accumulation in fish. A particularly concerning discovery was the significant decline in biogenic zinc. Over less than five years, the average zinc concentration in the alpine bullhead population of the stream fell by 70% and continued to decrease. This decline could have implications for the health of the fish population, as zinc is essential for various biological functions. The findings of this study are consistent with earlier research that young bullheads can serve as excellent indicators of water quality in mountain streams[2]. The study also complements a broader understanding of how reductions in mercury pollution can lead to immediate benefits for fish populations and, by extension, human consumers[3]. Moreover, it aligns with previous observations that larger and older fish tend to accumulate more mercury[4]. What makes this recent study particularly valuable is its demonstration of how a single environmental event, such as a flood, can have immediate and measurable effects on the metal concentrations in fish populations. This emphasizes the need for ongoing monitoring of aquatic ecosystems, especially in the wake of environmental disturbances. In conclusion, the research from the University of Žilina has provided new insights into the dynamics of metal bioaccumulation in alpine aquatic environments. By illustrating the rapid changes in metal concentrations following environmental events, it underscores the importance of protecting these ecosystems and highlights the potential for recovery when pollutant levels are reduced. This study not only advances our scientific understanding but also supports the development of more effective environmental management and pollution mitigation strategies.

EnvironmentEcologyMarine Biology


Main Study

1) Differential accumulation of metals in the lacustrine and fluvial Alpine bullheads (Cottus poecilopus) and recovery of fish from metal contamination after a flash flood.

Published 10th February, 2024

Related Studies

2) Different accumulation of some elements in the fry and adults of alpine bullheads (Cottus poecilopus).

3) Experimental evidence for recovery of mercury-contaminated fish populations.

4) Mercury concentration in the sentinel fish species Orthopristis ruber: Effects of environmental and biological factors and human risk assessment.

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