What does bioaccumulation refer to in aquatic ecology?

Bioaccumulation refers specifically to the build-up of toxins, such as heavy metals or persistent organic pollutants, within the tissues of an organism over time. This process occurs when an organism absorbs these harmful substances faster than it can eliminate them, leading to increasingly higher concentrations of toxins within its body. In aquatic environments, certain organisms, particularly those at higher trophic levels, can accumulate significant amounts of these substances due to the consumption of contaminated prey. This phenomenon is critical as it poses health risks not only to the organisms themselves but also to predators, including humans, who consume them, highlighting the importance of monitoring pollutants in aquatic ecosystems.

The other options do not accurately describe bioaccumulation. The loss of biodiversity in populations pertains to species extinction or reduction due to various factors, while an increase in water temperature relates to climate change impacts on aquatic habitats. Additionally, nutrient cycling involves the movement and exchange of organic and inorganic matter within ecosystems, which is separate from the concept of bioaccumulation. Thus, the correct answer underscores the issue of toxin build-up in aquatic organisms.