Final answer:
Three high-risk/high-impact activities in aquatic environments involve the introduction of invasive species, nutrient loading from runoff, and overfishing. These activities can lead to dramatic shifts in ecosystems and biodiversity loss, particularly in freshwater biomes altered by human activity. Addressing these impacts requires concerted efforts in public education, policy, and sustainable practices.
Step-by-step explanation:
Regarding aquatic environments, particularly those altered by human activities, three high-risk/high-impact activities include the introduction of invasive species, excessive nutrient loading from agricultural runoff, and overfishing or unsustainable fishing practices.
Invasive species can outcompete native fauna and significantly alter ecological balances as indicated in the case with the potential impact of the C. gigas invasion on Scandinavian aquatic habitats. Agricultural runoff can lead to eutrophication and dead zones in freshwater and marine ecosystems, severely affecting biodiversity.
Overfishing can deplete fish stocks and disrupt the food web, leading to the decline of other species, as is the case with some fish populations in highly fished areas.
Efforts like public education on invasive species, reduction of aquatic introductions from ballast water discharges, and more responsible aquaculture practices are vital to reducing these impacts. Moreover, high-risk aquatic biomes, such as freshwater biomes, are especially vulnerable to these high-impact activities which can lead to loss of species and alteration of community structures.