How does diel vertical migration by zooplankton and fish influence vertical nutrient transport and oxygen distribution in stratified lakes?

How does diel vertical migration by zooplankton and fish influence vertical nutrient transport and oxygen distribution in stratified lakes?

• A. Diel vertical migration reduces nutrient transport to deeper layers
• B. Diel vertical migration transports nutrients between layers via surface feeding and deep respiration, affecting oxygen distribution
• C. Diel vertical migration only affects temperature, not chemistry
• D. Diel vertical migration has no impact on stratified lakes

Answer: (B)

Diel vertical migration acts as a daily vertical conveyor for nutrients and organic matter between the upper and deeper waters of a stratified lake. Zooplankton and small fish surface to feed at night, gaining nutrients from the epilimnion, then migrate to deeper waters during the day to avoid predators. In the depth, their metabolism and excretion release nutrients directly into the hypolimnion, and their sinking fecal pellets deliver surface-derived organic matter that is remineralized down there. This two-way movement transports nutrients from the surface layer to deeper waters and also uses up oxygen where respiration occurs, altering the vertical oxygen profile. In stratified lakes, where mixing is limited, this downward flux can reduce oxygen concentrations in the depths while redistributing nutrients, which is why the correct choice emphasizes nutrient transfer between layers via surface feeding and deep respiration and its effect on oxygen distribution.

Diel vertical migration acts as a daily vertical conveyor for nutrients and organic matter between the upper and deeper waters of a stratified lake. Zooplankton and small fish surface to feed at night, gaining nutrients from the epilimnion, then migrate to deeper waters during the day to avoid predators. In the depth, their metabolism and excretion release nutrients directly into the hypolimnion, and their sinking fecal pellets deliver surface-derived organic matter that is remineralized down there. This two-way movement transports nutrients from the surface layer to deeper waters and also uses up oxygen where respiration occurs, altering the vertical oxygen profile. In stratified lakes, where mixing is limited, this downward flux can reduce oxygen concentrations in the depths while redistributing nutrients, which is why the correct choice emphasizes nutrient transfer between layers via surface feeding and deep respiration and its effect on oxygen distribution.