Correct option is B
In temperate and subpolar regions, productivity tends to be highest in spring, not least, because the transition from light-limiting to nutrient-limiting conditions occurs. During the spring bloom, there is usually an abundance of sunlight after winter, and nutrients are available in the surface waters. This allows for the rapid growth of phytoplankton, which leads to higher productivity. Therefore, option (2) is incorrect as it implies the opposite trend.
Information Booster:
- Spring productivity in temperate and subpolar regions is usually high because of the favorable combination of light and nutrients, stimulating phytoplankton growth.
- Phytoplankton blooms during the spring in these regions are a common phenomenon due to the increased availability of sunlight after the darker winter months.
- Light-limiting conditions typically occur in winter, while nutrient-limiting conditions appear in late spring or early summer, but spring itself sees an increase in productivity.
- Nutrient availability in these regions is influenced by mixing of water layers, but during spring, the newly available light accelerates productivity.
- The statement in option (2) is contradictory to the usual ecological patterns observed in temperate and subpolar ecosystems.
- The spring phytoplankton bloom is one of the most productive times of the year in many temperate and subpolar marine environments.
Additional Information:
- Option (1) is accurate because upwelling in equatorial regions does lead to higher productivity by bringing nutrient-rich waters into the euphotic zone.
- Option (3) is correct because cyanobacteria are indeed more numerically dominant in tropical and subtropical oceans due to their ability to fix nitrogen and take up nutrients at low concentrations.
- Option (4) is also correct, as larger phytoplankton like diatoms can dominate polar nutrient-rich waters, and these are grazed by multicellular zooplankton like krill, especially during certain seasons.
