Question

Define net primary production. Would you predict higher productivity in a farm pond or an alpine lake? Explain your answer.

Short answer

Net primary production (NPP) refers to the amount of organic matter produced by primary producers, such as plants and algae, that is available for consumption by other trophic levels after accounting for their energy needs in basic metabolic processes. Factors influencing NPP include light availability, nutrient availability, temperature, and ecosystem type. When comparing a farm pond and an alpine lake, higher net primary productivity is expected in a farm pond due to its increased nutrient availability and more favorable temperature conditions as compared to an alpine lake.

Step-by-step solution

Define Net Primary Production

Net primary production (NPP) represents the amount of organic matter produced by primary producers (such as plants and algae), available for consumption by other trophic levels, after accounting for the energy they consumed for their basic metabolic processes. It can be mathematically expressed as: \[NPP = GPP - R\] Where \(NPP\) is the net primary production, \(GPP\) is the gross primary production (total amount of energy produced via photosynthesis), and \(R\) is the energy consumption through respiration by the primary producers.

Identify Factors Influencing Primary Productivity

Primary productivity depends on several factors, including: - Light availability: Photosynthesis rate depends on the amount of light energy absorbed by primary producers, influencing NPP. - Nutrient availability: The presence of essential nutrients (e.g., nitrogen, phosphorus) influences the growth of primary producers and thus, the NPP. - Temperature: The optimal temperature range influences metabolic processes and photosynthesis in primary producers, impacting overall NPP. - Ecosystem type: Different ecosystems have varying levels of NPP depending on the combination of these factors.

Compare Farm Pond and Alpine Lake Productivity

Consider the factors mentioned in Step 2 and compare them for both farm ponds and alpine lakes: 1. Light availability: Farm ponds and alpine lakes generally have similar light exposure. However, alpine lakes, due to their higher altitude and snow cover in certain months, might have slightly lower light exposure compared to farm ponds. 2. Nutrient availability: Farm ponds tend to have higher nutrient availability due to agricultural runoff, the use of fertilizers, and the presence of different organisms providing nutrients. Alpine lakes, being more isolated systems, have lower nutrient availability, leading to lower primary productivity. 3. Temperature: The temperature in farm ponds, situated in more temperate/climate-controlled areas, tends to be more favored for primary productivity compared to alpine lakes, which experience colder conditions that slow down metabolic processes and limit productivity. Given these factors, we can predict that:

Conclusion

Overall, higher net primary productivity is expected in a farm pond compared to an alpine lake, mainly due to the increased nutrient availability and more favorable temperature conditions.