Eutrophication, P Loading, and Trophic States

Slide Deck 1

effects of cultural eutrophication

• algal blooms

• hypoxia

• taste and odor problems

• loss of economic vitality

• changes in community structure

• loss fish production

• loss of biodiversity

• facilitation of invasive species

what happens when P is added to a P-limited lake as a one-time pulse

• short-lived productivity boom

• productivity increases right when total P starts to decrease

  

vollenweider’s P loading model equation

[P]λ = [P]i / (1 + √Tw)

total P concentration in the lake predicted as a function of inflow total P concentration and water resistance time

key idea of vollenweider’s

predicts lake phosphorus concentration based on external P loading and lake physical characteristics

residence time

long residence time - phosphorus accumulates - higher eutrophication risk

(more vulnerable to nutrient enrichment)

short residence time - nutrient flushed quickly - lower accumulation

when vollenweider’s model is valid

• phosphorus is the primary limiting nutrient

• the lake is well-mixed

• the system is near steady state

• external P loading dominates over internal loading

benefits to vollenweider’s

• predictive

• links watershed inputs to lake response

• useful for management decisions

• helps set nutrient loading targets

key idea of carlson’s trophic state index (TSI)

an empirical classification tool that assigns a numeric value to lake trophic states using

• secchi depth

• chlorophyll-a

• total phosphorus

how carlson’s TSI

• compares trophic state among lakes

• tracks changes in lake over time

• communicates lake conditions to managers and the public

benefits of carlson’s TSI

• requires minimal data

• ideal for monitoring and comparison

• simple

differences between carlson’s TSI and vollenweider model

carlson’s TSI: describes current condition

vollenweider model: predicts response to P-loading