Temporal escape-adaptation to eutrophication by Skeletonema marinoi

Area of Science:

• Marine Ecology
• Evolutionary Biology
• Oceanography

Background:

• Diatoms initiate spring blooms in temperate coastal waters.
• Nutrient enrichment can alter bloom timing and plankton succession.
• The marine diatom Skeletonema marinoi is a keystone species.

Purpose of the Study:

• To investigate if Skeletonema marinoi adapts to nutrient enrichment through thermal evolution.
• To determine if earlier peaking populations can maintain their position in spring plankton succession.
• To understand the role of eutrophication in driving thermal niche shifts.

Main Methods:

• Common-garden experiment comparing eight geographically separated Skeletonema marinoi subpopulations.
• Analysis of growth rates (doubling times) at different temperatures.
• Correlation of growth rates with the trophic state of the origin environment.
• Field observations of blooming temperatures in relation to trophic state.

Main Results:

• At early-spring temperatures, faster growth correlated negatively with environmental trophic state, indicating selection for rapid growth in eutrophic conditions.
• At mid-spring temperatures, this relationship reversed, suggesting selection for different traits.
• Field observations confirmed that blooming temperatures decreased with increasing trophic state.

Conclusions:

• Eutrophication drives natural selection towards genotypes that grow faster at colder, earlier spring temperatures.
• Skeletonema marinoi exhibits thermal niche shifts in response to environmental nutrient levels.
• These evolutionary adaptations can lead to significant trophic changes in local marine ecosystems.