3.01 marine flash cards pg 1

Ecological Succession: Core Ideas

• Ecosystems are dynamic; they change due to climate shifts, invasive species, natural disasters, seasonal cycles, and time.

• The gradual sequence of community changes over time is called ecological succession.

  • Comparable to royal succession: when one community “dies,” another “inherits” the habitat.

  • Time scale ranges from a few \text{decades} to \text{millions of years}.

Primary Succession

• Begins on newly formed, lifeless surfaces.

  • Examples: volcanic lava flows, land exposed by retreating glaciers.

• No pre-existing soil; surface is bare rock or ash.

• Pioneer species (algae, fungi, lichens) are first colonizers; they break down rock and start soil formation.

• Few organisms initially ⇒ biodiversity rises gradually as soil develops and plants, then animals, establish.

Secondary Succession

• Rebuilding of a previously existing ecosystem after a major disturbance (fire, flood, storm, human clearing).

• Soil already present; seed bank and microorganisms often survive.

• Pioneer species + early plants (grasses, herbs) arrive quickly, followed by shrubs, trees, and animals.

• Starts with low biodiversity, which increases over time as community complexity returns.

Case Study: Surtsey Island (Iceland)

• Undersea volcanic eruption 1963–1967 created a brand-new island ⇒ classic primary succession site.

• First plant colonization recorded 1965 via ocean-borne seeds.

  • Early pioneers: sea rocket, sea sandwort, sea lyme grass.

• Ongoing observations show gradual soil development and rising biodiversity.

Key Takeaways

• Primary vs. Secondary: presence of soil is the main difference; primary starts from bare rock, secondary from existing soil.

• Pioneer species kick-start both processes but face harsher conditions in primary succession.

• Biodiversity trajectory: both forms move from low to higher diversity, but secondary succession is usually faster due to existing soil and seed banks.