Food webs & energy transfer

Biomass

standing stock of tissue per unit area or volume (e.g., g C m⁻² or g C m⁻³).

Productivity

rate of biomass production, including time (e.g., g C m⁻² d⁻¹).

Production

the process of creating living tissue.

Trophic

referring to feeding or nutrition.

Food chain

linear depiction of energy flow.

Trophic levels

hierarchical positions in food chains (who eats whom).

Primary producers

autotrophs, mainly phytoplankton fixing CO₂ with sunlight.

Primary consumers

herbivores consuming phytoplankton.

zooplanktivores

feed on zooplankton - often secondary consumers.

piscivores

fish eaters.

Apex predators

sharks, killer whales, humans. Last level in food chain.

-vores

referring to what the organism consumes.

Energy transfer

not 100% efficient.

Losses

include sloppy feeding, defecation, respiration, and indigestible material.

Microbial loop

recycles organic carbon (DOC, POC) back into food web.

Standing stock

biomass reservoir in steady state (production ≈ predation + other losses).

Food chain efficiency

averages ~10% per trophic level.

Upwelling systems

very efficient, few trophic levels (Diatom base).

Oligotrophic gyres

inefficient, many trophic levels (Cyanobacteria base).

Food chains vs. Food webs

Food chains = simplified, linear. Food webs = complex networks with multiple interactions and competition.

Bottom-up controls

nutrient/light availability controls primary producers.

Top-down controls

consumer grazing controls lower trophic levels.