Producers of Lake Ontario: The Base of a Great Lake Food Web

In Lake Ontario, primary producers—organisms that fix inorganic carbon via photosynthesis—form the foundation of the entire ecosystem. They fall into three guilds:

🌊 Pelagic Phytoplankton (Open Water)

• Diatoms (Asterionella, Fragilaria, Stephanodiscus) – Silica frustules; bloom spring/fall.
• Chrysophytes (Dinobryon, Mallomonas) – Golden algae; flagellated.
• Cyanobacteria (Microcystis, Anabaena) – Summer blooms; some toxic.
• Chlorophytes (Scenedesmus, Chlamydomonas) – Green algae.
• Cryptophytes (Cryptomonas) – High nutritional value for grazers.

Productivity: ~150–300 g C/m²/yr (mesotrophic). Spring diatom bloom = 50% annual production.

🪨 Benthic Periphyton (Attached)

• Epilithic (on rocks), epiphytic (on plants), epipsammic (on sand), epipelic (on mud).
• Dominated by diatoms, cyanobacteria, chlorophytes.
• Critical in nearshore (<30m) where light reaches bottom. Supports grazers (snails, insects).

🌿 Macrophytes (Vascular Plants)

• Submerged: Vallisneria, Potamogeton, Elodea, Chara (charophyte algae).
• Emergent: Typha, Scirpus, Phragmites (marshes).
• Floating-leaf: Nymphaea, Nuphar.
• Concentrated in bays, wetlands, river mouths (e.g., Bay of Quinte, Hamilton Harbour).

🔬 Why It Matters

Producers → zooplankton (Daphnia, calanoids) → forage fish (alewife, rainbow smelt) → predators (lake trout, salmon, bass) → birds/mammals. Dreissenid mussels (zebra/quagga) have diverted production to benthos since 1990s—changing everything.