Oysters are suspension feeders: each animal pumps water across its gills and strains out phytoplankton and fine sediment, then binds the unusable fraction into mucus-bound "pseudofeces" that settle onto the reef as biodeposits. A single adult oyster can filter several litres of water per hour, and a dense reef processes the entire water column above it many times a day.
Per-oyster clearance rate follows a thermal-performance curve peaking near 22 °C and dropping off at both cold and hot extremes (feeding shuts down below ~5 °C and above ~35 °C):
CR(T) = CR_max · exp( -(T - T_opt)² / (2σ²) )
F = N · CR(T) [population filtration, L/hr]
dC/dt = k_flush·(C_in - C) - (F / V)·C [water-column turbidity]
C is the turbidity of the reef's local water volume V, C_in is the sediment/algae concentration flowing in from the wider estuary, and k_flush is how fast the current exchanges that volume — a sluggish current lets the reef pull turbidity down further; a fast one keeps re-supplying it. Biodeposition (and so reef accretion) scales with the filtration rate F, which is why healthy oyster reefs measurably grow upward over years even as they clean the water above them.
- Oyster density — population per m² of reef; more animals means more total pumping capacity (and more biodeposit accretion) but also more competition for the same water.
- Water temperature — moves you along the thermal-performance curve; feeding all but stops far from ~22 °C.
- Current / flushing speed — how quickly outside water (at the loading concentration) replaces water the reef has already cleared.
- Sediment / algae loading — how turbid the incoming estuarine water is; the reef can only pull local clarity below this baseline, never below zero.
Real-world relevance: this is the same mechanism restoration projects rely on when they rebuild oyster reefs to improve estuary water quality — the Chesapeake Bay's historic oyster population is estimated to once have filtered the entire bay's water volume in a matter of days.