Algal Turf Scrubber —
A Biomimicry
Yearly range of gross primary productivity (GPP) at four back reef-flat sites on St. Croix. GPP is shown for each season as a function of the standing algal crop of mostly algal turfs. Combined with similar data from several other reefs across the Caribbean it has been possible to demonstrate that the very high levels of primary productivity are light, and not nutrient-limited.
TOP IMAGE: Typical mature algal complex from a three-acre water cleaning system in Florida.
Throughout much of the 1970s, Dr. Adey, alongside numerous postdoctoral researchers, investigated the metabolism of Caribbean coral reefs. Despite extremely low nutrient levels, these well-developed reefs exhibited high rates of photosynthesis and primary productivity, fueled by strong wave action and abundant sunlight.
Uncovering the Metabolic Strength of Caribbean Coral Reefs
Constant trade winds and moderate wave action drives open ocean water across these coral reefs. By measuring oxygen concentration, both day and night, in the water overflowing the reefs, along with current flow rates, it is possible to determine community respiration and photosynthesis. This work was carried out at several reef sites for over a year.
Laboratory test chamber built by my post docs Bob Carpenter and John Hackney. Similar to, most such chambers or microcosms, this chamber includes the standard magnetic stirring bar (right side of chamber). However, uniquely, this chamber included a device to provide oscillatory motion to the algal turf screen, which was cut from a larger screen in an exhibit coral reef algal turf scrubber (center and left in chamber). This device provided another demonstration of the role of wave surge in driving primary productivity.
Floating screens placed from the surface to 10m depth in a wide variety of eastern Caribbean reef environments were harvested weekly, by hand scraping to demonstrate algal production levels. At 10–20 g (dry wgt)/m²/day, production was roughly one-third of the algal turf productivity inferred from the oxygen analyses; the heterogenous reef surface provided 2–3 m² of surface/per horizontal m², thus providing the production rates inferred by oxygen analysis.
Transfer (biomimicry) of the algal turf scrubbing process (i.e. a removal of nutrients from surrounding water) to a “real world” need to remove nutrients from polluted waters. This Algal Turf Scrubber (ATS), built by the engineering firm HydroMentia is on Taylor Creek, a tributary of Lake Okeechobee, running through cattle farm country.
2D versus 3D. The character of the AST screen substate is critical to optimizing algal turf productivity. In a three-year long study on the Wicomico River in Virginia, we demonstrated a 3X greater algal function with a 3-dimentioanl screen.