The harvesting step collects both the algal turf and the pollutants, {HEAD ~ nutrients} or other undesirable species precipitated thereon, thus removing the species from {TAIL ~ the water} 
The harvesting step collects both the algal turf and the pollutants , { HEAD ~ nutrients } or other undesirable species precipitated thereon , thus removing the species from { TAIL ~ the water }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL