Algal turf scrubber (ATS) floways on the Great Wicomico River, Chesapeake Bay: productivity, algal community structure, substrate and chemistry(1).

productivity of flat ATS screens was 15.4 gm � 2 � d � 1 . This was elevated to 39.6 gm � 2 � d � 1 with a three- dimensional (3-D) screen, and to 47.7 gm � 2 � d � 1 by avoiding high summer harvest temperatures. These methods enhanced nutrient removal (N, P) in algal biomass by 3.5 times. Eighty-six algal taxa (Ochrophyta (diatoms), Chlorophyta (green algae), and Cyan- obacteria (blue-green algae)) self-seeded from the GWR and demonstrated yearly cycling. Silica (SiO2) content of the algal biomass ranged from 30% to 50% of total biomass; phosphorus, nitrogen, and carbon content of the total algal biomass ranged from 0.15% to 0.21%, 2.13% to 2.89%, and 20.0% to 25.7%, respectively. Carbohydrate content (at 10%-25% of AFDM) was dominated by glucose. Lipids (fatty acid methyl ester; FAMEs) ranged widely from 0.5% to 9% AFDM, with Omega-3 fatty acids a consistent component. Mathematical modeling of algal produ- ctivity as a function of temperature, light, and substrate showed a proportionality of 4:3:3, resp- ectively. Under landscape ATS operation, substrate manipulation provides a considerable opportunity to increase ATS productivity, water quality amelioration, and biomass coproduction for fertilizers, fermentation energy, and omega-3 products. Based on the 3-D prod- uctivity and algal chemical composition demonstrated, ATS systems used for nonpoint source water treat- ment can produce ethanol (butanol) at 5.83 per unit area of corn, and biodiesel at 12.03 per unit area of soy beans (agricultural production US). Key index words: Algal Turf Scrubber; biochemistry; nutrient removal; productivity enhancement; species composition Abbreviations: 2-D, two-dimensional; 3-D, three- dimensional; ATS TM , Algal Turf Scrubber; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; FAMEs, fatty acid methyl esters; GC, gas chromato- graph; GWR, Great Wicomico River; HDPE, high density polyethylene; ICP-OES, inductively coupled plasma optical emission spectroscopy; MSD, mass selective detector; PUFA's, polyunsaturated fatty acids