uch has been written about the innovative Offshore Membrane Enclosures for Growing Algae (OMEGA) developed by NASA scientists for deployment on water.
OMEGA, an integrated aquatic system to produce biofuels, treat and recycle wastewater, capture CO2, and expand aquaculture production, includes floating photobioreactors (PBRs) that are intended to cover hundreds of hectares in marine bays.
In a recent article in Aquatic Biosystems, test results were revealed regarding the interactions of marine mammals and birds with the OMEGA system.
To assess the interactions of marine mammals and birds with PBRs, 9 × 1.3 m flat panel and 9.5 × 0.2 m tubular PBRs were deployed in a harbor and monitored day and night from October 10, 2011 to Janurary 22, 2012 using infrared video. To observe interactions with pinnipeds, two trained sea lions (Zalophus californianus) and one trained harbor seal (Phoca vitulina richardii) were observed and directed to interact with PBRs in tanks. To determine the forces required to puncture PBR plastic and the effects of weathering, Instron measurements were made with a sea otter (Enhydra lutris) tooth and bird beaks.
A total of 1,445 interactions of marine mammals and birds with PBRs were observed in 2,424 hours of recorded video. The 95 marine mammal interactions – 94 by sea otters and one by a sea lion – had average durations of three minutes (max 44 min) and represented about 1% of total recording time. The 1,350 bird interactions, primarily coots (Fulica americana) and gulls (Larus occidentalis and L. californicus), had average durations of six minutes (max. 170) and represented 5% of recording time.
Interactive behaviors were characterized as passive (feeding, walking, resting, grooming, and social activity) or proactive (biting, pecking, investigating, and unspecified manipulating). Mammal interactions were predominantly proactive, whereas birds were passive.
Interactions occurred primarily during the day. Ninety-six percent of otter interactions occurred in winter, whereas 73% of bird interactions in fall, correlating to their abundance in the harbor. Trained pinnipeds followed most commands to bite, drag, and haul-out onto PBRs, made no overt undirected interactions with the PBRs, but showed avoidance behavior to PBR tethers. Instron measurements indicated that sea-otter teeth and gull beaks can penetrate weathered plastic more easily than new plastic.
Other results of the test showed that otter and bird interactions with experimental PBRs were benign.