Evaluation of Methods to Increase Light Under Ferry Terminals

Blanton, Susan L. ; Thom, Ronald M. ; Borde, Amy B. ; Diefenderfer, Heida L. ; Southard, John A.

Pacific Northwest National Laboratory (U.S.)

关键词: Marinas;    Light Transmission;    Eelgrass;    Light;    Habitat;   

DOI  :  10.2172/15001597
RP-ID  :  PNNL-13714
RP-ID  :  AC05-76RL01830
RP-ID  :  15001597

美国|英语

来源: UNT Digital Library

【 摘 要 】

To address concerns of resource agencies about the potential impacts of ferry terminal expansion on valuable habitat functions and resource use of nearshore areas, the Pacific Northwest National Laboratory (PNNL), in partnership with the Washington State Department of Transportation (WSDOT), conducted field trials with off-the-shelf products that promote light passage through dock structures. These products included a SunTunnel, deck prisms, and a metal halide greenhouse light. Light measurements (photosynthetically active radiation, PAR) were also recorded beneath glass blocks and a metal grating installed at Clinton Ferry Terminal on Whidbey Island, WA. A review of other studies measuring the effects of dock shading and alternate dock materials was conducted. PAR measurements from this study were related to minimum requirements for eelgrass Zostera marina photosynthesis and to the known maximum photosynthetic ?saturation? rate for Z. marina. We also related PAR measurements to what we know about light effects on juvenile salmonid feeding and passage under overwater structures. Of the light technologies tested, the metal halide light, SunTunnel, glass blocks, and grating potentially provide enough light for eelgrass growth underneath a ferry terminal with similar construction to the Clinton Ferry Terminal. All of these technologies would potentially provide adequate light under conditions where eelgrass is located at its upper depth limit and a dock is close to the water surface. Light levels needed to allow fish to feed and to form schools are low (~ 1-2 mmol/m2/s), and much less than those required for photosynthesis. Our research indicates that installing any of the tested light products would likely maintain light levels under the dock above those required for active feeding by juvenile salmonids.