Light Apparatus for Mesocosm Photo‐manipulation (LAMP): An inexpensive waterproof lighting device for within‐lake mesocosm experiments

Abstract

Although light is a key biological driver, light additions to in‐lake experiments can be difficult, if not impossible. To address this problem, we developed an inexpensive Lighting Apparatus for Mesocosm Photo‐manipulation (LAMP), a device that can be deployed within experimental underwater enclosures to increase ambient light levels. Each apparatus consists of 12 Light Emitting Diode (LED) flashlights embedded within a watertight PVC frame. Through the use of a voltage regulator, each is wired to a 12V deep‐cycle marine battery. Twelve LAMPs were deployed during a 3.5‐week mesocosm experiment in Cranberry Lake in the Adirondack region of New York State and run 12 hours per day. LAMPs proved durable under harsh wind and weather conditions. Mesocosms with LAMPs had significantly higher average Photosynthetic Photon Flux Density (PPFD) in the water column than did controls (8% higher integrated Photosynthetic Active Radiation [PAR] over a 1.75 m depth, paired t test, P < 0.01). Other potential research applications for LAMPs include (1) testing light limitation in highly eutrophic systems where algal biomass may be self‐shading, (2) experimentation at depth (e.g., examination of light limitation at the deep chlorophyll maximum), (3) application at different depths or in water bodies where specific wavelengths have been naturally attenuated using LEDs with different spectral properties, (4) testing animal responses to light climate in the field, or (5) collection of macroinvertebrates or fish larvae in modified LAMP‐based light traps.