Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow,tropical, eutrophic lake (Laguna Lake,Philippines) |
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| Authors: | Eugene C Herrera Kazuo Nadaoka |
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| Affiliation: | 1. Institute of Civil Engineering, University of the Philippines, Diliman, Quezon City 1101, Philippines;2. Department of Transdisciplinary Science and Engineering, School of Environment and Society, Tokyo Institute of Technology, O-okayama 2-12-1 W8-13 Meguro, Tokyo 152-8552, Japan;1. Paleoecological Environmental Assessment and Research Laboratory, Department of Biology, 116 Barrie St., Queen’s University, Kingston K7L 3J9, Ontario, Canada;2. St. Lawrence River Institute of Environmental Sciences, 2 St. Lawrence Drive, Cornwall K6H 4Z1, Ontario, Canada;1. Central Michigan University, Department of Biology, Biosciences 2100, Mount Pleasant, MI, 48859, United States;2. Illinois Natural History Survey, 1816 S. Oak Street, Champaign, IL 61820, United States;3. Michigan Department of Environment, Great Lakes, and Energy, Drinking Water and Environmental Health Division, 525 W. Allegan Street, Lansing, MI 48933, United States;4. Michigan Department of Natural Resources, Oden State Fish Hatchery, 8258 S. Ayr Road, Alanson, MI 49706, United States;5. Michigan Department of Natural Resources, Charlevoix Fisheries Research Station, 96 Grant Street, Charlevoix, MI 49720, United States;6. The Nature Conservancy, 721 Flanner Hall, University of Notre Dame, Notre Dame, IN, United States;7. The Nature Conservancy, 101 E. César E. Chávez Avenue, Lansing, MI 48906, United States;1. Department of Biology, Northern Michigan University, Marquette, MI 49855, United States;2. Michigan Department of Natural Resources, Marquette, MI 49855, United States;1. Rubenstein Ecosystem Science Laboratory, University of Vermont, Burlington, VT, USA;2. Vermont Fish and Wildlife Department, Essex Junction, VT, USA;3. US Fish and Wildlife Service, Essex Junction, VT, USA;4. SUNY Plattsburgh, Plattsburgh, NY, USA |
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| Abstract: | The physical, chemical, and biological dynamics under changing atmospheric conditions of Laguna Lake, Philippines were analyzed from intensive observations. Diel measurements were conducted for 48 continuous hours for both dry and wet tropical seasons in addition to fine resolution long-term monitoring. Results revealed significant vertical and diel variations of lake variables in spite of a shallow water depth (2.5 m) caused by the intense surface heating from solar irradiance (~800 W m?2) and accentuated by the lake's high turbidity (16–32 ftu). Late afternoon land-lake breeze (~5–7 m s?1) regularly breaks daytime thermal stratification, and convective cooling at night maintains isothermal condition until dawn of the next day. The stratified condition demonstrated a wind-driven, density-induced 2-layer current pattern with a windward moving epilimnion (~4 folds faster) and a compensating hypolimnetic flow in the general lake circulation direction. Laguna Lake was observed to have a dominating diel cycle but also undergoes significant seasonal limnological variations brought primarily by climate, hydrology, and its interaction with the adjacent sea. Significantly correlated variations of pH, chlorophyll-a and DO in the dry season were indicative of the higher biological activity associated with the intrusion of polluted waters from Metro Manila. The non-occurrence of thermal over-turn was observed to be regularly followed by bottom hypoxic conditions (2–4 mg L?1), indicative of the eutrophic condition of the lake and the importance of diel wind-induced mixing in the bottom supply of DO. Laguna Lake was found to be predominantly net heterotrophic (GPP:R < 1, NEP < 0). |
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| Keywords: | Laguna de Bay Hydrodynamics Diel Tropical limnology Continuous monitoring Net ecosystem production |
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