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Aquatic metabolism in the Everglades: Dominance of water column heterotrophy
Author(s) -
Hagerthey Scot E.,
Cole Jonathan J.,
Kilbane Deborah
Publication year - 2010
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2010.55.2.0653
Subject(s) - macrophyte , primary production , environmental science , ecosystem , trophic level , ecology , eutrophication , periphyton , water column , aquatic ecosystem , ecosystem respiration , biota , biomass (ecology) , nutrient , biology
Using high‐frequency measurements of free water dissolved oxygen (O2), we assessed gross primary production (GPP), respiration (R), and net aquatic production (NAP) in the shallow‐water Everglades peatland between 1996 and 2005. We distinguish NAP from net ecosystem production since the boundary for shallow aquatic ecosystems may include aboveground GPP of wetland biota. Metabolism was estimated for 68 sites distributed among nine habitats and yielded 1085 5‐d deployments or 5425 site‐days. Habitats differed in vegetation composition, trophic status, and hydrology. Systemwide O 2 averaged 3.8 ± 2.2 mg L −1 (mean ± SD), or 49% ± 30% of atmospheric saturation. GPP, R, and NAP averaged 103 ± 76, 220 ± 79, and −117 ± 65 mmol O 2 m −2 d −1 , respectively. Metabolism was greater during the summer‐wet season when greater irradiance, temperature, and material flux stimulate primary production and decomposition. Paradoxically, GPP was inversely related to total phosphorus (TP), with oligotrophic (TP < 7 mg L −1 ) open‐water habitats dominated by periphyton having the highest and eutrophic (TP > 35 mg L −1 ) habitats with dense emergent macrophytes the lowest rates. R was greatest for moderately enriched (TP = 15 mg L −1 ) open‐water habitats with floating macrophytes. The prevalence of net heterotrophy, 96% of the 1085 NAP estimates, reveals the importance of aboveground biota in regulating aquatic metabolism and O 2 dynamics in shallow ecosystems. R is not only regulated by the influx of aboveground autochthonous carbon but also by aquatic GPP. Carbon turnover is greater in habitats where O 2 production by aquatic vegetation enables aerobic respiration. Conversely, water‐column GPP is suppressed by dense emergent macrophytes, which limits O2 availability, favors anaerobic respiration, and reduces carbon turnover.