Effects of hydrologic and water quality drivers on periphyton dynamics in the southern Everglades |
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Authors: | David M Iwaniec Daniel L Childers Damon Rondeau Christopher J Madden Colin Saunders |
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Institution: | (1) Department of Biological Sciences & SERC, Florida International University, Miami, FL 33199, USA;(2) Coastal Ecosystems Division, South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, FL 33416, USA |
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Abstract: | Everglades periphyton mats are tightly-coupled autotrophic (algae and cyanobacteria) and heterotrophic (eubacteria, fungi
and microinvertebrates) microbial assemblages. We investigated the effect of water column total phosphorus and nitrogen concentrations,
water depth and hydroperiod on periphyton of net production, respiration, nutrient content, and biomass. Our study sites were
located along four transects that extended southward with freshwater sheetflow through sawgrass-dominated marsh. The water
source for two of the transects were canal-driven and anchored at canal inputs. The two other transects were rain-driven (ombrotrophic)
and began in sawgrass-dominated marsh. Periphyton dynamics were examined for upstream and downstream effects within and across
the four transects. Although all study sites were characterized as short hydroperiod and phosphorus-limited oligotrophic,
they represent gradients of hydrologic regime, water source and water quality of the southern Everglades. Average periphyton
net production of 1.08 mg C AFDW−1 h−1 and periphyton whole system respiration of 0.38 mg C AFDW−1 h−1 rates were net autotrophic. Biomass was generally highest at ombrotrophic sites and sites downstream of canal inputs. Mean
biomass over all our study sites was high, 1517.30 g AFDW m−2. Periphyton was phosphorus-limited. Average periphyton total phosphorus content was 137.15 μg P g−1 and average periphyton total N:P ratio was 192:1. Periphyton N:P was a sensitive indicator of water source. Even at extremely
low mean water total phosphorus concentrations ( ≤ 0.21 μmol l−1), we found canal source effects on periphyton dynamics at sites adjacent to canal inputs, but not downstream of inflows.
These canal source effects were most pronounced at the onset of wet season with initial rewetting. Spatial and temporal variability
in periphyton dynamics could not solely be ascribed to water quality, but was often associated with both hydrology and water
source. |
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Keywords: | periphyton hydrology water quality phosphorus Everglades |
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