Spatio-Temporal Dynamics of SAV Abundance and Water Quality in the Mangrove Lakes Region of Florida Bay

Transcription

1 Spatio-Temporal Dynamics of SAV Abundance and Water Quality in the Mangrove Lakes Region of Florida Bay Thomas A. Frankovich 1, James W. Fourqurean 1, Douglas Morrison 2 1 Florida International University 2 Everglades National Park GEER 28, July 27 August 1, Naples FL.

2 Where are the Mangrove Lakes? USGS

3 Importance Wintering area for waterfowl Blue-winged teal Ruppia maritima American coot Extensive SAV beds (historically) Critical habitat for American crocodile Photos courtesy D. Chalfant, naturepicsonline, AnimalPlanet

4 Study Objectives To identify relationships between water quality and benthic macrophytes Sp. A Sp. B To use the identified relationships to predict changes in benthic macrophyte distribution and abundance that may result from changes in water quality produced by restoration efforts Water quality

5 Methods SAV % cover, quarterly (41 sites) -1/4 m 2 quadrat (5% intervals) - all benthic macrophytes - 15 replicates per site WQ monitoring, monthly - temp, sal, water depth, secchi depth (41 sites) - TotN, TotP, Phytoplankton chl-a (each basin 8 sites) Hourly water temperature, salinity, and water level - datasondes in West Lake, The Lungs, 7 Palms Lake Data collection ongoing April 26 April 29

6 Study Sites

7 Statistics Exploratory statistics - Cluster analysis - NMS ordination - Regression analyses Statistical model Discriminant Function Analysis - Logistic Regression

8 Results Benthic macrophytes Batophora oerstedii Chara hornemanni Halodule wrightii Acetabularia sp. Chara Hal. Bat. Ruppia Acet. Other Prevalence (%) Rel. abundance (%) <1 <1 Chara and Halodule dominate species assemblages Other Halimeda incrassata, Penicillus capitatus, Sargassum pteropleuron,laurencia sp., Thalassia testudinum, Polysiphonia sp., Caulerpa prolifera, Rhizophora mangle

9 Results Benthic macrophytes Chara 2 High abundance Low abundance 4 6 Halodule 8 1 S27 S41 S1 S4 S16 S18 S15 S37 S36 S17 S14 S21 S19 S39 S2 S38 S22 S33 S13 S34 S11 S12 S9 S8 S5 S7 S28 S32 S4 S23 S24 S35 S29 S25 S3 S2 S3 S1 S26 S6 S31 Similarity Samples Sites grouped according to differences in community structure

10 Results Benthic macrophytes Species distribution Chara characterizes upstream lakes Halodule characterizes coastal embayments

11 Results Benthic macrophytes Benthic macrophytes,, salinity Salinity distribution (mean 26 28) Species (Chara, Halodule) differentiate along salinity gradient

12 Results Benthic macrophytes Salinity Stress = 1.7 Chara Halodule NMS axis Florida Bay West system Palms system NMS axis 1 Salinity r 2 =.65 Differences in community structure are evident between Florida Bay sites, West system sites, and 7 Palms sites.

13 Results Benthic macrophytes Mean Percent Cover Chara Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul 6 5 Halodule Chara percent cover is minimum in summer and fall and peaks in winter and spring. Halodule percent cover is minimum in winter and spring and maximum in summer and fall. Mean Percent cover Seasonality is evident in Chara and Halodule, but timing is asynchronous. Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul 26-28

14 Results Temperature, salinity West Lake Temperature (C) Temperature (C) 7Palms Lake Sep Dec Mar Sep Dec Mar Salinity (ppt) Salinity (ppt) Sep Dec Mar Sep Dec Mar Sep Dec Mar Sep Dec Mar Sep Dec Mar Sep Dec Mar Water temperature maximum in summer, minimum in winter salinity increases during dry season (winter-spring), decreases during summer and fall.

15 Results Nutrients Total Nitrogen (μm) Palms Lake System 7 Palms Lake Site 2 Middle Lake Site 8 Monroe Lake Site 13 Terrapin Bay Site 17 Total Phosphorus (μm) Palms Lake System 7 Palms Lake Site 2 Middle Lake Site 8 Monroe Lake Site 13 Terrapin Bay Site 17 N:P 9:1 Apr Jul Oct Jan Apr Jul Oct Jan Apr Apr Jul Oct Jan Apr Jul Oct Jan Apr Total Nitrogen (μm) West Lake System West Lake Site 28 Long Lake Site 3 The Lungs Site 35 Garfield Bight Site 4 Total Phosphorus (μm) West Lake System West Lake Site 28 Long Lake Site 3 The Lungs Site 35 Garfield Bight Site 4 N:P 3:1 Apr Jul Oct Jan Apr Jul Oct Jan Apr Apr Jul Oct Jan Apr Jul Oct Jan Apr Spatial variation in nutrient concentrations more evident than seasonal variation. More nutrients in West Lake system. Phosphorus limitation less severe in West Lake system.

16 Results phytoplankton Chlorophyll a (ug L -1 ) Palms Lake System 7 Palms Lake site 2 Middle Lake site 8 Monroe Lake site 13 Terrapin Bay site 17 Chlorophyll a (ug L -1 ) West Lake System West Lake site 28 Long Lake site 3 The Lungs site 35 Garfield Bight site 4 Sep Dec Mar Sep Dec Mar Phytoplankton abundances 6X greater in West Lake system

17 Results phytoplankton Phytoplankton Chlorophyll vs Total Phosphorus Chl-a (μg L -1 ) r 2 =.46 P < Total phosphorus (μm) 7 Palms Lake system West Lake system Phytoplankton abundance correlated with P-availability

18 Results Benthic macrophytes 1 Chara abundance Water Clarity Water Clarity Index Percent Cover Water clarity index Secchi depth 1 2 cm cm cm 4 > 6 cm West system 7 Palms system Greater Chara abundance associated with increased water clarity

19 Key findings preliminary conclusions Spatial species distribution consistent with mean salinity. Seasonality of Chara and Halodule abundances asynchronous. P concentrations are 3X greater in West Lake system than in 7 Palms system, fueling 6X greater phytoplankton densities. Greater water clarities in 7 Palms system coincide with 5X greater Chara abundances relative to West Lake system.

20 Acknowledgments We thank: Dr. Bill Loftus for use of jonboat Steven Huddleston, Jeff Woods, Mark Zucker (USGS) for field collaboration many, many other field volunteers Funding provided by Everglades National Park