Are There Effects at the Ecosystem Level?

Transcription

1 Springs and utrients Are There Effects at the Ecosystem Level? January 29, 2008 Robert L. Knight, Ph.D. Sky K. otestein, M.S. Wetland Solutions, Inc. ( Ecosystem-Level Effects Chapter Outline Chapter 1 - Springs as Ecosystems Springs Ecosystem Model Environmental Forcing Functions Energy Storages/Structure Ecosystem-Level Processes Human and Aesthetic Uses Chapter 6 - Effects of utrients on Spring Ecosystems Primary Producers Community Metabolism Community Structure Human and Aesthetic Effects Additional Research eeds and Questions 1

2 Sun (S) Groundwater (GW) Surface Water (SW) Surface Water (SSW) Atmosphere (A) Aquatic Plants & Consumers (SSAB) Economy (E) Springs as Ecosystems Springs and spring runs represent a unique class of aquatic ecosystems with distinct structures and processes. Due to their complexity, a holistic approach to spring studies is necessary to understand anthropogenic effects on these ecosystems. Silver Springs Ecosystem Model (Odum et al. 1998) Springshed-Spring Linkages Development of a management strategy for springs will be dependent upon a better understanding of the relative importance and synergism of direct stressors at the local level and indirect stresses that occur at the regional scale. Sun (S) Springshed Atmosphere (A) Evapotranspiration Economy (E) 2,3 8 Goods & Services 10 $ 4, atural Lands (L) 6,7 Outflows 16,17 X 12,13 1 X $ Downstream Export Silver Springs (SS) 22,23,24, , ,28 Groundwater Ground Pumping Water (GW) $ 14,15 Outflows 16,17 6, ,19 20 Evapotranspiration 22,23 $ Surface Water 1 Outflows Spring $ 24,25 Downstream Particulate Export $ Developed Lands (DL) Silver Springs Ecosystem to 1,200-m Station 26 Silver Springs Springshed 2

3 The Study of Springs Why study springs at the ecosystem level? Most springs studies: examined one or a few components of the ecosystem, such as aquatic plants, invertebrates, or water chemistry components are measured as amounts rather than rates, for example, aquatic plant biomass vs. aquatic plant productivity focused on the factors that are different between springs rather than on their underlying similarities. The Study of Springs Why study ecosystem metabolism? Ecosystem metabolism is measured by techniques that record the activity of the entire ecosystem through its effects upon dissolved oxygen concentrations. Ecosystem metabolism is inclusive of all living organisms that transform carbon through the biological processes of primary productivity and respiratory metabolism. Allows quantification and comparison of multiple forcing functions, the trophic level structure, ecosystem-level processes, and provides a more holistic view of springs. Fortunately, there are some historical measures of spring ecosystem metabolism for comparison to current conditions. 3

4 Upstream-Downstream Ecosystem Metabolism Method Ecosystem-level metrics have promise for providing a better understanding of the properties that many springs have in common. Specifically, the upstreamdownstream oxygen change method for ecosystem metabolism measurement pioneered in these aquatic systems should be a standard method to accompany all new springs biological studies. Effects of utrients on Spring Ecosystems There are consistent inverse correlations between rising nutrient concentrations (for both nitrogen and phosphorus) and declining ecosystem primary production and photosynthetic efficiency. 4

5 Silver Springs: A 50-Year Retrospective Study (Munch et al. 2006) Ecological Efficiency vs. itrate- GPP Efficiency (g O2/mol) y = x R 2 = Ox- (mg/l) * Phosphorus concentrations are relatively stable at this spring Wekiva River and Rock Springs Run PLRG Analysis (Mattson et al. 2006) Corroborative Ecosystem-Level Findings (Wekiva, Rock, Alexander, Juniper Springs) GPP Efficiency (g O2/mol) y = x R 2 = WR-1 WR-2 RSR-1 RSR-2 ASC-1 JC Ox- (mg/l) * A similar correlation between TP and GPP Efficiency was also observed. 5

6 Effects of utrients on Spring Ecosystems While this possible cause and effect relationship appears counter-intuitive, it may be explained based on the subsidy-stress hypothesis. Subsidy-Stress Hypothesis Hypothetical example of two types of inputs and their resulting ecosystem perturbations due to increasing input levels. utrients and nitrate in particular could be viewed as an example of a usable input (top curve), which have a subsidy effect on ecosystem productivity to a point, beyond which stress is incurred (Figure from E. P. Odum et al. 1979). 6

7 Effects of utrients on Spring Ecosystems Subsidy-Stress Hypothesis Low nitrate levels may be optimal for ecosystem productivity while higher levels may have the opposite effect of reducing overall production. In their natural, low nutrient state, springs may be adapted for optimal efficiency of light utilization and maximum ecosystem metabolism. Rising nutrient levels may result in the competitive advantage of weedy plant species that can capture light and spatial resources through higher rates of net productivity but lower gross productivity. Effects of utrients on Spring Ecosystems Elevated nutrient levels in concert with changes in other control mechanisms (such as recreation, flow rates, or grazing) may be linked to the observed plant community shifts, from adapted submerged aquatic plants with sparse but productive periphyton communities to systems dominated by benthic and attached filamentous algae. 7

8 Effects of Multiple Stressors on Spring Ecosystems Other possible stresses affecting primary producers in springs include: decreased dissolved oxygen in groundwater inflows altered grazer populations and introduction of exotic species reductions in flow volume recreational disturbance increased stormwater runoff dams and other water management activities aquatic plant management invasion by exotic plant and animal species The diversity of anthropogenic stressors illustrates the importance of an ecosystem-function level examination of springs. Recommendations for the Quantification of utrient Effects on Spring Ecosystems The manner in which spring ecosystems can be monitored for impacts resulting from nitrate or other nutrient pollutants as well as other stressors are presented as well as remaining research needs. Three recommended approaches for springs ecosystem nutrient-effects research: Synoptic studies of multiple springs to provide a better baseline for inter-spring comparisons Intra-spring comparisons In situ mesocosm studies Whole spring manipulation studies 8

9 ID Spring ame 0 Alexander Springs 1 Chassahowitzka Springs Group 2 Fanning Springs 3 Gainer Springs Group 4 Homosassa Springs Group 5 Ichetucknee Springs Group 6 Jackson Blue Spring 7 Kings Bay Springs Group 8 Madison Blue Spring 9 Manatee Spring 10 Rainbow Springs Group 11 Silver Glen Springs Group 12 Silver Springs Group 13 Troy Spring 14 Volusia Blue Spring 15 Wacissa Springs Group 16 Wakulla Spring 17 Weeki Wachee Spring 18 Juniper Springs 19 Little River Spring 20 Ponce De Leon Springs 21 Rock Springs 22 Washington Blue Springs 23 Wekiwa Spring Spring ID Spring ID Spring ID Beecher Spring 1 Fenney Spring 45 Cedar Head Spring 89 Copper Spring 2 Hornsby Spring 46 Wakulla Tubing D-Tunnel 90 Green Cove Spring 3 Horn Spring 47 Gum Spring Main 91 Holton Creek Rise 4 Cypress Spring 48 Little River Spring 92 Orange Spring 5 Starbuck Spring 49 Wakulla Tubing C-Tunnel 93 Suwannee Springs 6 Turtle Spring 50 Double Spring 94 ewport Spring 7 Salt Spring (Hernando) 51 Jackson Mill Pond Spring 95 Waldo Spring 8 Hunter Spring 52 Wakulla Tubing B-Tunnel 96 Warm Mineral Spring 9 Ellaville Spring 53 Rainbow Spring #6 97 Santa Fe Spring (Columbia) 10 Falmouth Spring 54 Silver Spring Main 98 utall Rise 11 Alapaha River Rise 55 Hart Springs 99 Alexander Springs 12 Wacissa Springs #2 56 Otter Spring 100 Silver Glen Springs 13 Wakulla Tubing A/K-Tunnel 57 Bubbling Spring 101 Washington Blue Spring (Choctawhatchee) 14 Black Spring (Jackson) 58 Wekiwa Springs 102 Steinhatchee River Rise 15 Wakulla Tubing K-Tunnel 59 Rainbow Spring #1 103 Santa Fe River Rise (Alachua) 16 Wakulla Tubing A/D-Tunnel 60 Deleon Spring (Volusia) 104 Welaka Spring 17 Holmes Blue Spring 61 Ginnie Spring 105 Williford Spring 18 Jackson Blue Hole Spring 62 Reception Hall Spring 106 Juniper Springs 19 Homosassa #1 63 Devils Ear Spring (Gilchrist) 107 Columbia Spring 20 Sanlando Springs 64 Blue Grotto Spring 108 Fern Hammock Springs 21 Suwanacoochee Spring 65 Madison Blue Spring 109 Treehouse Spring 22 Gator Spring (Hernando) 66 Rainbow Spring #4 110 Salt Springs (Marion) 23 Homosassa #2 67 Rock Springs 111 Crays Rise 24 Chassahowitzka Spring Main 68 Mearson Spring 112 Washington Blue Spring (Econfina) 25 Citrus Blue Spring 69 Gilchrist Blue Spring 113 Big Spring (Big Blue Spring) (Jefferson) 26 Levy Blue Spring 70 Manatee Spring 114 Morrison Spring 27 Mission Spring 71 Sun Springs 115 Spring Creek Rise #1 28 Allen Mill Pond Spring 72 Telford Spring 116 St. Marks River Rise (Leon) 29 Chassahowitzka Spring #1 73 Owens Spring 117 Gainer Spring #1C 30 Magnolia Spring 74 Troy Spring 118 Spring Creek Rise #2 31 Homosassa #3 75 Buckhorn Spring 119 Tarpon Hole Spring 32 Rock Bluff Springs 76 Crystal Springs 120 Gainer Spring #3 33 Bugg Spring 77 Lafayette Blue Spring 121 Poe Spring 34 Blue Hole Spring (Columbia) 78 Running Springs 122 Shepherd Spring 35 Springboard Spring 79 Unknown Brunson Landing Spring 36 Volusia Blue Spring 80 Lithia Springs Major 124 Gainer Spring #2 37 Branford Spring 81 Hays Spring (Jackson) 125 Ponce De Leon Springs 38 Siphon Creek Rise 82 Jackson Blue Spring 126 Sulphur Spring (Hillsborough) 39 Little Springs (Hernando) 83 Shangri-La Springs 127 Rhodes Spring #1 40 Weeki Wachee Main Spring 84 Lafayette Ruth Spring 128 Rhodes Spring #2 41 Ichetucknee Head Spring (Suwannee) 85 Fanning Springs 129 Rhodes Spring #4 42 Guaranto Spring 86 Apopka Spring 130 atural Bridge Spring 43 Wakulla Spring 87 Beckton Springs 44 Gadsen Spring 88 Springs Research Recommendations Synoptic Inter- and Intra-Spring Study State-wide spring ecosystem metabolism baseline study over a wide range of nutrient conditions, flows, and conditions Stats Ox- Average Min Max Average Ox- (mg/l) Spring ID Springs Research Recommendations Synoptic Inter-Spring Study Comparisons of Control and Affected Springs: Define the range of normal and altered ecosystem metabolism in springs over a wide range of nutrient conditions, including upstream/downstream studies along nutrient gradients Implement controlled treatments in downstream reaches for comparison to upstream control reaches Define the trophic-level biomass pyramids and energy flows in these reference spring systems 9

10 Springs Research Recommendations In Situ Flow-Through Mesocosm Studies Springs Research Recommendations In Situ Flow-Through Mesocosm Studies Controlled Ecosystem-Level Studies: Mesocosm studies in situ to determine the effects of nutrient levels on key primary producers and effects of consumers on various natural and weedy benthic and periphytic algal assemblages utrient addition studies Single species macrophyte and macroalgae productivity studies Consumer manipulation studies 10

11 Springs Research Recommendations Whole-Spring Manipulation Studies Before-and-after recreation reduction/elimination studies Exotic plant management studies Consumer control studies Summary Effects of utrients on Spring Ecosystems Evidence that the nutrients nitrogen and phosphorus can have negative impacts on springs (reduced ecosystem metabolism, increased coverage/abundance of filamentous algae and periphyton). utrients are not the entire story, declines in springs appearance are also linked to recreation impacts, the management of exotic plants and animals, and reductions in spring discharge. Springs ecology studies can be improved by measuring whole ecosystem metabolism. 11

12 Florida s Springs there exists a marvelous opportunity to study community metabolism and productivity Howard T. Odum (1957) 12