FOOD-WEB STRUCTURE IN BIG CYPRESS SWAMP WETLANDS BASED ON STABLE-ISOTOPE RESULTS William F. Loftus1 and David P.J. Green2,3 1 USGS – FISC, Everglades NP, Homestead, FL, USA; 2 Audubon of Florida, Tavernier Science Center, Tavernier, FL, USA; 3 FL Gulf Coast University, Ft. Myers, FL, USA

INTRODUCTION RESULTS: We analyzed 777 individual fishes of 24 taxa; 7 were non-native. We also analyzed 751 invertebrate samples of CROSS-LANDSCAPE COMPARISONS Southern Florida wetlands have been modified by drainage. A major restoration plan, 24 taxa and 733 vegetation samples of 24 taxa. Fish species names are in Table 1. Stoichiometric data for C:N showed that 14 CERP, is attempting to reestablish natural hydrology. CERP success implies aquatic food webs 15 13 0 0 as δ N values increased, C:N ratios decreased (Fig. 4). Most vegetation taxa had δ C values within + 2 /00 of -30 /00, except Big Cypress will be restored to support important predator populations. That premise is difficult to measure algae and moss. Values from BCNP biota were remarkably similar to those from Everglades marshes (Fig. 5). 12 Freshwater ‘Glades without data on those webs. From 2005-07, we collected biotic samples to map pathways of 10 TS Mangrove Zone V 14.0 60.00 Everglades energy flow and trophic status of biota in freshwater wetlands of Big Cypress National Preserve I 12.0 F Algae 8 SR Mangrove Zone 50.00 10.0 (BCNP) (Fig. 1 ). Food webs in cypress wetlands have been relatively unstudied throughout Py Amphipod

M 8.0 (‰) N 40.00 Crayfish Spoonbill chicks

A 15 6

their range. N 6.0 Fish 15 30.00 δ

Del 4.0 Insect Species used in comparison: C:N Ratio 20.00 Shrimp 2.0 4 • Gar / Mangrove snapper Vascular Pl. Food webs provide maps of their biotic constituents, their roles, and interactions. We used 10.00 0.0 • Gambusia / Rivulus 2 13 0.00 -2.0 • Grass Shrimp stable-isotope analysis to trace the movement of carbon (δ C) from primary producers to fishes, 0.00 2.00 4.00 6.00 8.00 10.00 -4.0 • Snails 15 -35.0 -30.0 -25.0 -20.0 -15.0 -10.0 -5.0 0.0 0 del 15N • Amphipods and to determine the trophic positions of animals by using nitrogen (δ N). General del 13C -33 -28 -23 -18 -13

V 14.00 13 60.00 Algae δ C (‰) Basic questions included: Patterns I 12.00 Big Cypress Amphipod 50.00 F 10.00 Py What are the major primary producers? Crayfish Distinct food webs are evident in south Florida studies; data may serve to 40.00 A 8.00

N Insect 15 relate spatial data to key indicator species. For example, Roseate Spoonbills How long are food chains? M 6.00

30.00 del 4.00 Moss (pink circle; mean + 1 SE; N=8) receive energetic inputs from Taylor Slough Is there spatio-temporal variability in the web? C:N Ratio 20.00 2.00 Python mangroves, near nesting locations and flight paths to foraging grounds What roles do non-native fishes play? 10.00 0.00 Snail -2.00 Shrimp (Lorenz data). 0.00 -40.00 -35.00 -30.00 -25.00 -20.00 -4.00 Vascular Pl. -40.00 -35.00 -30.00 -25.00 -20.00 -15.00 -10.00 -5.00 0.00 13 Fish Figure 1. Cypress Forest. del C del 13C

METHODS AND STUDY LOCATIONS Fig. 4. Bi-plots of δ13C and δ15N with C:N ratios for Fig. 5. Comparison bi-plots for taxa with all data combined CONCLUSIONS groups of biota. V=Vascular Plants, I=Insects, from the Everglades (Loftus 2000) and BCNP (this study). Primary producer, invertebrate, and fish samples of common species (Table 1) were taken F=Fish, Py=Python, A=Algae, and M=Moss. Isotope values varied temporally and spatially, and were similar to those from the Everglades. Cypress dome δ13C values tended to be more depleted compared with other three times per year: wet season, transitional season, and dry season. Sampling was at three sites δ15N values from Everglades animals appear enriched compared to BCNP values. Myriad factors influence δ15N values. For example, within BCNP cypress habitats: L-28, Bear Island (BI), and Raccoon Point (RP) (Figure 2). Site south Florida systems. Both detritus and algae were food base end-members. Snails, enrichment may indicate Everglades organisms function at higher trophic levels than conspecifics in BCNP, or it may imply differences in source, crayfishes, and amphipods were major 1o consumers, while fishes, shrimp, and most insects descriptions, sampling techniques, and physico-chemical data were reported in Liston et al. fractionation, or assimilation processes in primary producers at the base of the food web. were mainly carnivorous. As prairies dried in fall, animals moved into cypress domes but (2008) (Fig. 3). Three to five individuals or sub-samples were collected for each taxon from each food-web plots showed little evidence for movement. Piscivorous Florida gar had the 2005-06 15 L-28 highest δ N values and highest relative trophic positions. Non-native fishes functioned at sub-habitat (marsh & dome). Bear Island I-75 Seasonal Comparisons: As animals move similar trophic levels to native species and used a similar range of primary producers. BIG CYPRESS from marsh to dome from wet to transition (Liston NATIONAL PRESERVE Samples were field-frozen, then measured in the lab prior to drying Raccoon Point Et al, 2008), do isotope values reflect those movements? FUTURE WORK appropriate tissues at 50 C. Plant material was acid-treated to remove carbonate. RP – Wet, Marsh RP – Wet, Dome HQ US 41

AMPHIPOD AMPHIPOD 8 8 Dried tissue was pulverized, weighed, and prepared for analysis by mass CRAYFISH CRAYFISH We will explore the dataset with analytical tools such as the IsoSource (Phillips and 7 FISH 7 FISH INSECT INSECT 6 SNAIL 6 SHRIMP Gregg 2003) and circular statistical models (Schmidt et al. 2007) to examine mixing of spectrometer at FIU (see Williams & Trexler, 2006). Algae SNAIL 5 5 N 15 PERIPHYTON DETRITUS δ N 4 UTRICULARIA 4 UTRICULARIA primary producers in the cypress. We will investigate effects of lipids on values, and will 5 0 5 10 Km Spatial/ 3 3 2 2 also compare data quantitatively to food webs from other systems. Error bars not shown on figures for clarity of presentation. Figure 2. Maps of study locations Temporal 1 1 0 0 -33.50 -31.50 -29.50 -27.50 -25.50 -23.50 -21.50 -33.50 -31.50 -29.50 -27.50 -25.50 -23.50 -21.50 13 APPLICATIONS Comparisons Amphipod δ C δ13C

100 BI 80 Fish Hydrological restoration should restore aquatic food webs supporting populations 60 By Year Insect 40 b) Invertebrates a) Fishes AMPHIPOD

20 8 of higher vertebrates. Our data can help test that premise by defining spatio-temporal

Shrimp CRAYFISH Estimated water depth (cm) depth water Estimated Estimated water depth (cm) depth water Estimated FISH 0 Scientific Name Common Name % % I 7 Figure 3. BCNP water Scientific Name Common Name % RA % I INSECT -20 6 patterns in cypress-wetland food webs as a baseline for post-restoration comparisons. SHRIMP Jun Sep Dec Mar Jun Sep Dec Mar Jun RA Vascular P. 05 05 05 06 06 06 06 07 07 SNAIL Date Gambusia holbrooki Eastern mosquitofish 56.7 84.5 5 120 depths showing strong ALGAE 100 L28 Palaemonetes paludosus Grass shrimp 46.2 62 V - Algae 4 DETRITUS 80 15 60 seasonal patterns at the Jordanella floridae Flagfish 20.8 40.8 δ N UTRICULARIA Hydrologic restoration will affect aquatic plant communities at the food-web base. 40 Procambarus alleni Everglades crayfish 12.4 62.7 3 20 V - Moss

0 2 -20 three study sites: Bear Heterandria formosa Least killifish 10.2 43.7 Procambarus fallax Slough crayfish 5.6 54.9 15 We hypothesize that changes at the base will affect key invertebrate groups, with

-40 δ N 2006-07 1 Estimated water depth (cm) depth Estimatedwater Estimated water depth (cm) depth Estimatedwater -60 -80 Island (BI), L-28, and Gyrinus spp. Whirligig water beetle 4.4 13.4 0 -100 Lepomis marginatus Dollar sunfish 2.8 29.6 -33.50 -31.50 -29.50 -27.50 -25.50 -23.50 -21.50 Jun Sep Dec Mar Jun Sep Dec Mar Jun consequences resonating through the web. Stable-isotope analyses will permit tracing of 05 05 05 06 06 06 06 07 07 Date Anisoptera Dragonfly 3.6 63.4 100 Raccoon Point (RP). RP Lucania goodei Bluefin killifish 2.6 46.5 80 Coleoptera Aquatic beetle 2.4 20.4 RP – Transition, Dome food-web changes at both local and landscape scales. Our data will complement other 60 Lepomis gulosus Warmouth 2.1 30.3 40 Coenagrionidae Damselfly 0.7 14.8 south Florida food-web studies to provide a more comprehensive understanding of the 20 Figure 7. Values in wet-season marshes are enriched

0 Labidesthes sicculus Brook silverside 1.6 15.5 Planorbella spp. Planorbid snail 0.7 21.8

Estimated water depth (cm)(cm) depth depth EstimatedEstimatedwater water -20 compared to domes. We see little evidence of enrichment entire ecosystem. -40 Jun Sep Dec Mar Jun Sep Dec Mar Jun Ameiurus natalis Yellow bullhead 1.3 4.2 Corixidae Water boatman 0.4 9.2 05 05 05 06 06 06 06 07 07 Date signal in the transition-season domes, 1.5 months later, that Pelocoris femoratus Alligator flea 0.4 16.2 Poecilia latipinna Sailfin molly 0.8 11.3 we would expect as animals enter the domes for dry-season Predaceous diving Dytiscidae 0.3 5.6 LITERATURE CITED Cichlasoma bimaculatum Black acara 0.7 22.5 beetle shelter. We will continue to examine these data. Elassoma evergladei Everglades pygmy sunfish 0.6 16.9 Lethocerus spp. Toe biter 0.3 11.3 Liston, S. et al. 2008. Development and testing of protocols for sampling fishes in forested wetlands in southern Florida. Draft report to Physella spp. Physid snail 0.3 8.5 Fundulus chrysotus Golden topminnow 0.4 15.5 USACOE and USGS-PES. Belostoma spp. Giant water bug 0.1 7.7 10.00 Loftus, W.F. 2000. Mercury bioaccumulation through an Everglades aquatic food web. Ph.D. Dissert., Florida International University, Clarias batrachus Walking catfish 0.3 1.4 Ephemeroptera Mayfly 0.01 1.4 9.00 Oscar Miami. Hoplosternum littorale Brown hoplo catfish 0.2 7.7 Ranatra spp. Water scorpion 0.01 3.5 Non-native Pike 8.00 Phillips, D.L., and J.W. Gregg. 2003. Source partitioning with stable isotopes: coping with too many sources. Oecologia 136:261-269. Enneacanthus gloriosus Bluespotted sunfish 0.2 9.2 Acara Ea. mosquitofish N Mayan 15 7.00 Post et al. 2007. Getting to the fat of the matter: models, methods, and assumptions for dealing with lipids in stable isotope analysis. Cichlasoma urophthalmus Mayan cichlid 0.2 8.5 Fishes Clarias (Gambusia holbrooki) del Oecologia 152: 179-189. 6.00 Hoplo Notemigonus crysoleucas Golden shiner 0.1 4.2 SpotTilap Schmidt, S.N. et al. 2007. Quantitative approaches to the analysis of stable isotope food web data. Ecology 88:2793-2802. 5.00 Native Tilapia mariae Spotted tilapia 0.1 4.2 Williams, A.J. and J.C. Trexler. 2006. A preliminary analysis of the correlation of food-web characteristics with hydrology and nutrient Lepomis punctatus Spotted sunfish 0.1 2.1 δ13C 4.00 Sailfin molly -34.00 -33.00 -32.00 -31.00 -30.00 -29.00 -28.00 -27.00 gradients in the southern Everglades. Hydrobiologia 569:494-503. Lepisosteus platyrhincus Florida gar 0.01 1.4 del 13C Fig. 6. Stable-isotope values for taxa consistent among locations & seasons. The three (Poecilia latipinna) Belonesox belizanus Pike killifish 0.01 0.7 locations had very similar isotope values, though fish/shrimp seemed more enriched at L-28. ACKNOWLEDGMENTS Least killifish Table 1. Relative abundance (%RA) and % Incidence in samples of a) common fishes and b) Most fish and insects were omnivores/carnivores. The web seems to have but three levels: Fig. 8. Introduced fish values overlapped those of native Funding provided by USGS South Florida PES Program, administered by G.R. Best, and by Army Corps of Engineers CERP-MAP. (Heterandria formosa) o o common invertebrates collected at the study sites (Liston et al., 2008). All taxa were producers, 1 consumers, and 2 consumers, with both algal and detrital bases important. By the species. Piscivorous Pike killifish had highest trophic Special thanks to S. Liston for project assistance, to B. Dunker, N. Katin and N. Silverman for field assistance, and J. Lorenz, J. Trexler, analyzed for stable-isotope values. dry season, domes had few species surviving. L-28 and RP were sites with contiguous marshes. position, as expected. and C. McIvor for help in the study. We also thank K. Dunlop, L. McCarthy, W. Anderson, M. Kershaw, and C. Rebenack for sample prep and analysis at the FIU-SERC mass-spectrometer facility.