The influence of varying tidal exchange on the ecology of Elkhorn Slough

Transcription

1 The influence of varying tidal exchange on the ecology of Elkhorn Slough Amy Ritter and Kerstin Wasson K. Alt-Griffth, S. Connors, S. Lonhart, R. Preisler, E. Van Dyke, A. Woolfolk,

2 How do these restrictions of tidal flow affect community structure in Elkhorn Slough?

3 Flow regime categories 1. Full flow (no structures restricting tidal exchange) 2. Restricted flow 1. Muted during rainy season, tidal > freshwater influence 2. Minimal during rainy season, freshwater > tidal influence

4 Roadmap to talk Synthesis of several studies looking at how various groups of organisms respond to differences in tidal influence Potential mechanisms influencing biological patterns Implications for management

5 Summary of studies synthesized The following studies examined how assemblage and community structure varied across flow regimes in Elkhorn Slough: Fishes and crabs -Ritter, Preisler Aquatic invertebrates, algae, birds, and mammals - Wasson, Lonhart, Ritter Shorebirds - Connors Aquatic/terrestrial inverts -Alt-Griffith Marsh ecotone plants - Wasson and Woolfolk

6 Map of flow regime sites

7 Fish + Crab Study - Ritter and Preisler Data on average fish and crab abundance Surveyed 19 shallow-water sites throughout Elkhorn Slough in early spring and late summer (2005) Used seines and both large and small minnow traps (3 replicates of each) to sample fishes and crabs Amy Ritter, Rikke Preisler

8 Fish + Crab Study - Ritter and Preisler Data on average fish and crab abundance Multivariate data analysis: Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Transform: Fourth root Resemblance: S17 Bray Curtis similarity Crazy Cow Porter-Blohm Struve 2D Stress: 0.09 L Moro Cojo FLOW FULL MUTED MINIMAL Multidimensional scaling (MDS - graph) M Azevedo Analysis of similarities (ANOSIM - table): Pairwise Tests R Significance Groups Statistic Level FULL, MUTED FULL, MINIMAL MUTED, MINIMAL

9 Fish + Crab Study - Ritter and Preisler Data on average fish and crab abundance Multivariate data analysis: Multidimensional scaling Correlations between fish and crab species and MDS scores (> 0.45) MDS Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Transform: Fourth root Resemblance: S17 Bray Curtis similarity Crazy Cow Porter-Blohm Struve 2D Stress: 0.09 L Moro Cojo FLOW FULL MUTED MINIMAL 0.5 Correlation with MDS 2 Topsmelt Eur. green crab 0 Ore. shore crab 3-spine stickleback Longjaw mudsucker Shiner surfperch Staghorn sculpin Tidewater goby MDS 1 M Azevedo Cal. halibut Correlation with MDS 1

10 Fish + Crab Study - Ritter and Preisler Similarity percentages (SIMPER) results FULL MUTED MINIMAL Topsmelt Topsmelt 3-spine stickleback Ore. lined-shore crab Ore. lined-shore crab Longjaw mudsucker Staghorn sculpin Staghorn sculpin Topsmelt European green crab Goby complex Tidewater goby** Goby complex* Long-jaw mudsucker European green crab *Goby complex: Clevelandia ios and Lepidogobius lepidus ** Tidewater goby only found in 2/9 minimal flow sites

11 Fish + Crab Study - Ritter and Preisler Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Transform: Fourth root Resemblance: S17 Bray Curtis similarity M Azevedo Crazy Cow Porter-Blohm Struve 2D Stress: 0.09 L Moro Cojo FLOW FULL MUTED MINIMAL Leptocottus armatus (staghorn sculpin) % Differences between flow regimes: Whistlestop Transform: Fourth root Resemblance: S17 Bray Curtis similarity 2D Stress: 0.09 Crazy Cow Porter-Blohm LA 0.7 Full vs. Muted: 5.41 Full vs. Minimal: 8.77 S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Struve L Moro Cojo Muted vs. Min.: 9.70 M Azevedo *Expected if all spp contribute evenly = 100/23 = 4.35%

12 Fish + Crab Study - Ritter and Preisler Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Transform: Fourth root Resemblance: S17 Bray Curtis similarity M Azevedo Crazy Cow Porter-Blohm Struve 2D Stress: 0.09 L Moro Cojo FLOW FULL MUTED MINIMAL Atherinops affinis (topsmelt) % Differences between flow regimes: Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson Transform: Fourth root Resemblance: S17 Bray Curtis similarity S Azevedo Packard Pond N Strawberry Estrada 2D Stress: 0.09 Crazy Cow Porter-Blohm Struve L Moro Cojo AA Full vs. Muted: Full vs. Minimal: Muted vs. Min.: M Azevedo *Expected if all spp contribute evenly = 100/23 = 4.35%

13 Fish + Crab Study - Ritter and Preisler Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Transform: Fourth root Resemblance: S17 Bray Curtis similarity M Azevedo Crazy Cow Porter-Blohm Struve 2D Stress: 0.09 L Moro Cojo FLOW FULL MUTED MINIMAL Gasterosteus aculeatus (threespine stickleback) % Differences between flow regimes: Transform: Fourth root Resemblance: S17 Bray Curtis similarity 2D Stress: 0.09 GA Full vs. Muted: 7.82 Whistlestop S Marsh Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh Hudson S Azevedo Packard Pond N Strawberry Estrada Crazy Cow Porter-Blohm Struve L Moro Cojo Full vs. Minimal: Muted vs. Min.: M Azevedo *Expected if all spp contribute evenly = 100/23 = 4.35%

14 Community Study - Wasson et al. Data on presence of multiple species of inverts, algae, birds, mammals Surveyed 15 sites throughout Elkhorn Slough (2005) Used sediment cores and visual surveys of soft and hard substrate types to quantify species presence Kerstin Wasson, Steve Lonhart, Amy Ritter

15 Community Study - Wasson et al. Data on presence of multiple species of inverts, algae, birds, mammals Hidden Moro Cojo Railroad Resemblance: S17 Bray Curtis similarity 2D Stress: 0.1 FLOW FULL MUTED MINIMAL Multivariate data analysis: MDS (graph) S Harbor Whistlestop Old Mouth N Azevedo N Marsh Exit Hudsons Kirby N Marsh N Harbor L Moro Cojo Porter-Blohm Struve S Azevedo ANOSIM (table): Pairwise Tests R Significance Groups Statistic Level FULL, MUTED FULL, MINIMAL MUTED, MINIMAL

16 Community Study - Wasson et al. Similarity percentages (SIMPER) results FULL MUTED MINIMAL Amphipods Amphipods Sea lettuce complex* Polychaetes Sea lettuce complex* Water boatmen Sea lettuce complex* Jap. mud snail Brackish snail Amethyst gem clam Nemerteans Black-necked stilt Japanese mud snail Acorn barnacles Bay mussel complex** Red turf algae Diadumene anemones Polychaetes *Sea lettuce complex: Ulva fenestrata, U. linza, and U. intestinalis **Bay mussel complex: Mytilus galloprovincialis and M. trossulus

17 Invertebrate Study - Alt-Griffith Data on abundance of inverts (aquatic and terrestrial) Surveyed 21 sites throughout Elkhorn Slough in summer and winter (2005) Used astroturf collectors to sample invertebrates at the lower edge of the marsh zone

18 Invertebrate Study - Alt-Griffith Data on abundance of inverts (aquatic and terrestrial) Multivariate data analysis: MDS (graph) ANOSIM (table): Old Mouth Five Fingers N Harbor Transform: Fourth root Resemblance: S17 Bray Curtis similarity Coyote Dominic's Hudson M Azevedo Packard Main Whistlestop Yampah Estrada Kirby Campagna Struve Hummingbird Porter-Blohm Hidden MLML Marsh Moro Cojo Bridge S Azevedo Crazy Cow 2D Stress: 0.2 FLOW FULL MUTED MINIMAL Pairwise Tests R Significance Groups Statistic Level FULL, MUTED FULL, MINIMAL MUTED, MINIMAL

19 Invertebrate Study - Alt-Griffith Similarity percentages (SIMPER) results FULL MUTED MINIMAL Estuarine amphipod Estuar. amphipod Water boatmen Beach hopper Jap. mud snail Estuar. amphipod Amethyst gem clam Brachyceran flies Mussel shrimp/ostracods Spiders Spiders Brine flies Shore bugs Mussel shrimp/ostracods Japanese mud snail Calif. Assiminea snail

20 Shorebird Study - Connors Data on average abundance of shorebirds Visual surveys of 17 sites throughout Elkhorn Slough Multiple surveys conducted during spring, fall, and winter ( ) Sarah Connors

21 Shorebird Study - Connors Data on abundance of shorebirds Multivariate data analysis: MDS (graph) ANOSIM (table): Salinas River ES-E N Harbor ES-C ES-D Five ES-A ES-B Fingers Old Mouth S Marsh Moro Cojo N Marsh Porter-Blohm E Salt ponds W Salt ponds N Strawberry Transform: Fourth root Resemblance: S17 Bray Curtis similarity 2D Stress: 0.04 Estrada FLOW FULL MUTED MINIMAL Pairwise Tests R Significance Groups Statistic Level FULL, MUTED FULL, MINIMAL MUTED, MINIMAL

22 Shorebird Study - Connors Similarity percentages (SIMPER) results FULL MUTED MINIMAL Least sandpiper Least sandpiper Black-necked stilt Western sandpiper Western sandpiper Least sandpiper Willet Dunlin American avocet Marbled godwit Marbled godwit Western sandpiper Dunlin Dowitcher Dowitcher Dowitcher Willet Black-bellied plover

23 Marsh Plant Study -Wasson +Woolfolk Data on marsh plant relative abundance 18 sites around Elkhorn Slough 3 transects / site to assess plant assemblages and soil parameters Kerstin Wasson, Andrew Woolfolk

24 Marsh Plant Study - Wasson +Woolfolk Data on marsh plant relative abundance MLML Marsh Azevedo Pen Transform: Square root Resemblance: S17 Bray Curtis similarity Old Mouth N Azevedo 2D Stress: 0.12 FLOW FULL MUTED MINIMAL Multivariate data analysis: Estrada Yampah Crazy Cow Coyote N Marsh Struve MDS (graph) Whistlestop Porter-Blohm ANOSIM (table): Pairwise Tests R Significance Groups Statistic Level FULL, MUTED FULL, MINIMAL MUTED, MINIMAL

25 Marsh Plant Study - Wasson +Woolfolk Ecotone width* shows similar pattern as multivariate community analysis: muted flow is the outlier, with a very narrow band of ecotone *distance from 100% cover by marsh plants to 100% by upland plants Ecotone Width (cm) FULL MUTED MINIMAL

26 Marsh Plant Study - Wasson +Woolfolk Similarity percentages (SIMPER) results FULL MUTED MINIMAL Pickleweed Pickleweed Pickleweed Alkali heath Saltgrass Jointed charlock/ Wild radish Saltgrass Unidentified fescue Fleshy jaumea Soft chess

27 Fish and crab study Whistlestop Hudson S Marsh 2D Stress: 0.09 Crazy Cow Porter-Blohm FLOW FULL MUTED MINIMAL Community study Moro Cojo Railroad 2D Stress: 0.1 FLOW FULL MUTED MINIMAL Coyote Hidden Packard Hummingbird Main Old Mouth Kirby N Marsh S Azevedo Packard Pond N Strawberry Estrada M Azevedo Struve L Moro Cojo Hidden S Harbor Whistlestop Old Mouth N Azevedo N Marsh Exit Hudsons Kirby N Marsh N Harbor L Moro Cojo Porter-Blohm Struve S Azevedo Invertebrate study Coyote Dominic'sHudson M Azevedo Packard Main Whistlestop Yampah Estrada Kirby Campagna Struve Hummingbird Porter-Blohm Hidden 2D Stress: 0.2 FLOW FULL MUTED MINIMAL Old Mouth Five Fingers MLML Marsh S Azevedo N Harbor Moro Cojo Bridge Crazy Cow 3 studies found significant differences in assemblage/community structure between minimal flow and both muted/full regimes

28 Shorebird study N Strawberry Moro Cojo Salinas River ES-E N Marsh N Harbor ES-C ES-D Porter-Blohm Five ES-A ES-B Fingers Old Mouth S Marsh W Salt ponds E Salt ponds 2D Stress: 0.04 Estrada FLOW FULL MUTED MINIMAL 1 study found significant differences in assemblage structure between full flow and minimal flow regimes only Marsh plant study Old Mouth MLML Marsh 2D Stress: 0.12 FLOW FULL MUTED MINIMAL N Azevedo Azevedo Pen Struve Coyote Estrada N Marsh Whistlestop Crazy Cow Yampah Porter-Blohm 1 study found significant differences in assemblage structure only between full flow and muted flow regimes

29 Species Richness (# spp / regime) Fishes FULL MUTED MINIMAL Invertebrates FULL MUTED MINIMAL Birds FULL MUTED MINIMAL 1 Producers Freshwater/Terrestrial NON-NATIVE Freshwater/Terrestrial NATIVE Estuarine NON-NATIVE Estuarine NATIVE Marine NON-NATIVE Marine NATIVE FULL MUTED MINIMAL

30 Summary of results Multivariate showed effect of flow regime, but differences by study/indicator Minimal most different Most threatened spp found in minimal Univariate analysis by taxon shows differences across taxa Reduced richness in minimal for fish and inverts In general, more freshwater influence in minimal, more marine influence in muted

31 Roadmap to talk Synthesis of several studies looking at how various groups of organisms respond to differences in tidal influence Potential mechanisms influencing biological patterns Implications for management

32 Potential mechanisms behind ecological patterns across flow regimes Structures can restrict transport of organisms e.g. behavior, mobility, size Structures can alter conditions upstream e.g. physical, chemical X A B C C D E X A B C XD X E XA X B C D E

33 Water Quality Data Monthly volunteer snapshot surveys Muted/minimal flow sites tend to have smaller tidal range and lower rainy season salinity, and greater values of all other factors compared to full flow sites MDS 2 S Marsh Kirby Reserve N Skippers Bridge Harbor S Harbor M Azevedo Old Mouth Hudsons N Marsh Struve Crazy Cow Normalise Resemblance: D1 Euclidean distance S Azevedo 2D Stress: 0.08 FLOW FULL MUTED MINIMAL Correlation with 0.0 MDS 2 Salinity (rainy) Tidal Range Salinity (dry) Temperature Turbidity_ ph DO NH3-0.5 L Moro Cojo Porter NOX PO4 MDS Correlation with MDS 1

34 Roadmap to talk Synthesis of several studies looking at how various groups of organisms respond to differences in tidal influence Potential mechanisms influencing biological patterns Implications for management

35 Implications for management Biological data supports that there is a mosaic of habitats throughout the slough (esp. minimal are different from full flow sites ) Mosaic increases overall biodiversity in the Slough Full and muted are very similar for most taxa While minimal has lowest species richness overall, it harbors unique species and some threatened species

36 Restricted flow sites at Elkhorn Slough span a continuum of tidal exchange South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide)

37 Also a continuum of habitat use by potential conservation targets South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide) threatened brackish species e.g. tidewater goby, Tryonia snail key marine visitors e.g. migratory shorebirds, commercial fish nurseries

38 And a continuum of ecological concerns South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide) Low tidal exhange Limited flushing can result in poor water quality, and these habitats have limited connectivity with the estuarine network, but habitats are not subject to tidal erosion High tidal exchange Good flushing improves water quality, and there is good connectivity, but some habitats are subject to tidal erosion

39 Restricted flow sites at Elkhorn Slough span a continuum of tidal exchange South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide) Do we want representation of all parts of this continuum for the future? In what proportion?

40 Restricted flow sites at Elkhorn Slough span a continuum of tidal exchange South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide) Straw man for even representation of entire spectrum

41 Restricted flow sites at Elkhorn Slough span a continuum of tidal exchange South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough TIDAL RANGE (in cm, measured on a spring tide) Straw man for Goldilocks model: aim for middle range, with no representation of extremes

42 Do we want representation of the entire continuum of tidal exchange? In what proportion? What are the key ecological values of each flow regime? Key concerns? What are the consequences of limited connectivity between restricted and unrestricted flow sites? How long are estuarine assemblages likely to persist in minimal flow sites managed for no tidal exchange? Do any existing restricted exchange sites seem like they would be good models for the proposed tidal restriction project at Parson s?