the influence of varying tidal exchange on the...

The influence of varying tidal exchange on the ecology of

Elkhorn Slough

Amy Ritter and Kerstin WassonK. Alt-Griffth, S. Connors, S. Lonhart, R. Preisler, E. Van Dyke, A. Woolfolk,

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

Slough?

Flow regime categories

1. Full flow (no structures restricting tidal exchange)

2. Restricted flow1. Muted – during rainy season,

tidal > freshwater influence

2. Minimal – during rainy season, freshwater > tidal influence

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

Summary of studies synthesizedThe 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

Map of flow regime sites

• 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

Fish + Crab Study - Ritter and Preisler

• Data on average fish and crab abundance

• Multivariate data analysis:– Multidimensional scaling

(MDS - graph)

– Analysis of similarities (ANOSIM - table):

Pairwise Tests R SignificanceGroups Statistic Level FULL, MUTED -0.071 0.690FULL, MINIMAL 0.88 0.001MUTED, MINIMAL 0.726 0.001

Transform: Fourth rootResemblance: S17 Bray Curtis similarity

FLOWFULLMUTEDMINIMAL

Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry

WhistlestopCrazy Cow

Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09




Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09

• Data on average fish and crab abundance • Multivariate data analysis: Multidimensional scaling• Correlations between fish and crab species and MDS

scores (> 0.45)

3-spine stickleback

Ore. shore crab

Topsmelt

Shiner surfperch

Eur. green crab

Tidewater goby

Longjawmudsucker

Staghorn sculpin

Cal. halibut

MDS 1

MDS 2

-1.0 0 1.0

Correlation with MDS 1

0.5

Correlation with

MDS 2

0

-0.75-2.0 2.00

0

-1.0

1.0


• Similarity percentages (SIMPER) resultsFULL MUTED MINIMAL

Topsmelt Topsmelt 3-spine sticklebackOre. lined-shore crab Ore. lined-shore crab Longjaw mudsuckerStaghorn sculpin Staghorn sculpin TopsmeltEuropean 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


Leptocottus armatus(staghorn sculpin)

% Differences between flow regimes:

•Full vs. Muted: 5.41

•Full vs. Minimal: 8.77

•Muted vs. Min.: 9.70

*Expected if all spp contribute evenly = 100/23 = 4.35%



Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09


LA

0.7

2.8

4.9

7

Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09


Atherinops affinis(topsmelt)








Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09


AA

20

80

140

200

Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09






Gasterosteusaculeatus(threespinestickleback)



GA

40

160

280

400

Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09



Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09


• 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

Community Study - Wasson et al.

• Data on presence of multiple species of inverts, algae, birds, mammals

• Multivariate data analysis:

– MDS (graph)

– ANOSIM (table):Pairwise Tests R SignificanceGroups Statistic LevelFULL, MUTED 0.192 0.135FULL, MINIMAL 0.852 0.008MUTED, MINIMAL 0.828 0.008

Community Study - Wasson et al. Resemblance: S17 Bray Curtis similarity


L Moro Cojo

Moro Cojo Railroad

Struve

S Harbor

N Harbor

Old Mouth

Porter-Blohm

S Azevedo

Whistlestop

Hidden

N MarshN Marsh Exit

N Azevedo

KirbyHudsons

2D Stress: 0.1


Amphipods Amphipods Sea lettuce complex*Polychaetes Sea lettuce complex* Water boatmenSea lettuce complex* Jap. mud snail Brackish snailAmethyst gem clam Nemerteans Black-necked stiltJapanese mud snail Red turf algaeAcorn barnacles Diadumene anemonesBay mussel complex** Polychaetes

*Sea lettuce complex: Ulva fenestrata, U. linza, and U. intestinalis**Bay mussel complex: Mytilus galloprovincialis and M. trossulus

Community Study - Wasson et al.

• 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

Invertebrate Study - Alt-Griffith

• Data on abundance of inverts (aquatic and terrestrial)


– MDS (graph)

– ANOSIM (table):

Pairwise Tests R SignificanceGroups Statistic LevelFULL, MUTED 0.067 0.322FULL, MINIMAL 0.243 0.009MUTED, MINIMAL 0.478 0.012

Invertebrate Study - Alt-GriffithTransform: Fourth rootResemblance: S17 Bray Curtis similarity


Old Mouth

Campagna

Coyote

Dominic's

Estrada

Hidden

Hudson

Hummingbird

N Harbor

Kirby

Five Fingers S Azevedo

Moro Cojo Bridge

M Azevedo

MLML Marsh

Packard Main

Porter-BlohmStruve

Crazy Cow

WhistlestopYampah

2D Stress: 0.2


Estuarine amphipod Estuar. amphipod Water boatmenBeach hopper Jap. mud snail Estuar. amphipodAmethyst gem clam Brachyceran fliesMussel shrimp/ostracods SpidersSpiders Brine fliesShore bugs Mussel shrimp/ostracodsJapanese mud snail Calif. Assiminea snail

Invertebrate Study - Alt-Griffith

• Data on average abundance of shorebirds• Visual surveys of 17 sites throughout Elkhorn

Slough• Multiple surveys conducted during spring, fall, and

winter (1999-2000)• Sarah Connors

Shorebird Study - Connors

• Data on abundance of shorebirds


– MDS (graph)

– ANOSIM (table):

Pairwise Tests R SignificanceGroups Statistic LevelFULL, MUTED 0.424 0.121FULL, MINIMAL 0.796 0.001MUTED, MINIMAL 0 0.476



ES-AES-BES-CES-D

ES-EN Harbor

Old Mouth

N Strawberry

N Marsh

EstradaS Marsh

Five Fingers

W Salt ponds

E Salt ponds

Moro CojoSalinas River

Porter-Blohm

2D Stress: 0.04



Dowitcher Willet

Least sandpiper Least sandpiper Black-necked stiltWestern sandpiper Western sandpiper Least sandpiperWillet Dunlin American avocetMarbled godwit Marbled godwit Western sandpiperDunlin Dowitcher Dowitcher

Black-bellied plover


• 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

Marsh Plant Study - Wasson +Woolfolk

• Data on marsh plant relative abundance


– MDS (graph)

– ANOSIM (table):

Pairwise Tests R SignificanceGroups Statistic LevelFULL, MUTED 0.625 0.029FULL, MINIMAL 0.01 0.486MUTED, MINIMAL 0.354 0.114

Marsh Plant Study - Wasson +WoolfolkTransform: Square rootResemblance: S17 Bray Curtis similarity


Azevedo Pen

Coyote

MLML Marsh

Yampah

N Azevedo

N Marsh

Whistlestop

Old Mouth

Porter-Blohm

Estrada

Crazy Cow

Struve

2D Stress: 0.12

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

EcotoneWidth (cm)

FULL MUTED MINIMAL0

100

200

300

400

500

600

700

800

900

1000



Pickleweed Pickleweed Pickleweed

Alkali heath Jointed charlock/ Wild radish

Saltgrass

Saltgrass Unidentified fescue

Fleshy jaumea Soft chess


Fish and crab study Community study

Invertebrate study

3 studies found significant differences in assemblage/community structure between minimal flow and

both muted/full regimes


Coyote

Hudson

Hummingbird

Kirby

Packard Main

S Marsh

Old MouthEstrada

Hidden

M Azevedo

N Marsh

N Strawberry


Packard Pond

Porter-Blohm

S Azevedo

L Moro Cojo

Struve

2D Stress: 0.09 FLOWFULLMUTEDMINIMAL

L Moro Cojo

Moro Cojo Railroad

Struve

S Harbor

N Harbor

Old Mouth

Porter-Blohm

S Azevedo

Whistlestop

Hidden

N MarshN Marsh Exit

N Azevedo

KirbyHudsons

2D Stress: 0.1


Old Mouth

Campagna

Coyote

Dominic's

Estrada

Hidden

Hudson

Hummingbird

N Harbor

Kirby

Five Fingers S Azevedo

Moro Cojo Bridge

M Azevedo

MLML Marsh

Packard Main

Porter-BlohmStruve

Crazy Cow

WhistlestopYampah

2D Stress: 0.2

1 study found significant differences in assemblage structure between full flow and minimal flow regimes only

Shorebird study

Marsh plant study

1 study found significant differences in assemblage structure only between full flow and muted flow regimes


ES-AES-BES-CES-D

ES-EN Harbor

Old Mouth

N Strawberry

N Marsh

EstradaS Marsh

Five Fingers

W Salt ponds

E Salt ponds

Moro CojoSalinas River

Porter-Blohm

2D Stress: 0.04


Azevedo Pen

Coyote

MLML Marsh

Yampah

N Azevedo

N Marsh

Whistlestop

Old Mouth

Porter-Blohm

Estrada

Crazy Cow

Struve

2D Stress: 0.12

02468

10121416

0

10

20

30

40

50

0

10

20

30

40

50

60

Invertebrates

1° Producers

Fishes

FULL MUTED MINIMAL

Species Richness(# spp / regime)

Freshwater/Terrestrial NON-NATIVE

Freshwater/Terrestrial NATIVE

Estuarine NON-NATIVE

Estuarine NATIVE

Marine NON-NATIVE

Marine NATIVE05

10152025303540

Birds

FULL MUTED MINIMAL

FULL MUTED MINIMAL

FULL MUTED MINIMAL

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

Roadmap to talk




Potential mechanisms behind ecological patterns across flow regimes

Structures can alter conditions upstreame.g. physical, chemical

Structures can restrict transport of organismse.g. behavior, mobility, size

A B C

C D E

X

X

A B C

C D E

AB

DE

XX

XX

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

-1.0 -0.5 0.0 0.5 1.0Correlation with MDS 1

-1.0

-0.5

0.0

0.5

1.0

Correlation with

MDS 2

DO

Salinity (dry)

NH3

NOX

pH

PO4

Salinity (rainy)Temperature

Tidal Range

Turbidity_

MDS 1

MDS2

NormaliseResemblance: D1 Euclidean distance


Old Mouth

Hudsons

Kirby

Crazy Cow

L Moro Cojo

M Azevedo

N Harbor

N Marsh

Porter

Reserve BridgeSkippers

S Azevedo

S Harbor

S Marsh

Struve

2D Stress: 0.08

Roadmap to talk




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

TIDAL RANGE (in cm, measured on a spring tide)

0 2 7 45 88

South Azevedo Struve Pond North Marsh Whistlestop Bennett Slough

Restricted flow sites at Elkhorn Slough span a continuum of tidal exchange


0 2 7 45 88

threatened brackish speciese.g. tidewater goby, Tryonia snail

key marine visitors e.g. migratory shorebirds, commercial fish nurseries

Also a continuum of habitat use by potential conservation targets



0 2 7 45 88

Low tidal exhangeLimited flushing can result in poor water quality

And a continuum of ecological concerns

, and these habitats have limited connectivity with the estuarine network, but habitats are not subject to tidal erosion

High tidal exchangeGood flushing improves water quality, and there is good connectivity, but some habitats are subject to tidal erosion



0 2 7 45 88


Do we want representation of all parts of this continuum for the future?In what proportion?



0 2 7 45 88


Straw man for even representation of entire spectrum



0 2 7 45 88


Straw man for “Goldilocks” model: aim for middle range, with no representation of extremes


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?

the influence of varying tidal exchange on the...

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