Predictions for habitats, water quality, and biological...

PARSONS SILL PROJECT

Predictions for habitats, water quality, and biological communities

Draft 19 September 2009

E. Van Dyke, B. Hughes, J. Haskins, K. Wasson

PARSONS SILL PROJECT

How will conditions change inside the Parsons complex?

How will they change in the rest of the Slough?

GOALS FOR THIS PRESENTATION

Summarize extensive databases that ESNERR scientists have access to, making information available to everybody

Paint picture of future of Parsons to avoid surprises later

LATE MORNING

INFORMATION FLOW:From us to you: we summarize what we’ve learned from data & expert panels

BREADTH VS. DEPTH: Focus on breadth: a little bit about a lot of parameters

AFTERNOON

INFORMATION FLOW:From you to us: you prioritize management targets for this project

BREADTH VS. DEPTH: Focus on depth: a tiny subset of the parameters to be used as triggers for management action

PREDICTIONS SUMMARY

LEGEND FOR HANDOUT

⇑ Increase

⇓ Decrease

⇔ No change

⇜⇝Change in community structure (abundance of group remains similar, but abundance of some species changes)

PREDICTIONS SUMMARY

NOTESPredicted increases or decreases are RELATIVE to no action scenario (no sill at Parsons).Predictions apply to approximately the first five years after construction (in some cases effects may be immediate, in others they may take a few years to appear). We have not characterized the temporary impacts of construction itself.Increases or decreases are only indicated if they would represent a statistically significant difference (effects detectable on background of interannual variance).

PREDICTIONS SUMMARY

NOTES

Black arrows are predictions where the experts indicated there was a relatively high level of certainty, based on existing comparative data or published literature.Gray arrows are predictions where the experts indicated there was a relatively low level of certainty, due to limited data on the parameter or confounding factors.

PREDICTIONS SUMMARY

NOTES

Note that increases and decreases do not represent value judgment, just numeric changes (e.g. salt marsh increase is desirable but hypoxia increase is undesirable).

Each row does not have equal ecological or conservation importance in this system; equal space on the chart does not imply a value judgment.

PREDICTIONS SUMMARY

PREDICTIONS FOR INSIDE PARSONS VS. REST OF ESTUARY

Where no explanation is provided (BLANK BOX), the assumption is that changes to Parsons do not have measurable effects on the rest of the estuary.Predictions for effects on the whole estuary (Parsons plus rest) have not been made yet due to difficulty in defining relative importance of Parsons, but can be pursued with expert panels if requested by stakeholders.

PARSONS SILL PREDICTED CHANGES

1) Habitat extent and distribution2) Water quality and eutrophication3) Biological communities

HABITAT PREDICTIONSData sources

WATER LEVELS– Moffatt and Nichol / PWA modeling results– ESNERR / NOAA CO-OPS tide station data

(Elkhorn Slough and Monterey)

HABITATS– April 2005 NPS / Airborne1 LiDAR data– 2005 ESNERR / DFG aerial photography

HABITAT PREDICTIONSGeneral approach

WATER LEVELS– Extracted tidal datums from Dec. 2005 model results; adjusted to full tidal epoch– Also estimated 40% and 60% tidal ranges

HABITATS–Established habitat tidal elevation ranges from aerial imagery–Classified habitats to modeled datums

NAV

D88

(fee

t)

MHHW

MHW

MLLW

TIDAL RANGE without sillUnrestricted flow, mixed semidiurnal tidal cycleModel results (inside Parsons) match observed tides (main channel)

NAV

D88

(fee

t)

MHHW

MHW

MLLW

TIDAL RANGE with 25’ sillRestricted to 50% range, diurnal tidal cycleMHW-MHHW range shifted down; MLW-MHW range narrow

HABITAT DISTRIBUTIONWithout sill (unrestricted) With 25’ sill (50% range)

NAV

D88

(fee

t)

longer lag higher flowresistance

MODEL SENSITIVITYMinor variations in sill structure produce different tidal regimesLower amplitude due to increased tide lag and flow resistance through sill

SILL VARIATIONSWith sill (50% tidal range) With sill (60% tidal range)

0

50

100

150

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250

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350

400

unrestricted sill (50% tidal range) sill (60% tidal range)

Acr

es

subtidal intertidal mud marsh upland

HABITAT PREDICTIONS

HABITAT SUMMARY

PREDICTIONS FOR PARSONS WITH SILL

Salt marsh (intertidal) ⇑

highest elevation mudflats convert to marsh due to lowered tidal frame

Mudflat (intertidal) ⇓

higher mudflats convert to marsh, lower mudflats convert to subtidal

Subtidal ⇑lower elevation mudflats no longer exposed at low tide

HABITAT SUMMARY

PREDICTIONS FOR REST OF ESTUARY AFTER PARSONS SILL IS COMPLETED

Salt marsh (intertidal) ⇔

rate of marsh loss may slow in upper estuary due to improved drainage, but cause of marsh loss is poorly understood

Mudflat (intertidal) ⇔Subtidal ⇔

WATER QUALITY PREDICTIONSData sources

ESNERR – Continuous in-situ monitoring at 4 stations, initiated in 1995; monthly volunteer sampling at 24 stations, initiated in 1988; additional targeted sampling in 2008-9 as a part of eutrophication study

LOBO – Continuous in-situ monitoring at 4 stations, initiated in 2004

WATER QUALITY PREDICTIONSGeneral ApproachComparison of full vs. muted tidal exchange sites

In particular, comparison of Parsons complex to Whistlestop Lagoon, Bennett Slough and North Azevedo Pond

No muted site is a perfect proxy for future conditions at Parsons, but examining muted sites informs prediction about DIRECTION of likely changes

Bennett Slough

59%

20%

25%16%

43%

% of full tidal range shown in purple

EUTROPHICATION: temperatureMuted sites have higher average temperatures than full tidal sites

EUTROPHICATION: macroalgaeUlva often nutrient limited, enhanced by agricultural inputs;Algal mats can affect dissolved oxygen and benthic communities

EUTROPHICATION: macroalgaeFloating mats present in restricted but not full tidal exchange

EUTROPHICATION: water column chlorophyllAffects dissolved oxygen and light availability in the water column

EUTROPHICATION: chlorophyll aConcentrations not significantly different in full vs. muted sites

Hypereutrophic

Eutrophic

EUTROPHICATION: sediment anoxiaAffects benthic invertebrate communities and feeding by other animals

EUTROPHICATION: sediment anoxiaA much narrower layer at the top of the mud is well oxygenated at muted vs. full tidal sites

EUTROPHICATION: dissolved oxygen/pHGreater variation with less tidal exchange

a

b

b

a

b

b

EUTROPHICATION: dissolved oxygenOf ecological concern because distribution, abundance, and behavior of most estuarine organisms is affected by oxygen concentrations

Low oxygen conditions are typical at nighttime in nutrient-enriched systems

EUTROPHICATION: dissolved oxygenDO fluctuation much higher in tidally restricted than fully tidal sites but whistlestop

doesn’t go below that of South Marsh

DO comparison SM and Whistlestop Aug 2008

0

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8/12/08 8/13/08 8/14/08 8/15/08 8/16/08 8/17/08 8/18/08 8/19/08 8/20/08 8/21/08 8/22/08 8/23/08 8/24/08 8/25/08 8/26/08

Date

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whistlestop DOSM DO %

EUTROPHICATION: dissolved oxygenDO fluctuation much higher in tidally restricted than fully tidal sites and Bennet Slough

West and Vierra Mouth

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4001

1.54

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ODO% BSWDO% VM

EUTROPHICATION: dissolved oxygenShows very clear relationship with tidal range: the lower the tidal range and depth, the more hypoxia

EUTROPHICATION: dissolved oxygenShows very clear relationship with tidal range: the lower the tidal range and depth, the more hypoxia

Tidal range at sill’s maximum restriction

Tidal range at sill’s minimum restriction

WATER QUALITY AND EUTROPHICATION SUMMARY


Macroalgae(Ulva) ⇑

intertidal cover may decrease but subtidal and floating cover is likely to increase, leading to a net increase

Hypoxia (low oxygen) ⇑

based on regression analysis of tidal range vs. hypoxia duration for Slough sites; in addition to increase in hypoxia, there will be greater daily variation in oxygen levels

WATER QUALITY AND EUTROPHICATION SUMMARY


Temperature ⇑muted sites have greater variance in temperature than fully tidal ones, and on average are about 1C warmer

Chlorophyll ⇔no significant difference between existing muted vs. fully tidal sites

Sediment anoxia ⇑a significantly greater proportion of surface sediments are anoxic in muted vs. fully tidal sites (depth to anoxia is significantly shallower)

WATER QUALITY AND EUTROPHICATION


Macroalgae (Ulva) ⇔Hypoxia ⇔Temperature ⇔Salinity ⇔Chlorophyll ⇔Sediment anoxia ⇔

BIOLOGICAL PREDICTIONSGoalGet everyone on same page about existing knowledge and plausible direction of changes with sill

Lots of species/groups, so this will be fast tour of highlights

BIOLOGICAL PREDICTIONSGeneral Approach

Literature review and synthesis

Input from expert panels for each taxon

ESNERR monitoring dataDatasets from other researchers

Above used for comparison of current Parsons to sites with muted tidal exchange

Bennett Slough

59%

20%

25%16%

43%

% of full tidal range shown in purple

SALT MARSHOf conservation concern at Elkhorn because of extensive documented losses over past century, including of dramatic losses within Parsons complex due to diking, draining and subsidence prior to return of tidal exchange

Important for food web support, refuge for roosting birds, and for improving water quality

PICKLEWEEDProjections made by Van Dyke based on elevation and tidal range indicate significant increase in salt marsh after sill is implemented

Pickleweed dominates marsh from about MHW to MHHW and most of increase of salt marsh habitat will be a result of increased pickleweed abundance

SALT MARSH ECOTONEHigh marsh-upland transition zone•Very narrow and fragile zone hosts suite of endemic estuarine plant species•Marsh diversity is important for ecosystem function

SALT MARSH ECOTONEWoolfolk & Wasson

• Data on ecotone extent and plant communities

• Sampled 4 muted and 6 fully tidal sites in 2005

SALT MARSH ECOTONE•Plant communities differ significantly between full and muted tidal conditions•Muting Parsons is likely to change plant communities, but muted sites are variable so exact predictions cannot be made

tidal exchangefullmutedAzevedo Penin

Coyote

Five Fingers

Moss Landing

Yampah

PicNPull

North Azevedo Pon

Bennett

North Marsh

Whisltestop

2D Stress: 0.08

SALT MARSH ECOTONE•Of native marsh plants, pickleweed accounts for much more cover in muted than fully tidal sites•Salt grass and alkali heath are (mostly) absent from muted tidal sites

Atriplex triangularis spearscale 0.4 4.2

Cuscuta salina salt marsh dodder 0.3 0

Distichlis spicata salt grass 17.8 0

Frankenia salina alkali heath 17.3 0

Jaumea carnosa fleshy jaumea 7.9 9.5

Salicornia virginica pickleweed 34.4 64.7

FULL MUTED

SALT MARSH ECOTONE SUMMARY


Pickleweed ⇑same prediction as salt marsh habitat extent above

Other native marsh plants ⇓

existing muted sites at Elkhorn Slough have significantly decreased native marsh plant diversity due to decreased abundance of salt grass and alkaliheath

SALT MARSH ECOTONE SUMMARY


Pickleweed ⇔same prediction as salt marsh habitat extent above

Other native marsh plants ⇔

EELGRASSImportant estuarine conservation target because of rarity and effects on estuarine processes and diversity

EELGRASSPredictions for large-scale management alternatives developed by Sherry Palacios and expert panel using published literature on eelgrass and Elkhorn data

EELGRASSEelgrass beds have been gradually expanding in last decades, but are limited to lower Slough, apparently due to unfavorable conditions such as supersaturation with oxygen or high phytoplankton concentrations in upper estuary and Parsons complex

EELGRASS SUMMARY


⇔eelgrass is absent from Parsons now and is predicted to remain absent

EELGRASS SUMMARY


⇑decreased tidal velocities in the lower estuary could benefit eelgrass by increasing sediment deposition and plant stress

SMALL BENTHIC INVERTEBRATES(crustaceans, worms, small clams, etc.)

Important for estuarine food webs (feed birds and fish) and good indicators of ecosystem health

Micrographs from K. Heiman

SMALL BENTHIC INVERTEBRATES(crustaceans, worms, small clams, etc.)

Studied by MLML Benthic Lab Team (Oliver, Hammerstrom, Oakden, Slattery, Kim)

Sampled in 2003 (mostly main channel) and 2007-8 (mostly peripheral sites)

Coffee can cores of mud, sieved for invertebrates; identified and counted

SMALL BENTHIC INVERTEBRATES•Communities differ significantly between full and muted tidal conditions•However, there is overlap between some sites

Tidal ExchangeFullMuted

2D Stress: 0.21

SMALL BENTHIC INVERTEBRATES•Parsons complex sites are more similar to existing muted sites than most main channel sites (here lumped as ES)•Muted sites are quite variable, so it is hard to predict exactly how Parsons communities would change with a sill


ES

Five FingersNorth Harbor

Old Salinas

Parsons Slough

Pick N Pull

Rookery Lagoon

South Marsh

Bennett West

North Azevedo

North Marsh

Whistlestop

2D Stress: 0.1

SMALL BENTHIC INVERTEBRATES•Species diversity at Parsons complex sites is comparable to that of muted sites, so no significant loss of diversity expected with sill

MUTED tidal exchange

FULL tidal exchange

SMALL BENTHIC INVERTEBRATES•Total abundance varies a lot across seasons and sites, so it is hard to make rigorous predictions•Whistlestop appears to have lower total abundance than current Parsons complex, but other muted sites have similar abundance

MUTED tidal exchange

FULL tidal exchange

SMALL BENTHIC INVERTS SUMMARY


⇜⇝community composition differs significantly between existing muted and fully tidal sites

⇓some muted tidal sites (e.g. Whistlestop) have significantly lower total abundance than do many fully tidal sites

SMALL BENTHIC INVERTS SUMMARY


⇔

LARGE BENTHIC INVERTEBRATES(big clams, worms, shrimp)

Important for estuarine food webs and harvested by recreational users

Clams common in middens from Parsons complex

PACIFIC GAPER CLAMG. A. Anderson

FAT INNKEEPER WORMG. A. Anderson

BAY GHOST SHRIMPw. Jorgensen

LARGE BENTHIC INVERTEBRATES(big clams, worms, shrimp)Surveyed by ESNERR & MBNMS team in rapid assessments accompanying bank erosion study

Conducted literature review and wrote key species report reviewed by expert panel

LARGE BENTHIC INVERTEBRATES•Communities differ significantly between full and muted tidal conditions


2D Stress: 0.15

SMALL BENTHIC INVERTEBRATES•Parsons complex sites currently show lots of overlap with upper main channel sites•With sill, they will likely become less like upper main channel, more like muted sites….but which one? Lots of variability

RegionLower main channelUpper main channelSouth MarshFive FingersRookery LagoonWhistlestopNorth MarshHidden PondBennett WestAzevedo North

2D Stress: 0.15

LARGE BENTHIC INVERTEBRATES

More common in…..

FULL TIDAL EXCHANGE MUTED TIDAL EXCHANGEGaper clam Littleneck clamButter clam Jackknife clamFat innkeeper worm Batillaria snailGhost shrimp

Expect these to get more Expect these to get morerare in Parsons after sill? common in Parsons after sill?

LARGE BENTHIC INVERTS SUMMARY


⇜⇝community composition differs significantly between existing muted and fully tidal sites

⇑some species, esp. Batillaria snails, jackknife clams, and littleneck clams may increase (based on data from other muted sites)

⇓some species, esp. fat innkeeper worms and ghost shrimp may decrease

LARGE BENTHIC INVERTS SUMMARY


⇔

OLYMPIA OYSTERS

•Improve water quality

•Increase species richness of invertebrates and fish

•Have undergone dramatic declines at Elkhorn and whole Pacific coast

Painting by Cory and Catska Ench, 2003From Journal of Shellfish Research March 2009

OLYMPIA OYSTERSSurveyed by ESNERR team

Literature review and key species report reviewed by expert panel

OLYMPIA OYSTERSResults of investigation at Elkhorn relevant to Parsons project

Oysters are not common in strongly marine-influenced parts of the estuary near the mouth, perhaps due to lack of larval retention or predation by marine species; sill may improve larval retention.

Oysters were present at Parsons prehistorically – midden data.

Oysters are abundant in two muted tidal exchange sites (Whistlestop, North Azevedo), but rare or absent in three others (Hidden Pond, North Marsh, Bennett Slough West).

Oysters recruit abundantly at North Azevedo, but do not survive to large size, undergoing mass die-offs, probably related to shallow water depth (and associated hypoxia or high temperature).

OLYMPIA OYSTERSResults of investigation at Elkhorn relevant to Parsons project

Oysters are found between about -1 ft below MLLW and +2 ft above MLLW at Elkhorn. At the lower end of this range they are heavily overgrown by non-native sponges, bryozoans and tunicates.

In the upper estuary, number of oysters at a site is directly correlated with amount of hard substrates large enough to avoid burial that are present between MLLW and two feet above.

Restriction of tidal range will lead to initial mortality, because some current reefs will be too high (dessicate) or too low (subtidal, fouled by non-natives) in new tidal frame

This effect can be mitigated with strategic addition of hard substrates to appropriate tidal elevations

OLYMPIA OYSTERSTargeted restoration by addition of hard substrates can further increase numbers

Pilot restoration experiments already underway in Parsons complex

OYSTER SUMMARY


⇔

initially oyster mortality will occur due to changes in tidal regime, but long term recruitment and survival rates may increase, so overall prediction uncertain

OYSTER SUMMARY


⇔

NEKTON= Fish & Crabs

Important for estuarine food webs, and for recreational and commercial fishing

Lots of great sampling by various researchers in past, but focused on fully tidal areas

Ritter & Preisler dataset is only one with similar sampling effort across multiple fully tidal and muted tidal sites

NEKTONRitter & 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 to sample fishes and crabs

NEKTON•Nekton communities in South Marsh and adjacent main channel sites are similar to each other•Bennett is also fairly similar•Other muted sites are each distinct

Tidal regime1- full2-muted

CoyoteHudson

Hummingbird

Kirby

Packard

South Marsh

Bennett

Hidden

North Marsh

Whistlestop

2D Stress: 0.08

NEKTON

Two species were found to be significantly more abundant in muted tidal exchange (none were found to be more abundant in full)

•Topsmelt•Longjaw mudsucker

NEKTON SUMMARY


⇜⇝

existing muted sites have significantly different communities than fully tidal sites; in particular topsmelt and mudsuckers are predicted to become more abundant

NEKTON SUMMARY


⇔

FLATFISHEnglish solestarry flounderCalifornia Halibutspeckled sanddabdiamond turbot

Considered key species for Elkhorn Slough due to popularity with recreational fishers within Elkhorn and importance for fisheries in Monterey Bay

Team from Harvey & Associates (Sharon Kramer, Jenn Brown, Peter Nelson) conducted review and made predictions for effects of reduced tidal exchange, reviewed by expert panel

Courtesy of S. Anderson

FLATFISH

HIGHLIGHTS FROM KEY SPECIES REPORTMuted tidal exchange is generally expected to be less favorable for flatfishFlatfish generally more common in more marine-influenced portions of estuaries, because of better prey base and connectivity with ocean

Abundance depends on conditionsFlatfish should continue to occur in Parsons complex so long as sill doesn’t limit movement, hypoxia doesn’t increase substantially, and algal mats don’t accumulate on bottom interfering with foraging

FLATFISH SUMMARY


⇓flatfish generally favor more marine influenced conditions and are rarer in muted tidal exchange sites, but data for Elkhorn muted sites are limited

FLATFISH SUMMARY


⇔

ELASMOBRANCHS= Sharks & rays

Rely on shallow coastal habitats as nurseries

Important consumers of large molluscs, worms, crabs

Popular with public and fished commercially and recreationally

ELASMOBRANCHS

Lots of past and current studies in Sloughesp. by MLML researchers and PSRF

Various studies suggest importance of Parsons complex in larger Slough system – shallow mudflats with favorable prey for foraging, temperature for growth and nurseries, etc.

Historical numbers in Parsons complex (pre-1850) probably quite low, because only limited mudflats and channels were present in marsh-dominated habitat

Very few studies consistently comparing full tidal exchange to muted, so hard to make predictions for Parsons sill

ELASMOBRANCHSEmily Owens 2005 Senior Thesis

Sampled 3 nearby sites in Parsons complex: 2 with full tidal exchange (Rookery lagoon, South Marsh) and 1 with muted tidal exchange (Whistlestop Lagoon)

Equal sampling effort per site:50 m tangle net deployed for 3 hrs on 4 different days at each site

Assistance by PSRF, Matt Gardner, Rikke Preisler, & many volunteers

ELASMOBRANCHSLower total abundance in Whistlestop

south marsh whistlestop lagoon heron rookery

Series1 28 15 24

0

5

10

15

20

25

30

35

# E

lasm

obra

nchs

Total Elasmobranch Abundance

ELASMOBRANCHSOwens 2005

Community composition varies significantly across sites

Whistlestop has many fewer leopard sharks than Rookery Lagoon, many few bat rays than South Marsh, and fewer guitarfish than both

0

2

4

6

8

10

12

14

16

leopard shark guitarfish bat ray thornback ray

# In

divi

dual

s

Species

South Marsh Abundance

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Heron Rookery Abundance

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ELASMOBRANCHSAaron Carlisle 2007 M.S. ThesisRadiotagged leopard sharks

Found Parsons complex used throughout year, but most heavily from April– August

Some portions much more heavily used than others; no tagged sharks entered Whistlestop Lagoon

Tidal elevations around MLLW used most heavily presumably due to prey abundance

ELASMOBRANCHSAaron Carlisle 2007 M.S. ThesisConducted calculations that acreage of most heavily used habitat by tidal elevation would be reduced to about 70% of what it is currently with fairly restrictive setting of Parsons sill

Although lower intertidal habitats will decrease, the impact of the concurrent increase in shallow subtidal habitats is unknown, but potentially may provide leopard sharks with suitable habitat

ELASMOBRANCH SUMMARY


⇓optimal foraging habitat and water quality may decrease, but little is known about shark and ray abundance in muted tidal sites nor about response of preferred prey

ELASMOBRANCH SUMMARY


⇔

WATERBIRDSEstuary is important stopover for migratory shorebirds

Shorebirds and other waterbirds are valued by birdwatchers and other recreational visitors

WATER BIRDSMonitored by B. Ramer, S. Connors, G. Page, and many ESNERR volunteers

Literature review, synthesis of Elkhorn data, and predictions for Elkhorn made by expert panel

SHOREBIRDS

Fully tidal sites support greater bird numbers than muted sites at low tide due to more extensive mudflats and more abundant prey

At high tide, muted sites with very shallow water are used for roosting and some foraging

Parsons currently supports high numbers of various shorebird species (due to extensive intertidal mudflats) but not very high densities (suggesting limited food resources)

Historically, Parsons would not have supported very high numbers of shorebirds due to very limited extent of intertidal mudflats

OTHER WATERBIRDS

Densities of waders (herons, egrets) and waterfowl (esp. Mallards, Gadwall) are often high at muted vs. fully tidal sites

0

20

40

60

80

100

120

2007 2008 2009

0

500

1000

1500

2000

2500

2007 2008 2009

WATERBIRDSComparison of paired muted and fully tidal sites shows that waterfowl are more common in muted, shorebirds in full tidal exchange

North HarborBennett

North HarborBennett

Waterfowl abundance Shorebird abundance

WATERBIRD SUMMARY


Shorebirds ⇓

decreased mudflat area would probably translate to decreased total numbers of shorebirds using the area at low tide, though it might be used as a refuge at high tide

Other waterbirds ⇑

waterfowl and wading birds are typically more abundant in muted than fully tidal sites

WATERBIRD SUMMARY


Shorebirds ⇔Other waterbirds ⇔

MARINE MAMMALSUse the estuary for foraging, resting, reproduction and raising young

Important for humans: attract recreational visitors who support local businesses

MARINE MAMMALS

Monitored in the Slough by Okeanis team (Maldini, Eby, Scoles, Cotter & many volunteers), Slough Safari (Gideon) and Monterey Bay Aquarium

Focused studies by Harvey (MLML) and Estes (UCSC) labs

Biannual aerial surveys by USGS

Elkhorn data synthesized with literature review as a part of key species report series, providing broad predictions about affects of large-scale management alternatives

HARBOR SEALS•Use estuary for limited foraging, for resting, and pupping: the latter is most important/vulnerable function, occurs in early spring•Use Parsons complex for resting and pupping , especially intertidal mudflat “islands” along old levies•Almost never found in muted tidal sites such as Bennett Slough (but culverts may be more difficult to navigate than sill)

SEA OTTERS•Highest numbers in harbor area due to food resources (crabs, clams and worms in lower estuary, and proximity to Monterey Bay)•Eelgrass beds at Seal Bend primarily used as nursery for mothers and pups•Tidal creeks are also frequented, but purpose of use unknown•Low numbers in Parsons complex - maybe be used for limited foraging or male territories•Single individuals sometimes occupy muted sites for months (Whistlestop, Bennett Slough)

MARINE MAMMAL SUMMARY


Harbor seals ⇓

fewer harbor seals might use area for hauling out if sill provides barrier to navigation or if new mudflat distribution is less favorable

Sea otters ⇔

low numbers of sea otters use Parsons currently, and use muted sites such as Whistlestop or Bennett, so no significant change is anticipated

MARINE MAMMAL SUMMARY


Harbor seals ⇔

Sea otters ⇔

In Parsons Slough

In rest of estuary

Pickleweed ⇑ ⇔Other native marsh plants ⇓ ⇔Eelgrass ⇔ ⇑Small benthic invertebrates ⇜⇝ ⇔Large benthic invertebrates ⇜⇝ ⇔Oysters ⇔ ⇔Nekton community ⇜⇝ ⇔Flatfish ⇓ ⇔Sharks and Rays ⇓ ⇔Shorebirds ⇓ ⇔Other waterbirds ⇑ ⇔Harbor seals ⇓ ⇔Sea otters ⇔ ⇔

BIOLOGICAL PREDICTIONS: SUMMARY

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