ESCI 491: Eelgrass community function and

response to sulfideFish Team: Brian Maskal, Mattie Michalek, Elizabeth Orta

Photosynthesis and alkalinity team: Jennifer Dunham and Chloe NelsonSulfide and eelgrass distribution team: Angela Gossom, Sean Wu, Matthew Kneipp

Sulfur in leaf and root team: Jennifer Hartke, Rachel Blyth

Eelgrass as fish habitat

Questions: • Which species of fish depend upon

eelgrass habitat?• Do juvenile salmon use eelgrass as

habitat?Methodology:• Sample Site: Mud Bay, Bellingham, WA• Seined in eelgrass and non-eelgrass sites

Fish species observed

Steelhead Trout Coho Salmon Shiner Perch Spine Stickleback

Tidepool Sculpins Starry Flounder Snake Prickle-back Bay Pipefish

Cabazone Sculpins Crabs Pacific Staghorn Hermit Crabs

Pacific Staghorn Sculpin Shrimp English Sole Fish

Juvenile salmonids• Eelgrass site 1: 1 Coho• Eelgrass site 2: 1 Coho• Non-eelgrass site 1: 1 Steelhead• Non-eelgrass site 2 (in cove): 0 salmonids

Salmonids found in eelgrass and non-eelgrass habitats.

Coho only found in eelgrass bedsOn average, more species and more individual fish

observed in eelgrass bedsVery small sample size

Eelgrass photosynthesis, oxygen, and alkalinity production

Questions:• What is the rate of net

photosynthesis in eelgrass?• How does the presence of eelgrass

affect alkalinity production?Methods• Incubated sediment cores with and

without eelgrass• Measured dissolved oxygen, DIC, and

alkalinity over time

Observations – Dissolved oxygen increased

Eelgrass Sediment

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00

5

10

15

20

25

30

E1E2E3E4

Incubation time (d)

Diss

olve

d ox

ygen

(mg/

l)

0.00.20.40.60.81.01.21.41.61.82.002468

10121416

C1C2C3C4

Incubation time (d)

Diss

olve

d ox

ygen

(mg/

l)

Day Night Day Night

Observations – DIC decreased

Eelgrass Sediment

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01000

1200

1400

1600

1800

2000

2200

C1C2C3C4

Incubation time (d)

DIC

(μM

)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01000

1200

1400

1600

1800

2000

2200

E1E2E3E4

Incubation time (d)

DIC

(μM

)

Net photosynthesis rate: 3 mg C shoot-1 d-1, or 0.1 g C m-2 d-1

Day Night Day Night

Observations – Alkalinity flux

Not much change in alkalinity

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01800

1850

1900

1950

2000

2050

2100

2150

2200

C1

C2

E1

E3

Incubation time (d)

Alka

linity

(μm

ol k

g-1)

Day Night

Relationship between eelgrass density and pore water sulfide

Questions:• How does eelgrass density vary with

pore water sulfide concentration?Methods• Sampled eelgrass in two locations:

Padilla Bay and Hood Canal• Measured pore water sulfide: Used

sippers to sample, preserved samples in SAOB, measured sulfide using an ion-selective electrode

Results – Eelgrass vs. sulfide inventory Padilla Bay

Results – Eelgrass vs. sulfide inventory Hood Canal

Sulfur in eelgrass leaves and roots

Questions:• Does S in eelgrass reflect pore

water sulfide, eelgrass density, or water-column oxygen?

Methods:• Collected eelgrass leaves and

roots from Padilla Bay and Hood Canal• Measured S using an elemental

analyze

Results: Average %S and eelgrass density

Results: %S in leaves vs. pore water sulfide

0 0.05 0.1 0.15 0.2 0.250

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Hood Canal

padilla Bay

Pore water sulfide at 3 cm (µM)

Sulfu

r in

leav

es (%

)

Not plotted – one data point from Hood Canal at 0.9 %S

0.9%

Results: Eelgrass density vs. %S in leaves

Summary and interesting observations• Lots of fish in the Chuckanut Bay eelgrass beds but few salmonids• Rates of photosynthesis derived from DIC measurements similar to

rates determined by 14C.• Eelgrass does not have a large affect on alkalinity production• Eelgrass density does not vary with pore water sulfide, nor does

sulfide intrusion into leaves in Padilla Bay and Hood Canal• One shoot in Hood Canal had very high levels of S in leaves – What

conditions lead to sulfide intrusion?