ESCI 491: Eelgrass community
function and response to sulfide
Fish Team: Brian Maskal, Mattie Michalek, Elizabeth Orta
Photosynthesis and alkalinity team: Jennifer Dunham and Chloe Nelson
Sulfide 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 beds
On average, more species and more individual fish
observed in eelgrass beds
Very 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
30
Sediment
Day Night
25
E1
20
E2
15
E3
10
E4
5
0
0.0
1.0
Incubation time (d)
2.0
Dissolved oxygen (mg/l)
Dissolved oxygen (mg/l)
Eelgrass
Day Night
16
14
12
10
8
6
4
2
0
C1
C2
C3
C4
0.0
1.0
Incubation time (d)
2.0
Observations – DIC decreased
Eelgrass
2200
Sediment
2200
Day Night
2000
E1
1800
E2
1600
E3
1400
E4
1200
1000
DIC (μM)
DIC (μM)
2000
Day Night
C1
1800
C2
1600
C3
1400
C4
1200
1000
0.0
0.5
1.0
1.5
Incubation time (d)
2.0
0.0
1.0
Incubation time (d)
Net photosynthesis rate: 3 mg C shoot-1 d-1, or 0.1 g C m-2 d-1
2.0
Observations – Alkalinity flux
2200
Day
Alkalinity (μmol kg-1)
2150
Night
2100
C1
2050
C2
2000
1950
E1
1900
E3
1850
1800
0.0
0.5
1.0
1.5
Incubation time (d)
Not much change in alkalinity
2.0
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
0.9%
0.4
Sulfur in leaves (%)
0.35
Hood Canal
0.3
padilla Bay
0.25
0.2
0.15
0.1
0.05
0
0
0.05
0.1
0.15
0.2
Pore water sulfide at 3 cm (µM)
0.25
Not plotted – one data point from Hood Canal at 0.9 %S
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?