Restoration Monitoring of Drakes Estero · 2016-12-09 · Drakes Estero is a 2500–acre estuary...
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DISCUSSION/FUTURE EFFORTS Removal of the oyster racks is now ongoing (see photos above) and post-removal monitoring is expected to begin in December 2016. Preliminary monitoring suggests that our pre-restoration monitoring is capturing the variation in the under-rack conditions as it pertains to eelgrass recovery in the former mariculture operation (rack) areas. Non-metric Multi-Dimensional Scaling (NMDS) clusters the quadrats according to similarity in substrate and community composition on the estero floor. NMDS showed the five transect types fell along a continuum of species assemblages with distinct clusters of sites from each type, but a fair amount of overlap (Figure 3) . Eelgrass (Zostera marina) was strongly associated with Control and Sub-surface transects. Major transects were distinct from all the other transects, and were dominated by debris, Dvex and algal communities. INTRODUCTION Drakes Estero is a 2500–acre estuary located in Point Reyes National Seashore. It is a State Marine Conservation Area and the only Federal marine wilderness on the west coast south of Alaska. Several decades of commercial oyster mariculture ceased in 2014, leaving behind extensive infrastructure that harbors non-native species, precludes eelgrass growth, and litters the estero floor. In 2016, NPS began the Drakes Estero Restoration Project to remove this infrastructure and debris composed of five miles (~500 tons) of wooden oyster racks and two-acres of plastic tubes, oyster shell, plastic bags, and other mariculture debris on the estero floor. Outside of the mariculture sites, the estero is dominated by large beds of eelgrass, a foundation species designated as Essential Fish Habitat by the National Marine Fisheries Service (NMFS). To comply with permitting from the California Coastal Commission and NMFS, we are assessing: (1) potential impacts of the removal operations on limited eelgrass already growing within the mariculture operation (oyster rack) areas, (2) the recovery of eelgrass in the mariculture operation areas after restoration, and (3) changes to the abundance of the invasive tunicate, Didemnum vexillum (Dvex), within the estuary. We predict, During the restoration project: 1) there will be very limited short term eelgrass impacts After the restoration project: 2) eelgrass will recover, A) within the rack areas and exceed the required 1.2 : 1 mitigation ratio B) more quickly in minor-moderate debris plots than major debris plots C) more slowly at sub-sediment beam removal sites than those with surface wood 3) there will be a decrease in Dvex cover The findings of pre-restoration monitoring are presented here. Restoration Monitoring of Drakes Estero: Pre-Restoration Assessment of Eelgrass, Marine Debris, and Non-Native Species Amelia Ryan, Sarah Codde, and Ben Becker Point Reyes National Seashore, National Park Service METHODS The effects of restoration and the recovery of eelgrass are being assessed using areal percent cover of the estero floor using 0.25m 2 quadrat at regular intervals along a transect. Percent cover of each species or substrate in each photo is estimated with the assistance of CoralNet (coralnet.ucsd.edu), an online benthic imagery analysis program. Cover will be estimated at least 3 times: • Pre-restoration (<60 days prior to removal) • Post-restoration (<60 days post removal) • Annually post restoration until recovery goals met Different transect types were created to capture both short term impacts from rack and debris removal and long term recovery post restoration. Monitoring Transect Types RESULTS During the pre-restoration monitoring we assessed percent cover of 564 estuary floor quadrats within 54 transects (treatments and controls) for species community assemblage, substrate, and marine debris. White globs of Dvex covering strings of oyster shells Figure 3. NMDS results based on estuary floor cover of 564 quadrats in 54 transects of 5 types: eelgrass bed controls (Control), short-term sub-sediment eelgrass impacts (Sub- surface), short-term surface wood removal impacts (Surface), long-term recovery for sites with no-moderate debris (Min-Mod) and major debris (Major). Ellipses represent standard deviation. Italics represent dominant species/cover types. Figure 4. Distributions for the four cover types within each transect type. Figure 2. Distribution across Drakes Estero of different monitoring survey transect types relative to oyster racks. Figure 1. Project Location Piles of recently removed oyster rack wood (left) and plastic “french tubes” used in mariculture operations removed from the estero floor. Intact eelgrass bed in Drakes Estero Stringing out a transect (left) and preparing to photograph the quadrat on the estero floor (right). Control Sub-surface Surface Min-Mod Major Eelgrass Present? Yes Yes Yes No, but adjacent No Mariculture Debris? None Wooden crossbeams buried in sediment Rack wood fallen on eelgrass, little plastic or shell No to moderate debris and shell Major debris (plastic, wood, string) and shell Short-term Restoration Impacts? No Yes Yes No No Long-term Recovery Potential? No Yes Yes Yes Yes Figure 5. Model of recovery of the estero floor assemblages after restoration. Red arrows indicate predicted restoration trajectory. The association of Dvex with sites of major debris supports the assumption that mariculture operations provide better habitat for this non-native tunicate. In addition to Dvex, the association of green and red algae with sites of heavy mariculture debris indicates that mariculture operations altered benthic communities in multiple ways. Post restoration monitoring will allow us to determine whether the cover of algae and Dvex within these heavily impacted sites transitions over time to levels more similar to Control sites. Moderate Impact Intact Eelgrass Acknowledgements: National Park Foundation, National Park Service, National Marine Fisheries Service, California Coastal Commission, CoralNet. Sub-surface Surface Min-Mod Major Control Heavy Impact Some of the differences between the transect types are illustrated by four important cover types: eelgrass (Zostera marina), bare sediment, shell and debris, and algae (Figure 4). Note that major debris transects lack Zostera marina cover.
Transcript of Restoration Monitoring of Drakes Estero · 2016-12-09 · Drakes Estero is a 2500–acre estuary...
DISCUSSION/FUTURE EFFORTS Removal of the oyster racks is now ongoing (see photos above) and post-removal monitoring is expected to begin in December 2016. Preliminary monitoring suggests that our pre-restoration monitoring is capturing the variation in the under-rack conditions as it pertains to eelgrass recovery in the former mariculture operation (rack) areas.
Non-metric Multi-Dimensional Scaling (NMDS) clusters the quadrats according to similarity in substrate and community composition on the estero floor. NMDS showed the five transect types fell along a continuum of species assemblages with distinct clusters of sites from each type, but a fair amount of overlap (Figure 3) . Eelgrass (Zostera marina) was strongly associated with Control and Sub-surface transects. Major transects were distinct from all the other transects, and were dominated by debris, Dvex and algal communities.
INTRODUCTION Drakes Estero is a 2500–acre estuary located in Point Reyes National Seashore. It is a State Marine Conservation Area and the only Federal marine wilderness on the west coast south of Alaska. Several decades of commercial oyster mariculture ceased in 2014, leaving behind extensive infrastructure that harbors non-native species, precludes eelgrass growth, and litters the estero floor. In 2016, NPS began the Drakes Estero Restoration Project to remove this infrastructure and debris composed of five miles (~500 tons) of wooden oyster racks and two-acres of plastic tubes, oyster shell, plastic bags, and other mariculture debris on the estero floor. Outside of the mariculture sites, the estero is dominated by large beds of eelgrass, a foundation species designated as Essential Fish Habitat by the National Marine Fisheries Service (NMFS). To comply with permitting from the California Coastal Commission and NMFS, we are assessing: (1) potential impacts of the removal operations on limited eelgrass already growing within the mariculture operation (oyster rack) areas, (2) the recovery of eelgrass in the mariculture operation areas after restoration, and (3) changes to the abundance of the invasive tunicate, Didemnum vexillum (Dvex), within the estuary. We predict,
During the restoration project: 1) there will be very limited short term eelgrass impacts After the restoration project: 2) eelgrass will recover,
A) within the rack areas and exceed the required 1.2 : 1 mitigation ratio B) more quickly in minor-moderate debris plots than major debris plots C) more slowly at sub-sediment beam removal sites than those with surface wood 3) there will be a decrease in Dvex cover
The findings of pre-restoration monitoring are presented here.
Restoration Monitoring of Drakes Estero: Pre-Restoration Assessment of Eelgrass, Marine Debris, and Non-Native Species
Amelia Ryan, Sarah Codde, and Ben Becker Point Reyes National Seashore, National Park Service
METHODS The effects of restoration and the recovery of eelgrass are being assessed using areal percent cover of the estero floor using 0.25m2 quadrat at regular intervals along a transect. Percent cover of each species or substrate in each photo is estimated with the assistance of CoralNet (coralnet.ucsd.edu), an online benthic imagery analysis program. Cover will be estimated at least 3 times:
• Pre-restoration (<60 days prior to removal)
• Post-restoration (<60 days post removal) • Annually post restoration until recovery
goals met
Different transect types were created to capture both short term impacts from rack and debris removal and long term recovery post restoration.
Monitoring Transect Types
RESULTS During the pre-restoration monitoring we assessed percent cover of 564 estuary floor quadrats within 54 transects (treatments and controls) for species community assemblage, substrate, and marine debris.
White globs of Dvex covering strings of oyster shells
Figure 3. NMDS results based on estuary floor cover of 564 quadrats in 54 transects of 5 types: eelgrass bed controls (Control), short-term sub-sediment eelgrass impacts (Sub-surface), short-term surface wood removal impacts (Surface), long-term recovery for sites with no-moderate debris (Min-Mod) and major debris (Major). Ellipses represent standard deviation. Italics represent dominant species/cover types.
Figure 4. Distributions for the four cover types within each transect type.
Figure 2. Distribution across Drakes Estero of different monitoring survey transect types relative to oyster racks.
Figure 1. Project Location
Piles of recently removed oyster rack wood (left) and plastic “french tubes” used in mariculture operations removed from the estero floor.
Intact eelgrass bed in Drakes Estero
Stringing out a transect (left) and preparing to photograph the quadrat on the estero floor (right).
Control Sub-surface Surface Min-Mod Major Eelgrass Present? Yes Yes Yes No, but adjacent No
Mariculture
Debris? None
Wooden crossbeams buried
in sediment
Rack wood fallen on eelgrass, little
plastic or shell
No to moderate debris and shell
Major debris (plastic, wood,
string) and shell Short-term
Restoration Impacts?
No Yes Yes No No
Long-term Recovery
Potential? No Yes Yes Yes Yes
Figure 5. Model of recovery of the estero floor assemblages after restoration. Red arrows indicate predicted restoration trajectory.
The association of Dvex with sites of major debris supports the assumption that mariculture operations provide better habitat for this non-native tunicate. In addition to Dvex, the association of green and red algae with sites of heavy mariculture debris indicates that mariculture operations altered benthic communities in multiple ways. Post restoration monitoring will allow us to determine whether the cover of algae and Dvex within these heavily impacted sites transitions over time to levels more similar to Control sites.
Moderate Impact
Intact Eelgrass
Acknowledgements: National Park Foundation, National Park Service, National Marine Fisheries Service, California
Coastal Commission, CoralNet.
Sub-surface Surface
Min-Mod
Major
Control
Heavy Impact
Some of the differences between the transect types are illustrated by four important cover types: eelgrass (Zostera marina), bare sediment, shell and debris, and algae (Figure 4). Note that major debris transects lack Zostera marina cover.
