Flagler Park Living Shoreline Monitoring Vincent Encomio, Pam Hopkins, Katie Tiling, Josh Mills 9/23/2016

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1 FLORIDA OCEANOGRAPHIC SOCIETY Flagler Park Living Shoreline Monitoring Vincent Encomio, Pam Hopkins, Katie Tiling, Josh Mills 9/23/2016

2 Flagler Living Shoreline Monitoring Summary Constructed oyster reefs and Spartina alterniflora plantings in the St. Lucie River (Flagler Park) in Stuart, FL were monitored to track restoration success. Basic oyster and shoreline vegetation metrics were measured over two samplings. To track effects of freshwater discharges, oyster survival was monitored weekly over periods when salinities were less than 5 psu over all tides. Restoration Site All monitoring work was conducted in the St. Lucie River along the downtown Stuart riverfront adjacent to Flagler Park. The restoration area stretches west from the City of Stuart docks to Flagler Park (see Figure 1). The site was established by Martin County in 2011, initially as an oyster restoration site. Since then Spartina alterniflora plantings have been installed along available areas of shoreline to further expand the area as a living shorelines restoration site. Oyster reef restoration Oyster reefs were constructed over a series of community-based restoration events. Recycled shell (primarily oyster, but also clam and mussel) and mined beach shell were containerized into aquaculturegrade (Naltex) mesh bags and then deployed at the site to construct a series of intertidal oyster reefs (see Figure 2). Bagged shell modules were hand-placed by volunteers and typically were 1-2 tiers of shell high, depending on the depth at mean low water. Placement was such that reefs were exposed at most low tides. Spartina restoration Nursery-grown S. alterniflora was planted at two locations within the restoration site. Successive plantings were either plugs or 1 gallon size plants. The planting areas are shown in Figure 3 as Transect W-1 and Transect E-1. Both planting areas are located shoreward of the public boardwalk. Oyster and Spartina Monitoring Oysters and Spartina were monitored along several established transects shown in Figure 3. For Spartina plantings metrics were sampled haphazardly within each planting area (W-1 and E-1). Oyster metrics were sampled along 3 transects (1-3). Transect lengths were variable and based on distance required to traverse at least one constructed oyster reef. Transect descriptions are below. Transect Descriptions Transect 1 ( East ) was pre-marked by Martin Co. with survey marker on landward side of boardwalk. The transect is lined up with this marker. Transect line runs from planting area to oyster reefs (33.6 m long). Transect 2 ( Spoto s ) is lined up between 2 rooftop air conditioning units on waterfront restaurant and parallel with pier. The transect line runs 22.5 m out from shore/boardwalk. Along this transect are constructed oyster reefs and reef balls. 1

3 Transect 3 ( City Dock ) This transect starts at the first piling west of the pier leading to the City of Stuart boat docks and runs parallel to the pier. Transect line runs 24.6 m from the piling and traverses constructed oyster reef. Reef balls are adjacent to the northwest. Planting areas W-1: West planting area is the larger of the two planting areas and is located just east of the Flagler Park Center and immediately west of T-junction on boardwalk. E-1: The East planting area is lined up with Transect 1. Oyster Monitoring Transect sampling of live oyster density Transect samples were conducted in October Along each transect (1-3) a m 2 (0.25 m x 0.25 m) quadrat was placed over a section of reef. Quadrat locations along each transect were selected haphazardly and placed within 1 meter of the transect line. Within each quadrat all cultch material was excavated and washed to remove sediment. All live and dead eastern oysters of all sizes were identified and counted. Oysters with both left and right valves intact and closed were counted as live. An additional check was made by attempting to pry open the oyster with an oyster knife. If the valves remained closed, the oyster was counted as live. Most of the live oysters had visible signs of active growth (bill growth on outer margins) as well. A dead oyster was defined as an empty oyster with both valves intact and connected via its hinge ligament (articulated shell). Disarticulated shells (only one valve present) were not counted as dead. Four quadrats were taken along each transect. Data are reported as mean number of (live) oysters m -2 and % of live oysters per transect ± standard errors, respectively. Oyster shell heights Within each transect quadrat sample, live oysters were measured for shell height. A Vernier caliper was used to measure length of shell from the umbo to the distal margin of the shell, or longest point of shell growth. Pieces of cultch were selected haphazardly for shell height measurement. To avoid measurement bias, all oysters found on a single piece of selected cultch were measured. At least oysters were measured per sample. If the number of oysters in a sample was less than 10, all oysters were measured. Mean oyster shell height ± standard error was determined for each transect and for all sampled oysters. A Size-frequency distribution was constructed from the data, binning shell height data in 5 mm increments (0-5 mm, 6-10 mm, etc.). Data are reported as shell height in millimeters (mm) vs. frequency. Median shell heights were calculated for each site. Survival monitoring (% of live oysters) Starting on January 30, 2016 freshwater discharges from Lake Okeechobee began impacting the St. Lucie River. Although winter discharges did not adversely impact oyster survival in the central estuary (east of the Roosevelt Bridge; see Figure 4), it was thought that lowered salinity combined with high summer temperatures would result in oyster mortalities. Therefore, we decided to monitor oyster survival during a summer discharge period (June to July 2016) to determine discharge effects on oyster restoration reefs at Flagler. Survival over time was monitored during freshwater discharges starting in June 2016, when 2

4 salinities consistently stayed below 5 parts per thousand on all tides (see Figure xx). At each site visit, m 2 (0.5m x 0.5m) quadrats were haphazardly placed on separate restored reefs. Quadrats were interspersed at least m apart to adequately represent the site as a whole. Within each quadrat, all shell material (loose shell and shell clusters) was excavated to the base substrate, washed and brought back to land for counting. Oysters of all sizes (live and dead) were counted (Figure X).Generally, 5-15L of shell was found within each quadrat. All reefs sampled were at least 3 years old. Samplings were conducted on June 1, June 13, June 22, July 12, July 20 and July 27, Data are presented as mean % of live oysters ± standard error. Spartina alterniflora monitoring Spartina plantings were assessed by measuring % cover. Within each planting area (W-1 and E-1), a 1.0 m 2 quadrat was placed haphazardly within each planting area and % cover was estimated. Replicate quadrats were evaluated within the general footprint of each planting area. Assessments were conducted in October 2015 and June Results Transect samples Live oyster density and % live Transect sampling of live oyster densities showed that densities decreased from Transect 1 to Transect 3 (See Figure 5). Average oyster densities for all 3 transects (n=12 quadrats) was 387 ± 62 (standard error) oysters m -2. An attempt to estimate visual % cover of live oysters was attempted, but a rising tide and turbid water made this difficult and thus % of live oysters was determined instead. The percentage of live oysters is shown in Figure 6. No apparent differences between transects were observed. Mean % of live oysters across all transects was 88 ± 3.1 %. Shell heights Over all quadrats a total of 147 oysters were measured for shell height. Mean shell heights per transect are shown in Figure 7. No differences were apparent between transects. Overall mean shell height was 46.9 ± 5.6 mm. A frequency distribution of shell heights showed a wide range of size classes (median shell height = 45.8 mm) with most oysters in the juvenile (>15.0 mm) to large adults (>85.0 mm) (Figure 8). The wide range of size classes indicates successive periods of successful recruitment to the restoration reefs. Oyster survival The % survival of oysters is shown in Figure 9. Little change in survival was observed during these samplings and overall mean % of live oysters was 77.4 ± 3.2 %. Survival increased at the last sampling (July 27, 2016: 82.4 ± 3.9 %). This increase was likely due to the presence of newly settled spat observed on shell clusters. To verify survival and condition of oysters, individuals were periodically shucked to examine tissue condition. In almost all cases, oysters displayed good condition (see Figure 10B for example). Moribund, or dying oysters were only observed during one sampling. Sampling was halted after July 27, as salinities began to consistently increase above 5 ppt (Fig. 11). Although there was an 3

5 overall decrease in % of live oysters from the October 2015 samplings to the June-July 2016 samplings (88 % to 77 %), oyster survival was still fairly high and with relatively little change from surveys conducted by FWC in March Although discharges were consistent throughout the sampling period, each weekly discharge period incorporated a 2 day stoppage, designed to more closely simulate pulse-like rain and runoff events. These recovery periods resulted in temporary salinity increases that may have alleviated salinity stress to oysters and enabled more prolonged periods of survival. S. alterniflora monitoring Mean % cover of S. alterniflora was higher in the W-1 planting area (62.5%) compared to the E-1 planting area (45.9%). Percent covers did not change significantly between both sampling periods (see Figure 12). Overall growth was robust and each planting area displayed expansion beyond original planting locations, particularly at the E-1 location, in which Spartina expansion past the water ward side of the boardwalk was observed in both October 2015 and in June 2016 (See Figures 13A and 13B). The plantings in this area are directly protected by restored oyster reefs and Spartina expansion was even observed to extend through and just beyond bagged shell in June An increase in water ward growth of other shoreline vegetation (railroad vine - Ipomoea pes-caprae) was also observed at E-1. 4

6 Figure 1. Map showing Flagler Park restoration site (yellow box) and Roosevelt Bridge (location of water quality station) in Stuart, FL.

7 Figure 2. Map of restored oyster reefs at Flagler Park.

8 Transect 1 Transect 2 Figure 3. Sampling areas within restoration site showing oyster reef Transects 1-3 and Spartina planting areas W-1 and E-1

9 Figure 4. Results from FWC oyster survey (source: Water Resources Advisory Board presentation,south Florida Water Management District). Mid-estuary mortality levels are shown to be less than 20% after nearly 4 weeks at salinities < 5 ppt).

10 Figure 5. Mean oyster densities along Transects 1-3. Figure 6. Mean % of live oysters along Transects

11 Figure 7. Mean oyster shell heights along Transects 1-3. Figure 8. Size class frequency distribution of shell heights measured across all transects. 2

12 Figure 9. Periodic samplings of % live oysters during a 2 month period of Lake Okeechobee discharges. 3

13 Figure 10A. Photos of oyster sampling. Figure 10B. Shucked oyster showing oyster in good condition. 4

14 Figure 11. Salinities at the Roosevelt Bridge during survival assessments. 5

15 Figure 12. % cover of Spartina alterniflora within two plantings areas at the Flagler Park restoration site. Figure 13A-B. Photos showing waterward expansion of Spartina plantings at E-1 planting area. 6