Blue Carbon Eelgrass Study

Blue Carbon Eelgrass Study

The San Diego Unified Port District (Applicant) has received grant funding from the Builder’s Initiative to conduct a San Diego Bay-wide evaluation and inventory of carbon storage and sequestration potential (often referred to as “blue carbon”) of two species of eelgrass (proposed project). The proposed study of carbon storage and sequestration in eelgrass (Blue Carbon Eelgrass Study or Study) would be part of an ongoing quantitative effort to characterize carbon sequestration rates within eelgrass beds throughout San Diego Bay. Data collected during the Study would provide data on carbon stocks and sequestration rates, which would support future sampling and restoration efforts, and could provide guidance on future greenhouse gas emissions reduction strategies. Year 3 of the study added thirty-one (31) sampling sites to expand the scope of the study. The first two years of the Study included sampling at the following thirteen (13) sites: 1. Site A (East of Zuniga Jetty): 2. Site B (South of North Island Ammunition Pier) 3. Site C/NB-H-1 (Entrance of Shelter Island Yacht Basin) 9. Site D-1 (East of Coronado Tidelands Park) 12. Site E (Inshore of Homeport Island) 13. Site F/SB-H-3 (West of Chula Vista Bayfront Park) 14. Site G/SB-H-2 (Northwest of the Chula Vista Wildlife Reserve) 15. Site H (West of the Chula Vista Bayfront) 16. Site I (East of Crown Cove) 17. Site J (Along the Northern Shoreline of the Chula Vista Wildlife Reserve) 18. Site L/SC-H-2 (Navy NEMS 6 site) 19. Site N (Lowe’s Coronado Hotel, on West Side of South San Diego Bay) 25. Site O (Former Otay River, In the Middle of South San Diego Bay). The Applicant may continue to conduct sampling at these sites, the additional locations added to the Year 3 study, or a combination thereof, in the future as the Applicant plans to continue to seek funding and continue this study in future years. Year 3 of the study is anticipated to begin in Fall 2024. The study would focus on two species of eelgrass present in San Diego Bay: common eelgrass (Zostera marina) and wide-leaved eelgrass (Z. pacifica). It is anticipated that the Study would occur during the peak growth season for eelgrass. Over three (3) days, the consultant team, led by the firm Environmental Science Associates (ESA), will collect up to 60 sediment samples (e.g., triplicates at 20 sites) at the locations identified. Surface sediment samples will be collected by SCUBA divers to reduce disturbance to and/or mixing with lower sediments. Sample collection locations will be measured with an RTK-GPS from the boat. Samples will be frozen after collection and shipped overnight on ice to a subconsultant, Jonah Ventures, which will analyze the sediment samples and return a list of plant species detected. Plant matter may be reported to higher phylogenetic levels (i.e., not necessarily to the species level). ESA will use eDNA laboratory results to assess the relative abundance of functional plant groups (seagrass, terrestrial, freshwater, and salt marsh) within the samples. Using existing habitat mapping (e.g., National Wetland Inventory), ESA will develop generalized relationships to connect the species found in the sediment carbon with their source locations within/along the bay. As noted, it is not well understood the extent to which DNA abundance can be correlated with organic carbon fractions. ESA will report on assumptions used and uncertainties in data analyses. All subcontractors will support analysis and provide review corresponding to their expertise. In Year 2, three cores were collected and sampled for radioisotope dating to estimate sediment accretion rates. However, preliminary results suggest the radioisotope profiles cannot be resolved from the cores, potentially due to dredging/fill placement history, other landscape-scale disturbance, the coring method used, and/or other factors. For Year 3, the consultant proposes to collect three (3) shorter cores with a tripod setup guided by SCUBA divers. Taking shorter cores will eliminate the need for a vibracore, which may disturb the sediment layers during sampling. SCUBA divers can also visually observe the corer device to make a better determination of the core quality. The cores will be subsampled and sent to a lab for radioisotope analysis. Flett Laboratories will provide modeling and interpretation, and ESA will apply any accretion rates that result from the analysis to estimate sediment carbon accretion rates. ESA will prepare a report summarizing eDNA and radioisotope analyses, including methodologies, results, conclusions and uncertainties. Where applicable, results will be compared to data from Years 1 and 2 of this study. Jonah Ventures scientists will assist with eDNA result interpretation. Research done to develop a method to estimate carbon quantity based on DNA abundance—or to arrive at the conclusion that it is not feasible—will be discussed in the final report. Additional report review will be provided by Merkel & Associates, Silvestrum Climate Associates, and Dave Tomasko, each of whom brings their unique expertise to this experimental and interdisciplinary study. The budget for this task incorporates time for responding to one set of consolidated edits and comments from the Port and the Builders Initiative. Shallow soil sampling would occur at all forty-four (44) locations. Additionally, 1-m coring would occur at three (3) locations (Sites C/NB-H-1, F/SB-H-3, and O), time and budget permitting over a three-day sampling period. A description of each location is included below: 1. Site A (East of Zuniga Jetty): sampling would occur at western end of eelgrass transect line (start location of transect: 479072.77 mE, 3615685.66 mN, end location of transect: 480125.88 mE, 3615857.96 mN). Shallow soil sample. 2. Site B (South of North Island Ammunition Pier): sampling would occur at eastern end of eelgrass transect line (start location of transect: 479072.77 mE, 3615685.66 mN, end location of transect: 480125.88 mE, 3615857.96 mN). Shallow soil sample. 3. Site C/NB-H-1 (Entrance of Shelter Island Yacht Basin): sampling would occur along eelgrass transect line (start location of transect: 478133.17 mE, 3618846.88 mN, end location of transect: 478146.21 mE, 3618653.29 mN). Depth of sampling location: -6 ft NAVD88. Shallow soil sample, 1-m core. 4. Site CB-H-1 (North of H Ave., Coronado): sampling would occur at transect line 483341.93 mE, 3618261.73 mN. Shallow soil sample. 5. Site CB-H-3 (Northwest of Coronado Bridge): sampling would occur at transect line 485305.47mE, 3616660.77 mN. Shallow soil sample. 6. Site CB-L-1 (Northeast of Embarcadero Marina Park North): sampling would occur at transect line 484334.31 mE, 3618751.49 mN. Shallow soil sample. 7. Site CB-L-2 (Northwest of Pier 16): sampling would occur at transect line 485801.15 mE, 3617560.82 mN. Shallow soil sample. 8. Site CB-L-3 (West corner of Glorietta Bay): sampling would occur at transect line 483553.97 mE, 3615829.80 mN. Shallow soil sample. 9. Site D-1 (East of Coronado Tidelands Park): sampling would occur at transect line 484645.42 mE, 3617150.71 mN. Shallow soil sample. 10. Site D-2 (East of Coronado Tidelands Park): sampling would occur at transect line 484694.97 mE, 3617142.75 mN. Shallow soil sample. 11. Site D-3/CB-H-2 (East of Coronado Tidelands Park): sampling would occur at transect line 484737.05 mE, 3617153.69 mN. Shallow soil sample. 12. Site E (Inshore of Homeport Island): sampling would occur along eelgrass transect line (start location of transect: 484988.77 mE, 3614913.87 mN, end location of transect: 485340.45 mE, 3614908.16 mN). Shallow soil sample. 13. Site F/SB-H-3 (West of Chula Vista Bayfront Park): sampling would occur at transect line 490124.01 mE, 3609282.87 mN. Depth of sampling location: -4 ft NAVD88. Shallow soil sample, 1-m core. 14. Site G/SB-H-2 (Northwest of the Chula Vista Wildlife Reserve): sampling would occur at transect line 489563.94 mE, 3608967.42 mN. Shallow soil sample. 15. Site H (West of the Chula Vista Bayfront): sampling would occur at South Bay Borrow Pit (489125.39mE, 3609510.83). Shallow soil sample. 16. Site I (East of Crown Cove): sampling would occur south of eelgrass transect line (start location of transect: 487147.19 mE, 3610468.26 mN, end location of transect: 488574.09 mE, 3611161.79 mN). Shallow soil sample. 17. Site J (Along the Northern Shoreline of the Chula Vista Wildlife Reserve): sampling would occur at transect line 489851.77 mE, 3608809.52 mN. Shallow soil sample. 18. Site L/SC-H-2 (Navy NEMS 6 site): sampling would occur at transect line 485334.08 mE, 3614322.72 mN. Shallow soil sample. 19. Site N (Lowe’s Coronado Hotel, on West Side of South San Diego Bay) sampling would occur at transect lines 487640.93 mE, 3610468.26 mN. Shallow soil sample. 20. Site NB-H-2 (East of North End of Shelter Island): sampling would occur at transect line 479508.62 mE, 3620133.02 mN. Shallow soil sample. 21. Site NB-H-3 (Along the Southern Shoreline of Harbor Island): sampling would occur at transect line 480868.58 mE, 3620803.99 mN. Shallow soil sample. 22. Site NB-L-1 (Southwest of Southwestern Yacht Club, within Shelter Island Yacht Basin): sampling would occur at transect line 477969.90 mE, 3619499.24 mN. Shallow soil sample. 23. Site NB-L-2 (Americas Cup Harbor): sampling would occur at transect line 479145.81 mE, 3620526.31 mN. Shallow soil sample. 24. Site NB-L-3 (West of West end of San Diego International Airport Runway): sampling would occur at transect line 480568.03 mE, 3622151.63 mN. Shallow soil sample. 25. Site O (Former Otay River, In the Middle of South San Diego Bay) sampling would occur at transect line 488593.10 mE, 3609529.58 MN. Depth of sampling location: -13 ft NAVD88. Shallow soil sample, 1-m core. 26. Site OT-1 (Otay River Outlet): sampling would occur at transect line 489168.96 mE, 3606858.55 mN. Shallow soil sample. 27. Site SB-H-1(South Side of Sweetwater River Outlet): sampling would occur at transect line 488629.30 mE, 3611919.65 mN. Shallow soil sample. 28. Site SB-L-1 (Entrance to Marsh Channel on Sweetwater River Across from Pepper Park): sampling would occur at transect line 489611.89 mE, 3612297.64 mN. Shallow soil sample. 29. Site SB-L-2 (Southwest of the Chula Vista Wildlife Reserve): sampling would occur at transect line 489475.90 mE, 3608318.65 mN. Shallow soil sample. 30. Site SB-L-3 (Within Chula Vista Marina, Near South Entrance): sampling would occur at transect line 490306.36 mE, 3609441.84 mN. Shallow soil sample. 31. Site SC-H-1 (Southeast of Coronado Bridge): sampling would occur at transect line 485650.89 mE, 3616440.27 mN. Shallow soil sample. 32. Site SC-H-3 (Along the shoreline of the National City Marine Terminal): sampling would occur at transect line 488681.97 mE, 3612595.75 mN. Shallow soil sample. 33. Site SC-L-1 (Northeast of Glorietta Bay Park): sampling would occur at transect line 484346.41 mE, 3615418.77 mN. Shallow soil sample. 34. Site SC-L-2 (Southwest of Naval Amphibious Base Coronado): sampling would occur at transect line 485118.13 mE, 3614608.86 mN. Shallow soil sample. 35. Site SC-L-3 (Fiddler’s Cove Marina): sampling would occur at transect line 486021.56 mE, 3612899.15 mN. Shallow soil sample. 36. Site SM-1 (West of Sweetwater Marsh): sampling would occur at transect line 489647.62 mE, 3611065.16 mN. Shallow soil sample, vegetation sample. 37. Site SM-2 (West of Sweetwater Marsh): sampling would occur at transect line 489586.84 mE, 3611020.59 mN. Shallow soil sample, vegetation sample. 38. Site SM-3 (West of Sweetwater Marsh): sampling would occur at transect line 489376.01 mE, 3610919.08 mN. Shallow soil sample. 39. Site SM-4 (West of Sweetwater Marsh): sampling would occur at transect line 489179.31 mE, 3610834.31 mN. Shallow soil sample. 40. Site SP-1 (Within Restored Habitat Area East of Silver Strand Training Complex): sampling would occur at transect line 488586.97 mE, 3606941.45 mN. Shallow soil sample, vegetation sample. 41. Site UV-1 (South of Western Side of Harbor Island): sampling would occur at transect line 480251.46 mE, 3620583.61 mN. Shallow soil sample. 42. Site UV-2 (Southeast of Coronado Tidelands Park): sampling would occur at transect line 484815.87 mE, 3616730.79 mN. Shallow soil sample. 43. Site UV-3 (Southwest of Pier 5, In the Middle of South Central San Diego Bay): sampling would occur at transect line 486810.70 mE, 3615010.90 mN. Shallow soil sample. 44. Site UV-4 (Entrance to Pier 32 Marina): sampling would occur at transect line 489754.83 mE, 3612453.36 mN. Shallow soil sample. Most of the sampling locations would occur along existing eelgrass transect lines utilized by the U.S. Navy in their evaluations of San Diego Bay eelgrass beds. All locations would be accessed by boat and divers would conduct the sediment analysis activities detailed below. Sediment Analysis: The sediment analysis portion of the Study includes two components: shallow soil sampling, and sediment coring. Shallow soil sampling: Surface sediment samples will be collected by SCUBA divers across 20 of the 44 locations identified above to reduce disturbance to and/or mixing with lower sediments. Sediment samples will be used in accordance with eDNA laboratory results to assess the relative abundance of functional plant groups within the samples, to determine which carbon sources from around San Diego Bay are accumulating in eelgrass beds. Sediment coring: Three (3) sediment core samples would be taken at three locations (sites C/NB-H-1, F/SB-H-3, and O) during the sampling period (approximately 9 samples total). All cores would be collected at a one-meter-depth. The consultant proposes to collect three (3) shorter cores with a tripod setup guided by SCUBA divers. As stated previously, taking shorter cores will eliminate the need for a vibracore, which may disturb the sediment layers during sampling. SCUBA divers can also visually observe the corer to make a better determination of the core quality. The cores will be subsampled and sent to a lab for radioisotope analysis. Flett Laboratories will provide modeling and interpretation, and ESA will apply any accretion rates that result from the analysis to estimate sediment carbon accretion rates. Due to its nature and limited scope, construction of the proposed project would generate a minor amount of vehicle trips and would require limited use of equipment. Therefore, impacts related to air quality, greenhouse gas emissions, and transportation and traffic are not anticipated to occur. Furthermore, the Applicant would be responsible for complying with all applicable federal, state, and local laws regarding construction demolition debris, hazards and hazardous materials, and stormwater.

Chula Vista, Coronado, Imperial Beach, National City, San Diego

San Diego

Southern California

San Diego