SAV Restoration Reconsidered: Designing with Nature

1. SAV Restoration Reconsidered: Designing with Nature (Reflections on SAV restoration from recent review of Bay eutrophication) W. M. Kemp and L. Murray University of Maryland Center Environmental Science SAV Workgroup 23 January 2006 Work supported by US A COE & NOAA MDSG

2. Main Points of MEPS Article Related to Bay SAV W.M. Kemp, W.R. Boynton & 16 others. 2005.Eutrophication of Chesapeake Bay: historical trends and ecological interactions. Mar Ecol Prog Ser 303: 1-29 (1)Unprecedented decline in SAV was largely in response to nutrient enrichment and climatic events. (2) Important loss of habitat for fish and invertebrates. (3) Important loss of SAV community’s ability to mediate nutrient cycling, sediment transport and water clarity. (4) SAV bed positive feedback effects (which enhance plant growth conditions) tend to reinforce both degradation & restoration trajectories (5) Initial trends of SAV recovery, evident in certain Bay regions, may be related to combination of improving water quality and favorable climate (6) Bay SAV restoration efforts could exploit this initial recovery as well as associated self-enhancing positive feedback effects. (7) Regional approaches to Bay SAV restoration could apply knowledge of environmental and species differences to maximize effectiveness

3. Degradation Trajectory Summary of Nutrient-Related Feedbacks in Bay Ecosystem • Positive & negative feedbacks control paths of ecosystem change with both degradation and restoration of Bay • Hypoxia leads to more nutrients, more algae, & more hypoxia • Turbidity leads to less SAV causing more turbidity • Oysters & marshes tend to reinforce these feedbacks ( Kemp et al 2005)

4. Degradation Trajectory Restoration Trajectory Summary of Nutrient-Related Feedbacks in Bay Ecosystem • Positive & negative feedbacks control paths of ecosystem change with both degradation and restoration of Bay • Hypoxia leads to more nutrients, more algae, & more hypoxia • Turbidity leads to less SAV causing more turbidity • Oysters & marshes tend to reinforce these feedbacks ( Kemp et al 2005)

5. Solomons Island 1933 1999 Dramatic Bay-Wide Decline of Seagrass (Submersed Aquatic Vegetation, SAV) • Prior to 1960 most of the Bay bottom at depths < 1.5 -2 m was inhabited by diverse species of SAV • SAV decline started in upper Bay and Western shore tributaries, then moved to lower Bay and Eastern shore systems • Solomons Is., near mouth of Patuxent R. (CBL), was surrounded by SAV prior to 1965, but bare since 1975 • Huge loss of animal habitat Solomons Island 1999

6. 10 • 8 • 6 • 4 • 2 • - 0 Trends and Causes of SAV Decline in Bay • Sharp SAV decline in upper Bay in early 1960s, especially after TS Agnes • Modest recovery since mid-1980s, but still only 30% of former levels • Experiments and field studies reveal higher nutrients decrease light for SAV due both to: • (1) decreased water clarity (phytoplankton) • (2) increased epiphytic algae on SAV leaves ( Kemp et al 2005)

7. 100 Atmosphere 80 60 Diffuse Sources Percent of Total N-Sources 40 Particulate Nitrogen Trapping 20 Point Sources Plant Uptake 0 SAV Beds as Sinks for N-Loading to Bay • Historical Bay SAV beds were capable of removing ~45% of current N Loading • Primary pathways of N removal would be trapping particulate N & direct assimilation • Calculation only considers mainstem upper (MD) Bay • N removal rates would be larger if whole Bay were considered Denitri- fication N-Sinks (SAV Beds) N-Sources ( Kemp et al 2005)

8. Susquehanna Flats (Quad #003) 4 3 SAV Cover (103 Hectares) 2 1 Year 0 2002 2004 1996 2000 1994 1998 1988 1990 1992 1980 1986 1984 1982 Abrupt Upward Shift in SAV Recovery for Susquehanna Flats in 2005 ? • Does the abrupt 2005 rise • in SAV density reflect bed • self-enhancement? • What are the specific • mechanisms . . . increased • water clarity . . . what else? • How can we identify beds • approaching this ‘transition’ • point in their recovery? • How do these processes • vary among Bay regions & • SAV species? • Can an SAV restoration • program exploit this • process?

9. 250 Severn River (Quad #023) 100 200 150 200 SAV Cover (Hectares) 150 100 ‘03 ‘00 1.0 1.2 0.8 0.6 Secchi (m) 50 50 0 0 2004 2000 1996 2002 1994 1998 1986 1988 1990 1992 Year Middle (Mesohaline) Bay Recovery is Dominated by Highly Variable Ruppia Beds: Severn River • Severn River quad mostly • R. maritima, with one large • dense bed of P. perfoliatus • Note the high variability in • total SAV cover during • period of recovery • P. perfoliatus bed initiated • within sparse Ruppia bed in • late 1990s (J.P. Williams) • Note that variability since • 2000 is correlated to climate • and water clarity (2000 and • 2003 were wet years)

10. Broad Creek (Quad 044) 0.8 0.6 ‘03 ‘00 0 Cover (103 Hectares) 0.4 0.2 1.0 0.8 0 0.6 2004 2000 1996 2002 1994 1998 1988 1986 1990 1992 0.4 Year 0.2 1.5 2.0 1.0 0.5 Secchi (m) Middle (Mesohaline) Bay Recovery is Dominated by Highly Variable Ruppia Beds: Broad Creek • Broad Creek quad also • R. maritima, except for • transplanted P. perfoliatus • and S. pectinata • Note the extreme variability • in total SAV cover during • since survey began!! • Again, note that variability • since 2000 is correlated to • climate & water clarity

11. Bed-Scale SAV Cover Percent cover Epiphyte Biomass, afdw g/g SAV Bed Patchiness Edge density Epiphytes Reduced in Larger Denser Ruppia Beds • Lower epiphyte levels in denser • SAV beds (higher % cover at • at whole bed scale) • Higher epiphyte levels in more • patchy beds (higher Edge Density) • Similar bed-scale effects seen for • sediment nutrients, % silts/clays • Thus, beds that are denser & more • continuous have lower epiphyte • levels (lower water column N & P • due to higher nutrient trapping) (K. Schulte.2002.MS Thesis)

12. NH4 Recycling Dark Dark Light Light Denitrification Denitrification Nitrification Nitrification R. maritima R. maritima Bare Bare Bare P. perfoliatus P. perfoliatus Nutrient Cycling Intensity Higher in SAV Beds • Sediment biogeochemistry compared • in beds of two SAV species and in • adjacent “bare” sediments • Higher rates of NH4 uptake & release • indicate beds as sites of intense • nutrient cycling • Higher nitrification & denitrification • indicates SAV beds as key sites of N- • removal from Bay ecosystem • Mechanisms include enhanced particle • trapping % root O2 release stimulating • sediment nitrification which in turn • supports high denitrification (J. Davis. 2005. PhD Thesis)

13. Conceptualization of SAV Beds as Fish Habitats • SAV beds provide habitat for fish, • shellfish & waterfowl, and enhance • water quality conditions for better • plant growth • Ruppia maritima provides GOOD • habitat for consumers and SAV • Other SAV spp native to mesohaline • (e.g., P. perfoliatus) provide • EXCELLENT habitats

14. Broad Creek Yes La Trappe Cr No Choptank River Lakes Cove No Choptank Bridge No (A. Hengst) (J. Melton) Transplanted P. perfoliatus Survival in Choptank River SAV Restoration Sites • Transplants always successful • in Ruppia beds, not bare sediments • Even sparse Ruppia beds provide • positive-reinforcement for transplants • Transplants have been most • successful in Broad Creek • Better water quality but also • extensive Ruppia beds

15. Transplant Growth vs. Nursery Bed Area/Density P. perfoliatus Growth (g dw m-2) (A. Hengst) R. maritima bed biomass (area-weighted g dw m-2) Transplanted P. perfoliatus Growth in Ruppia Beds of Various Size & Density • P. perfoliatus transplant • success was unrelated • to Ruppia biomass • Transplant success (as • growth) was related to • Ruppia bed size & density • Larger Ruppia beds • provide better growth • conditions for transplants

16. Self-Propagation of Potamogeton Transplants • “Founder Colony” concept • Small transplants of stable SAV species • “Nursed” by fluctuating R. maritima beds • Long-term survival & natural expansion • Re-introducing formerly dominant spp. • (P. perfoliatus & S. pectinata) S. pectinata “satellites” (2004) (2001) P. perfoliatus “satellites” Original (10 m2) Transplants ~300 m

17. S. Pectinata satellite P. perfoliatus satellite 500 400 “Satellites” (2005) 300 Plant Area (m2) 200 Transplants (2001) 100 0 S. pectinata P. perfoliatus Self-Propagation of Potamogeton Transplants • Satellite patches of trans- • planted spp. arise in area • around transplant site • Natural self-propagation • of both transplanted spp. • within Ruppia beds • Within 4 years restored • area had increased by a • 3-4 fold (underestimate!!)

18. Key Points in the Chesapeake 2000 Agreement • Submerged Aquatic Vegetation • “Recommit to the existing goal of protecting and restoring[not • transplanting] 114,000 acres of submerged aquatic vegetation (SAV)” • “By 2002, implement a strategy to accelerate protection and restoration • of SAV beds in areas of critical importance to the Bay’s living resources” • Multi-Species Management • “By 2005, develop ecosystem-based multi-species management plans • for targeted species” [should this be applied to SAV species?]

19. Shoots Seeds Current Status Bay SAV Restoration Program "The figures below show results of restoration efforts by ...(VIMS), ... (MD DNR), and ... (CBF) between 1979 and 2004. Regardless of whether adult shoots or seeds were used in active restoration, most transplants survived for less than five years." (Dennison et al. 2005. IAN Newsletter)

20. Region: Upper Bay Salinity: Oligohaline, Tidal Fresh SAV Communities: “FRESHWATER MIXED” SAV Restoration: Propagules from feeder crks ? Tier I SAV Habitat: 10,000 ha Region: Middle Bay Salinity: Mesohaline SAV Communities: “POTAMOGETON”, “RUPPIA” SAV Restoration:Ruppia as “nursery beds” ? Tier I SAV Habitat: 25,000 ha Region: Lower Bay Salinity: Polyhaline SAV Communities: “ZOSTERA” SAV Restoration:Zostera seed dispersal Tier I SAV Habitat: 12,000 ha Regional Approach for SAV Restoration

21. Concluding Comments • Favorable climatic conditions & nutrient control have apparently • contributed to the small but important ongoing SAV recovery. • (2) SAV beds enhance their own growth conditions by particle trapping, nutrient uptake, and nutrient transformation. • (3) Signs of abrupt increases in SAV bed size, density and health (that are apparent in some areas) suggest natural feedback enhancement. • (4) Variations in SAV trends among regions and SAV species may suggest the need for regional approaches to restoration. • (5) C2K calls for ‘recommitment’ to SAV restoration (not transplanting); need to apply knowledge and wisdom in restoration strategies. • (6) How can we identify beds that are approaching ‘transition points’ in development, and what restoration efforts could be adopted that would help to nudge beds over the threshold to sustained health? • (7) Maybe its time to re-assess current approaches and strategies for Bay SAV restoration.