Rochelle Seitz, Katie Knick, Amanda Lawless, & Cassie Bradley Virginia Institute of Marine Science

Transcription

1 Effects of shoreline stabilization structures on living resources in estuaries: changes in abundance, biomass, and diversity of benthic invertebrates and their predators Rochelle Seitz, Katie Knick, Amanda Lawless, & Cassie radley Virginia Institute of Marine Science

2 Outline Importance of marshes ottom up effects on predators Shoreline development effects York River (Pris) Elizabeth-Lafayette (Dev) road ay -- Lynnhaven River (Pris) Patuxent River (Dev) Links between different shoreline stabilization structures and fauna

3 Importance of Marshes & Development Ecosystem services of marshes Nutrient retention & cycling Refuge & structure iological energy flow and transfer ~6% of Atlantic Coast will be developed (Titus et al. 29) Coastal development & pollution Sea-level rise Shoreline hardening Synthesis of shoreline development effects and landscape-level patterns is warranted

4 Compare sub-estuaries of differing land use % Hardened shoreline % Developed land

5 Prey and Predators: ottom-up control from Seitz et al. 23; Seitz et al., 28

6 Objectives Synthesize effects of shoreline development upon bivalves (Lafayette & road ay) and benthic community (York River & Patuxent) gradient of developed landscapes Different structures Determine effects of shoreline development on predators Estimate criteria for shoreline effects

7 Study Sites Patuxent Elizabeth- Lafayette York road ay Shoreline development in four locations: York River (N = 12) Elizabeth-Lafayette (N = 4) road ay (N = 12) Patuxent (N = 12)

8 Three Shoreline Types Natural Marsh ulkhead Rip-Rap

9 Gradient in % Natural Marsh % Shoreline natural marsh Pris A Pris Dev York River road ay Eliz-Lafayette P =.37 Dev Patuxent River System

10 Methods enthic Sampling Suction sample--.11 or.17 m 2 to 3 cm depth Density & diversity Shallow (< 1.5 m) 1-mm sieve 1-cm core on.5-mm sieve 3-cm core for sed grain size Predator sampling Otter trawl 3-m transect Density of fish and crabs

11 York & Lafayette Rivers: enthos York (Pris) H' (bits/individual +SE) Density (no. m -2 + SE) a) Shannon-Wiener diversity 2. P =.15 A b) Number of organisms A NM RR A A A NM RR Shoreline Type P =.1 Lafayette (Dev) mean no. m -2 (+SE) Seitz et al., MEPS a) Macoma balthica A b) Tagelus plebeius P =.37 NM RR Shoreline Type P =.37 P >.5

12 York (Pris) & Lafayette (Dev): Predators Significantly more crabs in Natural Marsh (p =.3) Total number of organisms/trawl (+SE) a) Fish predators b) Crab predators Lafayette York Lafayette York NM RR Shoreline

13 road ay (Pristine): ivalves Diversity greater in Natural Marsh and Rip rap (similar to York) More bivalves in Natural Marsh and Rip Rap More pristine system (8% marsh) does not show negative effects in Rip-rap habitats H' (bits/individual +SE) Mean No. (+SE) per sample road ay ivalves- Shannon-Wiener Diversity Natural Marsh Rip Rap ulkhead A NM RR A Shoreline Type road ay ivalves - Total Abundance NM RR Shoreline Type p =.34 p =.54 Natural Marsh Rip Rap ulkhead

14 road ay: Predators No significant difference among shoreline habitats Predators abundant in Marsh but not Rip-rap or bulkhead Mean No. Individuals (+SE) road ay Predators (Fish + Crabs) - Total Abundance p =.97 p =.97 Natural Marsh Rip Rap ulkhead NM RR Shoreline Type

15 Patuxent (Dev): Density & iomass Shoreline type influences benthic density Mean No. m Patuxent enthos Density NMPatuxent RR iomass Shoreline Type Developed system shows deleterious effects on rip-rap habitats Shoreline top predictor in AIC stats iomass (g AFDW m -2 ) + SE NM RR Shoreline Type

16 Patuxent (Dev): Predators Positive relationship between benthic biomass and predators: bottom-up control Deleterious effects in rip-rap habitats in developed systems iomass (g AFDW m -2 ) + SE Patuxent iomass NM RR Shoreline Type

17 Threshold for negative effects % Shoreline natural marsh Pris York River A Pris road ay Dev Eliz-Lafayette P =.37 >5% marsh Critical level Dev Patuxent River System

18 Density by % Wetland R 2 =.58

19 Summary Natural marsh has highest density and diversity; Rip Rap and ulkhead shorelines show negative effects Rip rap may be moderate habitat when nearby natural marsh cumulative effects (e.g., York, road -- pristine ) gray solution Predators may be adversely affected by shoreline development & more abundant in marshes where prey are abundant Habitat degradation may be linked with loss of higher trophic levels >5% natural marsh necessary for subsidizing adjacent habitats; thus living shorelines recommended green solution There is a crucial link between natural marshes, benthic infaunal prey, and predator abundance; therefore, protection and restoration of marsh habitats may be essential to the maintenance of high benthic production and consumer biomass in Chesapeake ay and similar estuarine systems

20 Acknowledgements Funding by: NOAA CSCOR, Army Corps of Engineers, VA Commonwealth, Chesapeake ay Restoration Fund, NSF REU program Assistance from: VIMS Community Ecology Group, VIMS Marine Conservation iology Group, NSF REU students