Can living shorelines be an effective form of coastal habitat restoration?

Transcription

1 Can living shorelines be an effective form of coastal habitat restoration? Donna Marie Bilkovic, Molly Mitchell, and Carl Hershner Virginia Institute of Marine Science May 24, 2012

2 Cumulative Impacts of Shoreline Hardening & Riparian development Forest suppression & fragmentation Natural connections between upland & wetland severed Tidal wetland loss Sediment supply & transport altered Static homogeneous shoreline, less biodiversity Aquatic habitat decline Decrease fish biomass and diversity Prevents the natural migration of habitats as sea level rises

3 Ecosystem service approach to shoreline protection With the observed negative effects of hardened shorelines there is a need for alternative erosion protection approaches Living shorelines designed to control erosion, while simultaneously enhancing estuarine habitats Soft (non-structural) Hybrid structure used to support plant growth LEGISLATION Maryland LS Protection Act (2008) Requires non-structural shoreline protection practices unless proven infeasible Virginia Legislation passed in 2011 requiring the development of a general permit for living shorelines. Virginia s approach is to streamline permit process for LS

4 Research Objectives THE ISSUES Habitat Conversion - Living Shoreline Multiple living shoreline types & designs Limited research on ecosystem services & functioning of these shorelines Existing intertidal & subtidal Research Goals 1) Assess ecological trade-offs of habitat conversion 2) Identify performance metrics to assess the effectiveness of living shorelines for ecosystem function & erosion control New Intertidal Ecological tradeoffs of conversion? Non-vegetated wetland to sand fill & planted marsh Shallow water to planted marsh & sill

5 Pilot survey design & components Ecological Infauna live in the sediment Epifauna - live on the surface Water Quality Sediment Vegetation complementary Engineering Produced high resolution elevation surface maps of shorelines Pre & Post storm events 4 shoreline types o Living shoreline o Riprap revetment o Natural Marsh o Intertidal Flat Why BENTHOS? Respond quickly to impairments Mostly sedentary reflecting local conditions Provide many ecosystem services to maintain good water and sediment quality

6 Survey Locations 3 study areas Severn River, MD Created marsh & biolog 4 yrs old South River, MD Marsh-sill (large gaps) 2 yrs old East River, VA Marsh-sill (small gaps) 7 yrs old

7 For Example, East River Living Shoreline Site Randomly select 6 9 transects per habitat Sill, gap, biolog, riprap, flat, marsh Randomly select offshore direction from intertidal for placement of subtidal transects AT EACH TRANSECT AND TIDAL ZONE, TAKE DEEP CORES FOR INFAUNA, SEDIMENT SAMPLES, & WATER QUALITY MEASURES. EPIBENTHIC COUNTS IN INTERTIDAL.

8 Field Work: Transect Placement & Water Quality & Plant Measures Intertidal transects Subtidal transects Recording transect position - GPS Marsh plant stem counts Marsh plant height Water Quality Sonde

9 Field Work: Epifauna Counts Epifauna: animals living on or just above the substrate. They may be firmly attached (sessile), relatively sedentary, or highly motile. Oysters, mussels, barnacles, snails, sponges & sea squirts ~ 98% of the epifauna by weight (biomass) were suspension feeders Barnacles & Oysters Barnacles Balanus spp Oysters Movie by: eheupel marsh periwinkle Tony Weeg/Creative Commons. Atlantic Ribbed Mussel

10 Field Work: Sediment cores Infauna and Sediment Quality Determined sediment nutrients, grain size, organic matter Collected, sorted, and identified 574 infauna cores

11 What infauna are in the sediment cores Deposit feeders - ingest sediment & digest associated bacteria, microalgae & organic matter Suspension or Filter feeders - feed on algae & detrital particles suspended in the water Credit: Chris Dungan / MDNR Tellina agilis Tellin Clam Small thin-shelled clam Macoma balthica Baltic Macoma Clam Abundant in the Bay Tagelus plebeius Stout Razor Clam Used as crab bait, in decline Gemma gemma Fingernail Clams One of the smallest known bivalves Jenny Dreyer, VIMS Nereis succinea Corophium lacustre Common Clamworm Slender tube-builder amphipod Polychaete = "many bristles" Favored fish food

12 Assessing Ecosystem Services shoreline stabilization Primary production Marsh plants Sediment Organic carbon LS Marsh LS Marsh (at least not yet) Living shorelines had comparable plant density & height as natural fringe marshes Living shoreline sediments do not yet reflect organic carbon content of natural shorelines

13 Assessing Ecosystem Services shoreline stabilization High Resolution Shoreline Profiles May 2011 September 2011 (after Hurricane Irene) Trimble R8 GNSS Model 2 Real Time Kinematic (RTK) GPS System South River East River Marsh-sills: Sediment gain immediately landward & seaward of the sills *Red = Deposition, Blue = Erosion

14 Assessing Ecosystem Services ecological trade-offs Intertidal Macrofauna Natural Structure Trade-off with marsh-sill construction Possibly water filtration with sediment bioturbation/nutrient cycling Credit: Chris Dungan Ecosystem Service providers Infaunal deposit feeders U.of British Columbia Clymenella torquata bamboo worm Suspension/filter feeders -feed on algae & detrital particles infauna suspended in the water -Filter water, improve clarity Tagelus plebeius Stout Razor Clam -ingest sediment & digest associated bacteria, microalgae & organic matter -Bioturbation of sediment increase oxygenation Suspension & nutrient cycling Oysters & mussels-sill epifauna mussels marsh

15 Assessing Ecosystem Services ecological trade-offs Intertidal habitat LS intertidal macrofaunal communities LS intertidal = hybrid of riprap & flat Infauna community similar to flats, except reduced deposit-feeders Addition of epifauna & filtration capacity Reduced infauna compared to Marsh, but similar community structure Converted Intertidal Existing Subtidal Habitat Trade-off of subtidal conversion to LS intertidal Replacing shallow subtidal with intertidal reduces infauna abundance, biomass & diversity Loss of suspension, interface and deposit feeders Gain in epifauna offset loss of infauna filtration capacity? Bioturbation = loss; nutrient-cycling?

16 Summary Marsh-sills better than riprap maintains the intertidal and upland connections Marsh-sill intertidal macrofaunal community = mixture of riprap & tidal flat assemblages Living shorelines may be following created wetland trajectories of ecosystem development Plants develop faster than biogeochemical processes (OM, nutrient accumulation) & infauna (> 10 yrs) Habitat conversion means ecological trade-offs loss of infauna biomass and diversity (temporary?), possible gain in filtration capacity by epifauna but very site dependent U.of British Columbia Some Take Homes: Minimize project footprint where subtidal shallows are limited Continue to modify designs to incorporate natural elements (e.g., testing of mussel planting with biologs - Lafayette Wetlands Partnership, Kevin Du Bois) Begin to incorporate nontraditional wetlands measures for LS monitoring e.g., epifauna counts easy and inexpensive

17 PERILS OF FIELD WORK (IN MARYLAND) 2010 Toilet water May 2011 Flooding & Toxins Swimming in Md. Rivers Can Be Worse Than a Dip in the Toilet - By Kate Yanchulis Swimming in the rivers that feed the Chesapeake Bay after a hard rain could be as hazardous to your health as hopping into an unflushed toilet. Date 7/21 7/28 8/04 8/11 8/18 Almshouse Ck ,510 Tropical Storm Lee causes flooding across East Coast Washington Post The remnants of Tropical Storm Lee caused torrential downpours across the East Coast, as rivers swelled past flood levels, roads closed, and thousands were forced to evacuate South River Federation Data Greater than 104 cfu/100 ml are considered elevated bacteria levels!!! Creosote

18 Thanks!! David Stanhope Kory Angstadt Pam Mason Dawn Fleming Molly Mitchell Kirk Havens Karen Reay Karen Duhring Sharon Killeen Cielomar Rodriguez Harry Berquist Kevin O Brien Randy Chambers Tim Russell Matt Johnston Special thanks to Jana Davis, CB Trust Kurt Mantay, CB Trust Walter Priest, NOAA Stephen Hult, London Town Mrs Teague, Poplar Grove