Timeline

  • Spring 2016 (siphon on)
    • Stable isotope data for four natural marsh sites at varying distances from the siphon.
  • Spring 2018 (Siphon off)
  • Spring 2019 (Siphon off)
  • Spring 2020 (Siphon on), but collections delayed to 2021

Hydrology and Elevation Mapping

(Swenson/Polito)

Key Findings

  • Correlation among sites is high for all parameters, temperature, conductivity and marsh water level.
  • Most (70%) of the differences between the 2019 and 2018 elevation surveys were fairly small (<5 cm) with 74% of the 2019 elevations being higher
  • The percentage of the day that a marsh is flooded is correlated with the daily mean water level for CRMS3680.
  • The percent marsh flooding can be calculated from measured water level (in m NAVD88) using a logistic sigmoid growth model.

(Note: CRMS3680 is the index station)

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Primary Producers

(Roberts)

Field Work: May 2018 & 2019

  • 5 distances from edge (1, 10, 25, 50, 100 m)
  • 3 transects in 2018; 2 plots on single transect in 2019
  • Determine biomass (aboveground clip plot) and collect plants for biomarkers)
  • Sediment and water column chlorophyll
  • Ancillary data: organic matter, C and N, bulk density, water content, pore water salinity, pH)

Key Findings

  • Overall magnitude of aboveground biomass similar between years; no consistent pattern with distance.
  • Trend of decrease along salinity gradient in 2018, weaker in 2019.
  • Biomass lower in high elevation restored marsh (LHA) than natural marsh(LHC); Biomass in restored marsh (LHB) more similar to the natural marsh (LHC).
  • Overall aboveground richness similar between years.
  • Richness decreases with salinity.
  • Richness lower in restored marshes than control sites in 2018; species richness was similar at lower elevation restored marsh (LHB) and natural marsh (LHC) compared to the higher elevation restored marsh (LHA) site.
  • Many species in one of the restored marshes (LHA) were not typical of brackish wetlands.
  • No clear patterns in benthic chlorophyll by site or distance.
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Litter Bag Decomposition & Macroinvertebrates

(Lopéz-Duarte, Polito, Roberts)

Field Work: May & July 2019

  • 1 transect per site, 5 distances from edge (1,10,25,50,100*m)
  • 5 replicate Spartina alterniflora litter bags per distance deployed for 2 months

Key Findings

  • Spartina alterniflora decomposition is highest in marshes that are flooded more due to lower elevation and a larger tidal range
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Microbial Community

(Engel)

Key Findings

  • Created marsh soils are fundamentally different than natural soils: lack well-developed peatlayer, wider grain size distributions (and larger overall particle sizes), less organic carbon.
  • Distinct microbial communities within soils, which affect the types of metabolic processes and microbial community services that influence the marsh habitat through time.
  • Overall taxonomic diversity similar, but specific genetic groups differed between created & natural marshes
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Sediment core collections. Left: from sandy dredge deposits at Lake Hermitage marsh creation site. Right: organic, mud rich sediments from natural marshes. Credit: Annette Engel.

Insects and Spiders

(Hooper-Bùi)

Field Work: May 2019

  • Emergence traps set Day 1, collected Day 8
  • 4 replicate sweeps at each site for biodiversity
  • 4 replicate sweeps at each site for isotopes

Key Findings

  • Not all works all the time. We placed emergence traps on the marsh platform on the first day. We collected insects via sweep net for biodiversity and community metrics. Another identical sweep sample was taken 5 m away for the insects for isotopes.
  • This is the second year (2019) we set the emergence traps. Last year (2018), there were a few insects – flies – in the emergence traps but not enough for isotope analyses. There were no insects in the emergence traps this year, likely because May may be too early in the year. One trap blew into the water on day 3 and was retrieved by the fish group. We added asecond collection of sweeping for isotopes to make up for the low numbers of insects in the emergence traps.
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Benthic Infauna

(Rabalais)

Field Work: May 2018 and May 2019

  • 1 transect per site (middle), 2 distances from edge (10 m, 50 m)
  • 5 replicates infauna, TOC, grain size
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Trawl and Suction Sampling

(Martin)

Field Work: May 2018 and May and July 2019

  • 8 trawls/site in years 1 and 2
  • Year 1 suction, n = 10 at salinity gradient sites
  • Year 2 suction, n = 9/site

Key Findings

  • Trawl: Clear differences between years, sites
  • Nekton community varies among sub-habitats (ANOSIM, Global R=0.333 , p=0.001). Biodiversity is highest in ponds at natural marshes.
  • We identified a need to incorporate site-specific data (e.g., pond sizes, marsh height) to determine which drivers influence community structure in ponds, creeks, or edges, across sites
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Biomarkers

(Polito, Olin, Lopéz-Duarte)

Field Work: May 2019

  • Collected ~2000+ sample in 2018 & 2019
  • Fish, invert, plants, submerged aquatic vegetation, algae, benthic microalgae, soil organic matter, particulate organic matter

Lab Work

  • Processed 1800+ samples from 2018
  • C&N isotopes: 2016 & 2018 complete
  • Compound-specific: 2016 complete
  • Heads collected for otoliths

Key Findings

  • Aquatic basal carbon sources are more important than terrestrial at all sites.
  • Similar trophic level but slightly higher use of terrestrial carbon at natural sites relative to created sites.
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