WP2 Field test

Field tests of restoration techniques and monitoring.

The major results in the REELGRASS project were the discovery of several processes
preventing the reestablishment of eelgrass (Flindt et al. 2011). Unconsolidated sediment that
allows for insufficient anchoring of seedlings was among the problems. Thus areas covered
with muddy sediments may temporally lose their ability to support eelgrass. Likewise, intense
disturbances from wave and current action, drifting macroalgae and macrofaunal sediment
reworking also inhibits recovery by causing high seedling loss (Valdemarsen et al. 2010).

Optimal sites for eelgrass restoration efforts in selected estuaries will be chosen based on
simulation results from dynamic models and GIS-tools (WP 4). We will choose and examine
sites with different eelgrass loss/recovery histories. Various approaches designed in WP 1 will
be further developed and tested at these sites through field manipulations to optimize
sediment conditions and to minimize current and fauna derived disturbances.
Preliminary studies in the laboratory have shown that muddy sediment can be
consolidated with sand, but field evidence is still lacking. We aim at testing sediment
consolidation and protection of seedlings from physical stress until they have developed selfsustainable
patch sizes. The field designs will include sediment stabilization by sand capping,
benthic fauna removal by applying protective mats on the surface, and protection against
currents and drifting algae by establishing shields in the direction of dominating winds.

These key recovery techniques for establishing self-sustainable flowering patches in
previously unvegetated sub-locations of estuaries will be based on the discoveries from WP 1
during the first year and implemented subsequently. Their effects on eelgrass recovery and the
succession of the associated biological communities will be monitored through frequent flora
and fauna samplings as well as water quality measurements (nutrients, turbidity and light
penetration) during the following years. The results will be evaluated in close collaboration with
the industrial partners to optimize the development of large-scale restoration techniques in WP
5. The field results will also be available for the development of models in WP 4 for simulation
of ecosystem behavior after implementation of various key recovery techniques.