Week 13 - Eelgrass

Question 1

Eelgrass in Estuaries

Answer 1

Eelgrass forms dense beds in the subtidal zone, supports a diverse fauna and flora, and acts as a nursery for fish and shellfish

Question 2

Eelgrass

Answer 2

Eelgrass is a common name for a group of plants, genus Zostera spp.

Zostera marina is native, and most common, with several ecotypes.

Grow underwater within the photic zone in estuaries and shallow coastal areas

Grass-like plant, ribbon-shaped leaves 20-50cm in length (exceptionally up to 2 m)

Leaves and rhizomes have air spaces called lacunae

Question 3

Eelgrass Biology

Answer 3

It is a rhizome-structured plant

Reproduce vegetatively from rhizomes below the surface

Leaves shoot from creeping rhizomes

Single plant may have multiple shoots hidden below the surface

It is also a perennial Angiosperm

One of the only flowering marine plants

Flowering in early February

Pollinates by flowers hidden beneath a transparent leaf sheath releasing long
filamentous pollen into the water

Question 4

Eelgrass characteristics

Answer 4

Density and morphology vary by depth, wave exposure, substrate, water clarity

Density in intertidal has been observed at 500 shoots / 0.25 m2

Density can serve as guideline to determine if a restored bed is approaching reference conditions

Question 5

Eelgrass distribution

Answer 5

in estuaries, bays, lagoons, and other marine environments where water is clear and light is plentiful

shallow salty waters with muddy or sandy bottoms in most of the world’s coastal temperate regions except at extremely high latitudes.

from Alaska to Australia, in the Chesapeake Bay and off the coasts of Florida, California, and coastal areas of Europe and Asia

Question 6

How Deep Does Eelgrass Grow?

Answer 6

Found growing within a meter of water, and at depths >30 m if water is especially clear

Depends on physical and chemical factors
1. the amount of light available*
2. water clarity
3. water temperature
4. salinity (10-30ppt)*
5. pH
6. elevation*
7. substrate*
8. wave action

Light availability is believed to be primary factor limiting depth distribution, density and productivity of eelgrass meadows

Question 7

Why Eelgrass so important

Answer 7

Among the most productive and biologically diverse ecosystems on the planet

Surface area for >350 sp. of macroalgae and 91 sp. of epiphytic microalgae
-Padilla Bay, WA, study showed biomass of macroalgae associated with eelgrass was greater than eelgrass shoot biomass

Question 8

Ecological Services and Functions of Eelgrass

Answer 8

prevents erosion and maintains stability nearshore by anchoring sediment with its spreading rhizomes

wave attenuation

promotes deposition of suspended particles

improves water clarity, which subsequently increases eelgrass production

increases productivity through increased photosynthesis in clear water, energy transfer up the food chain

removes excess nutrients

provides food, breeding areas, and protective nurseries for fish, shellfish, crustaceans and many other animals

Question 9

Ecological Significant Species (ESS)

Answer 9

DFO has designated eelgrass as an ESS

Acknowledging its unique influence on the ecology of sand and mud flats in Canada

No legal protection, but intended to bring attention to its high ecological significance and promote a greater degree of risk-averse management

regarding any human activities that may impact eelgrass or its community properties (Coll et al 2011)

Question 10

Eelgrass as food

Answer 10

As a primary producer, eelgrass forms the base of a food web

= Carbon Currency in the estuary

high cellulose content so not many animals graze it directly

Main food value is as detritus - bacteria, worms, crabs graze it directly, then pass up to other animals

Organisms depend on it directly and indirectly:
some water fowl, snails, urchins, lobsters, crabs, scallops, jellyfish, sea anemones, flounder, and many other fishes

Question 11

Human impacts on Eelgrass

Answer 11

1. Dredging and filling
2. Excess nutrient loading and chemical contamination
3. Logging
4. Land development
5. Oil spills
6. Docks
7. Anchoring
8. Boat propeller cuts
9. Invasive European Green Crab

Question 12

Factors influencing success in Eelgrass restoration

Answer 12

Factors that influence the success of eelgrass transplants primarily
related to:
 Proximity to natural eelgrass bed
 Site selection (including substrate, depth, current or wave disturbance)
 Quality of donor stock
 Light energy
 Salinity
 Temperatur

Question 13

Eelgrass Transplant procedure

Answer 13

1. Assess the reference and donor site for the proposed eelgrass transplant
2. Select donor plants with similar morphological characteristics that will survive in the new location
3. Obtain the necessary permits from DFO (and BC-WLRS / BC Parks if required). Arrange for volunteers to collect eelgrass donor stock and hire SCUBA divers for planting
4. Assemble your equipment and eager team
5. Attach a ~12 mm dia. non-galvanized steel washer to each plant near the base with a twist tie, and place in seawater tubs, in preparation for the divers to plant
6. Try to remain enthusiastic while your hands freeze and your mind wanders…..
7. Lay down quadrat, setting up, diver uses trowel to cut slot into sediment and inserts rhizome mersitem, plot after planting
8. Monitor the effectiveness of your transplant for up to 5 years, and apply adaptive management to learn and improve your transplant effectiveness