Eelgrass:The Big Picture

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EelgrassThe Big Picture
Frederick T. Short Research Professor
Department of Natural Resources and the
Environment
Jackson Estuarine Laboratory University of New
Hampshire
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• Eelgrass
• Zostera marina L.
• A seagrass
• vascular plant
• flowering
• root system

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Eelgrass and its role

• Form and physiology make eelgrass plants unique
• Functions and values make the habitat important
• Indicator of the health of the Coastal Zone
• Critical maintenance of the coastal waters
• Many current threats
• most of human origin
• Major stress factors
• poor water clarity
• overuse of coastal zone
• Conservation and protection needed
• improve water clarity
• reduce nitrogen inputs
• reduce physical damage

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Eelgrass Plant

• What eelgrass requires
• Clear water (a lot of light)
• What eelgrass prefers
• Cool temperatures 0 - 25 C
• Seawater to estuarine salinities
• Sandy to muddy bottom
• And what eelgrass tolerates
• Moderate pollution
• Many human activities

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Global Distribution of Zostera marina L.
Global Seagrass Atlas 2003
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Great Bay, New Hampshire
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Global seagrass decline
58 of sites declining
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Ecology of Eelgrass
SUBMERGED Subtidal and Intertidal MARINE Low
Salinity to Ocean Water FLOWERING Pollination,
Fruits and Seeds DISTRIBUTION Temperate
to Arctic NUTRIENT CYCLING In Sediment and In
Water Column
ESTUARINE FILTRATION Nutrients
and Sediments FOOD RESOURCE Waterfowl Inverteb
rates HABITAT Breeding Nursery Feeding Protec
tion INDICATOR Ecosystem Stress Pollution
Environmental Health
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New Bedford Harbor, MA
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Piscataqua River. NH 2004
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Flowers
Eelgrass
Fruit
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• 7 months of growth

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Tidal Range of Eelgrass Meadows
gt11 m
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Cape Cod, MA
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Maquoit Bay, ME
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World Atlas of Seagrasses 2003
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LEAF
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Cell Structure
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Photosynthesis
O2
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Penobscot Bay, ME
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WASTING DISEASE LOSS Labyrinthula zosterae
1986
1987
Great Bay, New Hampshire
under a microscope
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Wasting Disease Effect on Photosynthesis
Ralph and Short 2002, MEPS
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Low salinity impact on leaves
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Low Salinity Impact
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Impact of Salinity on Eelgrass Biomass
Moore, et al. in review
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FUNCTIONS VALUES

• 1) improves water quality
• 2) provides nursery habitat
• 3) shelter from predation
• 4) supports food web
• 5) supports fisheries

1) primary production 2) nutrient uptake
storage 3) oxygen production 4) habitat
structure 5) benthic production 6) filtration
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Lasell Island, Maine
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Fishing Island, Maine
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Eelgrass at deep edge
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SET(sediment elevation table) Measurements
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World Atlas of Seagrasses
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Year 1 Typical Year
20 August 2002
Fishing Island Eelgrass Meadow, Portsmouth Harbor
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Year 2 Habitat Loss
8 September 2003
Fishing Island Eelgrass Meadow one year later
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Geese eating eelgrass
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Causes of Current Eelgrass Decline

• Reduced water clarity
• Nutrient loading
• Sediment loading
• Siltation from dredging
• Cumulative impacts
• Physical Damage
• Fishing
• Aquaculture
• Dredge and Fill

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NHState of the Estuary Report 2006
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Water quality and light
Good
Fair
Awful
Poor
death
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Eelgrass daily growth at 2 meters depth for 9
days in July with different light extinction
values (K) replotted vs. light.

• Short, F.T., D.M. Burdick and J.E. Kaldy. 1995.
  Mesocosm experiments quantify the effects of
  eutrophication on eelgrass, Zostera marina L.,
  Limnology and Oceanography 40740-749

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Poor Water Clarity
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Eelgrass Monitoring Shows Decline in Spatial
Coverage and Biomass
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Tidal Effects on Light Reaching Eelgrass
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5.8
3.2
1.0
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Eelgrass Decline in Ninigret Pond, RIvs. Number
of Houses
World Atlas of seagrasses 2003
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Seaweed
Nutrient Enrichment gt Algae
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Great Bay Estuary Restored Eelgrass
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New Bedford Eelgrass Restoration between TERFS
after 4 years
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Causes of Current Eelgrass Decline

• Reduced water clarity
• Sediment loading
• Nutrient loading
• Siltation from dredging
• Cumulative impacts
• Physical Damage
• Fishing
• Aquaculture
• Dredge and Fill

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Moorings and dredging
Little Harbor, New Hampshire
Sept 2003
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Fishing boating activities
Narragansett Bay
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Great Bay, New Hampshire
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Trawling
Maquoit Bay, Maine
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PORT EXPANSION / DREDGING
New Hampshire
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Great Bay, New Hampshire
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Eelgrass and its role

• Eelgrass is a unique plants
• Functions and values make important habitat
• Indicates the health
• Critical maintenance of the coastal waters
• Many current threats
• most of human origin
• Major stress factors
• poor water clarity
• overuse of coastal zone
• Conservation and protection needed
• improve water clarity
• reduce nitrogen inputs
• reduce physical impacts

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Now we must move from science to policy
politics if we want to save the eelgrass
resource.