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Eelgrass Research
By Dante Torio

Eelgrass Research Approach

  • Traditional Ecological Knowledge as our guide.

  • Listening to what the elders are saying about eelgrass, its state, waterfowl feeding behavior, and meat quality.

  • “Before (i.e., 1975), geese and other waterfowl were too fat to fly after eating eelgrass; now they are skinny and do not eat eelgrass anymore.”

  • “Eelgrass was dark green, clean, and as long as boat paddles; now they are black, short, and slimy.”

  • “Our faces were full of salt when we traveled out of the bay, not anymore.”


Eelgrass Ecology

•Eelgrass is one of the 16 kinds of underwater flowering plants widely known as seagrass.

•Eelgrass or Zostera marina in Latin or SHIKAAPAASHKWH in Cree, grows in the cold regions of the northern hemisphere.

•Peak growing season in James Bay is in September.


Eelgrass DNA (Olsen et al. 2016)

Very resilient

  • has genes for freshwater and saltwater tolerance 

  • get nourishment through leaves and roots

  • resistant to infections 

  • adapted to low light (turbid) conditions

  • adapted to drying and osmotic stress (water imbalance) during low tide mainly due to the high concentration of sugar and pectin (gelatin-like substance) in its tissues

  • Resistant to toxic heavy metals

UV susceptible

Eelgrasses are sweet

  • 90% of eelgrass plant matter is sucrose (ordinary table sugar)

  • Eelgrass is considered as ‘marine sugarcane.’

  • Sugar is used by eelgrass in osmosis to draw fresh water in and leaves the salts out

  • The higher the salinity of water surrounding eelgrass, the sweeter the eelgrass plants


Eelgrass Study Site



CERRI’s Major Findings to Date

Finding 2. Sugar concentration in eelgrass is reduced by a high concentration of nitrogen in the water

  • The more nitrogen in the water, the less sweet the eelgrass

  • Sources of excess nitrogen in the water includes:

  • Fertilizer, animal, and plant matter from the atmosphere

  • Excess nitrogen can cause growth of bacteria and algae


CERRI’s Major Findings to Date

Finding 4. The severity of dead eelgrass leaves was related to the following:

  • Excessive amount of impurities (Total Dissolve Solids), i.e., organic matter and minerals (e.g., calcium, silica, magnesium, iron, etc.) in the water column

  • TDS increases as you go south of the sampling areas


More on these Cocconeis

  • It seems like silica is related to the plume

  • There are more cocconeis in marginal eelgrass than healthy ones


Where do Cocconeis get their silica?

  • Cocconeis and other diatom multiply because of excessive amounts of dissolved silica (from sand, rock, and silt)

  • Silica is released from detrital materials (clay, sand, and rocks) when these materials interact with seawater and wave action (Mackenzie and Garrels 1965, Fabre et al., 2020)


Putting them together

  • There's higher silica along the La Grande plume


CERRI’s Other Major Findings to Date

  • Marginal eelgrass areas are also infested by cyanobacteria (a noxious type of blue-green algae)

  • Impacts: Cyanobacteria competes with eelgrass for light and space

  • Decaying bacteria produce noxious gases and toxins


Western Science + Traditional Ecological Knowledge

•TEK guides what, when, and where to gather data  (indicator species, locations, peak growing season).

•TEK + Western science develop questions and hypotheses.

•What is in the eelgrass that makes geese fat?

•Why did geese stop eating eelgrass?

•What causes eelgrass to turn black, short, and slimy?

•Can we bring eelgrass back to their previous (1975) state.

•Western Science helps how to collect and analyze data.

•WS and TEK co-develops insights.


Eelgrass Biology

•Eelgrass reproduce through seeds and young shoots.

•Both annual and perennial types.

•Freshwater lineage but fully adapted to marine conditions.

•Grows best in soft sediments(70% silt: clay).

•Shallow environments (0.33- 2.4 meters).

•Wide tolerance to salinity (2-20 PSU).

•tolerate temperatures between -1 to 25 °c.


Current science on eelgrass decline and recovery

USA, Puget Sound, 40 years of monitoring

  • Wasting disease, recovered

  • Resilient to Global

  • More vulnerable to local factors  

Australia’s massive and long-term seagrass decline.

  • Smothering of fine sand from eroded and deforested areas.

  • Nutrient inputs to the bay (dead plant materials and fertilizer).

James Bay.

  • Decline in the early 90s

  • Slow to no recovery


CERRI’s Major Findings to Date

Finding 1. We found a link between goose fat content and eelgrass sugar!

  • The kind of sugar (e.g., sucrose) that is in eelgrass is the form that is easily digestible and provides energy

  • Migratory waterfowl requires a tremendous amount of energy stored as fat for long flights during migration

  • Among known geese plant foods in James Bay, eelgrass had the highest sugar content.


CERRI’s Major Findings to Date

Finding 3. Reference sites have sweeter eelgrass than marginal sites.

  • Eelgrass was sweeter in areas where Weewobwaow (Brant’s Goose)  were feeding

  • Sites where Weewobwoaw were feeding, had fewer Cocconeis


CERRI’s Major Findings to Date

Finding 5. Eelgrass leaves were infested by slimy, tiny, scale-like creatures called Cocconeis

  • There are two kinds of them Cocconeis scutelum and C. placentula

  • The shell of these Cocconeis are made up of pure silica


How Cocconeis affect eelgrass

What does Cocconeis do to eelgrass

  • Prevent light from reaching the leaves (less sugar produced, therefore less sweet eelgrass)

  • discourage geese and other animals from eating eelgrass leaves (Sieburth and Thomas 1973)

  • make the leaf surfaces hot during the day and choke the leaves with toxic gas during the night (Noisette et al. 2020)

  • Transmit UV radiation to the leaf surface killing the plants (De Tommasi et al., 2018)


The La Grande River Plume

  • Patterns of dissolved organic matter plume from La Grande  detected by satellite


Other minor findings

  • Eelgrass closer to the land and in sheltered bays is in a better state compared to more offshore eelgrass.


Implications of CERRI findings

  • Sugar provides the vital link between geese and eelgrass

  • Excessive amounts of impurities in coastal waters resulted in more dead eelgrass leaves

  • Infestation by Cocconeis resulted in reduced photosynthesis, thereby reduction of sugar in eelgrass

  • Heavy Cocconeis presence in leaves could be preventing geese from feeding on eelgrass

  • Silica is likely coming from effluents from major rivers such as La Grande, and they are being released as they interact with salt water.

  • There is enough evidence showing that Cocconeis presence, competition with cyanobacteria, and impurities in coastal waters have resulted in eelgrass decline.

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