Image by Jacob Banting
If you’ve spent time boating in the Salish Sea, you’ve probably cruised over eelgrass, maybe even without realizing it. These underwater meadows cover much of the shallow waters and estuaries, creating some of the most important marine habitats in the region.
What is eelgrass?
Although many people think eelgrass is a type of seaweed, it’s actually a flowering plant that has adapted to live entirely underwater, where it even blooms and releases pollen. While seaweed is algae that often attaches to rocks or floats freely, eelgrass has true roots and rhizomes that anchor it in shallow seafloor sediments, allowing it to form extensive underwater meadows, which help to stabilize both the plant and the surrounding sediments.
In the Salish Sea, Zostera marina, the native eelgrass species, typically grows at depths ranging from about 3 to 30 feet below the low tide line, depending on the location. When visible from the surface, eelgrass looks like green ribbons gently swaying with the current.
Why should boaters care about eelgrass?
It’s all connected
Eelgrass meadows provide both shelter and food for a wide variety of organisms, playing a vital role in the food web. Baby Chinook salmon hide from predators there, Dungeness crabs forage around the roots, and young rockfish spend their early days among the leaves. The connections go even further because endangered Southern Resident orcas hunt salmon that grew up in these eelgrass nurseries.
When you see a Great Blue Heron standing in the shallows, it is often fishing in eelgrass meadows. This list of marine life that depends on eelgrass goes on. Beyond wildlife, regional food security relies on the fish and shellfish that depend on eelgrass, supporting local communities throughout the Salish Sea.
Natural coastal defense
Eelgrass beds act as natural breakwaters, protecting coastlines much like artificial wave barriers. Their dense root systems stabilize seafloor sediments, preventing erosion from below, while their long, ribbon-like leaves absorb and reduce incoming wave energy before it reaches the shore. This dual protection provides erosion control without the construction costs or ongoing maintenance required by engineered coastal defenses.
Climate benefits
Eelgrass meadows absorb carbon from the water and bury it in seafloor sediments, where it stays locked away for hundreds of years if left undisturbed. When eelgrass beds are damaged, that stored carbon gets released back into the atmosphere, undoing years of climate benefits.
Water quality
Eelgrass beds filter water by absorbing excess nutrients that could otherwise trigger algae blooms and trapping sediments that cloud the water. The result is clearer, healthier water.
The anchoring problem
Since eelgrass beds are often hard to see from the surface, they are especially vulnerable to anchor damage. Anchoring in eelgrass is not only harmful to the environment but also not ideal for your boat. Anchors do not hold well in the soft sand and mud where eelgrass grows, making it more likely that your boat will drift or drag. You will often pull up plant material when retrieving your anchor, which clearly shows damage.
When an anchor drags through eelgrass, it rips up the root system and leaves scars on the seafloor. As your boat sways with the tide and wind, the anchor chain sweeps across the bottom, widening the damage. Small bare patches can grow over time as damaged edges become more vulnerable to erosion. This problem adds up. One boat might create a small scar, but dozens of boats over a season can seriously degrade a healthy meadow.
For these reasons, it is best to avoid anchoring in shallow water where eelgrass grows. Boaters should learn where eelgrass meadows are located in their region to protect these vital habitats and ensure safer anchoring.
Practical boating guidelines
Check before you leave the dock:
- Always check local charts and maps for known eelgrass locations and plan your route to avoid these sensitive areas, keeping in mind that eelgrass distribution varies throughout the Salish Sea, so it is important to consult local authorities for the most accurate and up-to-date information before boating.
- Some areas have designated no-anchor zones or specific depth recommendations that can help you avoid sensitive habitats while finding better holding ground for your boat.
- When you are unsure about an area, stay within marked channels to reduce the risk of damaging eelgrass beds.
- Before your trip, look for available moorings at your destination to minimize the need for anchoring.
Follow these anchoring rules:
- Anchor in at least 25 feet of water at low tide. At that depth, you’re usually clear of eelgrass beds, and your anchor will hold better.
- Use moorings or marina slips when available. You’ll avoid eelgrass and secure a more stable berth.
- Respect voluntary no-anchor zones. These mark areas where eelgrass beds are particularly important or vulnerable to degradation.
Safe mooring for eelgrass
- Moorings with mid-line floats keep lines off the seafloor, protecting eelgrass and reducing sediment disturbance.
- Avoid heavy chains and anchors from scouring the sea floor.
Be mindful on the water
- Slow down in shallow areas or avoid them altogether if possible, as propeller damage can be just as destructive as anchor damage.
- Watch for green ribbons swaying in the water, especially in depths ranging from 3 to 30 feet.
- Sandy bays and estuaries are prime eelgrass habitats.
- During Other Activities
- When swimming, paddling, or beaching, avoid trampling underwater vegetation to protect it.
- Beachgoers can also keep pets on leash near these habitats at low tide.
The big picture
Following these practices helps prevent cumulative damage to eelgrass beds. While individual impacts may seem small, repeated anchor and propeller damage across many boats creates lasting habitat loss.
Anchoring responsibly helps maintain the conditions that make the Salish Sea healthy. When you anchor in deeper water, you’re protecting underwater ecosystems that support salmon runs, filter our water, store carbon, and defend our coastlines. These benefits extend far beyond any single activity on the water.
Visit our partners at the Northwest Straits Commission. Their site, anchorout.org, offers up-to-date resources, interactive maps, and best practices to help protect these vital marine ecosystems: Facebook, Instagram & Threads.