Why we should we anchor outside of eelgrass beds?
During this 2023 season, we are asking boaters to anchor outside of eelgrass beds and addressing the barriers to boaters completing this task. So why are we asking you to look before you drop? Let’s find out!
When we anchor inside eelgrass beds, we damage the marine ecosystems that we come to Fishers Island to enjoy. To prevent this damage we always look for eelgrass before we drop our anchor!
Anchors rip eelgrass out by the roots.
Most of the damage from anchors around Fishers Island is caused by the anchor fall and retrieval [1, 2]. The initial damage occurs when the spikes of the anchor dig into the sediments - as the anchor is dragging to secure the boat, it is scarring the bed and eventually digging deep into the roots of the seagrass bed. When removed, the anchor yanks at the root and rhizome mat, pulling the entire plant out of the sediment. Once these plants are ripped out, they will not replant themselves. Depending on the anchor's size and the seagrass bed's density, the bare patch that a single anchor leaves range between one and four square meters [3].
Because most anchoring around Fishers Island is short-term, the long-term consequences of anchor ropes and chains are less concerning. However, moorings are concerning in this respect, and you can discover more about that here.
Then sediments cloud the water column.
The shoots, roots, and rhizomes form an intricate system that recruits fine sediments and organic particles. Anchors tear a hole in the system that holds down the sediments [3]. Without the shoots decreasing the effect of erosion, natural waves and tides begin to loosen the silt and nitrogen in these bare patches. These bare patches are also newly susceptible to boat wake turbulence because of how easily the sediments can be disturbed [4]. Anchors also rip a hold in the rhizome mat that secured carbon in the sediments and prevented it from releasing into the atmosphere.
Fine silt and organic particles stay suspended in the water column longer than coarser particles. Because they take so long to settle back on the seafloor and are so easily resuspended, the eelgrass suffers even more from the decreased access to light they require to photosynthesize.
To add to this damage, the resuspended nitrogen will fuel phytoplankton and algal growth, leading to large and uncontrolled blooms that can harm human recreation and fish populations.
Nitrogen-fueled algal blooms can impact recreational plans and destroy fish populations by creating low oxygen zones.
Regrowth takes years.
Eelgrass can recover from the damage an anchor creates in many cases, but this process takes approximately three years [5]. For context, that means the damage a single boat caused to an eelgrass meadow around Fishers Island in 2020 would finally return to full health this year. But most boaters to Fishers Island come out and anchor about ten times per year. That means that one boater could create, on average, ten bare patches in one year. So 2020’s damage may be recovered this year, but there could still be 20 bare patches recovering! Because this damage is cumulative, each boater must understand that they can substantially impact this ecosystem.
The three-year regrowth scenario is best-case. Sometimes, recovery is impossible because of outside environmental factors [6]. Some eelgrass beds grow in less protected enclosures than harbors or inlets in the coastline. That means they are working very hard to hold down the sediments and prevent coastal erosion, but if the anchoring pressure is hard enough, the bare patches can result in severe erosion and coastline loss. The remaining eelgrass will die from sediment burial and excessive shading resulting in disrupted photosynthesis.
As we wait for the eelgrass to regrow, the marine habitat suffers.
Eelgrass supports complex and diverse marine life, just like coral reefs. When eelgrass disappears or depletes, the bare sand it leaves behind cannot support the creatures that depend on the plants [3]. Marine animals within these meadows depend on the complex structures to provide shelter from predators, habitat for juveniles, and food for grazers. The complexity of the meadow relies on the density of the shoots, the continuity of the habitat, and the length of the grass blades [7, 8]. Anchoring directly disrupts all three of these key factors. Even as the bare patches in the meadow regrow, the shorter, sparser blades cannot support the life they could have before the anchor caused damage [2].
The small-scale repetitive habitat loss has cumulative, negative effects on marine life [9]. The bare patches from anchors leave areas that deplete the amount of life that the eelgrass can support. As the meadow accumulates additional patches through a year, its habitat capacity declines. Because our eelgrass sustains the fisheries around Fishers Island, in Long Island Sound, and the Atlantic, its degrading habitat destabilizes commercial and recreational fisheries. This will have a significant economic impact on commercial fishers and their consumers. Furthermore, recreational fishers will be disappointed by the low take limits and limited length of the fishing season.
What can we do?
Before dropping anchor, check for eelgrass off the side of your boat. It is that easy!
The good news is that eelgrass is very easy to spot. Because eelgrass grows in shallow water of 30 feet or less and contributes to sediment stability, the clear water enables boaters to see eelgrass beds over the side of the boat. If you see eelgrass, please move your boat out of the eelgrass bed before you drop your anchor. This simple task will help us Save Our Seagrass for generations of enjoyment!
