Eelgrass Creates

Safer Waters

Nitrogen pollution creates dangerous conditions in Long Island Sound. Eelgrass acts as a critical buffer to prevent disastrous consequences

What is Nitrogen Pollution?

Nitrogen is a naturally occurring limiting nutrient in marine ecosystems. When marine systems gain access to nitrogen, it stimulates growth. Nitrogen pollution occurs when humans dump excess nitrogen into water systems. There are three sources of nitrogen pollution.

  1. Fertilizer

  2. Human Waste - Sewage, Septic Systems, and Cesspools

  3. Fossil Fuels

Nitrogen pollution fuels algal blooms that can shut down beaches, create low oxygen zones, and kill fish. These blooms can harm humans and block the light available to seagrass. Shade crushes seagrass's ability to cycle the nitrogen out of the marine system.

Eelgrass Absorbs Nitrogen

Nitrogen is essential to plant life; eelgrass absorbs ammonium and nitrate through its roots and leaves [1]. The short-term retention of nitrogen in eelgrass can last for weeks to months, much longer than the algae retention time of days [2]. Short-term nutrient retention creates an important coastal buffer to slow nitrogen flow into oceanic habitats. These buffers prevent anoxic conditions caused by pelagic nitrogen-fueled phytoplankton blooms [3].

Eelgrass Decomposes Slowly

The decomposition of shed leaves or dead plants is a natural part of the life cycle. Eelgrass has more structural tissue than microalgae and bloom-forming macroalgae, so eelgrass decomposes at a slower rate than these algae [4]. A slower decomposition rate allows eelgrass to retain the nitrogen in its tissue for up to two years, primarily through its roots and rhizomes [5].

Eelgrass Traps Nitrogen in Sediment

Eelgrass beds reduce water current speeds, which promote nitrogen-rich particles to settle on the seafloor [6, 7]. Microalgae that live in seagrass sediment further stabilize these particles by secreting a biofilm that traps them in place seasonally [8]. In the fall and winter, eelgrass goes dormant, and the microalgae in the sediment become less active. During these seasons, nitrogen in the sediment is resuspended [5]. This seasonal nitrogen buffer prevents the pollution from rushing into Long Island Sound all at once.

Without Eelgrass…

Destruction of eelgrass habitat has disastrous consequences. Microalgae, phytoplankton, and short-term macroalgae take the place of eelgrass. These invaders have higher nutrient content and less structural stability than eelgrass which will lead to a shorter nitrogen buffer between coastal and oceanic habitats.

Furthermore, blooms can cause anoxic - zero dissolved oxygen - or hypoxic - low oxygen - zones due to the high oxygen demand from decomposing organic material. These habitats are not suitable for much marine life including eelgrass. This is a vicious cycle that creates difficult conditions for eelgrass to rebound from nitrogen pollution. Commercial and recreational fishers will also suffer the effects of eelgrass loss as the habitat that their catch depends upon is lost. Divers and snorkelers will not have beautiful meadows full of fish and shellfish to observe either.

If you are still unconvinced that eelgrass loss is destructive, consider that microalgal and phytoplankton blooms have been toxic to fish and humans. These blooms lead to lengthy beach closures and terrible smells as the blooms rip through ecosystems.