Seagrass: The Decline

Over the past fifty years, North Carolina has lost over fifty percent of its seagrass populations₄. This alarming rate of decline is believed to be caused by a multitude of factors, including eutrophication, turbidity, erosion, extreme climatic events, dredging and boating, and invasive species (See Figure 3)₇.  

Marine scientist Pat Garber argues that the primary cause is eutrophication, which occurs when runoff from the mainland suffocates the seagrasses with excessive nutrients, sediment, and waste. She also claims that erosion caused by poor land-use practices, watershed deforestation, and coastal clearing has damaged the seagrass beds₄.

Meanwhile, researchers at CSA Ocean Sciences, an international marine environmental consulting firm, believe that there is a causal relationship between powerful wave energy and the withering seagrass beds₂. Not only do strong water currents tear apart seagrass patches, but they also increase wave turbidity. Turbid water has a high concentration of inorganic material that prevents sunlight from reaching the seagrasses inhabiting the ocean floor, thus hindering seagrass growth.

Other researchers have blamed climate change, attributing the decline in seagrasses to the warmer water temperatures and reduced sunlight. In these inclement conditions, root and leaf development are weakened and internal carbon and nitrogen compositions are altered₄. With climate change also comes an increase in extreme weather events, such as floods and hurricanes, that destroy seagrass beds ₇.

Still others assert that the problem is rooted in commercial boating and fishing activities. Anchors, nets, and propellers all cause disturbances in coastal ecosystems, thus damaging the seagrasses’ natural habitat. Dredging, or the excavation of material from a water environment, is also believed to harm the seagrass beds by displacing their underlying sediment₇. Some marine scientists have also hypothesized that invasive species of foreign plants, animals, or microbes are negatively impacting seagrass health₇. 

While there is still general disagreement about what the exact cause of the decline in seagrass populations is, the one thing that everyone can agree on is that North Carolina’s seagrasses are rapidly disappearing – and we all need to do our part to help save them.