and staying the same
Here’s Why:
Sediment plays a vital role in the Delaware Estuary’s ecosystem. The amount of sediment in the Delaware Estuary’s water has been declining, and its changing concentrations due to human disturbance, storms, and sea level rise still pose challenges requiring further research and monitoring to understand its implications for the estuary’s long-term health.
Have you ever looked at the murkiness of our waters and wondered why it looks like that?
That cloudiness is often from sediment or mud (tiny particles of minerals and decaying organic matter) and holds immense significance for our plants, animals, and landscapes. It is the building material for the estuary’s marshes and shorelines and is where the life on the bottom of the bay and streams takes root. The balance of sediment in the estuary is a delicate dance: too little, and we risk losing essential marshland to rising tides, a concern that is increasingly pressing in our era of climate change; but too much, and we could potentially bury underwater habitats, blocking out light vital for bottom-dwelling plants and smothering developing fish eggs. This section looks at the crucial role of sedimentation, its challenges, and why managing this balance is more imperative now than ever.
Mid-Atlantic estuaries, including the Delaware Estuary, are notable for their ability to trap and store watershed-derived sediments. Only 5 percent of these sediments wash out to sea while the rest stays where it should. This helps paint a picture of estuaries as sediment repositories, far more dynamic and impactful factors are at play that impact sediment processes.
One thing you can count on is that sediment is always moving. Sedimentation is the process in which materials such as decaying plants, animals, minerals, and debris are carried into the water and deposited or settled into a new location. This process is at the core of the Delaware Estuary’s vitality, shaping its landscapes and resilience against climate change. The Delaware Estuary receives a significant influx of sediment from its main rivers, with the Delaware, Schuylkill, and Christina rivers accounting for about 80 percent % of the freshwater flow into the estuary.
Sediments are crucial in maintaining our landscapes that are heavily influenced by water, such as marshes. Enough sediment must reach marshland to maintain its elevation above the rising tides. If sea level rise outpaces the amount of sediment that a marsh can accumulate, marsh’s sediment accretion, the marsh could drown and become risks drowning and converting to open water – resulting in lost an event that would result in lost coastal habitats and increased vulnerability of flooding and storm damage in coastal communities to flooding and storm damage. This scenario is particularly relevant in our era of climate change, with the tidal region of the watershed feeling the brunt of the impact.
Turbidity is sediment suspended in the water – a delicate balance in the Delaware Estuary. When you look through highly turbid water, you cannot see fish, plant life, or the river bottom. Fewer suspended sediments in the water allow more light in, thus increasing the ability for algae or aquatic vegetation to grow, which is beneficial. Yet, this could also make the estuary more vulnerable to algal blooms, disturbing the balance.
Urban development can disrupt natural patterns of sediment flow. Similarly, climate change impacts, from more intense storms, or sea level rise, can affect sediment distribution. Even the good intentions of watershed management efforts, which aim to reduce sediment runoff to enhance water quality in upstream habitats, could inadvertently contribute to the declining sediment levels in the Delaware Estuary.
Further research and monitoring are necessary to clarify the reasons for this decline and its long-term implications. Understanding the effects of changes in land use on estuarine turbidity and long-term trends from historical satellite imagery could provide invaluable insights into managing our estuaries better.
