The destruction of the Gulf Coast estuary habitat by the on-going oil leak will have devastating effects on the functioning of ecosystem as a whole. Estuaries are semi enclosed bodies of water formed when fresh water from rivers and coastal streams flows into and mixes with salt water of the ocean (1). As many have pointed out these brackish wetlands provide critical habitat for spawning and larval development of many organisms in the Gulf in addition to providing habitat for birds and wildlife. Their role in the health of the Gulf is central, providing nutrients, habitat, and filtration of waters released from land.
In an estuary, nutrient-rich river waters combine with warmer, light infused shallow coastal waters and the upwelling of nutrient-rich deep ocean waters to generate primary productivity. The mixing of lighter fresh water and heavier salt water trap and circulate nutrients such that they are often retained and recycled by benthic (bottom dwelling) organisms to create a self-enriching system. In some estuaries, where productivity exceeds what can be used within the estuary, the action of regular tidal flushing moves nutrients and organic materials to adjacent coastal waters thereby increasing their productivity (1).What effect will the oil spill have on estuaries? There is, unfortunately, many cases where oil spills have impacted estuaries.Open seas have a much greater capacity to assimilate spilled oil and reduce its harmful effects. As many learned when the supertanker Exxon Valdez went aground in Alaska's Prince William Sound, however, nearshore spills can be disastrous, especially when they occur within partly enclosed bodies of water, such as a sound, bay, or estuary. Riverine and estuarine currents make spills and slicks particularly difficult to contain. They quickly carry the oil to shorelines, marshes, and flats where they do their worst damage. An oil slick is a threat to most creatures in its path, especially sea birds, waterfowl, and fur-bearing mammals. It can blanket and smother whole communities of shoreline and intertidal organisms, kill the eggs and larvae of fish and shellfish, and taint entire colonies of adult shellfish. In the confines of an estuary, even relatively small oil spills can wipe out whole populations of certain organisms, thus upsetting the food chain
there for years to come (2).
The movement of the oil through and into the estuary can occur at a surprising rate. Take the example of the oil spill near the Humber Estuary, Denmark. The movement of the oil was observed in the following manner:
"Neap tides and easterly winds on over the following four days kept the oil inside the estuary but the pollution had been driven up-stream beyond the Humber Bridge as far as the River Trent.
On the 28th September, there was oiling of the south bank between Skitter Ness to Grimsby. There was no oiled noted on the north bank, however oil was seen floating west of the Humber Bridge (15 miles from the spill’s origin).
On the 29th September, the oil had travelled west reaching Trent Falls by the afternoon.
By the 30th September large deposits of oil were found at Trent Falls and the Humber Wildfowl Refuge as well as from the Bridge to Grimsby.
By the 1st October, the wind had changed to south-southwest carrying the oil onto the north bank, affecting the Humber wildfowl refuge in particular. Oil was seen in the River Ouse and Trent and also reported at Saltend and Paull.
On the 2nd October, oil was reported on the north bank of the outer estuary around Sunk Island
The oil spread on the tides throughout approximately 50 miles of the estuary. In general the oiling of the middle and outer estuary had been most severe on the south bank, while in the upper estuary, the north bank had probably received the most oil. (3)"
It is clear, therefore, that the oil will be spread throughout the estuaries adjacent to the Gulf in short order. What can be done once this happens? Will we stand by with tied hands and let "natural attenuation" happen (this term is used in the environmental cleanup sector in cases where the responsible parties- polluters- are proposing to watch and see how nature deals with their mess. In some cases this is actually the best option available. There are environments and situations where the continued meddling of people only increases the environmental damage. Typically, these situations are in low-productivity environments and where the local microflora contains organisms capable of metabolizing the pollutant at an acceptable rate. Groundwater pollution plumes are often "managed" by monitored natural attenuation. However, Monitored Natural Attenuation- MNA is frequently proposed by polluters as to decrease the cost of their cleanup operations without regard for the effectiveness of the approach.) ?
It is very unlikely that, given the magnitude of the release of oil in the Gulf, active cleanup approaches will be feasible for every acre of impacted estuary. It is critical, therefore, that the chosen cleanup approaches are as effective as possible. Additionally, given our precarious global climate situation, we need to maintain awareness of the net impact of the remediation of the Gulf region. "Green" remediation approaches have emerged in recent years on the heals of the "sustainability" movement of recent years. While it is still evolving, the fundamental consideration of Green Remediation is to ensure that polluted site cleanup has a net positive impact on the quality and health of the site. Some of the considerations that green remediation adds to the discussion of remedial options are, among others:
- Total Energy Use and Renewable Energy Use
- Air Pollutants and Greenhouse Gas Emissions
- Water Use and Impacts to Water Resources
- Materials Management and Waste Reduction
- Land Management and Ecosystems Protection (4)
Whereas, traditional environmental cleanup processes only consider the cost ($) of the available technologies and their relative effectiveness. The lowest cost that achieves the end goal is chosen regardless of the potential myriad of secondary costs (fuel consumption, habitat loss, noise, land use restrictions, carbon releases) associated with the low cost($) option.
More on Green Remediation next time....
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