When hundreds of acres of the productive intertidal areas of Willapa Bay were diked it fit with what the people of the area needed at that time. It often did not take into account the very important role that these high intertidal areas played in relationship to the entire productivity of the bay.
These rich muddy benthic (bottom) areas store within the sediments vital minerals and nutrients, provide important links of the food chain such as benthic diatoms, provide habitat for burrowing invertebrates, act as feeding areas for various size animals and overall contribute to the entire biota of the bay. When these diked areas were cut off from the important influx of saline water to mix with the fresh water, it stopped them from storing the upland sediments along with organics, minerals and nutrients (such as silicates from the weathering of igneous rocks).
Without being captured by the intertidal flats, these valuable components to the basis of the food chain would be flushed to the ocean. There would not be the valuable role played by the bay as an important nursery area. That is the productive feature of a shallow bay and intertidal flats such as we have in Willapa. These areas we refer to as mudflats provide the storage areas and the first chance for many animals and plants to utilize, and thus start a recycling, of critical materials as they mix from the fresh and saline waters.
Willapa Bay lost a sizable percentage of these productive areas when dikes were constructed. There are many specific examples within the food web of how this works but a generalized sequence might serve to illustrate. The brackish (mix of fresh and sea water) medium over the mudflats provide the media and nutrient mixture for plant production, such as bottom algae (especially diatoms), which flourish on the nutrients within the sediments.
The various seasons play a role also. The dynamics of the sedimentary areas as they are being being deposited and eroded contain upland minerals and nutrients transported by the fresh water runoff along with wind and currents often during the winter during higher rainfall times. These normally single-celled plants in turn are utilized by many types of zooplankton, some of which live in or on the mudflat. Others may swim or travel onto the area as the tide ebbs and flows across the flat and still others await their preferred fare and filter it from the water which washes off the mudflat.
Think of oysters and clams. The activity of these small animals within the mudflat also helps liberate nutrients to the tidal currents. In turn, the inhabitants of the mudflat are prey for some larger predators such as crab and fish (including salmon juveniles, to cite a familiar example) and especially our thousands of shorebirds. The intertidal brackish area (mudflat) is a rich biological happening due to its unique position with respect to elevation and the mix of saline and fresh water from the upland and the bay. This was lost when a dike was put in or, as thought of at the time, was exchanged for a different type of biological production. We supposedly now better understand the value of these highly productive benthic areas and their importance to the entire bay. Science has pointed out the intricate and expansively vital role the mudflats play in the health of the bay. It is also obvious but somewhat understandable that most do not understand this importance.
Many productive estuaries have found out the hard way losing a great percent of the productive capacity when the mudflats have been eliminated by such activities as dikes, filling or both.
In addition, the role the mudflats play requires one to think not of what might seem important on the exact acreage separated from the bay behind the dike, but what that area did and could again contribute to the fauna and flora and indeed the total productivity of the entire estuary.
So, as folks give their views on this matter, it is hoped that the positive impacts of removing the dike are made a fair part of the consideration. Granted, they are not as easily observed, but they will prove to be far more numerous and important than keeping part of the bay cut off. I would say there is just as much if not much more interest in watching shorebirds, falcons, ducks and other waterfowl working a brackish water mudflat than having access to a few freshwater protected hunting blinds.
Richard L. Wilson, Ph.D.
President, Bay Center Mariculture Co.