Though often unappreciated an estuary is an extremely dynamic and fascinating place. When understood, the secrets of an estuary can be transformed into wonder and amazement, offering different experiences with each visit. Combinations of sight, sound, smell and touch are forever changing and interacting with one another, providing visitors with memorable encounters.
But an estuary is also a fragile environement dependent upon the health of the interacting systmens of which it is comprised. The relative abundance and quality of river and ocean water, wetlands, mudflats, eelgrass beds, deepwater channels and adjunct uplands ultimately determine estuarine health. Disturbances or alterations in any one of these components directly affects the qualits and functional capacity of adjacent parts and thus the entire estuary.
Yaquina Bay has an extreme tidal influence that extends from the bay entrance at the jetties to Toledo about 10 miles upriver defining the limits of the estuary. Tides fluctuate daily in response to tidal cycles of about six hours. Each day there are paired high and low tides of unequal duration and height called semi-diurnal tides. Tides are determined by the earth's rotation and gravitational forces between the earth and the sun and moon.
Saltwater intrusion is also limited by seasonal water flows of the Yaquina River. Winter rains increase water flow within the Yaquina River and tributaries which dilutes the sea water and limits tidal intrusion. During the normally dry summers, when river flow is dramatically reduced salt- water penetrates further up the Yaquina River.
Interactions of ocean water and freshwater have some important properties for the estuary. Tidally driven ocean water being denser and heavier than freshwater, and tends to sink as it moves upriver, while the lighter freshwater travels downstream riding on top of the saltwater. This phenomenon is known as a saltwedge and occurs in some large estuaries. Tidal wedges are not well developed in Oregon's small estuaries because strong tidal currents rapidly mix the ocean and river waters. The resulting mixture of fresh and salt water has important implications for animals living there.
Salt content in water is critical to the distribution of plants and animals in the estuary. Salinity tolerances restrict fresh water organisms to the upper reaches of the estuary while marine species are limited to the lower areas of the estuary. In between are specially adapted plants and animals able to tolerate constantly changing salinities, temperatures, and exposure to air. Some organisms increase their habitat range by following salinity gradients with each flood and ebb tide.
Open water channels are very important to salmon using them as migration corridors and to various fish feeding in the estuary. Harbor seals, California sea lions and diving birds also use the open channels to feed on fish.
Yaquina Bay Estuary Tidelands
Of the 4200 acres that comprise the Yaquina Bay Estuary, over 2500 acres are classified as tidelands. Tidelands are areas that may be exposed to air during low tides, and extend from the open water channels to the salt marshes fringing the edges of the estuary. They encompass a variety of habitats. Tidelands usually develop in areas sheltered from direct wave action or strong water currents. Sediments "rain" out of the water column and settle on the bottom as currents are slowed over the expansive flat regions. Over time sediments accumulate and create vast muddy areas known as mudflats.
Eelgrass Beds
Transition zones between mudflats and open water channels may be filled with eelgrass beds. These beds comprise some of the most critical habitat areas in estuaries. Dense growths of eelgrass can reduce local water currents and effectively trap silt and dissolved organic matter. The beds are highly productive areas of the estuary and are a significant source of detritus--dead organic material in the process of decomposition.
Many species of fish depend upon eelgrass beds for spawning, feeding and refuge. Pacific herring spawn in the eelgrass beds each February in Yaquina Bay, while chinook and coho salmon spend critical portions of their juvenile lives there. Dungeness crab, clams, mud shrimp and a variety of invertebrates are also associated with eelgrass beds. Some waterfowl, especially the Brant's goose, are known to extensively feed upon eelgrass beds during their migration stopovers.
Mudflats
Tidal flats, or mudflats, are the most conspicuous part of an estuary. These are vast flat areas covered with sand or mud that are dissected by a network of tidal channels. On flood tides seawater enters the tidal channels and eventually spills over onto the adjacent flats. This process deposits sediments on the mudflats and bathes benthic (bottom dwelling) organisms with nutrient rich water. On the ebb tide, water drains out into the tidachannels leaving the mudflats exposed to the air. Although mudflats may appear worthless and smelly places, they are in fact very productive areas. One close
look at a mudflat during low tide may reveal thousands of holes covering the surface of the mudflat. These holes are created by various types of animals burrowing into the mud,
not by water draining into the substrate as many believe.
A shovelful of mud would be teeming with worms, clams, mud shrimp and various isopods. These animals are either suspension feeders (filter water), deposit feeders (eat substrate) or individual select prey. Diatoms (type of phyto-plankton) and mats of filamentous algae may also be abundant. These algae are vital components of mudflats, because they have extremely high rates of photosynthesis, producing food that nourishes benthic animals like snails and crab.
Birds are also abundant on mudflats during low tide. Gulls, terns, waterfowl, herons and shorebirds rely heavily on the bounty of the mudflats and the small tide pools for their survival. At high tide, fish and crabs also prey upon the abundant invertebrates feeding upon the detritus.
Tidal Marshes
Tidal marshes in Yaquina Bay are normally fringing marshes between uplands and mudflats. They are formed in upper regions of the mudflat where sediment accumulation is rapid. As the mud increases in thickness, the degree and duration of submergence during high tide is reduced, allowing colonization of plants. First to appear is pickleweed, which is able to tolerate frequent inundation of salt water. This helps diminish erosion and trap more sediments, further building up the level of the marsh and allowing other wetland plants to populate the marsh.
Mature tidal marshes are subject to daily tides in the lower marsh areas and occasional tides in the upper marsh. Soils that are inundated by water for periods of time become saturated with salt water and are anoxic (without oxygen) below a few centimeters. Salt marsh plants are adapted to tolerate these soils and distribute themselves according to their ability to tolerate salty, anoxic soils and submersion.
Jaumea and pickleweed have adapted to the salt marsh by developing special cells that hold excess water. This allows them to dilute the salt concentration in their tissues. Salt grass and salt brush employ a different means to tolerate salt. They have special cells that accumulate salt and excrete it through pores on the underside of their leaves.
Tidal marshes are some of the most productive places on earth in terms of amount of organic matter created. (Through the process of photosynthesis huge amounts
of carbon dioxide and water are converted into simple sugars by the marsh plants.) When these plants die and decay, the organic matter becomes food for other organisms. Many fish and wildlife species live in association with tidal marshes because of the rich food supply and the protection dense growths of salt marsh plants provide.
Detritus and Energy Flow
Herbivores (plant-eating animals) consume less than 10% of plant material in the estuary. The remaining 90% becomes available to other organisms through the detrital food chain. This remarkable nutrient recycling system is comprised of dead organic material that is in the process of being decomposed by bacteria and other microscopic decomposers. The most biologically active region in an estuary occurs within the
first few centimeters of sediments where detrital communities flourish.
Organic material comes from vegetation or animals living within the estuary or is washed in from organic sources surrounding the watershed. As detritus is broken down by the decomposers, other organisms such as snails, crabs, worms and copepods eat the detrital particles covered abundantly with bacteria and microalgae. Detritus is actually richer in protein than plant material because it has so many other organisms associated with it. In this way, plant production can be effectively transferred up through the food web providing nourishment for an entire community of bottom dwelling (benthic) organisms. In turn, larger fish and birds prey extensively upon these benthic dwelling organsims for food.
Detrital communities are well established in salt marshes and eelgrass beds where dead organic matter often accumulates. As plant tissues are broken down to small particles, tidal currents sweep these particles to other parts of the estuary and into nearshore waters fueling waterborne life such as plankton and bottom dwelling organisms.
Wildlife Abundance and Diversity
Estuaries have fewer residental species of plants and animals compared to neighboring marine or freshwater habitats.
Relatively few organisms have adapted to meet the harsh physical demands of estuarine life. But those organisms that reside in estuaries are notably abundant. Plants, crabs, clams, bacteria, and polychaete and nematode worms can be found in extremely dense numbers. This is clearly an attribute of the high production of the estuary and demonstrates how well these organisms have adapted to thrive in constantly changing estuarine conditions. Predators such as fish, birds, marine mammals and humans are each uniquely equipped to exploit this great abundance of prey.
The diversity of life within the Yaquina Bay Estuary results in part from the many different habitats it contains. Freshwater wetlands, salt marshes, mudflats, eelgrass beds, open water channels and intertidal areas make Yaquina Bay an outstandingly dynamic and diverse place capable of supporting a cornucopia of life.
Each organism you encounter in the estuary relies on one or more of the benefits these environments provide: abundant food supply (for both plants and animals), shelter from the open ocean and shelter from predators in the salt marsh and eelgrass beds. In fact estuaries are nursery areas for the young of many fish due to the abundant food and shelter.
Large-scale harvesting of Yaquina Bay's resources did not occur until the 1860s when a San Francisco firm started commercially harvesting native oysters. Soon afterwards, Yaquina Bay became a prominent source of oysters for the entire West Coast, and many processing plants and canneries sprung up along its shores. Not long after the oyster boom of the 1880s, salmon became an important fishery, which attracted more people to settle in the area and harvest the seemingly endless resources of Yaquina Bay.
Aside from the bounty of Yaquina Bay's natural resources, settlers found its natural harboring capacity to be crucial to the community. Cargo ships were able to escape the relentless Pacific storms by slipping into Yaquina Bay, while local fishing fleets could safely dock in the bay and unload their hauls to bayfront processing plants.
Yaquina Bay's close proximity to vast forests of the coastal range further stimulated its development as a shipping port. Logging towns were quick to spring up along the surrounding shores and hillsides. Moored logs and large cargo ships became a common sight in the Yaquina Bay, since shipping proved to be the only efficient means of transporting the lumber to larger markets.
Commercial Fishing
Nearly all of the activities that historically attracted people to settle near the Yaquina Bay area continue to make up the foundation of the economy in this region. Newport is home to Oregon's second largest commercial fishing fleet (nearly 250
vessels), which supports a flourishing seafood processing and packaging industry.
The fishing industry is especially tied to the health of the bay. Three-quarters of the U.S. West Coast commercial fish harvest is composed of species that utilize estuaries at some point in their life. English sole, herring, salmon and Dungeness crab are some of the estuarine dependent species currently landed in Newport. Commercial oysters continue to be cultured in the estuary between Newport and Toledo and provide seafood markets worldwide with fresh oysters.
Recreation
In the last fifteen years, Newport has seen an explosion of tourist related industries develop in the region. Tourists from all over the world visit the Yaquina Bay area each year to experience the mystical charm of the coast and adjacent estuary. Recreational fishermen, sailors, clammers, crabbers, hikers and wildlife observers
continue to increase each year bringing new service related jobs and income to the community. Yaquina Bay has five recreational boat storage facilities that are home to over 650 recreational boats of all types. Estuaries also give humans living nearby a quiet tranquil place to retreat to and enjoy the splendors of nature, a value far exceeding traditional economic considerations.
Reduce Pollution and Flooding
Aside from attracting people to visit or work in the region, Yaquina Bay performs several tasks "free of charge" to the community. Plants and benthic organisms living in salt marshes and wetlands ingest pollutants and biochemically render some of them less harmful. Salt marshes and wetlands also act as flood control barriers, slowing the ebb and flow of tides near shore and preventing winter floods from washing over the banks. In a sense, estuaries are the "kidneys" of the landscape, filtering out wastes while retaining valuable nutrients that may be used by plants for growth.
What is done to the landscape tends to show up in the estuary as well. Unsound forestry and agriculture practices can choke the estuary with sediments and pollutants, and reduce its overall capacity for photosynthetic production. Pesticides and fertilizers combined with oil, gas and other pollution from ships, boats, homes and industries also wash in and can accumulate to levels that deteriorate estuarine quality and functions.
Another disturbance affecting the health of Yaquina Bay Estuary is dredging. Frequent dredging has sculpted Yaquina Bay into one of Oregon's three deep draft ports. Yaquina Bay is dredged from the jetty entrance all the way to Toledo, 10 miles upriver. Natural water circulation of the bay is effected by dredging. Deep channels increase the influence of tidal action, and decrease freshwater flushing.
Dredging also disturbs benthic deep channel communities and resuspends fine sediments into the water. Suspended sediments reduce water clarity and mobolize toxic compounds. Plants and animals living in these areas can accumulate these toxins and pass them on to predators like large fish and humans.
Human competition for estuarine use is great. Estuarine functions and quality become degraded as people inflict more pressure on them. The resiliency of an estuary is limited, and many areas suffer from abuse and overuse.
Because of the importance of estuaries and the pressures exerted upon them, many activities are regulated. In Oregon, local governments adopted land use plans that specify allowable uses for different portions of the estuary and adjacent lands. Additionally, activities that involve the filling or degrading of the estuary are regulated by the Oregon Division of State Lands and the Army Corps of Engineers. A permit is required for these activities. The state of Oregon owns the lands below mean low water and some intertidal areas; these lands are managed for the people of Oregon by the Division of State Lands.
People must learn to live harmoniously with the estuary to ensure its health. Yaquina Bay is the lifeblood of the community. It's values must be fully understood and considered if human activities are not to endanger its existence.
Original composed by Vicki Osis and Brady Phillips for OSU Extension Sea Grant.
Revised edition for HMSC website by Amy Martin, 1997.
McLusky, D.S. The Estuarine Ecosystem. John Wiley and Sons. New York. 1981.
Mitsch, W.J. and J.G. Gosselink. Wetlands. Van Nostrand Reinhold. New York. 1986.
Teal, J. and M.. Life and Death of the Salt Marsh. Ballantine Books. New York. 1969.
Cortright, R., J. Weber and R. Bailey. The Oregon Estuary Plan Book. Oregon Department of Land Conservation and Development. Salem. 1987.