Netarts Bay is an estuarine bay on the northern Oregon Coast of the U.S. state of Oregon, located about 5 miles (8.0 km) southwest of Tillamook. The unincorporated community of Netarts is located on the north end of the bay and Netarts Bay Shellfish Preserve, managed by Oregon Department of Fish and Wildlife, is located on the south side of the bay. The sand spit on the west side of Netarts bay is part of Cape Lookout State Park.
The bay is approximately 5 by 1.5 miles (8.0 by 2.4 km) and totals 2,325 acres (9.41 km2) in area, making it Oregon's seventh largest bay.Advisory Committee to the State Land Board (July 1972). "An Inventory of Filled Lands in Netarts Bay Estuary" (pdf). Oregon State University Scholars Archive. p. 2. Retrieved 2008-07-25. Of that, 812 acres (3.29 km2) are permanently submerged—the balance of 1,513 acres (6.12 km2) is intertidal land. It experiences a maximum tidal range of 9 feet (3 m).
The bay is part of a watershed of 13 square miles (34 km2) that is fed by at least 16 small creeks. From north to south, there is Fall Creek, Hodgdon Creek, O'Hara Creek, Rice Creek, two unnamed creeks, Yager Creek, three unnamed creeks, Whiskey Creek, an unnamed creek, Austin Creek, two unnamed creeks, and Jackson Creek.
Physical characteristics
Tidal dynamics
Like other estuaries along the Oregon Coast, Netarts Bay experiences semi-diurnal tides (two high tides and two low tides per day). At mean low water (the lower low tide), the bay contains approximately 113 million cubic feet of water. Contrasting that with that a mean higher high tide volume of approximately 450 million cubic feet, the bay's tidal prism is about 33 million cubic feet. The tidal range varies between 1.5 and 3 meters(5 – 9 feet), which can vary the amount of water (40–90%) flushed out of the estuary during each tidal cycle. With a mean tidal period of 745 minutes,Glanzman, C., Glenne, Bard, Burgess, Fred, & Oregon State University. Engineering Experiment Station. (1971). Tidal hydraulics, flushing characteristics and water quality in Netarts Bay, Oregon : Final report. Corvallis, Or.: Engineering Experiment Station, Oregon State University. bay waters turn over, on average, twice a day. Mixing within the estuary is dependent on local winds and tides. Horizontal mixing is limited, although vertical mixing is strong. Little to no vertical variations in temperature and salinity prevent density-driven current velocities, indicating that Netarts Bay is a well-mixed estuary. This has been further corroborated by water quality and dye studies.
Sediment input and erosion
Annually, around 2500 tons of sediment are deposited into the bay. An observed 10% decrease in mean high water volume between 1957 and 1969 in conjunction with high sedimentation rates suggests that the bay is gradually filling with sediment over time.Dicken, S., Hanneson, Bill, & Johannessen, Carl L. (1961). Some recent physical changes of the Oregon coast. Eugene: Dept. of Geography, University of Oregon. LIDAR data has shown the strong erosional response of the Netarts Littoral Cell (a 14-km long stretch of beach tucked between the neighboring Cape Meares and Cape Lookout Headlands)Revell, D., Komar, P., & Sallenger, A. (2001). Application of LIDAR to erosion hotspots in the netarts littoral cell, Oregon. Illumina Conference Papers Index - Unstructured, Illumina Conference Papers Index - unstructured. to ENSO (El Niño Southern Oscillation) forcing. During strong El Niño events (e.g. 1997–98), as much as 70,000 cubic meters of sand can be transported. Waves propagating from the southwest erode the southern portion of the spit and transport sediment northward, resulting in northward movement of the bay inlet. This erosion-deposition pattern is amplified by rip currents that create erosional "hot spots" along the spit. Cape Lookout State Park, situated within one of these hotspots, is subject to this intense erosional forcing.
Geology
Within the last 5 million years, differential erosion patterns on the neighboring Cape Meares and Cape Lookout headlands formed the embayment in which Netarts Bay now sits. Sediment cores obtained from within the bay have provided geological evidence for the existence of large, regularly occurring megathrust earthquakes throughout northwestern Oregon and the larger Cascadia Subduction Zone. Carbon-14 dating of the sediments suggest recurrence rates for these earthquakes to be between 400 and 600 years, and that at least 4 major quakes occurred within the last 3000 years. Sharp sand-layer contacts in the sediment record (deposited by earthquake-generated tsunami waves) indicate post-quake sinking of the marsh. This phenomenon, known as coseismic subsidence, provides strong geological evidence for the regular occurrence of major earthquakes occurring within the Cascadia Subduction Zone. Remnants of fire hearths from Native American settlements along nearby Nehalem and Salmon Rivers provide additional evidence of land subsidence (1–2 meters) resultant from subduction-zone earthquakes.
Biology
Shellfish
Olympia oysters are the only native oyster to the West Coast of North America. The establishment of a commercial fishery in the 1860s confirms a historical population within Netarts bay, with evidence of harvesting along the West Coast of North America by humans going back 4000 years. Due to over harvesting, increased consumption, and the export of adult oysters to San Francisco Bay, oyster populations declined in the late 1800s and the commercial fishery collapsed. The last known naturally occurring population of Olympia oysters in Netarts was surveyed in 1954. Subsequent field surveys in 1979 and 1992 did not find any Olympia oysters within the bay. Potential factors preventing population recovery post fishery collapse include: habitat degradation, sedimentation by increased motorized boat use, suffocation by burrowing shrimp, pollution, predation by invasive Japanese oyster drill and parasitism by non-native flat worm After their 1992 survey, Oregon Department of Fish and Wildlife began a large scale restoration attempt in Netarts, setting out 9 million spat between 1993-1998. Olympia oyster populations did not return to historical levels, but surveys in 2004 detected low populations of transplanted oysters in the bay. Anecdotal observations from residents also suggest small pockets of naturally occurring oysters subsist in the southwest corner of the bay. Juvenile oysters planted on adult oyster shell as substrate demonstrated that Olympia oysters can grow and reproduce in the bay. Small scale, investigative restoration projects run by The Nature Conservancy were undertaken in 2005 and 2006 to rebuild populations of Olympia oysters in Netarts Bay by adding shell cultch with set Olympia oysters to the bay in hopes of increasing settlement substrate and broodstock. Early monitoring of these sites found reproductive tissue and brooded larvae in adults and recruitment of larvae on shell substrate, but monitoring of the site ceased in 2007. Restoration interests are driven by culinary interest in Olympia oysters, the potential economic benefits of a commercial fishery, and the significant ecosystem services that Olympia oysters provide, including filtering the water and providing substrate for other organisms.
Four species of bay clam are also found in Netarts Bay.
Marine flora
The main primary producers of the bay are eelgrass (Zostera marina, a type of seagrass), microscopic diatoms, and sea lettuce (Ulva enteromorpha, a type of macroalgae). Most of these species are found on mudflats, which account for about two-thirds of the total area of Netarts Bay.McIntire, C.D., Davis, M.W., Kentula, M.E., Whiting, M. (1983). Benthic Autotrophy in Netarts Bay, Oregon. Report prepared for Environmental Protection Agency, Corvallis, OR, USA.
Eelgrass beds are found in the intertidal and subtidal mudflats, and biologically interact with oyster beds in a few ways: The pseudofeces and feces of bivalves have been found to fertilize seagrass by increasing bioavailable macronutrients such as ammonium and phosphate in sediments. Bivalves also filter phytoplankton from the water column, a process which reduces water turbidity, allows more light to penetrate through the water column, and reduces the number of epiphytes living on seagrass leaves. Eelgrass is important as food for waterfowl, habitat for juvenile fish, and as physical shapers of the bay.Stout, H. (1976). The natural resources and human utilization of Netarts Bay, Oregon. Corvallis: Oregon State University. The growing season is from April to October.
Diatoms are found in benthic and pelagic environments of the bay, and also as epiphytes living on other marine plants. There is a total of 336 diatom taxa identified in the bay, 50 of which are planktonic, 123 of which are epiphytic, and 282 of which are benthic (about 111 taxa overlap the epiphytic and benthic categories). Benthic diatom assemblage distributions correspond to sediment type, grain size, and wave energy.
Sea lettuce, a macroalgae otherwise known as green nori, grows usually only in the summer. Seasonal upwelling along the Pacific North American coast has been correlated to increased sea lettuce productivity and decreased eelgrass productivity.
Japanese eelgrass (Zostera japonica) is an introduced species found in bays and estuaries ranging from Oregon to British Columbia, Canada. It was likely brought over by Pacific oyster seed shipments that began in the early 20th century used by commercial shellfisheries along the Pacific northwest coast.
Native Americans and Netarts Bay Netarts Bay and sand spit are within the historic territory of the Tillamook Indians, which ranged from Tillamook head in the north to the Nestucca River in the south and from the Pacific Ocean in the west to the Coast Range summit in the east.Bonacker, G., Martin, Robert C., Frenkel, Robert E., & Oregon. Natural Area Preserves Advisory Committee. (1979). Preserve analysis : Netarts Sand Spit. Salem, Or.: Oregon Natural Area Preserves Advisory Committee. Cape Lookout State Park contains 13 suspected archaeological sites, including 6 on Netarts sand spit representing at least one and perhaps up to three major villages. Archaeological excavations of Netarts Sandspit Village (35-TI-1) show evidence of a major Tillamook village that was occupied at least three separate times between 1300–1700 A.D.Newman, T. (1959). Tillamook prehistory and its relation to the Northwest coast culture area. University of Oregon. Excavations revealed semisubterranean cedar plank structures with single pitched roofs, numerous hearths and fire pits, and middens around all house pits. The village contained at least 13 house pits and may have contained up to 30–40 house pits. It has been described as "the most impressive house pit site on State Park lands along the Oregon Coast."
Numerous artifacts were found during excavation of 35-Ti-1 in the 1950s. Some of the bone and antler objects found include: wedges, adzes, awls, needles, bi-pointed pins, blades, harpoon barbs, chisels, digging stick handles, and bone carvings with faces, perhaps from clubs or wand handles. One house pit included whalebone objects including a 1.5m x 0.3m (~5 ft x 1 ft) seat and a possible whale vertebrae seat surrounded by fire pits. Numerous stone artifacts were also found at the site, including: projectile points, blades, scrapers, gravers, core choppers, modified flakes, double pitted cobbles, hammerstones, and whetstones. The most recent occupation layer also contained trade goods including: rusted iron (perhaps knife blades), a copper pendant, and many sherds of Chinese porcelain.