Coos Bay - WikiHQ

alt=A map of Coos Bay, with key locations labelled. This map is based on figure 1.20 from Rumrill, (2008). "The Ecology of the South Slough Estuary: Site Profile of the South Slough National Estuarine Research Reserve."|thumb|314x314px|A map of Coos Bay, with key locations labelled. This map is based on figure 1.20 from Rumrill, (2008). "The Ecology of the South Slough Estuary: Site Profile of the South Slough National Estuarine Research Reserve."Coos Bay (Coos language: Atsixiis or Hanisich) is an estuary where the Coos River enters the Pacific Ocean, the estuary is approximately 12 miles long and up to two miles wide. It is the largest estuary completely within Oregon state lines. The Coos Bay watershed covers an area of about 600 square miles and is located in northern Coos County, Oregon, in the United States. The Coos River, which begins in the Oregon Coast Range, enters the bay from the east. From Coos River, the bay forms a sharp loop northward before arching back to the south and out to the Pacific Ocean. Haynes Inlet enters the top of this loop. South Slough branches off from the bay directly before its entrance into the Pacific Ocean. The bay was formed when sea levels rose over 20,000 years ago at the end of the Last Glacial Maximum, flooding the mouth of the Coos River. North Bend, located at the apex of the peninsula, is home to the Southwest Oregon Regional Airport.

The estuary has been altered over 150 years of modern anthropogenic use. Dredging, deepening, river diversion and spoil disposal has led to physical, biological, and chemical changes to the system over time.

Geology

alt=Orange flowers in the foreground with blue water and across the water is sandy dunes and some evergreens.|thumb|299x299px|Coos Bay and its nearby sand dunes

The bedrock of the greater Coos Bay region was formed from the Mesozoic through the Pliocene eras out of volcanic rock, sedimentary rock, and igneous rock intrusions. The area's geologic history is highlighted by tectonic interaction between oceanic and continental plates. The center of Coos Bay, where the towns of North Bend and Coos Bay sit, was formed during the late Pliocene or early Pleistocene. These formed much more recently as sand was deposited along the coast after eroding from other areas. By studying the transition from peaty to muddy intertidal sediment and the associated microfossils in the estuary, researchers were able to determine 10 instances of sudden rises in sea level as a potential proxy for earthquakes, including two dating 1,700 and 2,300 years ago when sea level rose by at least half a meter. This same study also found evidence of a large earthquake 300 years ago along the great plate boundary. and is heavily influenced by the Pacific Ocean and precipitation from the Coast Range. Regional weather consists of a cool, wet season in the winter (November through March) with an average annual rainfall of 56 inches, and a mild, dry season in the summer (May through September) with an average rainfall of less than 4 inches. Air temperatures range from 40° to 75 °F. Winter storms lead to accumulation of winter precipitation and which is a significant input of fresh water and sediments. For an estuary, this involves the tributaries and their flow rates, bottom topography, water discharge and the drainage basin, and sedimentation and deposition.

Tributaries

Thirty tributaries enter the bay, including 13 freshwater sources, the Coos River being the largest freshwater source. This is greater than the sea level is expected to rise locally, 1.10 ± 0.73 mm/yr.

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|+Coos Bay Tributaries (1974) The shallow and narrow V-shaped topography of Coos Bay is more varied across the channel than it is longitudinally. It is deepest near the mouth of the estuary, where the bottom is uniform, and the slope leading to this decline is gentle. In the summer, wind primarily comes from the North along the Oregon coast, bringing up nutrient-rich deep water and boosting primary production. Strong tides then move these upwelled nutrients further upstream, which stimulates primary production in the estuary. Oregon experiences mixed semi-diurnal tides, meaning there are two high and two low tides per day which differ in height. During the dry season, the major input of nitrogen comes from the ocean following upwelling events bringing nutrients like nitrogen into the estuary. In the late summer and fall, nitrate concentrations measured at low tide are varied, with highest concentrations in the tidal regions of the estuary, and lowest at the riverine ends. Thus, phosphorus concentrations also vary depending on location in the estuary, on the ocean end or riverine end. Photosynthesis by primary producers draws down atmospheric carbon dioxide and eventual burial of primary producers such as eelgrass and algae lead to long term burial of carbon in estuarine sediments. Estuaries can provide an important sink for increasing global carbon dioxide concentrations as estuary sediments can store carbon rapidly depending on tidal fluxes.

Temperature, salinity, and dissolved oxygen levels vary according to wind forcing, river discharge and tides, with a variety of timescales from daily (tidal) to yearly. TBT became an environmental concern in the late 1980s after commercial oyster farmers began noticing shell deformities. After sample results showed toxic levels of TBT, the two shipyards worked with the DEQ to clean up contaminated sediments and implement more environmentally conscience practices, which allowed Coos Bay to avoid being listed as a superfund site. Eelgrass beds are a vital habitat to many species of invertebrates. Additionally, the eelgrass affects the flow of water through the area, stabilizes the sediment, exchanges nutrients between the water column and sediments, and is a source of food for consumers. The Z. marina also decreased in spatial cover under treatment conditions, by 70.7% in high elevations and 36.7% in lower intertidal regions of the study. However, transplanted Z. marina did recover better than plots left to recover on their own. Over the course of the study, which includes the transition from El Niño to La Niña, leading to warmer winters and cooler summers, eelgrass density, biomass, and flowering all increased.

Shellfish

Some of Oregon's most productive shellfishing is in Coos Bay. The lower bay is the area that extends from the airport to the ocean entrance, and is marine dominated (meaning there is little freshwater influence). Some popular, easily accessible clamming spots are along Cape Arago highway, where recreational clammers can dig for gaper and butter clams, in the extensive mud flats during low tide. The resilience of a tidal marsh depends on the vegetation types and their location in the tidal frame, exposure to stressors, surrounding land use, and if there is enough space for migration.

The low sand marsh is mainly sandy, but may have silt and mud. This marsh type gently slopes at the edges into the surrounding area. Commonly found plants include Pickleweed, Seaside arrowgrass, Desert saltgrass, Three-Square rush, Jaumea, Dwarf hairgrass, Sea plantain, Paintbrush orthocarpus, Glaux maritima, Carex lyngbyei, and Tufted hairgrass. The low silt marsh is generally silty and muddy and is lacking in channels for tidal drainage. Commonly found plants include Triglochin maritirh, Scirpus robustus, Carex, Jaumea, Spergularia, Juncus lescurii, and Cotula coronopifolia. The sedge marsh is composed of low and high marshes which are likely to have diffuse tidal drainage and channels up to four feet high, respectively. Commonly found plants include Carex lynghyei, Triglochin, Deschampsia caespitosa, and Hordeum nodosum. The immature high marsh is easily identified as it is flat and sits a few feet above the surrounding mudflats. The immature high marsh also has deep channels that drain it. Commonly found plants include Carex, Deschampsia, Hordeum, Juncus lesccurii, Potentilla pacifica, Distichlis, Artiplex natula, and Agrostis alba. The mature high marsh is typically higher than the immature high marsh and it contains underground drainage channels. Commonly found plants include Remex occidentalis, Grindelia stricta, Trifolium wormskjoldii, Vicia gigantea, and Lathyrus japonicus. The bulrush-sedge marsh is typically found on the banks of a river or slough, particularly one with freshwater. Commonly plants include Scirpus validus and Carex lyngbyei. The diked marsh has broad variability as this is not a "natural" type of marsh. Instead, it is formed when saltwater is cut off from entering the former marsh. Most marshes found in Coos Bay were likely high or immature high marshes, before they were diked and used for pasture land. Saltwater plants, over time, will be replaced by freshwater plants. One saltwater plant that may remain is Juncus lescurii. The replacement plants, however, include grasses, shrubs, buttercups, herbs, alders, and other trees. The surge plain is the result of overflowing streams that were dammed, therefore also has broad variability.

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|+Area of Coos Bay Marshes (1974) Since then, the estuary and surrounding watershed have been constantly monitored by the National Oceanic and Atmospheric Administration and the Oregon Department of State Lands. are invasive in Coos Bay. Through 2015, seagrass saw an increase in abundance, Additionally, boats and ships have accidentally introduced terrestrial plant species such as gorse, English ivy, reed canary grass, and Spartina spp. Qualman Oyster Farms is located near the entrance to South Slough. Additionally, clams are harvested recreationally. Pacific whiting, Chinook salmon, Albacore tuna, and Pacific halibut. The majority of cargo is offloaded in the southeast corner of Coos Bay, which is near the head of the inlet, opposite the Coos River entrance. Currently, 2 million tons of cargo move through the port.

Natural gas

Jordan Cove, located across the inlet from the airport, was the proposed site of a liquefied natural gas (LNG) terminal by Jordan Cove Energy Project. The terminal would have exported liquefied natural gas from an underground pipeline that would have met with existing pipelines near Malin. The terminal and pipeline projects were cancelled in 2021. Oregon Governor Kulongoski expressed various environmental concerns.

External links

Coos Watershed Association
Robbins, William. "Coos Bay". The Oregon Encyclopedia.
Oregon Department of State Lands: About South Slough Reserve
National Oceanic and Atmospheric Administration National Estuarine Research Reserves: South Slough National Estuarine Research Reserve
National Estuarine Research Reserve Association: South Slough Reserve, Oregon

References