Coos Bay
Template:Short description Template:About
Coos Bay (Coos language: Atsixiis or Hanisich)<ref name=Hanis>{{#invoke:citation/CS1|citation
|CitationClass=web }}</ref> is an estuary where the Coos River enters the Pacific Ocean, the estuary is approximately 12 miles long<ref name="Percy-1974">Template:Cite book</ref> and up to two miles wide. It is the largest estuary completely within Oregon state lines.<ref name="Schrager">Template:Cite journal</ref><ref name="Rumrill-2008">Template:Cite journal</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Schrager" /> Coos Bay is Oregon's most important coastal industrial center and international shipping port, with close ties to San Francisco, the Columbia River, Puget Sound and other major ports of the Pacific rim.<ref name="Rumrill-2008" />
The city of Coos Bay is located on the peninsula formed by the inside of the loop of the bay. Charleston is located near the entrance to South Slough. Many of the commercial fishing and recreational fishing boats that call Coos Bay home are docked in Charleston.<ref name="Port of Coos Bay - Oregon's Seaport-3">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Eidam-2020-2">Template:Cite journal</ref><ref name="Eidam-2020">Template:Cite journal</ref> Dredging, deepening, river diversion and spoil disposal has led to physical, biological, and chemical changes to the system over time.
GeologyEdit
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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.<ref name="Baldwin-1973">Template:Cite journal</ref> The area's geologic history is highlighted by tectonic interaction between oceanic and continental plates.<ref name="Baldwin-1973" /> Subduction and abduction of the oceanic plate with the North American Plate has led to a thicker crust in Southwestern Oregon.<ref name="Baldwin-1973" /> The Empire Formation, on which Coos Bay lies, is mainly composed of sedimentary rock created by marine sediments that were deposited offshore before being pushed onshore over millions of years.<ref name="Baldwin-1973" /> This process results in the oldest rock being furthest east. East of the bay, and in the Coos River watershed, the bedrock is the oldest, formed during the Eocene.<ref name="digital.osl.state.or.us">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The center of Coos Bay, where the towns of North Bend and Coos Bay sit, was formed during the late Pliocene or early Pleistocene.<ref name="Baldwin-1973" /> The North Spit, the most western area bordering the ocean, is composed of sand dunes.<ref>Report Template:Webarchive</ref> These formed much more recently as sand was deposited along the coast after eroding from other areas.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Nelson-1996">Template:Cite journal</ref> This same study also found evidence of a large earthquake 300 years ago along the great plate boundary.<ref name="Nelson-1996" /> In addition, sea level rise 20,000 years ago drowned the prior river mouth, creating Coos Bay estuary as we know today.<ref name="Schrager" /><ref name="Rumrill-2008" />
Physical geographyEdit
Tidal flatsEdit
Tidal flats are areas where sediments that are deposited from rivers and tides accumulate. Coos Bay is primarily made up of mud and sand flats that form in areas of low tidal activity.<ref name="Schrager" /> The estuary covers 10,973 acres at mean high water and 5,810 acres at mean low water, and about 48% of the watershed is tideland.<ref name="Percy-1974" /> Tidal effects can extend up the tributaries 27 miles from the ocean.<ref name="Percy-1974" /> Of the tidal flats in Coos Bay estuary, organic content is highest in the mudflats (8-18% of dry weight, 19.77 ppt) compared to the sandflats (1-2% of dry weight, <0.1 ppt).<ref name="Rumrill-2008" /> These areas tend to lack visible vegetation, but do support benthic diatoms, mats of green and yellow green algae, and eelgrass beds (Zostera marina and Z. japonica). Tidal flats in the estuary have a network of shallow channels that allow water to drain when the flats are above water, and when submerged, allow water and sediment to pass through the flats.<ref name="Rumrill-2008" /> In this way, the flats act as a barrier that slows the water passing through, reduces how much water can flow through, and encourages the deposition, re-suspension, and transport of particles with the tides as the flats are constantly experiencing deposition and erosion.<ref name="Rumrill-2008" />
The mudflats are primarily made of a mix of medium and fine-grained sands, silts, and clays, while the sandflats are primarily made of medium-sized sand grains derived from the erosion of the nearby cliffs.<ref name="Rumrill-2008" /> The higher organic content of mudflats is composed of plant and animal tissues and wastes, diatoms, bacteria, and flocculants, chemicals that pull suspended particles out of the water to form into sediment.<ref name="Rumrill-2008" /> The environment a few centimeters below the sediment doesn't have enough oxygen, so sulfate-reducing bacteria live there, breaking down organic matter and producing hydrogen sulfide, giving the mudflats the classic "rotten egg" smell.<ref name="Rumrill-2008" />
WeatherEdit
The mild marine climate of Coos Bay is classified as Csb or a Temperate Mediterranean Climate zone<ref>Template:Cite journal</ref> and is heavily influenced by the Pacific Ocean and precipitation from the Coast Range.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Schrager" /> Runoff follows this same pattern, with approximately one month of lag.<ref name="Roye-1979">Template:Cite book</ref> 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.<ref name="Schrager" />
Fluvial geomorphologyEdit
Fluvial geomorphology is the study of the way rivers move through and affect their surrounding landscape.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> For an estuary, this involves the tributaries and their flow rates, bottom topography, water discharge and the drainage basin, and sedimentation and deposition.
TributariesEdit
Thirty tributaries enter the bay, including 13 freshwater sources, the Coos River being the largest freshwater source.<ref name="Eidam-2020" /><ref name="Roye-1979" /> About 1 m3/s of freshwater is released by the Coos River into the estuary in the summer and >300 m3/s in the winter.<ref name="Eidam-2020" /> These waters travel through areas of heavy logging and limited agriculture, originating from the Coastal Range.<ref name="Eidam-2020" /> The main channel of the estuary follows the north–south trending anticline (an arch-like fold in the ground), ending in the Isthmus Slough, Catching Slough, Haynes Inlet, and Coos River; while southward, the South Slough follows the syncline (an inward curve in the ground).<ref name="Eidam-2020" /> The sediment accumulation rate is approximately 2.3–9 mm/yr in a 0.9-m deep flat in South Slough over a 300-year timescale.<ref name="Eidam-2020" /><ref name="Johnson-2019">Template:Cite journal</ref> This is greater than the sea level is expected to rise locally, 1.10 ± 0.73 mm/yr.<ref name="Eidam-2020" /><ref>Template:Cite journal</ref>
| Stream | Length (miles) | Drainage Area (square miles) | Max Freshwater Annual Yield (ac-ft) | Min Freshwater Annual Yield (ac-ft) | Mean Freshwater Annual Yield (ac-ft) |
|---|---|---|---|---|---|
| Coos River | 5.5 | 415 | 2,200,000 | 1,130,000 | 1,590,000 |
| South Fork Coos River | 31.3 | 254 | 1,280,000 | 660,000 | 930,000 |
| Millicoma River | 8.7 | 151 | 880,000 | 450,000 | 630,000 |
| East Fork Millicoma River | 23.9 | 79 | 460,000 | 230,000 | 330,000 |
| West Fork Millicoma River | 34.9 | 55 | - | - | - |
Bottom topographyEdit
Coos Bay is considered a drowned river valley estuary, meaning it was a river valley that was flooded as sea levels rose.<ref name="Roye-1979" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The shallow and narrow V-shaped topography of Coos Bay is more varied across the channel than it is longitudinally.<ref name="Roye-1979" /><ref name="Baker-1978">Template:Cite journal</ref> It is deepest near the mouth of the estuary, where the bottom is uniform, and the slope leading to this decline is gentle.<ref name="Roye-1979" /> This topography, coupled with high tidal range and low runoff, allows for lateral and vertical mixing.<ref name="Baker-1978" />
Water discharge and drainage basinEdit
Annually, Coos Bay is estimated to discharge 2.2 million acre-feet of fresh water, with a yearly maximum of 3,044,000 ac-ft and a minimum of 1,560,000 ac-ft, based on extrapolations of fresh water inflow measured at the West Fork of the Millicoma River mouth in 1974.<ref name="Roye-1979" /> According to a US Department of Commerce survey from 1954 to 1970, freshwater inflow enters the estuary at a rate of 90 cubic feet per second (cfs) in the summer and 5500 cfs in the winter with an average of 2200 cfs.<ref name="Percy-1974" /> The drainage basin consists of forest, cropland, and rangelands.<ref name="Percy-1974" /> The South Slough watershed alone has a drainage area of about 7,932 ha.<ref name="Rumrill-2008" />
| Stream (at mouth) | Drainage area (square miles) | High average monthly flow (cfs) | Low average monthly flow (cfs) | Mean average monthly flow (cfs) |
|---|---|---|---|---|
| Coos River | 415 | 5,500 (Feb) | 90 (Aug, Sept) | 2,200 |
| South Fork Coos River | 254 | 3,300 (Feb) | 50 (Aug, Sept) | 1,300 |
| Millicoma River | 151 | 2,200 (Feb) | 30 (Sept) | 870 |
Sedimentation and depositionEdit
As of 1975, the Coos Bay has experienced a greater influx of sediment than output.<ref name="Roye-1979" /> Such sediment includes silt from drainage basin erosion, and various sands (marine sand, dune sand, South Slough cliff sand) due to erosion in the surrounding areas.<ref name="Eidam-2020" /><ref name="Roye-1979" /> Sediments are formed and moved via streams, littoral drift, or transport of sediments along a coastline parallel to the shore, processes due to wind activity, and erosion.<ref name="Eidam-2020" /> Sediment grains increase in size with depth and decrease in size when moving further into the estuary, likely because tidal currents are less strong further in and can no longer carry larger particles.<ref name="Rumrill-2008" /> To keep the estuary fit as a navigation channel, an average of 1.65 million square yards of material was removed annually by the US Army Corps of Engineers prior to the start of the Deep-Draft Navigation Project.<ref name="Roye-1979" /> Sediments input averages 72,000 tons annually.<ref name="Percy-1974" />
Modeling of Coos Bay sediment movement compared to historical patterns reveals that suspended-sediment concentrations and sediment retention has increased in the estuary over time as dredging, river diversion, construction and spoils disposal continues.<ref name="Eidam-2020" /> As a result of this development, sediment transport has been diverted into the central navigation channel, where more sediment is accumulating.<ref name="Eidam-2020" /> Tidal flat sediment retention has also increased.<ref name="Eidam-2020" />
BiogeochemistryEdit
Tides and upwellingEdit
Seasonal winds cause tides and upwelling that influence nutrients and the biogeochemistry of Coos Bay estuary. One third of macrophyte production in the estuary is attributed to upwelling.<ref>Template:Cite journal</ref> In the summer, wind primarily comes from the North along the Oregon coast, bringing up nutrient-rich deep water and boosting primary production.<ref name="Sutherland-2016">Template:Cite journal</ref> 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.<ref name="Rumrill-2008" /><ref name="Roye-1979" /> In 2000, the difference in semi-diurnal high and low tides was on average 0.3-0.5 m, and the average tidal amplitude between Mean Higher High Water and Mean Lower Low Water was about 2.1 m.<ref name="Rumrill-2008" /> The tidal prism, or the amount of water between mean high tide and mean low tide, accounts for 30% of the estuary's volume.<ref name="Eidam-2020" /> Estuary mixing and stratification is dependent on the tidal flux and river flux. Circulation patterns are also tidally-influenced.<ref name="Rumrill-2008" /> In the summer, the estuary is well-mixed, but in the winter it is highly stratified.<ref name="Eidam-2020" /><ref name="Sutherland-2016" /> Furthermore, in the summer months saltwater influence is greater as freshwater flow into the estuary is minimal.<ref name="Rumrill-2008" /> Following anthropogenic deepening and widening, the estuary has a 33% greater mean tidal amplitude and 18% more salinity intrusion length.<ref name="Eidam-2020-2" /><ref name="Eidam-2020" />
NutrientsEdit
Nitrogen inputs vary seasonally and along the salinity gradient.<ref name="Schrager" /> Increased precipitation during the wet season is a major input of land-based nitrogen, as is the watershed associated with agricultural nitrogen runoff and red alder nitrogen fixation. Oregon Coast Range streams typically contain higher amounts of nitrate compared to other Pacific Northwest streams due to the healthy population of red alder trees capable of fixing nitrogen.<ref>Template:Cite journal</ref> During the dry season, the major input of nitrogen comes from the ocean following upwelling events bringing nutrients like nitrogen into the estuary.<ref>Template:Cite journal</ref> 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.<ref name="Rumrill-2008" /> In the winter, during peak freshwater inputs, nitrate concentrations are high and fairly uniform throughout the estuary.<ref name="Rumrill-2008" /> This indicates that in the dry season, nutrient sources come from the Ocean, while in the wet season, nutrients are coming in with the freshwater.<ref name="Rumrill-2008" /> During summer months when dry conditions persist and upwelling is occurring, the primary source of phosphorus is from the ocean.<ref>Template:Cite book</ref> Thus, phosphorus concentrations also vary depending on location in the estuary, on the ocean end or riverine end.<ref name="Schrager" />
ChemistryEdit
Roughly half of the total organic matter within the Coos Bay estuary is stored organic carbon within sediments. Clay and silt particles typically have the highest concentrations of organic matter associated with them.<ref name="Folger-1972">Template:Cite journal</ref> 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.<ref name="Folger-1972" />
Similar to nitrogen and phosphorus, chlorophyll is dependent on upwelling and tidal mixing and varies along the salinity gradient.<ref name="Schrager" /> These physical processes influence estuarine chlorophyll by either directly transporting chlorophyll associated with plants from coastal waters into the estuary or by transporting recently upwelled, nutrient rich water, into the estuary which triggers primary production.<ref>Template:Cite journal</ref>
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.<ref name="Sutherland-2016"/><ref name="Johnson-2019" /> These values [ambiguous] and pH are also monitored at various locations throughout South Slough.<ref name="Rumrill-2008" /> In the wet winter season (December - February), the bottom water measured in the tidal waters of South Slough at Valino Island tends to be relatively cold, with temperatures ranging from 5° to 11 °C and highly variable salinity (0-20 psu).<ref name="Rumrill-2008" /> In the spring (March–May), temperatures increase to 13° to 23 °C and salinity becomes more stabilized (27 ± 4 psu) due to is less freshwater input.<ref name="Rumrill-2008" /> During the dry summer season (June - August), bottom temperatures increase to around 15 °C and salinity increases with less variability (31 ± 3 psu).<ref name="Rumrill-2008" /> In the fall (September - November) temperatures drop and salinity becomes more variable (30 ± 5 psu).<ref name="Rumrill-2008" /> Similar patterns are expected throughout the estuary, although location within the estuary will alter dynamics and values.
Seasonal variations of dissolved oxygen include relative highs in the fall and winter (Dec - Jan; >8 mg L−1) with fluctuations across the estuary and lows in the spring and summer during the upwelling season (Apr - Sep; close to 5 mg L−1), with some variation.<ref name="Sutherland-2016"/><ref name="Rumrill-2008" /> Lowest dissolved oxygen levels are found in the mouth in the spring and at the riverine end in late summer and early fall.<ref name="Sutherland-2016"/><ref name="Rumrill-2008" /> While upwelling does bring oxygen-poor water to the surface, upwelling strength alone is not a good predictor of low dissolved oxygen levels; the influence of other physical and biological factors are also needed to explain patterns of oxygen concentration.<ref name="Sutherland-2016"/> Overall, there is minimal likelihood of hypoxia due to rapid tidal exchange and shallow waters, based on the established dissolved oxygen content of the estuary throughout the year.<ref name="Rumrill-2008" />
South Slough did not exhibit any distinct seasonal pattern in pH at any of the monitoring sites, instead remaining within 7.5 and 8.2 year round at Valino Island.<ref name="Rumrill-2008" /> pH tends to be lower in the more riverine locations, between 6.5 and 7.8.<ref name="Rumrill-2008" /> However, there were strong daily fluctuations in pH following the tides and daylight at all monitoring sites, as shown by strong correlation with conductivity and salinity.<ref name="Rumrill-2008" />
Generally, levels of nutrients, salinity, specific conductivity and chlorophyll are at healthy levels in the estuary, as are water temperature, oxygen, and pH.<ref name="Schrager" />
PollutionEdit
Historically, Coos Bay has been subject to a range of pollutants from different sources from logging mills, boat manufacturing, and runoff. The area is also particularly vulnerable to any oil or chemical spills at the International Port of Coos Bay, due to its strong tidal currents.<ref name="Schrager" /> The Oregon Department of Environmental Quality (DEQ) began collecting samples of pollutions and contaminants in the late 1990s, and found that one of the largest sources of pollution into the Coos Bay estuary had been from tributyltin (TBT) sourced from two active shipyards within the estuary.<ref name="Cumberland-2003">Template:Cite journal</ref> TBT became an environmental concern in the late 1980s after commercial oyster farmers began noticing shell deformities.<ref>Template:Cite book</ref> 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.<ref name="Cumberland-2003" /> Southeast of Coos Bay is one of the state's largest coal fields with an area of 250 sq miles. Groundwater seepage from this coal field historically has also been a source of pollution.<ref name="Percy-1974" />
Ecology and biologyEdit
Plant lifeEdit
Plant life in Coos Bay supports biodiverse ecosystems contained within this watershed, ranging from forests in the uplands to eelgrass meadows in the bay. The forested regions of Coos Bay have been logged at least once in the past century, and some of these areas were replanted solely with Douglas fir trees.<ref name="Schrager" /> Sitka spruce, western hemlock, and Port Orford cedar trees can also be found in Coos Bay watershed, ranging from 15- to 75-years of age.<ref name="Schrager" /> Key upland area plant life also include evergreen huckleberry, Pacific sword fern, salal and salmonberry.<ref name="Schrager" /> Fresh and tidal marsh plants include baltic rush, fleshy jaumea, Lyngby's sedge, Pacific silverweed, pickleweed, salt grass, seaside arrowgrass, skunk cabbage, Slough sedge, salt-marsh bird's beak, western bog lily, and tufted hairgrass.<ref name="Schrager" />
EelgrassEdit
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In the aquatic regions, eelgrass (Zostera marina and Zostera japonica) covers about 1,400 acres of Coos Bay.<ref name="digital.osl.state.or.us"/><ref name="Hoffnagle-1974">Template:Cite book</ref> 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.<ref name="Rumrill-2008" /> The beds provide cover for predators and prey alike, including ecologically or economically important fish (see Fish section below).<ref name="Rumrill-2008" />
Eelgrasses are clearly important to the ecosystem, but they are also vulnerable to disruption. During a study in 1996, the density of eelgrass (Zostera marina) plants decreased by 59.4% over a period of 75 days on plots undergoing mariculture of Pacific oysters compared to only a 28.8% reduction in the control plots.<ref name="Rumrill-2008" /><ref name="Rumrill-1996">Template:Cite journal</ref> 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.<ref name="Rumrill-2008" /><ref name="Rumrill-1996" /> Following removal of these mariculture practices, Z. marina beds struggled to recover, and recovery depended most on how many Z. marina plants there were at the start of recovery, rather than on new growth.<ref name="Rumrill-2008" /><ref name="Pregnall-1993">Template:Cite journal</ref> However, transplanted Z. marina did recover better than plots left to recover on their own.<ref name="Rumrill-2008" /><ref name="Pregnall-1993" /> Aside from anthropogenic influences, eelgrass is also affected by other factors. A study on Z. marina meadows in Coos Bay from 1998 to 2001 found that Z. marina is more dense in areas with higher salinity and lower temperature; gradients which vary within the estuary depending on location.<ref name="Thom-2003">Template:Cite journal</ref> 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.<ref name="Thom-2003" />
Japanese eelgrass (Zostera japonica) is an invasive species, likely introduced during commercial oyster cultivation in 1970 or earlier.<ref name="Rumrill-2008" /> The distribution of Z. japonica has spread from the upper reaches of South Slough in the 1970s into the middle region of the estuary by 1987.<ref name="Rumrill-2008" /> By the early 1980s it is everywhere in the estuary, most commonly in the mid intertidal zone.<ref name="Rumrill-2008" /> Z. japonica converts unvegetated mudflats into eelgrass beds, leading to significant changes in the species composition and abundance of invertebrate communities of the area.<ref name="Rumrill-2008" /> Overall, species richness was significantly higher in Z. japonica dominated areas than it was before the invasion.<ref name="Rumrill-2008" />
AlgaeEdit
A variety of algae can be found in Coos Bay. Micro-algae or Phytoplankton, such as diatoms, are abundant. Coos Bay has some of the highest primary productivity within west coast estuaries.<ref name="Cumberland-2003" /> In the lower part of the bay, species such as Chaetoceros, Skeletonema, and Thalassiosira are found. In the upper part of the bay, species such as Melosira and Skeletonema are found.<ref name="Hoffnagle-1974" /> As of 1973, zooplankton were most abundant near the ocean, and numbers tended to decrease further into the bay. Neritic (swimming) species were found in the lower parts of the estuary.<ref name="Hoffnagle-1974" /> In a typical year, there is a small bloom of diatoms in the late winter and early spring before heavy grazing pressure by the zooplankton limits overall abundance. Lack of sunlight limits diatom growth in the fall and winter.<ref name="Rumrill-2008" /> Most algae are found at the mouth of the bay, and notably there is a shift in species from marine to brackish water plants here.<ref name="Hoffnagle-1974" /> Kelp beds, specifically those of bull kelp (Nereocystis leutkeana), are found in the bay as well.<ref name="Hoffnagle-1974" />
FishEdit
Coos Bay provides habitat for both residential and anadromous fish. The South Slough is an essential nursery environment for many marine fish in their larval and juvenile life stages.<ref name="Rumrill-2008" /> Near the mouth of the bay, perch, sculpin, and rockfish are found.<ref name="Percy-1974" /><ref name="Schrager" /> Surveys in the South Slough, the most commonly studied portion of Coos Bay, have shown that Shiner perch are the most abundant fish in the estuary.<ref name="Rumrill-2008" /> Shiner perch comprise 76% of fish caught by seine, and typically have a strong association with the eelgrass beds.<ref name="Rumrill-2008" /> Staghorn sculpin are another dominant species.<ref name="Rumrill-2008" /> Many of the residential species, Shiner perch included, move into the tidal flats during flood tides.<ref name="Rumrill-2008" /> Overall, the fish biomass abundance decreases with increasing distance from the ocean.<ref name="Rumrill-2008" /> Coho salmon, Chinook salmon, Steelhead, Coastal cutthroat trout, Striped bass, Pacific lampreys, Western brook lampreys and American shad all migrate through Coos Bay during different times of the year.<ref name="Percy-1974" /><ref name="Schrager" /> The Coos Bay estuary provides critical habitat for many of the juveniles of these species that have migrated upriver to spawn.<ref name="Rumrill-2008" /> Historically, White sturgeon, Green sturgeon, and Chum Salmon could also be found in Coos Bay.<ref name="Oregon Department of Fish and Wildlife">Oregon Department of Fish and Wildlife; Citizen Advisory Committee (1990). "Coos River Basin Fish Management Plan Template:Webarchive" (PDF). University of Oregon. p. 7. Retrieved November 9, 2022</ref>
ShellfishEdit
Some of Oregon's most productive shellfishing is in Coos Bay.<ref name="myodfw.com" /> Coos Bay is Oregon's largest bay, and the lower part of the bay offers many shellfishing opportunities such as crabbing and clamming.<ref name="myodfw.com">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="myodfw.com" /> Gaper, Cockle, Butter, Littleneck, Razor and Softshell Clams have all been found in the bay.<ref name="Percy-1974" /> Various species of clams were commercially harvested up to 1985.<ref name="Oregon Department of Fish and Wildlife" /> Dungeness crab are also frequently caught by recreational fishermen inside the bay.<ref name="Oregon Department of Fish and Wildlife" /> Ghost and mud shrimp are also found in the tidal flats and are harvested by both recreational and commercial fishermen for use as bait.<ref name="Oregon Department of Fish and Wildlife" />
In the South Slough, Polychaetes (e.g. annelid worms) comprise 38% of the genera found, making them the most diverse in the ecosystem. In contrast, Decapods (e.g. crabs) comprise only 16%, and Bivalves (e.g. clams) only 13%.<ref name="Rumrill-2008" /> Generally, species composition decreases with increasing distance from the ocean.<ref name="Rumrill-2008" />
WildlifeEdit
Mallard Ducks, Pintail Ducks, Widgeon, Marbled murrelet, and Coot all live in the estuaries.<ref name="Percy-1974" /><ref name="Schrager" /> The more migratory species of Canvasback ducks, Pintail ducks, and Black Brant winter in the estuaries.<ref name="Percy-1974" /><ref name="Schrager" /> Many of the seabirds typically found along Oregon's coast such as pelicans and gulls can also be seen in the bay.<ref name="Rumrill-2008" /> Seals and sea lions can typically be seen in the marine dominated zones.<ref name="Rumrill-2008" /> River otters can be found further up in the estuary.<ref name="Rumrill-2008" /> The fresh and tidal marshes are home to American beavers.<ref name="Rumrill-2008" /> Roosevelt elk live in the uplands.<ref name="Rumrill-2008" />
Tidal marshesEdit
Tidal marshes are marshes that are found along the coast and experience regular tidal flooding and draining. They are important because they provide protection against storm surges, reduce erosion, improve water quality, support a biodiverse ecosystem, and provide opportunities for recreation, which boosts the local economy.<ref name="Stevens">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Stevens" /> The soils of tidal marshes tend to be salty and hypoxic, with vegetation adapted for regular precipitation and tidal flooding.<ref name="Stevens" /> These areas are especially vulnerable to changes in these systems, especially rising sea levels.<ref name="Stevens" /> The National Oceanic and Atmospheric Administration and the National Estuarine Research Reserve System work together to assess the resilience of tidal marshes around the country and provide recommendations for their management and conservation.<ref name="Stevens" /> Coos Bay is composed of several types of tidal marshes, according to reports from 1974,<ref name="Hoffnagle-1974" /> 1979,<ref name="Roye-1979" /> and 2021:<ref name="www.oregon.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.
| Marsh Type | Area (acres) |
|---|---|
| Low silt marsh | 71.6 |
| Low sand marsh | 289.1 |
| Immature high marsh | 1000.5 |
| Mature high marsh | 97.5 |
| Sedge marsh | 353.5 |
| Bullrush and sedge marsh | 149.8 |
| Diked Marsh | 3942.9 |
| Surge plain | 285.0 |
| Total undiked marsh | 1951.9 |
| Total diked marsh | 3942.9 |
South SloughEdit
The South Slough, a sub-basin of the Coos watershed, is particularly well studied.<ref name="Schrager" /> The South Slough National Estuarine Research Reserve, spanning 4,771 acres, was the first estuary protected by the National Estuarine Research Reserve in 1974.<ref name="Cumberland-2003" /><ref name="www.oregon.gov" /><ref name="coast.noaa.gov">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Stevens" /><ref name="coast.noaa.gov" /><ref name="Schrager" /> Monitoring includes both water quality, ecosystem surveys, and measurements of resilience.<ref name="Stevens" /><ref name="coast.noaa.gov" /> The National Oceanic and Atmospheric Administration and the National Estuarine Research Reserve System rated South Slough as more vulnerable than the national average because its tidal range is small and most of the vegetation is below the mean tide.<ref name="Stevens" /> Additionally, most of the edges of the marsh are un-vegetated.<ref name="Stevens" /> However, South Slough was rated higher than average for adaptive capacity because there is a lot of space for marsh migration as sea levels rise; recommendations for management include protecting these surrounding areas.<ref name="Stevens" />
The diverse ecosystems that encompass the South Slough Reserve include salt marshes, eelgrass beds, sand, mud, and tidal flats, freshwater ponds and marshes, and even benthic habitats in the deep open channels.<ref name="Schrager" /><ref name="coast.noaa.gov" />
ThreatsEdit
Threats to the biodiversity of Coos Bay watershed include invasive species, forest pathogens, and wildfire. Green crabs, a species native to Europe,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> are invasive in Coos Bay.<ref name="www.oregon.gov" /> One of the species of eelgrass, Zostera japonica, is also invasive.<ref name="Seagrasses and Algae in the Lower Coos Watershed | Partnership for Coastal Watersheds-2020">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Through 2015, seagrass saw an increase in abundance,<ref name="Seagrasses and Algae in the Lower Coos Watershed | Partnership for Coastal Watersheds-2020" /> but Oregon State researchers have suggested that there has been a recent precipitous decline in seagrass mean density in parts of South Slough after a peak in 2015.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Additionally, boats and ships have accidentally introduced terrestrial plant species such as gorse, English ivy, reed canary grass, and Spartina spp.<ref name="Schrager" /><ref name="www.oregon.gov" /> The South Slough Research Reserve is aware of these species and, according to its 2017-2022 Management Plan, is "motivated to minimize their damaging effects early."<ref name="Schrager" /> Douglas fir trees may experience swiss needle cast as a result of contracting the fungal infection Nothophaeocryptopus gaeumannii.<ref name="www.oregon.gov" /> This results in stunted growth. Port Orford cedars and sometimes Pacific yews contract root rot from Phytophthora lateralis.<ref name="www.oregon.gov" /> This rot moves up the tree and kills the inner bark, thereby leading to the death of the tree.<ref name="www.oregon.gov" /> Furthermore, wildfire risk continues to increase as global climate change leads to hotter and drier conditions.
Historical usageEdit
Native AmericansEdit
The estuary is land of the Coos and the Coquille––specifically the Miluk people––who have lived in the area for approximately 6,000 years.<ref name="Schrager" /><ref name="www.oregon.gov" /> The flora and fauna of the watershed provided significant amounts of food and material for hunting and shelter. Villages generally homed around 100 people. Shortly after European settlers arrived in the 1850s, the Natives were forcibly removed and forbidden to return to their land. In the 1870s, "eligible" Natives were allotted a plot of land on which they could rebuild homes. This program was deeply ingrained within colonization, and therefore promoted assimilation in the Euro-American culture. Today, the Coos peoples are a part of the Confederated Tribes of the Coos, Lower Umpqua, and Siuslaw Indians.<ref name="www.oregon.gov" />
Edit
The estuary has a long history of dredging, deepening, and spoil disposal, dating back to early development in the mid-1800s.<ref name="Eidam-2020" /> In 1976, the Coos Bay was dredged as part of the Deep-Draft Navigation Project, a campaign by the US Army Corps of Engineers to increase channel depth and width for vessel usage.<ref name="Roye-1979" /> In its natural state, the estuary's entrance was approximately 200 feet wide and 10 feet deep; this project altered the entrance to measure 700 feet wide and 45 feet deep.<ref name="Roye-1979" /> Total estuary volume has increased 21% while the total estuary areas has decreased by 12%.<ref name="Eidam-2020-2" /><ref name="Eidam-2020" /> In contrast, 25 km2 of the estuary in South Slough has been managed by the National Estuarine Research Reserve and left unaltered by development.<ref name="Eidam-2020" /> A harbor and bridge were constructed in the entrance of South Slough, and the entry point of Coos River into the estuary has been redirected to the west, partially separating it from the east-estuary flats.<ref name="Eidam-2020-2" /><ref name="Eidam-2020" /> As a result of this, modeling reveals, the estuary has overall become more stratified and accumulates more sediment than it did historically.<ref name="Eidam-2020-2" /> Further deepening of the navigation channel from 11 to 14 m and widening by about 45 m has already been proposed for the western reach.<ref name="Eidam-2020-2" /><ref name="Eidam-2020" /> The navigational channel of Coos Estuary is regularly dredged to this day to allow for commercial shipping.<ref name="Schrager" />
PresentEdit
Currently, the greater Coos County––which encompasses the watershed––is home to over 64,000 people. A 2014 community report ranked the area poorly in climate adaptation, greenhouse gas mitigation, and resource efficiency, along with a few social and community aspects.<ref name="www.oregon.gov" />
EconomyEdit
Fisheries and aquacultureEdit
Coos Bay hosts several oyster aquaculture operations. Clausen's Oysters is located in Haynes Inlet at the north end of the estuary.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Qualman Oyster Farms is located near the entrance to South Slough.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Additionally, clams are harvested recreationally.<ref name="www.oregon.gov" /> Charleston acts as a port for many commercial vessels that fish off of Oregon's coast. Similar to other ports in Oregon, these fisheries include Dungeness crab, Pink shrimp,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Pacific whiting, Chinook salmon, Albacore tuna, and Pacific halibut.<ref name="Port of Coos Bay - Oregon's Seaport-3" /> The prominence of these industries promotes good water quality maintenance.<ref name="www.oregon.gov" />
Shipping portEdit
The Port of Coos Bay is one of the largest and deepest ports between San Francisco, California and the Columbia River.<ref name="Port of Coos Bay - Oregon's Seaport">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The majority of cargo is offloaded in the southeast corner of Coos Bay,<ref name="Port of Coos Bay - Oregon's Seaport-2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> which is near the head of the inlet, opposite the Coos River entrance. Currently, 2 million tons of cargo move through the port.<ref name="Port of Coos Bay - Oregon's Seaport-2" /> There are plans to widen the channel from 300 ft to 450 ft and to deepen it from 37 ft to 45 ft, allowing the shipping operations to scale up.<ref name="Port of Coos Bay - Oregon's Seaport" /> Coupled with the Coos Bay Rail Line, which threads through the Oregon Coast Range to Eugene, the port could see increased usage in coming years.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Natural gasEdit
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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
External linksEdit
- 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