Netarts Bay Salt Marsh


Channel patterns and small brackish ponds in the salt marsh at the south end of Netarts Bay.  The tracks cutting across the channels are the remains of an old dike. Dikes such as this one along with water gates were used to drain a marsh and and divert water flows to make it suitable for pasture (Saliskar and Gallagher, 1983) and the harvest of marsh hay (tufted hair grass) (Stout ed., 1976).


Channel patterns in the marsh at the head of Netarts Bay, Oregon.  The dashed line indicates the position of an old dike (reproduced from Seliskar and Gallagher 1983).

As you can see in the photo, the southern end of Netarts Bay still has an extensive mature tidal salt marsh, a  low-lying, vegetated landscape that is an interface between marine and terrestrial ecosystems.  Braided and meandering tidal channels penetrate the wetland, serving as conduits that allow saline baywater to move in and out of the marsh, periodically soaking it during high tides.  Tides in the summer months rarely inundate the entire marsh, but during the fall and winter when we have the highest of the high tides, baywater can overflow the banks of the channels, flooding the marshland, sometimes during storms to its terrestrial boundary.  Though Netarts Bay has little freshwater input from streams, there is runoff during heavy rains in fall and winter that can dilute the saline water near the marsh's terrestrial edges.  These conditions of flooding and runoff lead to a salinity gradient through the marsh from the bay edge to the truly terrestrial ecosystem, resulting in a zonation of plants along the gradient with varying degrees of salt tolerance.  Complicating the picture are effects of conditions of the soil such as salinity, moisture, evaporation, aeration, nutrients, and how high it is above sea level.  The salinity gradient is not only vertical, but can have lateral and linear components, contributing to patchy plant distributions. Also, brackish ponds or tide pools may have their own biotic community.

Plants and Their Distribution Across the Marsh

The diagram and photos below represent an actual transect taken on July 22, 2015 across a narrow portion of the marsh adjacent to the dunes on Netarts Spit to illustrate this plant zonation from the saline bay edge, where the most salt-tolerant  plants thrive, to the edge of the dunes above any bay water inundation.  This was a 212-foot transect line starting at the boundary of the mudflat where Japanese eelgrass Zostera japonica gave way to three-square sedge Schoenoplectus americanus.  This point was designated zero inches elevation.  The plants recorded along the transect and to about 20 feet on each side of its line were the more dominant species that form what are known as zonal communities.

Marsh Transect-2

Scientific name                                   Common name

Angelica lucida
Argentina (Potentilla) anserina
Atriplex patula
Carex obnupta
Cytisus scoparius
Deschamsia crespitosa
Distichlis spicata
Elymus mollis
Gallium aparine
Grindelia integrifolia
Hordium brachyantherum
Juncus balticus
Jaumea carnosa
Lathyrus palustris
Lonicera involucrata
Oenanthe sarmentosa
Plantago maritima ssp. juncoides
Polystichum munitum
Pteridium aquilinium
Schoenoplectus americanus
Salicornia virginica
Triglochin martimum
Vicia gigantea
Zostera japonic

Sea watch
Pacific silverweed
Slough sedge
Scotch broom
Tufted hairgrass
Native dune grass
Gum weed
Medow barley
Baltic rush
Marsh pea
Twin berry
Pacific water parsley
Seaside plantain
Sword fern
Bracken fern
Three-square sedge
Pickleweed, saltwort
Giant vetch
Japanese eelgrass


Communities 1 and 2 - three-square sedge (Schoenoplectus) is on the left.


Communities 4 and 5 - dominated by tufted hair grass (Deschamsia), then native dune grass (Elymus).


Community 3 - dominated by Jaumea.


Community 5 - entering dune habitat.

The first 20 feet of transect into the salt marsh, from 0 to 7 inches in elevation contained only three-square sedge.  A Salicornia, Distichlis, Triglochin, Jaumea community dominated the area 20 feet to 100 feet with an elevation change from 7 to 21 inches.  From 100 feet to 150 feet with an elevation change of 21 to 32 inches, Plantago maritima mostly replaced Triglochin.  Between 150 and 190 feet with only an additional 10 inches of elevation, the number of plant species began to increase, and Carex obnupta,  Juncus, Grindelia, and Deschampsia were added.  From 190 feet to 210 feet, the elevation increased dramatically from 42 inches to 76 inches and the transect entered the dunes.  This plant zonation is akin to that found in the more familiar rocky intertidal habitat.  It is not quite as obvious because vertical slope is much less abrupt.

The photos below represent the plants listed in the table next to the graph and found along the transect.


Argentina (Potentilla) anserina

Angelica lucida


Atriplex patula


Carex obnupta


Cytisus scoparius

Deschampsia Distchlis Elymus

Gallium aparine


Grindelia integrifolia

Deschamsia crespitosa

Distichlis spicata

Elymus mollis

Hordeum Jumcus Jaumea Lathyrus-p

Hordium brachyantherum


Lonicera involucrata

Juncus balticus

Jaumea carnosa

Lathyrus palustris

Oenanthe Plantago-mar

Polystichum munitum


Pteridium aquilinium

Oenanthe sarmentosa

Plantago maritima ssp. juncoides

Schenoplectus Salicornia Triglochin Vicia

Zostera japonica

Schoenoplectus americanus

Salicornia virginica

Triglochin martimum

Vicia gigantea

The salt marsh of Netarts Bay is divided into several different types designated by plant species as they are adapted to substrate, salinity, and elevation (Stout ed., 1976; Seliskar and Gallagher, 1983; U. S. Army Corps of Engineers, 1981). The southern end of the bay pictured above is considered a mature high marsh with level, peaty soils and a dendritic network of channels.  Along the western sides of the bay are immature high marshes, relatively level with silty substrates, and  low sandy marshes on sandy substrates with gradual slopes.  The edge of the bay where the three-square sedge grows is a sedge marsh, which is usually flooded at high tides.   See Seliskar and Gallagher (1983) for more comprehensive explanations.  The transect ranged from a sedge marsh to what is probably an immature high marsh bordering on a mature high marsh.

Most plants are seasonal, some making their appearance before or after others.  Below are photos of plants found in the Netarts Bay salt marsh, but not along the transect, because they either bloom at a different time or were in another part of the marsh or type of marsh.


Bolboschoenus maritimus ssp paludosus
Salt marsh bullrush

This is a native found in coastal and inland salt marshes, particularly in the West and Midwest.  This genus along with Schoenoplectus and a couple of other genera was grouped under the single genus, Scirpus, and this is how it appears in the older literature.  I found it in patches living in depressions, ponds during winter, near the old dike in the mature high marsh.


Armeria maritima, ssp. californica
Sea pink, sea thrift

Sea pink is another sand marsh inhabitant that typically blooms in July.  Click here for more information.


Scirpus microcarpus
Small-fruited bullrush

This is a tall, large-leafed sedge common to wetlands, and is locally found in a large patch on the eastern side of the Netarts Bay salt marsh, just inside of the Cape Lookout State Park boundary.


Carex macrocephala
Big headed sedge

This sedge is typical of the sand marshes along the western perimeter of the bay.  Double click here for more information on this plant under greenish flowers in the wildflower section..


Cordylanthus maritimus ssp. palustris
Salt-marsh bird’s-beak

A member of the snapdragon family (Scrophulariaceae), this plant is rare in northern Oregon.  Here, it occurs only in one place in the immature high marsh on the west side of the bay in a strip about 300 yards long and 30 to 40 yards wide, mostly as scattered plants, but one  area of maybe 100 square yards where they are fairly dense.


Cuscuta salina var. major
Salt marsh dodder

Salt marsh dodder is parasitic on Salicornia virginica.  You can see its web of thin, orange stems winding and encircling pickleweed during the summer months.

Those Mysterious Silvery Films in Marshes


Castilleja ambigua ssp. ambigua
Johnny-nip, paintbrush owl's-clover

Johnny-nips appear in midsummer in the immature high marsh and may blanket an area giving it a snowed-on look.  Click here for more information on Johnny-nips.


Rumex aquaticus var. fenestratus (formerly R. occidentalis) Western dock

Western dock usually blooms in May and June, and by mid-July is often dried out, as those are picture here.  It is common at in wet habitats, especially along the upper margins of mature and immature salt marshes.

Atriplex gmelinii

Atriplex gmelinii
Gmelin’s orache

This west coast saltbush in Oregon is found only in Tillamook, Lincoln, and Lane counties.

There is an interesting occurrence in wetlands, including the salt marshes of Netarts Bay, that you may have seen if you have ever ventured into a marsh.  It is a silvery, sometimes iridescent film that floats on the water's surface at marsh edges, in pools, and in seeps that looks for all intents and purposes like an oil slick.  And in a sense it probably is, but not from petroleum, though it is often mistaken by people for an oil spill.  It is a mixed organic and inorganic, non-petroleum sheen caused by bacteria breaking down organic matter from decaying plants and animals.  It is a very thin sheet, maybe 150 microns to 500 microns (1/2 millimeter), and an interesting indicator of wetland metabolism 

The film is often associated with rusty-looking wetland sediments, which you may find along some of the muddy shores and channels of Netarts Bay.  These sediments contain iron, and there are so-called "iron bacteria" living in the film that use the metal from these sediments as an energy source.  Depending on the kind of bacteria, the amount of organic material, and the amount of dissolved oxygen in the water, they may either reduce iron oxide in the sediment to ferrous hydroxide or convert the soluble ferrous metal into an oxide.  Dr. Randal W. Smith of Portland State University (Department of Physics), using special  techniques with electron microscopes, has determined the iron in the film is a complex of "mixed-valent"  (Fe2+ and Fe3+) reduced iron and iron oxides and may indicate an incomplete oxidation process.  Other metals such as manganese, nickel, and zinc may be involved as well.  The films are not amorphous but are nanocrystalline, formed of very small crystals. It may be that the ordered crystals begin to form in the mineral when it was in an amorphous state.  Bacteria play an important role in the formation of these films.

How can you tell whether a film is a natural, metallic surface film or one from petroleum?  Poke it with a stick.  If the film breaks up into separate plates, it is a natural metallic surface film.  If it reforms into a single sheet and clings to the stick, it is a petroleum slick. 


Bacteria in an metal-containing surface film (scanning electron micrograph by Dr. Randal W. Smith)


Non-petroleum surface film in the Netarts Bay salt marsh.


Iron-containing sediment and surface films in a salt marsh channel in Netarts Bay.

Estuarine Channels of Netarts Bay

Estuarine Channel Classes

Channels, said Charles Simenstad, "form the estuary's circulatory system" (Simenstad, 1983).   They are the conduits that link marine and riverine ecosystems, and they play a major role in the production of fisheries and wildlife.  Unfortunately, this recognition is only recent.  In the past, estuaries and their channels were exploited for agriculture, industry, and colonization.  Many around the US and the world have been damaged or destroyed.  We are lucky that Netarts Bay, a bar built estuary covering almost 3.5 square miles, along  with its channels, remains mostly intact. 

To the left is a diagram from Simenstad, 1983, of representative estuarine components.  Although Netarts Bay has no river discharge of fresh water (Jackson Creek no longer flows into Netarts Bay), other features in the figure are similar to those evident in the photograph of the salt marsh at the beginning of this article.  You can see in this image of the south end of the bay, the mainstream channels, the adjacent littoral flat (there are few sublittoral flats in this shallow bay), meandering subsidiary channels, and blind dendritic channels within the salt marsh habitat.   In addition to this southern mature high marsh in the photo and the immature high and low sandy marshes along the west side of the bay that are mostly out of the photo, there are small pocket marshes with their own channels along Netarts Bay Road on the east side of the bay near the entrances of small freshwater streams.  Yeager Creek is an example.

A typical channel cross section consist of a somewhat vertical bank, a slope, and a more-or-less level substrate.  Channels in Netarts Bay are either tidal where bay water flows in and out with the tides, or they are drainage channels that formed largely by freshwater runoff that cuts through soil substrates with low resistance or weakly stabilizing vegetation.  Tidal channels, including those that are mainstream, are fairly wide and deep and may not empty completely during low tides.  Drainage channels, such as blind dendritic and subsidiary channels, are usually higher in elevation, and often narrow down to a few inches across near their blind ends.  They flood with bay water only at the highest tides.  Some of these blind channel extend to the perimeter of the marsh and to the edge of the forest.  They may also tunnel under the marsh surface where overlying vegetation is thick and stable.  It has been noted in other marshes that even the smallest channels, some only a few inches wide and deep, can influence plant distributions (Sanderson et. al., 2000).

Most channels meander in a sinuous, snake-like pattern.  This meandering is the result of ebbs and floods of tidal waters that cause the slumping of channel banks, particularly during at ebb flows which, according to Fagherazzi  et. al., 2004, have water velocities stronger that those during flood flows, resulting in differential bank erosions.

Estuarine Cannels low tide

Channels at low tide.

Estuarine Channels high tide

Channels at high tide.

Channel under ground

Drainage channel tunneling under the marsh land.

Channel Soils

Soil in the salt marsh at the south end of the bay and its channels is classified in the jargon of soil science as a "fluvaquents-histosols complex" (USDA Web Soil Survey).  A fluvaquent is a kind of wet soil typical on river banks and tidal mudflats (an aquent) that is produced by frequent flooding, in the case of our marsh, at high tides.  A histosol soil is comprised of mainly organic materials.  Organic carbon, that carbon from decayed biological material, was analyzed in 1976 from numerous sites in the bay (Stout ed. 1976), but not from the marsh channels at the south end.  They found that mud flats on the east side of the bay contained high levels of organic carbon, to over 3.4%.  It is likely that the marsh channels  and their accompanying mud flats contain much more organic carbon because the slow water velocities allow fine sediments and plant debris to accumulate, and the sediment cores I examined contained lots of decayed vegetation and probably animal parts as well.  The grain sizes in the southern part of the bay classify the sediments generally as silty-sands, however the fine silt grains with their large surface areas that are found in the channels and littoral flats are typically associated with high levels of adsorbed organics (Stout ed. 1976), increasing the organic load.

Plant fiber cell walls

Micrograph of cell walls of decayed plant from tidal channel.

Those of you who have dug clams in the bay have undoubtedly encountered a layer of black, rotten-egg- smelling sediments somewhere under the surface, especially in muddy areas where there is little exchange of interstitial water in this soil with overlying waters.  This layer, common in the channels, is called the "sulfide layer", and is produced by sulfate-reducing bacteria, bacteria that thrive in an anaerobic (oxygen-free) environment and reduce sulfates to hydrogen sulfide (H2S), which is the chemical that makes the soil smell like rotten eggs.  Decaying organic matter in these sediments  consumes all the free oxygen, turning them anaerobic and allowing these bacteria to flourish.  The H2S combines with iron in the sediment to form iron sulfide and this turns anaerobic soil black.  If these black soils encounter oxygen, the iron sulfides then oxidize to iron oxides.  It is these iron oxides that can feed the bacteria that produce the silvery surface films we discussed above.

Channel Life

The vertical banks of the channels are fenestrated with holes about a half inch to a couple of inches across.  These are the burrows of the green shore crab Hemigrapsus oregonensis, also called the Oregon shore crab or the mud-flat crab.  This crab is found in quiet waters all along the Pacific coast.  It is a vegetarian, feeding mostly on green algae and diatoms.  It can tolerate the fine sediments in these muddy burrows because a mat of bristle-like setae at the openings to their bronchial chambers, which contain their gills, block the entrance of mud grains.





At the base of the banks of the mainstream channel and extending out into the littoral mud flats are a myriad of small holes a few millimeters in diameter.  These house a small nereid polychaete worm, generally less than two inches long, probably Nereis latescens.

Hemigrapsis holes

Hemigrapsis burrows

Nereis holes

Nereis holes

Hemigrapsis orgonensis

Oregon shore crab Hemigrapsus oregonensis

Nereis latescens

Nereis latescens

A fine-mesh plankton net dragged along the surface of the mud in the mainstream channels captured some prevalent epibenthic crustaceans, one of which is the blacktail bay shrimp Crangon nigricauda.  The common name (and the specific name) of C. nigricauda is misleading in that this shrimp does not always have a black tail.  It feeds on amphipods and is eaten by Dungeness crabs.  The net also captured some gammaridean amphipods.   The amphipod on the left is in the family Aoridae, probably Paramicrodeutopus schmitti, a tube-dwelling family common in estuaries.  The amphipod on the right is Grandidierella japonica is an invasive species from Japan that may compete with our native amphipods. 

Crangon nigrcauda

Crangon nigricauda  

To be continued.

Paramicrodeutopus schmitti

 Paramicrodeutopus schmitti

Grandidierella japonica

Grandidierella japonica


Fagherazzi, Sergio, Emmanuel J. Gabet, and David Jon Furbish.  2004.  The effect of bidirectional flow on tidal channel planforms.  Earth Surf. Process. Landforms 29: 295-309..

Plachinida, P.,  R. W. Smith, S. Rouvimov, E. J. Sanchez, P. Moeck, R. Hugo, and C. Wang.  2011.  Nanocrystalline Structure of Metal Containing Films in Natural Wetlands. Microsc. Microanal. 17 (Suppl 2): 1118-1119.

Seliskar, Denise M. and John L. Gallagher.  1983. The Ecology of Tidal Marshes of the Pacific Northwest Coast: A Community Profile.  U.S. Department of the Interior, Fish and Wildlife Service.  FWS/OBS-82/32.

Senderson, Eric W., Susan L. Ustin and Theodore C. Foin.  2000. The influence of tidal channels on the distribution of salt marsh plant species in Petaluma Marsh, CS, USA. Plant Ecology 146: 29-41.

Simenstad, Charles A. 1983.  The Ecology of Estuarine Channels of the Pacific Northwest Coast: A Community Profile.   U.S. Department of the Interior, Fish and Wildlife Service. FWS/OBS 83/05.

Smith, R.W. and E. J. Sanchez.  2011.  Environmental NanoBiology:  Structural Evaluation Of Natuarally Occurring Transition Metal Oxide-Containing Surface Films From Fresh Water.  Microsc. Microanal. 17 (Suppl 2): 618-619.

Stout, Heather, ed. 1976.  The Natural Resources and Human Utilization of Netarts Bay, Oregon.  Oregon State University, Corvallis, Oregon.

U.S. Army Corps of Engineers.  1981.  Coastal Engineering Technical Note - Value of Pacific Northwest Salt Marshes. U. S. Army Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir. VA CETN-V-12 11/81.

Guides, Keys, and Further Reading:

Barnard, j. Laurens.  1969. The Families and Genera of Marine Gammaridean Amphipoda.  Smithsonian Institution Press, Washington, DC.  535 pp.

Carlton, James T. (ed).  2007.  The Light and Smith Manual, Intertidal Invertebrates from Central California to Oregon.  University of California Press, Berkeley.  1001 pp.

Clark, Lewis J.  2004.  Lewis Clark’s field Guide to Wild Flowers of the Sea Coast in the Pacific Northwest.  Harbour Publishing, Maderia Park, British Columbia.  80 pp.

Gilkey, Helen M., and La Rea J Dennis. 2001. Handbook of Northwestern Plants. Oregon State Univeristy Press, Corvallis, Oregon.  494 pp.

Guard, B. Jennifer.  1995.  Wetland Plants of Oregon and Washington.  Lone Pine Publishing, Renton, Washington.  237 pp.

Hartman, Olga.  1944. Polychaetous Annelids From California including the descriptions of two new genera and nine new species.  Allan Hancock Pacific Expenditions  10:2 and 3.  387 pp.

Hartman, Olga.  1968.  Atlas of Errantiate Polychaetous Annelids From California.  Allan Hancock Foundation, University of Southern California.  828 pp.

Hickman, James C. (ed).  1993.  The Jepson Manual - The Higher Plants of California. University of California Press, Berkeley, California. 1399 pp.

Horn, Elizabeth L.  1994.  Coastal Wildflowers of the Pacific Northwest. Mountain Press Publishing Company, Missoula, Montana.  179 pp.

Knobel, Edward.  1977.  Field Guide to the Grasses, Sedges, and Rushes of the United States.  Dover Publications, New York.  83 pp.

Kozloff, Eugene N.  1983.  Seahore Life of the Northern Pacific Coast.  University of Washington Press Seattle, Washington.  370 pp.

Kozloff, Eugene N.  1996.  Marine Invertebrates of the Pacific Northwest.  University of Seattle Press, Seattle.  539 pp.

Kozloff, Eugene N.  2005.  Plants of Western Oregon, Washington, and British Columbia. Timber Press, Portland, Oregon.  512 pp.

Jensen, Gregory C.  1995.  Pacific Coast Crabs and Shrimp. Sea Challengers, Monterey, California.  87 pp.

Lamb, Andy, and Bernard P. Hanby.  2005. Marine Life of the Pacific Northwest - A Photographic Encyclopedia.  Harbour Publishing, Maderia Park, British Columbia. 398 pp.

Munz, Philip A.  2002. Introduction to Shore Wildflowers of Califonia, Oregon, and Washington. University of California Press, Berkeley, California.  234 pp.

Perkins, E.J.  1974. The Biology of Estuaries and Coastal Waters. Academic Press, London.  678 pp.

Phillips, Caitrin.  (no date) A Visual Identification Guide to the Gammaridean Amphipods of Morro Bay, CA - Order Amphipoda - Suborder Gammaridea.   pdf, California Polytechnic State University, San Luis Obispo.  38 pp.

Pojar, Jim, and Andy Mackinnon (ed).  1994.  Plants of the Pacific Northwest Coast - Washington, Oregon, British Columbia, and Alaska.  Lone Pine Publishing, Vancouver, British Columbia.  526 pp.   

Ricketts, Edward F., Jack Calvin, Joel W. Hedgpeth, David W. Phillips.1985.  Between Pacific Tides (5th ed).  Stanford University Press, Stanford, California. 652 pp.

Rudy, Paul, Lynn Rudy, Alan Shanks (ed), Barb Butler (ed).  2013. Oregon Estuarine Invertebrates, 2nd Edition. pdf, University of Oregon (Draft).  461 pp.

Ruppert, Edward E., Richard S. Fox, Robert D. Barns.  2004.  Invertebrate Zoology (7th ed).  Brooks/Cole--Thompsn Learning, Belmont, California.  989 pp.

Snively, Gloria.  1978.  Exploring the Seashore in British Columbia, Washington and Oregon.  Gordon Soules Book Publishers, Ltd., West Vancouver, British Columbia. 240 pp.

Taylor, Ronald J.  1990.  Northwestt Weeds.  Mountain Press Publishing Company., Missoula, Montana.  177 pp.

Turner, Mark andPhyllis Gustafson.  2006.  Wildflowers of the Pacific Northwest. Timber Press Field Guide, Portland, Oregon.  511 pp.

Visalli, Dana, Derrick Ditchburn, Walt Lockwood,  2005,  Northwest Coastal Wildflowers.  Hancock House Publishers Ltd., Surry, British Columbia.  96 pp.

Wiedemann, Alfred M., La Rea J. Dennis, and Frank H. Smith.  1969.  Plants of the Oregon Coastal Dunes. Oregon State University Press, Corvallis, Oregon.  120 pp.

Text and photos by Jim Young

Return to Site Contents Page