How Puget Sound Works
If you've ever wanted to know more about how Puget Sound works...
Read this explanation by SeaDoc chief scientist Joe Gaydos. It's a transcript of a talk he gave in August of 2009. You can also download a transcript of the report (with images).
Puget Sound and a National Ocean Policy
Meeting Sponsored by The Ocean Foundation Seattle, Washington August 24, 2009
Puget Sound Natural Resources Overview
Presentation made by Joe Gaydos, The SeaDoc Society
Hi my name is Joe Gaydos and I’m the Chief Scientist for the SeaDoc Society. We are a science-based marine conservation program focused on the Puget Sound region. But today, instead of boring you with confidence intervals, stable isotope techniques and modeling, I’d like to use the scientific information we have to tell you a little about what make Puget Sound so special. As David Dicks commented, this could be a very short talk, “Puget Sound is cool,” but I’m going to expound on that a bit.
Puget Sound is the Washington portion of a 17,000 sq km inland marine sea, an ecologically discreet area extending from Olympia in the south north to Campbell River and out to Cape Flattery. Next to the Chesapeake Bay, it is 2nd largest estuary in the United States. And although we can compare it in size to other estuaries, that really doesn’t do it justice. There’s really no other place like Puget Sound.
Puget Sound has unique geology, hydrology and biology. One thing you’ll notice first is that we’re not just talking about an inland sea as a body of water we’re talking about a well defined marine ecosystem that also is surrounded by some of the world’s most beautiful mountains. We have the Olympic Mountains and the Vancouver Island Range on the West and the Cascade Range on the east. And it’s these mountain ranges that help create the highly variable local climate patterns and a diversity of habitat types and species, from alpine meadows to the depths of Puget Sound. Just as you see this bold topography in the mountains surrounding the marine water, the striking variability in regional topography continues underwater in the form of steep bathymetry, resulting in very deep water close to shore.
Thanks to a series of glacial events, the last one ending about 10,000 years ago, Puget Sound is characterized by deep fjords and glacial sediments. The shoreline slopes steeply, and because light can only penetrate so far, Puget Sound has only a narrow fringe of vegetated habitat near the shoreline when compared to other estuaries such as the Chesapeake Bay.
Puget Sound is known as a rainy area, but the weather actually is a bit more complex. Beginning about mid-October, a semi-permanent low pressure cell, commonly called the Aleutian Low, intensifies and migrates southeastward over the Aleutian Islands and Gulf of Alaska. Surface winds blow in a counterclockwise circulation around the Aleutian Low; further south, winds blow in a clockwise circulation around a semi-permanent center of high pressure typically centered offshore of southern California. Together, these high- and low-pressure cells typically bring moist, mild, onshore flow into the Pacific Northwest from
October through early spring. As the moisture-laden air encounters the Olympic or Cascade Mountains, it rises and cools, and the cooling causes water vapor to condense into liquid cloud and rain drops. Because of the seasonal shifts in large-scale wind patterns, the Pacific Northwest’s wet season typically begins in October, peaks in midwinter, and ends in the spring. About 75% of the region’s annual precipitation falls in the period October–March. In the spring this Aleutian Low retreats to the northwest and becomes less intense, while the high-pressure cell to the south expands northward and intensifies resulting in reversal where very few storms actually reach the coast.
While the west slopes of the Cascade and Olympic Mountains receive enormous quantities of rain and snow, exceeding 200 inches of water a year, we also have some locations like Sequim or the San Juan Islands that just receive a fraction of that – rainfall in the region of 32 inches a year, or half of that seen in Seattle. These relatively dry areas lie in “rain shadows” of the Olympic Mountains.
Puget Sound’s circulation is driven by tidal currents, the surface outflow of freshwater from Puget Sound rivers and deep inflow of saltwater from the ocean. This is influenced by wind strength and direction. Circulation also is modified by underwater sills that lie at Admiralty Inlet, the mouth of Hood Canal and at the Tacoma narrows. Fresh water originates from the snow packed mountains, both during winter rain events and from the spring melt – draining about 43,000 km sq.
It moves down multiple major river systems putting fresh water into Puget Sound. These rivers include the Nooksack, Skagit, Stillaguamish, Snohomish, Duamish, Puyallup, Nisqually, and the Deschutes and on the Olympic Peninsula, Skokomish, Quilcene, Dungeness, Elwha The major sources of fresh water from Puget Sound river systems are from the Skagit and Snohomish watersheds in the Whidbey Basin, however, the majority of the fresh water coming into this inland sea comes primarily through the Fraser River. This fresh water brings nutrients, sediment, and many other things as it runs off the earth. This freshwater is more buoyant than the salt water and travels out over the surface of the sound.
Unlike the buoyant fresh water, salt water is denser and comes through the Juan de Fuca Strait at depth. The quality of this sea water differs depending on ocean conditions, storms and winds. At times, we have winds from the north that push water off the coast at the surface so water from the deep enters Puget Sound, this upwelling brings water that doesn’t have much oxygen, but lots of nutrients. Other times winds from the south push water onto the coast, creating down welling and water entering the sound is oxygen rich and nutrient poor. And because of Puget Sound’s long distance from the Ocean Puget Sound’s tidal zone is unusually large for its latitude, resulting in world-class conditions for shellfish.
Combined with its bathymetry, these tidal exchanges when forced through relatively shallow areas can create routinely currents up to 9 knots as seen here a deception pass. For example, while currents in Puget Sound’s main basin (with average depths of 200 m) or more, might be less than 0.25 meter per second, currents at Admiralty Inlet (with average depths of 40– 80 m), can be as large as 2.2 meters per second.
Note, the movement of water due to tides is about 5–10 times larger than the actual estuarine circulation observed throughout the Sound. As the tidal currents flow past points of land, the water forms eddies in the lee of the points. These tidal eddies provide a transport mechanism for offshore water to reach the shoreline, bringing nutrients and plankton to nearshore communities.
So what you have is a complex system whereby freshwater inflow, saltwater inflow, bathymetry, and wind combine to create a very rich biological system. Puget Sound has about 2,500 miles of shorelines. The exchange of water, sediment, and nutrients between the land and sea is fundamental to the formation and maintenance of an array of critical habitat types and it’s this high diversity of marine shorelines contributes to the high diversity of habitats. These include rocky shorelines, beaches, embayments and estuaries.
And remember, these shorelines also contain some of the most productive low to mid elevation forests in the world. Today 45% of WA is covered in these forests. While most are logged and re-planted, we still have almost 3 million acres, that’s about 3.6 times the area of Rhode Island. And these highly temperate forests support a huge diversity of species. In fact, a recent study showed that when you combine terrestrial and marine species, the Puget Sound area has about 7,000 species across our 16,000 sq mile basin.
And, from a marine perspective, Puget Sound is in keeping with Kruckenberg’s assertion that temperate estuaries are generally among the biologically richest marine areas in the world. In fact, we have about 3,000 species of marine invertebrates, which undoubtedly contribute to making this area Jacques Cousteau’s 2nd favorite place in the world to dive when he was still alive, I never asked him his first, but I imagine it was the place he was diving that day! Even our sea slugs are amazing, as you see with this white-lined dirona or this leopard dorid.
And while many people know about Puget Sound being home to the North Pacific Giant Octopus (Enteroctopus dofleini) is the largest octopus in the world ; we actually have many “largests.” Cryptochiton stelleri, also known as the giant pacific chiton, is the largest of the chitons growing to 33 to 46 cm. Balanus nubilis, the largest barnacle, which can measure 15 cm across and 30 cm tall. The plumose anemone Metridium senile; is the world’s largest sea anemone; which can grow to be a meter tall. But it’s not just size, its age too, we have the largest burrowing clam, the geoduck (Panopea abrupta), which can live to be 100 years old and the red urchin (Strongylocentrotus franciscanus) that can live to be over 150 years old.
In 1999, this region was noted as one of the World Wildlife Fund’s priority conservation ecoregions in the world because of 1.Our highly productive low and mid-level temperate forests, which I already discussed; 2.The fact that many of our marine species, many of which I just pointed out, are genetically and distinctly different from those on the open ocean, and 3. Because we are at the southern end of the zone that supports the greatest diversity of salmon (Oncorhynchus) species. Not only do we have all 5 species of Pacific Salmon, we also have steelhead (sea run rainbow trout, Oncorhynchus mykiss) and sea run cutthroat (Oncorhynchus clarki) as well as bull trout (Salvelinus confluentus), which we recently learned move into the marine waters to forage before returning up rivers.
And, compared to other regions, we produce an estimated 510x as many salmon as the entire legendary Columbia River basin; we appear to be dwarfed in numbers by the production of BC and Alaska, however when adjusted for the fact they are 38 and 45 times larger, we actually historically outcompeted both places, and to a certain degree, still compete with them today. But while we’re better known for our salmonids, we actually have about 230 species of marine and anadromous fishes; such as the red Irish lord (Hemilepidotus hemilepidotus). We have the Cabezon (Scorpaenichthys marmoratus), which is the world’s largest Sculpin. We have 25 species of rockfish; like this copper (Sebastes caurinus) which can live to be 50 years old or the quillback (Sebastes maliger) that can live to be 90 years old, or the yellow eye rockfish (Sebastes ruberrimus) that can live to be 118 years old.
We also have about 165 species of birds that depend on the marine ecosystem ranging in size from the 4,000 gm Bald Eagle (Haliaeetus leucocephalus) to the to the 25 gm Western Sandpiper (Calidris mauri). And not only are many of these species fascinating in their own right, such as the Western grebe (Aechmophorus occidentalis) that is so aquatic, after spending an entire winter on Puget Sound, fly inland to breed on freshwater lakes, where they construct floating nests. We have 8 different species of alcids, which are the northern hemisphere cousins of penguins that use their wings to fly underwater as they catch fish. We are beginning to realize, that these birds, even migratory ones like the Surf Scoter (Melanitta perspicillata), actually depend on Puget Sound in ways we couldn’t have imagined. You see, although these birds winter here, many birds like these scoters make huge migrations. This is a satellite tracking of scoters where we implanted satellite transmitters on these birds and a recent SeaDoc funded project demonstrated that in many years, Surf Scoter fattening on herring spawn can be a critical determinant of nesting success when these birds fly north.
Puget Sound also has a wide array of marine mammals. Where 18 states and one Canadian province are spending millions of dollars restoring river otter (Lontra canadensis) populations, we have a thriving river otter population that forages in the marine waters and 9-10 times a day brings marine derived nutrients onto the land via latrine sites and marking. While numbers are plummeting in parts of Alaska, Puget Sound’s has a harbor seal (Phoca vitulina) population that’s been at carrying capacity for a decade, and in the county where I live, we have 1 seal for every 3 people.
We are a major wintering site for both Steller (Eumetopias jubatus) and California sea lions (Zalophus californianus). Elephant seals (Mirounga angustirostris) are moving into the area as their population expands and we are a major stopping off site for grey whales (Eschrichtius robustus) that migrate from the Bering Sea to Baja and back. Humpback whales (Megaptera novaeangliae) that once were extirpated are now returning and of course, we have the flagship Southern Resident killer whales (Orcinus orca) as well as 2 other ecotypes of killer whales. Transient killer whales that prey on marine mammals and offshore killer whales; which are probably most closely related to the Southern Residents and are likely fish eaters too.
Puget Sound is unique and it ranks not only as a national treasure, but as one of the world’s treasures. I want to leave you with three ideas to keep in mind about Puget Sound: because of our unique geology and oceanography we are highly productive, biologically diverse, and unique in the US and the world. Puget Sound needs to be saved and the lessons learned and tools used here will benefit other coastal ecosystems around the world. I thank you for taking an interest in this region.
Note: Pictures provided by J. Gaydos, N. Maher, J. Nichols, and J. White. For more information on the SeaDoc Society see: www.seadocsociety.org