The ecology of eelgrass meadows in the Pacific Northwest: A ...

marina; Figure 5) and the diminutive under consideration. Both can be easily
Zostera japonica. species are found distinquished, not only - by - tidal elevation
on a muddy or mixed mud and sand substrate but al& size. Zostera japonica is a very
in areas sheltered from turbulent Water.
small plant, producinq leaves no wider
nica is usually found from than f mm (0:88 inchj and usually no
," j-1 to c2.4 m (8.0 ft)
longer than 10-15 cm (4-6 incks).
(Harrison 197g), while eelgrass occurs
Rhizomes are no more than 2-3 cm (6.8-1.2
from +1.8 rn (6.0 ft) down to -6.6 m (-22.0 inches) deep in the sediment. Leaf tips
ft) deep (Phillips 1972, 1974). In Canada
may be slightly notched, while those in
the two species overlap in the +1.0 m (3.3 eelgrass are rounded. Leaf sheaths are
ft) to +1.5 m (5 ft) region (Harrison open, while those in eelgrass are closed.
1979) .
In eelgrass, plants and leaves are much
A standard key to separate species is
unnecessary since only two species are
j
i
I
larger (a full analysis of seasonal
cha"9es in dimensions is given in chapter
2, Section 2.1, Vegetative Growth
strategies) .
The Pacific Northwest contains at least
three very large stands of eelgrass: (1)
Padilla Bay in northern Washington; (2)
Willapa Bay and Grays Harbor in
southwestern Washington; and ( 3 ) Hurnboldt
Bay in northern California. There are
large stands in some parts of southern
British Columbia and on Vancouver Island,
Canada (~arrison 1979, Haegele and Hamey
1982). Phillips (1972, 1974) calculated
that eelgrass covered up to 98 of the
bottom area of Puget Sound below mean
lower low water (MLLW). The largest stand
of eelgrass in Oregon is at Netarts Bay
(~igure 3). Table 2 lists the various
locations in the region where eelgrass has
been found and the extent of areal
coverage of growth where documented.
Eelgrass is found throughout the Pacific
Northwest in sheltered water on an
unconsolidated substrate and where
currents do not exceed 3.5 knots. Depth
of growth does not exceed -6.6 m (-22 ft),
and salinity is not less than 20 ppt
(except near river mouths at low tide).
Zostera japonica was probably introduced
into the region from Japan through the
oyster industry (~arrison 1976). Japanese
oysters were introduced into Willapa Bay
in 1928, and the species was first
collected by Hotchkiss in 1957 (Harrison
and Bigley 1982). These oysters were
increasingly imported after 1928 (Harrison
Figure 5. Eelgrass--(a) Vegetative plant and Biyley 1982). The species is
(b) Part of spadix with mature seeds presently found from Coos Bay (Phillips,
(after Phillips 1980) (~llustration unpublished research), to Netarts Bay,
courtesy of the U.S. Army Coastal Oregon; in Willapa Bay and Grays Harbor,
Engineering Research Center, Fort Belvoir, Waskington; and extensively from Padilla
~irginia) . Bay, Washington; to Nanaimo on Vancouver