Cover • Principle Findings • Introduction • Methods & Results • Data Summry •
Discussion/Conclusion • Glossary • Literature Cited
Figures & Tables • 1989/1999 Kelp Bed Maps
Introduction
Along the California
coast there is an abundant "kelp" resource
assemblage present (brown seaweeds - Order
Laminariales). The dominant, near shore, surface
canopy forming species include Nereocystis
luetkeana (bull kelp) and Macrocystis pyrifera
(giant kelp). Although the individual species
ranges are distinct, surface kelp canopies are
present along the entire California coast from
Crescent City to Imperial Beach (Abbot and
Hollenberg 1976). Each surface canopy, supported by air-filled
pneumatocysts, is composed of individual plants
that are attached to the bottom subtidal habitat by
root-like "holdfasts." The vertical stipes,
stretching from the sea floor to the surface
canopy, provide critical habitat for numerous
species of commercial and sport fish,
invertebrates, marine mammals and related
understory marine algae (Foster and Schiel 1985).
Along the central California coast, 77 species of
fish have been identified in kelp forests (Miller
and Geibel 1973), and McLean (1962) identified 204
species of invertebrates in a predominately
Nereocystis luetkeana kelp forest located south of
Monterey. Prominent marine mammals, such as seals,
sea lions and California sea otters. are also
associated with this important near-shore habitat
(Morejohn 1977). In addition to its role as an essential marine
habitat, coastal kelp canopies exhibit some of the
highest primary productivities of any ecosystem on
earth (Wheeler and Druehl 1986). This material is
provided to the food chain in three ways: 1)
directly, while the kelp plants are still attached,
2) indirectly, by providing detritus that is eaten
after it has fallen to the bottom, and 3) by
producing dissolved organic matter (DOM) that is
food for many microorganisms (Mumford 1989). Kelp
bed primary productivity within
Nereocystis/Macrocystis beds has been estimated at
350-2,800 g carbon/m2 (Wheeler 1990), placing them
ahead of tropical rain forests, reefs and
estuaries, warm temperate forests, and cultivated
land with regard to their contribution to the
overall food chain. Nereocystis luetkeana occurs from Point
Conception to the eastern Aleutian Islands (Druehl
1970), and is the dominant, surface canopy kelp
north of Santa Cruz, California. Its hydrodynamic
shape makes it especially well suited to high
exposure, "open coast" environments (Foster and
Schiel 1985). Nereocystis is predominately an
annual (Abbot and Hollenberg 1976), although mature
plants have been seen to persist for up to 18
months. Impressive growth rates of up to 10 cm per
day have been observed in young plants, and the
mature surface canopy reaches its maximum extent in
July through October. Sporangial sori mature at the
surface between May and December, drop from the
blade, and sink to the sea floor before releasing
their spores (Abbot and Hollenberg 1976). Macrocystis pyrifera has a range in North
America from Alaska to Magdalena Bay in Baja
California (Abbot and Hollenberg 1976), and
frequently forms thick canopies on rocky substrata
at depths of from 6-20 meters. Macrocystis is a
perennial1 at least the basal holdfast and attached
sporangial thalli, and develops its maximum surface
canopy between May and October. M. pyrifera is the
predominant canopy forming kelp in species in
California south of Sandhill Bluff ~Santa Cruz
County), and in addition to providing essential
marine habitat to hundreds of related species, is
utilized commercially as well. Upwards of 140,000
tons wet weight of M. pyrifera are harvested
annually from state-owned kelp beds for the purpose
of extracting alginates and colloids widely used in
industry and in the preparation and preservation of
certain foods (Abbot and Hollenberg 1976). Mixed canopies, containing both Nereocystis and
Macrocystis, are present along much of the
California coast-line from Sandhill Bluff (Santa
Cruz County) to Port San Luis (San Luis Obispo
County), and when these species co-occur,
Nereocystis is most commonly found inshore and
Macrocystis offshore (Foster and Schiel 1985). The extent of the total kelp canopy occupied by
each of these individual species is dynamic from
year to year. Annual fluctuations in canopy species
composition are thought to be the result of a
complex combination of physical, chemical, and
biologicai factors (Foster and Schiel 1985). Water
motion (Rosenthal et al. 1974), water
temperature/nutrients (Craig Barilotti pers.
comm.), light intensity (Luning 1981), and
available habitat, and exposure ~Foster and Schiel
1985) have all been associated with kelp canopy
health and development. In addition, warm water
temperature anomaiies, especially those associated
with the "El Nino Southern Oscillation" (ENSO),
have been known to dramatically reduce the
abundance, diversity and stability of the
near-shore kelp forest community (Tegner and Dayton
1991). In the latter months of 1997 and early
199&, the west coast of North America was again
influenced by a significant ENSO countercurrent. It
lasted several months, and raised surface sea
temperatures by as much as eight degrees Fahrenheit
in southern California and five degrees off the
Washington coast (NOM 1998). Aerial imagery
obtained in the summer of 1998 revealed that the
substantiai southern California near shore
Macrocystis pyrifera kelp canopy resource had been
largely eliminated south of Newport Beach,
presumabiy by these elevated temperatures or by
resultant invertebrate overgrazing. Little is known
regarding the effects of the ENSO, or other sea
temperature anomalies, on the Nereocystis kelD
resource. The relationships of these individual physical
factors, and identification of those that may be
"limiting" at any one time, have yet to be fully
understood, and continue to be the subject of
numerous ongoing research investigations. In
addition, adjacent kelp forests that appear to be
exposed to similar physical factors may frequently
produce vastly different canopy species
compositions, further revealing the complexity of
this dynamic habitat. Biological factors, including the impact of
herbivorous grazers such as sea urchins, are also a
major element determining the extent and diversity
of the near shore kelp resource (Foster and Schiel
1985). In that regard, the effects of a resident
sea otter population on the central California kelp
resource, and a better understanding of the role of
the otter in structuring near shore ecology are the
subject of ongoing research interest. Their predation on invertebrate kelp
grazers, mainly sea urchins (Jameson 1986), has
been shown to dramatically reduce the density of
these species, and to increase kelp canopy extent
in areas of significant otter abundance (Kivitek
1989). This increase in the kelp resource has been
observed to have dramatic effects on the diversity
and abundance of associated species, and the
resulting near shore community structure (Estes and
Palmisano 1974). This otter/urchin/kelp
interrelationship has resulted in the sea otters
designation as a "keystone predatoP. Kvitek (1998)
supported this designation by showing that sea
otter predation along the Washington outer coast
has significantly reduced the numbers of sea
urchins and the grazing pressure that they exert.
It was concluded that in the presence of an
established otter population, sea urchin grazing
was not the dominant force structuring the
near-shore community. Continued research will be
necessary to determine the impact of this important
marine mammal on the nearshore kelp forest
community. In addition to the natural effects of physical,
chemical, and biological factors on the near-shore
environment, occasional "man-caused" pollution
events may have significant additional effects on
species abundance and diversity (Foster and Schiel
1985). In 1991, the coilision of two ships,
approximateiy 22 miles WNW of Cape Flattery,
Washington (Rogne et a/ 1993), resulted in the
release of an estimated 1 G0,OG0 gallons of #2
diesel fuel into the marine environment. In
addition, oil continued to be released at a rate of
500 gallons/per day during the subsequent weeks.
The prevailing WNW winds and seas carried the fuel
oil towards both Vancouver Island and the Cape
Flattery area. During its time at sea the oil was
weathered, and would eventually be observed as "tar
balls" in both the keip beds, and to a lesser
extent on rocks and beaches from Neah Bay to Cape
Aiava. Ongoing ciean-up operations continued for
several months after the spill in an attempt to
minimize damage to the marine environment.
Questions were raised from this event regarding the
long-term effects of petroleum poilution on these
keip canopy forming species, and the resultant
vulnerability of the related marine community. Macrocystis canopies have been observed to be
largeiy unaffected by hydrocarbon pollution,
presumably due to the temporary protection provided
by plant produced mucus (Mitchell et al. 1970), and
the physical location of the reproductive
sporophylls near the basal holdfast. Pollution
effects on Nereocystis canopies have only been
recently investigated (Antrim et a/. 1995). Surface
stipe tissue bleaching and loss, as a result of
hydrocarbon contact, was observed both by Antrim
(1995), and during the fieid clean-up operation
following the 1991 Washington oil spill. However,
it is still unclear whether or not subsequent
seasonal Nereocystis recruitment is affected by
these polluting elements. The dynamic and sometimes vulnerable nature of
the coastal kelp resource, considering its
importance as habitat and food for hundreds of
related species, points out the need for systematic
methods of accurately assessing its extent and
vitality. Until 1989, the California state-wide
coastal kelp resource had only been sporadically
mapped and analyzed since an initial state-wide
visual survey conducted in 1915 (Rigg 1915).
Earlier ground based estimates of kelp canopy
extent have given way to modern aerial surveys,
which provide a cost effective and accurate
methodology for the mapping and quantification of
near shore kelp resources (Jamison 1971). A substantial portion of this dynamic kelp
resource habitat falls within the Monterey Bay
National Marine Sanctuary (MBNMS), established in
1992 as the largest United States marine sanctuary.
The management area includes 276 miles of the
California coastal zone betvveen Rocky Point (7
miles north of the Golden Gate Bridge) and Cambria
Rock (San Luis Obispo County), and extends from the
beach to approximately 30 miles offshore. Within
this management zone, occupying 5,322 square miles,
26 species of marine mammals, 94 species of
seabirds, 345 species of fish, 31 phyla of
invertebrates and over 450 species of marine algae
have been observed. The MBNMS administration has
four major components and mandates: 1 ) enhance
resource protection, through comprehensive and
coordinated conservation and management tailored to
the specific resources, 2) support, promote and
coordinate scientific research on, and monitoring
of, the site-specific marine resources to improve
management decision-making in National Marine
Sanctuaries, 3) enhance public awareness,
understanding, and wise use of the marine
environment through public interpretive and
recreational programs, and 4) facilitate, to the
extent compatible with the primary objective of
resource protection, multiple uses of these marine
areas not prohibited pursuant to other
authorities. In response to this conservation and management
mandate, Ecoscan Resource Data was contracted in
this study to establish a kelp resource inventory
program within the sanctuary-wide coastal zone
between Rocky Pt. and Pt Estero. A state-wide kelp
resource inventory, utiiizing similar methodology,
was conducted in 1989 (Van Wagenen 1989) for the
~alifornia Department of Fish and Game (CDF&G),
Marine Resources Division, and was available for
comparative purposes. The primary objective of this inventory, was the
establishment of a coastai keip resource mapping
and monitoring program that would accurately
refiect the current sanctuary-wide seasonai maximum
kelp resource extent. The methodology utilized was
designed to not only aliow a systematic, accurate
analysis of multi-year data from current and future
inventories, but to also aliow meaningful
comparisons with historic surveys as well. Data acquisition was accomplished utilizing
cost-effective medium format (70 mm) vertical
aerial infrared photography. Data processing
included the mapping of the imaged kelp canopies
onto a consistent baseline map series, followed by
a computer measurement of kelp canopy extent. Data
analysis for short term trends in kelp canopy
extent was accomplished by statistically comparing
indices from the current inventory with those of
the previous systematic study conducted in 1989.
Mapping products from both surveys, at several
scales, were included to graphically depict the
spatial extent of this important resource.
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2000