THE EFFECTS OF HARVESTING PYRIFERA ON UNDERSTORY IN CARHEL BAY,

by Robert Scott Kimura

A thesis submitted in partial fulfillment of the requirements for the degree of Haster of Arts in the Department of California State University, Fresno December 1980 ACKNOWLEDGMENTS

I offer my deepest gratitude to the late Dr. Torn Thompson; without his stimulus and encouragement I might never have become interested in marine plants. Thanks also are in order to my horne campus committee members Drs. Keith Woodwick and Gina Arce for their assistance and comments on my thesis; and to my off-campus committee member Dr. Mike Foster (California State University, Hayward) at Moss Landing Marine Laboratories for his technical guidance. I also extend my appreciation to Doug Hunt, my dive partner, Dan Miller, Kim McCleneghan, and Jim Houk of the California State Department of Fish and Game, Monterey, and fellow divers of Moss Landing Marine Laboratories. Without their assistance, this field work would have been a difficult undertaking. This research was funded by the University of California Sea Grant College Project R/CZ-21, under the direction of the late Dr. Torn W. Thompson. ABSTRACT

In Carmel Bay, the surface canopy undergoes a natural annual cycle of summer luxuriance and winter storm-related removal. Commercial harvesting activities normally occur during the summer months when surface canopies are best developed. To determine the effects of canopy removal on M. pyrifera and understory vegetation the abundances of 29 algal were followed for a 1-year period in three study areas. One study area was harvested in June and a second area in October to deter­ mine if canopy removal during different harvestable months would produce different results. A third area was an unhar­ vested control. All study areas were established adjacent to one another at depths ranging from 15 to 18 meters in locations known to have not been previously harvested.

In January, 6 months following the June canopy harvest, the abundances of juvenile Macrocystis pyrifera and increased signifi­ cantly in the June harvested area. No new juveniles were noted during this time in the unharvested area. Recruitment in the latter area did not occur until 5 months later. Most of the winter-appearing juveniles in the June harvested area were quickly lost due to early storm-related mortalities.

Therefore, the enhanced recruitment of the M. pyrifera and vi

~· californica populations did not contribute more adults to

the June area relative to the unharvested area which lacked winter recruitment. Harvesting in October had a smaller

effect on recruitment. In the October harvested area, M.

pyrifera and ~· californica juvenile abundances· also

increased substantially 6 months following canopy removal,

but this occurred 1 month prior to natural recruitment in

the unharvested area. This closer coincidence of recruit­ ment probably occurred because the October harvest was

closer to the time of natural canopy thinning in the uncut

area. The different recruitment periods are assumed to be

the result of increased submarine illumination caused by

surface canopy removals. Seasonal trends for all other

species in the harvested areas were similar to those in the

uncut area. In addition, annual harvesting operations have not disrupted the natural seasonal oscillations in total

surface canopy coverage for the entire bed from 1973

to 1979. CONTENTS

Page LIST OF TABLES . viii

LIST OF FIGURES X

INTRODUCTION l

LOCATION AND METHODS 5 Study Site 5 Methods 8

RESULTS 18 Substrate Composition 18 Species Composition 18

Algal Layering Structure 2l

Trends in Algal Percent Cover 21 Trends in Algal Density 34

The Effects of a June Harvest 72

The Effects of an October Harvest 77 DISCUSSION . . . 81 The Effects of Harvesting on Understory Algae 81 The Effects of Harvesting on Adult Macrocystis pyrifera ...... 91 General Community Overview 94 CONCLUSIONS 102 LITERATURE CITED 104 LIST OF TABLES

Table Page 1. Sampling Frequencies and Sample Sizes (N) for the 10m2 Quadrat and Random-Point- Contact Methods . . . . 15 2. Species Encountered in the Unharvested, June and October Harvested Areas Over the Course of the Study Period . 20 3. Percent Cover of Minor Species in the Unharvested Area Over Time . . . . . 26 4. Percent Cover of Minor Species in the June Harvested Area Over Time 27 5. Percent Cover of Minor Species in the October Harvested Area Over Time . . 28 6. Percent Frequency of Occurrence Values for l-!acrocys tis hyrifera Adults and Juveniles in Eac of the Unharvested, June, and October Harvested Areas Over Time ...... 35 7. Percent Frequency of Occurrence Values for Pterygophora californica Adults and Juveniles in Each of the Unharvested, June, and October Harvested Areas Over Time ...... 36 8. Percent Frequency of Occurrence Values for Juvenile Laminariales in Each of the Unharvested, June, and October Harvested Areas Over Time 37 9. Percent Frequency of Occurrence Values for Cystoseira osmundacea Adults and Juveniles in Each of the Unharvested, June, and October Harvested Areas Over Time .. 38 10. Percent Frequency of Occurrence Values for Schizymenia pacifica in Each of the Unharvested, June, and October Harvested Areas Over Time 39 ix Table Page 11. Percent Frequency of Occurrence Values for Weeksia reticulata in Each of the Unharvested, June, and October Harvested Areas Over Time 40 12. Percent Frequency of Occurrence Values for Opuntiella californica in Each of the Unharvested, June, and October Harvested Areas Over Time ...... 41 13. Two-Tailed Kruskal-Wallis Test of Macrochstis hyrifera Juvenile Abundances in Eac of t e Unharvested, June and October Harvested Areas . . . . 73 14. Newrnan-Kuels Multiple Comparisons Test of Macrosystis pyrifera Juvenile Abundances in the June Harvested Area .. 73 15. Newrnan-Kuels Multiple Comparisons Test of Macrocystis pyrifera Juvenile Abundances in the Unharvested Area .... 74 16. Two-Tailed Kruskal-Wallis Test of Pterygophora californica Juvenile Abundances in Each of the Unharvested, June and October Harvested Areas . 76 17. Newrnan-Kuels Multiple Comparisons Test of Pter~gophora californica Juvenile Abun ances in the Unharvested Area . 76 18. Two-Tailed Kruskal-Wallis Test of Juvenile Laminariales Abundances in Each of the Unharvested and June Harvested Areas 78 19. Newrnan-Kuels Hultiple Comparisons Test of Juvenile Laminariales Abundances in the Unharvested Area . . ... 78 20. Newrnan-Kuels Multiple Comparisons Test of Macrocystis pyrifera Juvenile Abundances in the October Harvested Area 80 LIST OF FIGURES

Figure Page 1. Carmel Bay Kelp Bed and Study Area Locations 36°33'N. & 121°57'W 6 2. Vertical Layering in the Carmel Bay (Most Abundant Species within Each of Seven Layers) 7 3. Mean No. Plants/10m2 = 95% Confidence Intervals Versus Increasing Sample Size 13 4. Overall (Annual) Percent Composition of Substratum Types for Each of the Study Areas 19 5. Mean No. Layers/Point and Sample Sizes for Each of the Study Areas 22 6. Pre-Harvest (Summer) Percent Cover Values Per Species for Each of the Study Areas 24 7. Plocamium cartilagineum Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 29 8. Calliarthron tuberculosum Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 30 9. Bossiella californica ssp. schmittii Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 32

10. Crustose Corallines Percent Cover ~95% Confidence Intervals and Sample Sizes in Each of the Study Areas 33 11. Mean No. of Macrocystis pyrifera (adults)/ 10m2 ±95% Confidence Intervals in Each of the Study Areas 42 12. Mean No. Macrocystis pyrifera (juveniles)/ 10m2 ~95% Confidence Intervals in Each of the Study Areas 44 xi

Figure Page 13. Relative Changes in Macrocystis pyrifera Canopy Cover for the Carmel Bay Kelp Bed from 1973 to 1979 46 14. Macrocystis pyrifera Mean Canopy Frond Lengths in Each of the Study Areas . 47 15. Macrocystis pyrifera Mean No. Stipes/10m2 in Each of the Study Areas . . . . . 49

16. Mean No. Pterygophora californica (adults)/ 10m2 ~95% Confidence Intervals in Each of the Study Areas . . . . 51

17. Pterygophora californica (adults) Relative Percent Composition of Four Morphological Categories in the Unharvested Area .. 52

18. Pterygophora californica (adults) Relative Percent Composition of Four Morphological Categories in the June Harvested Area 53 19. Pterygophora californica (adults) Relative Percent Composition of Four Morphological Categories in the October Harvested Area . 54

20. Mean No. Pterygophora californica (juveniles)/ 10m2 ~95% Confidence Interval in Each of the Study Areas . . . . 57

21. Mean No. Laminariales (juveniles)/10m2 ~95% Confidence Intervals in Each of the Study Areas 59

22. Mean No. C~stoseira osmundacea (adults)/ 10m2 ~95" Confidence Intervals in Each of the Study Areas . . 61

23. Cystoseira osmundacea (adults) Relative Percent Composltlon of Three Morphological Categories in the Unharvested Area . 63

24. Cystoseira osmundacea (adults) Relative Percent Composltlon of Three Morphological Categories in the June Harvested Area 64

25. Cystoseira osmundacea (adults) Relative Percent Composltlon of Three Morphological Categories in the October Havested Area 65 xii Figure Page 26. Mean No. Cystoseira osmundacea (juveniles)/ 10m2 ±95% Confidence Intervals in Each of the Study Areas ...... 67 27. Mean No. Schizymenia pacifica/10m2 ±95% Confidence Intervals in Each of the Study Areas ...... 68 2 28. Mean No. Weeksia reticulata/10m ±95% Confidence Intervals in Each of the Study Areas ...... 70 29. Mean No. Opuntiella californica/10m2 ±95% Confidence Intervals in Each of the Study

Areas 0 • • • • • • • • 0 • • • • • • • • 71 INTRODUCTION

Algal community structure in kelp forests has been described by Neushul (197la) and Foster (1972). The campo- nents, based on plant size, are vertically layered and thus act as shading agents reducing the amount of light reaching the bottom. Shading effects produced by Macrocistis pyrifera surface canopies are well known to suppress under­ story algal species composition and abundance. Dawson et al. (1960) noted only six species within a dense M. pyrifera kelp bed, while 28 species were collected in an open bed. MacFarland and Prescott .(1959) found the wet weight biomass of understory algae beneath a sparse surface canopy to be 2 0.475 kg/m . Under a dense canopy fewer species were found 2 and with less abundance (0.004 kg/m ). Pearse and Hines

(1979) removed entire ~- pyrifera plants in a Santa Cruz, central California kelp bed. In 3 months significantly

greater abundances of juvenile ~- pyrifera, Pterygophora californica, dentigera, and foliose red algae were found in the cleared versus adjacent uncleared area. Neushul (197lb) attributed the lack of undergrowth in several kelp beds to be the result of insufficient light. North (1971) states that overstory canopies, by producing a shading effect, can regulate understory community struc­ ture by excluding "light-loving" species and/or permitting 2 "dark-loving" species to inhabit shallower water.

Macrocystis pyrifera presently serves as a major

resource for algin, a commercial name given to a variety of soluble salts of alginic acid contained in cell walls I (Chapman, 1950). Alginic acids, with their wide range of

fiscosities, have a multitude of commercial uses. Cur-

rently, ~- pyrifera is harvested for algin extraction by

mowing barges. The legal depth of cutting is 4 feet, which

is sufficient to remove the surface canopy. To date there

have been few studies on what effects commercial removal of

the Macrocystis pyrifera surface canopy has on associated lI F understory algae. Pearse and Hines's removal of entire giant

kelp plants did not simulate commercial cutting, which

removes only surface tissue. However, their experiments

clearly indicate that ~- pyrifera functions as a dominant

shade producer limiting understory algal development. Under natural conditions North (1959a, 1967, 1971), Gerard (1976),

and Lobban (1978a) noted that the development of juvenile

~- pyrifera plants is inhibited by self-shading and enhanced when surface canopies are removed by factors such as storms.

Rosenthal et al. (1974) studied a kelp bed situated off

Del Mar, southern California and noted the absence of

juvenile ~- pyrifera plants until 6 months following canopy

removal by a kelp harvester. However, they did not clearly

conclude that harvesting prompted the appearance of juveniles

since the surface canopy underwent natural thinning at the 3 same time. North (1957, 1958, 1959b) studied the Paradise

Cove kelp bed in southern California and found no differ­ ences in understory algal abundances in an area 1 year after being commercially harvested compared to a nearby uncut area. However, in another area which had been con­ tinuously cut for 2 years by boat traffic associated with a nearby pier, there were appreciably greater numbers of juvenile~- pyrifera plants as well as other seaweeds.

Adult M. pyrifera plants were also present in the boating channel but were smaller (fewer stipes). Miller and Geibel

(1973) studied the effects of maximum kelp harvesting in a

Monterey Bay kelp bed, central California. They found

cutting the same plants three times in 1 year eliminated adult M. pyrifera but enhanced the number of juvenile ~­ pyrifera and Gigartina spp. compared to an adjacent uncut area. Both the findings in the Paradise Cove boating

channel kept open for 2 years and the Monterey Bay kelp bed area cut three times in 1 year probably reflect the effects of overharvesting.

Nany kelp beds in southern California display

surface canopies which persist for many years. Rosenthal et al. (1974) observed canopies near Del Mar to persist up to 4 to 8 years before removal by severe storm activity.

North (1971) reports that kelp beds near Point Conception have been known to oscillate on a 17-year cycle. These kelp beds are potentially harvestable throughout the seasons. 4 While harvesting operations are more concentrated

in southern California, Carmel Bay, central California

represents the northernmost area of commercial interest.

The Carmel Bay ~- pyrifera surface canopy oscillates on an

annual cycle in which spring/summer canopy luxuriance

alternates with fall/winter storm associated thinning

(personal observation). Harvesting usually occurs during

the summer months when canopy yields are greatest and seas

are calm. Natural differences in canopy abundance between

southern and central California suggest that the effects of harvesting may also differ. The purpose of this study was

to determine if June or October surface canopy removal in

Carmel Bay, central California would alter understory algal abundances relative to an unharvested control area. LOCATION AND METHODS

Study Site

The study was carried out in a Macrocystis pyrifera kelp bed situated off Carmel Beach (Figure 1). The sub­ stratum, primarily expanses of granite bench rock, was also composed of scattered boulder, cobble, and sand channel areas. The topography was variable with occasional rocky outcrops standing several meters off the bottom. The size and configuration of the kelp bed is determined by sand and water motion along the lateral and landward sides and insuf­ ficient light and/or the lack of hard substratum at roughly the 27-meter depth contour along the seaward edge.

Kelp harvesting operations in Carmel Bay normally do not occur at depths shallower than 18 meters due to several unmapped wash pinnacles situated closer to shore. At the

18-meter depth contour seven algal layers were present

(Figure 2). The bottom or first layer was comprised mainly of crustose corallines which covered nearly all hard sub­ strates. The holdfasts of all species were also considered in this layer. The second layer consisted of plants roughly

10 centimeters in height. Bossiella californica ssp. schmittii was the most common algae occupying this level and occurred as scattered individuals. Calliarthron tuber­ culosum was the major component of the third algal layer and 6 N

Arrowhead Point

October Harvested Area

Unharvested Area

1 km.

Figure 1. Carmel Bay Kelp Bed and Study Area Locations 36°33'N. & 121°57'W. MACROCYSTIS (CANOPY)

PTERYGOPHORA 6 1. O (CANOPY)

5 0.5 MACROCYSTIS ()

PLOCAMIUM & 4 0.4 CYSTOSEIRA 3 0.3 CALLIARTHRON 2 0.1 BOSSIELLA 1 0 CRUSTOSE

Figure 2. Vertical Layering in the Carmel Bay Kelp Forest (Most Abundant Species within Each of Seven Layers) 8 formed extensive mats over the bottom. Plocamium cartila- gineum was found mainly as an epiphyte on C. tuberculosum.

Scattered clumps and individuals of P. cartilagineum and

Cystoseira osmundacea comprised the fourth algal layer roughly 40 centimeters above the bottom. These algae were overtopped by the sporophylls of Hacrocystis pyrifera. A sixth subsurface layer standing roughly 1 meter off the bottom was formed solely by the blades of Pterygophora californica, but individuals were highly dispersed and blades did not form a continuous canopy over the bottom.

Overshading all species were the surface fronds of M. pyrifera which formed a continuous canopy over the kelp bed area during the summer.

Methods

Studies had to be conducted at depths where harvest- ing is practiced, and study sites had to be located in areas known to have never been previously harvested. Three circular 30-meter radius study sites were established roughly 0.5 kilometers directly off Carmel Beach at depths ranging from 15 to 18 meters (Figure 1). Each of the three circular areas was marked by a surface buoy anchored at the center. One area (reference/control area) was not harvested so natural seasonal changes could be monitored. Each of the two remaining areas was harvested once. One area was harvested in June 1975 (June area), and the other the 9 following October (October area). The Macrocystis pyrifera surface canopy in the June area was mechanically removed by

KELCO, a commercial harvesting firm based in southern

California. The October canopy was removed by hand. Surface fronds were bundled and cut by divers at a depth of 4 feet

(uncorrected for tidal height). The bundles were then tethered to a boat, towed out to sea, and released. Cammer- cial kelp cutters often do not remove all fronds in the cutting path, analogous to a lawn mower not cutting every blade of grass. In contrast, hand harvesting tends to be more efficient. In the present study, few uncut fronds were left in the commercially harvested area immediately after cutting, whereas in the hand-harvested area no uncut fronds remained. The difference in canopy abundance after cutting between the two areas was negligible since the number of uncut fronds in the June area was minimal.

Macroscopic benthic algae exhibit a variety of growth habits, and determining what is an individual is often difficult. This is especially true for understory species which tend to form mats due to rhizomatous and/or aggregated growth habits (e.g., Plocamium cartilagineurn and the articu­ lated coralline algae), and plants that grow as prostrate crusts (e.g., Lithothamnium spp. and Lithophyllum spp.). 2 Both lOrn permanent plots (quadrats) and random-point-contact techniques were employed to subsample plant abundance in each study area. The quadrat method was used to obtain direct 10 2 counts of definable individuals in the 10m areas. The random-point-contact technique provided percent cover estimates for all species "contacted" by random points.

2 lOrn Permanent Plot Method (density)

Within each of the three circular study areas, 2 25-lOm quadrats were randomly distributed and marked by either a subsurface buoy or yellow plastic bicycle handlebar tape anchored to rock by a concrete nail. The quadrats for each area were successively numbered from l to 25. During each sampling survey, all stations were relocated utilizing distance and compass headings. Each quadrat marker served as the center point to which a movable radius of 1.8 meters 2 length was attached and rotated to define a 10m circular area. A reference radius marked the beginning and end posi- tion of the arc swung by the movable radius.

Individuals counted in the fixed quadrats included the (Phaeophyta) Macrocystis pyrifera, Pterygo- phora californica, and Cystoseira osmundacea, and the red algae (Rhodophyta) Schizymenia pacifica, Weeksia reticulata, and Opuntiella californica. Brown algae standing roughly less than 0.25 meters in height consisting of a terminal blade supported by a short stipe were also counted but were generally not recognizable to species. Since all sporophytes of the order Laminariales appear this way during early development, these plants were treated as juvenile ll Laminariales until further tissue development permitted species identification.

Adults and juveniles were distinguished for each of the above brown algae. Macrocystis pyrifera whose longest front extended more than l meter off the bottom were treated as adults, while smaller plants were considered juveniles.

Pterygophora californica adults were defined as those being in at least their second year of growth as indicated by the presence of scars along the margins of the stipes.

Adult P. californica plants commonly had stipe lengths of roughly l meter. Shorter plants were generally in their first year of growth (lack of sporophyll scars) and were recorded as juveniles. P. californica adults were further partitioned into one of four blade condition categories:

(l) stipes bearing blades without evidence of tip deteriora­ tion and/or senescence (mature blades); (2) blades which were eroded and/or bryozoan encrusted (senescent blades);

(3) absence of blades (bare stipes); and (4) bare stipes initiating new blade production (new blade growth).

Cystoseira osmundacea juveniles appeared as small rosettes of less than 0.1 meter height. Adults consisted of all larger thalli and were further partitioned into one of three categories: (l) perennial basal branches only (basal);

(2) basal branches just beginning initiation of the floating vesicular branch bundles (intermediate); and (3) plants with vesicular branch bundles with one branch at least 0.25 meters long (erect). 12 In order to determine if 25 quadrats adequately subsampled the more conspicuous populations, cumulative mean density versus increasing sample number curves were gener­ ated for the Macrocystis pyrifera, Pterygophora californica, and Cystoseira osmundacea populations (Figure 3). Analyses were based on initial sampling data from the unharvested area. A guideline indication as to the minimum number of samples desired to estimate total population densities is determined by the sample number at which each curve reaches an asymptote. Figure 3 suggests that roughly 16, 23, and 9 samples were sufficient to estimate adequately the surround­ ing ~- pyrifera, ~- californica, and C. osmundacea population densities, respectively.

Although each study area originally contained 25 quadrat sites (N=25), some station markers were lost as time progressed, and several sites could not be relocated.

Therefore, for each area, density values for all sampling periods and statistical tests were calculated from only those quadrats which could be found throughout the length of the study. One exception was made for the June harvested area. Twenty sample plots persisted throughout most of the study period. In May, only five plots were sampled due to appreciable station loss. Although the May data were used in graphical analyses, they were omitted in statistical analyses due to equal sample size requirements. 13

5.0 Macrocystis pyrifera

15.0

Pterygophora californic a N s 10.0 0 ...-< ---.. ~ ,_,(I] ' 1'--. )::: 5.0 CIJ f-. ...-< - I'Y 1/ "" f- z0 / -' § .

5.0 . \ T T T 1"---. I/ - 1 I 1 12 34 56 7 8 91011121314151617181920212223 Number of Quadrats

2 Figure 3. Mean No. Plants/10m = 95% Confidence Intervals Versus Increasing Sample Size 14 Survey dates and the actual sample size (N) for the 2 10m permanent plot method are presented for each study area in Table 1.

Random-Point-Contact Method (percent cover)

Percent cover estimates obtained by the random-point- contact method were made for all remaining algal species and sessile invertebrates. The sampling instrument consisted of a 3-meter length of 0.5 centimeter diameter nylon line. Ten randomly spaced knots, functioning as points, were tied along the line that was weighted by several fishing weights.

The random-point-contact method was not intended to monitor fixed points. Successive lines formed a continuous random-point transect. For each study area during each sampling survey, random points ran in somewhat straight lines 2 2 from 10m station to 10m station. Observations were made by visualizing an imaginary line perpendicular to the sub- strate and passing through each point. All species inter- cepting the imaginary vertical line were recorded in the order which they were "hit," starting at the height of the

Pterygophora californica canopy (approximately 1 meter off the bottom) and continuing down to the substratum. Only one recording per species was made for each point (i.e., multiple blade overlap per species was not considered). However, exceptions were made for Macrocystis pyrifera and ~· cali­ fornica where sporophylls and holdfasts were treated as 2 Table 1. Sampling Frequencies and Sample Sizes (N) for the 10m Quadrat and Random-Point-Contact Nethods

10m2 Quadrat Hethod (N = No. of Quadrats)

Unharvested Area 23 -- 23 -- 23 23 -- 23 23 23 23 23

June Harvested Area 20 20 20 ------20 ------5

October Harvested Area -- -- 21 -- 21 -- -- 21 -- -- 21 --

Random-Point-Contact Hethod (N = No. of Points)

Unharvested Area 850 --- 600 --- 1200 ------890 --- 900 --- 1030

June Harvested Area --- 780 ------660 ------910 ------

October Harvested Area ------780 --- 680 ------1090 ------840

June July Aug.Sept.Oct. Nov. Dec. Jan. Feb. Har. Apr. Hay 1975 1976 16 separate taxonomic entities. Substratum type (bench rock,

boulder, cobble, or sand) and whether it was colonized or

bare was recorded as the last contact for all points. Since

surge occasionally caused the algae to flop back and forth

over the points, a haphazard instantaneous observation was

made for each point.

The total number of points sampled per study area and

survey ranged from 600 to 1200. Percent cover values per

taxonomic category were calculated by dividing the total

number of "contacts" per taxa by the total number of sampled

points and multiplying by 100. Ninety-five percent confi­

dence intervals for percentages were obtained from Table W

in Rohlf and Sakal (1969). Survey occurrences and the total

number of points sampled per survey (N) for each area are

presented in Table l.

Macrocystis pyrifera surface canopy abundance was·

concurrently measured by stipe lengths and the number of

stipes per plant. Thirteen to 18 plants were tagged in each

study area at the beginning of the study. The distance from

the surface to the tip of the longest frond per tagged plant was measured (uncorrected for tidal height), and the number of stipes l meter above the bottom counted. The same measure­ ments were made throughout the study period.

If surface canopies were left unmanipulated, seasonal trends in plant abundance were assumed to have been similar across study areas. With this assumption, seasonal trends 17 in the unharvested area served as a "standard" by which trends observed in the harvested areas could be compared for similarities or differences. Trends in the harvested areas which diverged considerably from those observed in the unharvested area were considered variations due to increased submarine illumination by canop"y removal. Trends in density which were different between study areas were tested for statistical significance. By area, monthly data were first tested by the nonparametric Kruskal-Wallis test for signifi­ cance (Sakal and Rohlf, 1969). If significant differences were found, the same data were tested by the posteriori

Newman-Kuels multiple comparisons test to determine which monthly abundances were significantly different (Zar, 1974).

In this manner, opposing or similar trends between areas could be statistically determined for different pre- to post­ harvest time intervals. For each area all monthly density data were utilized in statistical tests except the May data for the June harvested area, due to equal sample size require­ ments. Significance for all statistical tests was set at the

.05 level of probability.

All species identifications were derived from taxonomic keys in Abbott and Hollenberg (1976). RESULTS

Substrate Composition

The percent composition of substratum types (bench rock, boulder, cobble, and sand) were obtained by the random-point-contact method. Since little seasonal variation was observed for each of the substratum types in the study areas, overall mean percent cover values were used to summarize and compare the relative proportions of substratum types within the study areas (Figure 4). Substratum types were represented in relatively equal proportions across the study areas. Bench rock covered about 75 percent of the bottom in all study area. Boulders, cobble, and sand made up roughly 2, 6, and 17 percent of the bottom in all study areas, respectively.

Species Composition

Species composition was derived by combining all species encountered with the random-point-contact method and 2 those observed within the 10m permanent plots. A total of

29 species were encountered during the entire study period

(Table 2). All species encountered in both the June and

October areas were also represented in the unharvested area, but five species were found exclusively in the latter area. 19

100.0

~ 0 ...; .w ...; rn 0 [g' 0 50.0 u .w ~ QJ tJ 1-1 QJ p.,

Unharvested June October Area Harvested Areas

Sand Cobble Boulder Bench Rock

Figure 4. Overall (Annual) Percent Composition of Substratum Types for Each of the Study Areas 20 Table 2. Species Encountered in the Unharvested, June and October Harvested Areas Over the Course of the Study Period

CHLOROPHYTA Halicystis ovalis X X 2 PHAEOPHYTA Cystoseira osmundacea X X X 4 Desmarestia ligulata var. firma X X X 5 Desmarestia ligulata var. ligulata X X X 5 Dictyota binghamiae X X 3 Macrocystis pyrifera X X X 7,5 Pterygophora californica X X X 6

RHODOPHYTA Botryoglossum farlowianum X X 3 Bossiella californica ssp. schmittii X X X 2 Bossiella spp. X X X 3 Calliarthron tuberculosum X X X 3 Callophyllis flabellulata X X X 2 Coralline crust X X X 1 Fauchia laciniata X X 2 Fryeela gardneri X X X 2 Laurencia spectabilis X 3 Laurencia suboptosita X X X 4 Opuntiella cali ornlca X X X 3 Nienburgia andersonii X 3 Non coralline crust X X X 1 Pikea californica X 3 Plocamium cartilagineum X X X 4 Polyneura latissima X X X 3 Polysiphonia ~· X 2 Prionitis lanceolata X X 3 Rhodoptilum plumosum X X 2 Rhodymenia ~· X X X 2 Schizymenia pacifica X X X 3 Weeksia reticulata X X X 3 21 Algal Layering Structure

As mentioned earlier, six subsurface algal layers were described for the study areas. These layers were stratified such that all could potentially lie atop one another, but generally this was not the case. Although a maximum of five vertically stratified layers were encountered over several points, the average number of layers overtopping a point (Layering Index) was considerably less (Figure 5).

Data from points sampled in sand channels were omitted from calculations since these areas were usually devoid of vege- tation. Thus, Figure 5 depicts layering structure for hard substrata only. Layering Indicies show that for any season, layering was poorly developed but relatively similar across study areas. The mean number of layers per point during any given season for all areas varied between 0.9 and 1.6 algal layers. There was an overall slight decline in mean number of algal layers throughout the course of the study in all areas.

Trends in Algal Percent Cover

All sample points from the random-point-contact method were used to calculate algal percent cover values

(i.e., values reflect percent cover for total bottom area rather than for specific substratum types). Since the percent composition of substratum types was similar across study areas and did not change substantially with season, ue~----

11--- -II June Harvested Area

A .. -·· -,A October Harvested Area 2.0 780 611--- - 680 660 ._.. -- -11- _ ___J090 910 840 850 780 • - .. -·t-··-·· -··-··=-A== .. -=..;:·=.11 .. ____ .. -A 1.0 Gl 600 1200 8~ • 900 1030 z0

June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May

1975 1976

Figure 5. Mean No. Layers/Point and Sample Sizes for Each of the Study Areas

N N 23 utilizing all sample point data (all substratum types combined) does not bias interpretation of algal spatial and temporal trends.

In order to compare algal coverage across the study areas and to define the more important species based on percent cover, preharvest percent cover data for all species were utilized and are illustrated by area in Figure 6. With the exception of Plocamium cartilagineum and the crustose coralline algae, cover for all species differed by no more than 5 percent across all study areas. ~- cartilagineum was considerably more common in the June harvest area. As mentioned earlier, ~- cartilagineum was observed mainly as an epiphyte on Calliarthron tuberculosum. The slightly greater abundance of C. tuberculosum in the June harvest area compared to the other areas may be partly responsible for the differences in~- cartilagineum abundance. Also, nearly all f. tuberculosum plants in the June area were colonized by P. cartilagineum, while many plants were free of epiphytes in the other two areas.

From these data it is apparent that, based on cover in excess of 10%, the major understory algae were Plocamium

cartilagineum, Calliarthron tuberculosum, Bossiella californica ssp. schmittii, and crustose corallines. All other species never exceeded 5.0 percent cover, or more

commonly 1.0 percent cover throughout the study period and were therefore considered minor components within the study 24

l-1 Q) :>,

Macrocyst is (Sporophylls)

Cystoseira

Plocamium 4

Calliarthron 3 =r Bossiella 2='

Crustose 1 Corralines

Other Algal Species 1-3 ~

Attached Invertebrates 1-2 ::r'

Total 1-6

0 20 40 60 Percent Cover

Figure 6. Pre-Harvest (Summer) Percent Cover Values Per Species for Each of the Study Areas 25 areas, Furthermore, since abundances remained low, no differences in seasonal trends between study areas for these minor species could be detected. Seasonal percent cover values for the minor algal species as well as attached invertebrates are presented for the unharvested, June and

October areas in Tables 3, 4, and 5, respectively.

The following are descriptions of seasonal trends in percent cover by area for the major species Plocamium carti1agineum, Calliarthron tuberculosum, Bossiella cali­ fornica ssp. schmittii, and crustose coralline algae.

Plocamium cartilagineum

Percent cover for Plocamium cartilagineum in all study areas was generally greater in spring and summer and lower in fall and winter (Figure 7). Throughout the study period, this species was more abundant in the June area.

Seasonal abundance values in the June cut area ranged between 27.6 and 45.3 percent cover. In the October and unharvested areas, abundances varied from 9.7 to 21.9% and f~om 3.5 to 15.3%, respectively.

Calliarthron tuberculosum

Seasonal variations in percent cover for Calliarthron tuberculosum are illustrated by area in Figure 8. Abundances in all areas declined slightly from the initial to final surveys. As with Plocamium cartilaginum, Calliarthron tuberculosum was more abundant in the June area with cover Table 3. Percent Cover of Minor Species in the Unharvested Area Over Time

------1975------1976----

June July Aug. Sept Oct. Nov. Dec. Jan. Feb. Mar. April M3.y

(N) 850 -- 600 -- 1200 -- 890 900 -- 1030

Callophyllis flabellulata 0.1 Cystoseira osmundacea 2.0 0.3 1.0 0. 7 0.8 0.6 Desmarestia ligulara var. firma 1.0 0.1 Dictyota binghamiae 0.2 Fryeella gardneri 0.1 juvenile red blade (unidentifiable) 0.3 0.3 Laminariales juvenile 0.1 Laurencia subopposita 2.4 0.1 Macrocystis pyrifera (holdfast) 0.9 1.3 1.0 0.2 0.8 1.0 Macrocys tis pyrifera (sporophylls) 2. 0 2.0 1.5 2.0 2.8 non-coralline crust 0.9 0.6 0.2 0.4 1.7 Opuntiella californica 0.7 0.3 0.2 0.1 0.4 0.3 Polyneura latissima 0.1 Prionitis lanceolata 0.1 Pterygophora californica (holdfasts) 0.1 0.2 0.1 0.2 Pterygophora californica (blades) 5.0 1.0 1.0 0.2 Rhodymenia ~· 0.1 Schizymenia pacifica 1.8 0.1 attached invertebrates 17.5 16.3 15.1 12.2 10.7 8.3 Table 4. Percent Cover of Minor Species in the June Harvested Area Over Time

·~. 1975 1976 Jme July Aug. Sept Oct. Nov. Dec. Jan. Feb. Mar. April May (N) I 7801 --I 1660 1 1910 1 I -- l Botryoglossum farlowianum 0.1 Callophyllis flabellulata 0.3 0.3 Cystoseira osmundacea 2.4 1.8 4.1 Desmarestia ligulata var. firma 0.3 0.3 1.3 Desmarestia ligulata var. ligulata 0.1 Lauren cia subopposita 2.7 Macrocystis EYrifera (juvenile) 0.6 0.7 Macrocystis pyrifera (holdfast) 0.4 0.6 0.7 Macrocystis £yrifera (sporophylls) 1.0 0.4 non-coralline crust 0.6 1.1 Opuntiella californica 0.1 Pterygopflora californica (juvenile) 0.2 Pterygophora californica (blades) 3.3 0.3 2.3 Pterygophora californica (holdfast) 0.1 Schizymenia pacifica 0.1 0.2 attached invertebrates 8.5 7.6 3.4 Table 5. Percent Cover of Minor Species in the October Harvested Area Over Time

----- 1975 ------1976 -----

Jrne July Aug. Sept Oct. Nov. Dec. Jan. Feb. Mar. April May (N) I -- I I 780! I 6801 -- I I -- I

Callophyllis flabellulata 0.1 Cystoseira osrnundacea 2.6 1.5 3.7 1.5 Dictyota bin~harniae 2.8 Fryeella gar neri 0.1 Laurencia subopposita 1.8 Macrocystis pyrifera (juvenile) 0.1 1.0 Macrocystis pyrifera (holdfast) 1.7 1.1 0.1 0.4 Macrocystis pyrifera (sporophylls) 1.0 1.8 0.8 0.8 non-coralline crust 1.0 1.5 1.3 1.2 Opuntiella californica 0.1 3.7 0.2 Pterygophora californica (blades) 1.3 0.9 0.6 1.9 Rhodymenia ~- 0.1 Schizyrnenia pacifica 0.1 attached invertebrates 9.9 10.9 8.3 9.6

N 00 29

30.0 Unharvested Area 600 20.0 1030 10.0 1200 890

50.0 780

~ 40.0 (jJ 910 :> 0 u 30.0

~ '"'(jJ () 20.0 ~ (jJ 1'1< 10.0 June Harvested Area

30.0 840 1091-:o_____ -:1 20.0 780 680 10.0 October Harvested Area

June July Aug.Sept.Oct. Nov. Doc. Jan. Feb. !-'JEtr. Apr. May -----1975 ---- 1976 ---

Figure 7. Plocamium cartilagineum Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 30

30.0 600 850 1200 890 20.0 1030 10.0 Unharvested Area

40.0 660 H 780 Q) 30.0 :> 0 u 20.0 .w >:: Q) C) 10.0 H Q) June Harvested Area P4

40.0 680 30.0 78o 1 I._----fr-~90 840 20.0 1I----!I 10.0 October Harvested Area

June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. l".ar. Apr. May ------1975 ------1976---

Figure 8. Calliarthron tuberculosum Percent Cover 795% Confidence Intervals and Sample Sizes in Each of the Study Areas

I 31 varying between 13.3 and 27.9%. In the unharvested and

October areas, abundances ranged from 12.7 to 20.0% and from

17.3 to 24.1%, respectively.

Bossiella californica ssp. schmittii

The percent coverage abundances of Bossiella

californica ssp. schmittii was similar across study areas

(Figure 9). Abundances within each study area remained relatively stable with time. Cover values in all areas ranged between 7.0 and 12.0%.

Coralline Crusts

Due to field identification difficulties, Litho- phyllum spp. and Lithothamnium spp. were grouped under the taxonomic category "coralline crusts." Percent cover of coralline crusts was relatively similar in all study areas

(Figure 10). Both the minimum (31.1 percent cover) and the maximum (55.2 percent cover) abundances for all study areas occurred in the unharvested area.

Although seasonal variations in cover were recorded for each area, fluctuations were interpreted as not substan- tial due to difficulties of sampling the bottommost layer.

Variations in masking effects created by overstory algal layers made it difficult to accurately sample the crustose layers. Thus, seasonal changes may have been artifacts related to sampling methodology. 32 20.0 600

15.0 850 890 1030 10.0

5.0

15.0 660 H 780 910 QJ :> 0 10.0 u .1-J r I i r:: QJ 5.0 (.) H QJ P4

15.0 1090 680 840 10.0 780

5.0

June July Aug.Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. Nay ----- 1975 1976 ---

Figure 9. Bossiella californica ssp. schmittii Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 33

1200 60.0 890 50.0 40.0 30.0 20.0 10.0 Unharvested Area

60.0 H 660 Ill 50.0 :> 0 780 u 40.0 -1-J ~ Ill 30.0 (.) H Ill 20.0 P-< 10.0 June Harvested Area

60.0 780 680 50.0 I 1090 I I 840 40.0 30.0 20.0 10.0 October Harvested Area

June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. liar. Apr. May -----1975 ------1976---

Figure 10. Crustose Corallines Percent Cover ±95% Confidence Intervals and Sample Sizes in Each of the Study Areas 34 Trends in Algal Density

Percent frequency of occurrence values (percentage

of quadrats containing a given species regardless of abun-

dance) have also been tabulated for each species by area.

Since trends in density were generally similar to trends

indicated by quadrat occurrences (i.e., higher densities

also reflected broader spatial distributions), discussions

of frequency values are not presented for all species.

Instead, only those cases where trends in density did not

correspond with trends in frequency of occurrence are dis-

cussed where appropriate. Seasonal variations in percent

frequency of occurrence for each species can be referred

to by area in Tables 6-12.

Macrocystis pyrifera

Changes in adult densities. Seasonal density values

for Macrocystis pyrifera adults are illustrated for each

area in Figure 11. Adult t!· pyrifera plants were slightly more common in the nonharvested area throughout the year

compared to both harvested areas. Densities in the unhar- 2 vested area ranged from 1.0 to 1.4 plants/lOrn over the

course of the study. Densities in the June and October 2 harvested areas ranged from 0.7 to 0.9 plants/10m , and from 2 0.8 to 1.0 plants/10m , respectively. Little seasonal flue-

tuations in adult densities occurred within any of the study

areas despite canopy removal operations in the harvested I areas. Table 6. Percent Frequency of Occurrence Values for Macrocystis pyrifera Adults and Juveniles in Each of the Unharvested, June, and October Harvested Areas Over Time

Adults Unharvested Area 73.9 -- 53.3 -- 69.6 65.2 -- 65.2 65.2 65.2 60.9 52.2 June Harvested Area 40.0 40.0 55.0 ------40.0 ------40.0 October Harvested Area -- -- 42.8 -- 57.1 -- -- 47.6 -- -- 47.6 --

Juveniles Unharvested Area 69.6 -- 4.3 -- 0 0 -- 0 0 0 0 4.3 June Harvested Area 15.0 10.0 10.0 ------55.0 ------20.0 October Harvested Area -- -- 9.5 -- 4.8 -- -- 14.3 -- -- 38.1 -- Jme July Aug. Sept Oct. Nov. Dec. Jan. Feb. Mar. April May ------1975 ------1976 ---- Table 7. Percent Frequency of Occurrence Values for Pterygophora californica Adults and Juveniles in Each of the Unharvested, June, and October Harvested Areas Over Time

Adults

Unharvested Area 78.3 -- 69.6 -- 65.2 65.2 -- 60.8 52.2 56.5 52.2 52.2 June Harvested Area 35.0 4D.O 40.0 ------40.0 ------4D.O October Harvested Area -- -- 57.1 -- 66.7 -- -- 66.7 -- -- 61.9 --

Juveniles Unharvested Area 34.8 -- 8.7 -- 0 0 -- 0 0 0 0 0 June Harvested Area 20.0 5.0 0 ------15.0 ------20.0 October Harvested Area -- -- 23.8 -- 4.8 -- -- 0 -- -- 19.0 -- June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May ------1975 ------1976 ---- Table 8. Percent Frequency of Occurrence Values for Juvenile Laminariales in Each of the Unharvested, June, and October Harvested Areas Over Time

Unharvested Area 13.0 -- 0 -- 0 0 -- 0 0 0 39.1 52.2

June Harvested Area 15.0 15.0 15.0 ------15.0 ------20.0

October Harvested Area -- -- 9.5 -- 0 -- -- 4.8 -- -- 47.6 --

Jme July Aug. Sept. Oct. Nov. Dec. Jan. Feb. M3r. April May ------1975 ------1976 ----- Table 9. Percent Frequency of Occurrence Values for Cystoseira osmundacea Adults and Juveniles in Each of the Unharvested, June, and October Harvested Areas Over Time

Adults Unharvested Area 60.9 -- 56.5 -- 56.5 60.9 -- 60.9 56.5 52.2 52.2 47.8 June Harvested Area 55.0 45.0 35.0 ------35.0 ------40.0 October Harvested Area -- -- 66.7 -- 66.7 -- -- 61.9 -- -- 52.4 -- .

Juveniles Unharvested Area 39.1 -- 8.7 -- 26.1 17.4 -- 21.7 17.4 34.8 30.4 43.5 June Harvested Area 20.1 20.0 10.0 ------0 ------20.0 October Harvested Area -- -- 9.5 -- 4.8 -- 19.0 -- 23.8 ------. J1me July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May ------1975 ------1976 -----

UJ 00 Table 10. Percent Frequency of Occurrence Values for Schizymenia pacifica in Each of the Unharvested, June, and October Harvested Areas Over Time

Unharvested Area 73.9 -- 30.4 -- 30.4 26.1 -- 17.4 13.0 13.0 8. 7 0

June Harvested Area 20.0 25.0 20.0 ------20.0 ------0

October Harvested Area -- -- 4.8 -- 9.5 -- -- 14.3 -- -- 23.8 --

Jme July Aug. Sept. Oct. Nov. D=c. Jan. Feb. Mar. April May ------1975 ------1976 ----- Table 11. Percent Frequency of Occurrence Values for Weeksia reticulata in Each of the Unharvested, June, and October Harvested Areas Over Time

Unharvested Area 39.1 -- 8.7 -- 0 0 -- 0 0 0 4.4 4.4

June Harvested Area 20.0 20.0 15.0 ------0 ------0

October Harvested Area -- -- 4.8 -- -- 9.5 -- 0 -- -- 19.1 -- June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May ------1975 ------1976 ----- Table 12. Percent Frequency of Occurrence Values for Opuntiella californica in Each of the Unharvested, June, and October Harvested Areas Over Time

Unharvested Area 56.6 -- 47.8 -- 47.8 43.5 -- 43.5 39.1 39.1 43.5 56.6

June Harvested Area 35.0 30.0 30.0 ------35.0 ------10.0

October Harvested Area -- -- 47.6 -- 42.9 -- -- 57.1 -- -- 42.9 --

Jrn.e July Aug. Sept. Oct. Nov. fuc. Jan. Feb. Mar. April May ------1975 ------1976 ----- 42

2.0

~ 1.0

1.. ~ "". Unharvested Area (N=23)

2.0- N s June Harvested Area .....0 (N-20) --.._ .u"' !=1 .....ttl 10-< 1.0

z0 @ 1 Q) :8 . . 2.0 October Harvested Area (N=21) r

1.0

June July Aug.Sept. Oct. Nov. Dec. Jan. Feb. Var. Apr. May -----1975 ------1976---

Figure 11. Mean No. of Macrocystis pyrifera (adults)/10m2 ±95% Confidence Intervals in Each of the Study Areas. N Equals No. of 10m2 Plots Except for May 1976 in the June Harvested Area Where N=5 43

Changes in juvenile densities. Seasonal changes in

juvenile Macrocystis pyrifera densities were different

between study areas (Figure 12). In the unharvested area,

juvenile abundances ranged between 0 (fall/winter) and 0.7 2 plants/10m (spring/summer). In the area harvested in June,

juveniles were also present in the spring/summer months with 2 monthly densities ranging between 0.1 and 0.4 plants/10m .

However, an additional recruitment set occurred in winter.

In January, juvenile~- pyrifera abundances in the June area 2 were appreciably greater (2.0 plants/10m ) than those

observed during all other sampling periods with a maximum

of 30 plants occurring in one study plot. In the October

area, the seasonal abundance pattern of juveniles was more

similar to that described for the unharvested area. 2 Seasonal abundances ranged from 0.1 to 0.7 plants/10m with

greater abundances recorded in the spring and summer samp-

ling months. However, following canopy removal in the

October harvested area, juveniles were observed in April whereas in the unharvested area, juvenile ~- pyrifera plants were not observed until the following May.

Changes in surface canopy cover. Infra-red aerial

photographs of all kelp beds from Santa Cruz to Pismo Beach,

California are taken at 3-month intervals by the California

State Department of Fish and Game, Monterey. Photographic

inspection of the Carmel Bay kelp bed from 1973 to 1979 44

2.0

1.0 Unharvested Area (N=23)

5.0

N 1'1 June Harvested Area 0 4.0 .-I (N=ZO) ...... w"' ~ 3.0 ct1 .-I P-< 2.0 z0

~ ct1 1.0 Q) :;;::

2.0 October Harvested Area (N=21) 1.0

June July Aug.Sept. Oct. Nov. Dec. Jan. Feb. Mar.Apr. May ----- 1975 ------1976---

Figure 12. ~1ean No. Macrocystis pyrifera (juveni1es)/10m2 ±95% Confidence Intervals in Each of the Study Areas. 1r, N=5 45 indicates the canopy, at peak summer development, is similar in size and configuration from year to year. Visual esti­ mates of relative canopy cover for each photographic survey (abundant= 100% cover, moderate= 50% cover, sparse= 10% cover) indicate an annual cycle where canopy luxuriance in the spring/summer months alternated with canopy thinning in the fall/winter months (Figure 13).

Changes in canopy stipe lengths. Temporal trends in canopy reduction and recovery for each study area were also measured utilizing stipe lengths (unpublished data, D. Hunt) and are illustrated in Figure 14.

In the unharvested area, the seasonal behavior of surface canopy abundance depicted by stipe length measure­ ments (Figure 14) parallels that described by aerial percent cover (Figure 13). Canopy stipes were longest in the spring/ summer months. Fronds at this time extended over the surface and formed a complete canopy over the study area. Between

January and February, the surface canopy had thinned considerably when stipes were just at the surface level. By late February, the canopy was completely gone, and frond tips were lying roughly 1.5 meters below the surface. The surface canopy was regenerating by the following spring.

Immediately before cutting, stipe lengths in the June harvested area were similar to those in the nonharvested area, Immediately after cutting, frond tips, although not measured, were observed to be roughly 1.2 meters below the JStudy Period I

HEAVY

MODERATE

SPARSE F WSSFWSSFWSSFWSSFW SSF WS

l97:J---l974------197:>--- --l97o-----1977----1978--- -1979-

Figure 13. Relative Changes in Macrocystis pyrifera Canopy Cover for the Carmel Bay Kelp Bed from 1973 to 1979. See Test for Discussion of Relative Abundances 0 Unharvested Area (H=l8) '""'.w • ..c June Harvested Area (N=l3) bJ) +4.5 A----A :J:·M 0 QJ r-l!I! 5-··-··-m October Harvested Area (N=l6) .w QJ Ul>Qr-l QJ ' >'·M +3.0 Immediately After OCIIE-< Harvest ,..1 \ QJ !-< 4-l:>o 0 0 4-l .0 r-.~""d \ ...... ,s .w .wQJ +1.5 I _. ..A >' u I ..CCIICJ _. - .. .Wr-l!-1 _. \- - bJ)P., !-< \ - .. -·· >' 0 ·. .. QJ !-< u --- ...:ICJ>' I -- p.;::> 0 - \ >' ...... , r r ' QJ ;80CJ !-<

Figure 14. Macrocystis pyrifera Mean Canopy Frond Lengths in Each of the Study Areas 48 surface. Within a few weeks (July) fronds began to reappear on the surface, but lengths at this time were appreciably shorter compared to uncut stipes. Inspection of infra-red aerial canopy photographs of the June cut and uncut study areas indicated canopy cover in the June harvested area did not recover to uncut (control) levels until September

(photographs furnished by California State Department of

Fish and Game, Monterey).

In the area harvested in October, stipe lengths were also similar to those in the uncut area just prior to canopy removal. Stipes were then cut at a depth of 1.2 meters

(uncorrected for tidal height). Within a few weeks, frond tips had reached the surface, but at this time, frond lengths were still appreciably shorter compared to those in the uncut area.

Changes in stipe density. Stipe counts were obtained from the same plants used for measuring stipe lengths

(unpublished data, Doug Hunt). Multiplying the mean number 2 of stipes per plant with the mean number of plants per 10m 2 yielded estimates of the mean number of stipes per 10m for various periods (Figure 15) . Stipe densities in the unhar- vested area were greater during all seasons compared to those in both harvested areas. In the unharvested area, stipe densities declined nearly twofold from June to January, but were recovering by the following May. A different trend was observed in both harvested areas where stipe densities 0 $ Unharvested Area (N=18)

fli§-- -1J1 June Harvested Area (N=13) 50.0 &- .. -A October Harvested Area (N=16)

N cS 40.0 ...... 30.0 A------20.0 Bt =--:- - - -A z0 --·--·-.. -··-m 10.0 Before Harvest Measurements

June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May ------1975 ------1976 -----

Fieure 15. Macrocystis pyrifera Mean No. Stipes/10m2 in Each of the Study Areas 50 remained relatively stable from before harvest measurements throughout the remainder of the study period.

Pterygophora californica

Changes in adult densities. This species was more abundant in the unharvested area where seasonal abundance 2 varied between 2.0 and 5.2 plants/10m (Figure 16). In the 2 June area abundances ranged from 1.2 to 2.1 plants/10m .

In the October harvested area, seasonal density values 2 varied between 1.7 and 2.1 plants/10m . In the unharvested area, densities declined steadily throughout the course of the study representing an overall loss of roughly 60 percent of the adult population. Although plants were less common in the June area, densities also declined but the loss was smaller (37%). Pterygophora californica adult densities in the October area remained relatively stable.

Changes in subsurface canopy cover. The Pterygo­ phora californica adult population was partitioned into four categories based on blade condition: (1) mature blades; (2) senescent blades; (3) bare stipes (no blades); and (4) new blade growth. Seasonal trends in the relative proportions of thallus types are illustrated for the unhar- vested, June, and October harvested areas in Figures 17,

18, and 19, respectively.

In the unharvested area, blade bearing plants

(mature blades) were more common during the initial summer lr l 51

8.0 I . . I 7.0 6.0 5.0 4.0 3.0 2.0

1.0 Unharvested Area (N=23) N s 0 r--l Ul 4.0 ----.w . § . June Harvested Area (N=20) r--l 3.0 "'" 2.0 ...... 0 v z 1.0 * § (!) • • • • • • :E:

4.0 October Harvested Area (N=2l) 3.0 2.0 1.0

June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. }f.ar. Apr. t19.y ------1975 ------1976 ----

Figure 16. Mean No.Pterygophora californica (adults)/lOrn2 ±95/o Confidence Intervals in Each of the Study Areas. ·k, N=S 52

(N) 106 119 110 87 63 56 50 47 45

90.0 ~ 0 ·.4 Mature Blades ;Y. .w 80.0 . \ C1) ;til ..... I .. _ .. --1 ·. ;:l p. 70.0 ~--~ 0 p.. vi .w ..... 60.0 I ;:l Stipes (No Blades) "1:1 /~Bare ~ 50.0 ..... C1) I .w 0 40.0 E-< ""0 30.0 ~ / 0 •.4 20.0 .w ·.4 V' Ul 0 10.0 !§' 0 u .w ~ New Blade Growth Q) (j 30.0 )-I Jll, Q) Senescent Blades '2-f\ p.. ' 20.0 ' ' ',n/. I Q) ' ' ' \ ? ' ' •.4 ' ' 11 .ws ____ UJ I .w 10.0 ' -- -- \ C1) ' ~ ..... s \i. _.. ~ Q) _./, __ .g p:: - ', June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. V1ar. Apr. May 1975 1976

Figure 17. Pterygophora californica (adults) Relative Percent Composition of Four Morphological Categories in the Unharvested Area 53

(N) 34 41 29 24 6

100.0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0 r Bare Stipes (No ~1-~~~--·'lf 10.0 .;r··-'11-··-··-··- ··--v-··

20.0 Senescent Blades New Blade Growth ______rtfA ______..>"e- ...A 10.0 I ------~-~ Jme July Aug. Sept.Oct. Nov. Dec. Jan. Feb. Mar. Apr. VJay

-----1975 ---1976 ----

Figure 18. Pterygophora californica (adults) Relative Percent Composition of Four Horphological Cate­ gories in the June Harvested Area 54

(N) 35 43 45 45

90.0

80.0 Mature Blades/(/ 70.0

60.0

50.0

40.0 .· .. / \ 30.0 ~ \ Bare Stipes (No Blades)·· 20.0 / \ 10.0 .I/ \

20.0 New Blade Growth -A 10.0 ~Senescent Blades y,.....rJ -...... ? ...... ------1!11 June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. :t-'.ar. Apr. May -----1975------1976---

Figure 19. Pterygophora californica (adults) Relative Percent Cor.~position of Four Jvlorphological Cate­ gories in the October Harvested Area 55 sampling (Figure 17). At the end of the summer (August)

plants with senescent blades were common and by winter the majority of the population consisted of bare stipes. New

blade growth from bare stipes was noted as spring approached

and by mid-spring the relative abundance of plants with mature blades was beginning to recover. A similar pattern was noted in the October harvested area (Figure 19). How­

ever, the relative abundance of mature bladed plants in the

October area remained considerably higher compared to the

unharvested area. Furthermore, at the end of the study the

spring recovery of mature bladed plants in the October area was of considerably greater magnitude compared to the

unharvested area. Mature bladed plants were also the most

common form in the June area throughout the study period

(Figure 18). Highest abundance in the summer was followed

by a slight decline to the end of the study (spring). Con­

currently, there was less change in the relative abundance

of bare stipes. Although~- californica canopy regeneration

in spring was not observed by an increase in mature bladed

plants, plants initiating new blade growth were observed at

this time .. Similar changes in~- californica canopy reduc­

tion and recovery also appear in the percent cover data for

all study areas (Tables 3-5, pp. 26-28). Canopy cover never

exceeded 5.0 percent and thus shading exerted by this

species was unimportant. 56 The greater percentage of mature bladed plants in the harvested areas was not clearly related to increased light made available by giant kelp canopy removal. In the October area and before canopy elimination (August and October), mature bladed plants comprised the largest frac­ tion of the total adult ~- californica population. In contrast, in the unharvested area, mature bladed plants and bare stipes were in roughly equal proportions in August, and by October the majority of the population appeared as bare stipes. These preharvest data suggest natural changes in P. californica morphology can be different between areas. Thus, differences in plant morphology between areas after kelp harvesting cannot be conclusively determined as a response to variations in submarine illumination by kelp harvesting.

Changes in juvenile densities. In the unharvested area, juvenile Pterygophora californica were observed only during the initial summer sampling months. Abundances 2 ranged between 0.1 and 1.5 plants/10m (Figure 20). In the June area, juveniles were also present in the summer as well as the following spring with similar monthly abundances 2 ranging between 0.1 and 0.8 plants/10m . However, unlike the unharvested area, juveniles in the June area also occurred in winter and with the greatest dens.ity (3 .1 plants/10m).2 Up to 50 juvenile plants during this time 2 were counted in two of the lOrn plots. The January density F

57 3.0

2.0 Unharvested Area (N=23)

1.0

8.0

7.0 June Harvested Area (N=20)

N s 6.0 0 .._.-1 (JJ .w 5.0 r:: C\J .-1 4.0 !>-<

z0 3.0 ffi Q) 2.0 ~ 1.0 '"

2.0 October Harvested Area (N=21) 1.0

Jme July Aug.Sept. Oct. Nov. Dec. Jan. Feb. JVurr. Apr. May ----- 1975 ------1976 ----

Figure 20 Mean No. Pterygophora californica (juveniles) I 10m2 ±95% Confidence Interval in Each of the Study Areas, ·k, N=S 58 represented roughly a tenfold increase in abundance from the previous summer. In contrast, in the unharvested area, the summer to winter change in abundance represented roughly a twofold reduction.

In the October area, juvenile Pterygophora califor- 2 nica abundances ranged from 0 to 0.6 plants/lOrn across seasons (Figure 20) . Spring/summer/fall occurrences alter- nated with a winter absence, a pattern more similar to that observed in the unharvested area. However, juvenile P. califo=ica plants in the October area were observed in

April following canopy removal. In the unharvested area, juveniles were not observed at this time or during the remainder of the study.

Laminariales Juveniles

As described earlier, all members of the order

Laminariales appear similar when young, consisting of a simple blade growing from the tip of a short stipe. With- out further tissue differentiation, it is difficult to predict what species will eventually develop. Plants found in this state were treated as juvenile Laminariales. How- ever, since ~· pyrifera and~· californica were the only members of the order Laminariales observed throughout the course of the study, all juvenile Laminariales plants were assumed to be the immature stage of these species.

Seasonal densities for juvenile Laminariales plants are illustrated by area in Figure 21. 59

15.0 Unharvested Area (N=23) 10.0

5.0

15.0 June Harvested Area (N=20) 10.0

5.0

10.0 October Harvested Area (N=21) 5.0

JIID.e July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May ----- 1975 ------1976---

2 Figure 21. Mean No. Laminariales (juveniles)/10m ±95% Confidence Intervals in Each of the Study Areas. '", N=S 60 In the unharvested area, plants were present in the

spring and summer with monthly abundances ranging from 0.3 1 ~nts/10m 2 . Plants were absent during fall and . quite different trend was observed in the June

area. Like!:!· pyrifera and P. californica

s, juvenile Laminariales were present in spring and 2 (0.2 to 1.0 plants/lOrn), as well as in winter

cy), with the greatest observed abundance (5.1 plants/

The seasonal trend for juvenile Laminariales abund-

J in the October harvested area resembled that noted for

unharvested area. Abundances which ranged from 0 to 2.9 2 illts/lOm throughout the study period were greater in

ring and summer.

~ystoseira osmundacea

Changes in adult densities. Cystoseira osmundacea

adult densities were greater throughout the study period in

the October area versus the unharvested and June area

(Figure 22). Seasonal abundances in the October area varied 2 between 2.4 and 3.0 plants/10m , while abundances in the

unharvested and June harvested areas ranged from 1.3 to 1.8 2 2 plants/10m and from 1.0 to 1.7 plants/10m, respectively.

Seasonal variations in adult plant densities '"ithin each

study area were considered negligible.

Changes in adult morphology. The Cystoseira

I osmundacea adult population was partitioned into three ! I 61

Unharvested Area (N~23) - - ..._, .0 -

4.0 June Harvested Area (N~20) N 5 3.0 ·r ..... - 2.0 ,._. ., l.O '

-~ 0 z ' ' ' ' ' ~ ~ 5.0

4.0

3.0

2.0

l.O - October Harvested Area (N~2l)

June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. Har. Apr ..Hay -----1975 ------1976---

Figure 22. l1ean No. Cystoseira osmundacea (adults) I 10m2 ±95% Confidence Intervals in Each of the Study Areas. ·k, N=S 62 morphological categories: (l) basal; (2) intermediate; and

(3) erect. Seasonal trends in the relative proportions of thallus types are presented for the unharvested, June, and

October areas in Figures 23, 24, and 25, respectively. Data from all areas were too variable to detect any discernible seasonal patterns in plant condition. However, data in all study areas indicate that the majority of the C. osmundacea adult population throughout the study period occurred as the basal perennial form. Stipe lengths for nearly all erect plants in all study areas rarely exceeded 0.5 meters, and thus C. osmundacea did not effectively form a midwater or surface canopy. The relative abundances of erect plants in the unharvested area and June areas were not substantially different (Figures 23 and 24, respectively).

The unharvested area was probably not a suitable control for this species for the October area. Before harvest in August, a considerable portion of the f. osmun­ dacea population in the October area consisted of erect plants (Figure 25), while none were observed in the unhar­ vested area at the same time (Figure 23). The August observations indicate natural abundances can be different between areas. Therefore, the substantial increase in erect plants at the end of the study in the October area compared to no plants observed concurrently in the unharvested area was not convincingly a result of kelp harvesting. 63

(N) 41 38 35 42 33 31 30 36 32 ~ 0 'H .jJ n:1 .--< ;:l 100.0 p.. 0 4 P-< 90.0 Basal .jJ .--< ;:l "0 80.0 <: .--< n:1 .jJ 70.0 0 E-1 60.0 4-l 0

~ 0 50.0 'H .jJ 'H (/) 40.0 0 I "Y'Z- Intermediate ~ 0 30.0 I "' u " .jJ 20.0 I ..__ ~ " QJ )\ cJ I H Erect'I( )If QJ 10.0 \ P-< ! .. A!:!: ...... v QJ *=-·~"""" .. .. - .. ? •H .jJ June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. M3r . Apr. May n:1 .--< QJ 1975 1976 ~

Figure 23. Cystoseira osmundacea (adults) Relative Percent Composition of Three Morphological Categories in the Unharvested Area 64

(N) 30 33 27 24 6 0 •.-l .w" C\J r-l ;:1 p. 100.0 0 P-< .w 90.0 r-l r-Basal ;:1 '1j «: 80.0 r-l C\J .w 70.0 0 E-< lH 60.0 0

0 50.0 t •.-l .w" t •.-l til 40.0 I 0 rg I 0 30.0 u I .w 20.0 Q) f"L-' Erect "(j H r -~-::3 J Q) 10.0 D - _.4F= "'----:=..--=..:..-=- :..:._ ~ ;.:..:::--_.:.: - ' P-< ~At:'.. L._ Intermediate Q) :> ·.-l .w Jnne July Aug. Sept.Oct. Nov. fuc. Jan. Feb. Mar. Apr. May C\J r-l Q) ----- 1975 ------1976 ---- ~

Figure 24. Cystoseira osmundacea (adults) Relative Percent Composition of Three Morphological Categories in the June Harvested Area 65

(N) 56 64 56 52

4-< 70.0 0

~ 0 Yl_ Basal •.-1 ~ 60.0 +J 0 •.-1 •.-1 Ul+J om 50.0 p.,...< s ;::J OP. uo 40.0 P-< +J ~+J (J),...< 30.0 u ;::J Intermediate~)~- -- ~ .. 4.Erect 1-l'"d ill

Figure 25. Cystoseira osmundacea (adults) Relative Percent Composition of Three Morphological Categories in the October Harvested Area 66 Changes in juvenile densities. Data in the unharvested area suggest Cystoseira osrnundacea recruits during the spring/summer months (Figure 26). Abundances were greatest in June and the following May (1.0 plants/ 2 2 10m and 1.7 plants/10m , respectively). Abundances of 0.2 2 to 0.5 plants/10m were more common during winter months. Juvenile plants were less abundant in the June harvested area. Seasonal densities ranged from 0.2 to 0.5 plants/ lOrn 2 . Monthly abundances were too low to detect any seasonal pattern. Similar abundances were noted for the October harvested area where monthly densities ranged between 0.1 and 0.7 plants/lOrn.2

Schizymenia pacifica In the unharvested area, densities declined steadily from 5.5 plants/lOrn2 at the beginning of the study to no plants at the end of the study (Figure 27). Seasonal abundances in the June area were considerably lower, ranging between 0 and 0.5 plants/10m2 . The October area was similar to the June area; densities remained relatively stable ranging from 0.1 to 0.6 plants/lOrn2 over the course of the study period. The variations in seasonal trends between the study areas may not have necessarily been due to variations in available light. ~- pacifica is an annual plant (Abbott and Hollenberg, 1976). High mortality observed in the unhar- vested area may have been due to plants "living out their 67

3.0 Unharvested Area (N=23)

2.0

l.O

2.0 June Harvested Area (N=20) . l.O.

-~ i'--... ~ ' '

2.0

October Harvested Area (N=21)

1.0

June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. !:Jar. Apr. May -----1975 ------1976---

Figure 26. Mean No. Cystoseira osmundacea (juveniles)/10m2 ~95% Confidence Intervals in Each of the Study Areas. '", N=5 68 I I I 10.0 i

:Iq 9.0

8.0

7.0 Unharvested Area (N=23)

6.0

5.0

4.0

3.0

2.0 z0 1.0 @ z:Q) June Harvested Area (N=20)

2.0 October Harvested Area (N=21)

1.0

June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. Mar. Apr. May ------1975 ------1976---

2 Figure 27. Mean No. Schizymenia pacifica/10m ±"95% Confidence Intervals in Each of the Study Areas. ;, , N=5 69 life-spans." Plants in the harvested area may have settled more recently and consequently may have been younger. The relatively stable abundances noted from season to season in harvested areas may have been the result of younger plants persisting longer through the study period. Mortality could have been occurring in the harvested areas with densities being stabilized by recruitment. However, inspection of each quadrat through time indicated similar numbers of plants recorded throughout the study. This suggested the plants observed at the beginning of the study were the same plants noted at the end. If recruitment and mortality were co-occurring, one would expect greater variations in quadrat occurrences and densities within specific quadrats through time.

Weeksia reticulata

This plant was slightly more common during the spring and summer and absent during winter in all study areas

(Figure 28). The highest recorded monthly abundance in the ? unharvested area was 1.1 plants/lOrn-. In the June and

October areas, the greatest monthly abundances were 0.5 2 2 plants/10m and 0.8 plants/10m , respectively.

Opuntiella californica

Seasonal variations in Opuntiella californica densi­ ties are presented for each study area in Figure 29. For each of the study areas, densities were generally lowest in --- --~-~~~~-

70 2.0

l.O Unharvested Area (N=23)

l.O

June Harvested Area (N=20)

l.O October Harvested Area (N=2l)

June July Aug. Sept.Oct. Nov. Dec. Jan. Feb. }1ar. Apr. May ------1975 ------1976 ----

? Figure 28. Mean No. Weeksia reticulata/lOm~ ±95% Confidence Intervals in Each of the Study Areas. '', N=5 71 9.0

8.0 Unharvested Area (N=23) 7.0 6.0 5.0 4.0 3.0 2.0 1.0

3.0 - June Harvested Area (N=20) 2.0 - - 1.0 -

I I I T • •

4.0 October Harvested Area (N=21)

3.0 2.0 1.0 1 June July Aug. Sept.Oct. Nov. fuc. Jan. Feb. Jvlar. Apr. May -----1975 ------1976 ----

2 Figure 29. Nean No. Opuntiella californica/10m ±95% Confidence Intervals in Each ot the Study Areas. ·k, N=S 72 the fall and greater during the other seasons. In the unharvested area, maximum and minimum monthly density values 2 2 were 5.1 plants/10m and 1.2 plants/10m , respectively. In the June harvested areas, abundances ranged between 0.8 and 2 1.2 plants/10m throughout the study period. In the October area, seasonal densities varied between 1.2 and 2.3 plants/ 2 lOrn .

The Effects of a June Harvest

The mechanized removal of the surface canopy in June significantly enhanced recruitment densities of Macrocystis pyrifera, Pterygophora californica and juvenile Laminariales,

6 months following canopy removal (January). The abundance of ~- pyrifera juveniles in the harvested area exhibited a substantial increase 6 months following canopy removal, while a decrease was noted in the unharvested area over the same time interval (Figure 12, p. 44). Seasonal densities for each area were significantly different (P< .05, Kruskal­

Wallis test, Table 13). Abundances in the harvested area increased significantly from June (pre-harvest) to January

(post-harvest) sampling periods (P < .05, Newman-Kuels test,

Table 14). In contrast, a significant decrease was noted in the unharvested area for the same time span (P <.OS,

Newman-Kuels test, Table 15).

Pterygophora californica juvenile densities in the harvested area also increased appreciably from summer to 73

Table 13. Two-Tailed Kruskal-Wallis Test of Macrocystis pyrifera Juvenile Abundances in Each of the Unharvested, June and October October Harvested Areas

Null Hypothesis 2 No significant diff. in H/D a X .05(a-l) Significance abundances

Unharvested Area 43.97 9 15.07 p < . 05•'(

1 June Harvested Area 10.42 4 7.81 P< . 05 ''

October Harvested Area 10.18 4 7.81 P< . os-~<

"'Reject Null Hypothesis

Table 14. Newman-Kuels Multiple Comparisons Test of Macrosystis pyrifera Juvenile Abundances in the June Harvested Area

Null Hypothesis No significant diff. in .05 Significance abundances

January vs. all other months 5.73 2 2. 77 p < • 05>\-

All other month combinations p > . 05

*Reject Null Hypothesis 74

Table 15. Newman-Kuels Multiple Comparisons Test of Macrocystis pyrifera Juvenile Abundances in the Unharvested Area

Null Hypothesis No significant diff. in .OS Significance abundances

June vs. August 9.67 2 2. 77 p < .OS* vs. May 6.51 3 3.31 p < . 05"' vs. all other months 5.67 4 3.63 p < . 05"' Aug. vs. May 0.05 2 2. 77 p > .OS vs. all other months 1. 08 3 3.31 p > .05

May vs. all other months 1. 56 2 2. 77 P > . OS

All other month combinations P >.OS

"'Reject Null Hypothesis 75 winter (January) sampling periods, while a decrease was noted in the unharvested area (Figure 20, p. 57). However, results from the Kruskal-Wallis test (Table 16) indicate that seasonal densities in the June harvested area were not significantly different, while significant differences did occur in the unharvested area. Results of the multiple comparisons test for the unharvested area show that the winter (January) abundance was significantly lower than abundances recorded for the June summer sampling period (P < .05, Newman-Kuels test, Table 17). Although P. cali­ fornica juvenile densities in the June harvested area increased from summer to winter, the change in abundance was not significant due to extreme patchiness. The winter juvenile influx was observed in only three of the 30 quadrats (15 percent frequency of occurrence, Table 7, p. 36). High plant densities that occurred in only three of the 20 quad­ rats in winter did not yield abundance ranking patterns significantly different from other months which had fewer plants distributed across similar numbers of quadrats. Trends in density for juvenile Laminariales in the unharvested area were similar to those observed for Macro­ cystis pyrifera and Pterygophora californica juveniles (Figure 21, p. 59). Densities in the June area increased substantially from summer to winter, while in the uncut area, densities declined. The decrease in abundance from June to January in the uncut area was significant (P< .05, 76

Table 16. Two-Tailed Kruskal-Wallis Test of pterygophora californica Juvenile Abundances in Each of fhe Unharvested, June and October Harvested Areas

Null Hypothesis 2 No significant diff. in H/D a x .o5(a-l) Significance abundances

Unharvested Area 48.13 9 15.07 p < . o5·1: June Harvested Area 5.58 4 7.81 p > .05 October Harvested Area 6.02 4 7.81 p > . 05

.,.,Reject Null Hypothesis

Table 17. Newman-Kuels Multiple Comparisons Test of Pterygophora californica Juvenile Abundances in the Unharvested Area

Null Hypothesis No significant diff. in .05 Significance abundances

June vs. August 9. 71 2 2. 77 p < . 05.,.,

vs. January 7.59 3 3.31 p < . 05'~

vs. all other months 6.49 4 3.63 p < . 05'''

August vs. January 1. 63 2 2. 77 p > . 05

vs. all other months 2.14 3 3.31 p > . 05

January vs. all other months 1.56 2 2. 77 p >. 05

All other month combinations p >. 05

.,.,Reject Null Hypothesis 77 Kruskal-Wallis test, Table 18 followed by Newman-Kuels test ' Table 19). However, as with~- californica juveniles, the summer to winter increase in juvenile Laminariales in the

June area was not significant (P> .05, Kruskal-Wallis test,

Table 18). The winter appearing juvenile Laminariales plants in the June area were concentrated in only three quadrats

(15 percent frequency of occurrence, Table 8, p. 37) and thus the winter distribution did not create significantly differ­ ent ranking abundance patterns by the Kruskal-Wallis test.

The removal of the surface canopy in June did not modify seasonal trends in plant density and percent cover for all remaining species.

The Effects of an October Harvest

The hand harvesting of the Macrocystis pyrifera surface canopy in October significantly enhanced ~- pyrifera recruitment and the abundances of Pterygophora californica juveniles in April. Juvenile densities of ~- pyrifera in both the October and unharvested areas were greatest during the spring and summer months and lowest during the fall and winter seasons (Figure 12, p. 44). Results of the Kruskal­

Wallis test indicate seasonal densities for each area were significantly different (P< .05, Table 13, p. 73). However, the recovery interval following the low winter density period was shorter in the October area. Significant differ­ ences between the winter and later spring sampling periods 78

Table 18. Two-Tailed Kruskal-Wallis Test of Juvenile Laminariales Abundances in Each of the Unharvested and June Harvested Areas

Null Hypothesis 2 No significant diff. in H/D a x .05(a-l) Significance abundances

Unharvested Area 73.70 8 15.07 p< . 05'~ June Harvested Area 0.63 4 7.81 P> .OS

'~Reject Null Hypothesis

Table 19. Newman-Kuels Multiple Comparisons Test of Juvenile Laminariales Abundances in the Unharvested Area

Null Hypothesis No significant diff. in .OS Significance abundance

May vs. April 6.08 2 2. 77 P< . 05"' vs. June 10.39 3 3.31 p< . 05"' vs. all other months 10.08 4 3.63 p< . 05'''

April VS. June 9.46 2 2. 77 p < .OS*

VS. all other months 9.35 3 3.31 p< . 05''' June vs. all other months 4. 52 2 2. 77 p < . 05"' All other month combinations p > .05

'~Reject Null Hypothesis 79 in the October area occurred as early as April (P< .05, Newman-Kuels test, Table 20). In the unharvested area, a significant recovery of juvenile densities did not occur by April or May (P> .05, Newman-Kuels test, Table 15, p. 74). In the unharvested area, no P. californica juvenile

plants were observed throughout the latter half of the study, while several plants were encountered in April in the October area (Figure 20, p. 57). The loss of plants in the uncut area from June throughout the remainder of the study period was significant (P< .05, Kruskal-Wallis test, Table 16 followed by Newman-Kuels test, Table 17). No significant changes in plant abundances occurred in the

October area (P > . OS, Kruskal-\~allis test, Table 16). Removal of the surface canopy in October did not alter the seasonal abundances of other species. Seasonal density and percent cover trends for all other species were not different between the unharvested and October cut areas. 'i

80

Table 20. Newman-Kuels Multiple Comparisons Test of Macrocystis pyrifera Juvenile Abundances in the October Harvested Area

Null Hypothesis No significant diff. in .05 Significance abundances

April vs. January 3.93 2 2. 77 P< . 05'" vs. August 3.02 3 3.31 p < . 05'" vs. October 2.69 4 3.63 p > .05

January vs. August 0.59 2 2. 77 P> .05

vs. October 0.95 3 3.31 P> .05 August vs. October 2.69 4 3.63 p > .05

'"Reject Null Hypothesis DISCUSSION

The Effects of Harvesting on Understory Algae

In the present study, harvesting in June and October altered recruitment timing of Macrocystis pyrifera and Pterygophora californica. Harvesting did not modify seasonal trends for 27 other species. Seasonal trends in

~- pyrifera juvenile abundances in the unharvested area show natural recruitment occurred only during the spring and summer months (Figure 12, p. 44). The mechanized removal of the ~- pyrifera surface canopy in summer (June) resulted in significantly greater abundances of juvenile ~- pyrifera sporophytes 6 months later in January (Tables 13, 14, p. 73). In contrast, seasonal abundances of juvenile sporophytes in the unharvested area declined significantly over this same time period (Tables 13, 15, pp. 73, 74). Juvenile }1. pyrifera plants in the unharvested area were not observed until later in May. These data suggest harvesting in June advanced natural recruitment timing by at least 5 months, and that recruitment is largely a function of available light. Many winter appearing juveniles did not survive to the end of the study or reach adult status probably because of early storm related mortalities. Indirectly, this is 82 suggested by the lack of change in adult Macrocystis pyrifera densities in the June area after a decline in juvenile abundances (Figures 11 and 12, respectively, pp.

42, 44). Furthermore, in other studies at least 80 percent loss of juvenile plants has been noted as a result of exces­ sive water motion (Gerard, 1976). Rosenthal et al. (1974) noted a reduction of 387 to five juveniles in 9 months was caused by sand scour and burial. North (1971) stated that juvenile plants are more vulnerable to erosion than older plants because of their poorly developed holdfasts.

Harvesting in October resulted in significantly greater numbers of new Macrocystis pyrifera individuals the following April (Tables 13, 20, pp. 73, 80). In the unhar­ vested area, no ~· pyrifera juveniles were observed at this time, but a large number of juvenile Laminariales plants were encountered. Presumably, these plants would have eventually developed into ~· pyrifera and/or Pterygophora californica since these species were the only members of the order Laminariales observed throughout the study period in all areas. By the following month (May), several juvenile

~· pyrifera plants were noted in the unharvested area. These data suggest that harvesting in October advanced the natural timing of juvenile M. pyrifera recruitment by at least l months.

The distribution, recruitment, and life span of

Macrocystis pvrifera microscopic stages from which the 83 sporophytes arose were not determinable. A variety of life spans has been reported. Using submerged test panels, Aleem

(1973) and Foster (1975) recorded roughly a 2~ and 2-month time interval respectively, from the time of zoospore settlement to the subsequent appearance of juvenile sporo­ phytes. Neushul (1963) noted a similar 2- to 3-month time interval for zoospore to development in the laboratory. He also noted that 10 to 13 days were required to complete the zoospore to phases, and an additional 35 to 40 days were necessary for subsequent sporophyte initiation. By in-situ adult transplant studies in barren areas at 9 meters depth, Anderson and North (1969) and North (1968) also recorded roughly a 3-month interval for before juvenile sporophytes appeared. However, from similar experiments at 15 meters depth, juveniles did not appear until 7 to 8 months following sporophyte transplan­ tations. Presumably this was due to lower light levels in deeper water. Neushul and Haxo (1963), Anderson and North

(1966a) and North (1966) suggested that the sexual stages can persist in the sea for more than a year in a resting state under minimal illumination. Furthermore, Anderson and North (1966a, 1967) and Anderson (1967, 1968) found in-situ spore liberation throughout the year in southern

California. Fertile sori were noticed on plants throughout the study period in Carmel Bay. Similar observations have been made by Sparling (1977) along the San Luis Obispo 84 coastline. Apparently, !i· pyrifera continually "seeds" beneath its own canopy, enabling recruitment and/or growth when canopies thin by storms or by kelp harvesting. Factors influencing the spatial distribution of sporophytes include the dispersal patterns of the micro­ scopic stages. Anderson and North (1966b) transplanted adult Macrocystis pyrifera plants in attempts to "seed" areas devoid of vegetation. They later observed new sporo­ phytes concentrated near the transplanted adults, with decreasing densities short distances away (4 meters). How­ ever, dispersal range increased considerably with increased number of parent plants. North et al. (1969) noted critical distances between male and female were important for fertilization success. The distance between males and females increases with increasing distance from parent plants. However, they also mentioned that ova could be extruded from female gametophytes thereby facilitating dis­ persal. Drift plants and dismembered sporophylls also provide mechanisms for plant dispersal, but these methods were considered unimportant by Lobban (1978a).

Spore concentrations and release rates have also been studied in the field by Anderson and North (1966a, 1966b, 1967) and Anderson (1967, 1968). Spores were liber­ ated in concentrations of roughly up to 76,000 spores/ minute/cm2 sporophyll surface. High variation was found between plants and between sporophylls of the same plants. 85 No relationships between spore release rates and age, loca­

tion, or depth were found. On the other hand, Neushul

(1963) noted spore production increased with plant weight.

To the writer's knowledge, there have been no studies to

determine if kelp harvesting affects spore production by cut

plants. However, Anderson and North (1966a) suggested that

canopy damage by elevated surface temperature might lower

spore production.

Since zoospores and gametophytes have been found to

exhibit wide ranging life spans and dispersal patterns, it was assumed that all ~1acrocystis pyrifera microscopic stages were present in all study areas throughout the period of

investigation. Thus, differences in recruitment patterns

between study areas were probably the result of differences

in submarine illumination acting on gametophytes and

settled spores and not other factors such as temperature,

nutrients, currents, etc., or chance acting on spore produc­

tion. Study areas were established adjacent to one another

and it is unlikely that the microscopic stages were absent

in the uncut area. In fact, based on findings of Anderson

and North (1966b) that liberated spores are most concen­

trated around parent plants, microscopic stages may have

been more abundant in the unharvested area where adult M.

pyrifera plants were more common.

The life cycle of Pterygophora californica is

similar to that followed by all other members of the order 86 Laminariales (McKay, 1933). Seasonal abundances in the unharvested area suggest that in Carmel Bay, this plant recruits during the spring and summer months (Figure 20, p. 57). Spore production was presumably greatest during these months in the areas studied since blade bearing plants were most abundant then, while stipes lacking blades were more common during the winter months (Figures 17-19, pp. 52-54). Spore release probably occurred prior to blade detachment but possibly continued from dismembered blades as found in luetkeana (Nicholson, 1970). In different environments, McPeak et al. (1974) and Sparling (1977) indicated that fertile P. californica plants can be found throughout the year. To the writer's knowledge the only information pertaining to the developmental times for the

~- californica microscopic stages is from a settling plate study conducted at a depth of 3.3 meters near San Luis Obispo, California. A period as short as 4 to 6 months was documented for the developmental time from zoospore settle­ ment to the appearance of an identifiable ~- californica juvenile sporophyte, while less than a week was the sug­ gested time interval from zoospore attachment to development of a juvenile Laminariales blade (personal communication, C. Ehrler) . Schmitz and Lobban (1976) found that Pterygophora californica sporophytes can translocate, and stated this may be a mechanism whereby photoassimilates could be stored in 87 perennating portions of plants to initiate new blade production when favorable conditions arise. Frye (1918) discussed yearly blade sloughing and regeneration in P. californica sporophytes and suggested the number of attached blades and the attachment scars marking blade positions of previous years' grm

recruitment times similar to those observed for ~- pyrifera (Figure 20, p. 57). In the unharvested area, juvenile plants were noted only during the initial few months of the study. The loss of plants from June throughout the remainder of the study period represented a significant decline

------~· ...... 88 (Tables 16, 17, p. 76). In both harvested areas, P. californica recruitment occurred at times when no juveniles were observed in the unharvested area. In the June area, 2 new plants were most common in January (3.1 plants/10m).

In the October harvested area, new individuals were observed in April. Although recruitment periodicities were different between the unharvested and harvested areas, recruitment densities in each of the harvested areas were not signifi- cantly different with season (Table 16, p. 76). This was because new plants were concentrated in too few quadrats to detect significant differences using statistical tests based on ranking abundances. In all likelihood, many of the winter appearing juveniles in the June area did not persist long due to storm mortalities. Presumably, those that did or plants which appeared later were too rare to affect population density estimates.

Canopy removal in October also advanced Pterygophora californica recruitment timing to April. In the uncut area,

P. californica recruitment was not observed by the end of the study. However, many juvenile Laminariales plants were observed in April and May. Presumably, some of these plants would have soon developed into identifiable P. californica plants. Premature recruitment pulses in the harvested areas were assumed to be in response to increased light made available by surface canopy removals. Understory algae can 89 also potentially shade-out juveniles developing below them, and understory algal removal could allow new plants to mature. Differences in spatial and seasonal understory

cover between areas could have produced the observed vari­

ations in recruitment appearances. However, understory

layering structure in each of the study areas was considered

"thin" (roughly one layer per point) and relatively similar across study areas (Figure 5, p. 22). Thus, the overstory

Macrocystis pyrifera surface canopy was considered the domi­ nant shade producer for all study areas.

Although understory layers were relatively uniform

across study areas, slight variations in surface canopy

development and thickness may have existed which possibly resulted in variations in shading effects. If surface

canopies were not removed in the June and October areas,

and if these areas had thinner canopies and consequently more light than the uncut area, the advanced timing of

juvenile appearances could have been a natural phenomenon

rather than an effect of harvesting. Pre-harvest Hacrocystis

pyrifera adult plant and stipe densities in the June and

October areas were similar to each other but lower than

those in the uncut area (Figures 11 and 15, respectively,

pp. 42, 49). Lower pre-harvest plant and stipe densities

in the June and October areas indicate that surface canopies,

if not removed, may have been less developed that the uncut

area. Higher relative abundances of erect Cystoseira 90 osmundacea in the October versus unharvested area prior to kelp harvesting also suggest natural light levels were greater in the former area (Figures 23 and 25, respectively, pp. 63, 65). If surface canopies were left intact, sub­ marine illumination would have possibly been greater in the June and October areas relative to the uncut area, and the winter appearance of juvenile ~· pyrifera and Pterygophora californica sporophytes may have occurred naturally without kelp harvesting. In the June area, juvenile ~· pyrifera and K· californica plants appeared in winter (January). If harvesting had no effect other than to enhance what would occur naturally, then one would also expect a similar winter

~· pyrifera and K· californica juvenile influx in the adjacent October area. However, in the October area, juvenile sporophytes were not observed in winter with den­ sities similar to those seen in the June area (Figures 12 and 20, pp. 44, 57). Significantly greater densities occurred later in spring (April). Relative to the April appearances of juvenile ~· pyrifera and K· californica plants in the October area, these plants were observed later in the uncut area. Therefore, these data suggest harvesting, regardless of month, advanced recruitment timing of new M. pyrifera and K· californica sporophytes. This also appears as a time lag effect whereby a summer harvest produces a winter effect, and a fall harvest produces a spring effect. 91 The months when new juveniles in the harvested areas were observed were not the months when plants actually first appeared. For each area there was roughly a 3- to 4-month interval between the time when advanced recruitment was noted and the times of previous observations when fewer or no plants were noted. The development of new plants occurred sometime during these intervals. Regardless of the actual times of juvenile development, the winter observations of new plants the following spring relative to control area abundances which lacked winter recruitment. Early storm related mortalities buffered potentially wide differences in later plant abundances between uncut and summer cut areas.

Recruitment periodicities in the October (fall) cut and unharvested areas were more similar. This was because the mechanized canopy removal in October occurred closer to the

time of natural canopy reduction in the unharvested area.

Due to recruitment similarities between the October and uncut areas, it was assumed that later population abundances within

these areas, although not measured, would also not have been appreciably different.

The Effects of Harvesting on Adult Macrocystis pyrifera

Although the primary objectives were to examine

changes in understory algae after giant kelp harvesting,

some observations were made on the cut plants themselves.

North (1959c) suggested harvesting may increase cut plant 92 longevity. By reducing canopy drag, the probability of

total plant removal by storms would be lowerd. During the

time of study, differences in uncut versus cut plant survi­ vorship through one winter storm period were negligible.

Adult Macrocystis pyrifera densities in all study areas

remained relatively stable throughout the study period

(Figure 11, p. 42). It was assumed that the majority of

adult plants occurring in the sample plots at the beginning

of the study were the same plants recorded at the end of

the study. This is probably true, as individual quadrats

in all study areas did not vary appreciably in adult plant numbers through time. Furthermore, population turnover was

considered small since few juveniles developed into adults.

Although no differences in plant survivorship were noted between cut and uncut plants, differences in stipe

densities did occur (Figure 15, p. 49). Stipe densities in the uncut area decreased roughly twofold from summer to winter and increased as summer again approached. In

contrast, stipe densities in the harvested areas varied little over time. Under natural conditions, North (1961) estimated the average life span of uncut fronds to be 6 months, and Aleem (1973) found tensile strength decreased with frond age. Presumably, the losses of uncut stipes were

the result of having a greater probability of breakage by winter storms. Furthermore, broken s tipes frequently. entangle with other stipes creating additional losses. The 93 stability in numbers of cut stipes through time was presumably due to the reduction of drag effect and thus a

lower probability of breakage and complete loss. Some

fronds were undoubtedly lost during winter storms, but the

losses were balanced by the development of new fronds. Kelp harvesting is said to promote development of uncut subsur­

face fronds by permitting more light to penetrate through

the water column (North and Hubbs, 1968; Aleem, 1973).

Furthermore, Lobban (1978b) found translocation to favor young developing fronds when parent fronds were cut. These

data suggest that while individual plant survivorship may not necessarily be altered by kelp harvesting, individual

stipe longevity and/or the production of new stipes can be

enhanced.

11iller and Geibel (1973) have reported that surface

tissue removal, by reducing translocation of photoassimi­

lates to holdfasts, may result in slower holdfast develop­ ment. In contrast to North's suggestion that canopy

removal may enhance plant longevity by lower drag effect,

they theorized that reduced holdfasts size may result in

premature losses of entire plants. The work reported here

lasted only 1 year, perhaps too brief a time to detect

differences in the life spans of harvested versus non­ harvested plants. Moreover, observations were not made on

holdfast growth. Under natural conditions, the maximum age

of an individual Macrocystis pyrifera plant is roughly 4 to 94 8 years (North, 1971; Rosenthal et al., 1974). Currently, long-term field tagging studies are being conducted in

Carmel Bay to test if plant longevity is altered by harvest­ ing (C. Barilotti, personal communication).

Rosenthal et al. (1974) postulated that the removal of surface canopies promotes more variation in Macrocystis pyrifera age class distributions by intermittently permitting successful juvenile replacement. Harvesting would appear to have similar effects provided that favorable conditions for juvenile development such as the lack of storms and absence of severe grazing pressures coincide with the timing of the harvest.

General Community Overview

North (1971) described three types of temporal changes in Macrocystis pyrifera kelp beds: regular, non­ regular, and lack of changes. The following is a summary of these patterns. Regular kelp beds are those which appear and disappear at regular intervals. Examples are those located near Del Mar and Oceanside, California which have been known to fluctuate on roughly a 4-year cycle. Spores and gametophytes are continually present on the bottom and provide quick juvenile sporophyte replacement following canopy loss by storms.

Nonregular changing kelp beds are those that when lost, do not necessarily return to Macrocystis pyrifera ------

95 dominated forests. In most cases, these kelp beds are subject to severe grazing pressures which limit all algal development. When grazing pressures are lifted by diminishing food sources, opportunities for plant develop­ ment increase. The resulting plant community may not

necessarily return to ~- pyrifera dominance. Kelp beds which do not change are exemplified by those situated near Point Conception. These have been known to persist up to 17 years. Understory algae, as well as juvenile Macrocystis pyrifera sporophyte abundances, are

suppressed underneath the thick canopies. The~- pyrifera population sustains itself by massive vegetative growth of new fronds produced on old plants. The Carmel Bay kelp bed as well as many other kelp beds along the Monterey Penninsula display regular changes but on an annual cycle. The Carmel Bay surface canopy undergoes a yearly cycle of summer luxuriance alternating with winter reductions (Figure 13, p. 46). Juvenile Macro­ cystis pyrifera sporophyte recruitment is most successful during the spring months when seas are calm and before the surface canopy becomes sufficiently developed to shade out smaller plants. Similar annual cyclical patterns have been described for nearby kelp beds situated off Point Pinos by Faro (1969) and off Hopkins Marine Station by Gerard (1976) and Miller and Geibel (1973). 96 In Carmel Bay, harvesting once during the summer and fall provided "new windows" for understory development but for only a short period of time. In the June and October harvested areas, roughly 3 months were required for canopies to recover to control abundances. Similar recovery periods following harvesting have been noted by other workers.

Aleem (1973) also noted a 2- to 3-month period for canopy restoration following harvesting. Miller and Geibel (1973) noted that canopy recovery times differed with season of cutting: 2 to 3 months for spring harvests and 4~ months for fall harvests.

Canopy removal in June and October modified recruit­ ment timing of Macrocystis pyrifera and Pterygophora californica. The variations in recruitment timing indicate that for these species the occurrence of new plants is largely a function of light and that microscopic stages can be present throughout the year. Other algal species are given an opportunity to develop following mechanized canopy removal, provided spores are present at the time of harvest.

However, without a full understanding of light requirements for other species, it is assumed that most species already present in a kelp bed are "shade conditioned" and may not necessarily respond or respond quickly to elevated light levels. Species which are "light-loving" are more often not present beneath kelp canopies and therefore their appearance in a newly illuminated kelp bed environment would be the 97 result of longer range spore dispersal from parents growing in habitats elsewhere. Despite the appearance of "light­ loving" species, the quickly reformed Macrocystis pyrifera surface canopy would suppress their development. On the other hand, Foster (1975) demonstrated that the first individuals to appear on fresh substrates in kelp beds were species other than those within the immediate areas. These species ,.;ere rapid-growing, short-lived ephemerals. However, the ephemerals were eventually replaced by perennial algae more characteristic of the mature adjacent areas. Once perennial algae become estab­ lished, their presence and shading inhibited the appearance of new species. In the Carmel Bay study areas the more signific.ant resident understory algae, based on numerical abundances, were the perennial crustose and articulated coralline algae and Pterygophora californica. The coralline algae were important in terms of primary space occupancy. They formed extensive crusts and mats over the bottom. Crustose and articulated corralline algae have been noted to be important components in many kelp beds (Aleem, 1956, 1973; McLean, 1962; Neushul, 1964; Devinny and Kirkwood, 1974; Pearse and Lowry, 1974). Growth rates of crustose coralline algae are known to be slow (Adey, 1970a, 197Gb) as are those of articulated coralline algae (Johansen and Austin, 1970; Foster, 1975). Although noticeable changes in abundances 98 would not be expected to occur within the time studied, greater changes may take place over longer periods.

Pterygophora californica was also a conspicuous plant within the study areas, and harvesting altered recruitment timing. The subsurface canopies formed by such plants as ~- californica, like the surface canopy provided by Macrocystis pyrifera, can regulate understory composition and abundance (McPeak et al., 1974; Dayton, 1975; Hruby,

1976; Kain, 1976; Reed, in prep.). Since P. californica canopy abundances within the study areas never exceeded 5.0 percent cover (Tables 3-5, pp. 26-28), ~- californica was not considered an important shade producer during the time of the study. However, due to its perennial growth habits, this species has the potential of continually adding new plants under favorable conditions, and shading pressures exerted by ~- californica may become more important over longer time spans than the present study considered. North

(1966) and McPeak et al. (1973) stated that once established, thick P. californica canopies can suppress ~- pyrifera recruitment. However, given similar opportunities for development, North (1966) noted if there is one juvenile

~- pyrifera plant for every 100 juvenile P. californica plants, ~- pyrifera will eventually predominate. Pearse and Hines (1979) observed areas devoid of vegetation caused by intensive sea urchin (Strongelocentrotus franciscanus) grazing. In less than 1 year after mass sea urchin 99 mortalities by disease ~· pyrifera, ~· californica, Laminaria dentigera, and foliose red algae appeared. One year later all understory species had thinned considerably due to shading by the newly formed ~· pyrifera surface canopy. Long-term changes in understory community struc­ ture are therefore likely to be smaller than the immediate effects due to the persistence and quick canopy forming abilities of ~· pyrifera.

Unlike understory species, Macrocystis pyrifera regulates the composition of associated species by function­ ing as the dominant shade producer. Wide changes in under­ story structure can occur following canopy removal but are likely to be limited by quick ~· pyrifera surface canopy recovery. Even in the Paradise Cove boating channel where plants were cropped on a daily basis resulting in adult plants with. fewer stipes, the~· pyrifera population was able to sustain itself via higher recruitment. If canopy cutting pressures were removed, ~· pyrifera would presum­ ably quickly outshade smaller statured plants. Similarly, in the Monterey Bay kelp bed harvested three times in 1 year resulting in loss of canopy forming plants, many

~· pyrifera juveniles were observed developing on the bottom (Miller and Geibel, 1973). Complete canopy recovery following entire plant loss by storms has been observed to occur within a single year by Rosenthal et al. (1974) and

Barrales and Lobban (1975). Pearse and Hines (1979) 100 observed the expansion of ~· pyrifera into previously dominated sea urchin areas within 1 year. Foster (1975) noted that community maturation, based on the establishment and growth rates for ~· pyrifera, could also be attained in

1 year, while understory community maturation following disturbances would require longer time periods up to 10 years.

Miller and Geibel's (1973) observations of increased

Gigartina spp. abundances in an area harvested three times in 1 year and North's (1957, 1959b) observations of higher juvenile Macrocystis pyrifera densities as well as foliace­ ous understory algal cover in a boating channel cut continu­ ally over 2 years probably reflect modifications induced by overharvesting. Repeated cuttings at high frequencies in the same areas reduced the numbers of adult plants. This resulted in areas not only lacking a surface canopy for long time periods, but also reduced the shading effect exerted by the midwater floating stipe bundles. Harvesting at lower frequencies, which allows surface canopies to recover and leaves midwater canopies intact, would have less dramatic effects. North (1957, 1959b) observed an area in the

Paradise Cove kelp bed after it was commercially harvested and noted no differences in ~· pyrifera and understory abundances compared to adjacent uncut areas. This writer's observations in the Carmel Bay study areas suggest that canopy removal at a frequency of once per year regardless 101 of timing, produces short-term changes in the abundance of some understory algae. However, wide differences between cut and uncut areas are quickly buffered by storm-related mortalities and rapid surface canopy recovery. While maximum cover and yearly oscillations in the !:!· pyrifera surface canopy cover from 1973 to 1979 have not been altered by harvesting (Figure 13, p. 46), !:!· pyrifera plant density, biomass, and age class distributions may be affected over longer time intervals either by harvesting directly and/or indirectly by longer term changes in competitive interactions with other algal species for light and space. CONCLUSIONS

1. Annual harvesting operations (1973 to 1979) have not altered the seasonal oscillations in surface canopy cover or the configuration of the Carmel Bay kelp bed. 2. The Macrocystis pyrifera surface canopy recovers quickly from artificially or naturally caused reductions in population abundances. Following mechanized canopy removal, surface canopies recovered within 2 to 3 months by continued elongation of cut stipes and enhanced growth of uncut sub­ surface fronds. 3. The Macrocystis pyrifera quick canopy recovery abilities and winter storms operate synergistically in buffering wide changes in understory abundances between harvested and uncut areas. During the 1 year study, harvest­ ing at a frequency of once per year, regardless of timing, did not appreciably alter understory algal abundances relative to abundances within uncut area. Although canopy removal in June resulted in greater concentrations of Macrocystis pyrifera and Pterygophora californica juvenile sporophytes in January (5 months prior to natural recruit­ ment in the uncut area), many plants did not survive long due to early storm-related mortalities. Canopy removal in October had a lesser effect in altering recruitment perio­ dicities. An October harvest produced greater abundances 103 of !i· pyrifera and !:· californica juveniles in April, roughly 1 month prior to recruitment observed in the uncut area. Since recruitment times in the October and uncut

areas were similar, later adult population abundances in

these areas, although not measured, were assumed to also have been similar.

4. Additional changes in understory algal abund­ ances within once-per-year harvested areas may be manifested in longer time periods than the present study considered.

5. Harvesting the same areas more than once per year may produce more dramatic effects. LITERATURE CITED

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