THE EFFECTS OF COMPETITION FOR LIGHT AND SPACE ON THE PERENNIAL ALGAL ASSEMBLAGE IN A GIANT (MACROCYST!$ PYRIFERA) FOREST

A thesis submitted to the faculty of San Francisco State University in partial fulfillment of the requirements for the degree Master of Arts

by DANIEL CLIFFORD REED San Francisco, May 1981 THE EFFECTS-OF COMPETITION FOR LIGHT AND SPACE ON THE PERENNIAL ALGAL ASSEM-BLAGE IN A G KELP ( PYRIFERA FOREST

Daniel Clifford Reed San Francisco State University 1981

The algal assemblage in the sheltered giant at 1·1- water Cove in Carmel Bay, California, consists of a Macrocystis £Y!j_­ fera surface canopy, a dense subsurface canopy of pterygophor~ califor­ nica and an understory of articulate and encrusting coralline . Shading by the kelp canopies can reduce light reaching the bottom an order of magnitude. To determine the effects of the P. californica canopy on algal recruitment and growth, half of a mature stand of P. cal i forn ica was removed in May 1978 and changes were fo 11 owed in per­ manent quadrats established in this area as well as in an undisturbed control area. In the experimenta 1 area, high recruitment of fi. ~­ fera and P. californica and low recruitment of Desmarestia ligulata ssp. ligulata occurred later that No algal recruitment occurred in the control site. When M. pyrifera and .E_. cal ifornica ts were continually removed in same area the next year,~· ligu1ata became more abundant. Comparison quadrats cleared of the ght coralline understory indicated the f.. ca1ifornica canopy also inhibi- ted algal growth as the re-establishment of the line understory was significantly lower in quadrats located under the P. californica canopy. displays a greater flue on in canopy density and cover than P. cal ifornica, s lar experimental clear- ings of the surface canopy suggest it is also capable of suppressing algal recruitment and growth. Inhibition by the dense coralline understory was observed as highest rates of algal colonization were found in upright coralline removal quadrats located in the removal site.

In these areas, there was high recruitment of~· californica, Macro­ cystis pyrifera, Desmarestia ligulata and moderate to low recruitment

of .Q_. kurilensis, luetkeana and fleshy red algae. Signi­ ficantly fewer recruits were counted in coralline understory control quadrats. Slow-growing coralline algae recruited year-round, but these small plants had 1ittle effect on faster-growing brown and fleshy red algae which recruited in the spring. Competition for space does not appear important in this system, as lowest rates of algal colonization were recorded in quadrats scraped to bare rock. These results suggest that competition for light has a strong .influence on algal recruitment and growth in the kelp forest under­ story. Many which coloni.zed following the removal of dominant and corall ines are common to the understories of nearby forests subjected to higher and more frequent levels of disturbance. Without continual di:sturbance, the dominant perennials would soon become re­ established, as their recruitment was also high. The importance of / competition in structuring thi.s perennial algal community appears to result from the relatively low rates of both biological and physical disturbance at Stillwater Cove.

--~------ACKNOWLEDGEMENTS

I thank my major advisor, ~~ichael S. Foster, for his friendship, advice and enthusiastic support, and for instilling in me an apprecia- tion for marine algae. His sharing of ideas on marine communities has been a most stimulating and valuable experience. The other members of my committee, Michael N. Josselyn and John S. Oliver, provided con­ structive comments which considerably improved drafts of the manu­ script. Discussion with J. Barry, J. Estes, C. Harrold and A. Hurley helped to clarify my thinking on the presentation of the data. I would also like to thank R. Ogren for sharing his work and ideas on the ecology of Pterygophora californica. The field work could not have been accomplished without the help of diving partners D. Rose and R. VanWagenen. P. Bentivegna, J. Heine, G. Ichikawa, M. Kelly and R. Walker also provided invaluable assistance in the field. M. Kellogg identified the invertebrates associated with the coralline mats. Special thanks to J. Barry for generously providing the painstaking knowledge of computers. R. Stelow typed the manuscript and L. Me Masters prepared the figures. I am grateful to the Pebble Beach Association for allowing access to Stillwater Cove. Most of all, my thanks go to Director John H. Martin and the faculty and staff of Moss ' Landing Marine Laboratories for providing such a unique and stimu- lating environment in which students can gain a working knowledge of the marine sciences. Support for the field research was provided by Moss Landing Marine Laboratories and a gradute research grant from The David and Lucile Packard Foundation.

v TABLE OF CONTENTS Page INTRODUCTION. . 1

STUDY SITE. . . 4

METHODS. 6

RESULTS .. . • 10

Pterygophora Removal. . . 10 Cora 11 i ne Understory Treatments...... 11 Yearly Fluctuations...... 14 Canopy Effects of Light Reduction. 15 Seasonal Effects ...... 16

DISCUSSION...... 19

LITERATURE CITED. 28

APPENDIX I ..... 33

APPENDIX II. . . 35

FIGURES. . . • • 36

TABLE 1. . . 56

vi .J..------LIST OF FIGURES Figure 1 Location of study site...... 36 2 Diagrammatic representation of experimental manipu-

lations...... 38 3 Initial algal percent cover...... 40 4 Algal percent cover 270 days after Pterygophora removal ...... 42 5 Percent cover of algal understory prior to coralline

removal ...... 44 6 Percent cover of algal understory 130 days after

coralline removal...... 46

7 Seasonal variation in light reduction. 48 8 Percent cover of Desmarestia 1 igulata. 50 9 Percent cover of Desmarestia kurilensis. 52 10 Percent cover of Galliarthron tuberculosum ...... 54

vii .J..------INTRODUCTION

Light is a major limiting resource in many terrestrial plant communities, as plant shading may cause light levels to fall well below the compensation point (Harper, 1977). This often has pro­ nounced effects on the understory assemblage. Because of their I striking vertical stratification, giant kelp forests are often com­ pared to terrestrial forests (Kuhnemann, 1970; Neushul, 1971; Foster, 1975a) and correlative studies suggest shading may effect understory

algae in a similar way (Kitching, et ~., 1934; Dawson, et ~., 1960; Mclean, 1962; Kain, 1966; Foster, 1975b). The effects of light may be even more dramatic in marine systems, as its intensity and quality are also altered by water. When a resource such as light becomes in short supply (i.e., due to shading), competitive interactions for this resource may occur. Dayton (1975a) demonstrated a high degree of competition among three kelp canopy guilds by experimentally removing canopy species in an Alaskan kelp corrmunity. Similarly, Pearse and Hines (1979) observed an increase in understory algal cover following an experimental re­ moval of the surface Macrocystis pyrifera canopy in a giant kelp for­ est in central California. The hypothesis that competition for pri­ mary space is important in structuring marine communities has been well documented for animal and plant-animal interactions (Connell, 196la, b; Paine, 1966, 1979; Dayton, 1971; Lubchenco, 1980), yet evi­ dence that space competition among algal species is important in structuring plant populations is weak.

1

...~------2 The intensity and rate at which a system is disturbed also play an important role in regulating the algal assemblage. Barrales

and Loban (1975) examined several Macrocystis pyrifera forests off Chubut, Argentina and correlated distinct differences in al compo- si on to the degree of wave exposure. The algal communities ex- posed forests were characterized by a rich red algal flora, whereas \ understory in more sheltered areas was dominated by the green al Codium vermilara. In areas of moderate wave exposure, the brown gae Lessonia sp. and Zonaria sp., along wtth the articulate coralline Corallina officinalis, prevailed. Similarly, biological disturbance in the form intense grazing (primarily by sea urchins) has been reported to restrict the local distribution of algae in a wide vari

of subtidal algal assemblages (Leighton, et ~., 1966; Jones and Kain~

1967; Ogden, et ~., 1973; Breen and Mann, 1976). Results from these investigations and others (Aleem, 1956; Neus

et ~·, 1967; Divinny and Kirkwood, 1974; Divinny, 1978) suggest that many factors may be involved in the regulation of unders 1 associations in giant kelp forests. Light, nutrients and suitable space to settle and grow are essential for plant growth, and inter­ actions among the plants for these resources probably pl a s fi- cant role in the regulation of algal communities. The present study considers the effects of light and space on the

perennial algal assemblage in a sheltered ant p forest i few sea urchins. The system is characterized a surface of Macrocystis pyrifera, an understory canopy of the lked kelp, Pterygophora californica, and a bottom cover composed of articulate 3 and encrusting coralline algae. Light was manipulated by selectively removing the two kelp canopies and upright portions of the coralline understory. Subsequent changes were followed and compared with appro­ priate controls. The effect of newly created space on algal community structure was examined by further comparisons with areas scraped to bare rock. These experiments evaluated two basic questions: (1) \ What factors favor the dense coralline understory and exclude faster growing brown and fleshy red algae which flourish in nearby exposed forests? (2) What role do the kelp canopies and the coralline under­ story play in maintaining the structure of this algal community? STUDY SITE

Experiments were conducted in a Macrocystis pyrifera forest at

Stillwater Cove in Carmel Bay, California (36°34 11 N. lat.; 12P 56 11 W. long.) (Figure 1). The cove opens to the south and the forest is thus protected from large northerly swells associated with winter storms as well as strong northwesterly winds characteristic of the \ spring. The forest grows on a hard, moderate-relief substratum of sandstone, conglomerate and lava (Simpson, 1972). Low water motion and lack of suspended sediment result in relatively clear water, and M. pyrifera plants are found at depths below 30 m. The kelp forest is characterized by two distinct kelp canopies, a thick surface canopy of Macrocystis pyrifera and a subsurface canopy formed by another perennial kelp, Pterygophora californica. This latter species forms dense stands and attains a· height of approxi­ mately 2 m. Macrocystis pyrifera is generally excluded from these stands, but tends to grow around their perimeter; however, frond growth at the surface produces a canopy overlying the P. californica stands. Seasonal changes are apparent in both kelp canopies, but fluctuation is greater in M. pyrifera. Maximum plant density and cover are found in the summer, with a reduction occurring in the

winter and early spring (Foster, et ~., 1979). The understory algae beneath Pterygophora californica are also perennial species consisting predominantly of articulate and encrust­ ing corallines. The articulated coralline Calliarthron tuberculosum is the most conspicuous component of this bottom cover, and its en- 4 5 tangled fronds form dense mats which carpet the bottom. Calliar­ thron cheilosporoides is also occasionally found in the area, as is I

Bossiella californica ssp. schmitti and~- orbigniana s~p. orbigniana. Encrusting forms of the genera Lithothamnion and Lithophyllum occupy space underneath these mats and elsewhere, as very little bare rock is found in the cove. Fleshy red algae comprise only a small portion of \ the understory and those species that do occur (Plocamium carti­ lagineum, Laurencia suboppositta and Botryoglossum farlowianum ssp. farlowianum) are most often found growing as epiphytes on f. tuber­ culosum. Sessile invertebrate cover is low except on vertical walls. The study site was a relatively flat terrace comprising an area of approximately 150m2. It was located in the center of the forest at 15 m depth and contained a dense stand of Pterygophora californica. Only two Macrocystis pyrifera plants were found growing in the study site at the beginning of the study.

I

I t I __ ._i ______METHODS

All data were collected and all manipulations were performed usi

SCUBA. To determine the effects of the Pterygophora cal ifornica

canopy on understory algal recruitment and growth, 547 mature f_. californica plants were removed from half of the 150m2 study area in May 1978 (hereafter referred to as the Pterygophora removal si ). \ Plants were removed by cutting the stipe just above the holdfast. other half of the study site was left undisturbed and monitored as a control. Before the removal, the understory algal species composition

and cover were determined using a modification (Foster, 1975a) of the point contact method employed by terrestrial plant ecologists (Goodall,

1952; Grieg-Smith, 1964). The survey device consisted a metal bar l min length to which the ends of a 1.2-m long string were at opposite ends of the bar. Three knots were tied at random in the string. To determine cover, the bar was haphazardly dropped through the P. californica canopy and followed down by the investigator. string was pulled tight and the knots were pres down to s stratum one at a time. diver then noted plants intersecting an imaginary vertical line perpendicular to the bottom passing through a knot. Water motion may move blades or of p1 back and forth over a knot. These species were noted as being over the knot even if their presence was intermittent. Six , three on each side of the bar, were recorded from each cast .. For compara­ tive purposes, each cast of the bar (six points) was considered a sample. Species and/or varieties of Calliarthron Bossiella til/ere

6 7

s nguished in the sampling~ and encrusting corallines were identified. In the months following f. californica removal, changes in the algal communi were noted through rect observation, and in February 1979, quantitative sampling as described above was again conducted in the Pterygophora removal and control sites. 1 statistical comparisons were performed on values normalized wi an

\ arcsine transformation (Sokal and Rohlf, 1967). gae were identifi according to Abbott and Hollenberg (1976). To study interactions among the canopy-forming kelps and the coralline understory, permanent quadrats were established in both Pterygophora removal and the control sites in March 1979 and selective removals were made. To test the hypothesis that coralline al was affecting the recruitment and growth of other algae, the upright corallines were removed within ten l m2 quadrats located in the Pterx­ gophora removal site. A paint scraper was used to clear the ants and care was taken to remove only the upright cora 11 i nes and their epiphytes. Furthermore, the hypothesis that crustose coralline algae may inhibit the recruitment and growth of other species was tes scraping the coralline crust from a (0.25 m) 2 area 1 in of the ten l m2 quadrats in which the upright corallines had been re- moved. An impact hammer, powered by compressed air from a tank, was used to clear the substratum. a control, ten 1m2 quadrats were observed in which the coralline understory was left s The twenty l m2 quadrats were arranged so that one quadrat was ad- jacent to at least two others, Within this linear arrangement, quadrats were randomly placed to reduce the bias introduced in the 8 location of the different treatments. Identical treatments equivalent replicates were established in the Pterygophora control site. A diagrammatic representation of the experimental treatments and their controls are given in Figure 2. To return the understory its original assemblage9 all plants

~1/hi had recruited into the Pterygophora removal site since the ini~ tial P. californica earing were removed. In addition, for the remainder of the study, newly settled Macrocystis pyrifera and californica, which readily colonized the Pterygophora removal site (see Results) were continually removed as soon as they were distin­ guishable (usual at a length near 5 em). Algal cover in the PterL­ gophora control remained undisturbed. All quadrats were sampled before any clearing took place. The technique used in sampling was the same as that described earlier, with the exception that the metal sampling bar was haphazardly placed within the quadrats. A total of twenty points was surveyed in each 1 m2 quadrat. A (0.25 m) 2 frame, subdi ded into one hundred squares, was used to visually estimate percent cover in quadrats had scraped to bare rock. Sampling was conducted periodically from February 1979 to July 1980. During this time, experiments were moni­ tored on a weekly to biweekly basis.

Different species algae are known to be repi~oductive at ferent times of the year. Therefore, in August 1979, in order to examine possible effects due to seasonal differences in algal o- zation, five of the ten replicates of both upright coralline removal and upright coralline control quadrats located in the Pterygophor~ removal site were recleared of pl ich recruited that spring. 9 Due to the low recruitment observed in the March earings (see Results), quadrats located in the Pterygophora control site and the 2 (0.25 m) quadrats scraped to bare rock in the Pterygo~hora removal area were not recleared. Additional clearings were performed in November 1979, when five new replicate quadrats of each of the three coralline understory treatments (coralline control, upright coralline

\ removal and scrape to bare rock) were established in the Pter~gophora removal site. The abundance of algal spores and their abili to disperse may greatly effect distribution patterns of attached plants·. To determine the effect of spore availability on recruitment patterns, several species of fleshy red algae which were shown to be reproductive in laboratory were put in nylon mesh bags and anchored to the bottom. The bags were placed in each of the three coralline understory ments in the Pterygophora removal and control sites. The species of

red algae used in this experiment included Gigartina corymbifera~ Neoptilota densa, Callophyllis pinnata and Iridaea sp. Light measurements were taken within the study area ce a maximum and minimum canopy development in to determine the amount of light reduction occurring under the various kelp ies. ALi Cor Model Ll-185A Quantum/Radiometer/Photometer was used for this analysis. All measurements were taken during late morni hours

overcast skies using quantum sensors (surface and i measured only photosynthetically active radiation. RESULTS

Pterygophora Removal Prior to any experimental manipulations, the algal cover in the proposed Pterygophora removal and control sites was very similar (Figure 3). A complete cover of large f. californica was present in both the removal and control sites and similar plant densities were \ recorded (9.2/m2 in the removal site and 7.3/m2 in control; p > .05, two-sample t-test). The bottom cover in the two sites consisted al­

~ost exclusively of upright and encrusting coralline algae with other species comprising < 1% of the total algal cover. In May 1978, the time at which Pterygophora californica was cleared, virtually all of the Macrocystis pyrifera canopy at the study site had been removed as a result of unusually high storm activity during the previous winter. Within three months after the clearing, a substantial surface canopy of M. pYrifera had developed in the Ptery­ gophora removal site. This cover resulted from the recruitment of new plants rather than regrowth from old holdfasts, as visual observations

indicated that M~ pyrifera and f. californica rapidly colonized the newly cleared area. By October 1978, counts from twenty haphazardly

placed 1 m2 quadrats in the Pterygophora removal site revealed the

following plant densities: f. californica 17.6 ± 3.4 (S.E.)/m2; M. pyrifera 9.6 ± 1.4 (S.E.)/m2; and 1.6 ± 0.41 for the brown alga Desmarestia ligulata ssp. ligulata (hereafter referred to as Desma­ restia ligulata). In February of the following year, the surface canopy of Macro- 10 11 cystis pyrifera, although reduced, still persisted, and the under­ story was dominated by young Pterygophora californica and M. pyrifera plants (Figure 4). Oesmarestia ligulata cover was relatively low, accounting for 4.2%. Little change was recorded in the coralline

/ bottom cover, and fleshy red algae were still conspicuously absent.

In the control area where thej~_; californica canopy remained unchanged, \ there were no significant changes recorded in the understory from the

onset of the study (Figure 3 vs Figure 4). The term 11 recruitment 11 , as used here, is based on the visual observations of young rather than observations on the settlement of microscopic spores or .

Coralline Understory Treatments The remova 1 of Macrocysti s pYri fera, Pterygophora ca 1i forni ca and Desmarestia ligulata from the Pterygophora removal site in March 1979 returned the understory" to a coralline bottom cover. The algal cover in both the Pterygophora removal site and the unmanipulated Ptery­ gophora control was quite similar in all three of the proposed coral­ line understory treatments (Figure 5). With the continual removal of young Pterygophora californica and Macrocystis pyrifera sporophytes from the Pterygophora removal site, Desmarestia ligulata became more abundant when compared to the pre­ vious year (Figure 4 vs Figure 6). Although a controlled experiment was not performed, this suggests that young f.. californica and M. pyrifera outcompete Q. ligulata. Desmarestia ligulata tended to grow in the gaps within the coralline mat. Some recruitment of this alga 12 was noticed on the coralline mat itself, but these plants often became dislodged before attaining a large size. Recruitment of Q. kurilensis, along with two species of fleshy red algae, Bonnemaisonia nootkana and Callophyllis flabellulata, also occurred, but the cover of these / plants remained quite low (Figure 6). A comparison of algal cover in the upright coralline removal quad­ rats with the cover found in coralline controls in the Pterygophora removal site (Figure 6) 130 days after coralline understory treatments were initiated revealed no significant differences in the Desmarestia 1igul ata cover between the two treatments (p > .05 two-sample t-test). Desmarestia ligulata is capable of attaining lengths to 8 m (Abbott and Hollenberg, 1976) and can form a dense, low-lying canopy in other kelp forests {pers. cbs.). Consequently, the blades of individual plants from one quadrat frequently overlapped nearby quadrats. Since quadrats of the different coralline understory treatments were often adjacent to each other, this overlap was incorporated into the percent cover estimates and tended to bias the data toward a higher cover for Q. ligulata. To avoid this bias; counts of young sporophytes were made in May 1979, sixty-three days after clearing. They revealed signi­ ficantly greater numbers of Q. ligulata recruits growing in the upright coralline removal quadrats when compared to the coralline control (112.0 plants/m2 vs 24.7 plants/m2, p < 0.01 Mann-Whitney U-test). Simi 1arly, the occurrence of young Macrocysti s pyrifera and f.. ca 1i­ fornica was also different. Their combined mean density prior to remova 1 in May 1979 was 324. 5/m2 in the coralline remova 1 quadrats, but only ll.8/m2 (p < 0.01 Mann-Whitney U-test) in the coralline \

13 control. The surface canopy-forming kelp Nereocystis luetkeana was ob­ served growing in the upright coralline removal quadrats when Macro­ cystis pyrifera and Pterygophora californica recruits were continually / removed. Six plants were recorded, but only two eventually, reached the surface. Nereocystis luetkeana was not found growing in any other \ treatment. Similarly, somewhat higher cover of Desmarestia kurilensis and fleshy red algae was recorded in the upright coralline removal quadrats (Figure 6), but these differences were not significant (p > 0.05 two-sample t-test). Moreover, as in the coralline control quad­ rats, recruitment and subsequent cover of these plants were low. Lowest rates of recruitment were observed in quadrats scraped to bare rock (Figure 5). Encrusting coralline algae comprised the majority of the algal cover in these quadrats. Most of this plant material con­ sisted of basal crusts of upright coralline forms, as much of it later developed into Calliarthron tuberculosum. Recruitment of Desmarestia

ligulata and the foliose red alga Gigartina corymbifera was also o~­ served, though it was very low and variable for both species. Fifty­ five percent of the surface in these areas remained bare rock and showed no signs of colonization. No algal recruitment occurred in any of the three coralline understory treatments located in the undisturbed Pterygophora control site in the 130 days following the start of the experiment (Figure 6). Quadrats which werescraped to bare rock showed no signs of algal colonization. Algal recruitment was not observed in these scraped areas until early November 1979, 250 days after the time of clearing. 14

At this time, 11 encrusting coralline algae 11 began to appear.

Yearly Fluctuations The study was continued through two growing seasons with the peak

/ in brown algal recruitment beginning each spring (late April to early May) within one week of each other. Recruitment continued for a period of approximately four weeks and then tapered off. All species \ of present in the study site seemed to recruit at this time. Young Macrocystis PYrifera and Pterygophora californica sporo­ phytes were observed at other times of the year, but always in very small numbers. Recruitment of fleshy red algae seemed to occur during the same time, with the exception of the perennial species Gigartina corymbifera and Weeksia reticulata, which first appeared in the fall. There was no peak observed in coralline algal recruitment; new plants were found throughout the year. Based on the two seasons sampled, yearly fluctuations in the com­ position and cover of algae which recruited into the study site appeared to be low (Table 1). Desmarestia ligulata cover was high both years, but Q. kurilensis cover was substantially lower. Nereo­ cystis luetkeana did not appear in the summer 1980 sampling, although it was observed in the spring of that year, but again only in upright coralline removal quadrats. It, along with several species of fleshy red algae, began to show signs of deterioration early in the growing season, were gone by late June and consequently were not recorded in the July sampling period. 15 Canopy Effects on Light Reduction The amount of light reduction occurring as a direct result of the various kelp canopies is given in Figure 7. Shading was most apparent in July under a combined Macrocystis pyrifera and Pterygophora cali­

/ fornica canopy, where 97% less light was recorded when compared to an area of similar depth devoid of both kelp canopies. It was at this \ time of year when maximum canopy development occurred. Both kelp canopies independently accounted for an 88% reduction in light (July 1980). In March when the cover of the two kelp canopies was at a minimum, t· californica continued to substantially reduce surface light penetrating to the bottom (to 53%). Unfortunately, no data were recorded at this time of year for theM. pyrifera canopy. Aerial photographs, though, indicate that a sparse surface canopy was present (R. VanWagenen, pers. comm.), suggesting that the shading effects by M. pyrifera during the winter and early spring were probably low. The overlying Macrocystis pyrifera canopy was removed from the study site in April 1980 before the start of the second growing season. Isolated recruits of Pterygophora californica, Desmarestia ligulata and the foliose red alga Weeksia reticulata were later ob­ served growing under the t· californica canopy in this area. These plants were found in all three of the coralline understory treatments, but their numbers were exceedingly low (< l/m2) when compared to the Pterygophora removal site. The plants were located in quadrats near

the edge of the f~ californica canopy or in areas of less dense canopy cover, where light intensity was probably higher. The effects of the Macrocystis pyrifera canopy on algal recruit- 16 ment were investigated in ng 1980 in a nearby Pterygopho~ cali- fornica stand in which the surface M. pYrifera canopy was not removed. Similar coralline understory treatments were performed, both under- neath and outside the f. californica canopy. In contrast to the

Pterygophora removal site in which the ~1. pYrifera canopy had been removed, no springtime recruitment of brown or fleshy red algae was observed in this experiment in any of the cora 11 i ne understory treat­ ments located outside the f. californica canopy. Moreover, no algal recruitment occurred in treatments located under the combined P. cali- fornica and M. pyrifera canopies.

Seasonal Effects The time at which the clearings were performed seemed to have little effect on the composition of the algal community l Quadrats cleared at different times of the year were colonized similar species during the same seasons. Desmarestia ligulata, annual brown alga, showed a peak in cover in the summer months and little or no cover in the winter. This was true for all three the clearing dates in all three of the coralline understory treatments located in the Pterygophora removal site (Fi 8). Desmarestia kurilensis showed similar trends, but with much lower cover (Figure

9). In July 1980, a difference in~- ]igulata cover on three di ent clearing dates was observed in both the coralline control and upright cora 11 ine remova 1 quadrats (p < 0.05 two- factor s difference was due to the low cover observed in the ll clearings s as the cover of D. ligulata in the nter and summer clearings was 17 lar (p > 0.05 Newman-Keuls test). No si ificant differences among earing dates were found at any time in quadrats scraped bare rock. Calliarthron tuberculosum showed a slow but steady increase in cover which was independent of the time of its removal (Figure 10). This increase was probably the result of regrowth from basal crus Recruitment of C. tuberculosum was evident throughout the year in quadrats which were scraped bare, although there seemed to be a lag period ·as colonization was not immediate after scraping igure 10), This lag period may be due to the difficulties encountered in s- nguishing young coralline species. In the coralline control quad­ rats, £. tuberculosum cover remained relatively constant throughout the study (Figure 10). Comparison of the upright coralline removal quadrats located in the Pterygophora removal site with those 1oca ted in the Pterygophora control site suggested that not only did kelp canopies inhibit al 1 recruitment, but they may also have limited vegetative growth, cover of Calliarthron tuberculosum in July 1980 resulted from the regrowth of basal crusts and was signi higher in Pterygophora removal site (p < 0.05 two-sample t-test), Similar comparisons of coralline control quadrats revealed a higher cover f.. tuberculosum in the Pterygophora removal site as opposed

Pterygophora control (p < 0.05). Species other C. tubercolusum were too rare to use in similar comparisons. Colonization by reproductively active fleshy algal ies 18 corymbifera were observed growing within a 1 m radius of the mesh bags located in the Pterygophora removal site. These recruits grew slowly, remained small and never formed a substantial cover. No settlement was observed in the Pterygophora control site.

\ DISCUSSION

The results of these experiments suggest strong competitive interactions among the vari.ous macroalgal species, which are of major importance in structuring the subtidal algal community at Stillwater Cove. Canopy-forming kelps inhibited algal recruitment and growth, and light appears to be the major limiting resource. The removal of \ the Pterygophora californica canopy led to a dramatic increase in understory algal cover, as light increased by a factor of ten. In contrast, the algal understory was quite sparse in the heavily shaded Pterygophora control site where plant recruitment was quite low. In a typical year, both the surface and subsurface canopies pro­ bably play an equal role i~ight reduction. The Macrocystis pyrifera canopy quickly recovers following the winter period of frond detach­ ment and reduced-growth, and by mid-spring, a substantial surface canopy usually forms. This canopy is sufficiently dense to indepen­ dently inhibit springtime germination of brown and fleshy red algae. Pterygophora californica displays a less obvious reduction in cover in the winter than does M. pyrifera and has a canopy which provides sub­ stantial shading, even during times of minimum canopy development (Figure 6). Consequently, the f.. californica canopy is also suffi­ ciently dense by spring to independently inhibit springtime germina­

tion. McPeak, et ~· (1973) noted similar inhibitory effects by f.. californica on M. pYrifera settlement in the kelp forest off Point Lorna, California. In abnormal years, storms may remove entire plants of Macrocystis 19 20 . pyrifera and/or a higher proportion of attached fronds, resulting in a greater reduction in the surface canopy. As a result, canopy res­ toration is delayed and, in this case, dependent on recruitment and growth of new plants. Pterygophoracalifornica, unlike M. pyrifera,

'\ possesses a thick, "woody" stipe which is very difficult to break. Loss of entire plants after storms is rarely observed at Stillwater \ Cove. This characteristic, along with its subsurface habit, helps it to persist through these periods of high water motion, since catas­ trophic removal, as described by Rosenthal, et ~· (1974) forM. pyrifera, does not occur. Consequently, despite the drastic reduction in the M. pyrifera canopy, springtime germination continues to be inhibited by the more persistent f.. californica canopy. Evidence for the persistent nature of Pterygophora californica comes from their large size {approximately 2 m) and assumed old age. Like many kelps, f... californica forms cortical rings in the stipe. As many as eighteen rings were.counted in plants removed from the study area. If these rings are annual as proposed by Frye (1918), and documented for hyperborea (Kain, 1963}, these stands of f. californica are relatively long-lived and appear to be of uniform age. During springtime germination of 1978 and 1979, the surface canopy of Macrocystis pyrifera was quite sparse, as a result of a large number of storms encountered during previous winters. Shading effects by this canopy were therefore low. On the other hand, removal of Pterygophora californica triggered a large recruitment of brown, and to a lesser extent fleshy red, algae, indicating that shading by

f. californica was significant. During the spring of 1980, the fv1. 21 pyrifera canopy was well developed. This surface canopy was experi­ mentally removed at this time and algal recruitment was similar to that observed in the spring of 1979 (Table 1). No recruitment occurred in control areas where M. pyrifera was not removed. Apparently high recruitment of f. californica, which may lead to the formation of dense stands, occurs during years of greater storm activity and re­ \ duced M. pyrifera canopy.~ The coralline understory also plays an important role in struc­ turing the algal community. The coralline mat inhibits algal recruit­ ment which was significantly increased when the upright corallines were removed. Although no actual measurements were taken, the amount of light reaching spores or small plants beneath the dense coralline mat was probably low, greatly reducing their chances, for survival. Removal of the erect portions of the coralline mat did not increase primary space because coralline holdfasts were left intact. These holdfasts provided suitable space for algal settlement, indicating that coralline mats had a greater influence on light than primary space. Furthermore, if space were limiting, highest rates of coloni­ zation should occur in quadrats scraped to bare rock. On the con­ trary, the lowest rates of algal colonization occurred on bare rock treatments. Light may not be totally responsible for the low rates of algal colonization into the coralline mats. Inhibition of settlement caused by the abrasive action of algal fronds has been documented in inter­ tidal comnunities (Black, 1974; Dayton, 1975b). Perhaps the articu­ lated coralline algae produce a similar whiplash effect, although this is unlikely" Not only are they stiff and subject to the of water motion found in the intertidal zone, but if abrasion were important, one would not expect the common occurrence of epiphytic brown and red algae on Calliarthron tuberculosum. Another expl on for this low colonization is that the corraline mat may be a physi barrier to new recruits. Hruby and Norton (1979) found that a thi \ turf of Enteromorpha intestinalis significartly reduced the number algal spores reaching the underlying substratum. Whether the entangled frond::; of C. tuberculosum act as a similar barrier is not known. It was not investigated in this study. The importance of in structuring algal populations

been demonstrated for a number of marine communities, both. in i .·tidal (Paine and Vadas, 1969; Nicotri, 1977; Lubchenco, 1978, 1980;

lubchenco and Menge, 1978) and subtidal habitats (Breen and Mann~ 1976; Foreman, 1977; Ogden and Lobel, 1978; Duggins, 1980). Grazi however, appears to be unimportant at Stillwater Cove. The only or invertebrate grazers are sea hares (Aplysia californica), bat stars (Pati a miniata) and turban snails (Tegula spp.). Sea ins (Strongylocentrotus spp.), (Haliotis spp.) and p (Pugettia spp.), which are major herbivores in other lp forests

(Kitching and Ebling, 1961; ighton, 1966; Gerrard~ 1976; , 1 are rare in Stillwater Cove. The few sea urchins and abalone are restricted to cracks and crevices (pers. obs.), pro- bably feed mainly on drift plants (Lowry and Pearse, 1973). Other invertebrate grazers are not conspicuously abundant l vorous shes are absent. The low densities of sea urchins, abalone and kelp crabs illwater Cove may be attributed to the presence of the sea otter,

Enhydra lutris, whi has inhabited the cover since 1956 (Ebert,

1967). These grazers are primary food items of the sea otter in California (Ebert, 1968; Wild and Ames, 1974). A wide vari of evidence suggests that sea otters are important in structuring and maintai ng the nearshore algal comm~nities by limiting the densities

of herbivores (Estes and Palmisano, 1974; Estes, et ~., 1978). The re-establishment of sea otters in Stillwater Cove closely parall s the proposed age of the older Pterygophora californica stands. Per­

haps these dense stands developed after sea otters removed major herbivores. A diverse assemblage of less conspicuous invertebrates, some of which are grazers, inhabits the coralline mats (see Appendix l). Be- cause of the difficulties encountered in trying to remove these ani- mals from the coralline mats without altering the plants, their impact was not directly measured; however, the available evidence suggests that these small grazers have little effect compared to algal

titian for light. For e, there was substantial algal recrui ment on coralline mats in the Pterygophora removal site none in the Pterygophora control, but the invertebrates associ wi the coralline mats were undisturbed in both treatments. Previous observations of subtidal algal succession have marked seasonal differences in the species composi on nizing concrete blocks (Kains 1975; Foster, l975b). In this s seasonal recruitment was observed for the brown eshy red algal species, but the dominant ial Calliarthron tuberculosum settl on newly cleared surfaces at all times of the year. Growth of Calliarthron tuberculosum is relatively slow at a rate of approximately 2 em/year (Johansen and Austin~ 1970). Apparently. this slow growth has little effeft on the plants 1 survival, since it is not replaced by faster growing plants which colonize in the spri and outcompete it for light. Instead, growth of C. tuberculosum con­ tinues even at the low light levels experienced under the canopy the faster growing species. This shading probably effects tubercu- losum though, as higher·growth rates are observed in the winter (Johansen and Austin, 1970) when shading kelp canopies is a mum. In contrast to older plants which form dense mats and success- fully inhibit the colonization of other algae, younger, smaller indi­ viduals of Calliarthron tuberculosum. had little effect on the recruit- ment and growth of other species. For example, after fourteen months of regrowth following the removal of its upright cover in March l C. tuberculosum had little effect on springtime germination brown and fleshy red algae in 1980. Inhibitory effects by £. on other algae does not occur l approximately to years of age. It is at this time that the plants are la to pro­ duce a substantial cover which allows them effecti compete for light.

Continual removal of the dominant canopy species 1 a si i- ficant increase in ephemeral algal cover consisting primarily Desmarestia ligulata and, to a lesser extent, D. kurilensis, Nereo- ~ystis luetkeana and es red algae. Foster, et ~· (1979) found a si lar increase in D. ligulata lowing the natural removal of Macrocystis pYrifera canopy by storms. This opportunistic behavior Q. ligulata appears quite si lar to that observed in the kelp Alaria fistulosa found in sel otter dominated kelp forest at Amchitka Island, Alaska (Dayton, 1975a). Both D. ligulata and A. fistulosa seem to be poor competitors~ but rapidly colonize areas when the canopies of competitively domiriant kelps are removed. Moreover, foliose red algal understory behaves in much the same way, showing an increase in cover following the removal of canopy species (Dayton, l975a; Pearse and Hines, 1979; Foster, et !!}_., 1979). The low foliose red algal cover which resulted 1owing the re- moval of Pterygophora californica was probably due to a lo\AJ abunda.nce of spores in the cove, although experimental evidence for is was inconclusive. New recruits were only observeq growing near reproduc- tive plants. A dense foliose red algal understory is found approxi­ mately 150 m from the study site near an exposed wash rock located just outside the cove (Figure l), The mechanisms of gal spersal are poorly known, but results from this experiment and others on kel (Anderson and North, 1966; Dayton, 1972) suggest that the supply spores from sources outsi the cove was probably 1ow. ~1oreove r, the gh recruitment of kelps and coralline algae observed in the study area probably reflects a large supply of these spores found in cove. act in opposition to each other. Competition involves the inter- 26 actions within or between species for a common resource, and often leads to high abundances of a few competitively superior species (Connell, 196la, b; Dayton, 1971, Menge, 1972). On the other hand,

disturbance tends to incre~e the availability of a limiting resource, thereby reducing competition (Paine, 1966; Dayton and Hessler, 1972, Levin and Paine, 1974; Sousa, 1980). Depending on the intensity and \ frequency of the disturbance, a subsequent higher species diversity may result (Connell, 1978). The subtidal algal community at Still­ water Cove experiences very low levels of biological and physical dis­ turbance. The sheltered nature of the cove, combined with a hard and stable rock bottom, results in reduced water motion, low rates of sedimentation and relatively clear water throughout the year. More­ over, as a possible consequence of the re-establishment of sea otters, major densities are low and grazing pressures appear to be at a minimum. Under these conditions, perennial algal species are able to monopolize light and thus exclude other algae as well as inhibiting their own recruitment. In contrast, the giant kelp forests located 45-60 km north on a more wave-exposed coast experience higher and more frequent levels of

both biological and physical disturbance (Foster, et ~., 1979). These exposed forests also grow on a soft mudstone bottom, which is easily eroded by the high water motion experienced throughout much of the year. In addition, (Strongylocentrotus franciscanus) densities are relatively high, since the area is north of the present range of sea otters. As a result, grazing affects algal composition and abundance and may lead to a higher species richness (Cowen, 1979). 27 Under these conditions, survival of long-lived, slow-growing perennial species is low and the understory is characterized by a relatively

rich assemblage of rapidly-grow~ ephemeral species which flourish during periods of abundant light. These results indicate that experimentally-induced disturbances (i.e., selective canopy removals) allowed ephemeral algal species to \ invade the otherwise perennial algal assemblage at Stillwater Cove. The understory soon began to resemble that of nearby kelp forests, which are typified by high levels of disturbance. Only under condi­ tions of frequent disturbance might this ephemeral algal assemblage be maintained, particularly since the recruitment of slower-growing perennials was also high. Without their periodic removal, the compe­ titively dominant perennials became re-established, increasing compe­ tion for light and reducing chances for survival of other species. LITERATURE CITED

Abbott, I.A. and G.J. Hollenberg. 1976. Marine algae of California. Stanford Univ. Press, Stanford, CA. 827 pp. / Aleem, A.A. 1956. Quantitative underwater study of benthic com­ munities inhabiting kelp beds off California. Science 123:183. Anderson, E. and W.J. North. 1966. In situ studies of spore pro­ duction and dispersal in the giantke~~1acrocystis. Proc. Internat. Seaweed Symp. 5:73~86.

Barrales~ H.L. and C.S. Lobban. 1975. The comparative ecology of Macrocystis pyrifera th emphasis on the forests of Chubut, Argentina. J. Ecol. 63:657-677. Black, R. 1974. Some biological interactions affecting intertidal populations of the kelp laevigata. Mar. Biol. 28:1 198. Breen, P.A. and K.H. Mann. 1976. Destructive grazing of kelp by sea urchins in eastern Canada. J. Fish. Res. Bd. Can. 33:1278- 1283. Connell, J.H. 196la. The influence of interspecific competition and other factors on the distribution of barnacle Chthamalus ste 11 atus. Eco 1ogy 42:710-723. --...... --.-..-,· l961b. Effects of competition, by Thais lapillus and other factors on natural popul ons of the bar­ nacle Balanus balanoides. Ecol. Monogr. 31:61-104. 1978. Diversity in tropical rain forests and reefs. Science (199):1302-1310. Cowen, R.K. 1979. Trophic interactions thin a central California kelp forest. MS thesis, Calif. State Univ., Hayward. pp. Dawson, E.H., M. Neushul and R.D. Wildman. 1960. Seaweeds asso­ ciated with kelp beds along southern Californa and northwes Mexico. Pac. Nat. 1:1-81. Dayton, P.K. 1971. Competition, disturbance and communi organiza- tion: The provision and subsequent utili on of space in a rocky intertidal corrmunity. Ecol. ~1onogr. 41:351-389. 1972. Dispersion, dispersal and persistence annual intertidal alga, Postelsia Qalmaeformis ruprecht. Ecol 54(2) :433-438. 28 Dayton, P.K. 1975a. ExperimentaYstudies of algal canopy i actions in a sea-otter dominated kelp community at Amchitka Island, Alaska. h. Bull. :230-237.

. 1975b. Experimental evaluation of ecological dominance --....-;n-a-rocky intertida 1 alga 1 community. Ecol. Monogr. 45 (2): 137- 159.

--...... -~and R.R. Hessler. 1972. Role of biological disturbance in maintaining diversity in the deep sea. Deep-Sea Res. 19: 199-208. Divinny, J.S. 1978. Ordination of seaweed communities: Environ- mental gradients at Punta Bunda, Mexico. Bot. Mar. 363.

--.....,...... ,...,.,..-and P.D. Kirkwood. 1974. Algae associated with kelp of Monterey Peninsula, California. Bot. Mar. 17:100-1 Duggins, D.O. 1980. Kelp beds and sea otters: An experimental approach. Ecology 61(3):447-453. Ebert, E.E. 1967. Food habits of the southern sea otter Enhydra lutris nereis, and ecological aspects of their population and distributional expansion. Rept. to Calif. Dept. Fish and Game. MRO Ref. No. 67-18.~ --...... ,..____,.· 1968. A food habits study of the southern sea otter, Enhydra lutris nereis. Calif. Dept. Fish and Game 54:33-42. Estes, J.A. and J.F. Palmisano. 1974. Sea otters: Their role in structuring nearshore communities. Science 185:1058-1060. ---;-:---' N.S. Smith and J.F. Palmisano. 1978. Sea otter preda­ tion and community organization in the western eutian Islands, Alaska. Ecology 59:822-833. Foreman, R. 1977. Benthic community modification and recovery lowing intensive grazing by Strongylocentrotus droebachiensis. Helga. wiss Meeresunters 30:468-484. Foster, M.S. 1975a. Algal succession in a Macrocystis pyrifera forest. Mar. Biol. 32:31 329. --..----· l975b. Regulation of algal community development in a Macrocystis pYrifera forest. . Biol. 32:331-

--,...,.---=--' R. Cowen, C. Agegian, D. Rose, R. VanWagenen and A. Hurley. 1979. Continued studies of the effects of sea otter foraging on kelp forest communities in central California. Mimeo Rept. to Calif. Dept. Fish and Game, Sacramento. 1 30 Frye, T. 1918. The age of Pterygophora californica. Pub. Puget Sound Biol. Sta. '2:65-71. / Gerrard, V.A. 1976. Some aspects of material dynamics and energy flow in a kelp forest in Monterey Bay, California. Ph.D. dis­ sertation, Univ. of Calif., Santa Cruz. 173 pp. Goodall, D.W. 1952. Some considerations in the use of point quad­ rats for the analysis of vegetation. Aust. J. Sci. Res. Series B 5:1-41. Grieg-Smith, P. 1964. Quantative Plant Ecology, 2nd ed. Butterworth's, \ London. 256 pp. Harper, J.L. 1977. Population of Plants. Academic Press, N.Y. 892 pp. Hruby, T. and T.A. Norton. 1979. Algal colonization on rocky shores in the Firth of Clyde. J. Ecol. 67:65-77. Johansen, H.W. and L.F. Austin. 1970. Growth rates in the articu­ lated coralline Calliarthron (Rhodophyta). Can. J. Botany 48: 125-132. Jones, N.S. and J.M. Kain. 1967. Subtidal algal colonization follow­ ing the removal of Echinus. Helgo. wiss Meeresunters 30:468-484. Kain, J.M. 1963. Aspects of the biology of Laminaria hyperborea. II. Age, weight and length. J. Mar. Biol. Ass. U.K. 43:415-433. --..------.· 1966. The ro 1e of 1i ght in the eco 1ogy of Lamina ria hyperborea, pp. 319-333. ~: Bainbridge, R., G.C. Evans and 0. Rackham (eds.). Light as an Ecological Factor. Blackwell Scientific, Oxford. 1975. Algal recolonization of some cleared subtidal areas. J. Ecol. 63:739-765. Kitching, J.A., T.T. Macan and H.C. Gilson. 1934. Studies in sub­ littoral ecology. I. A submarine gully in Wembury Bay, South Devon. J. Mar. Biol. Ass. U.K. 19:677-705. --=----and P.J. Ebling. 1961. The ecology of Lough Ine. XI. The control of algae by Paracentrotus lividus (Echinodea). J. Anim. Ecol. 30:373-383. Kuhnemann, 0. 1970. Algunas consideraciones sabre los bosques de Macrocystis pyrifera. Physics xxix(70):273-296. Leighton, D.L. 1966. Studies in food preference in algivorous inver­ tebrates of southern California kelp beds. Pacific Science xx: 104-113. Leighton, D.L., L.G. Jones and W.J. North. 1966. Ecological relation­ ships between giant kelp and sea urchins in southern California~ pp. 139-140. In: Young, E.G. and J.L. Mclachlan (eds.). . 5th Int. Seaweed Symp. Pergamon Press, Inc., Oxford. Levin, S.A. and R.T. Paine. 1974. Dilturbance, patch formation and community structure. Proc. Nat. Acad. Sci. 71(7):2744-2747. Lowry, L.F. and J.S. Pearse. 1973. and sea urchins in an area inhabited by sea otters. ~1ar. Biol. 23:213-219. Lubchenco, J. 1978. Plant species diversity in a marine interti l community: Importance of herbivore food preference and algal competitive .abilities. Amer. Nat. 112:23-39. 1980. Algal zonation in the New England rocky i tidal community: An experimental analysis. Ecology 61(2):333- 344. --...... -and B.A. Menge. 1978. Community development and persis­ tence in a low rocky intertidal zone. Ecol. Monogr. 59:67-94. Mann, K.H. 1977. Destruction of kelp beds by sea urchins: A cycli­ cal phenomenon or irreversible degradation? Helga. ss Meere- sunters 30:455-467. · McLean, J.H. 1962. Subtidal ecology of kelp beds of open coast area near Carmel, California. Biol. Bull. Mar. Bi . Lab., Woods Hole 122:45-114. McPeak, R.H., H. Fastenau and D. Bishop. 1973. Observations and transplantation studies at Point Lorna and La Jolla. Kelp tat Improvement Project Ann. Rept. 181 pp. Menge, B.A. 1972. Foragi strategy a starfi in actual prey availability and environmental predi Ecol. Monogr. 42:25-50. 1, M. 1971. The kelp community of seaweeds. Nova Hedwigia 32: 265-267. --...... ,-.' W.O. Clark and D.W. Brown. 1967. dal plant animal communities of the southern California Islands. Symp. Biol. Calif. Isl., pp. 37-55. Ni • M.E. 1977. Grazing effects of four ne interti 1 i- vores on the microflora. Ecology 58:1020-1032.

Ogden, J.C., R.A. Brown and N. Sales . 1973. Grazing by the echinoid Diadema antillerum Phil ipi: Formation of halos around West Indian patch reefs. Science 182:715- 7. 32 Ogden, J.C. and P.S. Lobel. 1978. The role of herbivorous fishes and urchins in coral reef corrmunities. Env. Biol. Fish. 3(1):49-63. Paine, R.T. 1966. Food web complexity and species diversity. Amer. Nat. 100:65-75. ____. 1979. Disaster, catastr4he and local persistence of the sea palm Postelsia palmaeformis~ Science 205:285-287.

---::-:-- and R. L. Vadas . The effects of grazing by sea urch i. ns, Strongylocentrotus spp. on benthic algal populations. Limnol. \ and Oceanogr. 14:710-718. Pearse, J.S. and A.H. Hines. 1979. Expansion of a central California kelp forest following the mass mortality of sea urchins. Nar. Biol. 51:83-91. Rosenthal, R.J., W.O. Clark and P.K. Dayton. 1974. Ecology and natural history of a stand of giant kelp, Macrocystis pyrifera, off Del Mar, California. Fish. Bull. U.S. 72:670-684. Simpson, J. 1972. The geology of Carmel Bay, California. MS thesis, U.S. Naval Postgraduate School, Monterey, CA. 70 pp. Sokal, R.R. and F.J. Rohlf. 1969. Biometry. W.H. Freeman and Co., San Francisco. 776 pp. Sousa, W.P. 1980. The responses of a community to disturbance: The importance of successful age and species life history. Oecologia 45:72-81. Wild, P.W. and J.A. Ames. 1974. A report on the sea otter Enhydra lutris 1. in California. Calif. Dept. Fish and Game Mar. Res. Tech. Rept. 20:1-93. APPENDIX I

On 3 March 1979, four hapha~rdly chosen 1 m2 quadrats were cleared of the upright coralline bottom cover. The plant material (5 kg wet wt.) was removed with a paint scraper and placed in a nylon mesh bag. No suction device was employed to ensure the capture of all organisms occupying the coralline mats. The animals found in the \ cleared algae were sorted in the laboratory. Following is a list of invertebrate species found in the sorted algae. Abundances are given, when available.

Annelida Diopatra ornata Sa bell aria sp. Mollusca Alia carinata 7 Afiii?ilissa ·versicolor 4 Astrea gibberosa 7 Boreotrophon sp. 1 Calliostoma canaliculatum 1 Calliostoma sp. 6 Clathurel1a sp. 1 Crepidula adunca 17 Dendrochiton sp. 1 Diodora aspera 3 Fusinus luteopictus 8 Hinnites giganteus 2 Lacuna unifasciata 2 Lepidozona mertensii 1 Margarites sa1moneus 2 Nassarius mendicus 39 Ocenebra sp. 1 Pseudomelatoma torosa 6 Serpulorbis · sguamigerus 1 Tegula brunnea 5 Tegu1a montereyi 8 Trico1ia pu11oides 8

33 34 APPENDIX I (continued)

Arthropoda', Alpheus sp. Ampithoe sp. J Cryptolithodes·sitebergis Mimulus foliatus Pagurus spp. Pugettia richii

\ Echinodermata Cucumaria sp. Leptasterias sp. Ophioplocus esmarki Ophiothrix spiculata Strongylocentrotus purpuratus 16 Ectoprocta Crisia sp. Hippodiplosia insculpta Lagenipora punctulata Phidolopora pacifica Urochodata Styela montereyensis \

APPENDIX II Algal Transplant Experiment

In the fall of 1979, in an attempt to study differences in growth beneath and outside of the kelp canopies, a transplant experiment was initiated. Boulders containing substantial cover of the foliose red alga Gigartina corymbifera were transported into the study area and placed in the canopy removal and the canopy control sites. The boulders were secured by wedging them into truck tires fastened to the bottom with polypropylene line and rock-climbing pitons. Gigartina corymbifera is a common red alga found at similar depths outside the cove only 150 m from the study area. Transplanted algae, regardless of their location in the study site, suffered high mortality. Within three months, the cover of perennial G. corymbifera on the trans­ planted boulders, whether placed in the Pterygophora control or the Pterygophora removal site, was drastically reduced. Soon after trans­ plantation, young G. corymbifera were noticed on the boulders placed in the Pterygophora removal site. These young plants disappeared within two months. They did not appear to be grazed and reasons for their poor survival remain unknown.

35 \

36

FIGURE 1. Location of study site. \

N I Kilometer

•• 0. ·. :..:_..:.-. :.. :..::.: .. ~.. ·.. :::.-.. ·:.:StilI water Cove ... :::· ··.: . : . .

.;y• Exposed wash rock {:.··carmel ·;. -... ·. :·· . Carmel Bay ... .

California 38

FIGURE 2. Diagrammatic representation of the algal assemblage in the study site and the experimental manipulations which were performed. ~

Pterygophoro Pterygophora control removal

-~ P. californica

.IJll' cora I line control n=IO scrape to bare rock-tCjjf- upright coralline w n=IO removed 1.0 40

FIGURE 3. Initial algal percent cover in study site in May 1978 prior to experimental manipulation. Variation is given as standard error; n = 45 for Pterygophora control; n = 66 for Pterygophora removal; >1m= greater than 1m tall;< 1m= le~s than 1m tall. 41

Pterygophora Pterygophora Control Removal

Percent Cover Percent Cover 100 so 60-, 40 20 0 ' -, 0 20 40 60-, 80-, 100 Pterygophoro ca/ifornica'(,l m)

Pterygophora • coliforn ICO(

1-- , -f.- Bossie/la spp. 1--

- 1- Encrusting Cora II ines - f.-

~ Other species - 42

FIGURE 4. Algal percent cover in study si.te in February 1979, 270 days after Pterygophora californica removal. Variation is given as standard error; n = 20 in both areas. 43

Pterygophoro Pterygo phoro Control Removal

Percent Cover Percent Cover 100 80 60 40 20 0 «) -, ::t 0I 20 60I 80 100 Pterygophora californica ()I m) Pterygophora r- caltfornica (

- 1- Ca!liarthron spp_ -r-

,... ~ Bossie/la spp. I~ .... 1- Encrusting ~ Cora II ines

I" Other species '"-

Macrocystis pyrifera (:>I m)

Macrocystis -r- pyrifera (<1m)

1- Desmarestia 1- ligu/ata 1- 44

FIGURE 5. Understory algal percent cover in March 1979 prior to initiation of coralline understory treatments. Epi­ phytic red algae include Botryoglossum farlowianum s~.p. farl owi anum, Laurenci a suboppos itta and Pl ocami urn cartilagineum. Upright coralline algae other than · Calliarthron tuberculosum comprise 11 other species 11 category. Variation is given as standard error; n = 10 for each treatment. 45

Pterygophoro Pterygopho ro Control Removal

Percent Cover Percent Cover 100 80 60 40 20 0 0 20 40 60 80 100

Epiphytic red algae on C tuberculosum

Encrusting CoraJJjnes

Other species

~ Cora II ine control 0 Upright Coralline removal E;S Scrape to bare rock 46

FIGURE 6. Percent cover of algal understory in July .1979, 130 days after establishment of coralline understory treatments and with removal of Pterygophora californica and Macrocystis pYrifera recruits. Epiphytic red algae in­ clude.Botryoglossumfarlowianum ssp. farlowianum, Laurencia suboppositta and Plocamium cartilageneum. Upright coralline algae other than Calliarthron tubercu­ losum comprise 11 0ther species 11 category. Variation is . given as standard error; n = 10 for each treatment. Pterygophora Pterygophora47 Control Removal Percent Cover Percent Cover 100 80 60 40 20 0 0 20 40 60 80 100 I I

Epiphytic red algae on C. tuberculosum

.,...-:;~~IIQQ~~~~ En c rusting Corallines

Other species ) .

Bare rock

Desmorestio liguloto

Desmorestio kuri/ensis

Nererocystis luetkeono

Fleshy red algae

~ Coralline control 0 Upright Coralline removal ~ Scrape to bare rock \

48

FIGURE 7. Light measurements recorded at mi·n'imum {March) and maximum {July) kelp canopy development. All measure­ ments were taken at 15 m depth. Variation is ex­ pressed as standard deviation; n = 4. 49 6 :E 0 1- 55 m

(!) ~ 4 J: 0 <[ LLI a:: 3 .... :I: (!) ..J- 2 LLI ) 0 ~ ~I (/)

MAR.'79 JUL.'79 MAR.'SO JUL.'SO

0 Under no kelp canopy ~ Under Pterygophora only ~ Under combined /L1acrocystis Under Macrocystis only and Pterygophora II 50

FIGURE 8. Percent cover of Desmarestia ligulata in Pterygophora removal site. · Desmarestia liqulata was cleared from the quadrats _of all treatments in, March 1979, and in cora 11 i ne contra 1 and cora 11 i ne remova 1 quadrats in August 1979. rt was ·absent on __quadrats scraped to ) bare rock at the time of the summer clearing, and in quadrats of all three coralline understory treatments cleared in November 1979. +indicates time which Q ligulata was removed. Variation is given as standard error; n = 10 for data taken in February and July 1979; n = 5 for all others. 51 Oesmarestia ligu/oto I 100 ~ I 80 I \ I 1 I I I 60 I I

40 ,'.A Coralline 20 Control a:: 0 w 100 6 80 (.) 60 I-z 40 Upright 20 Cora II ine ) w (.) Removal a:: 0 ~100 80 60 40 Scrape 20 To Bare 0 ~--~~~~~~~~~~-Rock++ FEB JUL NOV FEB JUL ·79 79 79 eo eo • • Winter clearing o----a Summer clearing D.--6 Fall clearing 52

FIGURE 9. Percent cover of Desmarestia kurilensis in Pterygophora removal site. Desmarestia kurilt'msis was absent in every treatment at the time of all three clearing dates. Varia­ tion is given as standard error; n = 10 for data taken in February 1979 and July 1979; n = 5 for all others. ) 53 50 Oesmarestia kurilensis 40 30 Coralline 20 /9 Control 10 / /?' ' / ' 0 ' 0::50 ~40 "' 83o Upright · ,_20 Coralline z 10 w Removal c::(.) 0 UJ 50 0.. 40 30 Scrape 20 To Bare 10 Rock 0 FEB JUL NOV FEB JUL 79 79 79 80. 80

• • Winter clearing c---c Summer clearing t::.· • • ·D. Fa I I c I e a r i n g 54

FIGURE 10., Percent cover of Calliarthron tuberculosum in Pterygophora removal and Pterygophora control sites. In the Ptery­ gophora control site, quadrats were cleared in winter 1979 only. Quadrats in the Pterygophora removal site were cleared in winter 1979, summer 1979 and fall 1979. No ) clearing of coralline algae was performed in any coral­ line control quadrats. Pterygophora removal quadrats scraped to bare rock were not recleared in summer 1979, as cover was low. · +indicates time coralline algae was cleared. Variation is given as standard error; n = 10 for data taken in Feb­ ruary and July 1979 and in all Pterygophora control quad­ rats; n = 5 for all others. 55 100 Co!/iorthron tubercu/osum ~¢r~·~;.~~~·····~ 80 ' // L -j ,, t.:--""¢' / ....-··1 .. -··1'·., 60 -··-r·· '+ 40 Coralline 20 Control o~--~--~~~~--~-- ffi 100 80 6 ~ • u 60 • ~ 40 I Upright W 20 \ Coralline ) ~ O~-.e.:~~-~.;;.....,r------r- Removal ++ ~ 100 80 1

60 ~I 40 1 Scrape I 20 To Bare Rock o~~~~~~~~~~--++ + FEB JUL NOV FEB JUL 79 79 79 80 80 ...... Pterygophoro Control I Winter Clearing 0--o Pterygophora Removal /Winter Clearing o---c Pterygophoro Removal I Summer Clearing er-"t::. Pterygophoro Removal I Fall Clearing "' '------'

TABLE 1: Percent cover of non-calcified algae in the Pterygophora removal site following spring germina­ tion in 1979 and 1980. In both years, new Macrocystis pyrifera and Pterygophora californica were continually removed. Individuals were not sampled both years, as no plants persisted longer than ten months. X signifies presence of a flesh red algal species. Variation is ex­ pressed as standard error.

July 1979 (n = 10) July 1980 (n = 5) !Upright Upright Coralline Coralline Scrape Coralline Coralline Scrape Control Removal To Rock Control Removal To Rock

Oesmarestia ligulata 82.2 ± 9.2 94.0 ± 2.96 1.1 ± .99 96.0 ± 3.99 94.0 ± 4.85 36.0 ± 16.0 Desmarestia kurilensis 8.3 ± 4.6 10.5 ± 3.53 1.1 ± .99 34.0 ± 6.96 12.0 ± 3.51 80 ± 5.83 Nereocystis luetkeana 20 ± 13.5 Fleshy red algae {all species combined) 1.22 ± .53 3.0 ± 2.0 3.0 ± 2.13 1.0 ± 1.0 3.0 ± 1.0 4.0 ± 3.99 Bonnemaisonia nootkana X X X X Callophyllis flabellulata X X X faucia laciniata X X X X Fryeella gardneri X X X Gigartina corymbifera X X Neoptilota densa X Pikea robusta X Weeksia reticulata X X X

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