REPRODUCTIVE PERIODICITY AND ITS RELATIONSHIP

TO RECRUITMENT AND PERSISTENCE OF

Endocladia muricata and papillatus

A Thesis

Presented to

The Faculty of the Department of

Moss Landing Marine Laboratories

San Jose State University

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

By

Eric Walter Nigg

June 1988 Ill TABLE OF CONTENTS

Page

LIST OF TABLES ...... iv

LIST OF FIGURES ...... v

ABSTRACT ...... vi

INTRODUCTION ...... 1

The Plants ...... 5

SITE DESCRIPTIONS ...... 6

METHODS ...... 8

Phenology ...... 8

Seasonal Variations in Cover and Recruitment...... 9

RESULTS ...... 11

Phenology ...... 11

Seasonal Cover ...... 12

Recruitment ...... 12

DISCUSSION ...... 14

ACKNOWLEDGEMENTS ...... 21

LITERATURE CITED ...... 22

TABLES ...... 26

FIGURES ...... 31 IV

OF TABLES

Page

1. Correlation of cystocarpicity and latitude ...... 26

2. Seasonal variation in plant cover ...... 27

3. Comparison of cover of muricata and M. papillatus in plots cleared

during spring and fall ...... 28

4 Persistence of original colonizers in spring-cleared plots ...... 29

5. Persistence of original colonizers in fall-cleared plots ...... 30 v

LIST FIGURES

Page

1a. Habit and life history of muricata ...... 31

1b. Habit and life history of M. papillatus ...... 32

2. Map showing locations of study sites ...... 33

3. Diagram of experimental clearings ...... 34

4. Cystocarpicity of E. muricata at each site through time ...... 35

5. Cystocarpicity of M. papillatus at each site through time ...... 36 Vl

ABSTRACT

Simultaneous studies of phenology and recruitment of marine algae have rarely been done, despite the apparent importance of both to community development. The reproductive periodicity of two species of intertidal marine algae was observed bimonthly at five sites along the coast of central and northern for one year.

Endocladia muricata had a peak in presence of cystocarps in July 1985, while

Mastocarpus papillatus peaked in September of 1985. These peaks coincided with· maxima in cover. Presence of cystocarps positively correlated with increasing latitude for both species during peak months. The patterns of recruitment into experimental clearings made in spring and fall of 1985 reflected each species' phenology - i.e.

Endocladia recruitment was highest in spring clearings while Mastocarpus recruitment was highest in fall clearings- and persisted for up to 30 months after clearing. These results suggest that community development is partly governed by the phenology of organisms and the time of year at which space for recruitment is made available.

Moreover, these early patterns may persist. affecting community structure and diversity. 1

UCTION

Physical disturbances in rocky intertidal areas make space available for colonization by algae and sessile animals. Following a disturbance, the composition of marine algal assemblages may be determined partly by the time at which the space was made available (Foster, 1975; Connell, 1978; Sousa, 1979a). There is increasing evidence that plants of either fast-growing annual or slow-growing perennial species are equally capable of colonization and growth on newly cleared substrata (Northcraft,

1946; Foster, 1975, 1982; Sousa, 1979a). The sera! stages of these clearings will depend in part on how frequent and intense disturbances are, and when they occur relative to the reproductive cycles of the local algal populations. Theoretically then, at any given time a community may reflect the disturbance regime, timing of recruitment of organisms, and other successional processes that have affected it (Dethier, 1984).

The size, intensity and frequency of disturbances partly govern the composition of a community by controlling successional processes (Dayton, 1971; Levin and

Paine, 1974; Connell and Slatyer, 1977; Connell, 1978; Sousa, 1979a; Paine and

Levin, 1981 ). These factors vary seasonally and geographically. Connell (1978) has suggested that communities affected by intermediate levels of these factors show the highest species diversity. As these levels become extreme in either direction, diversity decreases and apparent dominance increases.

The intensity of disturbances is of particular interest in studies of succession from clearings. If, for example, a disturbance does not remove all parts of a plant, or leaves already settled spores or microscopic "alternate" stages, then development of the community will not necessarily reflect when succession began. Regeneration and growth from pre-disturbance plants and propagules will affect and perhaps dominate 2

the outcome. In fact, primary substratum for new recruitment may never be relinquished in partial clearings. Artifacts associated with this factor must be considered carefully when examining the results of experimental clearings (Dayton, 1975; Lubchenco, 1980;

Foster and Sousa, 1985; Hill,unpub. master's thesis; De Vogelaere, unpublished data).

Phenology (reproductive periodicity) and yearly fluctuations in fecundity, factors that are characteristic of the plants themselves, are of obvious importance to successful algal colonization and, hence, to community development (Northcraft, 1946;

Foster, 1975; Connell, 1978; Emerson and Zedler, 1978; Sousa, 1979a) yet they remain largely unstudied. While many annual (ephemeral) species may recruit throughout the year, perennials may have a distinct seasonality to recruitment (Emerson and Zedler,

1978; Sousa, 1979a; Gunnill, 1980a,b). Observations by Northcraft (1946) on a rocky shore in central California indicated that different species of algae became numerically dominant depending on when in the year space was made available for settlement.

Foster (1975), Sousa (1979a),and Emerson and Zedler (1978) obtained similar results in the subtidal, an intertidal boulder field, and in tidal pools, respectively. These studies indicate the importance of the timing of a disturbance relative to temporal recruitment patterns of different species of algae, but only Northcraft ( 1946) reported the seasonal reproductive status of algae at his study site. Paine (1979) stated that Postelsia (an annual) became sexually competent by midsummer. Gunnill ( 1980a,b) reported apparent peaks in recruitment for seven species of intertidal algae. He also observed annual recruitment fluctuations, but these were based on successful recruitment events which are affected by a number of different factors and, therefore, do not give accurate estimates of phenology. Norall, et al (1981) found that only one of four subtidal species that they studied had a "seasonal" peak in reproduction, but three of four varied in reproductive capacity along a depth gradient. 3

Physical variations associated with latitude are apparently responsible for setting limits on the ranges of many algal species (Abbott and North, 1972; Thom,

1980). The manner of propagation of plants and the abundance of grazers in the intertidal zone may also vary with latitude (Sousa, et al, 1981 ). Growth rates and fecundity of marine organisms may well be associated with these latitudinal variations as they are with physical variations associated with tidal height (for algae-Castenholz,

1963; Foster, 1982; for mussels-Harger and Landenberger, 1971; Suchanek, 1981) and depth of subtidal habitats (No rail, et at, 1981 ). The effects of this variation on plants within these range limits have not previously been addressed.

A plant's dispersal ability is an important factor in colonization following a disturbance. While most green (Chlorophyta) and brown (Phaeophyta) algae have motile propagules at some stage of their life histories, the (Rhodophyta) have no motile cells. Red algal spores, thus, cannot show any substratum preference, - though substratum characteristics have been demonstrated to be an important factor for survival (Hartog, 1959, 1972; Nienhuis, 1969; Harlin and Lindbergh, 1977; Lubchenco,

1983). Dispersal distances for red algal spores have not been experimentally determined as for $Ome species of green (Amsler and Searles, 1980) and

(Anderson and North, 1966; Dayton, 1973; Paine, 1979; Deysher and Norton, 1982).

These spores tend to be negatively buoyant (Coon, et al, 1972) and have been observed associated almost exclusively with the substratum rather than the water column (Amsler and Searles, 1980). Hoffman and Ugarte (1985), working in intertidal communities, found spores of what they called "late-successional" species (mostly perennial red algae) to be less abundant and more patchy in their distribution than so called "opportunistic" species. Undoubtedly these plants are limited in their ability to disperse and, therefore, to colonize open space. 4

Following settlement in the intertidal zone, propagules are subject to a variety of

physical and biological factors that affect survival and growth. Water motion {Charters,

et al, 1972) and desiccation during low tides {Connell, 1978; Schonbeck and

Norton, 1978, 1980) can cause mortality with the apparent result of a local failure of

recruitment. Grazing can have a similar effect, governing succession and ultimately controlling community development {Lubchenco, 1978, 1983; Robles, 1982; Robles and

Cubit, 1981; Petraitis, 1987).

Given the successful recruitment and growth of plants, the succession and structure of the community will be determined in part by the persistence of perennial species. Any early ability of a plant to pre-empt space and, perhaps, outcompete other plants by interference is dependent on the early species' ability to hold that space against the later species' incursions {Sousa, 1979b). If early colonizers have the ability to persist and spread vegetatively into surrounding areas, it will increase their likelihood of survival. This extends to the reproductive capacity of plants after they

settle into clearings. Plants that reproduce early in life will tend to increase in

abundance by colonizing openings that either have not been filled, or that arise

periodically in the immediate vicinity, while plants that spend years growing vegetatively risk death before reproduction.

This study examines the phenology of two species of intertidal marine algae,

Endocladia muricata and Mastocarpus papillatus, especially when the plants become

cystocarpic and when they recruit. Plant cystocarpicity (the relative abundance of

cystocarpic plants) was sampled for one year at five sites along the coast of central and

northern California. The cover of these plants was also measured in relatively

undisturbed quadrats at six sites for one year and was compared between seasons.

Recruitment patterns of both species into plots cleared during two seasons (spring and 5 fall ) were measured and compared at each of six sites. The questions addressed were:

1. Was the relative abundance of cystocarpic plants constant through the

year and with respect to latitude?

2. If there were peaks in reproduction, were they at the same time of year for

both species?

3. Did the cover of each species vary significantly between seasons?

4. Was the recruitment of each species dependent upon the time of year space

was made available for settlement?

5. If recruitment was "season" dependent, did later abundance correlate with initial

recruitment?

Additionally, qualitative observations were made on the dispersal ability and age of first reproduction for both species.

The Plants

Endocladia muricata (Figure i a.) occurs in dense stands in mid to high intertidal regions along the west coast of North America between and Punto Santo

Tomas, Baja California (Abbott and Hollenberg, i 976). The plant (hereafter referred to as muricata) is generally dioecious, but can be monoecious (Turner, et al, i 983;

Nigg, personal observation). It has isomorphic life history stages, and cystocarpic and tetrasporic plants may produce spores simultaneously (D. Woodward, personal communication). Its perennial turfy habit provides habitat for a diverse assemblage of organisms (Glynn, 1965; Sousa, i 984; Nigg, personal observation). 6

Mastocarpus papillatus (= Gigartina papillata, Guiry, et al, 1984) (Figure 1b.) may occur in dense stands in mid to high intertidal regions from Alaska to Punta Baja,

Baja California, and is "probably the most common red alga on the pacific coast"

(Abbott and Hollenberg, 1976). This species (hereafter referred to as M. papillatus) is dioecious and has heteromorphic life history stages, alternating between the foliose and the crustose ("Petrocelis") sporophytic phases. Observations of the life-history of this plant have demonstrated that some plants produce gametophytes from carpospores, thus skipping the crustose sporophytic phase (Polanshek and West,

1977; Guiry and West, 1983; Ohno et al, 1982; Masuda et at, 1984; Zupan, in prep.).

The plants are perennial, though the blades may die back in winter.

SITE DESCRIPTIONS

The study sites were chosen to represent similar assemblages of organisms, with E. muricata and M. papilfatus as two of their principal members. Locations of sites extend along the coast of central and northern California from San Luis Obispo County to Mendocino County, inclusive - a latitudinal range of approximately 5.4 degrees

(Figure 2). All of the assemblages except Pescadero Rocks are on fairly flat benches with very little slope.

Diablo Canyon (DC) 34.228" N. The site is approximately 1km north of the power

plant operated by Pacific Gas and Electric Co. in San Luis Obispo County, and is used

by them as a control area for comparison to areas potentially affected by the power plant. The limestone substratum is irregular, with small, cobble-filled channels 7

surrounding many of the plots. Plant diversity is high and both E. muricata and M. papillatus are fairly abundant.

Pt Sierra Nevada (PSN) - 35.728. N. Entrance to the site is approximately 8 km north of the Coast Guard lighthouse at Point. Piedras Blancas in San Luis Obispo

County. The limestone substratum is flat with small-scale irregularities. Plant diversity and cover are fairly high with both muricata and M. papillatus abundant.

Pescadero Rocks (PR) - 36.570" N. The site is in the northern end of Carmel Bay in

Monterey county. Clearings were made on the seaward side of an island 100m offshore of Pebble Beach. The substratum is of a course conglomerate in a limestone matrix and slopes approximately 30 degrees from the horizontal. Phenological surveys were done on this and another island 30 m to the south, as well as on Arrowhead point approximately 100 m further south. Plant cover is predominantly of E. muricata , but M. papillatus is present.

Bolinas (Sol)- 37.928. N. The site is in Marin County on a reef approximately 100 m from the cliffs, between "RCA Beach" to the north and Agate Beach to the south. The substratum is flat in general, but slanted bedding of the mudstone and limestone results in repetitions of intertidal elevations and, therefore, assemblages in widely separated bands progressing seaward. Plant cover is diverse, but is dominated by M. papillatus with very little E. muricata.

Sea Ranch (SR)- 38.750. N. The site is off Leeward Rd. in the Sea Ranch Colony, on

Highway 1, in Sonoma County. The substratum is of a fine sandstone with angular 8

bedding, causing some vertical relief. Aside from this, most of the area is relatively flat and at the same elevation. Plant cover is quite diverse, with fairly high cover of both E. muricata and M. papillatus.

Kibesillah Hill (KH) - 39.602" N. The entrance to the site is at a turnout at northbound mile 74.5 on Highway 1 in Mendocino County. The substratum is a coarse sandstone and varies in slope up to approximately 10-degrees from the horizontal. Plant cover is quite diverse, with high cover of both E. muricata and M. papillatus as well as a variety of fucoids.

METHODS

Phenology

The five northern sites were sampled for phenological patterns bimonthly between May 1985 and May 1986 inclusive. No transects for phenology were made at

Diablo Canyon due to logistical complications. All sites were sampled as close together temporally as tide and weather permitted. Generally this was over a one-week period (Pescadero Rocks was sampled in February of 1986, four weeks following the sampling of the first site in the series, due to intense winter storms).

At each site and time, 30 m transects with twenty-five random points were made through the E. muricata- M. papillatus assemblage in three well separated (>30m) areas. While the origins of the transects and the actual random points on the line changed between times, the areas that the transects sampled were the same.

Both species were sampled at each point on the transect. M. papillatus was sampled by haphazardly choosing a blade (or "ramet", sensu Harper, 1977) of a female 9

female plant at each point and squashing some of the papillae to check for carpospores. The proportion of cystocarpic plants relative to the total number of plants per transect {25) was calculated for each transect. Three of these transects were made at each site and time, giving a sample size of N=3. muricata is highly branched and tends to have cystocarps distributed sparsely among the branches. More branches were sampled for this species so that a meaningful proportion of cystocarpic plants could be calculated. This was done by using a 10 point, random point quadrat (RPQ) at each of the 25 transect points. This RPQ consisted of a 35 em long bar with a single 55 em long knotted string attached at both ends. At each point , the string at each knot was stretched away from the bar to its limit, and the branch closest to the knot was chosen.

Five knots were stretched to each side of the bar, generating a total of ten "random" points. Substratum irregularities made each point distance unique and so, each sample point unbiased. The same individual was not sampled more than once. Given that each of these RPQ's was chosen independently at random, and that a proportion of cystocarpic plants per total plants could be calculated, the sample size for E. muricata at each site and time was N=75.

Means and standard errors of cystocarpicity were calculated for each site and time using the appropriate sample size for each species. Sites and times were then compared graphically. For each species, data for the two months with the highest proportion of cystocarpic plants were combined at each site and compared by

Spearman's Rank Correlation (Sokal and Rohlf, 1969) along the latitudinal gradient.

Seasonal Variations in Cover, and Recruitment

As part of a larger study of community recovery, three 1x2 m plots were cleared at each site in each of two seasons (Aprii-May=spring; October-November=fall}. The 10 plots were randomly located within the E. muricata - M. papillatus assemblage.

Following the manual removal of all organisms from the rock the plots were sterilized by burning with a propane weed burner, until the rocks were too hot to touch, on three

successive low tides. This ensured that all incoming sessile organisms would be new

recruits. The substratum was not appreciably changed by this method of clearing and

sterilization.

Sampling of the plots at all sites was done quarterly for the first year following

initial clearing in each season, and semi-annually thereafter. Within the 1 x 2 m area of

each plot, only the center area of 0.5 x 1.5 m was sampled, leaving a 25 em border

around the outside of the plot (Figure 3). This was to account for potential edge effects

associated with grazers and storms (Paine and Levin, 1981; Sousa, 1984). This inner

area was divided into twelve quadrats, 25 em on a side. At each time, three of these

quadrats were chosen at random (but in combinations that would minimize repetitive

measures through time) and were sampled for percent cover of algae and sessile

invertebrates using a 20 point RPQ. This RPQ was a square grid of 64 holes in a 625

cm2 piece of plexiglass on legs that positioned it parallel to the substratum. New holes were chosen, 20 at a time at random, for each sampling period. A 3 mm rod with an

"infinitely small" point was extended through each hole to the substratum and the species of organism(s) contacted by the point was recorded. Each point in this device accounts for 5% of the total sample but, because of layering of plants, having more than 100% cover of organisms is possible

Four undisturbed "control" plots were established at each site and were sampled for seasonal variations in percent-cover of plants and sessile animals. They were sampled quarterly for one year (in each of four "seasons"), and three at a time on a

rotating basis. The fourth plot was a contingency for the potential loss of a control in this 1 1

long-term study. The mean, standard error, and measures of skewness and kurtosis of

muricata and M. papillatus cover in each control were calculated for each season.

Variances were compared with an Fmax test. and "seasons" were compared by ANOVA with all control plots at all sites combined (N=18), followed by a Fisher's LSD ("Least

Significant Difference") multiple comparison (Sakal and Rohlf, 1969).

For recruitment studies, experimental plots in which at least two of the quadrats had some cover of E. muricata or M. papillatus from RPQ data were included in the analysis. Plots cleared within a season were treated as a group. The difference in total number of points occupied by each species within a plot was subjected to a paired t-test

(Sakal and Rohlf, 1969). These comparisons were made at six-month intervals.

All statistical analyses were done at the level of a. =0.05 or less.

RESULTS

Phenology

The proportion of plants with cystocarps (cystocarpicity) varied through the year for both species,and the peak for each species occurred at different times of the year.

Consequently, their minima occurred at different times as well. E. muricata had its maximum abundance of cystocarps (30.4%) in late July of 1985 and its minimum {0%) in late November of 1985 (Figure 4).

M. papillatus peaked (100%) in late September of 1985 and had its minimum

(4%) in late May 1985 {Figure 5). Kibesillah Hill was not sampled in July 1985.

The presence of cystocarps during peak periods varied with latitude (Figure

4a,b). Combining the data for May 1985, July 1985 and May 1986 at each site, there was a significant correlation (r=0.631; P=0.001; N=42) between the mean abundance of 12

cystocarps on E. muricata and latitude (Table 1). Combining the data for September and November of 1985 at each site, there was a significant correlation (r=0.564;

0.002>p>0.001; N=30) between the mean abundance of cystocarps on M. papillatus and latitude (Table 1).

Seasonal Cover

Cover of both E. muricata and M. papillatus in control plots, combined over all sites, varied through four sample periods from March 1985 through January 1986

(Table 2). These data were normally distributed with respect to skewness and kurtosis, and the variances of the most extreme groups were not significantly different (Fmax=

1.70 for E. muricata and 1.85 forM. papillatus ). E. muricata cover (ANOVA, p=0.0001) was highest in summer (61.5%) and lowest in fall (37.5%), but only spring and summer were significantly different from fall. M. papillatus cover (AN OVA, P= 0.042) was highest in fall (30.9%) and lowest in spring (19.1 %}.

Recruitment

The relative abundance of recruits of E. muricata and M. papillatus differed depending on the season in which the plots were cleared (Table 3). One year after clearing (-April 1986), spring-cleared plots had significantly greater cover of E. muricata than of M. papillatus ( t=3.12; P=0.0087; N=13 plots), and fall-cleared plots had significantly greater cover of M. papillatus than of E. muricata (t=2.84; p=0.016; N=12

plots ) one year after clearing (-October 1986). The cover of E. muricata increased

steadily through time in spring plots, until at 30 months there was a slight decline (from

30.3% to 26.3%). M. papillatus cover varied with time (Table 3). 1 3

This pattern of recruitment related abundance did not persist eighteen months after clearing (Spring, t=0.29, p=0.77; Fall, t=1.47, p=0.16 ), although it re-emerged after twenty-four months (Spring, t=2.15, P=0.048 ; Fall, t=3.36, P=0.0037). The re- establishment of dominance by muricata in spring clearings during springtime sampling resulted from an overall decrease in M. papillatus cover, as well as an increase in E. muricata cover (Table 3).

The number of plots (of 18 total for each season) colonized by one or both species increased steadily through time. One year after the clearing of each type of plot, 13 (72%) spring and 12 (67%) fall plots had been colonized. Eighteen months after clearing, 15 (83%) spring and 17 (94%) fall plots had been colonized. Twenty-four months after clearing, 17 spring and 18 (1 00%) fall plots had been colonized (Table 3)

These patterns have persisted qualitatively in most plots over the course of the study (Table 3). After 30 months, E. muricata cover was higher than that of M. papillatus in 12118 (67%) of the spring-cleared plots; the remainder were covered more by M. papillatus. At the same time, 24 months following disturbance, 13/18 (72%) of the fall-cleared plots had higher cover of M. papillatus than of E. muricata ; the remainder were about equally covered by the two species.

Moreover, the plots that were predominantly colonized by one of the species within the first twelve months tended to retain higher cover of that species after 24 months. Of the 13 spring disturbances that had significant cover of E. muricata or M. papillatus after 12 months, 11 of them (85%) had higher cover of the initial colonizer after 24 months.(Table 4) Similarly, of the 13 fall disturbances with significant cover of

E. muricata or M. papillatus after 12 months, 12 of them (92%) had higher cover of the initial colonizer after 24 months (Table 5). 14

New recruits of each species became reproductive during the first year following settlement. Some muricata recruits produced cystocarps in most spring-cleared plots during spring and summer of 1986. Some M. papillatus recruits produced cystocarps in most fall cleared plots during fall and winter of 1986-87.

Dispersal of propagules occurred over distances of at least 50 em. Most plots had both species immediately adjacent to the borders and so half the width of the plot is the least distance over which the spores must have traveled to settle into the center of the plot. At Bolinas, E. muricata cover was very low adjacent to the cleared plots, and its cover in the cleared plots was very low. In contrast, the cover of this species was high in an area approximately 7-meters seaward, and recruitment was high in plots cleared in this area (Nigg, personal observation).

DISCUSSION

E. muricata and M. papil/atus had yearly peaks in the proportion of plants bearing cystocarps. These maxima were separated in time by 2 months at each site, with E. muricata peaking earlier in the year than M. papillatus . The actual abundances are not comparable between species since no measure of cystocarps or spores per unit area was established. Cover of the two species also varied through the year, with peaks in abundance that coincided with highest cystocarpicity.

Gunnill (1980a,b) reported spring and summer recruitment maxima for seven species of intertidal (mostly brown) algae, based on the appearance of very small plants (implying that these juveniles were observed soon after actual recruitment}. No species were predominantly fall recruiters, though Pelvetia fastigiata did show a secondary peak in December. He inferred that, because of the effects of desiccation 15

and winter storms (in the fall and winter respectively) spring and summer seasonality was "adaptive" to these plants. Ojeda and Santelices (1984) reported recruitment of

Lessonia nigrescens in the austral winter, but this may not have been the peak of annual recruitment since they never attempted observations of potential recruitment at other times of the year. The phenology of E. muricata, then, corresponded to the common pattern of spring-summer recruitment while M. papillatus tended to be later, perhaps responding to a different set of factors than many algal species (Gunnill,

1980b).

The relationship between cystocarpicity and latitude is most likely a reflection of physical factors that covary. Water temperature decreases, while summer daylength, winter storm intensity and wave height, degree of cloud cover and precipitation all increase at higher latitudes . The importance to community structure and recovery is that more spores were apparently available to plots in the north than in the south. If the same factors that were responsible for increased cystocarpicity ameliorated the environment for survival of the propagules, the cover of new recruits in the plots should also have been associated with latitude. In this study, however, there was no correlation between recruitment or recovery and latitude. This may have been due to site-specific differences in such factors as substratum type or heterogeneity, grazer densities, wave shock or local atmospheric anomalies. In spite of these differences, while not as strong for M. papillatus as for E. muricata, there does appear to have been an underlying biological response to some physical factor that varies with latitude.

Most disturbances occur during winter (Paine and Levin, 1981 ). The timing of the experimental disturbances in this study coincided with the ends of the temporal range of what Paine and Levin considered the disturbance season. Therefore, the timing of our clearings and their recruitment patterns are probably relevant to natural 1 6 disturbances. Sousa (i 984) made clearings within the geographic range of this study in July of one year and found a mixture of the two species settling within the same clearings. This follows if, as in this study, both species were cystocarpic in July at the time of disturbance. I would predict that disturbances in mid to late winter would be populated by E muricata since it would be the first species of the two with available carpospores. However, Northcraft (1946) made clearings on the Monterey Bay in four seasons and found no recruitment of E muricata in any of them after 24 months.

Moreover, he did observe M. papillatus recruitment in areas cleared in January.

Unfortunately, there are no data on the abundance of the two species adjacent to

Northcraft's plots. The fact that E muricata never recruited into any of them suggests some non-phenological factor.

The quality of the experimental clearings as compared to those found in nature is difficult to assess. The average size of clearings in nature is quite variable (0.03 - 1.3 m2 , in mussel beds; Sousa, 1984) but are generally smaller than ours were. This would tend to reduce grazing effects near the center of the clearings, possibly affecting the outcome of recovery processes, but not of dispersal or persistence. The manner of clearing, while not changing substratum characteristics directly, is unusual because the clearings were sterilized. More often in nature, remnants of pre-disturbance organisms are present, some of which may propagate vegetatively and recolonize without need of reproducing. Our clearings resembled disturbances caused by natural rock shear, which occurs to some extent all along the coast, and which was quite common at

Bolinas during this study.

The above assumes that these patterns of "seasonality" are recurrent from year to year. The fact that peak cystocarpicity coincided with peak cover for each species suggests they are if, again, the latter is a recurrent feature of these two species. The 1 7

quarterly sampling of cover in undisturbed plots was not sufficient to establish seasonality. However, long-term data from the monitoring program at Diablo Canyon

Nuclear Power Plant (PG&E, 1984) show the maxima in cover of these two species to be similar to this study, with E. muricata peaking in summer and M. papillatus peaking in fall. Moreover, this pattern was repeated for eight years.

Another assumption is that my measure of cystocarpicity corresponds to actual release of carpospores. The only support I have for this is qualitative. E. muricata was observed with cystocarps at various stages of development; from incipient bumps on the thallus, to large spheres containing carpospores, to empty cystocarps. All of these

"stages" became more abundant during the height of cystocarpicity. M. papillatus cystocarps developed ("ripened") over time so that in fall they were soft and practically oozing spores.

A curious aspect of the resulting recruitment was the colonization of plots by M. papillatus gametophytes and no sporophytes. Carpospores of M. papillatus should result in recruitment of sporophytes ( "Petrocelis" crusts ) rather than the gametophytes

I observed. Yet there was strong recruitment of upright plants that became cystocarpic when the plots were approximately one year old. The crustose phase had minimal cover in fall clearings even after two years. Two possible explanations could account for this: 1) M. papillatus could be short-circuiting the reproductive cycle apomictically by producing carpospores that grow directly into gametophytes; 2) sporophytes (crusts) and gametophytes may have released spores at roughly the same time and there was a failure of settlement or survival of carpospores, resulting only in gametophytes. The former explanation is supported by culture studies in which M. papillatus apparently reproduced gametophytes apomictically in a large proportion of cases (Polanshek and

West, 1977; Guiry and West, 1983; Ohno et al, 1982; Masuda et al, 1984). This may 1 8

vary under different physical regimes associated with latitude (Zupan and West, in prep). While culture studies may not reflect field conditions, this widely observed anomaly in the life history of M. papillatus is suggestive of what may potentially occur in situ. There is no evidence for or against the latter explanation.

Cystocarps of E. muricata, likewise, should result in sporophytes, which in this case would be morphologically identical to gametophytes. Both gametophytes and sporophytes may have been present in the plots following clearing. Since I did not sample the plots for the presence of sporophytes, no real assessment of the success· of recruitment of carpospores can be made. In order to produce female gametophytes

(observed in a cystocarpic state in most experimental plots one year after initial disturbance) one of the two scenarios above would have to occur, though the failure of recruitment would not be a necessary accomplice to simultaneous sporogenesis of the isomorphic life-history stages. Samples of a population of E. muricata in San Luis

Obispo County (D. Woodward, pers. comm.) suggest that sporophytes and gametophytes produced spores at roughly the same time of year (summer). This would result in both phases recruiting into the spring experimental plots at once, and would explain the presence of cystocarpic females.

Thus, the recruitment of gametophytic plants following the observation of this same phase producing spores is not trivial it may indicate other than the "standard" life-history for M. papillatus , and simultaneous sporogenesis in the alternate stages of

E. muricata.

Patterns of abundance of the two species relative to each other were not consistent through time. While E. muricata clearly populated spring plots early on and

M. papillatus clearly populated fall plots, this relationship broke down and re­ established itself at six-month intervals. This may have been due to the apparent 1 9

changes in cover of the two species with "season". muricata was significantly more abundant in spring-cleared plots at 12-month intervals (i.e.- at 12 and 24 months following the disturbance}. These intervals occurred in the spring, when E. muricata cover was highest. Similarly, M. papillatus was significantly more abundant only at 12 month intervals, when its cover was at its yearly high. Despite this, however, M. papillatus was never significantly more abundant overall in spring disturbances and E. muricata was never significantly more abundant overall in fall disturbances.

The recurrence of these patterns indicates an underlying dominance of substratum by one of the species depending on seasonal provision of space. While the pattern varies through the year, the fact that most plots maintained higher cover of the original colonizer after two years indicates long term persistence of early successional events. This persistence of first perennial colonizers may be of great importance to the community as a whole (Dayton, 1975; Foster, 1975; Sousa, 1979b).

The relative recruitment of the two species is most interesting from the viewpoint of processes.controlling community structure. The red algae are the most diverse group of marine plants and many provide important habitat both for other plants and for animals (Glynn, 1965; Turner, 1983; Sousa, 1984}. If the plants that recruit and become dominant have different associated assemblages of organisms that rely on them for habitat, then the overall diversity of the community could be dependent on the time of disturbance. A study of the Balanus glandula-Endocladia muricata community by

Glynn (1965) reported 93 species of plants and animals associated directly with E. muricata, either in the plant or on the substratum immediately around. it.. Glynn found no similar assemblage associated with Mastocarpus jardinii (= Gigartina agardhii;

Guiry, et al, 1984), a morphologically similar congener of M. papillatus, and no similar study has been done on the associates of M. papillatus. While there was a trend for 20 spring-cleared areas to be slightly more diverse (M. Foster, unpublished data), and populated more by E. muricata , these experiments were not designed to test for such a. causal link.

While many of the plots had significant amounts of "bare" substratum, this was quite persistent through time, and I must assume that some non-recruitment factor (e.g.­ grazers or unobserved substratum characteristics) was keeping propagules from surviving to adulthood. Allelopathic interactions are almost certainly not important, since the plants normally grow in mixed stands. Certain grazers, on the other hand, became increasingly abundant with time following disturbance. Large limpets (mostly

Coflisella spp.) occupy many spaces and juveniles could usually be found around the perifery of clumps of E. muricata and individuals of M. papillatus .

Clearly the timing of disturbance was a significant factor in the successional development of these disturbances. The ability of the plants to respond to open space appears to have been a direct result of their phenological characteristics. The persistence of these plants may help to explain the common occurrence of small-scale differences in cover, patches of dominant plants in a monoculture, and the "mosaic" pattern so often ascribed to intertidal communities. Whether latitude has any bearing on community development or not remains to be tested. A study with more replication within sites and/or over a wider range might demonstrate a pattern that this design was incapable of finding. However, the results of this study indicate that, at least over 5 degrees of latitude, seasonal phenological patterns and site-specific differences may overshadow the effects of latitudinally varying physical and biological factors as regards succession and recovery from disturbance .. 21

KNOWLEDGMENTS

I am deeply indebted to a number of individuals and organizations for facilitating the completion of this project. First and foremost, I thank Michael Foster for the myriad ways that he has helped me. Gregor Cailliet and John Oliver, the other two members of my commitee, were also invaluable. Between them they have given me as diverse a perspective on science, nature and life as I could hope to obtain. This work could have been done without Andrew DeVogelaere (dude extraordinaire), but without his frequent discussion and occasional criticism it would not have been as sound or as fun. Many long hours were spent alone in the field while collecting data, and it was these times that made me most appreciate the help offered freely by A. Dauben, S Dahl, A. De

Vogelaere, D. Hardin, K. Langan, S. Lisin, L. Kiguchi, M. McCamy, D. Vilas, and S,

White. I thank them all with uniform warmth. My graduate career would have foundered long ago if not for the constant aid of Gail Johnston. For all her creative assistance, counsel and humor, I thank her. Sheila and Sandy in the library, and Dorothy in bookkeeping have been indispensible to me throughout. My family was a constant source of support and I thank them for pretending I was still credible through my long tenure in graduate school. This work was supported in part by a grant from the David and Lucille Packard Foundation, and some data was obtained while I was working on a project for the Minerals Management Service. Lastly, I thank the Moss Landing Marine

Laboratory Community, simply for existing. I've learned more about living and thinking here than anywhere else. 22

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Table 1 - Mean (S.E.) percent of plants cystocarpic during two periods of highest reproductive activity for Endocladia and Mastocarpus at five sites. Spearman rank correlation coefficient (r) is for relation between percent cystocarpic plants vs. Latitude. N = the number of plots used in the correlation for each species. Periods for Endocladia were May '85, July '85 and May '86. Periods for Mastocarpus were Sept. '85 and Nov. '85.

Site (Latitude- Degrees)

PSN PR Bol SR KH (35.728 N) (36.570 N) (37.982 N) (38.750 N) (39.602 N)

Endoc/adia r N 12.1 (1.72) 9.33 (1.72) 18.6 (2.56) 18.6 (2.48) 26.3 (2.28) 0.631 ** 42

Mastocarpus 78.0 (7.06) 84.7 (3.33) 94.7 (1.33) 97.3 (1.98) 96.7 (3.92) 0.564** 30 27

Table 2- Mean (S.E.) percent- cover of Endocladia and Mastocarpus in undisturbed "control" plots in four seasons from March 1985 through January 1986. Plots were combined for all sites in each season (N=18). One-factor ANOVA's tested for differences between seasons for each species. For Endocladia, fall cover was significantly less than all other seasons. For Mastocarpus , spring cover was significantly less than fall only.

Season

Spring Summer Fall Winter ANOVA

Endocladia 53.8 (6.86) 61.5 (7.29) 37.5 (5.59) 49.4 (6.83) p=0.0001 + + +

Mastocarpus 19.1 (3.68) 26.7 (4.93) 30.9 (5.01) 23.6 (3.85) p=0.042 + +# # +#

+# :cells with like symbols are not significantly different at0<=0.05 (Fisher's LSD Test). 28

Table 3 - Mean (S.E.) percent cover of Endocladia muricata and Mastocarpus papillatus in plots that had cover of one or both of the two species in at least two ( of three ) subplots. Cover in plots was estimated at six-month intervals following clearing. Spring-Cleared plots were cleared in March - April of 1985. Fall - Cleared plots were cleared in October of 1985. "p" value is for paired t­ tests done between species at each period in each season.

Spring Clearings

Period N Endocladia Mastocarpus p Total Cover (months) (plots)

12 13 15.0 (4.30) 0.90 (0.55) 0.009 45.5 (5.61)

18 15 23.7 (5.90) 20.7 (6.06) 0.774 83.9(10.1)

24 17 30.3 (6.77) 12.3 (3.22) 0.047 74.9 (9.44)

30 17 26.3 (5.67) 21.0 (5.15) 0.579

Fall Clearings

Period N Endocladia Mastocarpus p Total Cover (months) (plots)

12 12 9.03 (5.56) 41.8 (8.33) 0.001 81.5 (8.96)

18 17 11.3 (5.91) 22.6 (4.78) 0.024 71.9 (8.74)

24 18 11.0 (4.67) 36.0 (5.93) 0.004 29

Table 4 - Percent Cover of each species within spring-cleared plots that had cover of one or the other i 2 months after disturbance, and then within those same plots 24 months after disturbance.

12 Months 24 Months

Plot Endocladia Mastocarpus Endocladia Mastocarpus

Kibesillah. Hill S1 30 0 70 5 S2 53 0 66 0 S3 23 0 88 8

Sea Ranch No Recruitment

Bolinas S1 0 7 5 32 S2 5 2 23 25 S3 3 0 18 37

Pescadero Rocks S3 5 0 15 0

Pt. Sierra Nevada S1 32 0 30 0 S2 5 0 15 0 S3 5 0 3 0

Diablo Canyon S1 7 0 15 3 S2 13 3 67 13 S3 13 0 53 3 30

Table 5 - Percent Cover of each species within fall cleared plots that had cover of one or the other '12 months after disturbance, and then within those same plots 24 months after disturbance.

12 Months 24 Months

Plot Endocladia Mastocarpus Endocladia Mastocarpus

Kibesillah Hill F1 2 60 16 73 F2 0 53 8 48

Sea Ranch F1 0 13 0 8 F2 0 13 10 30 F3 0 5 2 38

Bolinas F1 0 62 2 47 F2 0 63 0 48 F3 0 92 0 65

Pescadero Rocks No Recruitment

Pt. Sierra Nevada F1 48 20 65 37 F3 52 22 62 38

Diablo Canyon F1 7 25 18 15 F2 0 75 0 75 F3 0 12 3 5 3 1

Figure 1 a - Endocladia muricata - cystocarps at tips of branches, above left (scale=5mm), and vegetative branches, above right (Scale=1cm). Modified after Abbott and Hollenberg, 1976. Schematic representation of the life history of Endocladia muricata, below.

CARPOGONIUM~SYNGAMY~ cYV I

0 SPERMATIA o o 0 () 0 0 0 0 0 CARPOSPORES 0 O 0 0 0 HAPLOID / o GAMETOPHYTES

0 0 --E----- 0 DIPLOID TETRASPORES SPOROPHYTE 32

Figure 1 b- Mastocarpus papillatus- female blades with papillae, above (scale=5cm). Modified after Abbott and Hollenberg, 1976. Schematic representation of the life history, including the proposed apomictic cycle, below. Modified after Polanshek and West, 1977.

CARPOGONI~M ~---- SYNGAMY~ CYSTOCARPS ~I ~ :0£D~

0 o SPERMATIA \ 0 0 00 0 0 0

0 CARPOSPORES OO 0 /000 HAPLOID GAMETOPHYTES 0 0 0 -

Figure 2 - Map showing the locations of experimental sites along the coast of California.

~ Kioesillah Hill----- I ···~···

Bohnas ------:----'

Pescadero Rocks---._..;

O&ablo Casl)On ---~ 34

Figure 3 - Diagram of an experimental plot showing the arrangement of quadrats in the center. The 25 em. border around the perifery was not sampled to avoid potential edge effects. 40 Endocladia - Sierra Nevada 1m Pescadero D Bolinas -u.i (21 Sea Ranch u) 30 tl Kibesillah 'I'"" + -.2 c. II...ca 0 20 0 m -:;::... 0 E (I) 0 10 a... (I) D..

0 may '85 jul '85 sep '85 nov '85 jan '86 mar '86 may '86

Figure 4 - Means + 1 Standard Error of the percentage of branches of Endocladia muricata with cystocarps at five sites for one year. Note that the November minimum corresponds to the period following Fall 1985 clearings. w V1 120 Mastocarpus - [3 Sierra Nevada ITI Pescadero D Bolinas -ui 100 u) 1ZJ SeaRanch r;l Kibesillah ..±. 80 0 c. 11-. ctl 0 60 0 til ->- 0 40

20

may '85 july '85 sept '85 nov '85 jan '86 mar '86 may '86

Figure 5 - Means + 1 Standard Error of the percentage of individuals of Mastocarpus papi/latus in a cystocarpic state at five sites for one year. Note that the May minimum corresponds to the period following the spring 1985 clearings.