MLML / M8~RllIBR;jRY 8272 MOSS LANDING RD. MOSS LANDING, CA 95039

FACTORS AFFECTING THE ABUNDANCE OF PARACYATHUS STEARNS!! ON SUBTIDAL ROCK WALLS

by Mark Pranger

A thesis submitted in partial fulfillment ofthe requirements for the degree of Master ofScience in Marine Science in the School ofNatural Sciences California State University, Fresno August 1999 ACKNOWLEDGMENTS

I would like to thank the members of my graduate advisory committee for their advice and guidance during this process. Dr. James Nybakken for his interest and education in invertebrate biology and for allowing me to help in the teaching of others. For the insights and humor of Dr. Mike Foster, that helped improve this study and my education. For the help of Dr. Stephen Ervin who in the last hours help me through all CSU Fresno's paper work and deadlines. I am grateful to the staff at the Pollution Studies Lab at Granite Canyon for their help during experiments and for allowing me the use of their working space. I am indebted to the staff at Moss Landing Marine Labs that kept all the equipment working and operational, and to the Dr. Earl and Ethel Myers Oceanographic and Marine Biology Trust for helping to fund this project. Most of all, thanks goes to the many students at Moss Landing. Without their help this study would not have been completed. Special thanks goes to; Mat Edwards for being a faithful dive buddy, to Torno Eguchi, Michelle White, Bryn Phillips, Cassandra Roberts, Michelle Lander, and Lara Lovera for their help on statistics and editing of early drafts, and especially to Michele Jacobi for her help in all aspects of this study and her constant encouragement for me to finish. I also would like to thank my family and friends for their love and encouragement and the joy they bring to each day. ABSTRACT

FACTORS AFFECTING THE ABUNDANCE OF PARACYATHUS STEARNSII ON SUBTIDAL ROCK WALLS

The distribution and abundance ofParacyathus stearnsii, a scleractinian ahermatypic solitary , is primarily limited to the lower edge ofrock walls and areas ofhigh sand scour on the central California coast. I attempted to determine how competition, predation, and settlement affected P. stearnsii distribution near the upper edge ofsubtidal rock walls. Survival rates ofP. stearnsii polyps were reduced when transplanted within COIynactis californica aggregations, but were not significantly different from controls. Potential predators did not consume adult P. stearnsii. Paracyathus stearnsii spawned between March and May of three consecutive years, but an insufficient number oflarvae were collected to test for settlement preferences. Biological effects examined in this study had limited influence on the adult population, suggesting patterns ofdistribution and abundance may be set in larval and juvenile stages.

Mark Pranger August 1999 TABLE OF CONTENTS

Page

LIST OF TABLES. VI

LIST OF FIGURES Vll

INTRODUCTION 1 METHODS 3 Patterns ofSpatial Distribution . 3 Laboratory Competition Experiment 5 Field Competition Experiment 6 Predation Experiment 7 Reproduction/Settlement 8 Growth Rates . 9 RESULTS 11 Patterns ofSpatial Distribution . 11 Laboratory Competition Experiment 12 Field Competition Experiment 12 Predation Experiment 13 Reproduction . 13 Settlement 14 Growth Rates . 14 DISCUSSION 16 LITERATURE CITED . 22 LIST OF TABLES

Table Page

I. Mean abundance per zone. . 11 2. Feeding test design and percentage of items at least partially eaten. 13 LIST OF FIGURES

Figure Page 1. Map of study area 4 2. Percent increase in size after 6 months, based on initial surface area of top of calyx. . 15 INTRODUCTION

Three ahermatypic scleractinian and one corallimorpharian compete for resources along the coast of central California (Chadwick 1991). These are usually separated into three horizontal zones at the upper and lower edges of subtidal rock walls (Pequegnat 1964, Morris et al. 1980, Chadwick 1987). At a site in Monterey bay, Chadwick (1991) found that the corallimorpharian Carynactis califarnica Carlgren 1936 was most abundant (53.5 % cover) near the upper edge, upper zone, where it can form large aggregations by asexual reproduction. Carynactis califarnica occurred only sporadically in the middle zone and never in the lower zone (Morris et al. 1980, Chadwick 1987, 1991, Patton et. al. 1991). The coral Astrangia lajallaensis (Durham 1947) was most abundant in the lower zone (30 % cover) where it forms encrusting colonies (Fadlallah 1982, Chadwick 1991). It was rarely found in the middle or upper zone. The cup corals Balanaphyllia elegans (Verrill 1864) and Paracyathus stearnsii (Verrill 1869) were found in all zones, but were most abundant in the lower zone (7.5 % cover for B. elegans and 0.8 % cover for P. stearnsii, Morris et al. 1980, Fadlallah 1983, Chadwick 1991). Competition among these species is thought to be one of the factors that influences the distribution and relative abundances of these species (Chadwick 1991). In field and laboratory experiments, Chadwick (1991) studied the hierarchical dominance of these species. She found that adult B. elegans suffered tissue damage from all other species, and C. califarnica killed the crawling larvae of B. elegans. Survival rates ofA. lajallaensis were reduced in the presence of C. califal7lica and P. stearnsii. In laboratory tests, P. stearnsii displaced C. 2 californica by one distance, but no tissue damage was seen on either species. Chadwick (1991) indicated that C. califomica was the dominant space competitor over B. elegans and A. lajollaensis, and co-dominant with P. stea17lsii.

When C. califomica was removed from the upper zone both B. elegans and A. lajollaensis were able to survive. Chadwick (1991) therorized that C. cal!fomica's competitive dominance was the primary factor limiting the abundance of B. elegans and A. lajollaensis within the upper zone. This reasoning does not hold true for P. stea17lsii. Paracyathus steamsii's apparent ability to displace C. califo17lica should have allowed it to be equally abundant within all zones. The objective of this study was to examine factors that potentially limit the abundance of P. stea17lsii within the upper zone. Rock walls were sampled to quantify the distribution of P. steal7lsii within Stillwater cove. Laboratory and field competition experiments were conducted to test Chadwick's (1991) results of co-dominance between P. steal7lsii and C. califomica. Feeding tests were conducted to determine the effect of predation on P. steamsii distribution. Larval stages were collected to test for settlement cues or preferences. METHODS

Field studies were conducted at Stillwater Cove, Pebble Beach, California

(36 0 34' N, 121 0 56' W, Fig. 1). The cove opens to the southeast, which dampens storms from the north and west. The outer half of the cove contains many outcroppings of sandstone and conglomerate rock that provided vertical surfaces for field manipulations.

Patterns of Spatial Distribution Sites within Stillwater Cove were chosen haphazardly to quantify the distribution and abundance of Paracyathus stem-nsii, califomica, elegans and their potential predators. A zodiac was driven seaward from Pescadero Rock (Fig_ 1) on randomly determined compass headings for random lengths of time. Divers using self-contained breathing apparatus (SCUBA) swam approximately 10 m away from the anchor line of the sampling vessel on a randomly chosen compass heading. Divers circled counterclockwise around the anchor line, and the first vertical wall greater than 5 m in height which contained P. steamsii and C. califomica was sampled. Based on pilot studies, it was determined that proximity to the upper or lower edges of rock walls had a more significant effect on the distribution and abundance of species than water depth. To compensate for this edge effect and reduce variances, all walls were divided into three zones: I) upper, 0-2 m from the upper edge; 2) middle, in between the upper and lower zones, 2-5 m in height; and 3) lower, 0-2 m from the bottom. Transect tapes were laid horizontally and vertically within each zone and four 0.25 m" quadrats were placed at random distances along the tapes. A 0.25 m" quadrat was large enough to adequately 4

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StilhvaterCove Carmel Bay

i! 0 Sites

N ** Pescadero t Rocks 5 sample P. steamsii and C. califomica (pilot study). The number of P. steamsii and B. elegans, percent cover of C. californica, depth, height from the bottom, compass heading of supporting wall, and number of potential predators were recorded for each quadrat. Percent cover was estimated from a grid of 36 fixed points within each quadrat. Potential predators were defined as known to eat cnidarians and other sessile invertebrates, including: Sun Stars (Pycnopodia lzeliantllOides), Masking Crabs (Loxorhynchlls crispatlls), Bat Stars (Asterina miniata), Leather Stars (Demzasterias imbricata), and Rainbow Stars (Ortlzasterias koehleri). After a site was sampled, or if no vertical wall was found, divers surfaced and a new heading and time length were chosen from that point. Percent cover data for C. califomica was arcsin transformed because of non­ normal distributions. Differences in mean abundances were analyzed using a two­ factor ANOVA (site and zone). Differences among levels were analyzed using the a posteriori Bonferoni method or two-sample t-test.

Laboratory Competition Experiment To test the effect of competition for space, C. califomica and P. steamsii were transplanted into aquaria at Moss Landing Marine Laboratories, Moss Landing, California. Corynactis califomica were transported on small pieces of shell or debris, whereas P. steamsii were chipped off rocks using a knife. Species were held in separate aquaria supplied with filtered seawater until needed. Small pieces of shell containing a single of C. californica were glued to glass slides and distributed among four trays with flowing seawater. Paracyathus steamsii polyps were glued directly to glass slides and randomly placed among the C. californica polyps. Six polyps from each species were placed randomly in two rows within each tray. Only adults with fully extended without chips or 6 cracks were used during the experiment. Twelve additional C. califol7lica polyps were placed randomly adjacent to the original polyps, half in interspecific competition and half adjacent to conspecifics. Effects of C. califOl7licalP. steal7lsii interactions were compared to C. cali/ornica/C. californica interaction. Paracyathus stearnsii did not cause tissue damage to conspecifics and is unable to move (Chadwick 1991, Pranger per. obs.), so no P. steamsii/P. stearnsii interactions were tested. All polyps were placed with < 5 mm between body columns, but not in direct columnar contact. Shorter polyps were elevated so their tentacular crowns were at the same height as taller polyps. Polyps were fed adult brine shrimp (Artemia salina) once a week until satiated. The percentage of individuals from each species showing tissue damage or the percentage of C. califomica showing movement away from adjacent individuals was recorded twice a month for 4 months. Tissue damage was defined as discoloration or scarring. Movement was defined as > 5 mm or out of tentacular contact. Percentages were arcsin transformed because of non-normality. Differences in percentage of individuals that moved were analyzed using a randomized blocked ANDVA (species interaction blocked within trays).

Field Competition Experiment Competition was tested in the field by transplanting P. steal7lsii from the lower scour zone into three separate treatments. In the first treatment polyps were transferred into the upper zone and placed in the center of a C. califol7lica aggregation in tentacular contact. For the second treatment, polyps were transferred into the upper zone but not in contact with C. califol7lica. This treatment controlled for movement into the upper zone without competition with C. califomica. The third treatment was a transplant control with P. steal7lsii 7 polyps being replaced in the lower zone. Ten polyps were transplanted for each treatment type. This experimental design was replicated on four separate walls. All walls were on the side of rock plateaus; two were located at the west end and two at the east end of Stillwater Cove. These walls were chosen for their large surface area and numerous aggregations of C. califomica. The tops of the walls ranged from 8 to 10 m in depth with bottom depths ranging from 16.5 to 19.5 m. All polyps were transplanted directly from the bottom to 2 em diameter predrilled holes. Polyps were cemented in place with Z-spar® marine epoxy. Only adults without cracks or chips were used. After 1 week, replicates were re-examined and any missing individuals were replaced. This process was repeated for 2 weeks until all treatments had 10 individuals. The location of all holes were marked using yellow bicycle tape so they could be found if individual polyps were lost. Polyps were checked once a month from January 1994 through May 1996. The condition of each polyp was recorded as: 1) healthy; extended for feeding without tissue damage, 2) withdrawn; not extended for feeding, 3) dead; no tissue visible, or 4) gone; loss of the entire calyx. The survival rate was calculated as the number of live polyps at the end of the study divided by the number of calyxes remaining (live and dead). These percentages were arcsin transformed due to non­ normality and percentage differences in survival were analyzed using a randomized blocked ANaYA (interaction type blocked within sites).

Predation Experiment

To test the effects of predation upon study organisms, P. steamsii and C. califomica were exposed to potential predators. Potential predators were brought to Granite Canyon Pollution Studies Laboratory, Carmel, California and fed mussels (Mytilus califomianus) for 1 day to try to minimize differences in previous 8 feeding periods. Predators then were held in filtered seawater aquaria without food for 1 to 3 weeks to increase hunger levels. Potential predators included Sun Stars (Pycnopodia helianthoides), Masking Crabs ( crispatus), Bat Stars (Aster-ina miniata), Leather Stars (Dermasterias imbricata), and Rainbow Stars (Orthasterias koehleri). All potential predators were known to eat cnidarians, and were present in previous rock wall surveys. Five individuals of either prey item (P. steamsii or C. californica) were placed in glass aquaria with flowing filtered seawater. Prey species were allowed to acclimate to the tanks for I day before potential predators were introduced. Predators were chosen haphazardly and placed into the glass tanks for 24 hours. After 24 hours the number of dead or partially eaten prey items were counted. All prey items were then removed and replaced with a mussel (M. califomianus) control to verify that a potential predator was hungry and able to eat. After 12 hours, the percentage of predators that ate mussels was calculated. No data analysis was performed as no solitary corals were eaten (see results).

Reproduction! Settlement Paracyathus steamsii are known to contain mature gametes from February until May (Fadlallah and Pearse, 1982). Adult P. steamsii were collected twice a month from January through June during 1995-1997, and once a month from June to December during 1995. Ten adults were dissected to check gamete status and to remove eggs and sperm in attempts to induce external fertilization. Live adults were maintained in a flow-through tank that allowed for all exported water to be filtered, to collect any naturally spawned larvae. In an attempt to induce release of larvae or eggs and sperm, adults were placed in petri dishes and exposed to one or more environmental cues; exposure to free swimming sperm, warming and cooling 9 of ambient water, changes in pH, salinity increases and reductions, and varying daylight hours. Settlement preferences were tested in the field using cleared plots on rock walls. Cleared plots were located on two of the walls used in the competition study. Ten 100 cm" plots were cleared on each wall in three areas: the upper zone within C. califomica aggregations, the upper zone outside of C. califomica aggregations, and in the lower zone. Plots were scraped with a putty knife and scrubbed with a nylon brush to remove all visible tissue. All plots were cleared in January 1994 and examined twice a month until July 1994. Plots that contained unidentifiable organisms were photographed for marking ofexact location and for later identification. Plots were not disturbed by observers except for removal of encroaching C. califomica. To estimate recruitment to undisturbed areas, a one m" quadrat was used to sample the upper and lower zones. In July 1994, five quadrats were placed haphazardly within each of the upper and lower zones on two separate walls. All polyps less than 5 mrn in diameter were counted.

Growth Rates Growth rates of P. steamsii polyps from the lower zone were measured at Stillwater Cove from August 1994 to August 1995. Calipers were used to measure the length and width across the top of the calyces of 30 polyps from five different walls. Each measured polyp was marked with bicycle tape nailed 3 cm above the polyp. Each polyp's depth, position on the rock, and compass direction faced by supporting wall also were recorded to aid relocation. Nine polyps were relocated and measured in March 1995. Due to the limited re-Iocation 30 additional polyps were measured at the same five locations. Seventeen polyps were relocated and 10 measured in August 1995; four of these polyps were from the nine individuals relocated in March. These last four measurements were not independent, but were included because of the small data set. Lengths and widths were used in the following formula to calculate the surface area of a flat disk at the top of the polyp.

Oral disk surface area = L/2 * W/2 * 1t

Due to large variances, column shapes, height and width of the bases were not used as measures of calyx growth. Differences between Fall and Spring growth rates were analyzed using a Mann-Whitney Test. To verify the accuracy of surface area measurements, the same method was used to calculate surface area of 50 calyces in the laboratory. These measurements were compared against measurements of the same 50 calyces made with a calibrated Image Analyzer (Image v. 1.37). RESULTS

Patterns of Spatial Distribution Paracyatlws stearnsii abundances differed significantly among zones

(F2.66= 9.66 p

2 Table 1. Mean abundance per zone. Mean # (± SE) 0.25 m , except Corynactis is % cover (+ SE). Pooled values from 24 quadrates on six seoarate walls. Paracvathus BalQ110phyllia cOl}'IIQctis Asterilla Other Sea Stars Upper Zone 0.35 ± 0.13 5.10 ± 2.18 0.32 ± 0.03 0.621 ± 0.18 0.28 ± 0.10 Middle Zone 2.00 ± 1.20 11.32 ± 2.55 0.11 ± 0.03 0.517 ± 0.17 0.069 ± 0.05 Lower Zone 10.1O±1.64 12.08±2.75 O.OO±O.OO 0.586+0.14 0.034+0.03 12

The most abundant potential predators were bat slars (Asterina minima). They were found in all three zones with a slight increase in abundance in the upper zone (Table I). All other species of asteroids (except A. miniata) were grouped together because of low abundances. Abundances of this group were greater in the upper zone but not significantly different among zones (F2•66= 2.297 p=O.107). The middle zone was comprised of a mixture ofspecies from the upper and lower zones (Table 1). No other potential predators were found in elevated abundances or showed a distinct distribution pattern.

Laboratory Competition Experiment During the 4 month lab competition study, no tissue damage was visible on either C. californica or P. stearnsii polyps. Competition analyses, therefore, were based on movement of C. califomica. Ninety-two percent of C. californica moved at least one tentacle distance away from P. steamsii, whereas only 21 % of C. californica moved away from conspecifics. / P. stearnsii interaction caused significantly greater movement than C. californica / C. californica interactions (F I•3= 17.68 p=0.025). There was no significant difference among blocked experimental trays (F3.,= 0.140 p=0.930).

Field Competition Experiment The results from the field competition studies indicated significant differences in survival rates between transplant treatments (F2,4= 8.07 p=0,039), but not among sites (F, 4= .579 p=O.60l). A Bonferoni test indicated significantly greater survival rates for P. stea17lsii when transplanted within the lower zone (x

= 96%) than when placed within an aggregation of C. califo17lica ( x = 76%, to.017 (4)=29.5 p=0.048). Survival rales of P. stea17lsii polyps placed within the upper 13 zone outside of aggregations (x = 89%) were not significantly different from polyps within C. califomica aggregations or polyps transplanted to the lower zone

(tooI7 (4)=13.2, 16.3, p=0.44, 0.27, respectively). These results were from analysis of only three walls. Data from the fourth wall were not included due to the disappearance of most polyps 3 months after the experiment was started.

Predation Experiment Neither P. steamsii nor C. califo171ica were eaten by any potential predators. Three tests were conducted with Pycnopodia helianthoides with starvation times ranging from 1 to 3 weeks. The percentage of P. helianthoides that ate mussels ranged from 70 to 100% (Table 2). All other predator species were tested after two weeks of starvation and between 50 and 80% of predators ate the controls (Table 2).

Table 2. Feeding test design and percentage of items at least partially eaten.

Weeks % ofPrey Items Eaten % ofMytillls Predator starved Paracvathus Corynactis Eaten Pycnopodla heliantholds 1 0 0 70 Pycnopodla heliantholds 2 0 0 100 Pycnapodla heliantholds 3 0 0 80 Loxorhynchlls crlspatlls 2 0 0 60 Asterina minta/a 2 0 0 70 Dermasterias imbricata 2 0 0 50 Orthasterlas koehlerl 2 0 0 80

Reproduction Reproduction of adult Paracyathus stea171sii from Stillwater Cove followed similar seasonal patterns as found by Fadlallah and Pearse (1982). Females contained oocytes throughout the year with a portion maturing during early January. Spent ovaries were found from mid to late February, and no mature 14 oocytes were found after May. In 1996 all mature oocytes were released by the end ofApril. Males contained inactive sperm most ofthe year, with active sperm first appearing during December. Concurrently, gonad size began to increase and continued increasing until February. Spawned testes were not seen until the end of March and individuals with highly developed gonads were not seen after May.

Settlement Settlement experiments were unsuccessful in both the laboratory and field. Only five larva were collected in 1995 after introducing sperm into petri dishes containing adults. Larvae may have been released naturally and not as a result of experimental cue, as neither this method, nor any other, induced spawning in 1996 or 1997. Areas cleared for settlement at Stillwater Cove had no detectable recruitment ofP. stearnsii. Early colonizers such as barnacles and hydroids recruited to plots in the upper zone, whereas lower plots had only limited recruitment ofencrusting species. The density ofrecruits ofP. stearnsii larvae outside ofcleared plots in the lower zone was approximately 1.5 ± .45/ m2 ( x ±SE). Paracyathus stearnsii recruits were found only in the lower zone on similar substratum as the cleared plots.

Growth Rates Due to the unknown starting age ofpolyps, the percent increase in size after 6 months was plotted against size at initial measurement (Fig. 2). Individuals smaller than 50 mm averaged a 124% increase in size. Individuals larger than 50 mm averaged a 20% increase with the largest individuals increasing by 10%. No difference was found between Fall and Spring growth rates (U 0.05(2)8.18= 108, U=105, U'=38.5). Differences in area measurements between hand held calipers 15 and the Image Analyzer averaged 0.71 mm" or 0.42%, with the greatest variance being 3.1%.

Percent increase vs initial Area

1.60 III 1.40 I A III 1.20 <0 !"

Fig 2. Percent increase in size after 6 months, based on initial surface area of top of calyx. Fall growth period for August 1994 to March 1995. Spring growth period from March 1995 to August 1995. DISCUSSION

Paracyathus stearnsii and Carynactis califarnica in Stillwater Cove had vertical zonation patterns similar to those found in other studies (Pequegnat 1964, Chadwick 1991, Patton et. al. 1991). Carynactis californica had a patchy distribution on rock walls. This distribution pattern and variations in abundances within zones were probably the reason for the interaction effect between sites and zones. COIynactis californica were only found in areas of high water motion facing the opening of Stillwater Cove (south to southeast), and within the upper zone. The upper zone is often the area of the greatest rate of change of species composition due to removal and recolonization of species caused by disturbance (Pequegnat 1964, Gerrodette 1979). Rapidly growing and asexually reproducing species (eq. C. califomica) are more adapted to this environment because of their ability to rapidly occupy open space (Sebens 1985). Paracyathus steamsii was most abundant near the lower zone and in areas of high scour. Paracyathus steamsii is not limited to the bottom, and it has occupied similar scoured habitat 10 m off the bottom on sand-scoured pinnacles off the Big Sur Coast, CA (Impietro per. comm.). The lowest zone was devoid of most other sessile species except Balanaphyllia elegans, Astrangia lajollaensis, and a few encrusting species.

Paracyathus steamsii's ability to withdraw into its calcified calyx, and to regenerate lost tissue and calyx sections is thought to help it survive in similar environments of sand scour and high water motion (Pequegnat 1964, Gerrodette 1979, Pranger per. obs.). The area between these two zones, the middle zone, had the greatest variability of species including hydroids, bryozoans, ascidians, red and brown algae, small aggregations of C. califarnica, and a few scattered P. steamsii. 17

Quadrats sampled in this area were more or less similar to the upper or lower zone based on proximity to either zone. In the laboratory test, significantly more C. californiea moved away in C. californiea / P. stearnsii interactions than in C. ealijimzica / C. californica interactions. These results were similar to those of Chadwick (1991), who found 86% of C. ealifornica moved to avoid P. stearnsii. In Chadwick's (1991) experiments between C. californica and . C. californiea was found to be the dominant competitor and caused excessive amounts of tissue damage to B. elegans. No tissue damage was observed between C. californiea and P. stearnsii in either this or Chadwick's study. The lack of tissue damage to either species may be due to avoidance after very minimal aggressive behavior or rapid regeneration rates of tentacular tissue. Field results of competition among multiple individuals were more complicated than the results of laboratory experiments. Survival rates of P. stearnsii were reduced by transplantation into the upper zone, but were only reduced significantly when combined with competition effects. The effect of competition from multiple competitors on a single P. steamsii polyp may hinder the ability of the coral to feed. Paraeyathlls steamsii placed within an aggregation of C. califomiea had limited space to feed and grow. When tentacles from different species touched, the interacting and adjacent tentacles of both species were usually withdrawn for a short amount of time (Pranger per. obs.). Paraeyathlls stearnsii within C. ealifomica aggregations came into contact with many opposing tentacles, resulting in the withdrawal of many of its own tentacles. The time spent fighting with adjacent C. califomica reduced the time available for feeding. Adjacent C. califomiea were not as affected because of their ability to feed with tentacles not in interaction with P. steal"/lSii. Some P. steamsii polyps 18 survived for 2 years in a weakened half-retracted state during this study. During this long term siege Paracyathlls stearnsii were able to stop overgrowth by C. californica, but unable to force C. californica to retreat. Paracyathlls stearnsii would be more susceptible to predation, disease, or disturbance in this weakened condition (Ravindran et al. 1999). Larger and more robust P. stearnsii were able to force C. californica to move away during this competition experiment, creating a halo of open space around themselves. The presence of a clear space between competitors has been reported for many corals (Jackson 1977, Bak and Engel 1979, Sheppard 1982, 1985). Paracyathlls stearnsii within this halo would be able to feed, grow, and presumably reproduce. A polyp of P. stearnsii surrounded by C. californica would gain the added protection from overgrowth of nearby settlers such as bryozoans and hydroids (Jackson 1977). The halo effect may limit the interactions between P. stearnsii and C. californica as tentacles would have to be extended further to touch each other. The significant difference in survival rates found in the field competition study indicated that the upper zone does negatively effect survival of adult P. steamsii. The lack of significant differences in survival rates between P. stearnsii within and outside of the C. californica aggregation suggested competition with C. californica by itself was not a significant factor. Competition for space and resources with other organisms may affect P. steamsii survival. BalanophyUia elegans and other adjacent species were shown to experience reduced water motion and food availability in the presence of ascididan and other rapidly growing colonizers (Russ 1980, Sebens 1985, Bruno and Witman 1996). Brushing by algae caused polyp retraction and reduced feeding in B. elegans, enhancing overgrowth by algae (Coyer et al. 1993). 19

Predators can control the distribution and abundance of prey (Paine 1966, 1974, Connell 1971, Gaines 1985). The potential predators selected for this study did not feed on P. stearnsii adults. Predators were seen to step over or avoid prey items within the aquaria. Annett and Pierotti (1984) found that C. califarnica was a large portion of the diet of Dermasterias imbricata. Annett and Pierotti did find that D. imbricata would preferentially consume other anemones instead of C. califarnica if other options were available. Patton et al. (1991) found that Pisaster gigamells did walk over and consume C. califarnica mixed with other prey types. Pisaster achracells were found to avoid C. califarnica aggregations (Patton et al. 1991). One explanation for these differing results may be the use of lager adults during this experiment. Adult polyps may have had high nematocysts densities or other chemical defenses that made them less palatable to prey species (Gochfeld 1994, 1995). Predation pressures on larval and juvenile P. stearnsii were not tested, but have been shown by others to have great effect on limiting distribution (Bak and Engel 1979).

Recruitment (or survivorship) rates of newly settled P. stearnsii were low. Only 1.5 polyps m- 2 < 5 mm diameter were found in July 1994, all within the lower zone. This was much lower than the average 60 polyps m-2 ofjuvenile B. elegans found at Hopkins Marine Station, Pacific Grove, CA. (Fadlallah and Pearse 1982). The lack of polyps from the upper zone may be due to lower survivorship or the lack of settlement cues in the upper zone. Fadlallah and Pearse (1982) found that 50% of newly settled B. elegwls larva died within 2 weeks. Not enough polyps were collected in this study to test for settlement cues in the lab. The lack of recruitment to cleared plots within the field may have been due to generally low recruitment or to the removal of settlement cues during the clearing 20

process. Recruits were found in areas surrounding cleared plots within the lower zone. Future studies should focus on the effect of predation on larval and juvenile life stages as well as settlement cues. Predation by suspension feeders has been shown to limit larval abundance and settlement rates in corals (Young 1988, Tanner 1995, 1997). Larvae of many species have the ability to select settlement sites (Connell 1961, Gaines et al. 1985, Roughgarden et al. 1988, Young 1990). Scleractinian larvae settled in the same zone as adults and were restricted to settlement on hard substrata (Adjeroud 1997, Bak and Engel 1979). Balanophyllia elegans recruits were only found near adults on similar substrata (Fadlallah 1982). Settlement preferences were not tested for P. stearnsii because of low numbers of larvae collected. However, naturally occurring small juveniles were only found in the lower zone. If P. stearnsii larvae showed an affinity to the lower zone due to chemical cues or presence of adults, it could explain the current distribution of adults. The low growth rate of P. steamsii may reduce its chances of survival. The process of producing a calyx reduces the rate at which P. stearnsii can increase in size (Coyer et al. 1983). All non-transplanted P. stearnsii found in the upper zone

2 had surface areas greater than 70 mrn • Paracyathus stearnsii have long lives (40 yrs Gerrodette 1979), but to reach a size of 70 mrn2 would take at least a year according to size increase estimates (Fig 2.). Smaller coral polyps are more susceptible to overgrowth and physical attack than are larger individuals (Tanner 1995, Bak et al. 1996, Aerts and Soest 1997). Larger polyps have more resources to develop increased numbers of nematocysts and chemical defenses and are more likely to recover from disturbance and damage (Pranger per. obs.) 21 Connell (1978) stated that species composition is a consequence of past and present interspecific competition resulting in each species occupying the habitat on which it is the most effective competitor. This study suggested that much more than just interspecific competition has influenced the distribution of P. steamsii. Slow growth and longevity may aid the survival of P. steamsii in the more disturbed and sand-scoured lower zone, but these same traits may inhibit its survival in the upper zone. The particle-rich, rapidly changing upper zone described by Pequegnat (1964) is often occupied by clonal forms such as C. califamica that can quickly convert food to growth (Sebens 1985). Competition for space and food, as well as larval predation, may greatly reduce recruitment and survival of P. steamsii in the upper zone. However, the survival rates of transplanted adult P. steamsii and the existence of large individuals within the upper zone indicated P. steamsii was able to compete once established. LITERATURE CITED

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