Effects of sand burial and movement on rocky intertidal bench

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<ul><li><p>EFFECI'S OF SAND BURIAL AND MOVEMENT ON ROCKY INTERTIDAL BENCH COMMUNITIES IN CENTRAL CALIFORNIA </p><p>A thesis submitted to the faculty of San Francisco State University </p><p>and Moss Landing Marine Laboratories </p><p>in partial fulfillment of the requirements for the </p><p>degree </p><p>Master of Science In </p><p>Marine Sciences </p><p>by </p><p>Carolyn Kathryn Bretz </p><p>Moss Landing, California </p><p>1995 </p></li><li><p>EFFECTS OF SAND BURIAL AND MOVEMENT ON ROCKY INTERTIDAL BENCH COMMUNITIES IN CENTRAL CALIFORNIA </p><p>Carolyn Kathryn Bretz </p><p>San Francisco State University </p><p>1995 </p><p>ABSTRACT </p><p>Sand burial may play an important role in determining the local, small scale distribution </p><p>and abundance of many rocky intertidal species at Waddell Bluffs and Scott Creek. The </p><p>purpose of this research was to explore the role of natural sand accumulation in structuring </p><p>benthic algal and sessile invertebrate communities within a system seemingly dominated by </p><p>this physical disturbance. Intertidal assemblages were influenced by a seasonally recurring </p><p>gradient of sediment burial resulting in temporal and spatial heterogeneity. The mosaic </p><p>patterns produced were responses to different microhabitats and intercommunity </p><p>successional stages created by seasonal disturbance. Seasonal surveys showed areas with </p><p>heaviest sediment deposition harbored a mixture of fleshy brown (Pelvetia fastigiata) and </p><p>red (Mastocarpus papillatus, Mastocarpus jardinii and Mazzaella splendens) algae, and </p><p>extremely low densities of grazing invertebrates, possibly due to their intolerance to </p><p>prolonged burial. The green algae, Ulva sp. dominated sites where sand burial was </p><p>intermediate. Marine invertebrates were still rare at intermediate sites. Sand covered both </p><p>of these assemblages most of the year. The third major assemblage was formed by the </p><p>filamentous red alga, Polysiphonia pacifica, which encompassed areas with low, but </p><p>persistent sand cover (never more than 5-10 em thick). Other areas with low sand cover </p><p>Ill </p></li><li><p>were dominated by the anemone, A11tlwpleura elegantissima, and the sand tolerant alga, </p><p>Neorlwdomela larix. </p><p>Experimental clearings created in each algal assemblage were colonized by the common </p><p>algal species surrounding each 1 m2 patch, suggesting that either dispersal was limited or </p><p>colonizers were influenced strongly by local habitat characteristics. Recolonization by </p><p>limited dispersal in sand-swept habitats could explain these results. These hypotheses were </p><p>tested partially in reciprocal transplants of Mastocarpus papillatus and Polysiplwnia pacifiCa </p><p>which showed differential survival with varied sand burial depths. M. papillatus persisted </p><p>under deep sediment burial for significantly (p</p></li><li><p>ACKNOWLEDGMENTS </p><p>Alt/wugh nature begins with the cause and. ends with the experience, we must follow the opposite course, to begin with experience and by the mea/IS of it investigate the cause. </p><p>Leonardo da Vinci </p><p>This thesis went to hell and back. It only seems fitting to thank those that made the </p><p>journey with me. Through coursework and discussions, I have received a great deal of </p><p>scientific advice and wisdom from my committee members Drs. Michael Foster, James </p><p>Barry, and John Oliver. For this I am grateful. Many thanks to Dr. Thomas Niesen who </p><p>took time from his hectic schedule to read my thesis and participate as a committee member. </p><p>A significant part of my career at Moss Landing Marine Labs was inspired by John Oliver. </p><p>John has always encouraged me to follow the rules of science, but to have fun doing it. I </p><p>am grateful he took the time to support my interest in pursuing too many projects. </p><p>I am eternally grateful to the many friends that rode with me through the best and </p><p>worst times. Thanks to those that assisted me in the field and lab, especially Ken Israel, </p><p>Cassandra Roberts, Mary Nishimoto, Mike McNulty, Dahnmit McHue, and Gina Crane. </p><p>Thanks also to my very supportive friends Diana Steller, Nicole Crane, Sandy Yarbrough </p><p>and Sandi O'Neil; and Dr. Andrew DeVogelaere who had a fresh perspective and always </p><p>provided a chuckle. </p><p>My graduate career would not have been possible without the love and support of </p><p>some very special people. I owe alot to my parents, whose avid interest in nature and the </p><p>scientific world was an impetus for my own love of science. Special admiration and </p><p>respect go to Jim Barry who not only gave unlimited scientific guidance, but was a </p><p>personal inspiration in many, many ways. </p><p>This work was supported, in part, by a grant from the California Department of </p><p>Transportation. </p><p>v </p></li><li><p>TABLE OF CONTENTS </p><p>LIST OFT ABLES ............................................................................ viii </p><p>LIST OFF1GURES .......................................................................... x </p><p>INTRODUCTION ............................................................................ 1 </p><p>METHODS AND TECHNIQUES .......................................................... 5 </p><p>Study Site ........................................................................... 5 </p><p>Intertidal Survey Stations ......................................................... 5 </p><p>Physical Environment ............................................................. 6 </p><p>Species Composition and Cover ................................................. 6 </p><p>Field Experiments .................................................................. 8 </p><p>Artificial Clearing ................................................................ 8 </p><p>Transplant Experiment .......................................................... 9 </p><p>Statistical Analyses ................................................................. 10 </p><p>RESULTS ...................................................................................... 12 </p><p>Species Composition in Intertidal Mosaic ....................................... 12 </p><p>Sediment Influence on Species Composition and Cover ...................... 13 </p><p>Clearing Experiments .............................................................. 14 </p><p>Reciprocal Transplants ............................................................ 16 </p><p>Herbivore Densities ................................................................ 17 </p><p>D!SCUSSION ................................................................................. 19 </p><p>General Patterns .................................................................... 19 </p><p>Assemblage Patterns ............................................................... 21 </p><p>Algal Translocation ................................................................ 25 </p><p>vi </p></li><li><p>Clearing Experiment ............................................................... 27 </p><p>Benthic Invertebrates .............................................................. 30 </p><p>Rocky Shore-Sandy Beach Ecotone ............................................. 31 </p><p>LITERATURE CITED ....................................................................... 34 </p><p>vii </p></li><li><p>LIST OF TABLES </p><p>Table Page </p><p>1. Time table showing duration of ol:iservations and experiments ...................... .41 </p><p>2. Summary of sand deposition at rocky intertidal stations from Waddell Bluffs </p><p>and Scott Creek based on monthly samples for 14 months (July 1988 to August </p><p>1989). Assemblage type was named for the dominant species characterizing that </p><p>station. !=artificially armored shoreline. nd=no data .................................. .43 </p><p>3. Colonization of algal removal plots in the Ulva, Polysiphonia and Red-Brown </p><p>Algal habitat Plots were cleared February 1, 1990 and sampled periodically </p><p>until AprilS, April 29 and May 13, respectively. Each data point represents the </p><p>mean (1 SE) of 4-6 plots. Entero-diatom refers to an Enteromorphal </p><p>filamentous diatom mix found in the shallow depressions of the rocky bench. </p><p>Arrow indicates date of initial clearing .................................................. .4S </p><p>4. Single factor analysis of variance (ANOV A) results are shown for seasonal </p><p>sand depth versus assemblage (n=14). Student-Neuman-Keuls (SNK) test was </p><p>used for pairwise multiple comparisons (Zar 1984). *pO.OS) ....................................................................... .47 </p><p>Sa. Results of reciprocal transplant experiments. Data are the mean number (SE) </p><p>of thalli and percent cover of transplants over time for Mastocarpus and </p><p>Polysiplwnia, respectively. Comparison of transplants with a cleared border </p><p>and non-border are shown. In the field, transplants were marked with coded </p><p>PVC to indicate patch type (Mastocarpus {M} or Polysiplwnia {P}), treatment </p><p>replicate number (1-S), and treatment type (species and border). Categories for </p><p>qualitative observations of unmanipulated plants within recipient patches are as </p><p>follows: no change (NC), healthy appearance(+), tissue loss(-), disintegrated </p><p>(D), orange, white or bleached appearance (B), gone (0) ........................... .49 </p><p>Sb. Results of reciprocal transplant experiments. Data are mean sand depth over </p><p>time in recipient patches (n=IO). Measurements were made at3, 12, and 2S </p><p>weeks ........................................................................................ Sl </p><p>viii </p></li><li><p>6a. Single factor analysis of variance (ANOVA) results are shown for transplant </p><p>experiment recipient site (n=6) versus treatment border (n=3). ANOVA results </p><p>demonstrating significance were analyzed with Student-Neuman-Keuls (SNK) </p><p>test for multiple comparisons (Zar 1984). *p</p></li><li><p>LIST OF FIGURES </p><p>Figure Page </p><p>1. Map of permanent sampling stations"at Waddell Bluffs and Scott Creek in central </p><p>California. Numbers indicate station reference markers on rocky shale bench </p><p>outlines ...................................................................................... 63 </p><p>2. Winter (top) and summer (bottom) cover of beach sand over the rocky shale </p><p>benches under Waddell Bluffs. Arrows indicate natuml boulder markers ........... 65 </p><p>3. Field design for the reciprocal tmnsplant experiment. Factors include sand depth </p><p>(low, high), and border effect (none, 10 em). Three treatment levels (reciprocal </p><p>transplant, reciprocal tmnsplant with a 10 em clearing, and a control translocation) </p><p>were used to test the response of tmnsplanted algae to different sand habitats (n=5). </p><p>Qualitative "natuml" controls of unmanipulated plants within each recipient patch </p><p>were also examined (not shown). Recipient patches (n=6) in high and low sand </p><p>habitats dominated by Mastocarpus papil/atus and Polysiplwnia pacifica, </p><p>respectively, were chosen mndomly. Percent cover and number of thalli were </p><p>measured over a 6 month interval for P. pacifica and M. papillatus, </p><p>respectively .................................................................................. 67 </p><p>4. Seasonal change in sand depth in rock-y intertidal habitats at Waddell Bluffs and </p><p>Scott Creek sites. Data were collected monthly for 14 months from May 1988 </p><p>through August 1989. Each point represents the mean (1 standard error) of </p><p>measurements from random locations (n=10) .......................................... 69 </p><p>5. Tree diagmm resulting from avemge linkage clustering using Ward Minimum </p><p>Variance Method on percent cover data Euclidean distance was used to measure </p><p>similarity, demonstmted by clustering of independent stations (and replicates) </p><p>into 4 distinct groupings chamcterized by taxonomic relationship. Labels indicate </p><p>site (Waddell Bluffs, w, and Scott Creek, s), station number, and replicate number </p><p>(1-5) .......................................................................................... 71 </p><p>6. Percent cover of Viva sp. and sand depth for intertidal sites dominated by Viva sp. </p><p>Data were collected monthly from July 1988 through August 1989. Sand depths </p><p>X </p></li><li><p>6. Percent cover of Viva sp. and sand depth for intertidal sites dominated by Ulva sp. </p><p>Data were collected monthly from July 1988 through August 1989. Sand depths </p><p>and percent algal cover are the mean (1 standard deviation) of 10 and 5 </p><p>measurements from random locations, respectively. nd=no data for percentage algal </p><p>cover. Note scale change from a, c to b. Areas indicating an unknown percent cover </p><p>due to sand are designated with [?~ followed by a dashed line ........................ 73 </p><p>7. Percent cover (n=5) of brown and red macroalgae and sand depth (n=IO) for </p><p>intertidal sites dominated by this mixed assemblage. Only species which held an </p><p>average of &gt;5% cover at some sampling date are included. nd=no data for </p><p>percentage algal cover ...................................................................... 75 </p><p>8. Percent cover (n=S) of Polysiphonia pacifica and sand depth (n=10) for </p><p>intertidal sites dominated by Polysiphonia .............................................. ?? </p><p>9. Percent cover (n=5) of Antlwpleura elegantissima and sand depth (n=IO) for </p><p>intertidal sites dominated by the sea anemone ........................................... 79 </p><p>XI </p></li><li><p>INTRODUCTION </p><p>Physical disturbance can be important in providing space for colonization by </p><p>opportunistic and late successional species and has been shown to maintain diversity in </p><p>some systems by preventing monopolization of space by competitive dominants (Dayton </p><p>1971; Connell 1972; Sousa 1984; Pickett 'and White 1985). Disturbances, such as the </p><p>seasonal shifting of sand causing frequent episodes of burial and scour in intertidal </p><p>habitats, have an enormous, but poorly understood, effect on community development and </p><p>organization (Daly and Mathieson 1977; Taylor and Littler 1982; Littler et al. 1983). Daly </p><p>and Mathieson ( 1977) found that the microhabitats created by sand disturbance were </p><p>difficult, if not impossible, to characterize since they reflected both varying depths of burial </p><p>and frequencies of abrasion. </p><p>The habitat ecotone between exposed rocky shores and adjacent sandy beaches is an </p><p>insufficiently understood environment (Stewart 1983; Dethier 1991). Species living within </p><p>this environment must have behavioral and physical attributes that allow them to survive the </p><p>constraints of both habitats. In addition to factors such as wave exposure, desiccation, </p><p>insolation, predation, and grazing associated with rock)' shores, the biota of sand-swept </p><p>rocky habitats must endure additional physical stress from scour and burial by sediments </p><p>leading to abrasion and light reduction. Relatively few studies of rocky intertidal systems </p><p>have assessed the effects of sediments from adjacent beaches on the structure of </p><p>populations and communities (Frank 1965; Dalli 1969; Markham and Newroth 1972; </p><p>Markham 1973; Daly and Mathieson 1977; Mathieson 1982; Robles 1982; Littler et al. </p><p>1983; D'Antonio 1986; Shaughnessy 1986). Most that have addressed this question have </p><p>done so for only a few macroalgae and large grazing invertebrates and have not addressed </p><p>whole community patterns and how sand may influence the distribution of all or most </p><p>species. </p><p>Compared to the many studies on vertical zonation of rocky intertidal biota, little </p><p>information is available on factors influencing horizontal patterns, although horizontal </p><p>1 </p></li><li><p>gradients are common. Removal of intertidal organisms by seasonal disturbance provides </p><p>c...</p></li></ul>