POPULATION STUDIES OF MEIOFAUNAL OLIGOCHAETES INHABITING A CENTRAL CALIFORNIA SANDY BEACH Steven M. Lacy B. A., University of California, Davis THESIS Submitted in partial satisfaction of the requirements for the degree of MASTER OF ARTS in BIOLOGICAL SCIENCES at CALIFORNIA STATE UNIVERSITY, SACRAMENTO Abstract of POPULATION STUDIES OF MEIOFAUNAL OLIGOCHAETES INHABITING A CENTRAL CALIFORNIA SANDY BEACH _by Steven M. Locy Statement of Problem: Marine interstitial oligochaetes, although common in the meiofauna, have largely been ignored by ecologists along the California coast. Few authors, in addition, have analyzed in any detail effects of physical factors on oligochaete microdistribution. Sources of Data: Interstitial oligochaetes were extracted from monthly core samples taken along an intertidal transect at the Salinas River State Beach in Monterey County, California. Oligochaetes extracted were indentified to lowest taxon and assigned to a maturity state. Sediment samples taken concurrently were also-analyzed in the laboratory. Conclusions Reached: the beach. Oligochaetes occupied three discrete areas along Tubificids were predominant at the seaward stations. Marionina sub.terranea, an enchytraeid, had the highest densities in the middle of the beach. Other enchytraeid species representing three genera ｯｮｬｹｾＭ inhabited the landward stations. Multivariate analysis indicated that subterranea distr1bution and density patterns could be attributed to grain size. ACKNOWLEDGEMENTS I· am indebted to Dr. James Nybakken, my major professor, for his , guidance, and financial assistance during this thesis. The and assistance of the many people at Moss Landing Marine will always be remembered. In particular, I am grateful to ila Baldridge and Ms. Doris Baron for providing needed references and of course to Mr. Vidya Nerine who ｾｰ･ｮ､＠ the meiofaunal Walter J. Harman, Dr. Michael Loden, Nr. Terry Wassell, Michael , Tom Shirley, and Ms. Alice Fredlund deserve a thanks for their ,,,,..... , advice, and knowledgeable discussions in bringing this thesis end. Warm appreciations go to Dr. Olav Giere for his taxonomic advice and ｾｵｳ＠ Christopher Erseus for his correspondence and naming locyi after me, and Dr. Pierre Lasserre for unraveling many of enchytraeid problems in his writings. I am deeply grateful to Susan Chinburg, my wife, whose support and has helped me with all aspects of this thesis. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS v LIST OF TABLES • vii ix LIST OF FIGURES l INTRODUCTION • • ［ｾｔｅｒｉａｌｓ＠ 3 AND METHODS LAB EXPERIHENTS • • 5 STATISTICAL ANALYSIS 9 11 RESULTS SPECIES 11 SPECIES DISTRIBUTION 13 LAB EXPERIMENTS • • . 49 PHYSICAL ENVIRONMENT 49 STATISTICAL ANALYSIS 65 DISCUSSION 76 LITERATURE CITED 83 vi LIST OF TABLES Page Number of each maturity state for 14 Narionina subterranea in January Number of each maturity state for Marionina subterranea in April 15 Number of each maturity state for Marionina subterranea in July 16 Number of each maturity state for 17 Marionina subterranea in October Number of each maturity state for Marionina subterranea at station C . . 10. 11. 12. 13. 14. 15. 16. 18 Number of each maturity state for Marionina cf. a chaeta in January 19 Number of each maturity state for Marionina cf. achaeta in April 20 Number of each maturity state for Marionina cf. achaeta in July 21 Number of each maturity state for Marionina cf. achaeta in October 22 Number of each maturity state for Marionina cf. a chaeta at station c 23 Number of each maturity state for in January Marionina ｾﾷ＠ 24 Number of each maturity state for in April Marionina ｾﾷ＠ 25 Number of each maturity state for Marionina .!.E.E.· in July 26 Number of each maturity state for in October Marionina ｾﾷ＠ 27 Number of each maturity state for Lumbricillus group in January 28 Number of each maturity state for Lumbricillus group in April 29 vii viii LIST OF TABLES can't Page Number of each maturity state for Lumbricillus group in July 30 18. Number of each maturity state for Lumbricillus group in October 31 19. Number of each maturity state for tubificids in January . . . . . 32 zo. Number of each maturity state for tubificids in April 33 21. Number of each maturity state for tubificids in July . 34 22. Number of each maturity state for tubificids in October 35 23. Number of each maturity state for tubificids at station C 24. Seawater temperature at the surf zone 54 25. Beach slope and vertical changes from January stations . . . . 58 Arithmetic mean and range of mean grain size in phi (0) units 59 Arithmetic mean and range of median grain size in phi (0) units 61 Arithmetic mean and range of sorting in phi (0) units 63 29. Arithmetic mean and range of skewness values 66 30. Arithmetic mean and range of kurtosis values 68 31. Arithmetic mean and range of percent water 70 32. Arithmetic mean and range of sediment 26. 27. 28. temperature (Co) 33. 72 Canonical correlation analysis of seven environmental and five taxa variables . . . . . . . . . . . . . . . . . . . . . . 74 LIST OF FIGURES Page Figure 2. Modified Boisseau (1957) apparatus 6 Controlled temperature gradient apparatus 8 Population of Marionina subterranea for January 37 Population of Marionina subterranea for April 38 Population of Marionina subterranea for July 40 Population of Marionina subterranea for October 41 Population of Marionina subterranea at station C . . . . . . . . 42 8. Population of tubificids at station C 44 9. Median depth segment of Marionina 3. 4. 5. 6. 7. subterranea at each station for four months 10. 11. 12. . . . . Median depth segment of Marionina subterranea and tubificids at station C . . . . 47 Median depth segment of other enchytraeids and tubificids at each station for four months 48 Percentage of Marionina subterranea surviving at various temperatures 13. 14. Temperature preference of Marionina subterranea along a temperature gradient . . . . . . . . . . . . 50 51 Preferences of Marionina subterranea to different grain sizes at l6°C . 15. 45 52 Preferences of Marionina subterranea when placed randomly or between halves of different grain sizes at l6°C . . . ix 53 X LIST OF FIGURES can't Page Figure 16. 17. Beach profiles and station elevations for January and June . . . . . . . 56 Beach profiles and station elevations for October and September . . . . 57 INTRODUCTION The Oligochaeta, a class of predominantly terrestrial and freshwater annelids, includes a number of species which have adapted to the marine environment. Though there are marine and brackish water representatives of most families of oligochaetes, the majority of species are 1n the Tubificidae and Enchytraeidae. These worms are arbitarily divided into macrofaunal and meiofaunal groups. Macrofaunal oligochaetes are gener- ally retained on a 0.5 mm size screen while meiofauna oligochaetes will pass through this s1ze mesh. As opposed to other meiofauna that are specially adapted to the interstitial habitat, meiofauna oligochaetes have no real morphological adaptations for interstitial living other than size (Lasserre, 1971). Though oligochaetes may play a considerable role in the interstitial community (Fenchel, 1978; Giere, 1975), they are overlooked by many investigators due in part to difficulties in identification. The lack of discrete age classes has also tended to discourage studies in life history resulting in a paucity of information about population structure and breeding periods. Several studies that focus on vertical and horizontal distribution of interstitial marine communities containing oligochaetes have appeared (Jansson, 1962, 1966, 1968; Fenchel, Jansson and von Thun, 1967; Schmidt, 1969), but distribution analysis covering an entire year or more has only been reported by Lasserre (1967). Attempts to explain the distributuion of oligochaetes based solely on measured field parameters have been made by Cook (1971, 1974), Erseus 1 2 ) Giere (1973). Other works have coupled measured field parameters laboratory determined tolerances and preferences to explain ooc:Ualece microdistribution patterns (Giere, 1980; Jansson, 1962, 1968; 1971). However, attempts to correlate physical parameters with and seasonal distribution of several oligochaete species lacking. The purposes of this study were to 1) quantify temporal and spatial interstitial oligochaete populations inhabiting a tidal beach year, 2) correlate measured environmental factors with densities and distribution patterns, and 3) experimentally what physical parameters may determine the occurrence of subterranea, the predominant interstitial oligochaete. MATERIALS AND HETHODS An intertidal transect near the Salinas State River Beach, Monterey California (121° 47'W, 36° 47'N) originally sited by Narine (1977) reestablished. From a permanent datum marker, 5.3 m above MLLW , 1977) five stations, A, B, C, D, and E were established in order along a transect ｰ･ｲｾｮ､ｩ｣ｵｬ｡＠ to the During each sampling period a meter-line was laid down over face due west from the stationary marker to the water line. A was designated as 9 meters from the marker, and B, C, D, and E 21, 29, and 37 meters from the marker, respectively. sampling period was January 1976 through December 1976. The transect, stations A through E, was sampled once in January, April, , and October. To monitor short term changes, station C was addition- sampled once during each intervening month (February, March, May, , August, September, November, and December). Core samples for specimens were taken using a 50 em long plexiglass ty coring tube with an internal diameter of 2.54 em. These coring used due to their availability and ease in handling. The the tube was marked into 5 em sections by permanent marking During exposure at low tide, five 50 em cores were taken within each square sampling station. A coring site was determined by tossing a tic core cap into the quadrat. The coring tube was pushed perpen- into the sand surface to a depth of approximately 20 em, then Each 5 em section was then placed in a separate pre-labeled jar aining five percent buffered formalin and rose bengal. 3 The core was 4 into the hole to obtain the remaining 30 ern, removed, and above. Some climatic and hydrographic conditions were recorded during each period. Temperature of the seawater at the surf zone and the ern of the beach sediment was measured with a mercury-in-glass ,ennoo1eter read at 0.1°C. Temperatures below 10 em were recorded to using a temperature probe attached to a stick marked off at 5 em The probe was inserted into the sand ｡ｴｾ＠ each 5 em depth and to equilibrate for five minutes before a reading was taken. After reading the stick was pounded into the sand to the next 5 em inTemperatures were measured simultaneously during sampling in the rapid temperature changes occurring on the sand surface. One core for particle size analysis and percent interstitial water taken with a plexiglass tube 3.5 em internal diameter and 50 em in After removal each 5 ern section of sand was deposited onto a aluminum foil, wrapped tightly to prevent evaporation and sand To further avoid evaporation, samples were taken immediately to returning to the lab. profiles were to have been taken during sampling of the entire However due to fog on the horizon on numerous occasions, beach les were taken in January, June, September, and October. All pro- were surveyed relative to the fixed marker located above station A, the method of Emery (1961). The well drained nature of the prevented interstitial salinities to be taken so a hole was excathe water table at the fore beach stations. Water samples taken water table and sea surface at the surf zone were chemically in the laboratory. 5 In the laboratory the interstitial organisms were extracted using a Boisseau (1957) apparatus designed by Narine (1977) (Figure 1). least twenty minutes, sufficient time to the oligochaetes (Narine, 1977). The animals were washed from the micron screen and stored in 70% alcohol for later identification. The stained oligochaetes could easily be picked out under a standard ting scope. The worms were then transferred to a glass slide and under a compound microscope. Each oligochaete was identified to taxon and a maturity state noted. sample packets were weighed (wet wt.) in the lab. After samples were partially unwrapped and placed in a 150°C oven several days. The samples were then removed, allowed to equilibrate room temperature and reweighed (dry wt.). The difference between the weight and dry weight is the interstitial water weight of each sample. interstitial water was calculated by water weight wet weight of sample X 100. For sediment analysis each dried sand sample was analyzed by the Emery tube method (Emery, 1938). Measures of grain size, graphic mean (Mz) and median (Md)' uniformity or sorting (S 0 ), asymmetry or skewness (SK ) and peakedness or kurtosis (KG) were determined using the methods of 1 Folk (1974). Lab experiments Experiments were carried out to determine the response of Marionina !Ubterranea, the numerically dominant oligochaete, to temperature and sediment size. For the experiments M. subterranea were collected at a level in the beach in front of Moss Landing Marine Laboratories corre- 6 sea water in Figure 1. Modified Boisseau (1957) apparatus 7 to station C. The worms were obtained 24 hours prior to an and held at l5°C ｾｮ＠ filtered seawater. Only mature, healthy were used for the experiments. To test the survival of Marionina subterranea over a of temperatures, tolerance experiments were performed. Ten to worms were placed into 35 mm plastic petri dishes containing seawater. ' 10° ' The dishes were then covered and placed in the dark at 15°, 20°, 25°, or 30°C. al temperatur8. Two replicates were used for each Observations were made approximately every 24 At each reading dead worms, which were distinguished by the lack movement when touched by a metal probe, were counted and discarded. dishes were then placed back in the respective temperature compart- To measure temperature preferences, a temperature preference trough built following Gray (1965). A plexiglass tank (Figure 2) was divided three cross partitions into four water tight compartments. fitted tightly into the tank through the cross partitions. A trough At one end the tank a heating unit was secured and at the opposite end a freezing When in operation a temperature gradient from 5-30°C For this experiment a thin layer of moist sterilized sand of 2.0-2.5 size (177-357 microns) covered the bottom of the trough. placed ｾｮ＠ the trough and the unit was turned on. Worms were After 24 hours from each temperature region was removed and the live worms were counted. A Cooling coil rrrrr ｾｬ｜＠ /1 Plexiglass - 1\\｜｟ｾ＠ Heating unit -remperature trough IU ｾ｟Ｉｊ＠ D B A r------. tank - I""' B Water Figure 2. Controlled temperature gradient apparatus "' 9 Different size classes of sand beach sand. Each size class (0 ｧｲ｡ｾｮｳ＠ were obtained by sieving or phi size) was soaked in hydrogen peroxide for 4-5 days, washed in water and placed in an oven until comletely dried. p A LECO carbon analyzer indicated no organic carbon present in the sand. For each experiment a small plastic petri dish was divided in half. Each half of the dish received an equal amount of a moist sterilized sand class to completely cover the dish bottom. The oligochaetes were then placed at the boundary between the two sizes of sand. dish was placed in the dark at l5°C. Each experimental After 24 hours each sand half and the worms therein were placed in separate bowls. The worms were counted and discarded. Similar experiments were performed to determine if the preference exhibited by Harionina subterranea would change due to the intitial positioning of the worms. The procedure described above was followed except for each experiment the oligochaetes were either placed in the middle of each of the two sizes of sand or placed randomly over the two sand sizes. Statistical analysis To analyze the data, each 5 em core section of sand was considered as one case. The measured physical factors were considered the environ- mental data set. The biological data set consisted of the average number of species found in each sand section. For each set of the five species variables and seven environmental variables, a canonical correlation analysis was performed using the SAS subprogram CANCORR at Louisiana State University, Baton Rouge. The pertinent output consisted of 1) 10 nical correlation coefficients between all paLrs of environmental and can O biological variables; 2) canonical variates (CV) and 3) canonical weights or scores. The canonical correlation coefficient measures the goodness- of-fit between a composite of the pair of canonical variates (CV) which are simply the pair of data sets now statistically transformed. Each canonical variate (CV) is composed of weights or scores which measures the individual variable participation between the pair of data sets. If the correlation coefficient was significant, interpretation involved exam- ining the relative magnitude and sign of each weight or score defining each CV, sLnce there is of yet no statistical test of significance of the weights which enter each canonical variate (Pimentel, 1979). RESULTS ｾ＠ since no major taxonomic work has been carried out on Eastern Pacific coast interstitial oligochaetes, specimens were sent to Canadian and European taxonomists for identification. Species collected were found to be members of two oligochaete families, Enchytraeidae and Tubificidae. In the Enchytraeidae, Marionina subterranea (Knollner, 1935) was easily recognized by the lack of dorso-lateral setae. fication was later confirmed by Dr. Olav Giere. states were distinguished: The species identi- Four different maturity immature, adult, adult with sperm funnel, adult with developed clitellum. The smallest ｳｰ･｣ｩｭｾ＠ among 200 indi- victuals with noticeable reproductive organs was 18 segments long. Thus, any individual with less than 18 segments was considered immature and any individual 18 segments or longer was considered an adult. The smallest individual recorded was 9 segments, probably representing a newly hatched individual. Adults represented either recruited individuals from the immature state or a post-breeding phase (Lasserre, pers. comm.). Due to difficulty identifying minute internal characters of these worms in a preserved state, it was not possible to differentiate between the pre- and post-reproductive phases of this adult state. The third maturity state Were adults with sperm funnels capable of reproducing. In this state the collar of the sperm funnels of breeding individuals are normally brown due to the attached spermatozoa. The final maturity state were adults with a well developed clitellum, an advanced breeding state. The glandular cells of the clitellum, capable of forming mucus and cocoons, tended to 11 12 0ov e an r the viewing of the sperm funnels. The funnels were also hidden by increase of granular yolky material for the oocytes in the genital 8 rea. Another enchytraeid, Marionina cf. achaeta lacks setae and is similar to two meiobenthic enchytraeids described from Europe, Marionina achaeta Lasserre, 1964 and Achaeta littoralis Lasserre, 1967. Giere (pers. comm.) feels the anatomy of Marionina cf. achaeta is closer to Marionina achaeta but live specimens were never obtained for proper identification. Four maturity states could be identified: 1) immature individuals of 25 segments or less; 2) adults without sexual organs; 3) adults with sperm funnels; and 4) adults with a well developed clitellum. A third group of enchytraeids were considered together in this study. The Marionina ｾﾷ＠ group contained species closely affiliated with known European species (Giere, pers. comm.); 1847); ｾﾷ＠ ｾﾷ＠ spicula (Leuckart, sjelandica Nielsen and Christensen, 1958; M. southerni (Cernosvitov, 1937). Due to an insufficient number of live and preserved specimens further identification of the species were not ｰｯｳｩ｢ｬｾＮ＠ Since the species were not easily separated by setae position or number only three maturity states could be distinguished: 1) immature; 2) adult with sperm funnels; 3) adult with a clitellum. The last group of enchytraeids was the Lumbricillus group. Origi- nally the species present was thought to be Enchytraeus cryptosetosus Tynen, 1969 (Giere, pers. comm.). But towards the end of the study, Lumbricillus annulatus Eisen, 1904 and L. mirabilis Tynen, 1969, both species similar in external appearance to E. cryptosetosus, were found in other areas of the beach by Dr. Olav Giere. It is possible that these two species were incorrectly counted as E. cryptosetosus. Since the original 13 was discarded rendering reidentification impossible, only two states could be discerned: 1) immature; 2) sexually mature. Tubificid specimens could easily be separated from enchytraeids by presence of bifid setae. Tubificids were sent to Dr. R. 0. t in early 1976 who identified them as Aktedrilus monosper(Knollner, 1935). ｾｩｴｨ＠ At that time I was confident I was dealing this one species since this species has been reported in many meiofaunal studies as the only interstitial tubificid. Toward the end of this study in 1978 additional tubificid specimens were sent to Dr. Christer Based on these specimens Erseus (1980) described Aktedrilus locyi and identified an undetermined species of Bacescuella. Since the tubificid material was not saved only two maturity states could be recognized: I) immature; 2) sexually mature. For future work, the two species can be easily separated (Erseus, pers. comm.). ｾﾷ＠ locyi is a stout tubificid with very fine setae and a prominent spherical prostomiurn. spermatheca in segment X. Sexually mature individuals have a Bascescuella ｾﾷ＠ setae without a spermathecae in segment X. is more slender with thick Aktedrilus monospermathecus was never found in any sample (Erseus, pers. comrn.). Species Distribution Oligochaete species and maturity states are presented in Tables 123. In January, Marionina subterranea had the highest density at station C (Figure 3). adults. The population during January consisted principally of Sexually mature worms had the highest density and comprised a higher proportion of the population at station C than the other stations. During April (Figure 4) station B contained the highest number of individuals. Due to the low numbers of M. subterranea at stations A, D, and E Trtble 1. F1unber of eoch mc.1birity state for t-lnrionina suht.-:>rrHnen in LT::-muary Ecnn number A ±. 95 })Prcent cnnfir!ence ir:. t:erv;•_ls c B Immature 2.8 + 2.7 Adult 5 • ｌｾ＠ + 1.9 311.G Adult with sperm funnels 0.8 + 1.0 Adult \•.ri th clitellum 0.2 + Total 9.2 -+ Q ? c.·+ E D 1.9 o.s -+ 1.3 3-5 16.8 + 1.6 9.2 -+ 3.0 10.0 + 2.4 9.0 -+ 1.9 70.0 :!:. 3.C. 3.0 + 1.6 3.8 -+ 2.4 2.2 + 3.5 36.4:!:. 2.9 22.6 + 11.5 - 3.2 6.0 + 6.3 31.8 + 2.8 + 1.5 23.2 + 0.8 o.B + 1.3 2.7 46.1f + 7.1 + 2.2 G.6 + ｾ＠ 0 c..• u Table 2. Number of each maturity stflte for Harionina subterrnnea in April Nean number .::._ Ｙｾ＠ percent confidence intervtJ1s ｾＭﾷＱ｡＠ St0.tion turi ty state A B c D Immature 7.6 + 1.6 55. 1• -+ 3-9 28.0 + 3.1 1.2 + 1.2 Adult 2.6 + 1.6 46.0 + 2.3 l.t2. 4 + 3. ｌｾ＠ l.lf + 1.4 Adult >Ji th sperm fmmels 0.8 + 1.3 37.6 -+ 3. Lr 30.11 3-3 0.6 + Adult >lith clitellum 0.4 o.8 13.6 :!:. 2.tr 2.0 o.r. + l.l Total 11.4 + + ＲＮＱｾ＠ 152.6 :!:. lr.6 :!:_ 11.6 + 105.0 :!:.. 5.1 1.1 3.e :!:.. 1.5 0.2 + 0.8 o.6 -+ 1.1 0.4 + 0.8 1.2 + 1.2 Table 3· Number of each mnturity state for l·:arionina subterranea in July !'lean number .:t,. 95 percent confidence intervals Station l'aturity state A c B Immature 51.0 + 4.5 Adult 19.0 ｾ＠ 2.0 Adult with sperm funnels Adult Hith clitellum o.2 + Total 3.6 + 2.0 E D 3-7 4.6 + 2.0 58.8 ::':. 6.6 43.8 + 3.2 10.0+ 2.6 l07.h ::':. 5.5 57.8 ::':. 3.1 19.6 ::':. 3.6 161.2 + 4.6 71.0 ::':. 5.6 ll9.2 + 6.7 46.0 + o.B 102.0 + 5.2 30[.1+ ::':. 11.1 Table 4. Number of each maturity state for Harionina subterranee in Cctober J':ean number .:!:_ 95 ｾ･ｲ｣ｮｴ＠ confidence intervals Station ｾｬ｡＠ turi ty state Imma.ture A 14.6 c B =- 5.1 Adult Adult Hith sperm funnels I+(). 4 + ｾＮｅ＠ 3G.2 3?.6 -+ 6.2 3.6 + 6.2 - Total 22.0 + 6.4 91.6 -+ P.6 o.e + 1.9 0.2 + 7').2 -+ 7.1 5;:?.8 + '"· c 0.6 + 1.3 10.0 + 2.2 8.6 2.2 0.2 + + ::).5 3.0 + 0.9 Adult with clitellu!'l E D 122.4 + 7.e 36. 4 + 2. l1 + 1.1+ 100.2 + 5.1 o.E 0.6 -+ 1.3 1.6 + 2.0 r-:ean munbcr ::!:.. 95 percent confidence intervn.ls Ha turi ty 13 ｴｾ＠ Eonth te February Harch Eety June Imm2.ture 11·0.0 + 4.2 23.4 + 2.7 77-0 + 1;. 9 010 . //. Adult 52.0 + 7 18 .. 0 -+ 2.7 31.E + 311.0 -+ 3 ﾷｾ＠ Adult Hi th sperm funnels 1+2. 4 + 3-3 27.0 -+ 3.0 30.4 -+ 3. ｌｾ＠ Adult with clitellum 50.11 + 5.?) 11.1-1 -+ 1.9 12.4 + 3.0 9.2 + 2.5 184.8 -+ 6.6 72.2' + 4.2 151.6 + 5.0 106.6 + s.o Total IJ- .. August September 7 '7 •- • I November Immature 88.0::!:.. 5.6 75.2 + s.z 29.0 + 4.1 Adult C',8.B + ).1 92.8 6.7 35.6 Adult with sperm funnels 22.6::!:.. 2.7 30.!J + 2.8 o.6 + o .. S 4.6 + 1.2 Adult \1i th eli tell urn Total -- 200o0 :!:,. 6.0 + 203.0::. 8.5 ,_ + 3.0 ? r::; 24.2 -+ 3-9 December 67.2 + 4.1 3.P1 125.6 + ;;.8 3.2 + 1.3 18.0 + 2.2 o.8 + -+ 1.2 68.6 + 5.4 2.8 + 1.3 213.6 ::!:.. 6.5 Table 6. Humber of each r:1aturity state for l<a::-ionina cf. achaeta in Janu<ITy Nenn number + ']5 percent confidence intervals Station t-la turi ty str1 te A B Im::1nture .\clul t 1.11 + l.P Adult with sperm funnels Adult with clitellum Total 0.2 + 0.8 Lit + 1.8 0.2 + f).[!, c D ｾ｡｢ｬ･＠ 7. Humber of each r.:aturi ty 3t,"J. tc fo!' l':arioninn cf. acha_etG in April }lean nur:1ber + 95 percent con::"·Llr:nce intervals Station l':a turi t,y state c R D o.E Immature 1.0 + 1.3 - 1.6 + 1.6 0.4 Adult o.J+ + o.e 3.0 + 1.8 o.J, + o.S Adult \-Ji th sperm funnels o.S + + 1.2 Adult v;ith clitellum Total ｾ＠ ｾ＠ ( _ . (._ + 1.7 4.6 + 1.7 o.B + 1.0 N 0 rrable 8. Number of en.ch maturity state for 1'--iarionin:; cf. nchaeta in July l"lean number .:t_ 95 percent confidence intervals St,., tion ｾ｡＠ Maturity stn te A Immnture 0.2 + Adult ＳＮｌｾ＠ c B o.C: + 2.6 ｾ＠ 7 3.0 + L- • 2.2 1 .. 7 -+ ;J Adult vdth sperm funnels o.S Adult \·lith clitellum 0.2 + 0.8 5.0 + 2.E 4.6 + l.l - 10.2 + 3.3 tal + 1.3 D E To.ble 9. Number of each r.iaturity state for t:larionina cf. ach:1eta in Cctober l-1ean number ｾ＠ 95 percent confidence intervals Station E;,turi ty state A Immature 3.'+ + 2.2 Adult 3.4 + 2.1 6.8 + 2.8 c B D E 10.2 + 3.2 - 1.6 + 1.1 Adult Hith sperm funnels Adult with c1itellum Total 11.8 -+ 3.8 N N Table 10. Number of each maturity ｾＺ［ｴｱ･＠ Nean number ｾ＠ for F1nrionina cf. nchaeta. :ott station c 95 pP.rcent confidRnce intervals l1onth Maturity state February Immature l.L; + 1.1 Adult o.z May June November December + o.B Adult \·d th sperm funnels Adult with clitcllurn Total 1.6 + 1.2 August Se1=1ternber Immature o.LJ. + o.8 Adult 0.2 + o. 8 o.G + 1.1 Adult v1i th sperm funnels Adult with clitellum Total 0.6 + 1.1 0.6 + 1.1 N w Table 11. Number of e::tch ｾﾷｩ･｡ｮ＠ ｭｾｴｵｲｩ＠ ty state for llr1rionina ｾﾷ＠ in J::1nuary number i_ 95 percent confidence intervals Station Nturi ty state Immature A B 4.2 :!:. 1.9 Adult ;1i th cperm funnels Adult v1i th eli tell urn Total 5.6 + 2.4 c D E r:I'able 12. Number of ea_ch r:1a turi ty state for Earionina ｾﾷ＠ in April l'<ean number .:!:. 95 percent confidence intervals Station J··;n turi ty state ImmG..ture A l3 ｾ＠ 0 13.2 -+ '-· 0.6 + o.B (' o.2 + 1.0 0.8 + 1.0 c D E Adult with sperm funnels Adult vith clitellum Total 13.<5 + 2.8 '" \J> r.rable 13. Number of each mctturi ty state for l-:arionina snp. in July Neun number :!:.. 95 percent confidence intervals Staticn ｾＧ｡ｴｵｲｩ＠ A ty state c B ·- Immature 5.2 Arlul t r.ri th s;:·erm funnels 0.2 + o.i', Adult vii th eli telluro 0.2 + Total 6.2 + 1.3 + l l?.h + 1+.5 - 7, o.C. 6.e ｾＭ｟［Ｎ＠ Lt.• 'JO + 0.2 + D E o.e ?.9 P + 1.7 :J ,_ + s.r, N "' rean number + 95 percent confidence intervals 0tation ［ｾｉＡ＠ Imr1e1 tlwe Adult. vii th ｾ＠ !'F'Y' m fli;ll1Clr. c ;\ i<a tur i ty sti'l te • (. + ,'? .1+ r\. B + 1.5 F.1"- + 2.3 + n.g (.6 + 2 .. .3 0 -, I,/., ( • Adult •..:i th elite llun Total 25.6 + 2.0 f.:ean number + 95 r·ercent cnnficlence intervals Stotion n l:aturi ty stnte Imma_ture c D 3.2 ±. 2.9 .Sexually rna tur e IJ:otal 3.2 + 2.9 N "' Table 16. Number of each r:J,'lturi ty ｳｴｃｾ｣＠ J.lean number + 95 for Lumbricillus crDU]J in otpril nercent confidence intervals Station Eaturity Ftate A B c D Immature Sexuall,y Total ｭｾ＠ ture o.I• + 1.1 ?.f' + ｾ＠ ｾ＠ ,-_. L N "' ｾＺｴ｢ｬ･＠ 17. Nur:1ber cf cnch r!aturity state for Lumbricillus group in July Ncan numher :!: 95 percent confi(]ence intervals Station Haturi ty state A B 2.6 5.2 Sexually mature 3. 1f .:!:.. 1.9 1.0 + 1.3 Total 8.6 + 2.8 4.4 + 2.1+ 3.ll. D E :t_ 2.1 Immctture + c w 0 Table lf. Number of each maturity state for Lumbricil1us group in Cctober t-·Jenn number .::!::. 95 percent confidence intervFJ.ls Station J':aturi ty state Immature Sexually mature Total B 12.6 + Lf.l o.'+ + 1.0 13.0 + '+.1 1.2 :!:_ l.O 0.2 + 0.8 c D E Table 19. Nur.Jber of each maturity Hean number 2:. ｳｴｾ･＠ for tubificids in January 95 percent confirlcnce intervals Station I-:a turi ty state Immature A c B D 6.6 + 2.2 lf. 2 + 1.2> 7.0 + 1.7 6.6 ') + '-·•L 4.8 -+ 1.P 7.0 -+ 1.7 Sexually mnture Total ') w N Table 20. Number of ｲｾｮ｣ｬＭｉ＠ m:tturi ty f',tatr: for tubificids in April I'-\ean number .:::_ 95 percent confidence intervals .Stn.tion Haturi ty state Immature Sexually matlrre Total c B ?;).h 6.0 29.4 , D 5.3 '}0.11 + 2. " + 2 .. 3 3.!+ -+ 0.8 , 5.8 j 33.8 + 2.LJ 10.0 + 2.0 10.0 + 2.0 0.2 + o. 8 0.2 + o.t, 0.4 + o.6 w w ｾ｡｢ｬ･＠ ｾＱＮ＠ ｉｩｵｲｾ［ｌ･＠ of P2Ch n<:1tnrity ntnte for tubii'icicls in t.Tulj' Hean nnmber :!:.. 9;. pcrrent cnnfi('lcnce intervo..ls ｳｴｾ＠ }·:at uri ty state tion c "-' Imr.1:1_ture P.o + :;.B 17.2 + 3.1 - Sexually mature 1.6 1.7 1+.0 + 2 I·' Total ().G -+ -+ ｾＩﾷＭＧ＠ 7 n 1,7 .6 + - Y·.O ｾＱ＠ . .. 2 + 3-7 36.4 0.4 J.!-7. G + - 1+.0 36.F + 1;.6 + l.l + f.J .. 7 Table 22. I·Tumber of eP:ch ｲｾｮｴﾷｩ＠ t:y r.tr:tc .for tnbificidr:: in Cctober ｾｉ｡＠ Station turi ty sb te c ll Immature 5.4 + 3.1 .Sexually mature o. 11 -+ 1.1 r::'otal 5.2 + 3.2 s.o -+ 2.5 14.6 ,5.0 + -, <; .:...,._, 14.6 -+ 2.0 + E D 2.0 E2.6 + ｾＮＸ＠ 22.6 -+ 11.2 63.2 + 3-9 63.2 + 3-9 Table 23 .. Number of each matLLri ty Hean number .:!.:. 95 ｾｴ｡･＠ Honth February 0.8 + 1.3 o.P + 1.3 l<a:r ｾＭＧＺ｡ｲ｣ｨ＠ l9.0 + '+.;:?. o.6 Sexually mA-ture Total C percent confidence intervals Haturity state Immature ｳｴ･ｾｩｯｮ＠ for tubificiC:::; at + 1.1 1(1.6 + 11.1 lTune ').8 -+ 2.0 1].0 + 1;,.G + - :J.l 5.e 23. !r + 3.2 - 2.9 -+ 3.1 111.8 + 3. !r December 4.o Imrno t.ur0 ＱｾＲＮ＠ Totnl '+2.? + 1+.. 0 + 37 t'\ I E 320 Total population 300 Immature 2eO Adult u 0 II\ 0J Ul ,,_. / Adult with sperm funnels 220 Adult with clitellum 200 .-I rJ ...,"' 1Eo <=! •rl <lJ 160 " 11'0 u CJ 't •rl """' " 0 u 120 Ｂｾ＠ II\ C• ..., 100 ,.<=! ·rl ,,:> Eo ""'"' 60 +-' ·rl ,:::, 40 /// 20 / -+------!-, ........·+· ..........ｾＭＮＬｨ＠ -- -·- -.-- ｾﾷｪ＠ ｾＭＺＮ［＠ <........ . . . .·:...-· / 0 <=! 0 ... ::.· .... 100 ·rl +' "'p. .-I " 0 p. Eo 60 'H 0 "' "' biJ +' <=! 40 <lJ 20 " 0 u ,_. p. __.-, ----- - .... .... .... .... .... .... '------------- ...····,•' A ····· ····· c ····· D Station Figure 3. Population Of Earioninu. subterranea for January, 1976 38 320 300 ,, I E (.) 0 tr\ "' .-'::1 ro 200 > H Q) +' " ·.-I Q) (.) " ＠ｾ '" 14C 'H "u 0 Ｍｾﾷ＠ u. Lf\ 0'· :5 ·.-I ...,"'ＺＭｾ＠ E ·.-I "" "' ;::, /A-- ＭｾＮ＠ .· ,, ... ·1··· ... .... .. .. ＬＮｾＭﾷ＠ 2 ｾＭ ｯｾＭｲﾷ］＠ "0 ·.-I / / .· /•' ...., ·.. ' ·· ... ' .-·--t--·-·-. ---. 100 +' ro rl [ Eo 0 H 'H 0 60 20 -------... ... o ｾＭ］ﾷ｟Ｎｲ＠ A -----------, ... ··············· ·-__·-__ﾷＭｾ］ｲＧ B ｾﾷ＠ c )..:_" .-· .... ·-;...·:.:-·.-.::.., ' ............. D ' E Station Figure 4. Population of l<arionina subterranea for April, 1976. Legend in Figure 3 39 little can be concluded concerning maturity states. During April at stations B and C the population was composed of equal proportions of immature, adults and breeding individuals. In July (Figure 5) the greatest density of M. subterranea for the entire sampling period was 3 found at station C (av. 308.4 ± 11.1 indivs./250 cm ). During this month the maturity states remained proportionally similar at stations B to D. In October (Figure 6) all stations showed a decrease in total density from July. At this titne the population was dominated by immature individuals and adults. The monthly sampling at station C (Figure 7) indicated three population peaks during February, July, and December. Although total density increased during these months, the maturity states changed proportionally less severely throughout the sampling period. For example, immature individuals of M. subterranea had the greatest population densities in May and July, with low densities in June and November. But the percentage of immatures for the total population remained essentially unchanged during these months. Breeding individuals, or adults with sperm funnels and adults with a clitellum, had high densities in February and July. However these individuals constituted similar proportions of the total population from January to July. Adults occurred in high densities from August to October but comprised a greater percentage of the total population from September to December. The other enchytraeids were confined to the upper shore stations (Tables 6-18). The highest densities occurred in October. Marionina cf. achaeta had a high density at station B (av. 11.8 ± 3.8 indivs./250 cm3 ) while densities of the group Marionina ｾﾷ＠ and the Lumbricillus group 3 were highest at station A (av. 25.6 ± 2.0 indivs/ and 13.0 ± 4.1/250 cm , 40 320 300 "' I E 220 I 0 0 U\ CJ 220 Ul 200 rl ""' h Q) \ I \ 1f,Q -1-' .::: •rl Q) u 160 .::: Q) '0 •rl 140 '".:::' 0 0 120 ""' lf\ c' .G 100 : -1-' . j.. ·.. •rl > , Eo -1-' . •rl {/] .::: U> ··. 60 A 40 20 0 .::: 0 ·rl 100 -1-' 'g," rl 0 h 2o 60 'H 0 U> "" / // 40 ... :....ｾ＠ ..... . <1i -1-' .::: U> 0 20 h U> p., 0 ｾＮＺＭ｟Ｌ＠ A .·,ＮﾷｾＬ＠ ---------- Ｌｾ｟＠ / ·-· -·-·-·-·-·-·-·-·-·-·-· 3 c D ·' -- -- E Station Figure 5. Population of l. :arior..ina subterrnnea for July, 1976. Legend in Figure 3 41 320 300 "u I E 0 U\ 220 UJ .-i 200 "' n ? h '<!" +' 1E0 ﾷｾ＠ <1! 168 " 140 u CJ "D •rl ''0<! u ,, Lf C" ""' +' •rl >- ?, +' .,.; ｾ＠ (fj <! 6c 4u 20 0 " 0 •rl 100. +' ｾｪ＠ .-i ""' 80 '"0 60 " 40 0 ｲ］ｾ＠ LO " u" +' (IJ h .._ --- -- ------ 2 / (IJ ........... ·.:.: .::. :·.::.··:::.: ·::.::·7..:-:: ..... -..... . ,::., 0 A c D E Station Figure 6. Population of Earionin3. subterranea for October, 1976. Legend in Figure 3 42 320 300 -- 22.0 "' I E () 0 Lf"\ N 220 200 111 r-1 ,. +' "''" " rl •rl 1t0 1 Co (!) u "'" c(i 140 ·ri 'H " 0 c.; 120 "• ii\ a . 100 .c +' •rl f.o ::.: ?·, +' •ri {!; "'" 60 0 40 20 -·-·- ........ 0 ;·..j·-·-·-1.-" . .+.' _,. \ ..... ·k t•'" ·. ·.. ·.'1 ., ·,., ....... ＭﾷＡｾＺＮ＠ ..ﾷＮｾ＠ . .· l 100 2c 6c - / /- ......... _,.......- ｾ＠ / .__/ 40 20 F F A J J .L. s c D Figure 7. Population density of Marionina subterranea at station C. Legend in Figure 3 43 respectively). Specific life history information cannot be derived due to the low number of individuals. ｾ･ｲ＠ Generally, sexually mature individuals most abundant during July with high densities of immatures during October. The tubificids, Aktedrilus locyi and Bacescuella EE·• were always found at station C and generally confined to the lower beach stations (Tables 19-23). In January small populations appeared at stations C toE and were composed of immature individuals. densities increased at stations B through D. During April population Sexually mature individuals accounted for almost 20% of the population in July at stations B and C. In October the population was again composed solely of immature tubificids. Sexually mature individuals accounted for a large percentage of the population from May to July at station C (Figure 8). However the popu- lation density remained relatively stable except in November and December at this station. Analysis of vertical distribution of any meiofauna species is complicated by population migrations 1n response to environmental changes caused by the flooding and ebbing of tides, wave action and climatic factors (Boaden, 1968; Boaden and Platt, 1971; McLachlan, Erasmus and Furstenberg, 1977). Thus vertical patterns discussed here reflect general trends rather than exact relationships. Median depth segment can be used as a numerical indication of the vertical depth population. The median segment depth is the 5 em segment above which and below which 50% of the population was recorded on each sampling data. Marionina subterranea appeared to exhibit distinct seasonal vertical trends (Figure 9). In January the population was found closer to the 44 320 Tote.l populc:tion 300 "'Eu I -- 2E 0 Lr\ N U] rl "'-< "' I!Tlm::lture ----- Sexually mnture 220 2CC ? <I! +' 180 •rl <I! u "'"' "'cu 'C •rl 'H 160 ＱｾＰ＠ 120 '" Lf\ ｃｩｾ＠ c' "' 10 +' ·rl Ｔｾ＠ ",., Eo •rl ""' QJ C\ 4 20 0 10r "' "p+ 0 •rl +' E, rl ｾ＠ 0 p, 'H 0 <I! 60 "" 40 bD cj +' "'u QJ 20 ' "' H QJ P< 0 F J ｾＺ＠ ;; E J J A c s 1•1onth Figure 8. Population of tubificids at station c F D 46 surface at the landward stations, penetrating deeper as one proceeded seaward. In April and July this pattern was reversed. The population at the landward stations were found deeper while seaward individuals were closer to the surface. Thus two seasonal cycles seemed to exist. At the landward stations the population was found close to the surface in winter but as summer approached the population was found relatively deeper. At the seaward stations, C and D, the population was found deeper in winter and distributed close to the surface as summer approached. If a seasonal trend was apparent it should have been reflected during the more intense sampling period. However median depth segment of Marionina subterranea determined at station C (Figure 10) indicated no seasonal trends. Differential vertical distribution of the four maturity states during each month varied no more than 1 depth segment (5 em) from the total population distribution. The other three enchytraeid species or groups showed similar distribution patterns (Figure 11). In contrast to Marionina subterranea, at station A the populations were closer to the surface in January but deeper in April. In sharp contrast ｴｯｾＭ subterranea, during July and October the populations appeared closer to the surface relative to April. At station B, during January these enchytraeid species did not occur, but a few individuals were found quite deep in April. Distribution patterns in July and October at station B were similar to distribution patterns exhibited ｢ｹｾＭ subterranea. Tubificids showed a complex seasonal vertical distribution (Figure 11). Individuals were found at station A in July only at low median depths. At station B tubificids occurred only during April and July. station C the tubificids were deeper compared to these four months. ｾＭ subterranea during At 47 0-5 • E 0 10-15 d ·rl "'p. +' "' d "' "'ｾ＠ "d 20-25 ·rl 30-35 40-45 Q J ｬＧｾ｡ｲｩｯｮ＠ subterranea F A J Tubificids J A s c N D Eonth Figure 10. I::edian depth segi!Ient of Hnrioni na subterranea and tubi- ficids at station C 48 !·:ontr. Vediar. Cepth in em. Jan April July Cct I ' 0 D 0 5-10 A 15-20 - - 25-30 - - 35-40 - - 0 0 0 D 0 0 0 [:; 45-50 - 15-20 - - 25-30 - - 0 35-40 - i- 0 - B 45-50 - ,.. 5-10 - r- ' '-J 5-10 - D 0 [:; 0 0 1,5-20 - - c 25-30 35-LO - ,.. - 5-10 - - 45-50 - 15-20 D - 25-30 35-40 - - 45-50 - i5-10 - 115-20 - 'E 25-30 - - 35-40 - - 45-50 - - Figure 11. Hedian depth segment of other enchytraeids and tubificids at each station for four months. 0 l-:2.rionina cf. achaeta; nina spp.; D Lumbricillus group; !:::. tubificir1.s 0 ＿Ｍｾ｡ｲｩﾭ 49 Median depth segment patterns for the tubificid population at station C during monthly sampling periods (Figure 10) indicated widely fluctuating depths of population concentrations. Again no seasonal patterns can be discerned from these data. Laboratory Experiments Temperature. subterranea Temperature tolerance experiments using Marionina (Figure 12) indicated survival was poorest at 30°C. As the experimental temperature decreased survival increased with no mortality up to 6 days at 5°, 10°, and l5°C. The temperature preference experiment (Figure 13) showed the majority of M. subterranea, 62%, preferred the temperature regime 16-20°C. Sediment. Binomial analysis between two halves of each sediment preference experiment (Figure 14) indicated the worms chose 2.0 or 2.5 ｾＨＳＵＴＭＱＷ＠ microns) sand over the other sand size choices (Student's test, ｐｾＮＰＵＩ＠ ｾ＠ There was no significant preference by M. subterranea when offered other sand sizes during an experiment. Analysis of the initial positioning experiments was performed on the total results of the two sets of experiments (Figure 15-lower graphs). Regardless of the positioning of Marionina subterranea at the start of an experiment, either between the two halves of sand or randomly placed over the sand halves, the preference of the oligochaetes remained the same ＨｐｾＮＰＵＩ＠ Physical environment Temperatures of the seawater at the surf zone (Table 24) showed a maxima of 15-17.5°C from July to December. l40C were recorded from January to June. Cooler temperatures of 10.8°These values are similar to 50 • • n=10 Replicate D 0 n=10 n=10 25° 30° Temperature n=10 ...6 Renlicate n=9 n=11 r:'er:1perature 20° 30 20 10 2 1 4 3 6 5 Days IZI rl ｾ＠ ·rl > H " tD "' "' b!: <1! +' 30 • n=16 •n=10 •ct=7 20 D n=11 Qn=13 Dn=10 1 50 <lJ () H (!) r:c, 15° 10° Replicate ｾ･ｲＺＱｰ｡ｴｵ＠ 0 1 2 4 3 Days Figure 12. Percentage of ｽｾ｡ｲｩｯｮ＠ various ter.1peratures. " --' subterranea surviving at 6 51 6n 5'J tD rl Ｔｾ＠ m ;J "•rl:> ·rl " <=: 30 •rl 'H 0 f.., "' .n E 2 201 10 6 8 10 12 20 22 Temper8ture along sradient (°C) Fic;ure 13 .. Temperature preference of Harionino subterranen along a ｴ･ｾｰｲ｡ｵ＠ sradient 52 Figure 14. Frsfc.l"ences of !-:sr·io:1ine1 subterrG!1ea tc dif:'o:rent gra.in sizes at l6GC 53 10 0 n=31 n=19 i7 E0 " 0 :; " 6D c ｾ＠ ｾ＠ 4c "u0 t t- 20 "' 0 Sediment size ( mrn) · Phi size .50-.3:;L. 'I 1.5 .25-.177 .50-.354 .25-.177 2.5 100 ,., .50-.354 .25-.177 Worms -- n=19 ｲ｡ｮ､ｯｾｹ＠ placed Eo u " 60 0 " ｾ＠ 0 c 40 "c• 20 "' 0 ｾ＠ ｾ＠ u u Sediment size (col I .50-.354 Phi size ¢ .25-.. 177 1.5 2.5 ｾ＠ I -50-.354 .25-.177 1.5 crouneC in ｾ＠ 10C ,, Eo "u 60 u ｾ＠ "u""c 40 ｾ＠ " u "" u u c Sediment size (me) Phi size ¢ Combined results 20 0 .50-.354 .25-.177 .50-.354 1.5 2.5 1.5 ｾ＠ .25-.177 2.5 Grouneci in ｾｲ＠ Figure 15. Frefereace of 1-:a:rioninR. subtcrranea v:hen :rl2-.ced randomly or betvTeen ｨｾＱＮｬ＠ ves of different grain sizes at 16°C 54 Table 24. Seauater ter.lpe,-.atu,-.es at the surfzone Temperature (Co) 14.0° 14.5° 14.0° 1_3.0° 11.9° Date sampled l/27 lL!OO l/27 1600 l/28 l30E: l/28 1417 l/29 1630 ?ii!ie Temperature (Co) 14.0° 13.0° Date sa.mpled 2/27 1600 3/25 1335 Tir.Je (Co) ｾ･ｲＮＱｰ｡ｴｵ＠ Date sampled Time 10.8° 12.8° 12.8° 12.1° 12.1° 4/16 0630 Lf/19 0745 4/19 o845 4/20 0830 4/20 0930 ture (Co) ｾＺｲ･ｭｰ｡＠ DE,te sampled 12.0° 14.0° "/"1 ' o2oo 6/30 0900 / ']'' -1ffi8 Temperature (Co) 11!.90 15.0° 15.0° 16.0° 16.8° Date sampled Time 7/27 0705 7/27 0755 7/2f, 0748 7/28 oE52 7/29 1135 Temperature (Co) 17.0° 17.5° Date sampled 8/24 1C:3o 9/27 oE48 Time Ter:1pera ture (Co) Date sampled Time 17.0° 16.5° 17.2° 17.2° {, oO l__,.c, 10/20 1645 10/20 1745 10/21 1500 10/21 1610 10/22 1640 Temperature (Co) 16.0° 15.9° Date sampled Time ll/17 1445 12/16 1405 55 those recorded by Lasley (1977). His results indicated that from January to April sea water temperatures ranged from 10-l2°C, with May ranging from 12-l3°C. In June the bay waters warmed to approximately l4°C and from July to December the temperature ranged from 15-l6°C. The beach profiles taken once during the months of January, June, September, and October are presented in Figures 16 and 17. To better quantify the profiles, Table 25 indicates the change of slope and vertical position of the five stations in relation to January's measurements. The shape of the beach appears to fall into two profiles related to climatic conditions. In June the gradual slope and increased beach height indi- cated that sand deposition occurred reflecting summer conditions of smaller waves redepositing sand removed during the storm period (Bascom, 1964). In September and October the beach seems to have been eroded resembling the profile in January. This period of steep beach slope formation developed during the storm period (Fox and Davis, 1978). However, all the slope measurements are characteristic of exposed tidal beaches (Bascom, 1964; Pugh, et al.; 1974) reflecting substantial wave energy prevalent in Monterey Bay (Dittmer, 1972). Average mean and median grain size values (Tables 26 and 27) fall within the coarse (0.0-1.0 0 or 1000-500 microns) to median (l.0-2.0 500-250 microns) grain sand as defined by Folk (1974). 0 or The emergent pattern of average mean and median grain sizes indicated the coarsest sand occurred at station E except in January. Additional horizontal and seasonal patterns of average grain size previously found in this area (Dittmer, 1972; Narine, 1977) were not observed. Average sorting values (Table 28) indicated stations D and E were slightly more poorly sorted than the back shore stations. Poorly sorted A ' ' \ ', ' ｾ＠ " "' P< 0 rl c 'r . . . . . " 2 " .................... " <D D .-'" u m "' p June B January 3 'H 0 ｾ＠ +' bO •rl ::c"' 4 --- - -- --- 5 -- L----+----+-----f-----+----+----+-----t----"t-----r---""-HLl.\V 5 11] 15 25 30 35 ljQ Horizontal dist0.nce from fixed mr1rker (m) Fic;ure 16. Beach profiles and station elevations for Januar:r and June 1 '0- \ A \ ｾ＠ £.: ' ｾ＠ L B A ｾ＠ "' p., 0 r1 m ""u "' 3 <1l D c .0 'H 0 +' "" 4 h.O •rl "' Sep teiT.ber iJ:: 5 5 10 15 20 25 30 35 4o Horizontal distance from fixed marker ( m) Fir;ure 17. 3each profiles and st<J tion elevations for Cctober ancl September 50 Table 25. Bench slope and vertical chanGes from t.Tanuar,y sto..tions honth June January Station Percent slope Percent slope October ｾＩ･ｰｴｭ｢ｲ＠ Position ｣ｨｮｾ･＠ Percent slope FoEition change Fercent slope Position ( crJ) (em) change (em) A 22 10 +60 22 0 22 0 B ll 10 +75 15 -20 16 -20 c 10 10 +?Po 10 -21+ 12 -26 D 9 15 +6? (' c -22 10 -30 E 9 15 +11+ 9 -16 9 -2lt Table 26. Arithmetic mean a.nd rr1nc;e of mean grain size in phi (¢) units ｾｴ｡ｩｯｮ＠ Honth January Nean Ranc;e Febrnary A B c D E 0.94 0.39-1.59 1.'''' 0.83-1.91 1.10 0.33-1.511 1.27 0.94-1.61 1.27 0.39-1.64 0.61 0.00-1.03 0.38 0.23-0.69 o.B5 0.39 -.32-1.09 J.:ean 1.06 0.63-1.57 l·:ean 0.73 0.23-1.16 ｒ｡ｮｾ･＠ Narch llanr;e April Mean Range Eay June 1.20 0.31-1.59 o.B3 0.00-1.311 He an Hange 0.66 o.40-l.1B l-\ean 0.21 -.02-0.79 Range Jn1y August 0.59 o.zS-o.9e l,':ean Rance He an Range 1.20 o. 2.1+ 0.33-1.65 0.00-1.57 1.15 0.61'-1.71 o.Y:i-1.53 1.20 0.611-1.67 "' "' Table 26 (continued) Station l:onth September A B nean c D E 1.32 0.26-1.20 0.21-1.51+ 1-57 0.']2-1.99 October !'-lean Rane;e 1.26 1.5P, 0.51'-1.83 o.9E-2.00 o.P'6 1.112 0.90-l. 79 Novcrr.ber Decernb8r 1.19 o. 71-1.5[f f.: can Rc:n1r;e 1.49 o.C'8-1.2E 0 "' Table 27. ArithMetic mean and ｲｾｮ［･＠ of mr?rlinn. r:;rain size in r;hi (¢) units ｅｾｴｮ＠ B l-lonth 1:e0n Tbnc;e 0.99 0.25-1.63 1.55 0.9tl-2 .Ol February tion c l.lO o.m-Lct1 0.55-1.66 l:ctrch I:ecm Rane;e o. 7l -.02-1.32 April F (;n_n Un.nge ｾ｡＠ 1.20 -.07-l. 67 O.Ol -.21-J.II:'· Lean nee August 1.41 0.00-l. Ｗｾﾷ＠ Eenn Rant;e -. 03-l. 21+ 0.09 -.05-0.63 Ci.7F' -.05-1.61 -.Ol-1.311 O.hO 0.12 J.iean re::tn rt:.'tnge n .. _r:;? -.02-l.ll 0.2/_l·-1 .. 30 -.05-o.E:E Rrtnce July 1.t14 l.0£.-1.('? 1.16 Range June D 1 ...ｾＱ＠ 1.2.9 -.05-l. ?if -.18-1.61 0. h5-l. 71+ 1.30 0.46-1.80 n. ::P. Table 27 (continued) Station Fonth September B Nean .Rnnce November December E o.97-2.05 1.26 o. 71-1.60 1.33 0.59-l.C.,3 1.67 1.16-2.06 t:e2.n 1.50 Ranc;e 0.98-l./',6 J:lean 1.59 1.00-2.00 Ranse D 1.64 He an Range October c 1.311 o.87 -.04-1.84 -.04-1.75 ·Table 2S. Arithmetic mean ;mel rcmr;e of sortinr; in phi (9J') units Station llonth January l<ean n,mc;e Februrtry He an Range A B c D E 0.70 0.53-0.86 0.59 o.I+o-o. 83 0.69 0.1+5-0. 82 0.75 0.55-0.90 0.77 0.58-0.93 o.PS o. 73-1.01 0.96 0.90-1.02 0.75 0.59-0.89 0.46-1.00 o. 71+ 0.53-0.92 ＰｾＸＲ＠ He an ｾＺ｡ｲ｣ｨ＠ Range April J.·;ean Range liay o.GP.-0.93 0.75 o.Gl-0.92 0.73 0.56-0.1.'3 0.78 o.6o-o.86 l<ef'l.n Range June J,·;cBn 0.55 0.30-0.78 Hange July He an Hange Au[plst He an Hange 0.81 o. 71f-0. 86 0.76 0.65-0.91 o.G4 ｯＮｌｾＭ＠ .. 82 0.56 0.32-0.70 0.78 0.71 o.Lf5-o. 89 "'w Table 2P. (continued) Station ｬｾｯｮｴｨ＠ September A ｾ･｡ｮ＠ Range December c o.66 0.61-0.29 0.62 0.1+2-0. 83 0.53 0.38-0.77 1-:ean Range 0.60 0.34-0.85 ｴｾ･｡ｮ＠ 0.60 o.lf0-0. 91 Range D E 0.60 o.t;3-o.87 0.87 0.66-0.98 o.6o 0.39-0.89 t::ean Range October T'1ovember B 65 material generally has mixtures of grain sizes while well-sorted sediments have narrow ranges of gra1n s1ze. Skewness values (Table 29) indicated that in April and July the landward stations were coarsely skewed or contained an excess of coarse sediment than the seaward stations. Average kurtosis or peakedness measurements (Table 30) fall within the range of natural sediments (Folk, 1974). The distribution of pore water (Table 31) indicated the highest amounts of interstitial water were always obtained ,at station E and generally decreased toward the landward stations, a general occurrence observed elsewhere (Salvat, 1964; Ganaptai and Rao, 1963). At the time of sampling low values dominated the sand surface at the higher stations and showed the greatest variability in water content. Average monthly sedi- ment temperature (Table 32) from January to May ranged from approximately 10-l4°C. Average sediment temperatures were warmer from June through December falling between l4°-l9°C. The rapid drainage of water during the low tide did not allow chemical analysis of the interstitial water. It was necessary then to chemically analyze the water table during low tidal conditions. The few data do not allow any comparison of nutrient values, but generally salinity values were similar to oceanic values. Statistical analysis Canonical correlation analysis (Table 33) indicated only the first canonical variate pair (CV) had a significant canonical correlation coefficient ＨｐｾＮｏｓＩ＠ The physical variables, mean and median grain size and the taxon group, Marionina subterranea, had scores or weights relatively high compared to the other variable scores which permits us to Table 29. Arithmetic mean and range of skeNness values Station Eonth B January t.iean Ilange February 1-:ean -.0') --35-0.34 -.27 -.36-(-.16) He an Range -.17 --37-0.53 -.13 -.55-0.51 0.13 -.26-0.52 He an Range 0.11 -.25-0.35 June I·1ean 0.43 -.12-0.67 Rnnge ｬＧﾷｾ･｡ｮ＠ Range August Nean Range -.30 -.52-(-.1')) -.22> -.55-0.52 0.')0 -.2')-0.58 0.38 0.0')-0.60 0.13 0.27 -o3l-0.56 -.3')-0.52 t··:ay July E o.Lfo 1-'iean Hance April -.0') -.33-.051 D -.20 --39-0.13 Range !·:arch c -.21 -.35-0.51 -.05 -.26-0.If2 -.13 -.30-0.1') -.32-0.62 -.41 -.46-0.35 a-> a-> Table 29 (continued) c;tation J.:onth Gepter:1ber A B Eean Range November He an Range December D -.20 -.30-(-.0l) J·:ean Hange October G -.llf -.30-0.0I+ -.12 -.23-0.12 -.1? -.28-(-.03) -.17 -.34-0.02 1.ee.n " -.23 R::tnc;e -.1+2-0.00 -.06 -.25-0.60 (). 211 --39-0.58 Table 30. Arithmetic mean and range of kurtosis V?,lues Station B JanuEJry February lcarch April Eean Ranr;e 0.22 o. 70-1.08 0.9B o. 70-1.21 c D o.m 0.92 (). 65-l.ll 0.97 o.6n-1.3P 0.79 o.6Lf-l.50 o.e.o 0.69-0.95 o • .S6 1.00 0.63-1.75 0.61-1.11 n. E'2 Henn Range 0.60-1.10 !·Jean Range 0.78 O.h5-0.()3 ｴﾷｾ･ｮ＠ 0.')0 Range 0.76-1.22 0.90 0.59-2.11 0.75 0.6()-1.03 Nay l·:ean Hange 0.7h o.GS>-0.79 June l,:ean Rn.nc;e 1.80 0. 77-Lt.24 July Lean ｾｻ｡ｮｧ･＠ August Eean Range 0.96 0.64-1.22 o./38 o.G9-1.32 o.BS 0.66-1.05 0.70-1.20 0.83 0.62-0.96 "'"' Table 30 (continued) Station Honth September A B t·1ea.n Range Novel!lber December E o. 85 0.61-1.06 0.78 0.63-l.Ol o.6I•-l.l6 0.90 0.65-1.04 0.87 0.90 0.68-1.26 o. 77-1.12 Range 0.88 0.75-1.00 t·:ean Range 1.00 0.75-1.61 l-'iean D o.E9 Vie an Range October c Table 31. li..ri thmetic mean and range of percent \,rater Station Honth January l·:ean Range February A B c 2.4') 0.66-').84 3.10 2.12-6.35 4.90 2.Lf4-9.17 l!ean Tiange 5.36 3.95-7.00 4.20 2.78-6.(.') 3-90 2.13-11.')8 !fay lie an Range 5.30 3-21-7.01 June t··ie.3.n lf.')O 2.79-8.68 Hange July August 1-!ean Hanr;e He an Range 16.1+0 8.40 3.89-11.52 l5.2Y-l7.93 5.00 2.63-7.98 He an Hanr.:;e April E 5.50 3.16-9.67 Nean Range };arch D 2.40 o.6o-4.16 Lf.OO 2.72-2.12 5.20 3-51+-2 .10 5.70 3-71-9.42 5.30 3.32-E.29 11!.60 13.41-111.86 6.30 3.58-12.51 7.80 3-17-13.90 __, 0 Table 31 (continued) Station B September ｴﾷｾ･｡ｮ＠ Range November December l'iean D E 6.20 lC:can Range October c 3-93-9.33 2.40 0.32-3.72 2.70 1.12-1+.02 5-70 3.80-9.18 s.P.o tlange 3.26-9.58 Eean Range lf.lf3-lO. 75 6.13 6.00 2.97-10.81+ 15.40 11.02-18.78 Table 32. Arithmetic mean nnd ranc;e of sediment temperatures (C 0 ) Sta.tion A January liean Hance 9-g 7 .?>-lE. 7 c B 10.2 7 .1+-12. 7 D 12.6 10.1-21.5 February Nean Range 16.0 13.6-19.5 Narch He an Hance 11.9-20.0 April Mean Range Eay June July Auct;.st 9-5 7. 1!-ll.l 11.:s lr.l-16.0 11.4 lO .. ｾｓＭＱＮＵ＠ 10.1-12.2 Ec.:.-tn Ransc 12.0-15.5 l':enn Ranc;e 11.0 10.7-11.e 11.5 10.9-12.1 1 11.1 13.3-15.0 13.3-16.1 ll.l+ Uenn :<a nee 11.3 9.2-15.1 13.9 i1D.nce }:ean 1).7 ＱＰＮＵＭｬＧｊｾ＠ 13.8 lC1.3 1P .S-1';.9 16.1 ll-r.5-l7 .. 5 1 ｌｾＮ＠ Ａ｟ｾ＠ 13. G-1 11. 9 lS.f: 1?.9 ll.0-16.3 ""' Table 32 (continued) St;:'!t} on c r·ionth September 11: '7 J• I lie an 16.0-17.9 Iinngc October ｎｯｶ｣ｲｾ｢･＠ l<ean Tiancc t-:can 18.3 17.0-21.0 12>.9 1C..o 16.2.-2?.0 ｬｨＮｯＭＲＺｾＴ＠ 15." 1L1-.E-1P.5 ｾｲＺＭ｣･ｮ｢＠ 1-:ean n.ance D liS.'i }If. 7-18. C] 17.9 15-9-24.7 16.0 1 11.9-19.5 74 ｾＺＮ｢ｬ･＠ 33. Canonical ･ｮｶｩｲｯｦＮＧｬｴ＿ｾ＠ ｣ｯｲＡＧ･ｬｾｴｩｮ＠ analysis of seven and five taxa variables Variables Canonical variate Ｈｾｖ TemperDture Percent water 0.573 1-:eOian f;rain size 0.709 Sorting -0.599 SkeHness -0.517 Kurtosis o.o66 l<arionin::t subterrar..ea 0.712 Ｑﾷｾ＠ .. cf. ache3. ta 0.551 Earionina spp. 0.425 Lumb!'icillu.s group o.4E7 rrubificids 0.228 Canonical correlation coefficient 0.437 (p ｾＮＰＵＩ＠ Ｑ Ｉ＠ 75 consider these three variables as the only possible combination. However, the canonical correlation coefficient, though significant, is low and only general conclusions can be based on the results. DISCUSSION Interstitial oligochaetes tended to inhabit three discrete horizontal areas at the Salinas State River Beach. Marionina subterranea was found at all stations during this study with high concentrations at stations B to D. landward stations. The other enchytraeid species were confined to the Occasional individuals located at the seaward stations could be attributed to displacement by water turbulence (Gerlach, 1977). Tubificids inhabited stations B toE with high concen- trations at stations C and D. In this study Marionina subterranea was the numerically dominant oligochaete reaching the highest average density of 308 individuals I 250 cm 3 2 during July (123 indivs. I 100 cm ). oligochaetes, ｰｲ･､ｯｭｩｮ｡ｴｬｹｾﾷ＠ Narine (1977) reported that subterranea, constituted 6-7% of the total meiofauna from the Salinas State River Beach. Comparatively, Giere (1975) reported densities of 11,856 individuals I 100 cm 2 forM. sub- - terranea in an exposed beach in Scotland. ---- Other authors have also reported densities higher than those found in this study (Mcintyre and Murison, 1973; Fenchel et al., 1967; Jansson, 1962; Lasserre, 1975). Schmidt (1968) reported that oligochaetes may make up 40-60% of the total meiofaunal population. The population of Marionina subterranea appeared to have three density peaks at station C. One peak was in late winter, February, repeated again in December and a large density peak in midsummer. small density in June should be questioned since buted quite deep (median depth segment 30-35 em). ｾﾷ＠ The subterranea was distriOligochaetes have been found down to 60 em on tidal beaches (Schmidt, 1969) and 70 em on atidal 76 77 beaches (Lasserre, 1971). may have resulted in It is very possible that sampling only to 50 em ｵｮ､･ｲｳｴｩｭ｡ｧｾＭ oligochaete densities. subterranea and the other Nevertheless, the density peaks of M. subterranea are not represented by any increase of individuals due to recruitment. This is indicated by the relatively small proportional change of maturity states throughout the sampling period. Clearly the population density increase can be attributed to a general increase of individuals through vertical and/or horizontal migration representing all maturity states. Sexually mature individuals of ｾＭ subterranea containing sperm funnels reached their highest average densities in February and July but comprised a proportionally higher fraction of the population from January through July. Breeding individuals were also in the population every month, although in lower proportions from August to December. It appears that M. subterranea is capable of breeding continuously but has periods of intense breeding activity as reported for macrofaunal tubificids (Kennedy, 1966; Brinkhurst and Jamieson, 1971). of immatures tends to support this idea. The continuous presence More conclusive evidence would be based on cocoon deposition; however, cocoons were never found during this study. The small size of the cocoons and their tendency to stick to the substratum after deposition (Lasserre, 1975) probably prevented their detection in the samples. The higher proportion of adults at station C from August to December suggests recruitment of post-reproductive individuals and immatures into the adult class. Giese and Pearse (1974) and Harris (1976) have indicated that breeding periods of marine invertebrates coincided with temperature increases, but little work has been done with aquatic oligochaetes. Lasserre (1971) and Kennedy (1966) tentatively concluded oligochaete 78 breeding periods were dependent on food and temperature. However the breeding peaks for Marionina subterranea in this study do not seem dependent on temperature. The warmest temperatures in the sediment during this study and in the surf zone water appeared from July to December, while the intense breeding periods of M. subterranea occurred from January through July. Pronounced seasonal changes in vertical distribution of meiofaunal populations have been reported where populations were generally found near the surface in spring and summer but at lower depths during fall and winter (Schmidt, 1969; Harris, 1972; Narine, 1977; Renaud-Debyser, 1963 in Swedmark, 1964). This is in agreement with the results for Marionina subterranea at the seaward stations. This vertical shifting towards the surface during spring and summer has been attributed to food availability at the surface (Schmidt, 1969). The general occurrence of meiofaunal populations at greater depths in fall and winter has been interpreted as due to a greater stability of temperatures at these depths (Schmidt, 1969; Renaud-Debyser, 1963 in Swedmark, 1964). At the landward stations the vertical distribution of M. subterranea near the surface during the winter was probably related to increased wetness of the surface layers. During summer with warmer temperatures, there is less interstitial water near the surface during low tide and subsequently the worms are found deeper. However, under more extensive sampling at station C no such seasonal phenomena could be observed, suggesting that such trends need further investigating. Since the other enchytraeids were concentrated at the landward stations, sampled every third month and occurred in low densities, little of their population structure could be derived from the data. These 79 species, representing three genera, had the highest proportion of sexually mature or breeding individuals during July, corresponding with the gradual increase of seawater temperature found in this study. Following this, in October, immature densities increased and accounted for a higher proportion of the total population. It is tempting to speculate the increase in October was due to the emergence of young from cocoons laid during the breeding period, but further field studies and laboratory culturing experiments are warranted to explore this possibility. Tubificids had the highest average density of 83 individuals / 250 em 3 during October but that was quite low compared to other tubificid populations (Giere, 1975). Only one breeding period was observed for the tubificids at station C between April and August. The high density peak that would be expected in October to December due to young hatching from cocoons laid by the breeding individuals did not occur. Again the low median depth of the tubificids during these months may have prevented sampling the population adequately. The increase of sexually mature tubificids during this breeding did not coincide with ｷ｡ｲｭｾｮｧ＠ tempera- tures as found previously for the other enchytraeids. Canonical correlation was used to study the relationship of measured physical parameters to oligochaete density and distribution. The success of the method previously (Cassie and Michael, 1969; Poore and Mobley, 1980) was based on linear relationships between variables. It was hoped in this study that linear measurements could be obtained by sampling perpendicular from the water edge. However, the only linear physical factors found were mean and median grain size, with coarser sand found at station E, the closest seaward station. Only Marionina subterranea was 80 significantly correlated with grain size reflecting the general observation that the coarsest sand contained fewer M. subterranea. This pref- erence for certain grades of sand was confirmed experimentally in which M. subterranea preferred sand grains between 2.0-2.5 diameter. factor ｰ･ｲｾ＠ ｾ＠ or 117-354 microns in It is generally recognized that grain size is not a limiting for meiofaunal organisms except to provide interstitital spaces too large or too small for the organism. Thus the larger grain size could provide interstitial spaces too large for the worms. However, the oligochaetes absence may also be due to avoidance of the resorting and resuspension of sand (Hulings and Gray, 1976) which is more pronounced near the water edge (King, 1951). Another possibility is that the worms may be displaced by the increased wave activity (Gerlach, 1977). Though Mcintyre (1969) and others have stressed the importance of temperature acting directly in controlling meiofauna distribution, temperature was not significantly correlated with the distribution of any oligochaete group. Experimentally it was seen that M. subterranea pre- ferred the temperature regime 16-20°C and presumably this relationship should have been reflected in the field. However many sediment samples with temperatures below 10°C contained large numbers ｯｦｾﾷ＠ oubterranea. Jansson (1968) stressed that an aggregation of species does not necessarily indicate their optimal preference zone if environmental conditions have not been stable for a sufficient period of time. In such cases, such as beaches with tidal-induced fluctuating physical parameters, tolerance levels of specific species would be more useful interpreting animal microdistribution patterns than preference zones (Wieser, 1975; Giere, 1980). Such experimentally determined tolerances respond more to fluctu- ating ecological extremes that are encountered by individual oligochaetes 81 in their environment (Giere, 1980). Jansson (1968) found that three Marionina spec1es were distributed in certain zones on a beach in accordance to specific tolerance levels of temperature and salinity found in the beach. Populations of Phallodrilus monospermathecus from boreal and subtropical areas tolerated particular salinities and temperatures common in their respective habitats (Giere, 1977; Giere and Pfannuche, 1978). Subtropical populations were adapted to a warm environment and tolerated higher temperatures than the colder adapted boreal populations. In this study it was found that Marionina subterranea tolerated a temperature range of 5-20°C. Even at 25°C and 30°C survival lasted many hours. Similar tolerance ranges ｯｦｾﾷ＠ subterranea inhabiting the Atlantic coasts of France and eastern North America were reported by Lasserre (1971). ｰ･ｲｭｩｴｾﾷ＠ Obviously the wide temperature tolerance range exhibited would subterranea to inhabit the entire beach zone where such extreme temperatures were measured. Distribution patterns of the other oligochaetes have not been found to be due to any of the measured physical parameters. The infrequent sampling may have partially attributed to this noncorrelation. However, other physical factors (Giere, 1973; Jansson, 1968) may act by controlling faunal distribution through singular or synergistic interactions (Gray, 1968; Giere, 1977). Future work will have to rely on experi- mentally determined tolerances and preferences to discern clear relationships between meiofauna populations and their environment. In addition, biological factors such as food preferences (Brinkhurst, Chau and Kaushik, 1972; Giere, 1975; Wavre and Brinkhurst, 1971) and predation (Jansson, 1968; Jennings, 1960; Jennings and Gibson, 1969; Wisnienski, 1978) not examined in this study, have recently been 82 explored. Undoubtedly future work will also have to deal with these factors for interpreting life history patterns and microdistribution. Literature Cited Bascom, W. 1964. Waves and beaches. City, New York, 267 pp. Doubleday and Co., Inc. Garden Boaden, P. J. S. 1968. Water movement--a dominant factor in interstitial ecology. Sarsia, 34:125-136. and H. M. Platt. 1971. Daily migration patterns in an interstitial meiobenthic community. Thal. Jugoslav., 7:1-12. Boisseau, J. P. 1957. Technique pour l'etude quantitative de la faune interstitielle des sables. Comptes Rendus du Congres des Societes Savantes de Paris et des Departments, section .des sciences: 117119 0 Brinkhurst, R. 0., K. E. Chau and N. K. Kaushik. 1972. Interspecific interaction and selective feeding by tubificid oligochaetes. Limnol. Oceanogr., 17: 122-133. and B. G. M. Jamieson. 1971. Aquatic Oligochaeta of the World. Edinburg, Oliver and Boyd, 860 pp. Cassie, R. M. and A. D. Michael. 1968. Fauna and sediments of an intertidal mud flat: A multivariate analysis. J. exp. mar. Biol. Ecol., 2: 1-23. Cook, D. G. 1971. The Tubificidae (Annelida, Oligochaeta) of Cape Cod Bay. II. 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