Bryoliths (Bryozoa) in the Gulf of California1 D. W. James,2,4 M. S. Foster,2 and J. O’Sullivan3 Abstract: Populations of Diaperoforma californica (d’Orbigny) bryoliths were dis- covered in rhodolith beds, a sand habitat, and on a cobble bottom in the Gulf of California, Mexico, the first known observation of a modern free-living cyclo- stome bryozoan in the Northern Hemisphere. Densities ranged from a mean of 9.2 to 22.6 individuals/0.06 m2. Bryoliths from the deepest site were irregu- larly shaped and had the highest variation in shape; those from shallow sites were spheroidal. Water motion and bioturbation move the bryoliths and may determine their morphology. Schizomavella robertsonae (Soule, Soule & Chaney) bryoliths also occurred occasionally in one rhodolith bed sampled. Fossilized bryolith specimens of the cyclostome Diaperoforma californica (d’Orbigny) were found in a Pleistocene deposit near modern habitats. Bryoliths (free-living bryozoans that colo- channel deposits of the Imperial Formation of nize and surround a pebble, shell fragment, southeastern California (Kidwell and Gyllen- and other objects or are formed by frag- haal 1998) were found. mentation and regeneration) (Cook 1963, Attached colonies of the cyclostome bryo- Winston and Ha˚kansson 1986, Kvitek 1989), zoan Diaperoforma californica (d’Orbigny) have algae (Bosence 1983), and coral (Glynn 1974, been reported from British Columbia to Scoffin et al. 1985) are known to occur world- Costa Rica from below the low-tide level to wide on soft bottoms. Cheilostome and cte- depths over 185 m and are common in the nostome bryoliths are found on sand and Gulf of California (Osburn 1953). This spe- shell-gravel substrates. The Gulf of Califor- cies is morphologically plastic, with shapes nia contains very large populations of rho- ranging from short and palmate to tall with doliths (unattached nongeniculate coralline slender branches. Habitat may affect the mor- algae) (Foster et al. 1997), coralliths (free- phology of D. californica. The branches are living coral) (Reyes-Bonilla et al. 1997), and, usually narrow in proportion to their length as reported here, modern bryoliths in some in deeper waters and shorter, wider, and less locations. In addition, fossil cheilostome erect in exposed habitats (Osburn 1953). bryozoans from upper Pliocene deposits in We describe this species as a bryolith, the Loreto Basin (Cuffey and Johnson 1997, the first description of a modern free-living Dorsey and Kidwell 1999) and Pliocene tidal cyclostome bryozoan in the Northern Hemi- sphere, and present information on its mor- 1 This work was supported in part by National phology, density, cover, and habitat. Geographic Grant No. 5774-96 (to K. Meldahl), Inter- American Institute Grant No. UCAR 597-74025 (to materials and methods M.S.F.), and Moss Landing Marine Laboratories. Manu- script accepted 1 March 2005. 2 Moss Landing Marine Laboratories, 8272 Moss Study Sites Landing Road, Moss Landing, California 95039. Bryoliths were studied at four sites in the 3 Monterey Bay Aquarium, 866 Cannery Row, Mon- terey, California 93940. Gulf of California (Figure 1), and densities 4 Current address: The City of San Diego, Environ- were estimated at two of these, the rhodolith mental Monitoring and Technical Services Laboratory, beds off Punta Chivato (Manto de James) 2392 Kincaid Road, San Diego, California 92101. and off Isla Pata in Bahı´a de Los Angeles. Additional observations and specimens were Pacific Science (2006), vol. 60, no. 1:117–124 collected off Isla Pescador in Bahı´a de Los : 2006 by University of Hawai‘i Press Angeles and in the Canal de San Lorenzo. All rights reserved Pleistocene Diaperoforma californica (d’Or- 117 Figure 1. Location of study sites in the Gulf of California, Mexico. Bryoliths in the Gulf of California . James et al. 119 bigny) fossil specimens were collected at Isla All bryoliths, algae, and substrate under each Coronado. point were recorded. Bryolith density was Bryoliths were sampled in the rhodolith determined at Manto de James in June 1997 bed at Manto de James in March 1997 and (n ¼ 5) and Isla Pata in June 1998 (n ¼ 10). June 1997. This rhodolith bed occurred on All bryoliths were counted in 0.25 by 0.25 m a shallow (6.7–7.3 m) flat sandy bottom ex- randomly placed quadrats. posed to strong tidal and wind-driven cur- Sphericity of haphazardly collected bryo- rents. Bryoliths were mostly Diaperoforma liths was calculated to determine if mor- californica (Figure 2A,B,C,E), with Schizoma- phology varied among locations. Variation vella robertsonae (Soule, Soule & Chaney) in shape was characterized by measuring the occurring occasionally (Figure 2D). Rhodo- longest dimension (L), the intermediate di- liths consisted of Lithophyllum margaritae mension measured at the widest point 90 to (Hariot) Heydrich and Neogoniolithon trichoto- the midpoint of the axis of L (I), and the mun (Heydrich) Setchell & Mason and cov- shortest dimension measured at 90 to the ered 50–60% of the bottom. Sparse foliose midpoint of I (S). These lengths were mea- red algae were present. sured with a digital caliper (to the nearest 1/ Diaperoforma californica bryoliths were ob- 100 of a mm) and were used to calculate the served on the southwest side of Isla Pescador, coefficient of variation (CV; sample standard Bahı´a de Los Angeles, in May 1994. High deviation/mean of L, I, and S multiplied by densities of bryoliths 1.5–3 cm in diameter 100; n ¼ 3), a measure of sphericity (Foster occurred in 2–3 m of water in swell troughs et al. 1997). on the sand. The troughs were several meters The difference between individual mean long and located 20–30 m offshore. Various bryolith lengths at Manto de James in March algae, including rhodoliths, and organic de- and June was tested for significance (indepen- bris filled the troughs and covered the bryo- dent sample t-test) based on the means of all liths. three axes. The means were log(X) trans- A bryolith field consisting of D. californica formed to satisfy the assumption of normal- was sampled at Isla Pata, Bahı´a de Los Ange- ity. Normality was determined graphically, les, in June 1998. Bryoliths occurred on a and homogeneity of variances was tested us- cobble bottom in a band 8.5–11 m wide and ing the F test (Zar 1984). 53 m long that paralleled the curving shore- Differences in bryolith sphericity (CV) line at a depth of 2.4 m and 15 m from shore. among sites were tested with analysis of vari- No rhodoliths were observed. ance (ANOVA). The assumption of normally Diaperoforma californica bryoliths from the distributed error terms was tested using a Canal de San Lorenzo were collected from normality plot of residuals. Levene’s test re- a depth of 14 m in a rhodolith bed between vealed minor homoscedasticity of error terms, Isla Espı´ritu Santo and Calerita in June 1997 which was corrected using an arcsine–square (rhodolith bed described in Foster et al. root transformation. [1997]). The rhodolith bed consisted of rho- doliths (primarily Lithophyllum margaritae) results grading into white calcareous sand at 12– 19 m depth. Bryoliths were common in the habitats Bryolith and algal cover was determined at sampled. The percent cover of bryoliths Manto de James in June 1997 using a point (mean % G SE) at Manto de James in June quadrat consisting of a 1-m bar with a 1.5-m was 15 G 4%. Rhodolith cover was 64 G 6%, string attached at both ends with 10 points foliose red algal cover was 12 G 6%, and sand tied on the string (Foster 1982). Five quadrats cover was 8 G 3%. Bryolith density at Manto were randomly placed and sampling points de James in June was 9.2 G 2.33 individuals/ (total ¼ 20) were positioned on each side of 0.06 m2 (mean G SE) and 22.6 G 2.95 the bar. Bars were placed where the rhodo- individuals/0.06 m2 at Isla Pata. Although liths covered 50–60% of the sand bottom. quantitative data were not collected at Isla Figure 2. Representative bryoliths from study sites in the Gulf of California. A, Isla Pescador; B, Isla Pata; C, Manto de James; D, Manto de James; E, Canal de San Lorenzo; F, Isla Coronado (fossil). All are Diaperoforma californica ex- cept D, which is Schizomavella robertsonae. Bryoliths in the Gulf of California . James et al. 121 TABLE 1 Shape and Size of Bryoliths Site Depth (m) Longest Axis Intermediate Axis Shortest Axis CV n Isla Pata 2 43.69 G 2.29 39.35 G 2.23 33.82 G 2.37 14 G 39 Manto de James March 7 22.89 G 1.32 19.46 G 1.27 15.89 G 1.42 19 G 36 June 7 17.91 G 1.27 14.65 G 0.96 11.19 G 0.81 23 G 214 San Lorenzo 12–19 19.26 G 0.55 15.47 G 0.71 11.45 G 0.69 27 G 320 Note: Lengths, mean G SE mm (untransformed data); CV, coefficient of variation (%; mean G SE; untransformed data). Sphericity increases as CV decreases. Pescador and the Canal de San Lorenzo, bryoliths from both Isla Pescador and Isla bryoliths were abundant at Isla Pescador but Pata. rare at the Canal de San Lorenzo. Bryoliths differed in size and shape at the discussion various sites (Figure 2). Size (longest dimen- sion) ranged from 30.8 to 56.7 mm at Isla Although there are numerous species of free- Pata, 10.9 to 28.3 mm at Manto de James, living cheilostomate bryozoans, this record of and 14.1 to 22.8 mm at San Lorenzo (Table Diaperoforma californica is the first known rec- 1).