Western Washington University Masthead Logo Western CEDAR Environmental Sciences Faculty and Staff Environmental Sciences Publications 12-2002 Epibiotic Sponges on the Scallops Chlamys Hastata and Chlamys Rubida: Increased Survival in a High- Sediment Environment Duncan O. Burns Western Washington University Brian L. Bingham Western Washington University, [email protected] Follow this and additional works at: https://cedar.wwu.edu/esci_facpubs Part of the Environmental Sciences Commons Recommended Citation Burns, Duncan O. and Bingham, Brian L., "Epibiotic Sponges on the Scallops Chlamys Hastata and Chlamys Rubida: Increased Survival in a High-Sediment Environment" (2002). Environmental Sciences Faculty and Staff Publications. 1. https://cedar.wwu.edu/esci_facpubs/1 This Article is brought to you for free and open access by the Environmental Sciences at Western CEDAR. It has been accepted for inclusion in Environmental Sciences Faculty and Staff ubP lications by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. J. Mar. Biol. Ass. U.K. (2002), 82,961^966 Printed in the United Kingdom Epibiotic sponges on the scallops Chlamys hastata and Chlamys rubida: increased survival in a high-sediment environment P O Duncan O. Burns* and Brian L. Bingham O *Department of Biology,Western Washington University, Bellingham, WA 98225, USA. Department of Environmental Sciences, P Western Washington University, Bellingham, WA 98225, USA. Corresponding author, 1125 13th Street, Bellingham, WA 98229 e-mail: [email protected] The small free-swimming scallops, Chlamys hastata and Chlamys rubida, are frequently encrusted by the sponges Mycale adhaerens and Myxilla incrustans. It is unclear why this association exists. We hypothesized that living on scallop valves increases sponge survival by reducing the e¡ects of sediment accumulation. Scallops were collected to measure correlations between sediment load and encrusting sponge mass. In the laboratory, the survival of sponges on living scallops and empty scallop valves was measured. Time-lapse video was used to quantify spontaneous swimming and clapping of C. hastata. In the ¢eld, both scallop size and sponge mass were signi¢cantly greater in high turbidity sites. In the laboratory, sponges on empty scallop valves experienced near complete mortality after ¢ve weeks. Manually clearing sediments increased survival but did not duplicate the high survival of sponges on living scallops, which regularly swam or clapped their valves. INTRODUCTION not clear that any species of seastar in the Puget Sound eats scallops as a signi¢cant part of its natural diet. Mauzey et al. Epibiotic invertebrates encrust the valves of scallops (1968), in an extensive survey of seastars in the Puget around the world (e.g. Forester, 1979; Cherno¡, 1987; Sound region, found only four of 18 species feeding on Ward & Thorpe, 1991; Berkman, 1994).The selective forces scallops in the ¢eld (scallops were seen in only six of nearly driving these epifaunal associations are either unique to 3000 feeding observations). Two of six predation observa- each association, or common threads have simply not yet tions were the seastar Pteraster tesselatus, which actually been described. feeds preferentially on M. adhaerens and Myxilla encrustans The associations of the sponges Mycale adhaerens (Lambe) from the valves of scallops as well as on the scallops and Myxilla incrustans (Esper) with the scallops Chlamys themselves (Rohenhous & Guberlet, 1946). Clearly, hastata (Sowerby) and Chlamys rubida (Hinds) are a domi- epibiotic sponges could actually be a liability for scallops nant feature of the benthic biota on hard substrates in the encountering this seastar. Puget Sound and San Juan Archipelago,Washington, USA. It is possible that the greater bene¢t from the sponge/ Currently, the most popular theory explaining these strong scallop association accrues not to the scallop but to the associations is that both scallops and sponges are better able sponge. Bloom (1975) observed in the laboratory that to escape predators when they are living symbiotically. dorid nudibranchs were better able to feed on epibiotic In the laboratory, Bloom (1975) found that the pre- sponges when their scallop hosts were prevented from datory seastars Orthasterias koehleri and Evasterias troschelii swimming. He suggested that swimming by the scallops had a harder time gripping, manipulating and capturing provides an escape for the sessile sponge, thus serving as a scallops that were covered by epibiotic sponge. He asserted secondary selective force favouring the association. that sponge-covered scallops could, therefore, more easily While such predator escape may bene¢t the sponge, we escape predation. Stimulated by these ¢ndings, researchers hypothesized that a more likely bene¢t is an escape from have applied the seastar predation model to other sponge/ heavy sediment deposition. Sponges are sensitive to high scallop associations and obtained similar results (Forester, levels of suspended particles; many sponges are excluded 1979; Cherno¡ 1987). Although these data seem to support from areas with heavy sediment loads (Bakus, 1967) since seastar predation and the tube-foot interference mechanism their canals and chambers can be easily clogged by sediment as a reasonable explanation for the association, it is not (Gerrodette & Flechsig, 1979). Cherno¡ (1987) found that clear that it alone explains the evolution and maintenance epibiotic sponges experienced greater siltation and abra- of the relationship. sion when the host scallop was attached to the seabed. The predation model assumes that sponge covering Because of their £at morphology, Mycale adhaerens and e¡ectively deters seastar predators. However, the sponges Myxilla incrustans may be particularly vulnerable to sedi- covering C. hastata do not deter more aggressive species. ments. In the Puget Sound, strong river input, heavy preci- Bloom (1975) found that Pycnopodia helianthoides, a common pitation, regular algal blooms and strong tidal mixing all voracious predator, captured sponge-encrusted and unen- contribute to heavy particulate loads. We postulate that crusted scallops with equal frequency. Furthermore, it is periodic swimming of the scallop increases the tolerance Journal of the Marine Biological Association of the United Kingdom (2002) 962 D.O. Burns and B.L. Bingham Sponges and scallops in high-sediment habitats of the sponges for high sediment environments by Two-way analysis of variance (ANOVA) was used, with preventing sediments from accumulating on their surfaces. site and depth as the main e¡ects, to determine whether scallop size and sponge cover di¡ered among locations. The sponge cover data were log transformed to homo- MATERIALS AND METHODS genize variances. We used orthogonal contrasts to test for Field collections di¡erences between exposed and inland sites (Eagle Point and Pile Point vs Cone Island and Cypress Reef ) and Scallops were collected from subtidal sites in the San between sites within each of these groups (Eagle Point vs Juan Archipelago, Washington, USA. Two sites (Pile Point Pile Point; Cone Island vs Cypress Reef ). and Eagle Point) were located on the exposed west side of Wehypothesized that scallop size and sponge mass could San Juan Island. Two protected sites (Cone Islands and be related to sedimentation.Toestimate sediment loads, we Cypress Reef, Figure 1) were also sampled. The west side deployed sediment collectors at all four locations. The of SanJuan Island is in£uenced by clear waters of the open collectors were PVC tubes (5.0 cm inside diameterÂ39 cm North Paci¢c Ocean and is known by SCUBA divers as an tall) capped on the bottom end. They were attached to area of unusually good visibility. In contrast, the inshore lines weighted by cement blocks and held upright by £oats. sites of Rosario Strait and Bellingham Channel are heavily Three collectors were placed at 18 m and 24 m at each loca- in£uenced by in£ow of several large rivers, which contri- tion. They were left in place for seven days (26 November^ butes to nutrient loads, algal blooms and high turbidity. 3 December, 2001). At each study site, SCUBA divers collected 25 Chlamys In the laboratory, we allowed the collected sediments to hastata from depths of 18 and 24 metres. The scallops were settle then transferred them to pre-weighed aluminium taken to the Shannon Point Marine Center where they were pans. The samples were dried at 608C for 96 h then identi¢ed to species. We measured height of each scallop reweighed to determine dry sediment weight. We used 2- (dorsal hinge to the furthest point on the ventral margin) way ANOVA to test for di¡erences in sedimentation as a and determined the species of encrusting sponges. We used function of site and depth. Data were log-transformed to a contingency table to test for site-related di¡erences in homogenize variances. distributions of the two epibiotic sponges. The factors were sponge species (Mycale adhaerens or Myxilla incrustans)and site (Eagle Point, Pile Point, Cone Island or Cypress Reef ). Scallop behaviour Each scallop/sponge association was assigned to one cell in In the laboratory, we observed C. hastata spontaneously the table since only one sponge species was present on any clapping its valves or swimming around the tank. Todeter- scallop. mine how frequently these behaviours occur, we placed six Toquantify sponge cover, we calculated the surface area sponge-encrusted C. hastata in a 50Â26Â30