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Associating with algal symbionts is considered largely beneficial for cnidarians such as corals and sea anemones, yet there are potential costs of hosting symbionts, such as the production of reactive oxygen species. We compared the photophysiology and H 2 O 2 production rates of Symbiodinium muscatinei and Elliptochloris marina , the dinoflagellate and chlorophyte symbionts, respectively, of the temperate sea anemone Anthopleura elegantissima. Analyses of photosystem II ( PSII ) function in the two symbionts, including maximum quantum yield and relative electron transport rates, were consistent with prior studies indicating that E. marina has lower photosynthetic performance than S. muscatinei at high temperature and irradiance. The efficiency of PSII in both symbionts was positively affected by the addition of exogenous catalase, suggesting that both symbionts experience H 2 O 2 -mediated declines in PSII efficiency. We found that S. muscatinei produced more H 2 O 2 than E. marina across all treatments, with the highest production under high light and temperature. Results were similar in experiments involving both isolated symbionts and symbionts residing within intact tentacles, indicating that the potential stress of symbiont isolation was not a significant factor biasing our results. Despite the lower typical densities of S. muscatinei relative to E. marina , extrapolations of cell-specific H 2 O 2 production rates to the intact symbiosis suggest that S. muscatinei imposes a greater H 2 O 2 burden on A. elegantissima. Even with this burden, however, the considerably higher productivity and fitness of S. muscatinei- bearing anemones documented in prior studies suggests that the net benefit of hosting S. muscatinei exceeds that of E. marina.

iv ACKNOWLEDGEMENTS vi TABLE OF CONTENTS vii LIST OF FIGURES viii LIST OF TABLES x INTRODUCTION 1 METHODS 4 Field sampling 4 Preparation of host and symbiont fractions 4 Lipid extraction 5 Lipid analysis 7 Statistical analyses 7 RESULTS 9 Fatty acid profiles of Symbiodinium muscatinei and Elliptochloris marina 9 Fatty acid profiles of zooxanthellate, zoochlorellate, and aposymbiotic hosts 15 Fatty acid profiles of hosts and their algal symbiont 20 DISCUSSION 24 Fatty acid profiles of Symbiodinium muscatinei and Elliptochloris marina 24 Fatty acid profiles of zooxanthellate, zoochlorellate, and aposymbiotic hosts 26 Fatty acid profiles of hosts and their algal symbiont 29 Conclusions and future research directions 30 REFERENCES 32

We evaluated the seasonal stability of two algal symbiont populations in the temperate intertidal sea anemone Anthopleura elegantissima on San Juan Island, Washington, where the relatively thermally tolerant dinoflagellate Symbiodinium muscatinei coexists with the less thermally tolerant chlorophyte Elliptochloris marina. Random collection of anemones along repeatedly sampled transects over four seasons and three shore heights revealed S. muscatinei to be the dominant symbiont, with E. marina mostly limited to anemones in the lower intertidal zone. At the lowest shore height sampled (+0.2 m), the proportion of E. marina was between 40% and 50% of the total symbiont population throughout the year. Symbiont distribution patterns persisted despite considerable seasonal variation in aerial exposure, temperature, irradiance, nutrients, and phytoplankton concentration, as well as a high potential for symbiont shuffling, with mixed-symbiont assemblages occurring in 51% of all anemones sampled. Symbiont density in anemones also changed little despite three- to fourfold-higher division frequencies of both symbionts during July and November. Although the intertidal zonation of these symbionts was stable over an annual period, we predict that their spatial distributions will be responsive to longer-term environmental change, and anticipate that this anemone symbiosis will be a useful and highly tractable barometer for future climate change, with this study serving as a baseline. A diverse array of shallow-water cnidarians, including sea anemones, corals, jellyfish, and hydroids, engage in endosymbioses with phototrophic dinoflagellates (Symbiodinium spp.) that translocate photosynthetic products to their host. Many of these symbioses exhibit plasticity with respect to both the population density and genetic identity of the dinoflagellate partner, allowing them to exploit a wide range of conditions that vary spatially and temporally. In tropical systems, where cnidarian symbioses are particularly well studied, many hosts show depth-related differences in symbiont density and physiology, and also undergo predictable seasonal fluctuations in symbiont density and physiology that are correlated with environmental conditions (Fitt et al. 2000; Warner et al. 2002). In

Because planktonic invertebrate larvae may be food-limited, anything that increases feeding and digestive efficiency should increase the chances of larval survival to metamorphosis. As light directly enhances both feeding and digestion in some planktonic heterotrophic protists, we hypothesize that similar processes might occur in the larvae of marine invertebrates. We studied the direct effects of light on feeding and development in sea urchin larvae (Strongylocentrotus droe- bachiensis, S. franciscanus and sand dollar Dendraster excentricus). Larvae were placed in 12:12 h light:dark cycles or in complete darkness and ingestion rates were measured. We monitored larval morphology during the first 2 to 3 wk of development and tested for light-related differences. Short- term changes in light regime had no effect on feeding rates. However, larvae of all 3 species showed longer-term diel feeding patterns with ingestion rates generally higher during daylight hours. These patterns persisted in S. franciscanus larvae even when larvae were held in complete darkness for 3 d. Larvae of D. excentricus exposed to natural light cycles developed longer arms usually associated with food limitation; those held in darkness had significantly shorter arms. The developing juvenile structures (i.e., rudiments) of S. droebachiensis larvae exposed to light were significantly smaller than those of larvae held in continuous darkness, suggesting that light may have negative effects on larval growth and development. Measuring the effects of light on feeding and growth may clarify the behaviors of invertebrate larvae during their critically important planktonic period.

Enormous variation exists in the reproductive output of marine invertebrates (e.g., in the numbers of embryos produced, the volumes of embryos, and the energy that they contain). It is not clear why there is such great variability or what the population-level consequences are. We sampled a population of the brooding seastar Leptasterias aequalis (Stimpson, 1862) to collect basic information on brood sizes, embryo volume, and embryo energy content with a goal to better understand the reproductive ecology of this species. We collected brooding females in February and again in April. We measured the size of their broods and sampled the broods to estimate volume and energy content of the embryos. There was great variability in the volume and energy content of embryos produced by individual females and among the embryos in a single female's brood. Larger adults produced larger embryos, which generally had greater energy content and may be of a higher quality. The average energy content of embryos appeared to increase during the brooding period. Larger females produced larger broods but lost a greater proportion of the embryos. The net result is that larger individuals may not produce any more juveniles than smaller individuals, but those that they do produce may be of a higher quality.

The Minorities in Marine Science Undergraduate Program (MIMSUP) is an academic program at Western Washington University's Shannon Point Marine Center (SPMC) that seeks to increase the representation of minority individuals in the marine sciences. For the past 13 years, groups of students have spent two 10-week quarters at SPMC studying marine science, doing independent research, and developing the skills needed for success as marine scientists/educators. Program elements include formal coursework in marine science, supervised independent research, training in up-to-date field and laboratory investigative techniques, experience developing scientific and personal job-related skills, and introduction to the career options open to marine scientists. Results indicate that the program is impacting the career paths of student participants; program alumni seek advanced education and pursue careers in the marine and environmental sciences. MIMSUP introduces underrepresented students to the marine sciences, helps t...

Barnacle encrustation negatively influenced every aspect of swimming in the scallop Chlamys hastata measured in this study. Scallops swam significantly longer, travelled further and attained greater elevation once epibiotic barnacles had been removed. Shell morphometry of barnacle-encrusted scallops was similar to shells of unencrusted scallops. Specifically, shell length was positively allometric with shell height and shell mass was negatively allometric. However, adductor muscle mass scaled isometrically to shell height, in contrast to unencrusted scallops. In the laboratory, the drag coefficient (Cd) of barnacle-encrusted scallops decreased after barnacle removal, in contrast to sponge-encrusted scallops in which no decrease in Cd was detected when the sponge was removed from the scallop's valves. Furthermore, scallops swimming with barnacle encrustation required more energy than did unencrusted scallops. Although there was no significant difference in aerobic energy expenditure between swimming barnacle-encrusted and unencrusted scallops, differences in anaerobic energy expenditure were detected. Specifically, barnacle-encrusted scallops required more arginine phosphate than unencrusted scallops to swim to exhaustion although octopine levels were similar. Thus, barnacle encrustation dramatically decreased a scallop's ability to swim, partly by increasing the drag coefficient experienced by the scallop and the energy required for swimming.

The solitary ascidian Corella injutu is a com- mon fouling organism in many areas of Puget Sound and the San Juan Archipelago, Washington, USA. Despite its abun- dance, it is conspicuously absent from areas that receive direct sunlight. Previous work suggests that ascidians in unshaded habitats can be overgrown and killed by algal overgrowth. In this study, we tested the hypothesis that UV irradiation contributes to C. inflatu distribution by killing individuals exposed to direct sunlight. To test this, we exposed C. infuta embryos, larvae, juveniles, and adults to UV irradiation and measured the responses. We also tested for UV-absorbing compounds in larvae, juveniles, and adults. In the laboratory, UV significantly damaged all life stages; the earliest stages were most vulnerable. A 3-week UV exposure significantly shortened adult life span. Juve- niles suffered 100% mortality after only 3 days. Tadpole larvae decreased settlement and metamorphosis after I day of UV exposure, and embryos exhibited developmental abnormalities after only 30 minutes of exposure. None of the life-history stages had apparent UV-absorbing com- pounds. Given the vulnerability of this species to UV, we suggest that its unique life-history traits (i.e., time of spawn- ing, brooding behavior, length of larval life) help it persist in its preferred habitat and avoid dispersal into inappropri- ate, UV-exposed areas.

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 effects 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 field, both scallop size and sponge mass were significantly greater in high turbidity sites. In the laboratory, sponges on empty scallop valves experienced near complete mortality after five 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.

The effect of sponge encrustation on swimming ability of Chlamys hastata was determined by investigating swimming behaviour, scallop morphometry, and energy expended during swimming with and without commensal epibionts. Scallops swam significantly longer after sponge encrustation was removed from their shells, but no significant differences were detected in swimming elevation or distance. Scallops with sponge encrustation showed no adductor muscle hypertrophy or changes in shell morphometry compared to scallops without encrustation. However, C. hastata did exhibit scaling relationships associated with maximizing swimming efficiency. Specifically, shell width and adductor muscle mass were positively allometric with shell height, while shell mass was negatively allometric with shell height. Scallops increased their energy expenditure (both aerobic and anaerobic) during valve-clapping, but no significant difference was detected between unencrusted (43·0 μmol adenosine triphosphate [ATP] consumed during a two min escape swim) and sponge-encrusted (40·0 μmol ATP) scallops. Scallops in both treatments derived 86% of the energy used for swimming from anaerobic sources. The lack of substantial differences between scallops with and without commensal sponges is partially explained by the observation that even heavy sponge encrustation increases the immersed weight of the scallop by only 5%. The presence of a sponge encrustation does not appear to inhibit swimming by this scallop species.

The ascidian Corella inflata (Chordata, Ascidiacea) is common in many areas of Puget Sound, Washington, USA. However, it occurs only in habitats where it is protected from direct sunlight. Previous experiments with artificial lights showed that UV irradiation kills all life stages of this animal. The effects of natural sunlight exposure (measuring survival of adults, juveniles, larvae, and embryos) were compared. We partitioned the light spectrum to separate the effects of UVB, UVA, and visible light (PAR). Natural sunlight severely damaged C. inflata. Adults and juveniles died after 2-5 d. Exposed embryos failed to develop normally and larvae did not settle. As expected, UVB had significant effects, but pronounced effects were also seen when the animals were exposed to longer wavelengths alone (UVA and PAR). Thus, the distribution of C. inflata may be determined largely by exposure to light. Understanding the basic ecology of this species requires consideration of its vulnerability to sunlight damage and the effects of UVB, UVA, and PAR.

The processes by which cnidarians and their algal endosymbionts achieve balanced growth and biomass could include coordination of host and symbiont cell cycles. We evaluated this theory with natural populations of sea anemones hosting symbiotic dinoflagellates, focusing on the temperate sea anemone Anthopleura elegantissima symbi- otic with Symbiodinium muscatinei in Washington State, USA, and the tropical anemone Stichodactyla helianthus associating with unknown Symbiodinium spp. in Belize. By extruding symbiont-containing gastrodermal cells from the relatively large tentacles of these species and using nuclear staining and flow cytometry, we selectively analyzed cell cycle distributions of the symbionts and the host gastroder- mal cells that house them. We found no indications of diel synchrony in host and symbiont G2/M phases, and we observed evidence of diel periodicity only in Symbiodinium spp. associated with S. helianthus but not in the anemone itself. Seasonally, S. muscatinei showed considerable G2/M phase variability among samples collected quarterly over an annual period, while the G2/M phase of its host varied much less. Within samples taken at different times of the year, correlations between host and symbiont G2/M phases ranged from very weakly to very strongly positive, with significant correlations in only half of the samples (two of four A. elegantissima samples and one of two S. helianthus samples). Overall, the G2/M phase relationships across spe- cies and sampling periods were positive. Thus, while we found no evidence of close cell cycle coupling, our results suggest a loose, positive relationship between cell cycle processes of the symbiotic partners.

SUMMARY The susceptibility of algal–cnidarian holobionts to environmental stress is dependent on attributes of both host and symbiont, but the role of the host is often unclear. We examined the influence of the host on symbiont light stress, comparing the photophysiology of the chlorophyte symbiont Elliptochloris marina in two species of sea anemones in the genus Anthopleura. After 3 months of acclimation in outdoor tanks, polyp photoprotective contraction behavior was similar between the two host species, but photochemical efficiency was 1.5 times higher in A. xanthogrammica than in A. elegantissima. Maximum relative electron transport rates, derived from rapid light curves, were 1.5 times higher in A. xanthogrammica than in A. elegantissima when symbionts were inside intact tissues, but were not significantly different between host species upon removal of outer (epidermis and mesoglea) tissue layers from symbiont-containing gastrodermal cells. Tissues of A. xanthogrammica were 1.8 times thicker than those of A. elegantissima, with outer tissue layers attenuating 1.6 times more light. We found no significant differences in light absorption properties per unit volume of tissue, confirming the direct effect of tissue thickness on light attenuation. The thicker tissues of A. xanthogrammica thus provide a favorable environment for E. marina – a relatively stress-susceptible symbiont – and may explain its higher prevalence and expanded range in A. xanthogrammica along the Pacific coast of North America. Our findings also support a photoprotective role for thicker host tissues in reef corals that has long been thought to influence variability in bleaching susceptibility among coral taxa.

Marine invertebrates growing epifaunally on red mangrove (Rhizophora mangle) prop roots in the Indian River, Florida, USA, were studied in a small mangrove island (Jim Island) through which a number of channels had been cut. Roots hanging down into the water supported diverse epifaunal communities including sponges, oysters, barnacles, bryozoans, and acidians. To determine what factors control species' population dynamics and contribute to the high degree of spatial heterogeneity characteristic of communities in the unique habitat, two hypotheses were tested: (1) Distributions of species on the roots are controlled by differential growth and mortality due to physical features; and (2) Recruitment, as influenced by larval supply, structures the community. Four channels of the island were chosen for comparison and experimentation. Distributions of abundances of epifauna in the channels were determined and physical parameters (i.e., temperature, pH, salinity, flow, turbidity) were measured over a 13—mo perio...

Along the North American Pacific coast, the common intertidal sea anemone Anthopleura elegantissima engages in facultative, flexible symbioses with Symbiodinium muscatinei (a dinoflagellate) and Elliptochloris marina (a chlorophyte). Determining how symbiotic state affects host fitness is essential to understanding the ecological significance of engaging in such flexible relationships with diverse symbionts. Fitness consequences of hosting S. muscatinei , E. marina or negligible numbers of either symbiont (aposymbiosis) were investigated by measuring growth, cloning by fission and gonad development after 8.5–11 months of sustained exposure to high, moderate or low irradiance under seasonal environmental conditions. Both symbiotic state and irradiance affected host fitness, leading to divergent life-history strategies. Moderate and high irradiances led to a greater level of gonad development in individuals hosting E. marina , while high irradiance and high summer temperature promoted cloning in individuals hosting S. muscatinei and reduced fitness of aposymbiotic anemones. Associating with S. muscatinei may contribute to the success of A. elegantissima as a spatial competitor on the high shore: (i) by offsetting the costs of living under high temperature and irradiance conditions, and (ii) by promoting a high fission rate and clonal expansion. Our results suggest that basic life-history characteristics of a clonal cnidarian can be affected by the identity of the endosymbionts it hosts.

I would describe my graduate career in ecol ogy as "serendipitous". As a daughter of Latino parents who grew up in challenging environments with limited access to education, I was lucky to graduate from college, let alone pursue a PhD. I was also fortunate to meet a men tor who introduced me to ecology and graduate school. Unfortunately, many students from underrepresented groups lack adequate opportunities and mentorship as they head through the "pipeline" to graduate school. Despite the need for unique perspectives in collaborative scientific research, ethnic minority students continue to "leak" from the system. According to demographic projec tions, over 50% of the US population will be composed of individuals from underrepresented groups by the year 2050 (US Department of Commerce 1996). At present, how ever, these groups constitute only 6.5% of students enrolled in higher degree programs in ecology (NSF 2007). What can we do to remedy this? Exposure, oppor tunity, and access appear to be key. Here, I present some points for consideration for academic professionals (including educators, administrators, and program man agers), based on the first-hand experiences of successful minority scientists I have interviewed or who have pub lished on the subject. Introduce ecology early and supply access to research and career opportunities. It is important to publicize research, internship, and graduate program opportunities and pro vide financial support. The Ecological Society of America's (ESAs) Strategies for Ecology Education, Development, and Sustainability (SEEDS) program has effectively intro duced minority scientists to ecology by providing fellow ships and field trips, as well as travel awards to ESA's annual meetings (www.esa.org/seeds/). Create "bridge" programs that facilitate the transition of minority students from one level of academia to the next. Summer courses, orientation programs, intemships, research experiences, and cultural events all teach stu dents about the academic and social expectations of uni versities. For example, the Meyerhoff Scholars Program at the University of Maryland (UMD) has offered scholar ships, summer bridge programs, and intemships, as well as engaged students' families, and provided faculty and peer mentoring in an effort to recruit and retain minorities in science. As a result, minority participation in the sciences at UMD has increased 18%; in addition, UMD has recently introduced a graduate fellows program (Summers and Hrabowski 2006; WebTables 1 and 2). Build a sense of community through the creation of outreach

Many temperate ascidians reproduce seasonally but the factors controlling their gametogenic cycles have not been experimentally demonstrated. I tested the effects of daylength on gametogenesis in three ascidians (Boltenia villosa, Styela gibbsii, and Chelyosoma productum) by exposing animals to normal or reversed light cycles and measuring gonad and oocyte sizes. Under a normal cycle, all species followed patterns reported for field populations. B. villosa showed evidence of continuous reproduction; S. gibbsii and C. productum spawned primarily in the spring (though a secondary mid-winter spawn may also have occurred in S. gibbsii). Altering the light cycle demonstrated that the gametogenic cues differ in these three species. Gametogenesis in B. villosa and S. gibbsii was largely unaffected by a reversed light treatment but the cycle of C. productum was dramatically changed. Even in C. productum, however, the gametogenic cycle was not completely reset in the 12-month experiment. This suggests that other factors (e.g., temperature, endogenous rhythms) contribute to gametogenic control. Longer-term experiments are needed to establish the relative importance of light cycle in these species. Additional key words: tunicates, reproduction, seasonality, synchrony, daylength Synchronous spawning is critical for marine invertebrates that release gametes into the water column and rely on currents for fertilization. Water temperature, light, phytoplankton abundance, lunar cycle, and presence of conspecifics all may cue populations to synchronize spawning and maximize fertilization (reviewed by Giese & Kanatani 1987; see also Starr et al. 1990, 1991; Tyler et al. 1992). For such cues to be effective, however, some earlier signal must entrain gametogenic cycles so that gonads contain viable sperms and full-grown oocytes or ova when the spawning cue arrives. Laboratory experiments have shown that gonad growth and maturation cycles in some marine invertebrates are affected by temperature or food abundance (reviewed by Giese & Pearse 1974; see also Babcock et al. 1986; Franz 1986; Tyler 1988; Tyler & Young 1992; Tyler et al. 1992; Beauchamp 1993). Some of the clearest evidence for extrinsic control of gametogenesis, however, comes from experimental studies with light. For example, gametogenic cycles of polychaetes (Olive & Pillai 1983; Fong & Pearse 1992a,b), a cephalopod (Richard 1967), seastars (Pearse & Eernisse 1982; Pearse & Beauchamp 1986; Pearse & Walker 1986; Pearse et al. 1986a; Xu & Barker 1990), sea urchins (Pearse et al. 1986b; McClintock & Watts 1990), and a cephalochordate (Fang et al. 1989) have been altered or completely reset by simple modifications of the light cycle. Giese & Kanatani (1987) suggest that daylength may be a fairly general gametogenic cue, but to date, only a few species in a few phyla have been studied. In this paper, I report on the first test for such effects in ascidians (phylum Chordata, subphylum Urochordata). Millar (1952, 1958) and Berrill (1975) suggested that temperature controls gametogenesis in ascidians. At temperate latitudes where annual temperature fluctuations are large and predictable, gametogenic cycles could cue to temperature changes. In tropical waters where temperatures remain quite constant, absence of the temperature cue could lead to non-seasonal reproduction. Consistent with this hypothesis, temperate ascidian species often show highly seasonal reproduction (reviewed by Millar 1971; Berrill 1975) while continuous reproduction has been demonstrated for some tropical species (Goodbody 1961, 1963). However, temperature control of ascidian gametogenesis has never been tested experimentally, and Svane & Young (1989) suggest that daylength should also be considered. The hypothesis that light controls reproductive seasonality can accommodate continuously reproducing tropical species since annual changes in daylength This content downloaded from 207.46.13.129 on Sun, 26 Jun 2016 07:01:17 UTC All use subject to http://about.jstor.org/terms