Danielle C. Zacherl

Barium and Strontium Uptake into Larval Protoconchs and Statoliths of the Marine Neogastropod Kelletia kelletii

The trace elemental composition of calcified larval hard parts may serve as useful tags of natal origin for invertebrate population studies. We examine whether the trace metal barium (Ba) deposits into the calcium carbonate matrix of molluscan larval statolith and protoconch in proportion to seawater Ba concen- tration at two temperatures (11.5 and 17°C). We also examine strontium (Sr) uptake as a function of temperature. Using encapsulated larvae of the marine gastropod, Kelletia kelletii, reared in the laboratory under controlled conditions, we demonstrate a significant inverse effect of temperature and a positive effect of seawater Ba/Ca ratio on Ba incorporation into larval carbonates. Ba/Ca partition coefficients ( DBa )i n protoconch were 1.13 at 11.4°C and 0.88 at 17.1°C, while DBa in larval statolith measured 1.58 at 11.4°C and 1.29 at 17.1°C. Strontium incorporation into statoliths is also inversely affected by temperature, but there was a significant positive effect of temperature on Sr incorporation into protoconch. These data suggest larval statoliths and protoconchs can meaningfully record variation in seawater physical and chemical properties, and, hence, have potential as natural tags of natal origin. Copyright

You Say Conchaphila, I Say Lurida: Molecular Evidence for Restricting the Olympia Oyster (Ostrea lurida Carpenter 1864) to Temperate Western North America

ABSTRACT The western North American bivalve mollusc known as the Olympia oyster, long known as Ostrea lurida Carpenter 1864†, is a historically exploited native species that has been largely displaced by larger nonnative oysters. There is much renewed interest in documenting and restoring its native populations and recent successful culturing has attracted a specialty market for these oysters. Yet its name was called into question when it was synonymized with O. conchaphila Carpenter 1857, an oyster whose type locality is Mazatlán, Sinaloa, Mexico. Others have considered it more plausible that the Olympia oyster is a more northern species, distinct from O. conchaphila, but morphological or molecular evidence either way has been lacking. Here we used a molecular approach to test the single versus two-species hypotheses with samples from Sinaloa, Mexico, near the type locality of O. conchaphila (Mazatlán, Mexico), and samples from Willapa Bay, WA, the type locality of O. lurida, as well as samples from intermediate locations. Based on our combined and separate analyses of two mitochondrial DNA (mtDNA) markers, 16S ribosomal RNA (16S) and cytochrome oxidase III (CO3), native Ostrea from Sinaloa, Mexico are reciprocally monophyletic with a clade from multiple other localities between Baja California, Mexico and British Columbia, Canada, including Willapa Bay, WA. Corrected pairwise sequence comparisons for 16S indicate these two groups last shared a common ancestor 1.5–3.9 mya (2.06% sequence divergence). Based on these results and assuming that the Sinaloa group represents the true O. conchaphila, molecular evidence supports O. conchaphila and O. lurida as separate species. Posthoc morphological comparisons uncovered no significant support for morphological distinction between the two taxa, underscoring the difficulty associated with using morphology alone to distinguish closely related oyster species. Despite the present lack of any morphological diagnostic differences for separating these nominal species, the molecular data are not consistent with the synonymy of the species and support the reinstatement of O. lurida from all the localities north of central Baja California.

Seasonal Settlement of Olympia Oyster Larvae, Ostrea lurida Carpenter 1864 and Its Relationship to Seawater Temperature in Two Southern California Estuaries

ABSTRACT The continued lack of recovery of the United States west coast populations of the Olympia oyster, Ostrea lurida † Carpenter 1864, has piqued recent interest in restoration projects. Because local population persistence is influenced by many factors, including larval settlement, information about the magnitude and timing of settlement will provide valuable contributions to such restoration efforts. We examined larval settlement as a function of season and also monitored water temperature, which is reported to influence settlement timing by cueing synchronized male spawning and subsequent larval settlement. Previous literature, based on an anomalous open coast population, found that settlement of O. lurida in La Jolla, CA occurred once seawater reached a temperature of 16°C. To observe variation over seasons in larval settlement density relative to temperature within the more common estuarine habitat in southern California, we placed ceramic tiles in two locations within Upper Newport Bay, Newport, California and in two locations within Aqua Hedionda Lagoon, Carlsbad, California. Temperature data were also collected at each site throughout the sampling period. Tiles were collected and oyster spat counted every two weeks during spring tides to pinpoint pulses in settlement. Settlement in Upper Newport Bay occurred from May until November with peak settlement in June and ranged from 0.0 oysters/m2 to 1,179 ± 344.8 oysters/m2 at Coney Island and 0.0 oysters/m2 to 511 ± 216.4 oysters/m2 at Newport Wall. In Aqua Hedionda Lagoon, settlement occurred from June until February with peak settlement in June and ranged from 0.0 oysters/m2 to 339 ± 53.7 oysters/m2 at Aqua Hedionda site 1 and 0.0 oysters/m2 to 108 ± 37.3 oysters/m2 at Aqua Hedionda site 2. Whereas oyster settlement did occur at all of our study sites, we did not observe a universal temperature that correlated with the initiation and termination of oyster settlement, nor any significant correlations linking water temperature with peaks in settlement.

EXPLORING RESTORATION METHODS FOR THE OLYMPIA OYSTER OSTREA LURIDA CARPENTER, 1864: EFFECTS OF SHELL BED THICKNESS AND SHELL DEPLOYMENT METHODS ON SHELL COVER, OYSTER RECRUITMENT, AND OYSTER DENSITY

ABSTRACT Oysters provide habitat, sediment stabilization, and improved water quality, and are important foundation species in many estuarine ecosystems. Worldwide oyster population declines have been dramatic and efforts to restore declining populations and the services they provide are ongoing. Several commonly used oyster restoration techniques were examined to determine which would be the most successful for restoring the Olympia oyster Ostrea lurida in Newport Bay, CA. Replicate (n = 5) 2×2 m shell beds were constructed of two initial shell planting thicknesses (bed thicknesses of 4 versus 12 cm) and two methods of deployment (bagged versus loose shell). Shell cover, oyster spatfall (settlement), oyster recruitment, and adult oyster densities were analyzed over 2 y; 12-cm-thick oyster beds maintained higher shell cover, experienced less sedimentation, and received greater numbers of oyster recruits than 4-cm-thick beds. There was no significant effect of shell deployment method on shell cover, recruitment, or adult density; however, spatfallwas greater on loose shell beds comparedwith bagged shell beds in the final year of the study. Overall, augmenting mudflat habitat with oyster shell significantly increased adult O. lurida oyster density compared with unmanipulated plots and increased oyster density relative to the average density of oysters measured elsewhere in Newport Bay. Collectively, the data suggest that building thicker shell beds might increase the longevity of a constructed shell bed, and therefore, this approach is recommended for future restoration activities in southern California. This study highlights the advantages of augmenting habitat in a manner that provides vertical relief from sedimentation.