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Articles 1261 - 1290 of 2516
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Effect Of Physical Disturbance On Population Dynamics And Trophic Interactions Among Microbes And Meiofauna, Daniel M. Alongi
Effect Of Physical Disturbance On Population Dynamics And Trophic Interactions Among Microbes And Meiofauna, Daniel M. Alongi
Journal of Marine Research
A series of laboratory experiments was conducted to assess the effects of physical disturbance of surface sediments on trophic interactions among bacteria, protozoa and meiofauna. Bacteria, zooflagellates, and populations of the hypotrich ciliate Aspidisca sp. and the nematode Diplolaimella chitwoodi were, at most sampling periods, not significantly affected by small-scale, daily disturbances. However, populations of the epibenthic harpacticoid copepod Tisbe holothuriae became disproportionately abundant in disturbed cultures.Bacterial numbers, growth rates and doubling times were affected little by the presence of meiofauna. The response of zooflagellates was not clear; populations of the ciliate Aspidisca sp. were, at most sampling intervals, significantly …
Nitrogen Storage And Use Of Biochemical Indices To Assess Nitrogen Deficiency And Growth Rate In Natural Plankton Populations, Q. Dortch, J. R. Clayton Jr., S. S. Thoresen, J. S. Cleveland, S. L. Bressler, S. I. Ahmed
Nitrogen Storage And Use Of Biochemical Indices To Assess Nitrogen Deficiency And Growth Rate In Natural Plankton Populations, Q. Dortch, J. R. Clayton Jr., S. S. Thoresen, J. S. Cleveland, S. L. Bressler, S. I. Ahmed
Journal of Marine Research
Various newly developed indicators of N deficiency, physiological state (approximate growth rate), and N source for growth were measured during five cruises to Dabob Bay, Washington from early spring to summer. Although nitrate and ammonium in the surface layer were depleted early in the spring, the plankton populations never became extremely N deficient, as indicated by high intracellular amino acid/protein ratios. However, growth rates, estimated from protein/DNA or RNA/DNA ratios, were usually low unless nitrate concentrations were high or had recently been high, as indicated by large intracellular nitrate pools or high nitrate reductase activities. High growth rates were observed …
Correlation Scales, Objective Mapping And A Statistical Test Of Geostrophy Over The Continental Shelf, Kenneth L. Denman, Howard J. Freeland
Correlation Scales, Objective Mapping And A Statistical Test Of Geostrophy Over The Continental Shelf, Kenneth L. Denman, Howard J. Freeland
Journal of Marine Research
We have constructed spatial structure functions for oceanographic variables, collected during 15 cruises off the coast of Vancouver Island, Canada over a 3 year period (1979–81), to determine the appropriate correlation function and unresolved noise level for objective mapping according to the Gauss-Markov theorem. The assumption of quasigeostrophic flow has been tested by comparing the longitudinal and transverse velocity shear structure functions derived from geopotential height fields with those derived from 6 current meter moorings. In addition objective maps of geopotential height imply current shears similar to the directly observed shear vectors, as would be expected under geostrophic control. Structure …
Features Of The Circulation In The Mozambique Basin In 1981, Marten L. Gründlingh
Features Of The Circulation In The Mozambique Basin In 1981, Marten L. Gründlingh
Journal of Marine Research
Several cruises of the RV Meiring Naudé in 1981 were aimed at deriving the background or average circulation in the Mozambique Basin. This information would be of direct benefit to determine the advection of isolated eddies in this area. The results reflected the existence of a strong (up to 67 × 106 m3s−1) but variable current in the vicinity of the Mozambique Ridge. An eddy associated with this current and situated east of the Ridge emerged as a significant feature of the survey. No evidence could be found of a consistent background flow in the …
Dynamics Of Temperature And Chlorophyll Structures Above A Seamount: An Oceanic Experiment, Amatzia Genin, George W. Boehlert
Dynamics Of Temperature And Chlorophyll Structures Above A Seamount: An Oceanic Experiment, Amatzia Genin, George W. Boehlert
Journal of Marine Research
Three hydrographic surveys comprised of densely spaced XBT and CTD stations were conducted over Minami-kasuga Seamount, in the northwest Pacific (21°36′N, 143°38′E). A cold dome, similar to a Taylor column, was observed above the seamount top during the first survey. Uplifted isotherms penetrated to the lower euphotic zone and were associated with higher chlorophyll concentrations. Vertical displacement of uplifted isotherms decayed with elevation above the seamount, so that both temperature and chlorophyll anomalies were undetectable at depths less than 80 m. Relatively high chlorophyll concentrations in a layer from 80 m to 100m depth formed a distinctive deep chlorophyll maximum …
The Effects Of Oil-Contaminated Prey On The Feeding, Growth, And Related Energetics On Pink Salmon, Oncorhynchus Gorbuscha Walbaum, Fry, Jack Peter Schwartz
The Effects Of Oil-Contaminated Prey On The Feeding, Growth, And Related Energetics On Pink Salmon, Oncorhynchus Gorbuscha Walbaum, Fry, Jack Peter Schwartz
Theses (Unassigned)
Pink salmon, Oncorhynchus gorbuscha Walbaum, fry were exposed to oil-contaminated prey (OCP) in a series of experiments to determine the effects of oil exposure via the diet on the ability of pink fry to survive. Brine shrimp, Artemia salina, nauplii were contaminated with petroleum hydrocarbons by exposure to the water-soluble fraction (WSF) of Cook Inlet crude oil and fed to the fish. Feeding rates were measured for 10 days using OCP and for 5 days using uncontaminated prey (post-exposure period). In a separate experiment, fry growth was measured over a 50 day period. In another experiment, fry oxygen consumption, food …
Flux Measurements Across A Finger Interface At Low Values Of The Stability Ratio, Trevor J. Mcdougall, John R. Taylor
Flux Measurements Across A Finger Interface At Low Values Of The Stability Ratio, Trevor J. Mcdougall, John R. Taylor
Journal of Marine Research
We present the results of laboratory experiments across a sharp finger interface using heat and salt as the properties which contribute to density. Values of the stability ratio Rp as low as 1.2 were achieved so the results approach the range of Rp which is of interest in the ocean. The buoyancy flux ratio, corrected for vertical heat conduction, Rf* was found to depend on Rp, but at Rp = 1.2, Rf* is still only 0.65 ± 0.1. Values of Stern's number A = βFs(l – Rf)/ …
Effects Of Remote Annual Forcing In The Eastern Tropical Atlantic Ocean, Julian P. Mccreary Jr., Joel Picaut, Dennis W. Moore
Effects Of Remote Annual Forcing In The Eastern Tropical Atlantic Ocean, Julian P. Mccreary Jr., Joel Picaut, Dennis W. Moore
Journal of Marine Research
An ocean model is used to study the effects of remote annual forcing in the eastern tropical Atlantic. The model is linear, viscid and continuously stratified. The ocean basin is an idealized version of that of the tropical Atlantic, and the wind stress forcing the model is an idealized representation of the annual variation of the equatorial trades in the western Atlantic. Solutions are represented as expansions of the baroclinic modes of the system. The response of each mode is found numerically, not by integrating the equations of motion forward in time, but at a fixed frequency (2π year–1 …
Wind And Thermal Conditions Along The Equatorial Pacific, Jene-René Donguy, Alain Dessier, Gérard Eldin, Alain Morliere, Gary Meyers
Wind And Thermal Conditions Along The Equatorial Pacific, Jene-René Donguy, Alain Dessier, Gérard Eldin, Alain Morliere, Gary Meyers
Journal of Marine Research
Variability in heat storage of the equatorial Pacific Ocean during El Nino Southern Oscillation episodes is analyzed from subsurface temperature observations in order to show how the patterns of heat content are related to changes in the Walker Circulation. Large-scale zonal gradients in depth of the thermocline (and dynamic height) are largely in equilibrium with local zonal wind stress. Depth of the thermocline is positively correlated with mixed layer heat content and sea-surface temperature in the central Pacific during a minor El Nino/Southern Oscillation episode in 1969, indicating that the oceanic dynamic response to wind forcing as well as thermodynamic …
The Influence Of Seagrass Cover On Population Structure And Individual Growth Rate Of A Suspension-Feeding Bivalve, Mercenaria Mercenaria, C. H. Peterson, H. C. Summerson, P. B. Duncan
The Influence Of Seagrass Cover On Population Structure And Individual Growth Rate Of A Suspension-Feeding Bivalve, Mercenaria Mercenaria, C. H. Peterson, H. C. Summerson, P. B. Duncan
Journal of Marine Research
The average density of Mercenaria mercenaria in 216 ¼-m2 samples taken in spring 1980 from an eelgrass (Zostera marina) bed in Back Sound, North Carolina, was 9.0 m–2, more than five times the average density (1.6 m–2) in 216 ¼-m2 samples from a nearby sand flat. Size-frequency distributions differed between environments, with the sand flat containing a larger fraction of its Mercenaria in the smallest size class (0–1 cm). Use of internal growth lines to age all Mercenaria collected revealed that age-frequency distributions also differed between environments but that average Mercenaria age …
Habitat Dimensions Of Calanoid Copepods In The Western Gulf Of Mexico, James A. Cummings
Habitat Dimensions Of Calanoid Copepods In The Western Gulf Of Mexico, James A. Cummings
Journal of Marine Research
The vertical distributions of 49 species (53 taxa) of calanoid copepods were determined in cyclonic and anticyclonic hydrographic features in the western Gulf of Mexico for three seasons of the year. The relative intensities of the features varied among seasons, while within seasons the physical structure between features was different. Since the same copepod species were present in both features for all seasons sampled, the contrasting hydrography provided a natural experiment in which to study the mechanisms, biological or physical, acting to influence species vertical distribution patterns. Hierarchial classification analysis revealed that groups of samples characterized by relatively homogeneous biotic …
Nephelometer And Current Observations At The Stie Site, Panama Basin, W. D. Gardner, J. K. B. Bishop, P. E. Biscaye
Nephelometer And Current Observations At The Stie Site, Panama Basin, W. D. Gardner, J. K. B. Bishop, P. E. Biscaye
Journal of Marine Research
The LDGO-Thorndike film recording nephelometer was used in three modes (profiling, short-term tethered and long-term moored) to measure changes in particle concentrations on time scales of minutes to weeks and space scales of meters to 25 km while measurements were being made on production and settling rates of particles. Although the nepheloid layer had no large near-bottom increase suggestive of local resuspension, there was an unusually thick nepheloid layer due to resuspension and advection of sediment from the basin walls. The concentration of particles increased by a factor of 3 between 900 m and the seafloor at 3840 m, while …
Comments On "On The Determination Of Absolute Velocities In The Ocean" By M. E. Fiadeiro And G. Veronis, Lee-Lueng Fu
Comments On "On The Determination Of Absolute Velocities In The Ocean" By M. E. Fiadeiro And G. Veronis, Lee-Lueng Fu
Journal of Marine Research
Fiadeiro and Yeronis (1982, FY hereafter) proposed a procedure that they claimed would lead to the best reference level for computing the absolute velocities in the ocean by the inverse method as described in Wunsch (1978). According to FY, the reference level obtained by the procedure is best because the correction required of the absolute velocities at this level to satisfy a set of imposed constraints is minimum among all the possible levels. However, one likes to ask whether the velocity field resulting from this choice of reference level is necessarily the best in the sense of being closest to …
Spatial And Temporal Effects Of Salinity, Temperature And Chlorophyll On The Communities Of Zooplankton In The Southeastern Bering Sea, Sharon L. Smith, Julio Vidal
Spatial And Temporal Effects Of Salinity, Temperature And Chlorophyll On The Communities Of Zooplankton In The Southeastern Bering Sea, Sharon L. Smith, Julio Vidal
Journal of Marine Research
Analyses of 402 samples collected from late March through early June in 1980 have shown that the two communities of zooplankton over the southeastern shelf of the Bering Sea are kept separate spatially by the lack of advection and frontal characteristics of the salinity distributions. The abundance of copepods over the middle shelf, between 50 and 100 m isobaths approximately, was highly correlated with seasonal warming of the surface layer, while abundances of copepods over the outer shelf and slope were not. The spring bloom of phytoplankton influenced abundances over the middle shelf more profoundly than the outer shelf; of …
Erratum In "The Importance Of The Diffusive Permeability Of Animal Burrow Linings In Determining Marine Sediment Chemistry," By R. C. Aller; Journal Of Marine Research 41(2): 299-322., Robert C. Aller
Journal of Marine Research
On page 304 The roots, am of equation (3) are correctly defined as… The an preceding the cos function was left out by mistake in the original printed version.
Ferromanganese Micronodules From The Surficial Sediments Of Georges Bank, L. J. Poppe, R. F. Commeau, J. A. Commeau, F. T. Manheim, P. J. Aruscavage
Ferromanganese Micronodules From The Surficial Sediments Of Georges Bank, L. J. Poppe, R. F. Commeau, J. A. Commeau, F. T. Manheim, P. J. Aruscavage
Journal of Marine Research
Ferromanganese micronodules have been found on Georges Bank, off the U.S. northeast coast, distributed throughout the surficial sediments within an area about 125 km long and at least 12 km wide. These coarse, sand-sized concretions have precipitated from metal-rich interstitial waters and contain many of the textural and structural features common to other neritic nodules. Most of the nodules have accreted around detrital grains, and X-ray powder diffraction analyses indicate the presence of geothite and vernadite (δ-MnO2) in the ferromanganese layers. Chemical analyses of the micronodules, when compared with similar data on deep-sea manganese nodules, reveal …
The Importance Of Microalgae, Bacteria And Particulate Organic Matter In The Somatic Growth Of Hydrobia Totteni, Thomas S. Bianchi, Jeffrey S. Levinton
The Importance Of Microalgae, Bacteria And Particulate Organic Matter In The Somatic Growth Of Hydrobia Totteni, Thomas S. Bianchi, Jeffrey S. Levinton
Journal of Marine Research
Laboratory microcosm experiments reveal that benthic microalgae (filamentous blue-green and diatoms) probably constitute the bulk of nutrition in the somatic growth of the deposit feeding mud snail Hydrobia totteni. Despite an apparent excess of nitrogen in the particulate fraction of the sediment, H. totteni grows only about 42% as much in the dark as in the light. Growth in the dark is probably explained by the utilization of filamentous blue greens and, to a lesser extent, bacteria. The additional growth in the light is probably explained by benthic diatoms, as shown in previous studies. Standing-stocks of micro-organisms (bacteria and …
Reflection Of Low-Frequency Equatorial Waves At Arbitrary Western Boundaries, Mark A. Cane, Peter R. Gent
Reflection Of Low-Frequency Equatorial Waves At Arbitrary Western Boundaries, Mark A. Cane, Peter R. Gent
Journal of Marine Research
Procedures are developed for calculating effects of western boundaries of arbitrary geometry on low-frequency equatorial waves. We show that the mass flux incident at the coast is all returned eastward by equatorial Kelvin waves. Short Rossby waves generated as part of the reflection serve only to redistribute mass along the coast. For the case of a uniformly sloping coast we present formulae and graphical results for the amplitude of the equatorial Kelvin wave reflected at the coast due to incident free Rossby waves. Results are shown to depend on the single parameter γω where γ is the slope of the …
Abyssal Eddy Kinetic Energy In The North Atlantic, William J. Schmitz Jr.
Abyssal Eddy Kinetic Energy In The North Atlantic, William J. Schmitz Jr.
Journal of Marine Research
Both eddy and mean fields have similar zonal and meridional scales of geographical variation in the mid-latitude North Atlantic. The first map of the North Atlantic that contained estimates of the intensity of the abyssal eddy field is now several years old, and in the interim the relevant data base has increased roughly six-fold. Contemporary charts are presented, containing these more recent observations, along with some new styles of data presentation. The basic picture of maximum abyssal eddy kinetic energy near the fully developed Gulf Stream is consistently substantiated, along with a two order or magnitude latitudinal decay (from about …
Effects Of Velocity Fluctuations On Vertical Distributions Of Phytoplankton, Greg Holloway
Effects Of Velocity Fluctuations On Vertical Distributions Of Phytoplankton, Greg Holloway
Journal of Marine Research
Effects of vertical velocity oscillations (associated with high frequency internal gravity waves) upon the vertical distribution of horizontally averaged phytoplankton concentration are considered. It is suggested that such effects have been systematically misrepresented in previous modeling efforts. Correction terms are derived both for averaged quasi-Lagrangian (isopycnal) models and for averaged Eulerian models. In quasi-Lagrangian models, an apparent modification to growth rate coefficient is obtained. In Eulerian models, velocity fluctuations are shown to induce a net vertical transport which can be described by a “virtual velocity” and which is seen as a correction to eddy diffusivity parameterizations. Difficulties such as negative …
Influence Of Residents On The Development Of A Marine Soft-Bottom Community, William G. Ambrose Jr.
Influence Of Residents On The Development Of A Marine Soft-Bottom Community, William G. Ambrose Jr.
Journal of Marine Research
Field experiments in a Maine estuary were designed to follow community development in newly exposed sediment to determine if resident infauna affect the settlement and survivorship of colonizing infauna and thereby effect changes in community structure. Sets of buckets consisting of control buckets (buckets with previously dried sediment) and two experimental treatments (Nereis virens or Glycera dibranchiata added to dried sediment) were exposed on three dates between June and October 1979 and sampled after 8, 16 and/or 24 weeks. At each sampling, new buckets were established. The index of proportionate similarity comparing the infaunal community of exposure periods with …
Community Unity: Experimental Evidence For Meiofauna And Macrofauna, Susan S. Bell, Sarah A. Woodin
Community Unity: Experimental Evidence For Meiofauna And Macrofauna, Susan S. Bell, Sarah A. Woodin
Journal of Marine Research
The response of two different size classes of marine benthos, macrofauna and meiofauna, to manipulation of disturbance/predation and size specific utilization of biogenic structural refuges by each benthic size category were studied in an intertidal sandflat in Virginia. A field investigation was conducted during August and September 1980 in the same Diopatra tube system which Woodin (1978; 1981) previously utilized for macrofauna I experiments. Predator/disturber exclusion cages were employed to experimentally evaluate changes in patterns of abundance of both meiofauna and macrofauna in areas of varying Diopatra tube densities (0, 1, 3 or 6 Diopatra 0.01 m–2). Samples …
Cycling Of Nitrogen By Plankton: A Hypothetical Description Based Upon Efficiency Of Energy Conversion, Dale A. Kiefer, C. Allen Atkinson
Cycling Of Nitrogen By Plankton: A Hypothetical Description Based Upon Efficiency Of Energy Conversion, Dale A. Kiefer, C. Allen Atkinson
Journal of Marine Research
Numerous studies of the nitrogen cycle in the upper ocean have shown that the growth of oceanic phytoplankton is often largely supported by the supply of ammonium excreted by herbivorous zooplankton and members of other tropic levels. Despite considerable knowledge of the growth and metabolic responses of phytoplankton and herbivorous zooplankton to supplies of energy and nutrients, no general quantitative description of nitrogen cycling in the planktonic community has been proposed. Here we present a hypothetical description of a closed, steady state, and well mixed water column in which nitrogen is cycled between a nutrient pool, the crop of phytoplankton, …
Sediment-Water Exchange In Shallow Water Estuarine Sediments, Steven Emerson, Richard Jahnke, David Heggie
Sediment-Water Exchange In Shallow Water Estuarine Sediments, Steven Emerson, Richard Jahnke, David Heggie
Journal of Marine Research
Pore water profiles in shallow estuarine sediments of Puget Sound show the characteristics of enhanced interstitial-water transport by animal activity. Using an in situ 3H experiment and dissolved silicate profiles we evaluate the transport parameter due to animal activity in the surface 20 cm of sediments to be 1–5 × 10–7 s–1 which is in the range of similar parameters determined in other nearshore environments in the U.S. The fluxes of alkalinity, ammonia and silicate across the sediment-water interface due to biological processes are greater than that by one-dimensional molecular diffusion. For the metals Fe, Mn, Cu, …
Oxalic, Glyoxalic And Pyruvic Acids In Eastern Pacific Ocean Waters, Spencer M. Steinberg, Jeffrey L. Bada
Oxalic, Glyoxalic And Pyruvic Acids In Eastern Pacific Ocean Waters, Spencer M. Steinberg, Jeffrey L. Bada
Journal of Marine Research
A sensitive high performance liquid chromatographic (HPLC) technique has been used to determine the concentration and distribution of several α-keto acids and oxalic acid in seawater samples from a station (28°29′N, 128°38′W) in the eastern Pacific Ocean. Glyoxalic, pyruvic and oxalic acids were found to be present. Although the pyruvic acid profile at this station was in general featureless, the profiles for glyoxalic and oxalic acids showed variations which could be attributed to both primary production and heterotropic activity. Surface waters were found to have a combined concentration of glyoxalic and oxalic acids of ∼300 to 400 nm/liter which makes …
On The Equatorial Pacific Response To The 1982/1983 Ei Nino—Southern Oscillation Event, T. Y. Tang, R. H. Weisberg
On The Equatorial Pacific Response To The 1982/1983 Ei Nino—Southern Oscillation Event, T. Y. Tang, R. H. Weisberg
Journal of Marine Research
The ocean's response to the 1982/83 EI Nino—Southern Oscillation event was the largest ever documented. In this paper we explore the effects of certain details of the observed zonal wind stress anomaly field upon the ocean's response using a linear, adiabatic, reduced gravity, analytical model. The increase in magnitude of the downwelling response over the composite of previous EI Nino events is attributed to the eastward translation of the observed westerly wind anomaly and the double peaked downwelling at the South American coast is attributed to the amplitude modulation of this anomaly. Effects of an easterly anomaly which appeared to …
Observations Of An Internal Resonance In A Fjord, J. R. Keeley
Observations Of An Internal Resonance In A Fjord, J. R. Keeley
Journal of Marine Research
Current meter, CTD and tide gauge data collected in a sill fjord in northern British Columbia are considered. Annual changes in stratification are such that the natural internal period of oscillation of the fjord matches that of the semidiurnal tide in both the spring and fall of the year. Evidence of a semidiurnal internal resonance is sought by calculating the ratio of energy and the relative phase of vertical current shear and the barotropic tide. It is possible to show a strong response in the fall coincides with a phase shift of 180° which is the signature of a resonance. …
The Effect Of Summertime Shelf Break Upwelling On Nutrient Flux In Southeastern United States Continental Shelf Waters, Larry P. Atkinson, Patrick G. O'Malley, James A. Yoder, Gustav A. Paffenhöfer
The Effect Of Summertime Shelf Break Upwelling On Nutrient Flux In Southeastern United States Continental Shelf Waters, Larry P. Atkinson, Patrick G. O'Malley, James A. Yoder, Gustav A. Paffenhöfer
Journal of Marine Research
Gulf Stream-induced upwelling at the shelf break of the South Atlantic Bight (SAB) presents water which, in summer, can intrude onto the continental shelf. In July 1979, an XBT survey of the continental shelf revealed such an intrusion of cold water off St. Augustine, Florida. From weekly mappings, it was determined that Gulf Stream water <22.5°C covered 3280 km2 and occupied 38 km3 shoreward of the 42 m isobath. Using temperature and nitrate distributions and the T°C:NO3 relationship, we determined that 3200 metric tons of nitrate-nitrogen were advected into the study area. Net nitrate-nitrogen fluxes were 32 μmoles · m …
Disturbance, Sediment Stability, And Trophic Structure Of Soft-Bottom Communities, P. K. Probert
Disturbance, Sediment Stability, And Trophic Structure Of Soft-Bottom Communities, P. K. Probert
Journal of Marine Research
Previous studies of marine soft-bottom communities have shown (1) that natural disturbances (especially biologically-mediated disturbances, which are usually localized and recur reasonably frequently) help maintain spatio-temporal heterogeneity of communities, and (2) that biogenic modification of sediment can affect sediment stability with respect to fluid forces and geotechnical properties and that this is an important factor in community organization, particularly in the trophic structure of the macrofauna. It is argued in this paper that natural disturbances, and the ensuing biogenic alterations to sediment stability, may be important in maintaining trophically-mixed communities where deposit feeders do not have an overriding influence on …
Seasonal And Geographic Variation In The Shell Microstructure Of A Salt-Marsh Bivalve (Geukensia Demissa (Dillwyn)), Richard A. Lutz, George R. Clark Ii
Seasonal And Geographic Variation In The Shell Microstructure Of A Salt-Marsh Bivalve (Geukensia Demissa (Dillwyn)), Richard A. Lutz, George R. Clark Ii
Journal of Marine Research
The microstructure of the inner shell layer of Geukensia demissa (Dillwyn) varies with both the season of calcium carbonate deposition (or dissolution) and the latitude of sampled populations. Living specimens (n = 510) were sampled at monthly and, occasionally, biweekly intervals over a 3-year period from a natural intertidal population in Gulf of Maine estuarine waters. Scanning electron microscopic examination of the inner shell layer growth surface and fractured shell sections of the sampled specimens suggests that the observed structural changes reflect seasonal cycles of aragonite deposition and dissolution. Discrete nacreous tablets generally are deposited during the warmer months …