Physioecology of zooplankton. II. Effects of phytoplankton concentration,temperature, and body size on the development and molting rates of Calanus pacificus and Pseudocalanus sp.

Developmental time and stage duration for Calanus pacificus Brodsky and Pseudocalanus sp. and the rate of loss of body carbon by molting for C. pacificus were estimated for copepodite stages cultured under various combinations of phytoplankton concentration and temperature. Mean development time and stage duration for C. pacificus decreased hyperbolically with increasing food concentration, and the minimum time required for reaching a given stage decreased logarithmically with a logarithmic increase in temperature. Low temperature retarded the development of early stages proportionally more than that of late stages, and stage duration increased logarithmically with increasing body weight. Therefore, copepodite development was not isochronal. The rate of loss of body carbon by molting was small, ranging from 0.2 to 2% day^-1. This rate increased hyperbolically with food concentration and was linearly related to the growth rate. The critical food concentration for the rates of development and molting increased with temperature and stage of development, but these rates were less dependent on food concentration than the growth rate. The development rate of Pseudocalanus sp. was higher than that of C. pacificus, and was less influenced by changes in food concentration and temperature. It is postulated that the inverse relationship between temperature and body size results from a differential effect of temperature and body size on the rates of growth and development. That is, with increasing body size the growth rate tends to become temperature-independent, but the development rate remains proportional to temperature. Thus, copepodites growing at low temperature can experience a greater weight increment between molting periods than individuals growing at high temperature, because the growth rate is similar at all temperatures but stage duration is longer at low temperature.Contribution No. 1128 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Physioecology of zooplankton. III. Effects of phytoplankton concentration,temperature, and body size on the metabolic rate ofCalanus pacificus

Weight-specific rates of oxygen consumption of actively feeding copepodite stages ofCalanus pacificus Brodsky were measured under various combination of phytoplankton concentration and temperature. The rate decreased logarithmically with a logarithmic increase in dry body weight of copepods, and the relationship between these variables was described using a log-transformed allometric equation. The body-size dependence of the metabolic rate was independent of changes in food concentration and temperature, but the metabolic level increased linearly with a logarithmic increase in temperature and was not significantly affected by changes in food concentration. Respiration rates measured in this study forC. pacificus were about twice as high as rates reported for unfed closely related species of the same genus. An analysis of the metabolic cost of feeding processes suggests that metabolic models derived from feeding models may be of little ecological value at present.Contribution No. 1129 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Physioecology of zooplankton. IV. Effects of phytoplankton concentration,temperature, and body size on the net production efficiency ofCalanus pacificus

Weight-specific rates of individual production, total metabolic expenditure and assimilation, and net production efficiencies were estimated forCalanus pacificus Brodsky of selected body weights cultured at various phytoplankton concentrations and temperatures. The weight-specific rate of individual production increased hyperbolically with food concentration, and the maximum rate of individual production decreased logarithmically with a linear increase in body weight propotionally more at high than at low temperature. The weight-specific rate of total metabolic expenditure decreased logarithmically with increasing body weight and was unaffected by changes in food concentration. The effects of food concentration and temperature on the weight-specific rate of assimilation were similar to those on the rate of individual production, but the effect of body size differed considerably. The diversity in the temperature and body-size dependence of the maximum weight-specific rates of various physiological processes suggest (1) that, except for the metabolic rate, the allometric model (log-log relation) is inadequate for describing relationships between maximum rates of physiological processes and body size within species, and (2) that the common assumption that temperature affects the rates of various physiological processes in similar ways is not justified. Net production efficiency increased hyperbolically with food concentration, and the maximum production efficiency first increased slightly and then decreased gradually with increasing body weight. Small copepods attained higher efficiency at high temperature but larger ones did so at low temperature. The critical food concentrations for production efficiency and for the rate of individual production increased with increasing temperature and body size. Because of the effects of interactions among critical food concentration, temperature, and body size on the rates of growth and individual production and on net production efficiency, early development stages ofC. pacificus optimized growth and food conversion efficiency at high temperature, but late stages, particularly at low food concentrations, grew best and transformed food more efficiently at low temperature.Contribution No. 1130 From the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Effects of water temperature and mixed layer depth on zooplankton body size

Ecological consequences of global warming include shifts of species ranges toward higher altitudes and latitudes as well as temporal shifts in phenology and life-cycle events. Evidence is accumulating that increasing temperature is also linked to reduced body size of ectotherms. While temperature can act directly on body size, it may also act indirectly by affecting the timing of life-cycle events and the resulting population age and size structure, especially in seasonal environments. Population structure may, in turn, be influenced by temperature-driven changes in resource availability. In a field mesocosm experiment, we investigated how water temperature and mixed surface layer depth (a temperature-dependent determinant of light availability to phytoplankton) affected population dynamics, population age and size structure, and individual size at stage (size at first reproduction) of Daphnia hyalina during and after a phytoplankton spring bloom. Mixed layer depth was inversely related to the magnitudes of the phytoplankton spring bloom and the subsequent Daphnia peak, but had no effect on the body size of Daphnia. Conversely, temperature had no effects on abundance peaks but strongly affected the timing of these events. This resulted in at times positive, at other times negative, transient effects of temperature on mean body size, caused by asynchronous changes in population size structure in cold versus warm treatments. In contrast to mean body size, individual size at stage consistently decreased with increasing temperature. We suggest that size at stage could be used as an unbiased response parameter to temperature that is unaffected by transient, demographically driven changes in population size structure.     

Effects of body size and temperature on the metabolic rate of Penaeus monodon

Laboratory measurements of oxygen consumption were made on Penaeus monodon (Fabricius) from protozoea to adult stage at temperatures between 15° and 35°C. The logarithmic relationship between weight-specific respiration rate (WRt) and temperature (T) for two size groups, Protozoea 1 (PZ1) to Postlarva 1 (PL1) and PL to adult, are given as; WRt=10^{0.431+0.0146 (T)} (ml O₂ g^-1 h^-1) and WRt=10^{-0.948+0.0338 (T)} (ml O₂ g^-1 h^-1), respectively. Additionally, equations relating metabolic rate, temperature and size for the two size groups are; PZ1-PL1: log M=0.431+0.0146T+(1.25 (log TL)+0.579), and PL1-adult: log M=-0.948+0.0338T+(2.60(log CL)-0.683), where M=oxygen consumption in ml O₂ individual ^-1h^-1, T=temperature in °C, TL=total length in cm, and CL=carapace length in cm. Activation energies of 6 186.75 J for PZ1-PL1 and 14 066.62 J for PL-adults point to different metabolic pathways or to differences in the ratio between the metabolic pathways used.     

Effects of age and food availability on diel vertical migration of Calanus pacificus

Age-specific differences in diel vertical migration behavior of Calanus pacificus were investigated in a 58 d (30 April–26 June, 1981) experiment in the Scripps Institution of Oceanography Deep Tank, La Jolla, California, USA; the experiment spanned three successive generations of copepods. The onset of vertical migration behavior occurred in the first feeding stage, Nauplius III. The amplitude of vertical migration gradually increased with age, becoming maximal in the late copepodite stages. Night depths remained constant with age while daytime depths increased. The migratory behavior of late copepodite stages was influenced by food availability. When phytoplankton was abundant and individual ingestion rates were high, copepodites performed high-amplitude migrations. As food availability declined, however, and the competition for food increased, migration amplitudes decreased and then ceased altogether so that copepodites remained in the relatively food-rich surface waters at all times. We suggest that hunger is the primary factor controlling vertical migration behavior.     

Effects of food-level acclimation on digestive enzyme activities and feeding behavior of Calanus pacificus

A recent hypothesis in the zooplankton literature states that zooplankton acclimate to ambient food concentrations such that higher digestive enzyme activities and, consequently, higher maximum ingestion rates are achieved at higher food levels. To test this hypothesis, adult female Calanus pacificus, collected from the main basin of Puget Sound, Washington, USA, in August 1979 and May 1982, were conditioned for 2 wk at different concentrations of the diatom Thalassiosira weissflogii (=fluviatilis). Ingestion rates and the activity of the digestive enzymes laminarinase, maltase, and cellobiase were measured periodically during acclimation and in a block-designed feeding experiment at the end of acclimation. Consistent with the hypothesis, maximum ingestion rate and digestive enzyme activity were positively correlated. However, in contrast to the hypothesized mechanism, this result arose because both maximum ingestion rate and digestive enzyme activity were negatively correlated with food concentration during acclimation. The enhanced ingestion of copepods following long-term (12 to 14 d) acclimation to low food is similar to that previously described for short-term (e.g. 1 d) starvation. It might be energetically optimal for copepods experiencing a patchy food environment to maintain higher levels of digestive enzymes at low food concentrations in order to exploit high concentrations of food when encountered.     

Effects of the polycyclic aromatic hydrocarbon fluoranthene on growth rate and nucleic acid composition of Capitella sp. I

Body volume growth rate, dry tissue weight, organic carbon content, and nucleic acid content (RNA and DNA) of individual Capitella sp. I were measured after 14 d of exposure to natural sediment, sediment contaminated with fluoranthene (in acetone) and sediment treated with acetone only. Exposure to 101 μg fluoranthene g⁻¹ sediment dry wt during 2 weeks reduced body volume specific growth rate by 50%. Dry tissue weight and carbon content were also lower in fluoranthene-exposed worms. However, when corrected for differences in body volume, worms from fluoranthene-contaminated sediment had a higher dry weight and carbon content per unit body volume than worms from the control and acetone treatments. Part, but not all, of the reduction in body volume growth rate in response to fluoranthene may have been due to a reduction in tissue water content. The correlation between RNA:DNA ratio (which has previously been used as a predictor of recent growth rate) and worm growth rate was weak in the control group and was significantly influenced by sediment treatment. Not only did the fluoranthene-exposed worms have a lower growth rate than expected based on their RNA:DNA ratio, but analysis of this group separately indicated that measured growth rate was independent of the RNA:DNA ratio. Our results not only confirm previous indications of a weak relationship between nucleic acid content and actual growth, but indicate that empirical, predictive relationships between these variables measured under favorable growth conditions should not be extrapolated to predict growth under toxicant-stressed conditions. Received: 6 April 1997 / Accepted: 7 May 1997     

Temperature acclimation and other influences on embryonic duration in the copepod Pseudocalanus sp.

Embryos of Pseudocalanus sp. captured near Halifax, Nova Scotia, Canada, in spring take longer to develop than do those from the warmer waters of summer and autumn. This is related to the larger size of females and their eggs in the colder seasons. An experiment revealed size-assortative mating and the influence of male size as well on embryonic duration. The seasonal change is contrary to the slight reduction of embryonic duration after short-term cold acclimation of females in the laboratory. There is no evidence that embryos in the cold season develop more rapidly than expected from the overall relationship between embryonic duration and female size. However, they do, like embryos after short-term cold acclimation, develop relatively more rapidly at low temperatures; i.e., there is clockwise rotation of the rate-temperature response, equivalent to the temperature adaptation that has been demonstrated among species of copepods. This seasonal rotation may also be related to seasonal variations in size, since larger females from a given season produce embryos that show such rotation. Thus, there is no evidence for seasonal compensation as a consequence of temperature acclimation underlying changes that are attributable to differences in size. Evidently there is also a strong genetical component in duration of development of embryos produced by individual females.     

The theoretical basis for estimating phytoplankton production and specific growth rate from chlorophyll, light and temperature data

Phytoplankton maximum specific growth rate, μ_max, and maximum photosynthetic quantum yield, Φ_max, can be related mathematically via the photosynthetic light curve, P(I). A model is presented in which maximum quantum yield defines the initial slope of the light curve and is assumed to be a known constant, while maximum specific growth rate defines the light-saturated region of the curve and is assumed to be a known function of temperature. The effect of introducing μ_max(T) into P(I, Φ_max) is to replace the unknown, temperature-dependent light saturation parameter with a term involving the ratio μ_max/Φ_max. The advantage of writing P(I) in terms of both μ_max and Φ_max is that those parameters are particularly well documented in the literature. Consequently, estimates of nutrient-unlimited phytoplankton growth and production rates can be based solely on the constants μ_max, Φ_max and k_c (light absorption per unit of chlorophyll) and the free variables light, temperature and chlorophyll concentration. Rate estimates appear to be accurate to within a factor of two for an extremely wide range of conditions.One particularly significant result of introducing μ_max into P(I, Φ_max) is that the carbon : chlorophyll ration, θ, appears explicitly. It is possible to derive an expression for optimum θ based on the assumption that adaptive changes in carbon/chlorophyll occur so as to maximize the specific growth rate for given conditions of light and temperature. Laboratory and field data are compiled from the literature to test the formulae presented here.     

Energetics of Euphausia pacifica. I. Effects of body carbon and nitrogen and temperature on measured and predicted production

Laboratory production during the life span of Euphausia pacifica was measured directly (as the sum of growth, molting and reproduction) and indirectly (as assimilation minus metabolism and leakage) to test the hypothesis that weight-specific production is a constant for all sizes. Euphausiids were collected in Puget Sound, Washington State, USA, from September 1973 to March 1978. Equations were determined (in terms of carbon and nitrogen at 8° and 12° C) expressing the relationships between body weight and the daily rates of growth, molting, reproduction, ingestion and metabolism. The allometric equation (R=aW ^b ) best related body weight (W) to the rate (R) for growth, molting, ingestion, respiration and excretion for life stages from late larvae through adults. As predicted by the original above hypothesis, the weight-specific coefficient (b) was close to 1.0 for ingestion and excretion; in contrast, b was 0.62 for growth, and 0.77 to 0.85 for molting and respiration. The Q₁₀ s also varied: 3.5 for growth, 2.4 for molting, about 3.0 for ingestion, and 2.0 for respiration and excretion. Assimilation efficiencies, for all weights and at both temperatures, were 81.3% of carbon and 85.9% of nitrogen ingested. The relationships between rate and body weight of early larvae for growth and molting were linear, as was the relationship for reproduction in adults. Weight-specific production was higher by I to 2% at 12° than 8° C for all life stages, and was 2 to 4% for carbon and 2 to 6% for nitrogen in adults, but 13 to 17% for carbon and 14 to 15% for nitrogen in early furcilia larvae. The null hypothesis was rejected for production measured directly, but would have been accepted if only an indirect measurement of nitrogen production had been considered. Clearly, indirect measurement incorporates all errors of measurement and assumption and makes interpretation difficult.     

不同氮源对4种海洋微藻生长的影响

采用实验室一次性培养的方法,研究了硝氮、氨氮、尿素和混合氨基酸等4种不同氮源对典型赤潮藻赤潮异弯藻Heterosigma akashiwo、凯伦藻Karenia sp.、球形棕囊藻Phaeocystis globosa和常见浮游植物优势种类角毛藻Chaetoceros sp.生长的影响。结果表明,这4种海洋微藻不仅能利用无机氮硝氮和氨氮,而且也均能利用有机氮尿素和混合氨基酸。赤潮异弯藻、凯伦藻和角毛藻均在以硝氮为唯一氮源时,比生长速率分别达到最大值0.45、0.52和0.70 d-1;而球形棕囊藻在以硝氮和尿素为唯一氮源时,比生长速率均达最大值0.65 d-1。可溶性有机氮库中的重要组成成分尿素和氨基酸均能显著促进4种海洋微藻的生长;相比较而言,赤潮异弯藻和凯伦藻更加喜好有机氮氨基酸,而球形棕囊藻和角毛藻更加喜好尿素。海洋微藻具备利用有机氮源的能力,无疑扩展了其氮营养来源,在无机氮缺乏而有机氮丰富的水体中,它们在浮游植物群落中更具有竞争优势。     

Influence of pH, salt concentration and temperature on the growth of Aeromonas hydrophila

The influence of environmental factors on the growth of Aeromonas hydrophila was investigated Four isolates (AH 37, AH 79, AH 86 and AH 100) were exposed to various environmental factors such as pH, salt concentration and temperature in laboratory condition. All the four isolates showed more or less similar growth at pH 7.0, 8.0 and 9.0 at 30 degrees C and 5 degrees C. At pH 5.0, 6.0 and 10.0, the log number of cells was found to be lesser than that of pH 7.0, 8.0 and 9.0 at both 30 degrees C and 5 degrees C. The results of the influence of salt concentration on the growth of Aeromonas hydrophila revealed that NaCl concentration of 0.5%, 1.0% and 2.0% favored the growth of this organism at both 30 degrees C and 5 degrees C. Increase in the salt concentration resulted in the growth of the decrease of this organism. Three percentages and 4% salt concentration moderately supported the growth of the organisms in the medium whereas at 5.0% NaCl concentration, there was no growth. Moderate growth of A. hydrophila at 5 degrees C is an interesting observation. The ability to grow at salt concentration between 0.5%, 4.0% under acidic and alkaline conditions pose a problem in the preservation of seafoods. These criteria may account for modified preservation techniques.     

Influence of food quantity and temperature on development and growth of the marine copepod Calanus chilensis from northern Chile

An experiment under laboratory conditions was conducted to test the hypothesis that development and growth of copepodite stages in Calanus chilensis are temperature-dependent and not subject to food shortage in the upwelling area of the Humboldt Current, northern Chile. Field data obtained from June 1994 to May 1995 in Bahía Mejillones (23°S) were used to define four combinations of temperature and food under which copepodites were reared from Stage CIII to adulthood. The high temperature was 18.1 °C and the low temperature 13.1 °C, whereas the high food level was in the range of 6.8 to 24.8 μg l⁻¹ chlorophyll a and the low level 1.0 to 6.8 μg l⁻¹ chlorophyll a. As food a mixture of three unknown species of phytoflagellates and the diatom Navicula cryptocephala was used. This phytoplankton was initially obtained from the same sampling sites as copepods and kept in f/2 media at stable levels and composition throughout the experiment. The development rate (1/t), estimated from the time (t) elapsing between Stage CIV and adult, was significantly affected by both temperature and food, although low-food effects were much more remarkable. Low-food conditions also significantly reduced body length and “structural” (lipid-discounted) body mass at adulthood, while temperature only affected body length. The weight-specific growth rate was also affected by food and temperature, but again food effects were much more drastic. The results indicate that C. chilensis is a highly sensitive species to lack of food, and is possibly subject to food shortage during its annual cycle in the coastal upwelling area of northern Chile. Food limitation may help explain the seasonal pattern of adult size reported by previous studies in the area and the lack of consistence between the number of generations predictable from a temperature-dependent model and that observed in the field during the annual cycle. Received: 10 September 1996 / Accepted: 29 October 1996     

Influence of algal concentration and temperature on the filtration rate of Mytilus edulis

The filtration rates of Mytilus edilis (=galloprovincialis; 40 mm) were determined in relation to food concentration and temperature, using pure suspensions of the unicellular alga Platymonas suecica in concentrations ranging from 3x10⁵ cells/l to 1.5x10⁸ cells/l. The rate of filtration (ml/h/mussel) generally decreased as cell concentrations increased, and dropped to low values when concentrations above 5x10⁷ cells/l were supplied. The amount of water swept clear varied continuously, and noticeable differences in the filtration activity of M. edulis were observed over short time intervals (5 min). Fluctuations of filtered volumes per unit time were greater with lower than with higher concentrations of algae. The influence of temperature on filtration activity was highest between 5°–15°C and 25°–30°C. A temperature increase from 15° to 25°C resulted in only a slight increase in filtration rate. At 5° and 30°C, filtration dropped to very low values, namely 350 and 100 ml/h, respectively. The temperature coefficients for the filtration rates of M. edulis were determined as: Q₁₀ (5° to 15°C)=4.96; Q₁₀ (10° to 20°C)=1.22. The amount of algae cells ingested per mussel per hour is directly related to food concentration. The maximum number of cells filtered/mussel/h in an algal suspension of 70x10⁶ cells/l was 21.5x10⁵ cells/h. Cell concentrations of up to 40x10⁶ cells/l were swept clear without producing pseudofaeces. The critical cell density for M. edulis was reached at algal concentrations of 70 to 80x10⁶ cells/l. Above these concentrations no normal filtration activity was observed.     

Effects of temperature and body mass on metabolic rates of sprat, Sprattus sprattus L.

Sprat, Sprattus sprattus L., is a small schooling clupeid forming large stocks in several ecosystems. Despite its high trophodynamic impact, little is known about its energy consumption rates. As a central component of a bioenergetic budget, metabolic rates of sprat from 3.11 to 9.71 g wet weight (WW) were measured at nine different temperatures (T) ranging from 9 to 21°C using a computer-controlled intermittent-flow respirometer. Routine metabolism (R _R) was related to T (°C) and WW (g) by R _R = 0.074 WW^1.077 e^{0.080 T}. Standard metabolic rates (R _S) as calculated from the 10% percentiles of the repeated measurements were on average 12% lower and still influenced by continuous swimming activity: R _S = 0.069 WW^1.073 e^{0.078 T}. We interpret the deviation of the scaling exponent b from typically found exponents of b ~ 0.8 as a consequence of permanently elevated activity level. The high permanent swimming activities also indicated that the concept of standard metabolism may not be meaningful in schooling planktivorous fish. These results suggest that generally in bioenergetic models for clupeid schooling fish the activity multipliers should be chosen very conservatively.     

Effects of zooplankton diel vertical migration on a phytoplankton community: A scenario analysis of the underlying mechanisms

A mechanistic model was applied to study the influence of diurnal vertical migration (DVM) of planktonic crustaceans on the succession and composition of the phytoplankton community. While zooplankton was restricted to only one functional group, the phytoplankton community was divided into two functional groups which are distinguished by their maximum growth rates and vulnerability to zooplankton grazing. DVM causes a pulsed grazing regime and may also entail a corresponding reduction of the cumulative daily rates of ingestion and losses of zooplankton. To study the relative importance of these two mechanisms of DVM to phytoplankton we performed a scenario analysis consisting of 5 different scenarios. The results show that DVM has a strong influence on the phytoplankton community. Well edible algae benefit during the first 3–4 weeks of summer stratification by reduced daily grazing. The typical shift from small, well edible algae to larger, poorly or non-edible phytoplankton is distinctly delayed. Under the assumption of unchanged daily grazing, however, a pulsed grazing regime has nearly no influence on the resulting phytoplankton composition. As similar effects are also found for completely non-edible phytoplankton, indirect effects via phosphorus availability must be assumed. Thus, the scenario analysis reveals that the observed effects of DVM on phytoplankton can be explained by a combination of two mechanisms: (1) reduction of the daily zooplankton grazing, and (2) changed assimilation and remineralisation of phosphorus. Surprisingly and in contradiction to earlier reports there is almost no DVM effect on phytoplankton due to the sole action of a pulsed grazing regime.     

Growth and development of Calanus spp. (Copepoda) during spring phytoplankton succession in the North Sea

Experiments were carried out to determine growth and development rates of the herbivorous copepod Calanus finmarchicus (Gunnerus) under natural conditions during the phytoplankton spring bloom in the northern North Sea. From 28 April to 25 May 1983 copepodite stages I, IV and V were incubated for a 3-d period on board a ship in vessels with naturally occurring phytoplankton or cultured algae as food. Highest rates of growth and development were achieved while the diatom Chaetoceros sp. was the dominant phytoplankton organism. These rates decreased considerably when this chain-forming diatom was succeeded after one week by the small-celled diatom Thalassiosira conferta. Again one week later, during the bloom of the succeeding colonial microflagellate Corymbellus aureus, copepodite stage IV still managed to maintain moderate rates of growth and development, but these rates dropped to almost zero in CV, suggesting the start of a resting stage. Nevertheless, brood collected from this generation and from Calanus helgolandicus (Claus) was raised in the laboratory to the adult stage at high speed. Since temperature and the total phytoplankton concentration in the sea remained almost constant it seems that the retardation and arrestment of growth and development were an immediate response to a qualitative change of the food composition related to the successive blooms of different algal species.     

The influence of seawater temperature on zooid size and growth rate in Pentapora fascialis (Bryozoa: Cheilostomata)

Zooid size variation and growth banding in the bryozoan Pentapora fascialis, collected from the South of Great Britain to the South of Italy, were investigated in order to test their relationship with the variation of seawater temperature. Zooid length appeared to be more sensitive than zooid area and width to temperature variation. The longest zooids were budded in localities that typically experience low seasonal variation in temperature (3.2–7.5°C) and low mean annual temperature (about 11°C). Zooid length demonstrated the strongest relationship with the range of seasonal variation in temperature rather than the mean annual temperature. Growth bands produced during colder months were less high than those produced during warmer months. Measurements of these alternating bands were used to calculate growth rate of the laminae, ranging from 20.7 at Plymouth to 29.3 mm year⁻¹ at Tino Island. Significant differences in zooid length were found between the two bands, with longer zooids within the band developed in colder months and shorter zooids in bands produced in the warmer period. We conclude that zooid size can be used as an environmental proxy of the seasonal temperature regimes experienced by the species.