Effects of temperature on the mortality and growth of Hawaiian reef corals

Three common species of Hawaiian reef corals, Pocillopora damicornis (L.), Montipora verrucosa (Lamarck) and Fungia scutaria Lamarck, were grown in a temperature-regulated, continuous-flow sea water system. The skeletal growth optimum occurred near 26°C, coinciding with the natural summer ambient temperature in Hawaii, and was lowest at 21° to 22°C, representing Hawaiian winter ambient. Levels of approximately 32°C produced mortality within days. Prolonged exposure to temperatures of approximately 30°C eventually caused loss of photosynthetic pigment, increased mortality, and reduced calcification. Corals lived only 1 to 2 weeks at 18°C. The corals showed greater initial resistance at the lower lethal limit, but ultimately low temperature was more deleterious than high temperature. Results suggest that a decrease in the natural water temperature of Hawaiian reefs would be more harmful to corals than a temperature increase of the same magnitude.Contribution No. 504 of the Hawaii Institute of Marine Biology.     

Synergistic effects of temperature,salinity and light on the hermatypic coral Montipora verrucosa

Temperature tolerance in the reef coral Montipora verrucosa (Lamarck) is affected by salinity and light. Low salinity reduces ability of the coral to survive shortterm exposure to elevated temperature. High natural light intensity aggravates damage sustained by corals at high temperature. In long-term growth experiments, high light intensity caused substantial loss of zooxanthellar pigment, higher mortality rates, reduced carbon fixation and lowered growth rate at both upper and lower sublethal temperatures Effects of light at optimal temperature were less dramatic. Interactions between physical environmental factors appear to be most important near the limits of tolerance for a given factor. Acclimation capability was indicated, and was influenced by both thermal history and pigmentation state of stressed corals.Contribution No. 543 of the Hawaii Institute of Marine Biology.     

Physiological ecology of four Polysiphonia species (Rhodophyta,Ceramiales)

Photosynthesis and respiration of 4 species of the marine red algal genus Polysiphonia were evaluated under a variety of light, temperature and salinity conditions. The manometric results were compared with the local distribution and abundance of each species. The species can be separated into two distinct categories based on their overall distribution and temperature optima: (1) cold water plants [P. lanosa (L.) Tandy and P. elongata (Hudson) Sprengel], with peak photosynthesis at 21° to 24°C, but with active photosynthesis as low as 5°C; (2) plants with warm-water affinities [P. nigrescens (Hudson) Greville and P. subtilissima Montagne], having photosynthetic optima at 27° to 30°C, and exhibiting little or no photosynthesis below 10°C. The plants from the first group exhibit thermal injury at temperatures of 25°C and show a narrow tolerance to low salinities during periods of high temperatures. The plants from the second group show thermal injury at 30°C and have a wider tolerance to low salinities. The horizontal distribution of the 4 Polysiphonia species within the Great Bay Estuary System of New Hampshire, USA, is primarily governed by their tolerances to high temperatures and low salinities. The temperature optimum for each of the species corresponds to its particular estuarine distribution. Thus, P. subtilissima, having the highest temperature optimum, penetrated furthest into the Estuary, while P. lanosa, having the lowest temperature optimum, was restricted to the more coastal stations. There was a good correspondence between the natural distribution patterns and the manometric results.Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 731.Scientific Contribution No. 4 of the Jackson Estuarine Laboratory.     

Influence of thermal history on the response of <Emphasis Type="Italic">Montastraea annularis</Emphasis> to short-term temperature exposure

Acclimation of reef corals to environmental conditions has been related to metabolic response at large geographic scales, but regional relationships have rarely been described. Physiological responses to temperature increases of Montastraea annularis (Ellis and Solander 1786) from an inner lagoon and an outer barrier reef in the Gulf of Honduras, southern Belize, were compared in May 2003. The hypothesis that inferred differences in thermal history would result in contrasting responses to elevated temperature was tested. Ambient seawater temperatures adjacent to corals at 4–5 m depth were measured every 15 min at inner lagoon and outer barrier reef collection sites for 1 year (June 2002–May 2003). Monthly averages and 3-day running averages (warmest period, July–October 2002) of daily maximum seawater temperatures were significantly higher (by ∼0.5°C) at inner lagoon reef compared to outer barrier reef sites. M. annularis photosynthesis (P) and respiration (R) rates were measured in respirometers at six temperatures between 29°C and 35°C approximately every hour, with repeated measurements over 3 h. P and R were significantly lower across most temperature treatments for samples collected from the inner lagoon compared to outer barrier reef. Both inner and outer reef M. annularis displayed an increase in P and R with increasing temperature between 29°C and 32°C, but above 32°C P and R sharply declined. P/R ratio versus temperature showed a significant difference between the elevations of the regression lines suggesting that M. annularis from the outer barrier reefs may have been more physiologically stressed than those from the inner lagoon reefs when exposed to acute temperature changes. These results emphasize that thermal stress must be considered within the context of acclimation temperature, and that short-term exposures may have physiologically important effects on this species.     

Skeletal Sr content and density in Porites spp. in relation to environmental factors

The coral genus Porites was investigated to evaluate the use of skeletal strontium content as a recorder of seasonal and annual temperature oscillations. In the Hawaiian archipelago, the mean annual water temperature fluctuates by ±0.5C°, with seasonal temperature ranges of 4 to 8C°; the resolution of the Sr thermometer appears to be ±1.5C°. Of this error term, ±0.7C° is analytical, the remainder is biological. Corals from some locations yield temperatures which are consistently offset from the Sr vs temperature calibration line, suggesting genetic population differences. Analysis of cores collected in 1980 from Hawaiian Porites spp. showed no discernible long-term trends over a 100 yr period. Although absolute temperatures are poorly resolved, subannual oscillations in skeletal Sr values accurately reflect recorded seasonal temperature variations. The most useful application of the Sr thermometer is in deciphering the skeletal density band pattern. Subannual oscillations in Sr-temperature values when correlated with density values showed a consistent pattern. When the sections chosen for x-radiography closely followed the growth axis, an abrupt shift from minimum to maximum skeletal density was evident in September/October each year, followed by a gradual decrease in density. The density pattern, shown by microdensitometry, is independent of latitude or temperature range over the Hawaiian archipelago. The annual density shift coincides with high but declining water temperature and solar insolation. If low-density growth represents optimum calcification conditions, the density shift in Hawaiian Porites spp. reflects a change in conditions from optimal to suboptimal. Analyses of samples from other Indo-Pacific locations confirm the generality of this density pattern and suggest a complex relationship between density and environmental light and temperature.Hawaii Institute of Geophysics Contribution No. 1209; Hawaii Institute of Marine Biology Contribution No. 618     

Effect of elevated temperature on aerobic respiration of coral recruits

Metabolic rates provide a valuable means to assess the condition of early life stages of scleractinians, but their small biomass creates a signal-to-noise problem in a confined respirometer. To avoid this problem, measurements of the oxygen diffusion boundary layer (DBL) and Ficks first law were used to calculate the respiration rate of coenosarc tissue on recruits (i.e., colonies 5–14 mm diameter) of Porites lutea (Edwards and Haime, 1860) exposed to two temperatures at a flow speed of 0.6 cm s^–1. All experiments were completed in Moorea, French Polynesia, between November and December 2003. At 26.8°C, the DBL was 565±55 µm thick, the oxygen saturation adjacent to the tissue was 80±3%, and the mean respiration of the coenosarc was 1.2±0.1 µl O₂ cm^–2 h^–1 (all values mean ± SE, n=10). Exposure to 29.7°C for 24–48 h did not affect the DBL thickness but significantly reduced the oxygen saturation adjacent to the tissue (to 74%) and increased the mean respiration rate by 35%. As the small corals differed slightly in size, in a uniform flow speed they experienced dissimilar flow environments as characterized by the Reynolds number (Re), thereby creating the opportunity to test the flow dependency of respiration. At 26.8°C, respiration and Re were unrelated, but at 29.7°C, the relationship was positive and statistically significant. Thus, respiration of small corals may not be mass transfer limited at low temperature, but relatively small increases in temperature may result in an increased metabolic rate leading to mass transfer limitation and flow-dependent rates of respiration.Communicated by J.P. Grassle, New Brunswick     

Mode and timing of reproduction in some common hermatypic corals of Hawaii and Enewetak

Common Hawaiian and Enewetak corals were examined to determine the method and mining of reproduction. Of the 7 Hawaiian species examined for the release of planulae, only 2 have planulated in captivity, Pocillopora damicornis and Cyphastrea ocellina. Both planulate year-round and both are characteristic of reef flats. Four of the 5 species which did not planulate were found to contain eggs, but not planulate, when polyps were examined microscopically. These 5 species do not usually occur on reef flats. Seven of the 12 Enewetak species examined in June, July, August and January planulated; 4 of these were pocilloporids, all of which are common in shallow water. Only 3 of the 8 species of Acropora planulated, and these 3 occur solely in shallow water. A greater proportion of the Pocillopora spp. colonies than Acropora spp. colonies planulated and they released more planulae per head. In previous studies and in this one, coral species which have released planulae are characteristic of shallow-water environments such as reef flats. Most of the 10 species reported on here which failed to planulate in captivity are not commonly found on reef flats. The failure to detect planulation in so many species, particularly those of deeper water, suggests that common hermatypic corals may not all reproduce in the same way, and that mode of reproduction may be related to habitat.     

Some aspects of the thermal tolerance of Trichomya hirsuta (Mollusca: Bivalvia) of Eastern Australia

The upper temperature tolerance range for Trichomya hirsuta L. is described for acclimation temperatures of 10° to 32°C at 30% S. Changes in thermal resistance with time are described along with the incipient lethal temperatures. The eurythermicity for the species is 240.7 C°-squared. The ultimate upper incipient lethal temperature is 35.1°C. Definition of the incipient sublethal temperature is given, and is equal to 32°C. Diet effects are shown not to be significant in short-term lethal experiments, but indicate that unfed mussels reduce their resistance after prolonged exposure to high temperatures. Size was also shown to have no effect on resistance and tolerance. A comparison of the tolerance triangle of T. hirsuta with those of the temperate species Mytilus edulis and Mya arenaria revealed that the 24-h LT₅₀ minus 2.2 C° approximates the incipient lethal temperature. The eurythermicities of the temperate species are Mytilus edulis, 363 C°-squared; and Mya arenaria, 415 C°-squared.     

A comparative study of metabolic energy expenditure in the limpets Patella cochlear,P. oculus and P. granularis

Oxygen consumption of 3 species of Patella was measured in air and water at various temperatures. Measurements at constant temperature over a full tidal cycle showed no tidal or light-dark rhythms. Measurements under conditions simulating natural tidal, temperature and day-night cycles allowed calculation of daily respiratory energy budgets. P. cochlear occurs low on the shore, but experiences a food shortage due to intense intraspecific competition. Its rate of respiration is moderate, but metabolic expenditure is kept low because exposure to air is brief and body temperatures seldom rise above 23°C. P. cochlear has a respiratory rate-temperature (R-T) curve which peaks at 20°C and forms a plateau between 20° and 32.5°C. The midshore P. oculus has abundant food and adopts an exploitative strategy. Growth rate is very high, and this high turnover of energy is linked with a high metabolic rate, high Q10 (temperature coefficient) values, high body temperatures during the day-time low tide, and a respiratory R-T curve peaking at 32.5°C. Small P. oculus occur mainly in intertidal pools and respire faster in water, while larger individuals occur on bare rocks and respire faster in air over the upper temperature range. In contrast, the upper-shore P. granularis has little food, and conservation of energy is essential, particularly as its growth rate is moderate and its reprocurve output high. Respiratory losses are reduced by suppression of the R-T curve and low Q10 values, resulting in relative independence of temperature. Small P. granularis occur low on the shore and respire slower in water. Larger individuals occur at high levels due to migration, and respire slower in air. This further reduces respiratory energy losses. The patterns of respiration in these 3 species are thus related to food availability, resulting in exploitative or conservationist strategies.     

Elevated temperature impairs onset of symbiosis and reduces survivorship in larvae of the Hawaiian coral, <Emphasis Type="Italic">Fungia scutaria</Emphasis>

Many corals obtain their obligate intracellular dinoflagellate symbionts from the environment as larvae or juveniles. The process of symbiont acquisition remains largely unexplored, especially under stress. This study addressed both the ability of Fungia scutaria (Lamarck 1801) larvae to establish symbiosis with Symbiodinium sp. C1f while exposed to elevated temperature and the survivorship of aposymbiotic and newly symbiotic larvae under these conditions. Larvae were exposed to 27, 29, or 31°C for 1 h prior to infection, throughout a 3-h infection period, and up to 72 h following infection. Exposure to elevated temperatures impaired the ability of coral larvae to establish symbiosis and reduced larval survivorship. At 31°C, the presence of symbionts further reduced larval survivorship. As sea surface temperatures rise, coral larvae exposed to elevated temperatures during symbiosis onset will likely be negatively impacted, which in turn could affect the establishment of future generations of corals.     

Population genetics of eight species of Trapezia (Brachyura: Xanthidae), symbionts of corals

Starch-gel electrophoresis was used to study gene-enzyme variation in thirteen populations of eight species of the genus Trapezia from Hawaii, Panamá, and Enewetak Atoll (Marshall Islands). Between 20 and 30 (mean = 27.8) gene-enzyme systems were resolved in each population, with 20 systems in common among all populations. The distribution of electrophenotypes was in agreement with Hardy-Weinberg-Castle expectations, except for T. digitalis, which consistently showed heterozygote deficiencies. Diagnostic loci among color forms support the hypothesis that color forms are distinct species. Low values of genetic distance among species suggest a recent radiation, perhaps during the Pleistocene. Genetic distance between the Hawaiian and Panamanian populations of T. ferruginea did not significantly differ from zero, indicating that the Eastern Pacific population of T. ferruginea has recently immigrated from the central Pacific, and/or that there is gene flow between the two areas. There were diagnostic loci between T. ferruginea and T. formosa from Enewetak and the populations of these species from Hawaii (T. ferruginea only) and Panamá (both species). Therefore, these geographic populations may represent separate species. The level and pattern of genetic variability in Trapezia spp. are in agreement with those observed in most other organisms.     

High-temperature tolerance of photosynthesis in the red alga Chondrus crispus

Chondrus crispus (Stackhouse) is a perennial red seaweed, common in intertidal and shallow sublittoral communities throughout the North Atlantic Ocean. In the intertidal zone, C. crispus may experience rapid temperature changes of 10 to 20C° during a single immerison-emerision cycle, and may be exposed to temperatures that exceed the thermal limits for long-term survival. C. crispus collected year-round at Long Cove Point, Chamberlain, Maine, USA, during 1989 and 1990, underwent phenotypic acclimation to growth temperature in the laboratory. This phenotypic acclimation enhanced its ability to withstand brief exposure to extreme temperature. Plants grown at summer seawater temperature (20°C) were able to maintain constant rates of lightsaturated photosynthesis at 30°C for 9 h. In contrast, light-saturated photosynthetic rates of plants grown at winter seawater temperature (5°C) declined rapidly following exposure to 30°C, reached 20 to 25% of initial values within 10 min, and then remained constant at this level for 9 h. The degree of inhibition of photosynthesis at 30°C was also dependent upon light intensity. Inhibition was greatest in plants exposed to 30°C in darkness or high light (600 mol photons m^-2s^-1) than in plants maintained under moderate light levels (70 to 100 mol photons m^-2s^-1). Photosynthesis of 20°C-acclimated plants was inhibited by exposure to 30°C in darkness or high light, but the degree of inhibition was less than that exhibited by 5°C-grown plants. Not only was light-saturated photosynthesis of 20°C plants less severely inhibited by exposure to 30°C than that of 5°C plants, but the former also recovered faster when they were returned to growth conditions. The mechanistic basis of this acclimation to growth temperature is not clear. Our results indicate that there were no differences between 5 and 20°C-grown plants in the thermal stability of respiration, electron transport associated with Photosystems I or II, Rubisco or energy transfer between the phycobilisomes and Photosystem II. Overall, our results suggest that phenotypic acclimation to seawater temperature allows plants to tolerate higher temperatures, and may play an important role in the success of C. crispus in the intertidal environment.     

Temperature tolerance of the estuarine prawn Upogebia africana (Anomura,Crustacea)

Continuous temperature measurements were made in a typical South East African estuary. Mean summer (November to March) temperatures were in the range 19° to 24°C, and in winter (June to August) from 13° to 16°C. Large daily temperature fluctuations of 6° to 10°C occurred in summer; these appear to result from tidal movement of cool sea water into the estuary. In winter, temperature fluctuations were much smaller (3° to 5°C). The burrowing prawn Upogebia africana (Obtmann) was found to have an upper lethal temperature of 29°C in both winter and summer. The resistance time of prawns to temperatures above 30°C was much greater in summer than in winter. It was possible to acclimate winter prawns and increase their resistance time to a level comparable to that of summer individuals. A latent period of 40 h occurred before acclimation effects were detectable. Long-term exposure of prawns to high temperatures did not increase their resistance above that of summer prawns. Water at a temperature above this upper lethal temperature is not pumped through the burrows. This avoidance behaviour considerably increases the ability of U. africana to withstand short-lived temperature extremes.     

Influence of temperature changes on oxygen uptake and ammonia and phosphate excretion,in relation to body size and weight,in Oikopleura dioica (Appendicularia)

The relationship between the rates of oxygen consumption, ammonia and phosphate excretion of a pelagic tunicate, the larvacean Oikopleura dioica Fol, 1872 were assessed as a function of size, dry weight and ash-free dry weight at 15°, 20° and 24°C. O. dioica has higher respiration and excretion rates than copepods of similar weight, but the weight exponent of the allometric power function: Y=aX ^b is similar to that of other poikilotherms. Temperatures above 20°C have a depressing effect on respiration and ammonia excretion. 90% of the variance in metabolic rates is explainable by body mass and temperatures Q₁₀ values for oxygen consumption, ammonia and phosphate excretion, respectively, are 2.45, 1.86 and 1.75 between 15° and 20°C, and 3.75, 2.90 and 3.60 between 20° and 24°C. Metabolic quotients (O:N, O:P, N:P) indicate a protein-oriented diet. The results of this study suggest weak metabolic regulation in O. dioica, an energetic strategy which allows an immediate response to favourable changes in feeding conditions.     

Experimentelle Untersuchungen zur Ökologie der marinen Kieselalge Thalassiosira rotula. I. Temperatur und Licht

Nearly 500 crabs, Scylla serrata (Forskal) (family Portunidae), ranging in wet weight from 0.2 to 14.0 g, were acclimated to 27° and 35°C and their respiratory metabolism under water and on exposure to air at test temperatures ranging from 16° to 38°C was studied. In aquatic respiration, the response to temperature of crabs acclimated to a temperature of 16°C is statistically significant, and directly related to their weight. Smaller crabs did not survive at the warm acclimation level of 35°C. The metabolic rates of cold-adapted S. serrata are higher than those of warm-adapted ones. The effect of acclimation to aerial respiration on crabs acclimated to cold temperature varied slightly between large and small crabs. The aerial respiration rate was less than a tenth of the aquatic rate for all sizes. The response of S. serrata to warm acclimation in air has been found to be almost opposite to its response in water.This paper formed part of a thesis approved for the award of the degree of Doctor of Philosophy by the Madras University, India.     

Influence of sex and age on the feeding habits of the common soleSolea solea

The lethal concentration of cadmium was determined for the mysidLeptomysis lingvura G.O. Sars, a Mediterranean species from surface coastal waters, and the effect of sublethal doses on respiration, ammonia excretion, and feeding efficiency at different temperatures, and on activities of 19 hydrolases was tested. Experiments were carried out on individuals collected in spring 1987 near Marseille. At 18°C, respiration rate was significantly affected only by concentrations >0.05 mg Cd l^–1. At 0.1 mg Cd l^–1, respiration rate was more significantly depressed at 20°C than at 10°C. There was a concomitant decrease in the Q₁₀ rate (by 23 to 59%, according to the particular experiment), indicating a strong synergistic effect of temperature. Ammonia excretion was likewise affected by cadmium, also with a concomitant decrease in the Q₁₀ rate (by 34%). Daily faecal pellet production was maximum at 18°C; it was inhibited by cadmium at temperatures between 14 and 20°C, and enhanced at extreme temperatures (10 and 22°C). The assimilation efficiency of contaminated individuals was reduced by 9%. These decreases in faecal pellet production and assimilation efficiency reflect a significant decrease in energy (by about 43%) which could rapidly lead to an unbalanced energy budget with a consecutive lowering of the reproductive potential. Generally, hydrolase activities usually increased initially in the presence of 0.2 mg Cd l^–1, but after 48 h they declined, reaching very low values at 72 h. Most physiological processes are therefore affected by exposure to cadmium and the unbalanced energy budget arises from the inability to utilize environmental food. These results are consistent with the literature data on cadmium contamination in marine organisms. Physiological and biochemical changes appear to be very informative in studies of in vitro sublethal effects of micropollutants and in situ environmental modifications.     

Effect of light quality on photosynthesis of the reef coral Montipora verrucosa

Pieces of the reef coral Montipora verrucosa (Lam.), collected from Kaneohe Bay, Oahu, Hawaii in 1982, were grown in four low-light treatments (11% sunlight): blue, green, red and the full spectrum of photosynthetically active radiation (PAR); and at high-intensity full PAR (90% sunlight). These acclimated corals were then tested for photosynthetic ability in blue, green, red, and white light. The photosynthetic parameters that were measured were; ligh-saturated photosynthetic rate, the initial slope of the photosynthesis/irradiance curve, the light intensity where these two lines crossed, and dark respiration. While acclimation intensity had a pronounced effect, the results also showed that the color of the acclimation treatment influenced the photosynthetic responses of the corals. The color of the light used in the measurements of photosynthesis had much less effect on the photosynthetic responses of the corals.Contribution No. 729 of the Hawaii Institute of Marine Biology     

Metabolic adaptation of Cancer irroratus developmental stages to cyclic temperatures

Metabolic-temperature responses of the developmental stages of the sublittoral crab Cancer irroratus cultured at 10° to 20°C daily cyclic and 15°C constant temperatures were determined. Generally, the metabolic rate increased with temperature in the lower range with Q₁₀'s (temperature coefficients) above 2, compensated in the midrange with Q₁₀'s between 1 and 2, and declined at the higher temperatures with Q₁₀ values less than 1. For the larvae cultured at a constant temperature of 15°C, the compensatory response range narrowed with development from first zoeae to the later zoeal stages. In contrast, the compensatory response of the first zoeae, megalops, and crab stages within the range 10° to 25°C was interrupted by a zone of thermal sensitivity between 15° and 20°C for those individuals cultured in the 10° to 20°C cyclic regime. The compensatory response range is narrower for the third stage zoeae and broader for the second, fourth, and fifth stage zoeae. Metabolic rate-temperature (M-T) patterns of C. irroratus developmental stages cultured under the cyclic regime varied from those held at constant temperature by increased respiration and metabolic rate compensation between 20° and 25°C, and by an extension of the metabolically active range towards higher temperatures.     

Cyclical mucous sheet formation on poritid corals in the San Blas Islands,Panama

Mucous sheets are common on poritid corals as well as other reef coelenterates, but the frequency, cause and function of these sheets have rarely been investigated.Porites furcata Lamarck andPorites astreoides Lamarck colonies at three sites in the San Blas Islands, Panama, were monitored for the presence or absence of mucous sheets every 2 d between 11 May and 27 August 1983. Concurrent measurements of polyp expansion, particulate matter concentrations, salinity, water temperature and sedimentation rates were also made at each site. Mucous sheet formation was not correlated with any of the environmental parameters measured. Mucous sheet formation by both species had a lunar periodicity.P. furcata formed mucous sheets around the time of the full moon, whileP. astreoides formed mucous sheets during the first quarter (around a week before full moon). Mucous sheet formation was correlated with polyp contraction behavior and may be a secondary effect of a lunar cycle in polyp activity.     

Combined effects of temperature and salinity on embryos and larvae of the northern bay scallop Argopecten irradians irradians

The combined effects of temperature and salinity on embryonic development and on larval survival and growth to setting size of the northerm bay scallop Argopecten irradians irradians (Lamarck) were studied in the laboratory. A 6x6 complete factorial design was used; temperatures ranged from 10° to 35°C, at 5C° intervals, and salinities ranged from 10 to 35S, at 5S intervals. Response-surface contour diagrams were generated to provide estimates of conditions for optimal responses. Normal development of embryos occurred over a very narrow range of temperature and salinity. Survival of larvae occurred over a wider range of temperature and salinity than did embryonic development or growth of larvae. Satisfactory growth (>70% of the maximum observed value) occurred only at high temperature-high salinity conditions; optimal conditions for survival occurred at similar salinities, but at slightly lower temperatures. Temperatures of 35°C or greater and/or salinities of 10S or less were lethal for all life stages studied. Both salinity and temperature exerted significant effects on development and survival, but temperature was clearly the dominant factor influencing growth. It is suggested that northern bay scallop embryos and larvae be reared at their respective optimal temperature-salinity levels so as to increase efficiency of aquaculture operations.This paper is adapted from a thesis submitted to the College of Fisheries, University of Washington, in partial fulfillment of the requirements for the MS degree. This study was conducted at the NMFS Laboratory in Milford, Connecticut, USA