Size–frequency dynamics of NE Pacific abyssal ophiuroids (Echinodermata: Ophiuroidea)

The 17-year time-series study at Station M in the NE Pacific has provided one of the longest datasets on deep-sea ophiuroids to date. Station M is an abyssal site characterized by low topographical relief and seasonal and interannual variation in surface-derived food inputs. From 1989 to 2005, over 31,000 ophiuroid specimens were collected. Size–frequency distributions of the four dominant species, Ophiura bathybia, Amphilepis patens, Amphiura carchara and Ophiacantha cosmica, were examined for recruitment and the role of surface-derived food supplies on body size distributions. Juveniles were collected in sediment traps and used to investigate settlement patterns and seasonality. Trawl samples showed no indication of seasonal changes in recruitment to larger size classes; however, there was evidence of seasonal settling of juveniles. Interannual differences in median disk diameters and size distributions of trawl-collected adults are greater than those at the seasonal scale. Three of the four species, O. bathybia, A. patens and O. cosmica, had co-varying monthly median disk diameters, suggesting they may have a similar factor(s) controlling their growth and abundance. Interannual differences in monthly size distributions were generally greater than those between seasons. Cross-correlations between the particulate organic carbon (POC) flux (food supply) and size distribution indices for O. bathybia, A. patens and O. cosmica all were significant indicating that increases in food supply were followed by increases in the proportion of smaller size classes after approximately 17–22 months. These findings suggest that food inputs are indeed an important factor influencing deep-sea ophiuroid populations on interannual time scales, more generally supporting the long-hypothesized connection between food availability and population size structure in the deep sea. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Saving by freezing? Metabolic rates of<Emphasis Type="Italic"> Adamussium colbecki</Emphasis> in a latitudinal context

Standard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O ₂ g ^-1 h ^-1) and "winter" (106.52±39.65 µl O ₂ g ^-1 h ^-1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage.     

Vertical distribution of larvae of Euphausia nana and E. similis (Crustacea: Euphausiacea) in Sagami Bay and Suruga Bay,Central Japan

Vertical distributions of the larval stages of Euphausia nana Brinton and E. similis G. O. Sars in Sagami Bay and Suruga Bay, Central Japan were studied. Most of the metanauplius larvae of E. nana occurred between 25 and 80 m depth, and they were found at greater depths than the eggs and calyptopis larvae. The nauplii and metanauplii of e. similis were mainly found between 50 and 100 m depth, and they also occurred deeper than the eggs and calyptopes. The larvae of the two species from calyptopis I demonstrate diurnal vertical migration. However, this phenomenon was not clear in the season (March) when a seasonal thermocline was absent. Calyptopes and fruciliae of E. similis occurred deeper and migrated over greater vertical distances than those of E. nana. The distance of migration of furcilia I larvae of E. similis was estimated to be about 200 m.     

Trophic impact, metabolism, and biogeochemical role of the marine cladoceran Penilia avirostris and the co-dominant copepod Oithona nana in NW Mediterranean coastal waters

In this work we studied the trophic ecology and feeding impact of the cladoceran Penilia avirostris and the cyclopoid copepod Oithona nana, the two dominant zooplankters in the summer communities of the coastal NW Mediterranean, on the naturally occurring microbial communities. In order to ascertain carbon surplus for growth and reproduction and the contribution to carbon and nitrogen recycling of these two species, we also determined their basal metabolism and excretion rates. The experiments conducted during summers 2002, 2003, and 2004 indicate that P. avirostris grazed mostly upon small flagellates, dinoflagellates, and diatoms, whereas O. nana had a narrower prey range, selecting motile organisms such as ciliates and occasionally dinoflagellates. The grazing impact of both species accounted, on average, for <10% of the standing stock of the microbial groups considered. In spite of the oligotrophic conditions, the feeding activity of P. avirostris is in general sufficient to compensate basal metabolism and allows a surplus for growth and reproduction. This was not the case for O. nana, its daily rations being often lower than the carbon basal demands. Regarding excretion rates, both species presented different N:P excretion ratios, the ones of O. nana falling within values typical for copepods, whereas the absence of detectable phosphorus excretion by P. avirostris implied an unbalance recycling with respect to typical Redfield ratio composition of marine seston.     

Metabolic activity and elemental composition of krill and other zooplankton from Prydz Bay,Antarctica, during early summer (November–December)

Oxygen uptake and ammonia excretion rates, and body carbon and nitrogen contents were measured in krill (Euphausia superba) and eight other zooplankton species collected during November–December 1982 in the Prydz Bay, Antarctica. From these data, metabolic O:N ratios (by atoms), body C:N ratios (by weight) and daily metabolic losses of body carbon and nitrogen were calculated as a basis from which to evaluate seasonal differences in metabolism and nutritional condition. Comparison of the present data with mid-summer (January) data revealed that early-summer E. superba were characterized by higher metabolic O:N ratios (58.7 to 103, compared with 15.9 to 17.5 for mid-summer individuals). Higher O:N ratios of early-summer E. superba resulted largely from reduced ammonia excretion rates and, to a lesser degree, from slightly increased oxygen uptake rates. Body C:N ratios of E. superba were low in early-summer (3.8 to 4.2) compared with mid-summer krill (4.1 to 4.7) due to lowered body-carbon contents in the former (42.6 to 43.6% compared with 43.2 to 47.5% dry weight of midsummer individuals); gravid females formed an exception, since no seasonal differences in body elemental composition were detected for these. No significant changes in water content (75.3 to 81.4% wet wt) and nitrogen content (9.9 to 11.1% dry wt) in E. superba were evident between the two seasons. Seasonal differences in metabolic rates and elemental composition were less pronounced in a salp (Salpa thompsoni), but a higher metabolic O:N ratio occurred in early-summer individuals. Interspecific comparison of the seven remaining zooplankton species studied with twelve species from mid-summer zooplankton investigated in an earlier study indicated that higher metabolic O:N ratios in early-summer are characteristic not only of herbivore/filter-feeders, but also of some carnivores/omnivores. No relationship between metabolic O:N ratios and body C:N ratios was apparent either intraspecifically or interspecifically, within or between early-summer and mid-summer seasons.     

Scavenging deep-sea amphipods: Effects of food odor on oxygen consumption and a proposed metabolic strategy

In situ respiration rates as a response to the odor of food were measured for two species of scavenging amphipods, Paralicella caperesca from 3 650 m in the western North Atlantic Ocean and Orchomene sp. B from 1 300 m in the Santa Catalina Basin off southern California (USA). In addition, complementary laboratory starvation/respiration rates for a shallow-water species, Orchomene sp. A, were determined. Initial elevated O₂ consumption rates were found for up to 8 h in all deep-sea amphipods exposed to bait odor, followed by a period of lowered respiration equivalent to rates observed in individuals not exposed to bait. Orchomene sp. A revealed a response similar to that observed in the deep-sea species. A metabolic strategy is proposed whereby scavenging amphipods efficiently utilize large episodic organic falls in the food-limited environment of the deep sea. This strategy involves (1) the ability to withstand long periods of starvation, (2) rapid response to an organic fall, (3) rapid location of the organic fall, (4) maximal rate of food consumption with maximal quantity ingested, and (5) efficient utilization of the consumed food. Each of these attributes are explored with the expected and observed mechanisms employed to achieve them.     

Mycosporine-like amino acids: possible UV protection in eggs of the sea hare Aplysia dactylomela

We investigated mycosporine amino acid (MAA) involvement as protective sunscreens in spawn of the sea hare Aplysia dactylomela to determine if adult diet and ultraviolet (UV) exposure affected the UV sensitivity of developing embryos. Adults were fed a red alga rich in MAAs (Acanthophora spicifera) or a green alga poor in MAAs (Ulva lactuca). Adults on each diet were exposed for 2 wk to ambient solar irradiance with two types of acrylic filters; one allowed exposure to wavelengths >275 nm (designated UV) and one to wavelengths only >410 nm (designated NOUV). Spawn from each adult group was likewise treated with UV or NOUV and monitored during development for differences in mortality and metabolic rate (measured as oxygen consumption: V˙ _O2). Also recorded were number of eggs or embryos per capsule, times to hatching, hatching success, size at hatching, and V˙ _O2 of adults. Spawn from adults eating red algae was almost twice as rich in MAAs as spawn from adults eating green algae, suggesting that MAA content is diet-related. Although overall quantities of MAAs in the spawn reflected MAA contents of the adult diet, specific MAAs were differentially sequestered in the spawn. Thus, porphyra-334, found in high concentration in Aplysia dactylomela's preferred red algal food, was present in only low concentration in the spawn. Conversely, mycosporine-glycine, in low concentration in red algal food, was the most abundant MAA in the spawn. UV treatment of adults had no effect on quantities of MAAs in the spawn. Adults exposed to UV had significantly higher V˙ _O2s and spawned twice as often. The UV-treated adults produced spawn with significantly higher V˙ _O2s and their embryos developed to hatching sooner. The only significant effect of UV exposure of the spawn was to reduce the percentage of veligers hatching from 71 to 50%. There was no significant effect on hatching time or size of the veligers at hatching, nor on number of eggs per capsule. Received: 13 May 1997 / Accepted: 27 June 1997     

Influence of seasonal variation in temperature, salinity and food availability on module size and colony growth of the estuarine bryozoan Conopeum seurati

Zooid size and colony growth of the estuarine bryozoan Conopeum seurati (Canu) (order: Cheilostomatida; suborder: Malacostegina) were examined over 15 mo at Avonmouth Dock, Avon, England. Data were analysed in conjunction with synchronous measurements of temperature, salinity and food availability. Zooid length, width and area were strongly temperature-dependent, while both food availability and colony growth rate had no significant effect on zooid length, width or area. Salinity and the interaction of temperature and salinity significantly influenced zooid length and area, suggesting that changes in zooid size may result from oxygen limitation in warm waters. The validity of a number of other mechanisms proposed to account for temperature-related changes in zooid size is discussed. The results support the use of zooid size as an indicator of both long-term trends and seasonal variations in temperature in Recent and fossil assemblages as long as data sets are large and the effects of other factors on zooid size are considered. Colony growth rate was found to be significantly influenced by both the amount of food available to the colonies and the combined effect of temperature and food availability, suggesting that growth rate increases as food increases, but that the former may be limited at low temperatures when metabolic rates are low. Received: 30 March 1999 / Accepted: 24 September 1999     

Feeding dynamics of Octopus mimus (Mollusca: Cephalopoda) in northern Chile waters

The natural feeding of 485 Octopus mimus (164 to 3088 g) was studied in relation to the species' life cycle and environmental seasonal variations off the north of Chile from autumn 1991 to summer 1992. Analysis of digestive-tract contents revealed that O. mimus preyed upon 25 different prey items belonging to five zoological groups (Teleostei, Mollusca, Crustacea, Echinodermata and Polychaeta). Cannibalism was only occasional. The results indicate that the diet and food intake of this species are significantly affected by sex and maturation. Senescent individuals ingest a small amount of food, and their diet is mainly based on small, not very motile prey. The food intake, expressed as body weight, of non-senescent individuals is higher in females than in males. Seasonal changes in sea-water temperature seem to be followed by adjustments in food intake. Like other Octopus species, O. mimus appears to be an opportunistic predator.     

Physioecology of zooplankton. I. Effects of phytoplankton concentration,temperature, and body size on the growth rate of Calanus pacificus and Pseudocalanus sp.

Changes in dry weight and in weight-specific growth rates were measured for copepodite stages of Calanus pacificus Brodsky and Pseudocalanus sp. cultured under various combinations of phytoplankton concentration and temperature. Mean dry weight of early copepodites was relatively unaffected by either food concentration or temperature, but mean dry weight of late stages increased hyperbolically with food concentration and was inversely related to temperature. The food concentration at which maximum body weight was attained increased with increasing temperature and body size, and it was considerably higher for C. pacificus than for Pseudocalanus sp. This suggests that final body size of small species of copepods may be determined primarily by temperature, whereas final body size of large species may be more dependent on food concentration than on temperature. Individual body weight increased sigmoidally with age. The weight-specific growth rate increased hyperbolically with food concentration. The maximum growth rate decreased logarithmically with a linear increase in body weight, and the slope of the lines was proportional to temperature. The critical food concentration for growth increased with body size proportionally more at high than at low temperature, and it was considerably higher for C. pacificus than for Pseudocalanus sp. Because of these interactions, early copepodites optimized growth at high temperature, even at low food concentrations, but under similar food conditions late stages attained higher growth at low temperature. The same growth patterns were found for both species, but the rates were significantly higher for the larger species, C. pacificus, than for the smaller one, Pseudocalanus sp. On the basis of findings in this study and of analyses of relationships between the maximum growth rate, body size, and temperature from other studies it is postulated (1) that the extrapolation of growth rates from one species to another on the basis of similarity in body size is not justified, even for taxonomically related species; (2) that the allometric model is inadequate for describing the relationship between the maximum weight-specific growth rate and body size at the intraspecific level; (3) that the body-size dependence of this rate is strongly influenced by temperature; and (4) that species of zooplankton seem to be geographically and vertically distributed, in relation to body size and food availability, to optimize growth rates at various stages of their life cycles.Contribution No. 1127 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Assessment of total and organic vanadium levels and their bioaccumulation in edible sea cucumbers: tissues distribution,inter-species-specific,locational differences and seasonal variations

The objective of this study is to investigate the levels, inter-species-specific, locational differences and seasonal variations of vanadium in sea cucumbers and to validate further several potential factors controlling the distribution of metals in sea cucumbers. Vanadium levels were evaluated in samples of edible sea cucumbers and were demonstrated exhibit differences in different seasons, species and sampling sites. High vanadium concentrations were measured in the sea cucumbers, and all of the vanadium detected was in an organic form. Mean vanadium concentrations were considerably higher in the blood (sea cucumber) than in the other studied tissues. The highest concentration of vanadium (2.56 μg g⁻¹), as well as a higher degree of organic vanadium (85.5 %), was observed in the Holothuria scabra samples compared with all other samples. Vanadium levels in Apostichopus japonicus from Bohai Bay and Yellow Sea have marked seasonal variations. Average values of 1.09 μg g⁻¹ of total vanadium and 0.79 μg g⁻¹ of organic vanadium were obtained in various species of sea cucumbers. Significant positive correlations between vanadium in the seawater and V _org in the sea cucumber (r = 81.67 %, p = 0.00), as well as between vanadium in the sediment and V _org in the sea cucumber (r = 77.98 %, p = 0.00), were observed. Vanadium concentrations depend on the seasons (salinity, temperature), species, sampling sites and seawater environment (seawater, sediment). Given the adverse toxicological effects of inorganic vanadium and positive roles in controlling the development of diabetes in humans, a regular monitoring programme of vanadium content in edible sea cucumbers can be recommended.

     

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     

Light quality in relation to growth,photosynthetic rates and carbon metabolism in two species of marine plankton algae

The effect of light quality on growth, photosynthesis and carbon metabolism in two species of marine algae,Cyclotella nana (Hustedt) andDunaliella tertiolecta (Butcher), was examined. Relative growth constants forC. nana were 0.37, 0.29 and 0.25 in blue, white and green light, respectively. Corresponding constants were 0.41, 0.31 and 0.29 forD. tertiolecta. Photosynthetic rates in both species were higher in blue light and lower in green light compared with white light of the same intensity. More than 60% of¹⁴C assimilated byC. nana orD. tertiolecta grown in blue or green light was incorporated into the ethanol-insoluble fraction, compared with 10 to 30% in this fraction in white light. The relative importance of the various components within this fraction was independent of light quality. Although less¹⁴C was assimilated into the ethanol-soluble fraction in blue or green light, there was a relative increase in some amino acids and organic acids in this fraction and a decrease in sugars and sugar phosphates relative to white light of the same intensity. These differences were independent of light intensity, photosynthetic rate and cell density in the cultures.     

A comparison of meal size and feeding rate of the lysianassid amphipods Anonyx nugax,Onisimus (=Pseudalibrotus) litoralis and Orchomenella pinguis

Lysianassid amphipods were collected in 1987 from Frobisher Bay, Baffin Island, and from the Mingan Archipelago, Gulf of St Lawrence. Meal size and feeding rate of Anonyx nugax (Phipps), Onisimus (=Pseudalibrotus) litoralis (Krøyer) and Orchomenella pinguis (Boeck) were estimated directly, gravimetrically and/or from predictive equations. Size-specific ingestion was greatest in A. nugax, which fed swiftly and efficiently in comparison to O. litoralis and O. pinguis. These two latter species dispersed some bait while feeding and crawling on its surface. Groups of lysianassids fed more wastefully than single individuals. Meal size of females of O. litoralis decreased with increasing maturity, while berried females of O. pinguis consumed less food than mature males. Up to 30 d of starvation had no effect on survival and feeding ability of A. nugax, but 10 to 15 d of starvation dramatically reduced feeding ability or killed O. litoralis and O. pinguis. Differences between meal size, feeding rate and survival point to divergent feeding patterns, which also have been evidenced elsewhere by analysis of gut contents. O. litoralis and O. pinguis are best characterized as facultative scavengers, while large A. nugax are possibly obligate carnivores. Results emphasize the importance of lysianassid amphipods, particularly A. nugax, as bait stealers and as predators of commercial species trapped by various fishing gear.     

One size fits all: stability of metabolic scaling under warming and ocean acidification in echinoderms

Responses by marine species to ocean acidification (OA) have recently been shown to be modulated by external factors including temperature, food supply and salinity. However the role of a fundamental biological parameter relevant to all organisms, that of body size, in governing responses to multiple stressors has been almost entirely overlooked. Recent consensus suggests allometric scaling of metabolism with body size differs between species, the commonly cited ‘universal’ mass scaling exponent (b) of ¾ representing an average of exponents that naturally vary. One model, the Metabolic-Level Boundaries hypothesis, provides a testable prediction: that b will decrease within species under increasing temperature. However, no previous studies have examined how metabolic scaling may be directly affected by OA. We acclimated a wide body-mass range of three common NE Atlantic echinoderms (the sea star Asterias rubens, the brittlestars Ophiothrix fragilis and Amphiura filiformis) to two levels of pCO₂ and three temperatures, and metabolic rates were determined using closed-chamber respirometry. The results show that contrary to some models these echinoderm species possess a notable degree of stability in metabolic scaling under different abiotic conditions; the mass scaling exponent (b) varied in value between species, but not within species under different conditions. Additionally, we found no effect of OA on metabolic rates in any species. These data suggest responses to abiotic stressors are not modulated by body size in these species, as reflected in the stability of the metabolic scaling relationship. Such equivalence in response across ontogenetic size ranges has important implications for the stability of ecological food webs.     

Some observations on the influence of salinity on growth and photosynthesis inPorphyra umbilicalis

Notwithstanding the great importance of the salinity factor in the marine environment, the knowledge of influence of salinity on growth of marine benthic algae is very limited. Rate of growth (mg, cm²) and O₂ output of the intertidal red algaPorphyra umbilicalis from Helgoland, North Sea, were measured during a 3 week culture in 3 different salinities (1/2-, 1- and 2-concentrated artificial sea water; Table 1). Under hypertonic conditions (2-concentrated sea water) growth rate and photosynthesis rate were depressed, compared to values obtained in normal concentrated sea water. Under hypotonic conditions (1/2-concentrated sea water), growth expressed in mg was the same as in normal concentrated sea water, or higher when expressed in cm³. Rate of O₂ output was almost unaltered in one of the two experiments, lowered in the other. Cell size increased at higher salinity, while swelling of cell walls and intercellular substances as well as the intensity of colouring decreased with salinity. The discrepancies between growth and photosynthesis under hypotonic conditions cannot be completely explained by the observed influences of salinity on morphological structures (cell size, swelling of cell substances). Detailed studies on the time course of photosynthesis and respiration rates, and preparation of a metabolic balance for the algae are necessary.     

Sexual reproduction in the corallimorpharian sea anemone Corynactis californica in a central California kelp forest

The seasonal cycle of sexual reproduction in the corallimorpharian sea anemone Corynactis californica (Calgren, 1936) was studied for 18 consecutive months (July 1987 to December 1988) at a subtidal area in the Hopkins Marine Refuge (HMLR), Pacific Grove, Monterey Bay, California. Samples were collected, histological sections were prepared, and gametocytes were examined and measured. C. californica grows by multiple or longitudianl fission to form single-sexed clones of various color and size. In female clones, oocytes appeared in late August and early September; they increased in size steadily in fall, and peaked in early December in both years. In male clones, spermatogenesis was synchronous with the female oogenic cycle, and motile sperm were observed in most testes in early December. Spawned gonads were found in both sexes from late November to early December. Spawning was induced in the laboratory in early December, and external fertilization was followed by development of free-swimming larvae. Gametogenesis and spawning are correlated with seasonal increases in seawater temperature and phytoplankton abundance, and we discuss and compare timing of sexual reproduction in this corallimorpharian to those in several actiniarian and scleractinian species.     

Metabolism of epipelagic tropical ctenophores

Measurements of respiration and excretion at 25°C were made for five species of ctenophores collected during five cruises to the Bahamas (1982–1984). The mean element-specific respiration and ammonium excretion rates of freshly collected specimens of all species ranged from 4 to 16% d^-1, the mean atomic O:N ratios were 10 to 16, and ammonium averaged 60 to 90% of the total dissolved nitrogen excreted. For adult ctenophores, the carbon content ranged from 0.6% carbon (as percent of dry weight) for Bolinopsis vitrea to 3.7% carbon for Beroë ovata. There was a marked increase in the organic content (% carbon of dry weight) of small Bolinopsis vitrea with tentacles compared to fully lobate adults. B. vitrea had increasingly higher metabolic rates when held at food concentrations up to 100 copepods 1^-1 (about 250 g C 1^-1). The overall range between starved and well-fed B. vitrea was about two times for respiration and a factor of three for ammonium excretion. B. vitrea decreased from well-fed to a starved metabolic rate in about a day after removal from food. The metabolic rate of Eurhamphaea vexilligera was not measurably affected by short-term starvation or feeding (maximum 25 copepods 1^-1). In feeding experiments, E. vexilligera of 20 to 56 mm length fed at rates equivalent to clearance rates of 250 to 1 800 ml h^-1.     

Effects of Olisthodiscus luteus on the growth and abundance of Tintinnids

The effects of the red tide flagellate Olisthodiscus luteus Carter on the growth of two tintinnid species, Tintinnopsis lubulosoides Meunier and Favella sp. (Clap. & Lach.) Jorg., were measured in batch culture. T. tubulosoides and Favella sp. grew at rates equivalent to 1.2 (10°C) and 2.0 (20°C) population doublings per day, respectively, when offered nutritionally adequate phytoplankton species. The growth rates of both tintinnid species were reduced in the presence of 10²–10³ O. luteus cells · ml^-1 in multialgal treatments. Growth rate inhibition was proportionately greater at higher O. luteus densities. Lethal effects were observed for both tintinnid species at O. luteus concentrations of 5x10³ cells · ml^-1 in multi-algal treatments. T. tubulosoides mortality occurred at all O. luteus concentrations in unialgal culture. O. luteus-conditioned medium did not substantially inhibit tintinnid growth when combined with acceptable food species, suggesting that toxicity is induced by ingestion or direct contact with O. luteus cells, or by exposure to a short-lived exudate. In agreement with these results, an inverse relationship between O. luteus concentration and tintinnid abundance was observed in Narragansett Bay, Rhode Island, over a two year period. The small lorica diameter of the species apparently inhibited by these O. luteus blooms suggests a detrimental effect independent of cell ingestion. In addition to the absolute concentration of O. luteus cells, the availability of nutritionally adequate algal food may be an important factor determining the impact of O. luteus blooms on tintinnid populations.Contribution no. 5048 from the Woods Hole Oceanographic Institution     

Respiration and excretion by oceanic salps

Rates of oxygen consumption and ammonium nitrogen excretion were measured on the solitary and/or aggregate generations of ten species of oceanic salps collected by SCUBA divers during cruises in the Atlantic Ocean (1982–1985). Species that were visibly more active had higher metabolic rates than did less active species. Rates were 1.5 to 2 times lower and O:N ratios were lower when salps were held before incubation than when incubation began at the time of collection. Respiration rate showed a better relationship to length than to weight, suggesting that metabolic activity may be connected mainly with swimming. O:N ratios were between 13 and 28 for most species and generations, but higher and more variable in Pegea spp. Exretion of urea was low or undetectable. Rates of metabolic demand (turnover) ranged from 9.7 to 99% body carbon d^-1 and 6.4 to 55.6% body nitrogen d^-1.Contribution No. 5988 from the Woods Hole Oceanographic Institution and No. 412 from the Allan Hancock Foundation