The relationship between dissolved oxygen concentration and maximum size in deep-sea turrid gastropods: an application of quantile regression

Bathymetric gradients in body size are the most well-known patterns of geographic variation in deep-sea organisms. The causes of size-depth relationships remain uncertain, but most have been attributed to rates of nutrient input. Chapelle and Peck (1999, Nature 399:114-115) recently hypothesized that body size in marine invertebrates is a function of dissolved oxygen concentration. We tested this hypothesis by using quantile regression techniques to assess the relationship of dissolved oxygen levels to maximum size in deep-sea turrid gastropods collected from the North Atlantic. Relationships were examined for a group of nine turrid species and within the abundant lower bathyal species Benthomangelia antonia (Dall, 1881). We controlled the analysis for depth because size in deep-sea gastropods varies bathymetrically. When the effects of depth are accounted for statistically, maximum size in B. antonia increases with increasing levels of dissolved oxygen. In turrids as a group, both depth and oxygen appear to explain significant proportions of the variance in maximum size. These findings suggest that a suite of factors, including dissolved oxygen concentration, may influence maximum size in deep-sea organisms.     

Stable isotopic compositions of hydrothermal vent organisms

Stable isotopic analyses were used to study trophic relationships in two communities of deep-sea hydrothermal vent organism in the Pacific Ocean. The community at Hanging Gardens on the East Pacific Rise (21°N), sampled in 1985, is dominated by two species of vestimentiferan tubeworms; communities at Alice Springs and Snail Pits on the Marianas Back Arc Spreading Center (western Pacific), sampled in 1987, are dominated by gastropod mollusks, barnacles, and anemones. In both locations, carbon and nitrogen isotopic values of vent invertebrates are significantly different from those of non-vent invertebrates collected at 11°N on the East Pacific Rise and elsewhere in the deep-sea. These distinct isotopic compositions reflect local sources of organic carbon and nitrogen used by vent consumers. Many vent invertebrates lacking chemoautotrophic endosymbionts have ¹³C-enriched values of-11 to-16%. compared to values of-17 to-22%. normally observed in deep-sea fauna. This suggests that a ¹³C-enriched food source is trophically important in both vent communities. Free-living bacteria colonizing surfaces and suspended in the water column may constitute this food resource. Nitrogen isotopic analyses show that the food web of the East Pacific Rise community has more trophic levels than the Marianas vent community.     

Depth-related adaptations, speciation processes and evolution of color in the genus Phyllidiopsis (Mollusca: Nudibranchia)

The nudibranch genus Phyllidiopsis (Phyllidiidae) contains 30 currently recognized species, all of them distributed throughout the tropical Indo-Pacific, eastern Pacific, Northwest Atlantic and Caribbean Sea. Half of the known species of Phyllidiopsis inhabit deep waters, and most of the deep-sea species of the Phyllidiidae belong to this genus. There is no definitive explanation for the high diversity of Phyllidiopsis in the deep-sea or for whether diversity could be related to particular adaptations of this group or to historical events. In light of phylogenetic analysis, several cases of vicariance have been detected in this genus. Apparently two major vicariant events occurred between the tropical Indo-Pacific region and the Atlantic-eastern Pacific area first and subsequently between the eastern Pacific and the Atlantic. Vicariant events could also be involved in producing vertical distributional patterns in a few species of Phyllidiopsis. The scarcity of phyllidiids in the Atlantic Ocean may be explained by historical events, including isolation and subsequent extinction in shallow waters. There is a mimicry species complex in Phyllidiopsis, including several members of a clade that probably acquired this coloration through common ancestry, and also including another unrelated species that probably acquired this coloration through convergent or parallel evolution. There is also a group of white species, lacking any other contrasting colors, that inhabits deep waters. This coloration could constitute an adaptation to the deep-sea environment and not a mimicry complex. In this case, all species acquired this coloration through common ancestry.     

Role of echinoderms in benthic remineralization in the Chukchi Sea

The role of large, epibenthic organisms in carbon cycling at high latitudes is difficult to assess using standard ship-board collection techniques. We used a remotely operated vehicle equipped with video imaging to examine the distribution and abundance of epibenthic organisms in the northeast Chukchi Sea during June 1998. At each of 11 sites, we collected between 25 and 50 images from a minimum of 20 min of video. We observed 15 different epibenthic taxa, with the echinoderms (Ophiura sarsia, O. maculata, Ophiopholis aculeata, Stegophiura nodosa, and Echinarachinus parma) overwhelmingly dominating the epibenthos. Echinoderm density was highly variable, ranging from 0.2 to 256.6 individuals m^-2 (median=16.3), and echinoderm biomass varied between <0.5 and 4,988 mg C m^-2 (median=737). The highest biomass of ophiuroids recorded (3,388 mg C m^-2) is 30% higher than the highest previously reported from an Arctic shelf. Using a relationship between biomass and respiration developed for deep-sea organisms living at cold temperatures, we estimated respiration rates from <0.1 to 15.0 mg C m^-2 day^-1 (median=1.9). Respiration rates measured on board were several orders of magnitude higher than those obtained from the predictive equation. Further work is needed to assess echinoderm respiration rates accurately under in situ conditions. Even with calculated minimal values for respiration rates, a comparison of epifaunal and infaunal respiration at four stations revealed that echinoderm respiration accounted for as much as 25% of total respiration. High epifaunal respiration rates and biomass values are likely supported by high concentrations of particulate organic carbon carried by Bering Sea water flowing through the eastern Chukchi Sea. Our observations support observations from the Eurasian Arctic that echinoderms dominate the epibenthos of Arctic shelves and that the role of these organisms in carbon remineralization must be considered if we are to generate accurate models of carbon cycling in the Arctic.     

Temperature and pressure tolerance of larvae of Crepidula fornicata suggest thermal limitation of bathymetric range

The extant deep-sea fauna is thought to result from recolonisation of this environment by shallow-water organisms following climate-driven mass extinctions. Planktonic larval tolerance to high pressure is considered an important preadaptation for successful deep-sea invasion. In this study, the pressure and temperature tolerance of a species without any known confamilial deep-sea relative were assessed for the first time. Early- and late-veliger larvae of the shallow-water species Crepidula fornicata were subjected to a temperature/hydrostatic pressure regime from 5 to 25 °C and from 0.1 to 40 MPa. Although early and late veliger survived pressures equivalent to 2,000 m water depth or greater at all temperatures, decreased larval activity indicated significant sublethal temperature and pressure effects. Reduced larval activity of early veliger at low temperatures suggests that the bathymetric range of this species may be thermally constrained. A mechanistic model is proposed to explain the emerging pattern of ontogenetic shifts in pressure tolerance of shallow-water benthic invertebrates.     

Hydrothermal vent communities at the shallow subpolar Mid-Atlantic ridge

A new type of animal community has been found near hot vents in the subpolar Atlantic at 100 to 106 m depth off Kolbeinsey on the Jan-Mayen ridge. Incubation of high temperature fluids yielded cultures of undescribed hyperthermophilic eu- and archaebacteria, growing in a temperature range between 70° and 110°C depending on the isolates. Bacteria are closely related to species occurring within deep sea hydrothermal areas. In contrast to deep-sea vent sites of the Mid-Atlantic and other oceans, the Kolbeinsey macro- and meiofauna consists of species reported from non-vent areas in the boreal Atlantic and adjacent polar seas. The most abundant forms are a solitary hydroid polyp and two sponges. Kolbeinsey is an isolated and young area of hydrothermal activity at relatively low depth and in highly productive waters; these findings could indicate a model for an early evolutionary step towards the formation of a genuine specialized vent community.     

Nematode community composition in hydrothermal vent and adjacent non-vent fields around Myojin Knoll,a seamount on the Izu-Ogasawara Arc in the western North Pacific Ocean

In contrast to specific large benthic invertebrates in chemosynthetic ecosystems such as hydrothermal vents, meiofaunal communities in such habitats have been reported to have strong taxonomic overlap with meiofauna in the adjacent “normal” environments. However, meiofauna have only recently been included in studies of those environments and detailed information on these communities is still rare. This is especially true in the Northwest Pacific Ocean, even though there are many seamounts with active vents in the calderas of the region. Nematode community composition at the genus level in sediments from a hydrothermal vent field in the caldera of Myojin Knoll (32°06′N, 139°52′E, depth 1,300 m), a seamount on the Izu-Ogasawara Arc, Japan, was investigated for the first time and was compared with adjacent non-vent areas inside and outside the caldera. Multivariate analyses showed that the composition of nematodes in the hydrothermal field was significantly different from that in the non-hydrothermal fields around the caldera. However, the common genera, such as Oxystomina, Pareudesmoscolex, Desmoscolex, and Microlaimus were found in two, or all three vent fields while their rank contributions differed among the three fields. When the data from Myojin Knoll were compared with those from other deep-sea vent environments in different regions (e.g., North Fiji Basin, East Pacific Rise, Mid-Atlantic Ridge), the nematode composition in the vent field of the Myojin caldera was more similar to that of the non-vent fields around the caldera than the composition in vent fields of other regions. These data from the Northwest Pacific Ocean also suggest the absence of long-range transport systems and local adaptations for meiofauna in hydrothermal vent fields.     

Molecular phylogenetic analyses of shallow-water Caribbean octocorals

Octocorals, especially gorgonians, are conspicuous on Caribbean coral reefs, but there is no consensus regarding species relationships. Mitochondrial protein-coding genes [NADH-dehydrogenase subunits 2 (ND2) and 6 (ND6), and mutS homolog (msh1), 1633 bp] from 28 shallow-water species were sequenced to develop the first molecular phylogeny for Caribbean octocorals. The specimens were collected primarily in the Caribbean or off Brazil in 1999-2001. Morphological characters (sclerites and axial ultrastructure) were also examined in order to map them onto the molecular phylogeny. Analyses of both nucleotide and amino acid substitutions using maximum parsimony and likelihood (including maximum-likelihood and Bayesian analysis) generated very similar results, with most nodes having high levels of support. These molecular results were significantly different from the generally accepted classification. Neither Plexauridae nor Gorgoniidae were monophyletic. Plexaurella spp., nominal plexaurids, were basal to the gorgoniids, sharing many morphological characters with them. This corroborates previous findings using secondary metabolites and biosynthetic pathways. The sea fans, Gorgonia spp. and Pacifigorgia spp., as well as the pinnate gorgonians, Muriceopsis flavida and Pseudopterogorgia spp., did not have sea fan or pinnate relatives, suggesting there has been convergent evolution of colony form. Caribbean plexaurids appeared more derived and/or recently evolved according to both morphological and molecular data (e.g. Eunicea spp. and Plexaura spp.). Molecular phylogenetics is a promising approach for reconstructing phylogenetic relationships among octocorals as well as to understand their complex morphology. Electronic Supplementary Material is available if you access this article at http://dx.doi.org/10.1007/s00227-003-1018-7. On that page (frame on the left side), a link takes you directly to the supplementary material.     

Annual population development and production by Calanus finmarchicus, C. glacialis and C. hyperboreus in Disko Bay, western Greenland

The populations of the copepod species Calanus finmarchicus, C. glacialis and C. hyperboreus were investigated in Disko Bay during a 14-month period in 1996-1997. The three species were predominant in the copepod community. The biomass reached a maximum at the beginning of June (127 mg C m^-3). From the end of July until the end of April the following year, the biomass was <1-6 mg C m^-3. All three species showed seasonal ontogenetic migration. The spring ascent for all three species was just prior to or in association with the break-up of sea ice and the development of the spring bloom, whereas descent occurred over a larger time span during summer. The main overwintering stages were CV for C. finmarchicus, CIV and CV for C. glacialis and C. hyperboreus. Peak abundance of juvenile copepodites, representing the new generation, was in August for C. finmarchicus, in July for C. glacialis and in May/June for C. hyperboreus. From the timing of reproduction and the population development, the life cycles were deduced to be 1 year for C. finmarchicus and at least 2 years for C. glacialis and C. hyperboreus. Secondary production and potential grazing impact of the Calanus community were estimated by two methods based on specific egg-production rates and temperature-dependent production. The Calanus community was not able to control the primary producers during the spring bloom but probably did during post-bloom. The estimates also indicated that grazing on ciliates and heterotrophic dinoflagellates contributes as an essential food source in the post-bloom period.     

Ultrastructural,biochemical, and immunological characterization of two populations of the mytilid mussel <Emphasis Type="Italic">Bathymodiolus</Emphasis><Emphasis Type="Italic">azoricus</Emphasis> from the Mid-Atlantic Ridge: evidence for a dual symbiosis

A recently described species of mytilid mussel, Bathymodiolus azoricus Von Cosel et al., 1999, was observed to be the dominant organism at the hydrothermal vents off the Azores, at both the Lucky Strike and Menez Gwen sites. Evidence suggests this species of Bathymodiolus represents yet another example of the intriguing dual symbiosis known in three other species of deep-sea mytilid mussels. Transmission electron micrographs (TEM) show the majority of gill bacteriocytes in mussels sampled from both populations to contain two distinct symbiont morphotypes. One morphotype is characterized by large size (mean diameter, 1.25 µm), coccoid shape, and stacked intracytoplasmic membranes that are consistent with the morphology of type I methanotrophs. The second morphotype is smaller (mean diameter, 0.35 µm) and was observed in coccoid or rod shapes. Immunoblots revealed the presence of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) and methanol dehydrogenase (MeDH) in both populations of mussels. Activities of these enzymes, as well as sulfate adenylyl transferase (ATP sulfurylase) and adenylyl sulfate reductase (APS reductase), were detected in gill extracts. The activities measured for the two populations were highly variable, though the population sampled from Lucky Strike showed higher RubisCO activity. Stable carbon isotope values (Lucky Strike, '¹³C=-32.6ǂ.3‰; Menez Gwen, '¹³C=-22.8ǂ.4‰) are in the range of previously reported stable carbon isotope measurements for mytilid mussels hosting a dual symbiosis. Collectively, these results provide evidence for the activity of both sulfur-oxidizing and methane-oxidizing metabolic pathways in B. azoricus. Furthermore, evidence for a greater dependence on methanotrophy in the Menez Gwen mussel population is offered by analysis of cell counts from TEMs. Higher methanotroph numbers, and putatively activity, in this population of mussels are further supported by published geochemical data indicating higher methane concentrations in the vent fluids at Menez Gwen. This finding suggests that environmental conditions may regulate a balance between the physiological activities of different symbiont populations associated with these mussels. The existence of a dual symbiosis could thus confer greater environmental tolerance and increased niche space to the mytilid host in the stochastic hydrothermal vent habitat.     

Identification of archaeogastropod larvae from a hydrothermal vent community

Dispersal is essential in order that endemic species living in ephemeral, patchy vent environments may persist over evolutionary time. Quantitative field studies of larval dispersal, however, require specieslevel identification of the larval forms because each individual must be distinguished from related vent species, and from non-vent species living in the surrounding deep-sea environment. Methods for culturing these larvae to an identifiable stage have not yet been developed. To solve the larval identification problem for the archaeogastropod molluscs (a prominent component of vent communities), we used a scanning electron microscope (SEM) to image shells of larvae collected in the water column near vents along the East Pacific Rise (9°40′ to 9°50′N; 104°W). Larval shell size, shape and ornamentation were compared to protoconchs retained in juvenile or adult shells of identified species, and used to assign five larval groups unequivocally to species (Cyathermia naticoides Warén and Bouchet, 1989; Neomphalus fretterae McLean, 1981; Clypeosectus delectus McLean, 1989; Rhynchopelta concentrica McLean, 1989; and Lirapex granularis Warén and Bouchet, 1989) and seven groups tentatively to species or genus [Lepetodrilus spp. (three groups); Gorgoleptis sp; Peltospira ?operculata McLean, 1989; and ?Melanodrymia sp. (two groups)].     

Carotenoids indicate differences in diet of the hydrothermal vent crabBythograea thermydron (Brachyura)

Carotenoid pigments were used as markers to investigate the sources of energy to two deep-sea hydrothermal vent communities. Specimens of the hydrothermal-vent brachyuran crabBythograea thermydron were collected at 2 500 m depth from the Rose Garden vent site in the Galápagos Rift Valley in February, November and December 1979, and 2 600 m depth on the East Pacific Rise at 21°N in May 1982. Four carotenoids (astaxanthin, canthaxanthin, echinenone and beta-carotene) have been identified as the pigments responsible for the red color of the eggs of the crabs from the Galápagos Rift site. Consistent with the fact that animals are unable to synthesize carotenoidsde novo, precursors were not present in the crabs' tissues, affirming that these pigments are of dietary origin. The number of ovigerous female crabs and the concentrations of carotenoids in the eggs suggest a readily available source of these pigments in the Galápagos vent environment. In contrast, the developing eggs ofB. thermydron from the 21°N vent site were cream-colored, with only trace quantites of carotenoids and fewer types of carotenoids. Analysis of carotenoid distribution in both females and males in these two populations indicates a very low level of carotenoids in the diet of the 21°N vent crabs, and reflects differences in trophic interactions and primary production at the two vent sites. The few types and low concentration of carotenoids inB. thermydron indicate a diet that is different from non-vent, deep-sea crustaceans. We hypothesize that the source of carotenoids are bacteria within the vent community, and not ultimately from photosynthetic production.     

Trophic relationships of hydrothermal vent and non-vent communities in the upper sublittoral and upper bathyal zones off Kueishan Island,Taiwan: a combined morphological,gut content analysis and stable isotope approach

This study used morphological, gut content analysis and carbon- and nitrogen-stable isotope analysis to investigate the trophic structure of upper sublittoral (15–30 m deep) and upper bathyal (200–300 m deep) hydrothermal vents and the adjacent non-vent upper bathyal environment off Kueishan Island. The sublittoral vents host no chemosynthetic fauna, but green and red algae, epibiotic biofilm on crustacean surfaces, and zooplankton form the base of the trophic system. Suspension-feeding sea anemones and the generalist omnivorous vent crab Xenograpsus testudinatus occupy higher trophic levels. The upper bathyal hydrothermal vent is a chemoautotrophic-based system. The vent mussel Bathymodiolus taiwanensis forms a chemosynthetic component of this trophic system. Bacterial biofilm, surface plankton, and algae form the other dietary fractions of the upper bathyal fauna. The vent hermit crab Paragiopagurus ventilatus and the vent crab X. testudinatus are generalist omnivores. The vent-endemic tonguefish Symphurus multimaculatus occupies the top level of the trophic system. The adjacent non-vent upper bathyal region contains decapod crustaceans, which function as either predators or scavengers. The assemblages of X. testudinatus from sublittoral and upper bathyal vents exhibited distinct stable isotope values, suggesting that they feed on different food sources. The upper bathyal Xenograpsus assemblages displayed large variations in their stable isotope values and exhibited an ontogenetic shift in their δ¹³C and δ¹⁵N stable isotope signatures. Some individuals of Xenograpsus exhibited δ¹⁵N values close to those of non-vent species, suggesting that the highly mobile Xenograpsus may transfer energy between the upper bathyal hydrothermal vents and the adjacent non-vent upper bathyal environment.     

Ecotoxicological responses to chalcopyrite exposure in a proxy for deep-sea hydrothermal vent shrimp: implications for seafloor massive sulphide mining

Deep-sea mineral prospecting has raised concerns regarding potential ecotoxicological impacts of deep-sea mineral extraction. Although metal mineral phases are predicted to exhibit low bioavailability, few data explore the relative toxicity of mineral phases and dissolved constituent metals. Acute 96?h chalcopyrite (CuFeS₂) (<250?µm grain size) exposures using the shallow-water ecophysiological model organism Palaemon varians as an ecotoxicological proxy for deep-sea hydrothermal vent shrimp revealed no effect in both lethal and sublethal assays up to 2.888?g?L^?1, suggesting that chalcopyrite is not bioavailable. Deep-sea species, therefore, appear at greater ecotoxicological risk from dissolved metals during seafloor massive sulphide (SMS) mining. Consequently, an approach combining modelling the release, and spatial and temporal dilution of dissolved metals during SMS mining, with data on sublethal effects of dissolved metals on shallow-water proxies, may best constrain the potential ecotoxicological impacts of SMS mining, and deliver ecotoxicological threshold concentrations for active SMS extraction.     

Molecular taxonomy of vestimentiferans of the western Pacific,and their phylogenetic relationship to species of the eastern Pacific III. Alaysia-like vestimentiferans and relationships among families

The phylogenetic status of Alaysia-like vestimentiferans, which were collected at eight sites in the western Pacific, was analyzed on the basis of the nucleotide sequence of part of a mitochondrial gene for cytochrome oxidase I. The 123 individuals analyzed were tentatively classified into four species, which inhabit, respectively, seep areas off the central part of the Japanese mainland, hydrothermal vent fields in the Mid-Okinawa Trough, hydrothermal vent fields in the southern Okinawa Trough, and both seep and vent sites in the Bismarck Sea. From six additional lamellibrachiid specimens from two sites in the Bismarck Sea, two new tentative species were recognized, namely, one from a seep area off Papua New Guinea and another from the hydrothermal vent field at the DESMOS site in the Manus Basin. Phylogenetic analysis using all available sequences of six vestimentiferan families and Alaysia-like vestimentiferans revealed that vestimentiferans could be divided into three groups, namely, lamellibrachiids, escarpiids, and others, even though the monophyly of the third group was supported by only low bootstrap probabilities. Within the first group, the earliest divergence of a tentative lamellibrachiid species from the DESMOS site was apparent. All Alaysia-like vestimentiferans formed a monophyletic group with Arcovestia ivanovi from the Manus Basin, and it is suggested that this group might be derived from vestimentiferans that are endemic to the hydrothermal sites in the Eastern Pacific Rise.     

Chromosomal evolution in Mugilidae: karyotype characterization of Liza saliens and comparative localization of major and minor ribosomal genes in the six Mediterranean mullets

This study continues a comparative cytogenetic analysis of the fish family Mugilidae, reporting the karyotype characterization of the leaping mullet, Liza saliens, by C-banding, Ag- and fluorochrome-staining, and completing the fluorescence in situ hybridization (FISH)-mapping of the 18S and 5S rRNA genes (rDNA) to the chromosomes of the six Mediterranean mullets, namely L. saliens, L. ramada, L. aurata, Mugil cephalus, Chelon labrosus and Oedalechilus labeo. In all species, except M. cephalus, the 5S rDNA sites were localized on a medium-sized acrocentric chromosome pair, which was considered homeologous in all of them. In L. saliens, an additional 5S rDNA site was detected in a location close to the one shown by major ribosomal genes in M. cephalus, i.e. the subtelomeric region of chromosome pair 1. The 5S rDNA site in M. cephalus is located on the smallest chromosome pair of the complement, which, on the other hand, though on a different position, bears 18S rDNA in all the species of Liza and Chelon examined. The heterochromatin composition and the major and minor ribosomal gene locations suggest that the karyotype of L. saliens (subgenus Protomugil) can be considered intermediate between the karyotype of the more primitive M. cephalus and those of the other Liza (subgenus Liza) species and of the representatives of the more derived genera Chelon and Oedalechilus.     

Escape responses of copepod nauplii in the flow field of the blue mussel,<Emphasis Type="Italic"> Mytilus edulis</Emphasis>

Bivalves are important grazers on phytoplankton in shallow waters. However, very little is known about their ability to capture actively moving zooplankton. We investigated the escape response and success of early and late nauplii of three copepod species (Acartia tonsa, Temora longicornis and Eurytemora affinis) in the flow field of a blue mussel, Mytilus edulis, using both video observations and incubation experiments. An empirical model was created to describe the spatial distribution of the fluid deformation rate. Nauplii responded with escape jumps at mean fluid deformation rates of 0.6-1.9 s^у. Escape success differed between taxa. T. longicornis was the poorest escaper, while A. tonsa and E. affinis were more efficient and similar to one another. Deformation rates differed in different parts of the flow field, which resulted in differences in escape success between the sectors. Nauplii were caught most often in the sector furthest away from the exhalent siphon, where the deformation rate was the weakest. There the nauplii were unable to detect an escape signal in time to react and flee.     

Cross-shelf variation in calanoid copepod production during summer 1996 off the Oregon coast, USA

The fecundity of nine species of adult female calanoid copepods, and molting rates for copepodite stages of Calanus marshallae were measured in 24 h shipboard incubations from samples taken during the upwelling season off the Oregon coast. Hydrographic and chlorophyll measurements were made at approximately 300 stations, and living zooplankton were collected at 36 stations on the continental shelf (<150 m depth) and 37 stations offshore of the shelf (>150 m depth) for experimental work. In our experiments, maximum egg production rates (EPR) were observed only for Calanus pacificus and Pseudocalanus mimus, 65.7 and 3.9 eggs fem^-1 day^-1 respectively, about 95% of the maximum rates known from published laboratory observations. EPR of all other copepod species (e.g., C. marshallae, Acartia longiremis and Eucalanus californicus) ranged from 3% to 65% of maximum published rates. Fecundity was not significantly related to body weight or temperature, but was significantly correlated with chlorophyll a concentration for all species except Paracalanus parvus and A. longiremis. Copepod biomass and production in on-shelf waters was dominated by female P. mimus and C. marshallae, accounting for 93% of the adult biomass (3.1 mg C m^-3) and 81% of the adult production (0.19 mg C m^-3 day^-1). Biomass in the off-shelf environment was dominated by female E. californicus, P. mimus, and C. pacificus, accounting for 95% of the adult biomass (2.2 mg C m^-3) and 95% of the adult production (0.08 mg C m^-3 day^-1). Copepodite (C1-C5) production was estimated to be 2.1 mg C m^-3 day^-1 (on-shelf waters) and 1.2 mg C m^-3 day^-1 (off-shelf water). Total adult + juvenile production averaged 2.3 mg C m^-3 day^-1 (on-shelf waters) and 1.3 mg C m^-3 day^-1 (off-shelf waters). We compared our measured female weight-specific growth rates to those predicted from the empirical models of copepod growth rates of Huntley and Lopez [Am Nat (1992) 140:201-242] and Hirst and Lampitt [Mar Biol (1998) 132:247-257]. Most of our measured values were lower than those predicted from the equation of Huntley and Lopez. We found good agreement with Hirst and Lampitt for growth rates <0.10 day^-1 but found that their empirical equations underestimated growth at rates >0.10 day^-1. The mismatch with Hirst and Lampitt resulted because some of our species were growing at maximum rates whereas their composite empirical equations predict "global" averages that do not represent maximum growth rates.     

Disinfection efficacy on cyst viability of<Emphasis Type="Italic"> Artemia franciscana</Emphasis> (Crustacea),<Emphasis Type="Italic"> Hexarthra fennica</Emphasis> (Rotifera) and<Emphasis Type="Italic"> Fabrea salina</Emphasis> (Ciliophora)

Resting stages (cysts) of Artemia franciscana, Hexarthra fennica and Fabrea salina were exposed for two periods (acute and chronic exposures) to different concentrations of five aquaculture disinfectants (formalin, sodium hypochlorite, potassium permanganate, organic iodine, copper sulphate). The effects of chemical treatments were ranked according to their action on cyst hatching: total inhibition (no cyst hatching), heavy inhibition (significant decrease of cyst hatching), alteration of hatching synchrony, and occurrence of anomalous hatching (death of emerging individuals or birth of malformed organisms). Resting-stage viability was not completely impaired by disinfectant exposures at the ordinary doses used in aquaculture, so that usual treatments are possibly ineffective against the protist and metazoan cysts potentially present in breeding systems. On the other hand, the high resistance shown by cysts suggests the possibility of using these chemicals in live-feed disinfection.     

Energy budgets and feeding rates of Coryphaenoides acrolepis and C. armatus

This study develops energy budgets and estimates feeding rates for two macrourid fishes, Coryphaenoides acrolepis, dominant in the bathyal eastern North Pacific, and the abyssal cosmopolitan species, Coryphaenoides armatus. Daily energy expenditure by C. acrolepis was nearly twice that of C. armatus. C. acrolepis allocated nearly equal amounts of energy to metabolism and growth. Once sexual maturity was reached reproduction became the dominant energetic cost. Either these costs are necessary to retain adequate numbers of eggs and larvae on the continental slopes, or this fish does not reproduce on an annual basis and the calculated costs are an overestimate. C. armatus allocated relatively more energy to metabolism than growth. It may be semelparous, and this strategy would be of great energetic savings in its food-poor but stable environment. Individual daily ration for C. acrolepis decreased from 0.31% to 0.07% of body weight (BW) and for C. armatus from 0.12% to 0.02% BW with increasing fish length. These rates are substantially lower than those for fishes living in cold waters on the continental shelves. The population feeding rates for C. acrolepis ranged from 0.8 to 15 kg km^-2 day^-1 and for C. armatus from 5 to 2,800 g km^-2 day^-1. The scavenging behaviour of C. acrolepis was used to investigate the role of carrion as a food supply to the deep-sea benthos. It was estimated that the carrion eaten by C. acrolepis is equivalent to 0.04 mg C m^-2 day^-1 or only 0.2-0.4% of the average small particulate flux. Carrion consumption is important for scavengers like C. acrolepis, but it is not an important component of the carbon flux into the deep-sea benthic environment.