In situ grazing rates of deep-sea benthic boundary-layer zooplankton

In situ grazing rates of mixed assemblages of deep-sea benthic boundary-layer zooplankton were measured in July 1983 at a site in the North Atlantic Ocean at 2 175 m depth using a short-term radioisotope-uptake method. Zooplankton were collected with an opening-closing net system from the bottom 1 m of the ocean and incubated in situ with mixed tritiated amino acids in special cod-end chambers. Incubations were terminated at depth by the addition of MS-222. Radioisotope uptake beyond that of dead controls was shown by both the zooplankton and particulate fractions. Grazing rates in the deep-sea experiments were surprisingly high, being comparable to wintertime Narragansett Bay zooplankton grazing rates determined in a separate series of laboratory experiments. These laboratory experiments also documented nonparticle-associated uptake of dissolved amino acids by Narragansett Bay zooplankton, but the importance of this in the deep sea is unknown. The deep-sea benthic boundary layer may be a region of elevated rates and activity because of its higher particulate concentrations, and our experiments may also have measured maximum rather than average rates.     

Comparative study of behavioral-sensitivity thresholds to near-UV and blue-green light in deep-sea crustaceans

The behavioral sensitivities of five species of deep-sea crustaceans (order Decapoda: Acanthephyra curtirostris, A. smithi, Notostomus gibbosus, Janicella spinacauda and Oplophorus gracilirostris) to near-UV and blue-green light were studied during a research cruise off the coast of Hawaii in 1993. Two of the five species have electrophysiologically-measured spectral sensitivity peaks at 400 and 500 nm, while the remaining three species have a single sensitivity peak at 490 to 500 nm. In the current study, behavioral mean threshold sensitivities (defined as the lowest irradiance change to which the shrimp would give a behavioral response) were determined for tethered specimens of each species at two wavelengths, 400 and 500 nm. The mean behavioral threshold sensitivities of the two species with putative dual visual-pigment systems were approximately the same to near-UV and blue-green light, while the other three species were significantly less sensitive to near-UV vs blue-green light. Results from these experiments indicate that (1) behavioral information obtained from tethered shrimp accurately reflects their spectral sensitivity, and (2) the sensitivity of the putative dichromats to near-UV light is sufficiently low to detect calculated levels of near-UV light remaining in the down-welling field at their daytime depth of 600 m. Possible functions of this high sensitivity to short wavelength light are discussed.     

In situ filtering and ingestion rates of deep-sea benthic boundary-layer zooplankton in the Santa Catalina Basin

In situ rates of filtration, particulate ingestion, and carbon ingestion of deep-sea benthic boundary-layer zooplankton were determined in December 1984 in the Santa Catalina Basin, at 1 300 m depth in the California Borderland, by a short-term radioisotope-incorporation technique. Zooplankton were collected at 1 or 50 m above the bottom with an opening-closing net system on a submersible, and incubated at depth with labelled amino acids in special cod-end chambers. Concentrations of particulate material and particulate organic carbon in the ambient water were also measured. The zooplankton had a median weight-specific filtration rate of 12.4 ml (mg dr. wt)^-1 h^-1 and a median carbon ingestion rate of 5.4 g C (mg dr. wt)^-1 h^-1. Filtration rates were not significantly different from those in similar experiments in the north Atlantic at 2 175 m depth or Narragansett Bay in the winter, although the medians of the deep-sea experiments were lower than for the Bay. In the Santa Catalina Basin, rates from experiments at 1 m above the bottom in more turbid water were not significantly different from those at 50 m above the bottom in clearer water. These deep-sea benthic boundary-layer zooplankton may have the potential to respond to food pulses, and their relatively high ingestion rates suggest that they could have significant effects on particulate, chemical, and bacterial processes in the near-bottom water column.     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. IV. Patterns of aerobic metabolism in the mesopelagic deep-sea fangtooth fish Anoplogaster cornuta

Measurements have been made of oxygen consumption rates O₂ of 10 specimens of the mesopelagic deep-sea fangtooth fish Anoplogaster cornuta. Determinations were made at 1 atm pressure, at temperatures of 3°, 7°, and 10°C, at dissolved oxygen concentrations ranging from near saturation to zero, with the fish swimming at low, controlled speeds. Weight-specific O₂ were uniformly low. They showed Q₁₀'s of 2.5 and 1.3, respectively, in the temperature ranges 3° to 7°C, and 7° to 10°C, at dissolved oxygen concentrations above 2 ml (standard temperature and presusure, STP)/1. Measurable O₂ continued in these fish at dissolved oxygen concentrations down to the lowest levels detectable with our instruments. At 7°C the average critical oxygen tension (P _c ) for the entire group was near 35 mm Hg. However, there is a statistically significant positive slope to the regression line relating O₂ to P _c for individual fish. The physiological and ecological significance of these results is discussed, particularly with reference to thermal effects and to the basis for survival by A. cornuta in the oxygen minimum layers of the eastern Pacific Ocean.     

Low-temperature adaptation of deep-sea bacteria isolated from the Japan Trench

Montastraea annularis, M. faveolata, and M.␣franksi are three recently separated species that together dominate reefs of the tropical western Atlantic. Despite morphological, life-history, ecological and genetic differences, the legitimacy of their status as separate species has been questioned. This controversy stems from both the scarcity of unambiguous, diagnostic differences among them, and from the possibility of extensive hybridization associated with their approximately synchronous reproduction in sympatry. Here we report on fertilization trials and the timing of spawning, both of which suggest that the potential for hybridization may be limited. Crosses between M. faveolata (the most genetically distinctive taxon) and the other two species were largely unsuccessful, as were selfed matings for all three species. M. annularis and M. franksi showed no evidence of fertilization barriers, but the timing of spawning typically differed between them by 1 to 2 h. We also found that spawning times in the field of M. annularis and M. faveolata were non-overlapping in 1995, and that the timing of spawning in M. annularis could be experimentally shifted forward by simulating earlier than natural sunsets. These findings from Panamá and Honduras, particularly given their consistency with comparable observations and experiments elsewhere, provide evidence of reproductive isolation and support the separate species status of these three taxa. Some hybridization may occur under natural conditions at these sites, particularly between M. annularis and M.␣franksi. Rampant genetic interchange among these taxa in Central America seems unlikely, however, in the light of the concordant associations between morphology, reproductive biology and other characters which are observed. Received: 22 July 1996 / Accepted: 2 October 1996     

Trophic structure of deep-sea macrobenthos

The effect of the trophic factor on large-scale distributional patterns of deep-sea macrobenthos inhabiting the floor of the World Ocean has been studied. Two hundred and twenty-eight bottom trawl samples collected by Soviet research vessels in the Pacific and Indian Oceans at depths ranging from 3000 to 6000 m were analyzed. For each sample, the weight of animals with a similar mode of feeding was determined to find the weight ratio of representatives of three main trophic groups, i.e., deposit-feeders, suspension-feeders and carnivores. These data, indicating predominance of alternate groups as well as data on their geographic distribution, were related to feeding conditions which depend on: (1) rates of sedimentation, (2) nature of sediments, (3) content of organic carbon, (4) degree of transformation of organic matter on and within sediments, and, when available, (5) data on redox potential, biochemical oxygen consumption, and state of heterotrophic microflora in the sediments. In dealing with the feeding conditions of deep-sea macrobenthos in the Atlantic Ocean, biological characteristics were deduced from literature data on the composition of sediments, their redox potential and organic carbon content. As a result of this research, eutrophic and oligotrophic regions on the floor of the World Ocean have been distinguished and their boundaries defined. Eutrophic regions lie within areas with high biological productivity of surface-water layers, and cover the peripheral and equatorial parts of the oceans; they are characterized by quantities of labile (digestible) organic matter within sediments which are sufficient for deposit-feeders to predominate in eutrophic regions everywhere, except on considerable bottom elevations. Oligotrophic regions are confined to open areas of the oceans lying beyond the equatorial belt; they are characterized by very low rates of sedimentation and, consequently, by scarce quantities of deposited organic matter. Here, suspension-feeders predominate, although their population density is very low.     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. I. White-muscle metabolism in shallow-water fishes

Maximal rates of oxygen consumption in vitro have been measured under standardized conditions at three test temperatures (5°, 15°, and 25°C) on minced preparations of white muscle from 39 species of shallow-water marine teleost fishes. These fishes came from four different geographic areas, two with cool average water-temperatures (near 15°C: coastal southern California, Galápagos Islands) and two with warm average water-temperatures (near 25°C: Hawaiian Islands; Bermuda). The group includes species covering much of the range of variation to be found among the teleosts with respect to five additional variables: phylogenetic position, type of environment, body weight, activity level, and growth stage. The purpose of the work is to provide part of a base line of tissue-metabolism data on shallow-water fishes for comparison with similar results from deep-sea species. Major conclusions from statistical analyses of the results are: four groups of shapes of oxygen-uptake rate versus temperature curves exist: normal, flat, dipped and peaked. Over 50% of curves are normal. Intra-group differences, contributing significantly to the total variance of the results at given test temperatures, are: cool versus warm average environmental temperatures primarily for epipelagic species; epipelagic versus non-epipelagic environments; very active species versus all others; juvenile stages versus adults. In each case, the subgroup first mentioned shows higher muscle oxygen-uptake rates than the other subgroup. Variables not contributing significantly to the total variance are phylogenetic position and body weight. Physiological and ecological implications of these results are discussed.     

Temporal resolution in the eyes of marine decapods from coastal and deep-sea habitats

 Temporal responses of eyes from four decapod species taken from sublittoral (Pandalus montagui Leach), coastal [Nephrops norvegicus (L.)] and deep-sea [Paromola cuvieri (Risso) and Chaceon (=Geryon) affinis A. Milne Edwards and Bouvier] habitats were examined. The electroretinogram responses to a range of sinusoidal intensity modulations between 0.5 and 40 Hz were recorded. Recordings were made from individuals adapted successively to two background light intensities. The sublittoral and coastal species showed faster responses when adapted to the higher light level and they also responded best to intermediate frequencies. When adapted to the lower light level, all species responded most strongly to low-frequency stimuli. Physiological and ecological reasons for the differences in responses are suggested. Received: 2 July 1999 / Accepted: 26 October 1999     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. II. Red-muscle metabolism in shallow-water fishes

Maximal rates of oxygen consumption in vitro have been measured under standardized conditions at three test temperatures (5°, 15°, 25°C) on minced preparations of red muscle from 10 species of shallow-water marine teleost fishes. These fishes came from three different geographic areas, two with cool average water temperatures (near 15°C: coastal southern California, Galápagos Islands) and one with warm average water temperatures (near 25°C: Hawaiian Islands). The group is made up of post-juvenile or adult epipelagic fishes, which are moderately or very active in terms of their locomotor activities. A large part of the range of phylogenetic diversity among the teleosts is represented, as is the body weight range from a few grams to several kilograms. The purpose of the work is to provide part of a set of tissue-metabolism data on shallow-water fishes for future comparison with similar results from deep-sea species. Of 8 complete curves for oxygen uptake rate versus temperature (R-T curves), 6 are normal in shape (Q₁₀1.5), 1 is normal but with a low Q₁₀, and 1 is partly flat, partly normal. The differences between the species in terms of both absolute positions and slopes of the R-T curves are not related in any consistent way to any of the three testable variables: phylogenetic position, long-term adaptation temperature, and body size. The red muscles of a variety of adult epipelagic fishes, at ecologically realistic temperatures, are shown to be exceptions to the general rule that tissues of ectothermous lower vertebrates have lower metabolic rates than comparable tissues of non-torpid endothermous higher vertebrates. This circumstance probably is a major factor in the great capacities for sustained high-speed swimming shown by most epipelagic fishes. Other physiological and ecological implications of the results are discussed.     

深海热液喷口周围微氧耐压细菌的培养研究

研究采用析因实验设计,探讨了培养基的水源、培养温度和生长pH等因素对喷口细菌生长繁殖的影响,初步探索了常压下东太平洋某海底喷口周围微氧耐压细菌的生长条件。样品培养10d后,对培养液中细菌量进行显微计数,实验数据用SPSS11.0统计软件中的方差分析程序进行处理。统计结果显示:在标准大气压下,从研究样品中获得最多细菌数的较优培养条件为:培养基水源为单蒸水;生长pH为7.60;培养温度为50℃。在该条件的培养液中细菌平均浓度达2.596×10个/mL。研究结果为进一步认识、鉴定与开发利用深海喷口周围细菌资源打下了基础。     

Photosynthetic characteristics of marine phytoplankton from contrasting physical environments

Two suites of phytoplankton samples have been collected in consecutive years at various times over a day from selected depths within vertically mixed and stratified water columns in the western Irish Sea, in order to provide a range of possible light histories within the populations collected. Values for the maximum rate of ¹⁴C retention (P _max) and the initial slope of the ¹⁴C retention: light intensity curve () were obtained. Supra-thermocline samples from the stratified water exhibited higher P _max values than corresponding subthermocline samples. Higher values of were also generally associated with samples from the supra-thermocline zone of the stratified region. Differences in the depth distribution of P _max and in the mixed water were small, except in the presence of a shallow thermocline. In one suite of samples from the stratified water, a diurnal increase in the P _max values of the supra-thermocline samples was observed. P _max values obtained from the samples from the mixed water were interpreted in relation to the distribution obtained from the samples from the stratified zone. Data from both the contrasting sites visited for one sample suite demonstrated a two-phase relationship between the chlorophyll a concentration and both P _max and . The rates of ¹⁴C retention of the first suite of samples were estimated by two techniques. The average differences in the retention were greater in samples from the sub-as opposed to suprathermocline zone. No trends were apparent in the smaples from the mixed waters.     

Larval dispersal of a deep-sea hydrothermal vent bivalve from the Galápagos Rift

The prodissoconch morphology of an unclassified mytilid from a hydrothermal vent on the Galápagos Rift indicates the presence of a planktotrophic larval stage with longrange dispersal capabilities. Recorded abyssal currents are probably sufficient to transport such larvae hundreds of kilometers. It is suggested that one or more aspects of the unusual biological or physico-chemical conditions (such as high microbial densities, elevated water temperatures, and hydrogen sulfide concentrations) encountered at vents, provide a stimulus to larval settlement. Such a behavioral response, perhaps coupled with a gregarious settling response, would provide a means of concentrating relatively sedentary organisms in and around these restricted, geographically isolated regions.     

Retention of particulate adenosine triphosphate from Mediterranean deep-sea water by glass-fibre and membrane filters

When deep-water samples from the Mediterranean Sea were passed through glass-fibre filters (Whatman GF/F), the adenosine nucleotide concentration of the particulate material was exceptionally low. The concentration was higher when the particulate material was concentrated on SM cellulose-membrane filters with porosities of less than 1 μm. There would seem to be two reasons for this: (1) inhibition of the bioluminescent reaction; (2) an apparently lower retention of ATP by the glass-fibre filters. In order to compare results obtained with the two different types of filters, a correction factor of two can be used if measurements are made with an internal standard. This constant factor can only be applied to samples from depths greater than 300 m.     

Evolution of habitat use by deep-sea mussels

Previous phylogenetic studies proposed that symbiont-bearing mussels of the subfamily Bathymodiolinae (Bivalvia: Mytilidae) invaded progressively deeper marine environments and evolved from lineages that decomposed wood and bone to specialized lineages that invaded cold-water hydrocarbon seeps and finally deep-sea hydrothermal vents. To assess the validity of the hypotheses, we examined two nuclear (18S and 28S rRNA) and two mitochondrial genes (COI and ND4) from a broad array of bathymodiolin species that included several recently discovered species from shallow hydrothermal seamounts. Bayesian phylogenetic analysis and maximum-likelihood estimates of ancestral character states revealed that vent species evolved multiple times, and that reversals in vent and seep habitat use occurred within the sampled taxa. Previous hypotheses regarding evolution from wood/bone-to-seeps/vents are supported in that mid-ocean hydrothermal vent species may represent a monophyletic group with one noticeable reversal. Earlier hypotheses about progressive evolution from shallow-to-deep habitats appear to hold with a few instances of habitat reversals.     

Bioluminescent responses of the deep-sea scyphozoanAtolla wyvillei

The bioluminescent responses of specimens of the deep-sea scyphozoanAtolla wyvillei, collected in the North East Atlantic and Southern Oceans between 1978 and 1984, were investigated. They include propagated waves of light travelling around both the coronal groove and/or various sites on the umbrella margin. The responses are non-polarised, there may be multiple waves resulting from a single stimulus, and propagation velocities range from 70 to 490 mm s^–1. Isolated luminous areas at the tentacle base do not produce multiple responses, but show summation of flashes at stimulus frequencies >2 s^–1 and facilitation is at least partly produced by local recruitment of additional luminous sources. Propagated luminous responses have also been observed in the neritic scyphozoanPelagia noctiluca. Damage during capture and handling probably limits the responses obtainable in the laboratory.     

Reproductive strategies of two deep-sea gastropod species from the Porcupine Seabight (Northeast Atlantic)

Two species of small gastropods (<6 mm in length), Amphissa acutecostata (Philippi, 1844) and Gymnobela subaraneosa (Dautzenberg and Fischer, 1896), widely distributed in the northeast Atlantic, were found in large numbers in the Porcupine Seabight (Northeast Atlantic). Except for some aspects of taxonomy and distribution, as well as some data on larval development, the biology of these species is unknown. This study describes basic aspects of the life-history strategies of both species. Histological studies showed that oocyte and sperm development in both species was similar to the gametogenetic patterns observed in other deep-sea gastropods. In females, oogonia proliferated in the germinal epithelium and developed into previtellogenic oocytes (30–40 m), which grew into vitellogenic primary oocytes. Vitellogenic oocytes were covered by a thin layer of follicle cells involved in the vitellogenic processes. The maximum size for mature oocytes was 99.06 m for A. acutecostata and 114.82 m for G. subaraneosa. In A. acutecostata most of the volume of the ovary was occupied by previtellogenic and early vitellogenic oocytes, whereas in G. subaraneosa most of the volume was filled by large vitellogenic oocytes. Both species showed quasi-continuous production of oocytes. The oocyte size-frequency diagrams suggested a continuous release of a small number of oocytes throughout the year for A. acutecostata, and asynchronous periodic spawning events for G. subaraneosa. Gonad development and gametogenesis could be strongly affected by presence of parasites in one of the populations of G. subaraneosa.Communicated by J.P. Thorpe, Port Erin     

Effect of molecular properties on the photocatalytic degradation rates of dichlorophenols and dichloroanilines in aqueous TiO2 suspensions

The kinetics of the photocatalytic degradation of 10 different dichlorophenols and dichloroanilines have been investigated experimentally and theoretically. With the intention of finding certain molecular indices in order to determine the degradation rates of aromatic pollutants, geometry optimizations of the compounds have been performed with the semiempirical PM3 method. The molecular orbital calculations have been carried out by an SCF method using the RHF formalism. The correlations between the apparent first-order rate constants and the calculated molecular properties of the compounds have been examined. Four different structure–activity relationships have been developed expressing the logarithms of the rate constants in terms of the Hammett constants, electron densities of the substituents, the coefficients and the energies of the highest occupied molecular orbitals HOMO, and 1-octanol/water partition coefficients log?K _OW.     

On the place of origin of deep-sea lsopods

Biogeographic and phylogenetic data on the deep-sea isopod family Ilyarachnidae (Paraselloidea) document its origin and evolutionary radiation in the deep sea. The distribution of eyes among paraselloidean families suggests an in situ evolution for all those families which have primarily deep-sea distributions. Present-day distributions of paraselloidean isopods provide no hints to their ultimate sources in shallow water. These findings contrast to recent suggestions in the literature that the deep-sea isopod fauna has been derived from shallow Antarctic waters.