Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. I, Horizontal and vertical distributions

Originally published in the Journal of marine research, v. 36, 1, 1978, pp. 119-142The hydrographic limit of the distribution of Nematoscelis megalops in the Northwestern Atlantic Ocean is usually marked by the abrupt changes in water properties across the Gulf Stream. There are, however, isolated but repeated occurrences of this species in the Sargasso Sea. In our study, individuals in the Sargasso Sea were expatriates from the Slope Water which had been transported to the collection site by Gulf Stream cold core rings with but two exceptions. The exceptional cases can be indirectly linked to the presence of rings. Expatriated populations do not persist. Extinction in a ring appears to take place in one or two generations, and for N. megalops it is related to changes in hydrographic properties, and in particular, the vertical temperature structure. Both in the Slope Water and in the ring 50% or more of the population is found in a restricted temperature regime centered about 10°C. As a ring ages, the preferred temperature regime and N. megalops along with it move deeper into the water column. The physiological and biochemical data given by Boyd, Wiebe and Cox (1978) combined with data given here indicate that withdrawal from the surface results in progressive deterioration of the nutritional condition of the population, a cessation of growth, a drastic reduction in the number of males relative to females, reproductive incapacitation, and ultimate extinction. It is conceivable that a process similar to that occurring in rings is responsible for the maintenance of the Gulf Stream as a hydrographic limit in the distribution of N. megalops.Prepared for the Office of Naval Research under Contracts N00014-66-C-0241; NR 083-004 and N00014-74-C-0262; NR 083-004 and for the National Science Foundation under Grant DES 74-02783 A0

Euphausiid distribution, abundance and succession in North Atlantic warm-core ring 82B

Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Plankton Research 27 (2005): 175-188, doi:10.1093/plankt/fbh170.Zooplankton collections were made with a Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) both day and night in warm-core ring 82B in the North Atlantic Ocean and at night in the Slope Water between March and August 1982. Species succession of euphausiids in 82B was presented during the lifespan of this warm-core ring, aiming at providing basic information on possible response of North Atlantic marine ecosystem to global warming. Species succession of euphausiids (32 species) in this long-lived warm-core ring was investigated. Major physical changes of 82B occurred in March-April by convective mixing and thermostad cooling, in April/May by stratification of the surface waters, and in August by the interaction with Gulf Stream. Substantial changes in species composition were observed that corresponded to these physical changes. Four different patterns were found in temporal change in abundance of warm-water species. There were species that decreased in number from March to August, species that decreased from March to June, but increased in August, species that increased from Match to August, and species that showed no systematic trend. These differences may be attributable to a species tolerance to the thermostad temperature decrease and their vertical distribution. There was also a large change from April to June with ascendance of the transition species, Thysanoessa gregaria. Cold-water species had variable patterns of abundance in 82B and occurred more abundantly in the Slope Water than in the ring. The monthly percentage decrease in the abundance of warm-water species in 82B was high compared with that of cold-water species in cold-core rings as a result of the more rapid changes in the physical structure and the shorter lifetimes of warm-core rings in the Western North Atlantic.This work was partially supported by grants from The Sumitomo Foundation and from The Asahi Glass Foundation given to Y.E. and by grants from the National Science Foundation (OCE8012748, OCE8508350, and OCE879962) to P.H.W. for collection of the samples and from the WHOI Adams Chair and NOAA Grant NA17RJ1223 for support during the manuscript preparation

Temporal changes in euphausiid distribution and abundance in North Atlantic cold-core rings in relation to the surrounding waters

Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 54 (2007): 181-202, doi:10.1016/j.dsr.2006.10.008.The species composition of euphausiids was investigated in relationship to the hydrographic conditions in the North Atlantic cold-core rings (CCR) and adjacent waters to elucidate species succession in evolving water masses. Using data, dating back to the 1970’s, from as many CCRs as possible and selecting typical cases where no major physical perturbations occurred, a general pattern of euphausiid succession and change in vertical distribution in rings with time was obtained. This pattern was related to the general distribution of euphausiids in the northwestern North Atlantic Ocean, aiming at providing basic information on probable response of North Atlantic marine ecosystem to global warming. Of the 34 euphausiid species identified, 5 were cold-water species, 17 were warm-water species, 6 were wide-ranging warm-water species, 1 was transitional, 4 were cosmopolitan and the remaining was Thysanoessa parva. Among cold-water species, Euphausia krohni and Nematoscelis megalops were dominant in CCRs. E. krohni became rare in rings older than 6 months, whereas N. megalops survived longer, being abundant in some rings of 9 months or older, by staying within its preferred temperature range as the CCR elevated isotherms sank to depths where they are normally found in the Sargasso Sea and because it is an omnivore-carnivore. Among warm-water species, epipelagic species appeared first in rings, corresponding to the physical change occurring most rapidly in the surface layers. Mesopelagic species appeared later. Cold-water species made up 65-85% of the total euphausiid population in number in younger rings (1-5 months old), while warm-water species contributed only 2-7%. Wide-ranging warm-water species made up about up to one fourth of the total in rings 5 and 7 months old. Warm-water species, mainly E. brevis, increased in older rings (9 months old or older) and made up 50% of the total in the oldest ring. The contribution of cold-water species decreased to 14% in older rings. T. parva made up 26-38% of the total in rings 6 months or older. CCR populations can be characterized by high species number, but intermediate evenness between the Slope Water and northern Sargasso Sea. In CCRs, only a limited number of species were dominant even if there were more species present in rings as old as 9-12 months than in the northern Sargasso Sea. In rings older than 9 months, euphausiids showed two peaks in their vertical distribution: a shallow daytime peak at about 400 m and a nighttime peak in the upper 100 m consisting of warm-water species (mainly E. brevis) and a deeper persistent peak at 800 m or deeper consisting of the species N. megalops and T. parva. This shallow peak in CCRs is shallower than that in the surrounding northern Sargasso Sea, and the deep peak is rarely observed in these waters.This work was partially supported by a grant from The Asahi Glass Foundation given to Y.E. and by grants from the National Science Foundation (OCE8012748, OCE8508350, and OCE879962) to P.H.W. for collection of the samples and from the WHOI Adams Chair and NOAA Grant NA17RJ1223 for support during the manuscript preparation

Accounting for biological and physical sources of acoustic backscatter improves estimates of zooplankton biomass

Author Posting. © NRC Canada, 2008. This is the author's version of the work. It is posted here by permission of NRC Canada for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 65 (2008): 1321-1333, doi:10.1139/F08-047.In order to convert measurements of backscattered acoustic energy to estimates of abundance and taxonomic information about the zooplankton community, all of the scattering processes in the water column need to be identified and their scattering contributions quantified. Zooplankton populations in the eastern edge of Wilkinson Basin in the Gulf of Maine in the Northwest Atlantic were surveyed in October 1997. Net tow samples at different depths, temperature and salinity profiles, and multiple frequency acoustic backscatter measurements from the upper 200 meters of the water column were collected. Zooplankton samples were identified, enumerated, and measured. Temperature and salinity profiles were used to estimate the amount of turbulent microstructure in the water column. These data sets were used with theoretical acoustic scattering models to calculate the contributions of both biological and physical scatterers to the overall measured scattering level. The output of these predictions shows that the dominant source of acoustic backscatter varies with depth and acoustic frequency in this region. By quantifying the contributions from multiple scattering sources, acoustic backscatter becomes a better measure of net-collected zooplankton biomass.This work was supported by the Office of Naval 540 Research (Grants #N00014-00-1-0052 and N00014-01-1-0166)

Bringing dark data into the light : a case study of the recovery of Northwestern Atlantic zooplankton data collected in the 1970s and 1980s

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in GeoResJ 6 (2015): 195-201, doi:10.1016/j.grj.2015.03.001.Data generated as a result of publicly funded research in the USA and other countries are now required to be available in public data repositories. However, many scientific data over the past 50+ years were collected at a time when the technology for curation, storage, and dissemination were primitive or non-existent and consequently many of these datasets are not available publicly. These so-called “dark data” sets are essential to the understanding of how the ocean has changed chemically and biologically in response to the documented shifts in temperature and salinity (aka climate change). An effort is underway to bring into the light, dark data about zooplankton collected in the 1970s and 1980s as part of the cold-core and warm-core rings multidisciplinary programs and other related projects. Zooplankton biomass and euphausiid species abundance from 306 tows and related environmental data including many depth specific tows taken on 34 research cruises in the Northwest Atlantic are online and accessible from the Biological and Chemical Oceanography Data Management Office (BCO-DMO).This is a contribution from the Biological and Chemical Oceanography Data Management office (BCO-DMO) that is funded by the United States National Science Foundation Grants OCE-1031253 and OCE-1435578

A bibliography of physical, chemical, and biological studies of rings in the world's oceans

This bibliography marks the end of several years of sporadic attempts to put together a set of references on rings. The scope of the effort encompasses the chemistry, biology, and physics of the long-lived, coherent features which are commonly referred to as rings after Fuglister (1972). There is a vast literature on the mesoscale eddy field in different parts of the world. The present set of references includes a subset of this body of work. The basic criterion used in the compilation of this bibliography is fairly narrow compared to the range of eddies found in the world's oceans. The emphasis here is on the highly nonlinear features formed due to the instability processes in boundary currents and in the planetary scale jet which surrounds the Antarctic. The nomenclature "ring", refers to the strong encircling current which forms a kinematic trap in which the core of the ring is embedded

Wavelet analysis of atmospheric turbulence over a coral reef flat

The world’s tropical coral reefs are at risk of severe bleaching episodes and species decline in response to global climate variability. The ecological and economic value of reef ecosystems is enormous, yet very little is known of the physical interactions that take place at the coral–ocean–atmosphere interfaces. This paper introduces and validates a novel technique for the acquisition of surface energy balance measurements over Heron Reef, part of the Capricorn Bunker Group of the southern Great Barrier Reef, Australia. Measurements of surface energy and radiation exchanges were made using a Campbell Scientific eddy covariance (EC) measurement system mounted on a floating pontoon anchored to the reef flat. A Nortek Vector velocimeter was positioned next to the pontoon to record wave motion. Wavelet analysis techniques were used to decompose the turbulent exchange of sensible heat measured by the EC unit and to compare vertical velocity measurements with wave-induced motion recorded by the velocimeter. The results indicate that although the EC system and the velocimeter share intermittent periods of high common power in their respective wavelet variance spectra, these regions are not coherent and differ in strength by more than an order of magnitude. It was concluded that over a standard averaging period of 30 min the wave-induced motion of the pontoon would not significantly interfere with the acquisition and calculation of turbulent fluxes of sensible and latent heat, thereby confirming the robustness of this method of obtaining surface energy balance measurements over coral reefs

CB17: Inferring the dynamical history of a prestellar core with chemo-dynamical models

We present a detailed theoretical study of the isolated Bok globule CB17 (L1389) based on spectral maps of CS, HCO$^+$, C$^{18}$O, C$^{34}$S, and H$^{13}$CO$^+$ lines. A phenomenological model of prestellar core evolution, a time-dependent chemical model, and a radiative transfer simulation for molecular lines are combined to reconstruct the chemical and kinematical structure of this core. We developed a general criterion that allows to quantify the difference between observed and simulated spectral maps. By minimizing this difference, we find that very high and very low values of the effective sticking probability $S$ are not appropriate for the studied prestellar core. The most probable $S$ value for CB17 is 0.3--0.5. The spatial distribution of the intensities and self-absorption features of optically thick lines is indicative of UV irradiation of the core. By fitting simultaneously optically thin and optically thick transitions, we isolate the model that reproduces all the available spectral maps to a reasonable accuracy. The line asymmetry pattern in CB17 is reproduced by a combination of infall, rotation, and turbulent motions with velocities $\sim0.05$ km s$^{-1}$, $\sim0.1$ km s$^{-1}$, and $\sim0.1$ km s$^{-1}$, respectively. These parameters corresponds to energy ratios $E_{\rm rot}/E_{\rm grav}\approx0.03$, $E_{\rm therm}/E_{\rm grav}\approx0.8$, and $E_{\rm turb}/E_{\rm grav}\approx0.05$ (the rotation parameters are determined for $i=90^\circ$). The chemical age of the core is about 2 Myrs. In particular, this is indicated by the central depletion of CO, CS, and HCO$^+$. Based on the angular momentum value, we argue that the core is going to fragment, i.e., to form a binary (multiple) star. (abridged)Comment: ApJ, in pres

Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. II, Physiological and biochemical effects of expatriation

Originally published in the Journal of Marine Research, v. 36, 1, 1978, pp. 143-159Nematoscelis megalops, a cold water euphausiid commonly found in Northwestern Atlantic Slope Water, is frequently transported in the cores of Gulf Stream cyclonic rings into the Sargasso Sea. The inner core made of cold Slope Water gradually assumes physical and biological characteristics of the surrounding Sargasso Sea. These changes gradually lead to a localized extinction of this species in the core of the ring. Samples of N. megalops taken from the same ring at 6 and 9 months after its formation show a weakened physiological and biochemical condition. Deterioration of ring individuals is evidenced by an increase in body water content and a reduction in total body lipid, carbon, respiration rates, and nitrogen relative to Slope Water individuals. By 6 months it appears that ring N. megalops must supplement food intake by metabolizing some of their body protein and by 9 months they appear to use lipids as well. A shipboard starvation experiment involving 40 Slope Water individuals showed that physiological and biochemical states similar to those found in individuals from the 9 months old ring could be duplicated in 4 days of complete starvation.Prepared for the Office of Naval Research under Contracts N00014-66-C-0241; NR 083-004 and N00014-?4-C-0262; NR 083-004 and for the National Science Foundation under Grant DES ?4-02?83 A01

Particulate matter sinking to the deep-sea floor at 2000 M in the Tongue of the Ocean, Bahamas, with a description of a new sedimentation trap

Originally published in Journal of Marine Research 34 (1976): 341-354A sedimentation trap for use just above the deep-sea floor was free-fallen to a depth of 2050 m in the Tongue of the Ocean canyon on January 3, 1974. On March 6, it was successfully recovered with the assistance of D.S.R.V. Alvin. The trap has a base 1 m square and a height of 30 cm. At the trap bottom are filters to retain falling particles. Two spring-powered sliding doors, each 1 m x 0.5 m, are used to close off the lower 2 cm of the trap during ascent to prevent disturbance of the particles collected on the filters. Total carbon on the filters as determined by high temperature combustion averaged 2301 mgC/m2 or an average on a daily basis of 36.5 mgC/m2. Similar filter aliquots were treated with cold phosphoric acid to eliminate the inorganic fraction. The resulting carbon values (X =: 5.7 mgC/m2/day) suggest 14% of the total carbon reaching the sea floor at 2000 m in this area is organic in origin. Fecal material is one readily identifiable component of the material contributing to the organic fraction. Counts of fecal pellets resulted in an estimate of an average of ~650 pellets/m2/day. Average pellet length was 241 μm and diameter was 109 μm. In laboratory experiments the pellets sank at rates varying from 50 m/day to 941 m/day (X at 5°C =159 m/day). Comparison of the sedimentation trap estimates of organic carbon input to the sea floor in this area with benthic energy requirements indicates that rapidly sinking small particulate matter could supply approximately 14% of the metabolic requirements of the benthos.Prepared for the Office of Naval Research under Contract N00014-66-C-0241; NR 083-004 and the Atlantic Foundation