Showing papers on "Pelagic zone published in 1981"

Remineralization and Nutrient Cycling in Coastal Marine Ecosystems

Abstract: Our views of remineralization and nutrient cycling in coastal marine ecosystems have changed considerably over the last 30 years. The major trend has been an increasing appreciation for the complexity of processes involved, including some marked changes in our assessment of the importance of bacteria with respect to smaller animals and in our perception of the association between bacteria and particulate matter in the sea. Among the more recent developments in this area is a growing awareness of the importance of the coupling between benthic and pelagic communities in coastal waters. There appears to be a strong linear correlation between the organic matter produced in the overlying water and the amount of organic matter consumed on the bottom in almost all of the coastal environments for which annual data are available. The large amount of organic matter consumed by the benthos (perhaps 25–50 percent of that produced) is associated with a large flux of inorganic nutrients from the sediments to the overlying water. The stoichiometry of net benthic nutrient regeneration differs from that of pelagic regeneration, however, and simple Redfield type models probably cannot be applied. The amount of fixed inorganic nitrogen returned to the water across the sediment-water interface appears to be about half of that expected on the basis of the flux of phosphorus. This behavior, along with the fact that an appreciable amount of organic matter in coastal waters gets remineralized on the bottom, contributes to the low N/P ratio that is characteristic of these areas and may be responsible for the observation that nitrogen is commonly the nutrient most limiting for primary production. Recent direct measurements of the flux of dissolved N2 across the sediment-water interface indicate that denitrification is probably responsible for the loss of fixed nitrogen during decomposition in the sediments. If this is a widespread phenomenon, estuaries, bays, and other coastal waters may be major sinks in the marine nitrogen cycle and important terms in the global nitrogen budget. However, the fact that eutrophication appears to be an increasing problem in many estuaries is dramatic warning that anthropogenic nutrient inputs can overwhelm the recycling and remineralization processes in coastal waters.

Daily patterns in the activities of swordfish, Xiphias gladius, observed by acoustic telemetry

Abstract: Horizontal and vertical movements of swordfish were studied using acoustic telemetry. Five swordfish in the Pacific and one in the Atlantic were tagged with transmitters which provided information on location. depth. and surrounding water temperature. Two of the Pacific fish showed a clear daily cycle of movement between an inshore bank during the day and deep water offshore at night. All of the swordfish responded to light, swimming deep during the day and coming near the surface at night. In the Pacific depth during daylight appeared to be limited to about 100 m by the oxygen-minimum layer, but in well-oxygenated waters of the Atlantic, a midday depth of greater than 600 m was recorded and tbe fish appeared to follow an isolume. Depth of the Atlantic fish in daylight was related to changes in ligbt caused by variation in water transparency. The vertical movements were associated with temperature changes ofas much as 19" C within 2 hours. The implications of rapid vertical movements on buoyancy and swim bladder volume are discussed. Despite their high commercial value and their significance as one of the large predators of the open ocean, relatively little is known about the habits and behavior of the swordfish, Xiphias gladius. The information which is available comes chiefly from observations made at the sea surface by commercial fishermen and from a few scientific studies based on commercial captures. Swordfish are large, fast-swimming fish that offer little opportunity for direct observation; however, some aspects of their behavior can be readily examined by telemetry from attached sensors. X iphias gladius is found throughout tropical and temperate waters. Its appearance in higher latitudes usually occurs in warm-season aggre­ gations along the edge ofthe continental shelf and on offshore banks

The phytoplankton and protozooplankton of the euphotic zone of Lake Tanganyika: Species composition, biomass, chlorophyll content, and spatio‐temporal distribution1

Abstract: The seasonal cycle of phytoplankton and protozooplankton 1 iomass observed at two widely separated pelagic stations in the euphotic zone of Lake Tanganyika from February through November 1975 could be divided into three phases, based oil algal abundance and species succession and coinciding with three phases of annual thermal stratification. Phytoplankton biomass was minimal (as low as 60 mg*m-“) during the phase of stable stratification and maximal, as high as 930 mg* me 3, at the end of the period of deep mixing. Diatoms, especially Nitzschin spp., were abundant only during the period of mixing, while filamentous blucgreens, principally Anahaena sp., were prominent during a p :riod of rapid surface warming which produced shallow mixed layers following the period o - deepest mixing. The biomass of Stromhidizcm cf. virile nearly equaled or exceeded the >hytoplankton biomass during much of the stably stratified period; this protozoan probably h: s a symbiotic relationship with zoochlorellae, which were always present in it. Lake Tanganyika showed a greater relative annual range bei wecn maximum and minimum phytoplankton and chlorophyll a concentrations than other tropical lakes and the temperate Great Lakes. Chlorophyll a ral.nged from 0.1 to 4.5 mg* np3 in he ellphotic zone and frorn 0.2 to 20.4 in surface waters; phytoplankton biomass ranged frctm 25 to 1,570 rng.n+ in the cuphotic zone. Annllal mean concentrations were among the Lowest known, 140 mg.rnm3 for phytoplankton biomass and 1.2 rng. mm3 for chlorophyll cc. Explanations for both the low annual means and the high annual variabilities may lie in ‘he lake’s steep morphometry, which affects nutrient regeneration, and in high loss rates kyrhich cause high algal growth rates but low algal biomass much of the year.

Dispersal of tropical marine fauna to the Great Australian Bight by the Leeuwin Current

Abstract: A tropical element in the demersal and pelagic fauna of the Great Australian Bight has been observed. The fauna includes benthic invertebrates, such as the basket star, Euryale aspera (Lamark), and the holothurians Pentacta anceps (Selenka) and Pentacta quadranguiaris (Lesson), and tropical pelagic tuna, such as the oriental bonito, Sarda orientalis (Temminck and Schlegal). It is suggested that the Leeuwin Current, which flows southward to Cape Leeuwin and then eastward, is responsible for the existence of tropical fauna in the Bight. The low salinity waters of the Leeuwin Current were observed for the first time to round Cape Leeuwin.

Feeding Ecology of Marine Cormorants in Southwestern North America

Abstract: -The diets of Pelagic, Brandt's and Double-crested cormorants (Phalacrocorax pelagicus, P. penicillatus and P. auritus) were compared. Data were based on 1,695 pellets and 71 chick regurgitations analyzed by us and information on 34 stomach samples published in the literature. A total of 19 sites between Kodiak, Alaska and central Mexico is represented. The three cormorants often fed in the same areas at the same time using the same technique. They exploited different microhabitats as defined by prey behavior; the prey species overlapped substantially between Brandt's and Pelagic cormorants, but those of the Double-crested Cormorant were quite different. Double-crested Cormorants fed on schooling fish usually occurring well above flat bottoms; Pelagic Cormorants fed on solitary prey on or concealed in rocky substrates; and Brandt's Cormorants fed on prey on or just above the bottom in rocky areas and in areas of flat sand or mud. The latter species fed over flat bottoms more in the northern part of their range than in the southern part where they fed almost exclusively in or near rocky habitat. Double-crested and Pelagic cormorants showed no geographic shift in their feeding habits. The feeding ecology of marine birds has been defined in five major ways: the distance offshore at which a species feeds (inshore, offshore or pelagic; Wynne-Edwards 1935), the depth to which it dives (bottom, mid-water or surface; Balz and Morejohn 1977), the prey species consumed (Ainley and Sanger 1979), prey size (Ashmole 1968), and the methods of food capture (Ashmole 1971). Except for diving depth, little has been said about differences in feeding habitat. This contrasts markedly with land birds, whose use of microhabitats for feeding is a well-known phenomenon. In the present article we attempt to define much more narrowly the feeding habitats of three sympatric, closely related seabird species: the Pelagic, Brandt's and Double-crested cormorants (Phalacrocorax pelagicus, P. penicillatus and P. auritus). Heretofore, all have been regarded as feeding similarly, by diving beneath the surface, from the bottom to mid-depths, in inshore waters. So similar has their feeding ecology appeared that Cody (1973) was led to postulate that, in areas of sympatry, breeding seasons have become staggered as a means to distribute demand on available food resources. We obtained information on prey from the analysis of fish otoliths and invertebrate hard parts in pellets. Pellets, which cormorants apparently produce almost daily, have received very little attention from seabird researchers, yet they prove invaluable in a study such as ours. In cormorants, these pellets are equivalent to stomach samples in terms of what they indicate about diet (Jordan 1959, Schlatter and Moreno 1976; Ainley, unpubl. data). Birds do not have to be c ll cted for their stomachs nor harassed in order that they regurgitate their stomach cont nts; thus, large samples and time series of s mples can be gathered. The attainment of adequate samples to allow valid comparisons between species has posed problems in studies of marine birds (Balz and Morejo n 1977). Jordan (1959) gave a detailed description of cormorant pellets and the mechanism and frequency of their production. Why cormorants produce pellets is not known, but the fact that pellets often contain many nematodes indicates that they may aid in parasite control (Jordan 1959; Ainley, unpubl. data). They are produced only by adult and subadult cormorants; younger birds begin producing them at about the time they are able to fly. In forming the pellet, the stomach contents are enveloped in mucus secreted by the stomach wall. Upon drying, the pellet becomes very hard. A cormorant regurgitates one pellet during the night, usually just before dawn, when it departs for daily feeding. Regurgitation before daylight not

Relationship Between Primary Production and Fish Production in Lake Tanganyika

Abstract: Primary production in Lake Tanganyika, 0.8 g C˙m−2˙day−1, is not high by comparison with other tropical lakes yet the fisheries of the lake maintain annual yields of 125 kg hectare−1 (1.3 g C˙m−2˙year−1). The efficiency of carbon transfer to the fishery from primary production is anomalously high among the lakes of the world and approximates the efficiencies of the most productive marine fisheries. The great antiquity of this lake may have allowed selection of the most efficient pelagic species and resulted, in turn, in a highly efficient pelagic ecosystem where carbon accumulates as fish at the top of the trophic pyramid rather than as algae at the bottom. However, estimates of heterotrophic bacterial production equal or exceed primary production by algae. The immense volume of anoxic deep water is the likely source of energy fixed in reduced substances that could allow such high rates of bacterial production. The study of the relationship between fish production and primary production in two ot...

Effects on Artificial Reef and Demersal Fish and Macrocrustacean Communities

Abstract: This chapter provides a synthesis of the observed effects of the Buccaneer Gas and Oil Field (Figure 1) on biological systems and fisheries of the study area. Demersal fishes and macrocrustaceans, the biofouling community, and reef and pelagic fishes were used as indicators of impact. Other biological components (bacteria, plankton, and infaunal benthos) were considered as part of the “environment” and were addressed only to the extent that they directly impacted or limited the primary indicator groups.

Hydrography and its effect on fish larvae in the Mauritanian upwelling area

Abstract: During Meteor cruise 44 in January and February 1977 simultaneous hydrographical and biological investigations were carried out in the Mauritanian upwelling area . Both horizontally and vertically the hydrographic structure and fish larvae abundance were similar, apparently results of upwelling. Highest concentrations of fish larvae were found above the slope and above the outer shelf in aged upwelled water, whilst fresh upwelling water was free of larvae. The inshore boundary of fish larvae followed approximately the 16° C isotherm. Both hydrography and fish larvae populations at a given location varied in time, consequences of advection. A spatial and temporal investigation of species composition indicated that during upwelling fish larvae were carried from depths of about 30 m at the outer shelf towards the shore and northward. This pathway was also indicated by water mass analysis and current meter measurements. Within the upper 60 m the northward flow, however, decreased with increasing latitude. According to water mass analysis and species distribution there was no northward transport in the Cape Blanc area of epipelagic fish larvae, the major group within the ichthyoplankton.

Ecological Structure of the Pelagic Seabird Community in the Benguela Current Region

Abstract: The distribution of pelagic seabirds off the west coast of southern Africa I S analysed according to trophic guilds. Distribution of the b ~ r d s is not random. At any given observation station one guild dom~na tes the seabird assemblage. P~scivores and squid-eaters account for the bulk of avian abundance and biomass, the remainder being planktivores and omnivores. Intraguild competition for food apparently is reduced by interspecific differences in foraging behaviour and temporal separation. A winter increase in avian species richness and diversity, and abundance and b~omass , is supported by a seasonal increase in productivity. Correlations of seabird indices with oceanographic and meteorological parameters are poor This indicates that local sedbird distribution is mainly a function of the availability of prey and the species' attributes for locating and capturing prey. However, subsets of parameters for water masses and weather correlate with seabird distribution. INTRODUCTION STUDY AREA It is generally accepted that biological productivity in the pelagic environment can be correlated broadly with water masses characterized by temperature, salinity and suspended matter (Sverdrup et al . , 1942; Emery et al., 1973). However, only a few attempts have been made to establish statistically-sound correlations between water masses, productivity and the distribution of pelagic seabirds (Pocklington, 1979), for assessing the value of seabirds as environmental predictors across wide oceanic zones. This paper analyses the pelagic avifauna of the southern sector of the Benguela Current region, along the west coast of southern Africa, in terms of its diversity in relation to environmental features. More particularly, the question addressed in a preliminary analysis is: to what extent is the distribution and abundance of pelagic seabirds affected by measurable oceanographic and meteorological features? Moreover, the analysis identifies broad ecological and behavioural properties which affect avian distribution. The analysis was performed as part of a pilot study for developing deterministic models which could be useful generally in assessments of marine productivity and resources in the Southern Ocean. This paper constitutes part of the commemoration of the 21st anniversary of the establishment of the Percy FitzPatrick Inst~tute of African Ornithology The principal water mass associated with the continental shelf in the study area (Fig. 1) consists of the Benguela Current upwelling system, comprising water which rises from ca. 300 m depth (Hart and Currie, 1960). Temperature, salinity and productivity in the principal water mass fluctuate seasonally (Emery et al., 1973); whereas the geographical orientation of the system is relatively constant throughout the year, the centre of upwelling and thus maxlmal productivity shifts longitudinally 100-170 km between summer and winter (Hart and Currie, 1960). The western boundary of the Benguela Current water mass coincides with an offshore divergence belt, an area of upwelling dissociated from the inshore system of upwelling, which occurs at the interface between the central South Atlantic surface water mass and the south-western African continental water mass (Bang, 1971). The study area extended from 2 to 335 km offshore, corresponding to Kessel's (1979) inner front (inshore waters), to the shelf-break front (shelf edge and slope) and embraces depths between 30 and 400 m. Air temperatures, water temperatures, and salinities typical of an average year in this sub-tropical zone are 10"-27 "C, 9"-22 'C and 34-36 %O S respectively (Sverdrup et al., 1942). The Benguela Current upwelling system is highly productive (Cushing, 1971) and supports abundant populations of pelagic seabirds (Summerhayes et al., O Inter-Research/Printed in F. R. Germany 017 1 -8630/81/0005/0269/$ 02.00 wlar. Ecol. Prog. Ser. 5: 269-277, 1981 Fig. l . Southern sector of Benguela Current region. Broken line traces the edge of the continental shelf; dots represent cruise stations occupied by R. S. 'Africana 11' during 1950-1953 1974). The study area is visited by many Southern Ocean seabirds during their non-breeding phases (Brooke, in press). This, as well as the similarities in temperature and salinity between the two regions (Emery et al., 1973), allows the study area to be regarded as a northern extension of the Southern Ocean ecosystem. M A T E R I A L A N D METHODS From November 1950 to June 1953 the South African Government Research Vessel 'Africana 11' made monthly survey cruises off the west coast of South Africa (Marchand, 1952). Standard seabird watches were made by Cdr A. Thomas (for details see Cooper and Dowle, 1976), and physical oceanographic and meteorological data were obtained at the cruise stations shown in Figure 1. All birds seen were recorded with the aid of 8 X binoculars from the ship's bridge (10 m above sea level), 15 min after the ship stopped at, and just before the ship departed from, each station. Additional species seen at any other time while the ship was on station were noted. Analyses of the basic data included 15 dependent variables and 8 independent variables for multivariate correlations. The dependent variables are: bird species richness (BSR), Shannon-Wiener index (BSD = H' = p, log P, where pi is the proportion of the ith species in the community of a particular area), total number (abundance) and total (live-weight) biomass of birds, and the numbers of individual birds in each of four food type and seven feeding method guilds (Appendix 1 contains the currently accepted trophic classification of species and their weights). The independent variables are: barometric pressure, water depth, distance from shore, surface salinity, surface-water temperature, air temperature, and wind and wave strengths.

Vertical distribution and biology of pelagic decapod crustaceans off oregon

Abstract: Collections with opening-closing midwater trawls to a depth of 2,400 m and with bottom trawls were used to describe the vertical distributions of pelagic crustaceans from the surface to the sea floor at 3,000 m off Oregon. Twenty-nine species of decapod shrimps, representing 14 genera, were captured. The number of species and individuals decreased with increased depth. Sergestes similis predominated in catches in the upper mesopelagic and epipelagic waters and comprised 74 percent of the individuals in the entire water column. Only four species exhibited definite diel vertical migrations (S. similis, Bentheogennema burkenroadi, Gennadas propinquus and Pasiphaea chacei). Most species, especially carids, were nonmigratory. Some depth stratification by size and sex was noted. The size of eggs brooded by female carids showed no consistent trend to increase with increasing depth for closely related species. Within the carids and penaeids, meso- to bathypelagic species have decreased egg number compared to epipelagic species; nevertheless within the carids, the number of eggs brooded per female was always highest for the deepest living species within a genus, which were also the largest sized species. Reproductive effort showed some trends with depth, but may also be influenced by other variables, such as available food resources.

Biomass, Production, and Potential Yield of the Lake Tanganyika Pelagic Fish Community

Abstract: The Lake Tanganyika pelagic fish community consists of two short-lived clupeid species, of which Stolothrissa tanganicae is dominant, and four much larger, long-lived Lates species. Purseseine catches in previously unfished areas contained approximately equal amounts of clupeid prey and Lates predators. The annual production/mean biomass ratio for Stolothrissa is 3.5–4, which approximates the instantaneous mortality rate. Predator P/B ratios probably are less than 1. Prey fish biomass is about 230 kg/hectare, and production about 700 kg/hectare per year in the north of the lake (Burundi). Even in intensively fished areas, most prey production probably is converted to predator tissue. Without predators, potentially harvestable clupeid production in the Burundi sector would theoretically bc 350 kg/hectare per year, which extrapolates to 1.1 million t/year for the lake. Purse-seining removes Lates species faster than clupeids, leaving more clupeid production for yield. Fishery models should attempt ...

Food and feeding habits of Mirogrex fingerlings in Lake Kinneret (Israel)

Abstract: The food composition of the fingerlings (13–41 mm TL) of Mirogrex terraesanctae terraesanctae was studied on specimen collected at four stations in Lake Kinneret. The fingerling feed mostly on pelagic zooplankters and zoobenthic forms whereas algae were found in the intestines in low biomass. The number of zooplankton organisms in the guts of the fingerling that were sampled during June–August was higher by 234% than in fingerlings that were sampled during March–April. The role of sardines fry in the Kinneret ecosystem is discussed.

Fish in Salps: the Association of Squaretails (Tetragonurus Spp.) With Pelagic Tunicates

Abstract: Stromateoids are fishes of the open ocean commonly found in association with gelatinous zooplankton (Mansueti, 1963; Haedrich, 1957). One genus, Tetragonurus, has been found inside the branchial chambers of salps (Emery, 1882; LoBianco, 1909) and cloacal chambers of pyrosomes (LoBianco, 1909; Fitch, 1949, 1951).

Vegetation macrofauna and benthic meiofauna in the phytal zone of the archipelago of Luleå- Bothnian bay

Abstract: The archipelago of Lulea, in the northwestern part of the Bothnian Bay, is subjected to the lowest salinities and the most extreme weather conditions found in the Baltic Sea basin. A large scale systems ecology study of the Lulea archipelago was carried out during 1976 in order to reveal the general characteristics of the ecological communities excisting in this little known area. The quantitative studies of the phytal subsystem, presented here, revealed a very poor fauna and flora on the sandy shallow bottoms that dominate the area. The pelagic primary production is only about 10 per cent of that found in the northern Baltic proper. Together with the physical forces of ice and wave erosion and large, irregular water level fluctuations, this low production limits the distribution and production within the benthic communities. With a few exceptions, the macrofauna and macroscopic vegetation as well as meiofauna are composed by euryhaline fresh-water species able to tolerate the low salinities (0–3...

Cephalopods of the southern ocean region: potential resdurces and bibliography

Abstract: Cephalopods (squids and octopuses) are known tobe extremely important organisms in the trophic structure of the Antarctic ecosystems, constituting significant portions of the diets of sperm whales, seals, penguins; pelagic birds and fish. The southern hemisphere population of 500 000 sperm whales, for example, consumes about 50 million tonnes of cephalopods a year, according to Clarke's calculations (Voss 1973. p. 61 ). This value approximates to three-quarter of the world's current annual fisheries production. The highly evolved nervous system of cephalopods allows them to be aggressive, fastswimming predators. This characteristic, unique among invertebrates, makes them comparable in behaviour to many !arge predatory vertebrates. As predators, for example, cephalopods are estimated to consume about 100 mi!lion tonnes of Antarctic krill a year (Everson- this volume, paper 4). Knowledge of the biology and species composition of the cephalopod fauna is almost completely lacking, making an assessment of the resource potential of cephalopods in the Antarctic extremely difficult. This Iack of knowledge is due primarily to the strong swimming and net-avoidance capabilities of cephalopods, which have prohibited adequate sampling. Special sampling efforts are required therefore to elucidate their biology and resource potential. Cephalopods inhabit both pelagic and benthic habitats in the Southern Ocean. The squids are primarily pelagic and constitute the major resource potential in terms ofnumbers of species and biomass. The octopuses are primarily benthic dwellers and their biomass and consequent contribution to energy flow are relatively minor in comparison to pelagic cephalopods. This is especially the case in the shelf waters of the Antarctic continent, whereas sub-Antarctic islands appear to support !arger populations of octopuses.

Cenozoic Planktonic-Foraminifer Biostratrigraphy of Deep Sea Drilling Project Hole 462, Nauru Basin (Western Equatorial Pacific), and Distribution of the Pelagic Components

Abstract: The Cenozoic sedimentary sequence recovered at Deep Sea Drilling Project Hole 462, in the Nauru Basin, is characterized by rare layers of autochthonous pelagic clay and/or radiolarian ooze, which alternate with much more conspicuous, allochthonous, carbonate-rich graded layers. The biostratigraphic signal, based on planktonic foraminifers, is strongly biased by heavy reworking. Nevertheless, most of the biozones of the late Eocene to Pleistocene have been recognized. Boundaries between zones are sometimes only tentatively drawn. A combination of data based on host and reworked planktonic-foraminifer faunas indicates that relatively few biozones are missing in the Cenozoic, namely the Subbotina pseudobulloides, "Morozovella" trinidadenis, M. angulata, and part of the M. pusilla Zones in the Paleocene; the Morozovella formosa through Acarinina pentacamerata Zones in the early Eocene; most of the Hantkenina aragonensis and Globigerinatheka subconglobata Zones in the middle Eocene; and the upper part of Zone N4 through Zone N6 in the early Miocene. The absence of Zones N14/N15 in the middle Miocene and the completeness of the Pliocene cannot be proved. The oldest reworked fauna is dated as mid-Cretaceous. Quantitative analyses of the studied samples distinguish different types of graded layers, characterized primarily by varying distributions of the main fossiliferous components. Radiolarian-rich turbidites are common in the lower part of the sequence (late Eocene to early late Oligocene, and late Pleistocene). Foraminifer-rich turbidites occur primarily in the upper part of the Oligocene, in the middle Miocene, and in the Pliocene to early Pleistocene. Accumulation rates per zonal interval have been estimated, the highest values occurring in the latest Eocene and late Oligocene (Zone P22). Relatively high rates are recorded also in the early late Oligocene, latest Oligocene, middle Miocene, and late Pliocene. It is suggested that these high accumulation rate values are related to erosional events dated at ~ 37, ~ 32, ~ 26, -24?, -13 , and possibly 3 m.y. ago, as well as during the Pleistocene. The most important events are those dated at -37 (latest Eocene) and at -26 m.y. ago (late Oligocene, Zone P22). INTRODUCTION The present depth of the Nauru Basin (western equatorial pacific) is over 5000 meters, and Hole 462 was drilled at a water-depth of 5183 meters below sea level, on Anomaly M-26, which according to Larson and Hilde (1975) dates the ocean crust below the Nauru Basin at -150 (m.y. old). Although the subsidence path of the Nauru Basin deviated from the Parson-Sclater curve (see Schlanger and Premoli Silva, this volume), its floor has been below the carbonate compensation depth (CCD) since the Early Cretaceous. The whole Cenozoic sedimentary sequence was recovered continuously at Hole 462, at least down to Core 39 at a depth of 370 meters sub-bottom; it is characterized by an alternation of pelagic clay with carbonaterich and/or radiolarian-rich layers, at first sight very similar to pelagic oozes. By analogy with modern sediments, and in agreement with the location of the Nauru Basin's bottom below the CCD during the whole Cenozoic, the interbedded pelagic clay, which mainly yielded fish debris and abyssal, non-calcareous agglutinated foraminifers, must be considered the only indigenous sediments in this location. Consequently, the occurrence Initial Reports of the Deep Sea Drilling Project, Volume 61. of carbonates throughout the Cenozoic sequence at Site 462 is anomalous and results from mechanical redeposition rather than planktonic fallout. Analysis by binocular microscope of the washed residues of the > 63-μm fraction, confirmed by quantitative analyses, reveals that sediments other than pelagic clay are finely graded, and range from coarse foraminifer and/or radiolarian sand to nannofossil silt. Planktonic foraminifers exceeding 250 μm, almost without matrix, are the main components of the bottom of the most complete sequences. The sequences grade upward, via finer-grained planktonic foraminifer-radiolarian silty sand, to nannofossil silt, eventually topped by pelagic clay. Redeposition processes involved a large amount of reworking. Unlike the Cretaceous sediments, in which reworking was a minor feature, both in total amount and in terms of ages of the eroded sediments, Cenozoic planktonic-foraminifer faunas are so mixed that the biostratigraphic signal may be strongly masked. The associated calcareous benthic foraminifers show that the sources of the displaced material were mainly areas at bathyal depths. Shallow-water skeletal debris, frequently associated with abundant volcanic material, and outer-shelf to upper-bathyal faunas are contained in some very coarse graded layers interbedded episodically in the turbiditic sequence (see Premoli Silva

Concentrations of radionuclides in reef and lagoon pelagic fish from the Marshall Islands

Abstract: A radiological survey was conducted from September through November of 1978 to assess the concentrations of persistent man-made radionuclides in the terrestrial and marine environments of 11 atolls and 2 islands of the Northern Marshall Islands. The atolls and islands include Rongelap, Utirik, Taka, Bikar, Rongerik, Ailinginae, Likiep, Jemo, Ailuk, Mejet, Wotho, Ujelang and Bikini. Over 4000 terrestrial and marine samples were collected for radionuclide analysis from 76 different islands. Soils, vegetation, indigenous animals, and cistern and groundwater were collected from the islands. Reef fish, pelagic species, clams, lagoon water, and sediments were obtained from the lagoons. A report is given of all available concentration data for /sup 137/Cs, /sup 90/Sr, /sup 239+240/Pu, /sup 238/Pu, /sup 241/Am as well as naturally occurring /sup 40/K and other gamma emitting radionuclides in tissues and organs of different species of fish collected from the atolls.

Juvenile Salmonid and Baitfish Distribution, Abundance and Prey Resources in Selected Areas of Grays Harbor, Washington

Abstract: : A comprehensive studies of juvenile salmonids, English sole, and baitfish and their epibenthic and neritic prey communities was conducted in Grays Harbor in order to evaluate the potential effects of dredging proposed for widening and deepening the existing navigation channel. Quantitative stomach analyses of juvenile salmonids and English sole indicated that they fed mainly in the epibenthic and neritic habitats in which they were captured. Fishes occupying shallow sublittoral or lower littoral habitats fed mainly on epibenthic crustaceans--primarily harpacticoid copepods, cumaceans, and gammarid amphipods--while those captured in neritic habitats tended to be larger in size and fed upon more pelagic prey such as larval northern anchovy and drift insects. Potential impacts of the proposed dredging project were considered to be either a direct reduction in the fish populations as a result of dredging operations or an indirect reduction of the carrying capacity by removal of preferred habitat or alteration of migration or residence patterns. Of the indirect effects assessed in this report, only the permanent loss of shallow sublittoral habitat, estimated to involve 1.1% of the total sublittoral habitat in the estuary, may be deleterious particularly to juvenile chinook and chum salmon, and young-of-the-year English sole, which forage and rear almost exclusively in this habitat in Grays Harbor.

A synopsis of PROBES

Abstract: The Processes and Resources of the Bering Sea Shelf (PROBES) project is a 6-year multi-institutional (University of Alaska, Florida State University, University of Washington, Brookhaven National Laboratory, Southwest Fisheries Center, Bigelow Laboratory for Ocean Sciences) interdisciplinary study designed to understand the processes that contribute to the production of enormous numbers of animals (including crabs, fish, birds, mammals) in secondary and higher trophic levels in the vast Bering Sea continental shelf. The research plan is based on the hypothesis that the broad shallow shelf leads to an oceanographic structure of a semi-permanent front-interfront system in which phytoplankton primary production is coupled to a pelagic food web over the outer shelf and to a benthic food web in the middle shelf (see cover, this issue). The project has concentrated on the processes that control the survival of the early life history stages of the Alaska pollock (Theragra chalcogramma Pallas) as an example of mass and energy transfer in the pelagic system. PROBES began in 1976 and is sponsored by the Division of Polar Programs, National Science Foundation.

Environmental assessment of the Alaskan Continental Shelf: final reports of principal investigators, volume 12. Biological studies

Abstract: This report contains results on: reproductive ecology, foods and foraging areas of seabirds nesting on the Pribilof Islands, 1975-1979; Pelagic and Demersal Fish assessment in the Lower Cook Inlet estuary system; Epipelagic meroplankton, juvenile fish, and forage fish: Distribution and relative abundance in coastal waters near Yakutat.

Production ecology in the Northern Baltic

Abstract: Production biology in the Bothnian Bay is discussed and compared to that of the southern parts of the Baltic. Severe ice-conditions, low water temperatures in spring and early summer and a pronounced water-colouring cause a delay of the spring development of phytoplankton and a low annual production in the Bothnian Bay. This delay makes possible a higher efficiency of the pelagic system as the zooplankton fauna can develop in harmony with the food resources. The downward transport of energy and matter to the bottom communities from an efficient pelagial should be small and temporally unpredictable, which is thought to be an adequate explanation of the observed very low benthic fauna biomasses in the Bothnian Bay.