Zone Of High Productivity Research Articles

Distribution and life history of the planktonic copepod, Eucalanus californicus, in the northwestern Pacific: Mechanisms for population maintenance within a high primary production area

We investigated the geographical and vertical distribution of the copepodid stages of Eucalanus californicus in the northwestern (NW) Pacific Ocean, and compared life history characteristics against the northeastern (NE) population of the species and the neighboring subarctic sister species, Eucalanus bungii. In the NW Pacific, multi-layered zooplankton samples were collected between 15°N and 49°N. High abundances (>1000inds. m−2) of E. californicus were restricted to an area around 33°N, whereas E. bungii was highly abundant between 36°N and 49°N. The occurrence of E. californicus in the surface layer was associated with seasonal spring ontogenetic vertical migration (OVM), as suggested by previous studies in the NE Pacific. Gonadal analysis of adult females showed that surface reproduction occurs during the spring in the slope water area, which is a region on the continental slope north of the Kuroshio axis, and within the Kuroshio–Oyashio Transition Area (TA). The seasonal OVM strategy of E. californicus in the NW Pacific is characterized by (1) shorter periods of surface reproduction and growth and (2) deep C5 stage dormancy (500–2000m). The former is an adaptive response to relatively high water temperatures and short bloom periods in the TA and slope water area. The latter strategy of deep dormancy is considered to be an adaptation to avoid drift caused by a local oceanic feature of deeper westward (>1000m) recirculation currents, thus retaining the population within the high primary production zones of the TA and slope water area.

What ocean biogeochemical models can tell us about bottom-up control of ecosystem variability

AbstractGnanadesikan, A., Dunne, J. P., and John, J. 2011. What ocean biogeochemical models can tell us about bottom-up control of ecosystem variability. – ICES Journal of Marine Science, 68: 1030–1044. Processes included in earth system models amplify the impact of climate variability on phytoplankton biomass and, therefore, on upper trophic levels. Models predict much larger relative interannual variability in large phytoplankton biomass than in total phytoplankton biomass, supporting the goal of better constraining size-structured primary production and biomass from remote sensing. The largest modelled variability in annually averaged large phytoplankton biomass is associated with changes in the areal extent of relatively productive regions. Near the equator, changes in the areal extent of the high-productivity zone are driven by large-scale shifts in nutrient fields, as well as by changes in currents. Along the poleward edge of the Subtropical Gyres, changes in physical mixing dominate. Finally, models indicate that high-latitude interannual variability in large phytoplankton biomass is greatest during spring. Mechanisms for producing such variability differ across biomes with internal ocean processes, such as convection complicating efforts to link ecosystem variability to climate modes defined using sea surface temperature alone. In salinity-stratified subpolar regions, changes in bloom timing driven by salinity can produce correlations between low surface temperatures and high productivity, supporting the potential importance of using coupled atmosphere–ocean reanalyses, rather than simple forced ocean reanalyses, for attributing past ecosystem shifts.

Interpretation of the paleo-primary production record in the NW African coastal upwelling system as potentially biased by sea level change

Using a regional circulation-ecosystem model subject to a set of boundary conditions that reflect present-day (PD) and Last Glacial Maximum (LGM) conditions, we investigate how changes in preformed subsurface nutrient concentrations as opposed to a local drop in sea level or increase in wind stress influence the biological productivity off the northwest African coastal upwelling area. A reduction of subsurface nutrient concentration at LGM reduced the zonally averaged primary production (PP). The sea level change modifies the shelf morphology, the upwelling circulation, and the productivity and displaces the high-productivity zone. According to our model results, the sedimentary record of PP is best explained by a simulation considering a doubled wind stress over NW Africa. We conclude that production regionally along the coast of NW Africa during the LGM may have been lower than today, despite the fact that most of the sediment cores north of 22°N show local increases in PP during the last glacial period. This paradox may be due to the sea level change and the associated eastward shift of the coastline and upwelling system.

The flight activity of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and Teretrius nigrescens Lewis (Coleoptera: Histeridae) in Kenya

The invasive storage pest, the larger grain borer (LGB) Prostephanus truncatus (Horn), was introduced into the maize-deficit, semi-arid areas of the eastern region in Kenya in the early 1980s. In spite of containment efforts and the introduction of the predator Teretrius nigrescens Lewis from Mexico, LGB has spread to the main maize production zone in western Kenya during the past five years. The present work presents results from a 28-month monitoring effort of LGB and its predator, using pheromone traps at five locations along an east-west transect across Kenya. LGB occurred in all regions with highest trap catches in the high potential maize production zones in Western Kenya. T. nigrescens had not spread to western Kenya and trap catches were very low and mostly zero in Eastern Kenya, even in the area where it was released during the 1990s, suggesting that it became locally extinct after initial establishment. LGB flight activity was closely related to relative humidity, temperature and vapour pressure deficit. A model based on climatic factors accurately predicted seasonal trends of LGB flight behaviour in Kakamega and Mombasa but not in Kitale and Thika. It was concluded that models that rely on the direct effect of climate cannot predict LGB flight accurately enough to allow assessment of the impact of T. nigrescens on a regional basis. It is suggested that other factors such as the availability of stored grain and thus the indirect effect of climate via enhanced or reduced crop production play a major role in the flight activity of LGB and T. nigrescens.

ENVIRONMENTAL CHALLENGES OF BREEDING PEACHES FOR LOW CHILL REGIONS

Peach production throughout the world suffers from a multitude of environmental challenges related to both temperature and humidity but it is mainly the stress caused by excessive warmth that makes the low chill regions (<500 chill hour accumulation) of the world unique from those of the high chill production zones. These mild winter environments range from the cool highland mountains of Mexico where peaches can be induced to flower in the summer months so the fruit is harvested in the off season winter months, to hot dry deserts where flower induction is needed to synchronize bloom in the absence of a distinct cool season, to the humid and cool spring lowland environment of southern Brazil, to the humid but warm spring lowland environment of south and central Texas, and to the greenhouse environment of peach protected culture in Asia. The major abiotic environmental challenges are for adaptation to low chilling accumulation, cold damage during bloom, and in many cases also to high heat especially during bloom time but also during subsequent growth of the fruit and the tree. These factors affect productivity as well as fruit ripening time, size and quality.

Temporal variations of C, N, δ13C, and δ15N in organic matter collected by a sediment trap at Cuenca Alfonso, Bahía de La Paz, SW Gulf of California

To monitor the composition and the vertical flux of particulate matter from the sea surface, a sediment trap was moored in Cuenca Alfonso, Bahía de La Paz, a zone of high productivity in the southwestern Gulf of California. Carbonate-free samples from 2002 to 2005 were analyzed for C org, N, δ 13C, and δ 15N. The results show seasonal and interannual variability, with the δ 13C and δ 15N values larger in spring and summer than in fall and winter. The C:N ratio and δ 13C increased by 1.5 units from 2002 to 2003–2005, suggesting a change in the supply of organic matter and-or the use or preferential degradation of N org. There was no interannual variation in δ 15N. The occasional high δ 15N values suggest that physical mechanisms, such as the shoaling and advection into the bay of 15N-rich subsurface equatorial water, occur over short time periods. The latter is presumed to be related to the periodic development of a significant cyclonic gyre in the southern Gulf.

Characterization of crop growing environment of chickpea in Haryana

The data on area, production and productivity of chickpea crop in different districts of Haryana were collected for 27 seasons (1978-79 to 2004-2005) to study characterization of crop growing environments. The data showed that there had been drastic decrease in area and production in north and central part of the state. The southern parts of the state showed comparatively less decrease or increase in area and production. There is no trend in the productivity. By analyzing the trends of recent years, the districts of Hisar and Bhiwani had high spread and high productivity during 1993-97 periods. Sirsa fell in medium spread and high productivity zone, whereas Mahendergarh, Jind, Gurgaon and Rohtak had low spread but high productivity. In the recent pentad (1998 to 2002), only Bhiwani district had high spread and medium productivity, whereas Sirsa and Hisar recorded medium spread but high productivity. Mahendergarh, Jind and Gurgaon fell in low spread and high productivity category, whereas Rohtak falls in low spread and medium productivity zone. Models have been developed to predict chichpea yield in Karnal and Mahendergarh districts.

Upper quaternary laminated sapropelic sediments from the continental slope of Baja California

Core MD02-2508 retrieved from the plateau of the continental slope off Baja California recovered a 40-m-thick section of sapropel (up to 15% Corg), calcareous clay, and diatom ooze with the age of 120 ka at the core bottom. The section is subdivided into three units: Unit I (Holocene) consists of the laminated sapropel; Unit II comprising oxygen isotope stages (MIS) 2, 3, and 4 is represented by homogeneous calcareous clay with interbeds of slightly siliceous sapropelic mud; and Unit III (MIS-5) is composed of laminated sapropelic diatom ooze. Laminated intervals are characterized by the intercalation of two lamina types: (1) dark-colored organic-rich laminae containing multi-species “oceanic” diatom assemblages, as well as radiolarians, coccoliths, planktonic and benthic foraminifera; (2) lighter-colored laminae consisting of diatom ooze with the neritic colonial diatom assemblages commonly composed of one to three species of a single genera. The dark laminae are assumed to be generated within a high productivity zone over the slope, whereas light ones likely represent diatom mats produced by short-term boisterous phytoplankton blooms, possibly in the coastal upwelling.

Integrated seismic and magnetotelluric exploration of the Skierniewice, Poland, geothermal test site

The purpose of the research activities at the Skierniewice geothermal test site is to develop and apply an exploration methodology for low-enthalpy systems in sedimentary formations. Work included seismic and magnetotelluric surveys carried out close to well Kompina-2 to create a detailed structural–geologic model and characterize the anisotropic fracture system around the borehole. The study included the reprocessing of archival data from selected boreholes and 2D seismic lines. The collected data were used to identify formations with high fracture permeability and the presumed flow path of geothermal (∼110 °C) brine in high productivity zones, and determining rock porosities and salinity distribution in the subsurface. The next stage of the investigations will focus on siting a second borehole and studying the possibility of installing a plant for electrical generation or direct geothermal heat applications.

Geophysical investigation of seamounts near the Ogasawara Fracture Zone, western Pacific

Abstract This paper provides an analysis of multi-channel seismic data obtained during 2000–2001 on seamounts near the Ogasawara Fracture Zone (OFZ) northwest of the Marshall Islands in the western Pacific. The OFZ is unique in that it is a wide rift zone that includes many seamounts. Seven units are delineated on the basis of acoustic characteristics and depth: three units (I, II, and III) on the summit of seamounts and four units (IV, V, VI, and VII) in basins. Acoustic characteristics of layers on the summit of guyots and dredged samples indicate that the seamounts had been built above sea level by volcanism. This was followed by reef growth along the summit margin, which enabled deposition of shallow-water carbonates on the summit, and finally by subsidence of the edifices. The subsidence depth of the seamounts, estimated from the lower boundary of unit II, ranges between 1,550 and 2,040 m. The thick unit I of the southern seamounts is correlated with proximity to the equatorial high productivity zone, whereas local currents may have strongly affected the distribution of unit I on northern seamounts. A seismic profile in the basin around the Ita Mai Tai and OSM4 seamounts shows an unconformity between units IV and V, which is widespread from the East Mariana Basin to the Pigafetta Basin.

Foraging strategy of masked boobies from the largest colony in the world: relationship to environmental conditions and fisheries

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 362:291-302 (2008) - DOI: https://doi.org/10.3354/meps07424 Foraging strategy of masked boobies from the largest colony in the world: relationship to environmental conditions and fisheries Henri Weimerskirch1,*, Matthieu Le Corre2, Charles A. Bost1 1Centre d’Etudes Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France 2Laboratoire d’Ecologie Marine, Université de la Réunion, 15 avenue René Cassin, BP 7151, 97715 Saint Denis, Ile de la Réunion, France *Email: henriw@cebc.cnrs.fr ABSTRACT: The largest masked booby Sula dactylatra colony in the world, with >100000 individuals, is located in the eastern tropical Pacific (ETP) on Clipperton Island. We studied their foraging ecology and their relationship with the environment as well as with the tuna purse seine fishery. We examined the movements of birds at sea and studied their diet. Breeding masked boobies foraged mainly during day time, departing early in the morning and returning late in the evening, with a few birds spending the night at sea mainly in flight. The foraging range of birds rearing chicks was on average 103 km (maximum 242 km), with 73% of the time spent in flight. Foraging zones, as measured by first passage time analyses, indicated that zones of area-restricted search (ARS) were 3 km in diameter on average (average duration 1 h) and were located at the extremity of individual trips. ARS zones were dispersed around Clipperton, with no particular concentration, and individual birds never returned to the same ARS from one trip to the next. These results suggest that the foraging sectors of masked boobies were unpredictable at a small scale. The foraging area was located in a zone of high primary production that had drifted from the coasts of Central America. This large-scale feature appears to be predictable and explains the strong seasonality in the breeding season of the population. This peak of productivity occurs year after year around the island in January to March, i.e. during the time of highest energy demand for the colony, when birds are feeding large chicks. Masked boobies dove at an average depth of 2 m (maximum 6 m) and fed almost exclusively on flying fishes, with an estimated daily catch for the population of 69 t of fish. Around Clipperton, yellowfin tuna are caught by the purse seine fishery in large numbers in association with dolphins. Since boobies are observed feeding almost exclusively in association with tuna and dolphins that drive flying fish to the surface, making them accessible for the birds, their dependence on tuna suggests that overexploitation of tuna stocks in this area could have a negative impact on the masked booby population. KEY WORDS: Clipperton Island · Sula dactylatra · GPS · Eastern Tropical Pacific · Tuna fishery Full text in pdf format PreviousNextCite this article as: Weimerskirch H, Le Corre M, Bost CA (2008) Foraging strategy of masked boobies from the largest colony in the world: relationship to environmental conditions and fisheries. Mar Ecol Prog Ser 362:291-302. https://doi.org/10.3354/meps07424 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 362. Online publication date: June 30, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Predicting the global distribution of planktonic foraminifera using a dynamic ecosystem model

Abstract. We present a new planktonic foraminifera model developed for the global ocean mixed-layer. The main purpose of the model is to explore the response of planktonic foraminifera to different boundary conditions in the geological past, and to quantify the seasonal bias in foraminifera-based paleoceanographic proxy records. This model is forced with hydrographic data and with biological information taken from an ecosystem model to predict monthly concentrations of the most common planktonic foraminifera species used in paleoceanography: N. pachyderma (sinistral and dextral varieties), G. bulloides, G. ruber (white variety) and G. sacculifer. The sensitivity of each species with respect to temperature (optimal temperature and range of tolerance) is derived from previous sediment-trap studies. Overall, the spatial distribution patterns of most of the species are in agreement with core-top data. N. pachyderma (sin.) is limited to polar regions, N. pachyderma (dex.) and G. bulloides are the most common species in high productivity zones, while G. ruber and G. sacculifer are more abundant in tropical and subtropical oligotrophic waters. For N. pachyderma (sin) and N. pachyderma (dex.), the season of maximum production coincides with that observed in sediment-trap records. Model and sediment-trap data for G. ruber and G. sacculifer show, in general, lower concentrations and less seasonal variability at all sites. A sensitivity experiment suggest that, within the temperature-tolerance range of a species, food availability may be the main parameter controlling its abundance.

Organic-walled dinoflagellate cysts and benthic foraminifera in coastal sediments of the last century from the Gulf of Tehuantepec, South Pacific Coast of Mexico

Qualitative and quantitative analysis of recent organic-walled dinoflagellate cysts (dinocysts) was performed on surface sediment samples and a core from the continental shelf of the Gulf of Tehuantepec, Mexico, in order to document the spatial distribution of dinocyst assemblages in relation to upwelling and primary productivity, and to assess the environmental history of the last century. The analyses of surface sediment samples show a close relation between dinocyst assemblages and productivity on a regional scale. Polysphaeridium zoharyi and heterotrophic taxa (notably Brigantedinium spp.) dominate in the high productivity zone, whereas Spiniferites delicatus and other phototrophic taxa are more abundant in the lower productivity zone. Sediment in an eighteen cm long gravity core (dated using 210Pb and 137Cs) provided a record of the last century at annual to decadal resolution, thus yielding a unique opportunity to examine variations in dinocyst assemblages associated with environmental changes. Cyst concentrations in the core range between 477 and 2300 cysts g − 1 , giving cyst fluxes between 68 and 494 cysts cm − 2 yr − 1 . Twenty-three phototrophic and heterotrophic cyst taxa were identified. Brigantedinium spp., P. zoharyi and Bitectatodinium spongium are dominant, and are associated with the seasonal upwelling that characterizes the area. Cysts of potentially toxic species such as P. zoharyi (the cyst of Pyrodinium bahamense var. compressum and/or bahamense) occur throughout the core. Despite slight variations in relative abundances of the taxa in the assemblages, there is no evidence for eutrophication following industrial development of the adjacent coastal zone. Core samples were also analyzed for benthic foraminiferal content in order to determine possible effects of high, upwelling-induced productivity on bottom water oxygenation. The benthic foraminiferal assemblages are dominated by Hanzawaia concentrica (over 50%), with less abundant Uvigerina excellens, Cancris spp. , Planulina ornata, Quinqueloculina lamarckiana, Epistominella sandiegoensis, Nonionella basispinata, Cassidulina modeloensis and Textularia foliacea. The benthic foraminiferal assemblages are characteristic of oxygen concentrations above 1 ml l − 1 , indicating that possible changes in productivity did not significantly affect bottom water oxygen concentrations over the last 100 years.

Spatial distribution ofCubiceps pauciradiatus(Perciformes: Nomeidae) in the tropical Indian Ocean and its importance in the diet of large pelagic fishes

The bigeye cigarfish (Cubiceps pauciradiatus) is a small pelagic nomeid of the tropical world ocean, often recovered in the stomach contents of top predators such as tunas, billfishes and marine mammals. In the Indian Ocean, a few studies have investigated the biology and the ecology of this species that is one of the most abundant fish of the intermediate trophic levels. In this paper, we investigated the spatial distribution of C. pauciradiatus in the Indian Ocean using pelagic trawl catches carried out between 20°N and 45°S, and the importance of bigeye cigarfish in the diet of 9 piscivorous fishes sampled by different fishing gears in the western part of the Indian Ocean. The highest densities were observed along the eastern coast of Africa and in the Arabian Sea (87 000 individuals per square nautical mile) during the South-West Monsoon and in the eastern part of the Seychelles archipelago (62 200 ind. square nmi) during the North-East Monsoon. Small sized bigeye cigarfish (20–80 mm SL) was a regular and abundant prey (20 to 200 ind. per stomach) for schooling predators exploited by purse seine fishery such as large yellowfin and bigeye tunas chasing prey near the sea surface. Large sized bigeye cigarfish (61–150 mm SL) occurred in small numbers (3 to 20 ind. per stomach) in the stomach contents of swordfish and of large yellowfin and bigeye tunas caught by longline sets at great depths. Large concentrations of bigeye cigarfish occurred in zones of high productivity, and that species constituted seasonally a strong link in the transfer of energy from low to high trophic levels in this part of the Indian Ocean.

Spatial match–mismatch in the Benguela upwelling zone: should we expect chlorophyll and sea‐surface temperature to predict marine predator distributions?

Summary Remote‐sensing measurements of marine primary productivity are widely used to predict the distribution and movements of marine top predators, despite the fact that predators do not feed directly on phytoplankton but several trophic levels higher up the food chain. To test for potential links between primary productivity and top‐predator feeding hotspots, we assessed spatial match–mismatch across four trophic levels of the Benguela upwelling zone (south‐east Atlantic). The food chain studied consisted of phytoplankton, zooplankton (copepods), pelagic fish (anchovies and sardines) and two top predators (Cape gannets Morus capensis and human fisheries). Remote‐sensing data of sea‐surface temperature (SST) and chlorophyll_a concentration were used as indices of phytoplankton abundance throughout the study area. Copepod biomass and pelagic fish density were determined during at‐sea surveys in the South African section of the Benguela using net tows and hydro‐acoustics, respectively. Seabird (Cape gannet) home ranges and foraging zones were assessed from two Namibian breeding colonies (Mercury and Ichaboe) and two South African colonies (Lambert's Bay and Malgas) using global positioning system (GPS) tracking. Industrial fishing for anchovies and sardines was investigated using South African landing statistics and logbooks. Our spatial analyses revealed a strong match of seabird at‐sea habitat and zones of high primary productivity throughout the southern Benguela. Conversely, there was a marked spatial mismatch between copepods and pelagic fish, as well as between pelagic fish, seabirds and human fisheries: copepods were present in the southern Benguela but pelagic fish usually feeding upon them were located further east (Indian Ocean), outside of the Benguela sensu stricto. Consequently, the majority of these pelagic fish were out of reach for seabirds and fisheries confined to the southern Benguela. Synthesis and applications. Our study demonstrates the impact of an ecosystem shift across one of the world's most productive marine ecosystems and highlights the limitations of using remote‐sensed patterns of primary productivity to interpret the foraging behaviour of marine top predators. These findings underline the importance of a better knowledge of food web spatial dynamics to support ecosystem‐based fisheries management and the conservation of marine top predators.

Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos–Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ∼ 40° relative to “stable” Europe. Due to ambiguities in hemispheric origin (N or S) and thus paleomagnetic polarity, the observed declinations could indicate either clockwise (CW) or counterclockwise (CCW) vertical-axis rotations. Thus at Adriani (Koroni), the primary declinations indicate either CW or CCW rotations of ∼ 95° or ∼ 84°, depending on paleomagnetic polarity and age. The primary inclinations for all Peloponnesus sites indicate peri-equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other Mediterranean orogenic belts. Our new paleomagnetic data support the interpretation that Mesozoic radiolarites within the Tethys Ocean were originally deposited along peri-equatorial belts of divergence and high biologic productivity.

Methods and Applications of Cenozoic Marine Diatom Biostratigraphy

Diatoms provide the chief Cenozoic biostratigraphic tool in marine sediments beneath high primary productivity zones, especially where calcareous fossils are rare or poorly preserved. Diatom biostratigraphy, which is based on originations and extinctions of unique taxa, is especially useful in circum-Antarctic, equatorial Pacific, and high latitude North Pacific marine successions, which are available largely from ocean drilling. Oligocene to Holocene diatom biostratigraphic zonations are correlated with the geopaleomagnetic timescale, resulting in age control of million-year to as little as hundred-thousand year resolution. Paleocene and Eocene zonations are less well developed and have lower chronostratigraphic control, but are more widely applicable, because planktonic diatom assemblages of the globally warm early Paleogene were less provincial. We review the principals and methods of biostratigraphy and the application of diatoms to age control in stratigraphic successions worldwide. Distinct biostratigraphic zonations defined for the low latitudes, the North Pacific and the Antarctic, are reviewed, and Atlantic records and Antarctic coastal records are discussed. New biostratigraphic tools are introduced, including multidimensional graphic correlation of published diatom ranges.

Comparing the catch efficiency with different types of plankton nets in the high production zones of the Pacific Ocean

A comparison of the qualitative and quantitative characteristics of zooplankton caught by five different types of plankton nets was performed on the basis of the data of plankton surveys in various high production zones of the Pacific Ocean (392 zooplankton samples) in order to determine conversion coefficients for a more adequate quantitative estimation of plankton. In epipelagic zones, both the abundance and biomass of zooplankton caught by a Juday net were practically everywhere higher as compared to those estimated with the use of JuOM and Norpak nets but lower than the values obtained with Bongo nets. For the sake of the comparison of the quantitative estimations with different nets, we suggest coefficients equal to the ratios of the zooplankton biomass from a Juday net to the biomasses from other nets: from 0.4 to 1.5 for the total biomass values and from 0.3 to 2.3 for individual groups of zooplankton. The coefficients applied at the TINRO to account for the plankton underhauling with big Juday nets are reasonable and reliable for most of the dominating groups except for chaetognats, which are twice overestimated.

Structural and stratigraphic controls on fold-related fracturing in the Zagros Mountains, Iran: implications for reservoir development

Abstract New observations of fracture corridors &gt; 150 m tall and planes of bedding-parallel slip are integrated with sedimentological descriptions of the Asmari Formation to understand the main controls on the development of fractures in the Zagros Mountains of Iran. In the Kuh-e Pahn, fold-related fracture corridors are axis-parallel (NW-SE) and occur in the crest of the anticline. They form by neutral surface folding, but at a critical dip of the beds (c. 15°), bedding-parallel slip by flexural slip folding is the predominant mechanism. This relationship is substantiated by curvature calculations. Crestal fractures have a large vertical extent in mechanical unit B (&gt; 150 m), primarily due to the lithological homogeneity of massive packstones within the Asmari Formation. Northerly and easterly trending fracture corridors, interpreted from satellite imagery, are spatially unrelated to the detachment folding of the cover series, but represent the distributed effect of deep-seated basement reactivation related to fault movement. These trends define high production zones in the nearby Gachsaran super giant oilfield. Observations from an adjacent eroded box fold, the Kuh-e Mish, with steeper dipping limbs (60°), revealed a contrast in the style of deformation, and we interpret these folds to represent different stages in box fold evolution.

Development of a coupled physical–biological ecosystem model ECOSMO: Part I: Model description and validation for the North Sea

A 3-D coupled biophysical model ECOSMO (ECOSystem MOdel) has been developed. The biological module of ECOSMO is based on lower trophic level interactions between two phyto- and two zooplankton components. The dynamics of the different phytoplankton components are governed by the availability of the macronutrients nitrogen, phosphate and silicate as well as light. Zooplankton production is simulated based on the consumption of the different phytoplankton groups and detritus. The biological module is coupled to a nonlinear 3-D baroclinic model. The physical and biological modules are driven by surface forcing at temporal scale of 6 h using atmospheric re-analysis data. The model was integrated for 1984 and 1986. The simulated fields for 1984 were used to investigate the annual spatial distribution of phytoplankton and zooplankton biomass and their production in the North Sea. A detailed validation showed that the model, based on consideration of limiting processes, is able to reproduce the observed spatial and seasonal variability of the North Sea ecosystem e.g. the spring bloom, summer sub-surface production and the fall bloom. Distinct differences in regional characteristics of diatoms and flagellates could be modeled and their different roles in the seasonal cycle were resolved by ECOSMO. Moreover, the model was able to describe seasonal and regional characteristics of zooplankton biomass. In contrast to earlier models ECOSMO was able to identify frontal environments as zones of high productivity, and the simulations characterized the dynamics of different zooplankton feeding environments with special emphasis on the role of frontal production. For the second trophic level the regional increase of production in the frontal zone was found to be several times higher than for the first trophic level.