bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decadal‐scale variations of ecosystem productivity and control mechanisms in the Bohai Sea
Authors: Tang Qisheng , Jin Xianshi , Wang Jun , Zhuang Zhimeng , Cui Yi , Meng Tianxiang 
Published: September 2003

AbstractDecadal‐scale variations of ecosystem productivity in the Bohai Sea are described by using the survey data of 1959–60, 1982–83, 1992–93 and 1998–99. Indices including chlorophyll a concentration, primary production, phytoplankton abundance, zooplankton biomass and fishery biomass were used to describe the ecosystem productivity at different trophic levels. During the past four decades, the productivity and community structure of the Bohai Sea ecosystem has been highly variable. Primary productivity and fish productivity decreased from 1959 to 1998, such that phytoplankton abundance in 1992 and 1998 was about 38% of that in 1959 and 1982, fishery biomass in 1998 was particularly low, which was only about 5% of that in 1959. Zooplankton secondary productivity also showed a decreasing trend from 1959 to 1992, but reached high levels in 1998, about three times as much as 1959 and 1982, and four times as much as 1992. These results indicate that a large variation in ecosystem productivity is one of the important characteristics of coastal ecosystem dynamics. Therefore, it is impossible to apply a single theory to explain the causes of variations in the Bohai Sea ecosystem as the changes in productivity are likely to be forced and/or modulated by multiple mechanisms.
Periodic changes in the zooplankton of the North Sea during the twentieth century linked to oceanic inflow
Authors: Reid Philip C. , Edwards Martin , Beaugrand Gregory , Skogen Morten , Stevens Darren 
Published: September 2003

AbstractOceanic inflow is estimated to contribute more than 90% of the nutrient input into the North Sea. Variability in the volume, chemical properties, biological content and source of the inflowing water is thus likely to have a considerable effect on North Sea ecosystems. Changes seen in the plankton, and in particular Calanus finmarchicus and Calanus helgolandicus, over the last 40 years as measured by the Continuous Plankton Recorder survey, allow clear periods to be identified that appear to be associated with variability in inflow. Monthly estimates of inflow and outflow across a section between Orkney and Utsira in Norway as well as netflow (sum of Baltic outflow, runoff and Channel inflow), have been derived from runs of the NORWECOM model for two integrated depth intervals: surface to 150 m and >150 m. A comparison is made between the physical model output and plankton results for the period 1958–99. Distinct plankton periods that appear to reflect changing inflow events are discussed in relation to hydrometeorological and earlier plankton studies over approximately the last 100 years.
Abundance of Calanus sinicus across the tidal front in the Yellow Sea, China
Authors: Liu G. M. , Sun S. , Wang H. , Zhang Y. , Yang B. , Ji P. 
Published: September 2003

AbstractThe abundance of Calanus sinicus eggs, nauplii, copepodites and adults and chlorophyll a (Chl‐a) concentration were studied across tidal fronts in October 2000, and May and June 2001 in the Yellow Sea, China. The aim of the study was to evaluate the role of tidal fronts in the ecology of C. sinicus. The hydrographic tidal fronts were identified by the horizontal temperature gradient in the bottom layer and the temperature profiles across the fronts. The survey results showed that the concentration of Chl‐a was high in the vicinity of the fronts, particularly in spring and early summer. The abundance of C. sinicus eggs and nauplii was usually higher in the tidal fronts than in the adjacent areas. In May and June 2001, the abundance of copepodites and adults of C. sinicus peaked in the tidal front. In June 2001 and October 2000, many copepodites and adults were found in stratified region.
Scale issues in marine ecosystems and human interactions
Authors: Ian Perry R. , Ommer Rosemary E. 
Published: September 2003

AbstractUnderstanding the reciprocal interactions between humans and marine ecosystems has several fundamental difficulties, in particular compatible methodologies and different analytical scales. The issue of scale is central, as the scales chosen for studies of marine systems and human interactions can constrain recognition of the drivers and responses of these systems to global changes. The essential task is to discover how to combine social and natural science scale analyses to understand the impact of natural systems on people and the impact of people on natural systems. We identify characteristic spatial, temporal and organizational scales in marine ecosystems and human interactions, and the difficulties inherent in their cross‐disciplinary application. An approach is suggested focusing on communities of fish and fishers that makes explicit: (1) the need to manage marine resources in such a way as to encompass global to local scales; (2) recognition of the complementary nature of organizational scales between the natural and social sciences and use of appropriate natural science scales in the development of management policies; (3) the need to be aware of shifting temporal baselines and the representative nature of the data over time, for both social and natural sciences; and (4) caution regarding predictive models when humans are included. In terms of methodologies, good scale matches occur across large‐scale social and natural science models and surveys, but problems remain in small‐scale qualitative social studies and in cross‐scale studies. Cumulative case studies appear to provide the best approach, although ‘integrating up’ remains a challenge. Natural and social scientists need to work together to identify these issues of ecosystem processes and human interactions, and their appropriate scales.
Habitat selection of overwintering Calanus finmarchicus in the NE Norwegian Sea and shelf waters off Northern Norway in 2000–02
Authors: Halvorsen Elisabeth , Tande Kurt S. , Edvardsen Are , Slagstad Dag , Pedersen Ole Petter 
Published: September 2003

AbstractThe abundance and distribution of overwintering Calanus finmarchicus in the NE Norwegian Sea and shelf waters off North Norway was studied during January for 2000–02. Depth integrated distribution of C. finmarchicus CV showed aggregations with high abundances in the Lofoten Basin and southwest of Tromsøflaket for all three years. The exact location of the aggregation areas and the maximum abundances did, however, vary between the years. The concentrations southwest of Tromsøflaket were almost twofold higher in 2000 at 150 000 ind. m−2 compared to 70 000 and 90 000 ind. m−2 in 2001 and 2002, respectively. Vertical distribution of the animals was similar for the three years, with most of the CVs of the population residing in the depth interval between 700 and 1200 m. Peak abundances of 350 ind. m−3 were found at 850–1000 m west of Tromsøflaket in 2000, whereas in 2001 the maximum abundances were located in the Lofoten Basin at 700–900 m, in the order of 150 ind. m−3. In 2002, the highest concentration of animals was found west of Vesterålen between 1100 and 1200 m, with a concentration of 385 ind. m−3. The vertical and horizontal distribution of C. finmarchicus CV closely followed the hydrographic structures in the area, with the highest abundances associated with cold (<2°C), less saline (34.85–34.9) water with a density of 27.95–28. The patches of high abundance were located in confined areas along the continental shelf slope and in the Lofoten Basin, indicating that the animals may have been extracted from the highly flushed surface areas in late summer during their ontogenetic descent, and trapped in mesoscale physical features in the deep‐water masses throughout the winter. We argue that deep‐water mesoscale anticyclonic eddies, which are frequently formed along the continental slope and in the Lofoten Basin, may provide favourable retention areas for the overwintering population of C. finmarchicus. Consequently, the impact of ocean climate as well as more regional and local effects on the creation and persistence of these mesoscale features is likely to influence the Calanus abundance and advection paths in the following spring and summer.
Annual cycle of zooplankton abundance, biomass and production on the northern Gulf of Alaska shelf, October 1997 through October 2000
Authors: Coyle Kenneth O. , Pinchuk Alexei I. 
Published: September 2003

AbstractZooplankton abundance from March through October on the northern Gulf of Alaska shelf in 1998, 1999 and 2000 was dominated by calanoid copepods; the biomass was dominated by calanoids and cnidarians. Although we sampled during the 1997–1998 El Niño, marked interannual differences in the major copepod taxa were not observed. Zooplankton abundance and species composition were influenced primarily by mean water‐column salinity, secondarily by the mean temperature above the thermocline. An annual biomass peak, averaging about 0.5 g wet weight m−3, occurred in May and consisted primarily of the oceanic copepod species Neocalanus cristatus, Neocalanus plumchrus and Neocalanus flemingeri. A second biomass peak, 0.5 g wet weight m−3, was observed in August and consisted mainly of the cnidarian Aequorea spp. Copepod production, estimated from daily growth rates using temperature–body size regressions, peaked in May at about 35 mg C m−2 day−1. Initial calculations suggest an annual copepod production on the order of 6 g C m−2 year−1, probably less than 10% of the annual primary production. The apparent resilience of the zooplankton assemblage on the northern Gulf of Alaska shelf to the 1997–1998 ENSO may have been because of its large geographic separation from the faunal boundary between zooplankton communities in the California Current and North Pacific subarctic gyre.
The marine copepod, Pseudocalanus elongatus, as a mediator between climate variability and fisheries in the Central Baltic Sea
Authors: Möllmann C. , Kornilovs G. , Fetter M. , Köster F.W. , Hinrichsen H.‐H. 
Published: September 2003

Abstract Pseudocalanus elongatus is a key species in the pelagic zone of the deep basins of the Central Baltic Sea. The copepod serves as a major food organism for larval as well as for adult, pelagic planktivorous fish. Large interannual fluctuations in the standing stock of P. elongatus have been attributed to significant changes in the hydrographic environment over the last two decades. In particular, the decreasing salinity in the Baltic deep basins, a result of a change in atmospheric forcing leading to an increase in rainfall since the 1980s and of a lack of pulses of saline water intrusions from the North Sea, was found to affect reproduction and maturation of the copepod. In parallel, dramatic changes in the weight‐at‐age of herring, one of the most important commercial fishes of the Baltic Sea, have been observed since the late 1980s. Using time‐series on herring stomach contents, as well as length and weight, we provide evidence for a chain of events relating variability in climate, salinity and P. elongatus abundance to changes in diet and condition of herring in the Central Baltic Sea.
Environmental ‘loopholes’ and fish population dynamics: comparative pattern recognition with focus on El Niño effects in the Pacific
Authors: Bakun Andrew , Broad Kenneth 
Published: September 2003

AbstractA process of comparative pattern recognition is undertaken for the purpose of garnering insights into the mechanisms underlying some currently puzzling conundrums in fishery resource ecology. These include (a) out‐of‐phase oscillations between anchovies and sardines, (b) the remarkable fish productivity of the Peru–Humboldt marine ecosystem, (c) sardine population increases in the eastern Pacific during El Niños, (d) basin‐wide synchronies in large‐amplitude abundance variations, (e) characteristic spawning of large tuna species in poorly productive areas, (f) contrary trends in Pacific tropical tuna abundance during the 1970s and early 1980s.It is found that each of the items appears to become less enigmatic when the conceptual focus shifts from conventional trophodynamics to the idea that ‘loopholes’ in the fields of biological controls (i.e. of predators of early life stages), produced by poor ocean productivity or by disruptive environmental perturbations, may in fact lead to remarkable reproductive success. Implications include the following: (1) El Niño, rather than being an unmitigated disaster for Peruvian fisheries, may in the long run be a prime reason for the remarkable fishery productivity of the Peru–Humboldt large marine ecosystem. (2) Globally‐teleconnected climatic trends or shifts might produce globally‐coherent population expansions even when local environmental expressions may be quite different. (3) It may be unreasonable to expect any management methodologies to be able to keep the fish populations of highly climatically‐perturbed systems such as the Peruvian LME always at stable high levels; an alternative approach, for example, might be to take optimal advantage of the transient opportunities afforded by the high fish productivity of such inherently erratic systems.
Tidal front and the convergence of anchovy (Engraulis japonicus) eggs in the Yellow Sea
Authors: Hao Wei , Jian Su , Ruijing Wan , Lei Wang , Yi'an Lin 
Published: September 2003

AbstractAnchovy recruitment determines fish production and thus the sustainable exploitation of anchovy in the Yellow Sea. Haizhou Bay is a traditional spawning and nursery ground for anchovy. The retention of anchovy in its early life stages appears to be related to observed fronts. Cruises have confirmed that anchovy eggs are distributed in high density patches, particularly in the tidal frontal zone. Front and egg patches shift to the shallow area in the warm season. A diagnostic Hamburg Shelf Ocean Model was applied in the East China Sea and Yellow Sea to simulate the frontal circulation and particle movement, forced by monthly wind speed and measured temperatures. It was observed that the jet along the front and upwelling in the mixed side of the front play an important role in the transport of eggs. Convergence and divergence areas are frequently induced by frontal shear instability and topography potential vorticity balance. Numerical experiments show that tidal mixing and front play an important role to converge particles like eggs. When eggs are caught in the convergence zone they are aggregated into a patch. The convergence zone has good feeding condition for eggs to hatch and larvae to grow.
Modelling the vertical distribution of eggs of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus)
Authors: Boyra G. , Rueda L. , Coombs S.H. , Sundby S. , Ådlandsvik B. , Santos M. , Uriarte A. 
Published: September 2003

AbstractUnderstanding and modelling the vertical distribution of fish eggs in the water column is a major challenge for future use of underway‐continuous egg samplers as estimators of the total egg abundance. This study presents modelling of field data of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) egg vertical distribution obtained from LHPR sampling in the Bay of Biscay. Starting from Sundby's model [Deep‐Sea Res.30 (1983) 645], improvements were achieved through successive modifications concerning egg buoyancy and vertical propagation of wind‐induced turbulence. In addition, measurements of egg settling velocity and buoyancy by stages were included as inputs for the model. The best model fitting was achieved through the adoption of a gradual turbulence vertical decay model (proportional to the inverse of the water density profile), a Gaussian variability of egg density and adaptability of the egg density to the surrounding water by means of permeability of the chorion. This led to improvements over the Sundby original model. The coefficient of determination (R2) of the modelled egg abundance profiles compared with the observed ones was around 80% for both sardine and anchovy. The model described successfully the vertical distribution of eggs for waters of high surface salinity (R2 of almost 90%), but less so for waters of low surface salinity (R2 of about 70%).
Effects of ontogenetic vertical migration of zooplankton on annual primary production – using NEMURO embedded in a general circulation model
Authors: Aita Maki N. , Yamanaka Yasuhiro , Kishi Michio J. 
Published: September 2003

AbstractWe developed a global three‐dimensional physical–biological coupled model and applied it in simulations with and without ontogenetic seasonal vertical migration of large zooplankton (copepods). The annual cycle of phytoplankton behaviour is well reproduced by this model with the seasonal vertical migration of zooplankton. A comparison of the two cases shows that in the northwestern Pacific and subarctic southern ocean, primary production is higher in the case with vertical migration. In these regions, large phytoplankton (diatoms) dominate, and the presence of large zooplankton throughout the year reduces primary production by large phytoplankton (diatoms). This effect is greatest for the diatom bloom. On the other hand, for regions where small phytoplankton dominate, primary production is higher in the case without vertical migration. This is because small zooplankton are suppressed by grazing pressure from large zooplankton, reducing grazing pressure on small phytoplankton.
Recruitment, sustainable yield and possible ecological consequences of the sharp decline of the anchovy (Engraulis japonicus) stock in the Yellow Sea in the 1990s
Authors: Zhao X. , Hamre J. , Li F. , Jin X. , Tang Q. 
Published: September 2003

AbstractNatural mortality, stock–recruitment relationship and sustainable yield of the anchovy (Engraulis japonicus) stock in the Yellow Sea were estimated based on acoustic assessments of the wintering anchovy stock from 1987 to 2002. The stock‐recruitment relationship was estimated to be: R = 151.1 × SSB × e−0.299·SSB, where R is given in billion fish and SSB is in million tons. The optimum sustainable yield of anchovy was estimated at 520 000 tons for the period 1987–2002. The ecological consequences of the sharp decline of the anchovy stock observed after 1996 were examined in terms of the reduction in biomass production in the Yellow Sea ecosystem, as well as the consequences of such reduction on predator–prey interactions and species competition.
Growth rate variability of Pacific saury, Cololabis saira, larvae in the Kuroshio waters
Authors: Oozeki Yoshioki , Watanabe Yoshiro , Kurita Yutaka , Nakata Kaoru , Kitagawa Daiji 
Published: September 2003

AbstractGrowth rate time series of Pacific saury, Cololabis saira, larvae in the Kuroshio waters were constructed using a previously reported relationship between early life stage growth rates and environmental factors in winter (January to March) 1971–2000, including sea surface temperature, chlorophyll a concentration and copepod density. Pacific saury has been commercially exploited and its stock size shows large fluctuations. It spawns from autumn to spring. Growth and survival in the early life stage have been considered the major factors controlling recruitment fluctuations. The winter spawning cohort showed a fast and stable growth rate during their early stage. Ages of 40 mm juveniles (t40) calculated from growth rate estimations were stable during the 30‐yr period and showed a significant positive correlation to the Pacific Decadal Oscillation index in winter. A negative correlation between the t40 and the catch record of medium size saury (24.0–28.9 cm) was detected but was not significant. Recruitment of the winter spawning cohort is thought to be regulated not only by the duration of the vulnerable larval period but also by other biological factors, i.e. mortality after the larval stage and the abundance of predators.
Wind strength and biological productivity in upwelling systems: an idealized study
Authors: Botsford Louis W. , Lawrence Cathryn A. , Dever Edward P. , Hastings Alan , Largier John 
Published: September 2003

AbstractBiological production in wind‐driven coastal upwelling systems is of global importance. To understand better how wind speed and shelf width affect productivity, we formulated a simple model of cross‐shelf transport that included the dynamics of one potential mechanism: increasing nutrients with increasing winds, with possible loss of productivity due to off‐shelf Ekman transport. We used this model to determine how shelf productivity would depend on wind speed and shelf width using several ecosystem (Nutrient–Phytoplankton–Zooplankton, NPZ) models that reflect different trophic pathways and differences in model stability. For constant wind speeds, shelf productivity for all of the NPZ models declined beyond a certain wind speed. The shelf transit time beyond which productivity declines can be determined graphically from the time course of cumulative production in the NPZ model. Shelf width and latitude then determine the corresponding wind speed. The predicted points of decline in productivity with wind‐speed were consistent with data from local observations of higher trophic levels on the central California coast. Only shelf productivity of the NPZ model reflecting new production was dome‐shaped. Shelf productivity of models of regenerated production remained constant with wind speed at low winds. Artificial instability in NPZ models can lead to an inaccurate dependence of productivity on wind. Our model of coastal upwelling, which represents production as cross‐shelf transport of parcels containing developing NPZ models, exhibits a different dependence on wind forcing than previous models that represented upwelling production as a fully mixed shelf. The relative degree of mixing versus transport in upwelling systems is a critical factor underlying the dependence of productivity on wind.
Modelling the distribution, sustainability and diapause emergence timing of the copepod Calanus finmarchicus in the Labrador Sea
Authors: Tittensor D. P. , DeYoung B. , Tang C. L. 
Published: September 2003

AbstractIt is now recognized that Calanus finmarchicus, the dominant copepod zooplankter of the North Atlantic, has most of its biomass in the open ocean. While the Labrador Sea does contain a large population of Calanus finmarchicus, the importance of possible connections with the rest of the North Atlantic are not understood. Although there are few wintertime observations, sufficient data exist to model the role of the circulation, temperature and food supply on population dynamics. This study couples a biological model of Calanus finmarchicus with a physical oceanographic model of the Labrador Sea, using chlorophyll data derived from observations by the satellite‐borne SeaWiFS (Sea‐viewing Wide Field‐of‐view Sensor) as a proxy food supply for the numerical copepods. We produce a large‐scale, comprehensive picture of the spatial distribution of Calanus finmarchicus in the Labrador Sea, along with an exploration of the timing of diapause and an examination of population sustainability. We are able to simulate reasonably well the temporal and spatial patterns of Calanus finmarchicus in the Labrador Sea. During a year long model run, the population has a single generation over most of the Labrador Sea, with a final diapausing population about 50% the size of the initial for the parameters used in these simulations. A latitudinally dependent diapause emergence scheme with early emergence to the south of Newfoundland provides the best fit to data. A change of 0.5°C in the temperature field can cause significant changes in the population abundance in a single year, due to changes in Calanus finmarchicus growth rates.