Feeding activities of zooplankton in the Bohai Sea

The Bohai Sea was the site of the Chinese national GLOBEC programme. During the June 1997 cruises of R/V Science No.1, observations and experiments on zooplankton feeding were conducted. At five 48 h time-series stations the following observations and measurements on zooplankton were carried out: (1) diurnal vertical migration, by collecting samples at different layers every 3 h with a closing net; (2) diurnal feeding rhythms, by gut pigment analysis; and (3) ingestion rate, by both gut pigment analysis and the dilution method. A classification by body size was used to deal with the diversity of species and developmental stages of zooplankton assemblages. Samples were separated into three size groups: small (200-500 mu m), medium (500-1000 mu m) and large (> 1000 mu m). The results showed that the copepods (Calanus sinicus, Paracalanus parvus, Acartia bifilosa and Centropages mcmurrichi) performed clear diurnal vertical migrations. However, their behaviour was different at different stations. The variation in gut pigment content over the 24 h cycle showed strong diurnal feeding rhythms, particularly for the large size group. Gut pigment contents reached their daily maximum during the time from dusk to midnight (18:00-24:00). The peak value was about 10 times the minimum observed in the daytime. The in situ daily grazing rate, based on gut pigment contents and evacuation experiments, was 4.00-12.65 ng chla ind(-1) day(-1) for the small size group, 5.99-66.58 ng chla ind(-1) day(-1) for the medium size group and 31.31-237.13 ng chla ind(-1) day(-1) for the large size group. The copepods consumed only a small part (2.90-13.52%) of the phytoplankton biomass hut about 77% of the daily production. The grazing mortality rate of phytoplankton by microzooplankton (<200 mu m) measured by the dilution method ranged from 0.43 to 0.69 day(-1) The calculated daily consumption of phytoplankton biomass was 35-50%, and 85-319% of the potential production.

Viewing DVM via general behaviors of zooplankton: A way bridging the success of individual and population

In this paper, we viewed the diel vertical migration (DVM) of copepod in the context of the animal's immediate behaviors of everyday concerns and constructed an instantaneous behavioral criterion effective for DVM and non-DVM behaviors. This criterion employed the function of 'venturous revenue' (VR), which is the product of the food intake and probability of the survival, to evaluate the gains and losses of the behaviors that the copepod could trade-off. The optimal behaviors are to find the optimal habitats to maximize VR. Two types of VRs are formulated and tested by the theoretical analysis and simulations. The sensed VR, monitoring the real-time changes of trade-offs and thereby determining the optimum habitat, is validated to be the effective objective function for the optimization of the behavior; whereas, the realized VR, quantifying the actual profit obtained by an optimal copepod in the sensed-VR-determined habitat, defines the life history of a specific age cohort. The achievement of a robust copepod overwintering stock through integrating the dynamics of the constituent age cohorts subjected to the instantaneous behavioral criterion for DVM clearly exemplified a possible way bridging the immediate pursuit of an individual and the end success of the population. (c) 2005 Published by Elsevier Ltd.

Restructuring of a zooplankton community by perturbation from a wind-forced coastal jet

The impact of transient wind events on an established zooplankton community was observed during a, field survey in a, coastal region off northern Norway in May 2002. A transient wind event induced a coastal jet/filament intrusion of warm, saline water into our survey area where a semi-permanent eddy was present. There was an abrupt change in zooplankton community structure within 4-7 days of the wind event, with a change in the size structure, an increase in lower size classes less than 1 mm in equivalent spherical diameter (ESD) and a decrease in larger size classes greater than 1.5 mm in ESD. The slope of zooplankton biovolume spectra changed from -0.6 to -0.8, consistent with the size shifting towards smaller size classes. This study shows that even well established zooplankton communities are susceptible to restructuring during transient wind events, and in particular when wind forcing induces horizontal currents or filaments.

Zooplankton functional groups on the continental shelf of the yellow sea

Zooplankton plays a vital role in marine ecosystems. Variations in the zooplankton species composition, biomass, and secondary production will change the structure and function of the ecosystem. How to describe this process and make it easier to be modeled in the Yellow Sea ecosystem is the main purpose of this paper. The zooplankton functional groups approach, which is considered a good method of linking the structure of food webs and the energy flow in the ecosystems, is used to describe the main contributors of secondary produciton of the Yellow Sea ecosystem. The zooplankton can be classified into six functional groups: giant crustaceans, large copepods, small copepods, chaetognaths, medusae, and salps. The giant crustaceans, large copepods, and small copepods groups, which are the main food resources for fish, are defined depending on the size spectrum. Medusae and chaetognaths are the two gelatinous carnivorous groups, which compete with fish for food. The salps group, acting as passive filter-feeders, competes with other species feeding on phytoplankton, but their energy could not be efficiently transferred to higher trophic levels. From the viewpoint of biomass, which is the basis of the food web, and feeding activities, the contributions of each functional group to the ecosystem were evaluated; the seasonal variations, geographical distribution patterns, and species composition of each functional group were analyzed. The average zooplankton biomass was 2.1 g dry wt m(-2) in spring, to which the giant crustaceans, large copepods, and small copepods contributed 19, 44, and 26%, respectively. High biomasses of the large copepods and small copepods were distributed at the coastal waters, while the giant crustaceans were mainly located at offshore area. In summer, the mean biomass was 3.1 g dry wt m(-2), which was mostly contributed by the giant crustaceans (73%), and high biomasses of the giant crustaceans, large copepods, and small copepods were all distributed in the central part of the Yellow Sea. During autumn, the mean biomass was 1.8 g dry wt m(-2), which was similarly constituted by the giant crustaceans, large copepods, and small copepods (36, 33, and 23%, respectively), and high biomasses of the giant crustaceans and large copepods occurred in the central part of the Yellow Sea, while the small copepods were mainly located at offshore stations. The giant crustaceans and large copepods dominated the zooplankton biomass (2.9 g dry wt m(-2)) in winter, contributing respectively 57 and 27%, and they, as well as the small copepods, were all mainly located in the central part of the Yellow Sea. The chaetognaths group was mainly located in the northern part of the Yellow Sea during all seasons, but contributed less to the biomass compared with the other groups. The medusae and salps groups were distributed unevenly, with sporadic dynamics, mainly along the coastline and at the northern part of the Yellow Sea. No more than 10 species belonging to the respective functional groups dominated the zooplankton biomass and controlled the dynamics of the zooplankton community. The clear picture of the seasonal and spatial variations of each zooplankton functional group makes the complicated Yellow Sea ecosystem easier to be understood and modeled. (C) 2010 Elsevier Ltd. All rights reserved.

SOUND PROPAGATION AND SCATTERING IN BUBBLY LIQUIDS

In the ocean, natural and artificial processes generate clouds of bubbles which scatter and attenuate sound. Measurements have shown that at the individual bubble resonance frequency, sound propagation in this medium is highly attenuated and dispersive. Theory to explain this behavior exists in the literature, and is adequate away from resonance. However, due to excessive attenuation near resonance, little experimental data exists for comparison. An impedance tube was developed specifically for exploring this regime. Using the instrument, unique phase speed and attenuation measurements were made for void fractions ranging from 6.2 × 10^−5 to 2.7 × 10^−3 and bubble sizes centered around 0.62 mm in radius. Improved measurement speed, accuracy and precision is possible with the new instrument, and both instantaneous and time-averaged measurements were obtained. Behavior at resonance was observed to be sensitive to the bubble population statistics and agreed with existing theory, within the uncertainty of the bubble population parameters. Scattering from acoustically compact bubble clouds can be predicted from classical scattering theory by using an effective medium description of the bubbly fluid interior. Experimental verification was previously obtained up to the lowest resonance frequency. A novel bubble production technique has been employed to obtain unique scattering measurements with a bubbly-liquid-filled latex tube in a large indoor tank. The effective scattering model described these measurements up to three times the lowest resonance frequency of the structure.

Totality of experience: sound, music and mythology in Gus Van Sant’s “Death Quartet”

Reflecting on Gus Van Sant’s films Gerry (2003) Elephant (2004) and Last Days (2005), the director’s long-term sound-designer Leslie Shatz observed that “You have to get into the totality of the experience and not just the dialogue”. Shatz’s comment expresses something fundamental about the experimental approach to cinema and to soundscapes undertaken by Van Sant in these three films, unofficially known as the “Death Trilogy”. This thesis contends that Van Sant makes deliberate aesthetic choices which do indicate a distinctly “auteurist” leaning. However, I also argue that intertextual elements, prior knowledge, and audience participation in meaningmaking enhance the experience of, and reveal the nuances in, the soundtracks themselves. This thesis aims to contribute to a growing body of work within filmmusic scholarship concerned with resisting a traditional bias in the field: that film music should be understood as a means of characterisation and as emotional signifier. The films of the “Death Quartet”, which includes Paranoid Park (2007), I believe, offer fertile ground on which to explore these new approaches. It is my contention that these films deconstruct the traditional approach to soundtracking and the relationship between soundtrack and character, and that only an approach sensitive to the aesthetic and philosophical functions of music and sound can adequately acknowledge their unique cinematic qualities.