Effect of vertical mixing on the vertical distribution of copepods in coastal waters

The vertical distribution of copepod adult stages and naupliihad been studied in a coastal water before and during homogenizationof the water column due to wind. When the water column was stratified,the vertical distribution of the zooplankton was also stratified,as is generally described in the literature. During homogenizationof the water column, different patterns of vertical distributionwere observed. The less active nauplius stage was evenly distributed,even though adult stages always exhibited a stratified distribution.Oithona similis and Microsetclla norvegica exhibited the samedistribution in stratified and unstratified water columns. Temoralongicomis and Pseudocalanus sp. were deeply distributed ina less turbulent area. The causes of these changes are discussed.     

Analysis of the self-shading effect on algal vertical distribution in natural waters

Self-shading of light by algae growing in a column of water plays an important role in the dynamics of algal blooms. Thus without self-shading the algal concentration would increase more rapidly, making the nutrient limitation too strong. Apart from the practical importance of self-shading, its inherent nonlinearity in the growth dynamics leads to an interesting mathematical problem, which warrants detailed analytical investigation. Our mathematical model for the self-shading effect includes vertical diffusion, algal settling, gross production, and collective losses of algae. Steady-state solutions of the model equation are investigated in detail by the phase plane method, and their stability examined. Finally we discuss the vertical profile of algal concentration.Contribution No. 291 of the Marine Sciences Research Center     

A method of studying the vertical distribution of the bottom fauna in shallow waters

Summary A method is described of sampling the vertical distribution of the bottom fauna of shallow water using liquid oxygen as a freezing agent.

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Zusammenfassung Es wird eine Methode beschrieben zum Probentnahme der vertikalen Verteilung der Bodenfauna untiefen Wassers, mit Benutzung von flüssigem Sauerstoff als Frierungsmittel.

     

Phaeodarian Radiolaria from the Upper Cretaceous beds of central Japan

Upper Cretaceous Phaeodarea (Radiolaria) were recovered from the Shoya Formation, which crops out 100 km northwest of Tokyo, central Japan. The Shoya Formation consists of about 600 m-thick marine sedimentary rocks, represented by alternating beds of sandstone and mudstone, which are overlain by about 10 m of Phaeodarian-bearing siliceous mudstone. The latter is assigned to the Upper Cretaceous (late Campanian to early Maastrichtian) based on the associated Polycystine Radiolarian fossils. In spite of the poor general preservation of nearly all Phaeodarian specimens as recrystallized quartz infillings, three new Phaeodarian species, Challengeranium cretaceum, Challengeron paleotriangulum, and Medusetta fossilis, were identified on the basis of their shape and ornamentation. Our finding, together with two other very recent reports of fossil Phaeodarians clearly document that the origin of Phaeodarian Radiolarians can be extended back to at least the Upper Cretaceous.     

Planktonic sarcodines (Acantharia, Radiolaria, Foraminifera) in surface waters near Bermuda: abundance, biomass and vertical flux

The abundance biomass and vertical flux of large planktonicForaminifera. Acanthana and polycystine Radiolaria were determinedin surface waters of the Sargasso Sea southeast of Bermuda.On average, Acanthana were the most abundant group (     

The morphometric variation of Actinomma boreale (Radiolaria) in Atlantic boreal waters

A morphometric study on the polycystine radiolarian species Actinomma boreale (Cleve) from ten trigger weight core-tops from the Norwegian-Iceland Seas, three piston cores taken offshore western Norway and three surface sediment samples from Lygrepollen, Sogndalsfjord and Høyangsfjord (western Norwegian fjords) shows a variation in morphology that groups A. boreale into three distinct clusters, interpreted to be related to different oceanographic settings. The largest specimens of A. boreale are found in the western Norwegian fjords, the smallest in the Iceland Sea, giving an apparent positive correlation with temperature.Down core studies in piston cores from the Norwegian Sea demonstrate a considerable size variation of the cortical shell of A. boreale. In the eastern Norwegian Sea, the climatically cold Younger Dryas had a population of A. boreale that was characterized by large cortical shells, while the climatically warm Holocene population was dominated by small sized cortical shells, showing a negative correlation with temperature. We suggest that the large sized conical shell population of A. boreale in the Younger Dryas is not reflecting precisely the sea-surface water temperature. Another factor must play the dominant role here, probably nutrients.     

Winter spatial distribution of fish larvae assemblages relative to the hydrography of the waters surrounding Taiwan

The aim of this study was to investigate the species composition and distribution of fish larvae in relation to hydrographic conditions in the waters surrounding Taiwan Island (TI) in February 2003. In total, 242 kinds of fish larvae belonging to 127 genera and 75 families were recognized. Among these, 109 taxa were identified to the family or genus level, others to the species level. The 12 predominant types, which constituted 71% of the total fish larvae, were Engraulis japonica, Scomber sp., Diaphus spp., Benthosema pterotum, Carangoides ferdau, Embolichthys mitsukurii, Maurolicus sp., unidentified Myctophidae, Gonostoma gracile, Trichiurus lepturus, unidentified Gobiidae, and Myctophum asperum. The distribution of fish larvae showed a clear association with water masses around TI, with higher abundances and lower species richness northwest of TI where the China Coastal Current prevails, and lower abundances and higher species diversity east of TI where the Kuroshio Current dominates. Cluster analysis distinguished three station groups and four species groups, and the distribution patterns of fish larvae also corresponded to hydrographic conditions. The total abundances of fish larvae and eight of the 12 predominant taxa showed significant and positive correlations with zooplankton abundance, which suggests that food source might be a key factor determining the abundance and distribution of fish larvae during the winter.     

Feeding rhythm and vertical migration of the euphausiid Euphausia pacifica in coastal waters of north-eastern Japan during fall

We investigated the feeding rhythm and diel vertical migrationof Euphausia pacifica in coastal waters of north-eastern Japanin September 2000. The euphausiids arrived at the surface earlyin the night and sank just after satiation. Gut pigment contentsand stomach fullness were higher in the food-rich surface layerat night than in the food-poor deep layer during the day. Feedingactivity of E. pacifica during daytime was low even if foodorganisms were abundant in the ambient water in the top 50 m.Therefore, the feeding rhythm of E. pacifica is explained bydecreased feeding activity during the day rather than by reducedfood availability.     

Seasonal occurrence and vertical distribution of appendicularians in Toyama Bay, southern Japan Sea

To investigate seasonal variation in the community structureof appendicularians, vertical hauls (0–500 m) with a Norpacnet were made at an offshore station in Toyama Bay at intervalsof 2–4 weeks from February 1990 to January 1991. Additionalsamples were collected with MTD nets at 12–17 differentdepth layers between the surface and a depth of 600–700m at the same position in June, September and December 1986,and March 1992, to examine the vertical distribution of appendicularians.Twenty-one species (including two unidentified species) belongingto five genera were found, and the dominant species were dividedinto three groups by their occurrence period. Oikopleura longicauda,Fritillaria borealis f. typica and F. borealis f. sargassi occurredthroughout most of the year. Fritillaria pellucida, O. fusiformisand O. rufescens were found in summer and autumn. Oikopleuradioica was found in spring and winter. Oikopleura longicaudawas overwhelmingly the most abundant species throughout theyear. This species was always distributed in the upper 100 mdepth, with a peak at a depth of 0–50 m that correspondedto the peak of chlorophyll a concentration during the day andnight in all seasons. The day–night vertical distributionpatterns of F. borealis f. typica, F. pellucida, O. fusiformisand O. rufescens were similar to that of O. longicauda. Seasonalvariations in abundance of appendicularians are considered tobe the result of biological factors rather than physical factorssuch as temperature and salinity. In particular, O. dioica seemsto be affected by food availability.     

The vertical distribution of Culicoides impunctatus larvae

Abstract. Soil cores were taken from three transects, representing the vegetation typical of much of the west coast and Highlands of Scotland, in an attempt to investigate the distribution of Culicoides impunctatus larvae. Sampling of soil cores was carried out at four periods throughout the day (00.00,05.00,12.00 and 17.00 hours). Each core sample was sliced into sections, 1 cm deep and Culicoides impunctatus larval numbers in the first 8 cm of the soil core were investigated, using a sugar-flotation technique. At all sampling times, approximately 50% of the total numbers of larvae recovered were from the first 2cm of the soil. During the daylight sampling periods (05.00, 12.00 and 17.00 hours), there was a small but significant migration of larvae into the deeper layers (2–5 cm). The results are discussed in relation to those for other species from previous studies, and also to their application in larval collection for colonization techniques and in localized Culicoides control.     

Horizontal and vertical distribution and demography of euphausiids in the Ross Sea and its adjacent waters in 2004/2005

The horizontal and vertical distribution and population structure of euphausiids in the Ross Sea and its adjacent waters were investigated during the summers of 2004/2005 using stratified towed samples. Nine species of euphausiids occurred in the survey area. Among them, Euphausia triacantha was dominant in biomass north of the southern boundary of the Antarctic circumpolar current (SB). Thysanoessa spp. was widely distributed north of the continental slope, while E. superba was distributed from the SB to the slope, where it showed the highest biomass. Juvenile E. superba was distributed offshore near the SB and remained at the surface, but gravid females were dominant in the slope and mainly occurred in the middle layers (400–600 m). Adult and juvenile E. crystallorophias were found at 200–300 m in the colder water of the continental shelf. In general, the peak biomass of euphausiids was found in the mid layers of the Ross Sea area. The life span and the number of spawns for major species are also discussed.     

The distribution and some biological features of Stichaeus grigorjewi (Stichaeidae) in the waters of northern Primorye (The Sea of Japan)

Stichaeus grigorjewi is a common species, but in the waters of northern Primorye it is comparatively rare. It occurs at depths down to 465 m for the greater part of the year, except for the spawning period, staying in deep-water masses with relatively stable temperature conditions. The widest bathymetric distribution of S. grigorjewi is observed from spring-early summer. After the completition of spawning, it shifts to depths larger than 100 m and winters in the upper section of the continental slope. During each season maximum concentrations of S. grigorjewi along the coasts of Primorye are observed in water from Povorotnyi Cape to the Olga Gulf. Males and females of this species have close rates of growth and reach an age of not less than 12+ years. Most individuals of S. grigorjewi in catches had a length of 37 to 44 cm and fed mainly on fish.     

The vertical distribution of phytoplankton in stratified water columns

What determines the vertical distribution of phytoplankton in different aquatic environments remains an open question. To address this question, we develop a model to explore how phytoplankton respond through growth and movement to opposing resource gradients and different mixing conditions. We assume stratification creates a well-mixed surface layer on top of a poorly mixed deep layer and nutrients are supplied from multiple depth-dependent sources. Intraspecific competition leads to a unique strategic equilibrium for phytoplankton, which allows us to classify the distinct vertical distributions that can exist. Biomass can occur as a benthic layer (BL), a deep chlorophyll maximum (DCM), or in the mixed layer (ML), or as a combination of BL+ML or DCM+ML. The ML biomass can be limited by nutrients, light, or both. We predict how the vertical distribution, relative resource limitation, and biomass of phytoplankton will change across environmental gradients. We parameterized our model to represent potentially light and phosphorus limited freshwater lakes, but the model is applicable to a broad range of vertically stratified systems. Increasing nutrient input from the sediments or to the mixed layer increases light limitation, shifts phytoplankton towards the surface, and increases total biomass. Increasing background light attenuation increases light limitation, shifts the phytoplankton towards the surface, and generally decreases total biomass. Increasing mixed layer depth increases, decreases, or has no effect on light limitation and total biomass. Our model is able to replicate the diverse vertical distributions observed in nature and explain what underlying mechanisms drive these distributions.     

The annual cycle of Mesodinium rubrum in the waters surrounding the Isles of Shoals, Gulf of Maine

Mesodinium rubrum was collected in Kemmerer bottles, fixed inBouin's solution and protargol stained. Cell volume showed aseasonal change of over an order of magnitude, being largest(3.25x10⁴ µm³) in the early spring and smallest in thesummer. Cell abundance was highest in the spring and lowestin the summer. Biomass followed a similar trend ranging from{small tilde}1 to 147 J m^–3 Production, estimated by amultiple regression that incorporated ambient temperature andcell volume, was 2.5 kJ m^–3 day^–1 This is {smalltilde}0.3% of the primary production.     

The distribution ofMyriophyllum spicatum L. in the inland waters of Egypt

Myriophyllum spicatum has been discovered in the Nile valley during the past decade. The rapid colonization seems to be influenced by changes in the Nile water regime after the building of the High Dam at Aswan.     

The distribution of phytoplankton in some Central East African waters

Summary Observations of the distribution of phytoplankton were made in Pilkington Bay, Lake Victoria and in Lake Kyoga. For Pilkington Bay, series of samples were taken along an east-west line in the north-west corner of the bay and along a north-south line through the mouth of the bay. For Lake Kyoga, the main series of samples was taken from the north-east arm to the point of inflow of the Victoria Nile.Counts of algae were made by the sedimentation technique and it was found that for Pilkington Bay Melosira was the dominant genus during the period of the investigation. For the north-east arm of Lake Kyoga the dominant alga in mid-August was Lyngbya limnetica.At times, marked changes not only in density of phytoplankton but also in vertical distribution were observed from station to station in Pilkington Bay.During May an increase of Melosira occurred in the north-west corner of Pilkington Bay and this increase is as likely to have been due to water movements as to growth.Water movements have an important effect on phytoplankton distribution and it is possible that surface water movements bring about inoculation of relatively dense concentrations of phytoplankton, especially Melosira, into the Buvuma Channel from Pilkington Bay.The contribution of the north-east arm of Lake Kyoga to the Victoria Nile system was found to be markedly different chemically and biologically from that of Lake Victoria.A number of new records of algae from Lake Kyoga are listed.

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Résumé Des recherches sur la distribution du phytoplancton furent poursuivies dans la baie de Pilkington, dans le lac Victoria et dans le lac Kyoga. A la baie de Pilkington, des séries d'échantillons furent prélevées sur une ligne allant de l'est à l'ouest et située dans la partie nord-ouest de la baie, ainsi que sur une ligne traversant du nord au sud l'entrée de la baie. Au lac Kyoga, la principale série d'échantillons fut prélevée à partir de sa pointe nord-est jusqu'à l'arrivée des eaux de la branche mère du Nil.Le dénombrement des algues fut fait selon le procédé de la sédimentation et les résultats de l'enquête indiquent que, dans la baie de Pilkington, Melosira était le genre le plus répandu pendant la durée des recherches. Quant à la pointe nord-est du lac Kyoga, l'algue la plus répandue, à la mi-août, était Lyngbya limnetica.A certains moments, des variations marquèes, non seulement dans la densité du phytoplancton mais encore dans sa distribution verticale, furent constatées de divers postes d'observation sur la baie de Pilkington.Pendant le mois de mai, il se produisit une augmentation de la quantité de Melosira dans la partie nord-ouest de la baie de Pilkington, augmentation qui semble provenir des mouvements de l'eau ainsi que de la croissance.Le mouvement de l'eau exerce une influence importante sur la distribution du phytoplancton et il est possible que les mouvements de surface de l'eau produisent l'augmentation dans la canal de Buvuma de concentrations assez denses de phytoplancton, de Melosira surtout, provenant de la baie de Pilkington.L'apport de la pointe nord-est du lac Kyoga au réseau de la branche mère du Nil se révéla de composition chimique et biologique sensiblement differente de celle du lac Victoria.Un certain nombre d'observations nouvelles des algues du lac Kyoga ont été notées.

     

The distribution of major biochemical components in the waters of the Kuril Islands

In this paper, data are presented on the distribution of dissolved and particulate carbohydrates, proteins, lipids, and nucleic acids (NAs) in the waters of the Kuril Islands on both the Sea of Okhotsk and Pacific Ocean sides. By analyzing discrepancies in the absolute and relative concentrations of these substances, it is revealed that the waters of the Sea of Okhotsk have a strong bioproductivity. Changes in the absolute and relative conventrations of the major biochemical components of dissolved organic matter (DOM) and particulate organic matter (POM) are shown to result from the biological activity of auto- and heterotrophs of shelf and deep-sea ecosystems. Carbohydrates and proteins prove to be the major biochemical components of DOM and POM, respectively. Given high primary productivity, the carbohydrate content in POM is comparable to that of protein. In the southern Kuril area, the high concentration of dissolved and particulate NAs (which exceeds that of dissolved protein) and the high content of dissolved lipids are both strongly associated with local fish and zooplankton distribution. In the shelf and pelagic waters, biological factors dominate the horizontal and vertical distribution patterns of the major biochemical components of DOM and POM. The hydrological regime only affects these patterns in the straits of the Kuril Islands. For the first time, the biochemical composition of DOM and POM in the sea surface microlayer (SML) is characterized. In this microlayer, the concentrations of major biochemical components of DOM and POM are, to a great extent, higher than in the underlying layer.     

The distribution of the crayfish, Austropotamobius pallipes, in British waters

SUMMARY. The distribution of Austropotamobius pallipes , the only freshwater crayfish indigenous to the British Isles, is examined using over 300 records collected since 1970. The majority of records are for England where crayfish are found in areas associated with base-rich easily weathered substrata. Waters containing crayfish tend to be in the pH range 7–9, with calcium levels above 5 mg l⁻¹. Crayfish are found in a wide variety of habitats ranging from deep water-filled quarries with a soft substratum to shallow fast-flowing streams.