Effect of temporal and geographical factors on fatty acid composition of M. galloprovincialis from the Adriatic sea

Soft body tissue and gill and mantle microsomal membranes of Mytilus galloprovincialis, were analyzed to assess geographical and temporal effects on fatty acid distribution with special focus on n-3 polyunsaturated fatty acid (PUFA) content. Mussels and plankton samples were collected in April and in October from three locations of the North Adriatic Sea. Plankton fatty acid composition apparently depended both on the sampling site and time and differences referable to temporal features prevailed on the geographical ones. Accordingly, also mussel fatty acid composition appeared to be more effectively modulated by sampling time rather than by sampling location. Membrane fatty acids showed high homeostatic capabilities to reduce effects of exogenous input on cellular organization. Selective capabilities apparently enable mussels to modulate their fatty acid composition combining plankton input, environmental effects on lipid metabolism and physiological requirements. The constantly higher n-3/n-6 ratio in April than in October, shared by fatty acids of plankton, soft tissues and microsomal membranes, confirms the influence of temporal factors in fatty acid modulation. On these bases, late spring is suggested to be the more suitable period for collecting mussels destined for healthy diet of humans or other animals.     

Role of two toxin-producing plankton and their effect on phytoplankton-zooplankton system--a mathematical study supported by experimental findings

Plankton is the basis of the entire aquatic food chain. Phytoplankton, in particular, occupies the first trophic level. Plankton performs services for the Earth: it serves as food for marine life, gives off oxygen and also absorbs half of the carbon dioxide from the Earth's atmosphere. The dynamics of a rapid (or massive) increase or decrease of plankton populations is an important subject in marine plankton ecology and generally termed as a 'bloom'. Harmful algal blooms (HABs) have adverse effects on human health, fishery, tourism, and the environment. In recent years, considerable scientific attention has been given to HABs. Toxic substances released by harmful plankton play an important role in this context. In this paper, a mathematical model consisting of two harmful phytoplankton and zooplankton system will be discussed. The analytical findings will be verified through our experimental observations which were carried out on the eastern part of Bay of Bengal for the last three years.     

Notes on the distribution of phytoplankton in some Kenya waters

The distribution of the major plankton algae in a number of Kenya waters is described. The lakes and dams are shown to fall into ecological groups related to figures for the pH, conductivity and alkalinity of their waters and characterised by the dominance of certain types of alga. The composition of the phytoplankton collected at approximately monthly intervals from Sasumua and Ruiru reservoirs is described. Plankton periodicity is demonstrated for both waters and is shown to be related to rainfall. The periodicity of plankton in Lake Naivasha is noted.     

Primary production and biovolume of various phototrophic plankton size fractions in three southeastern United States reservoirs

Plankton size classes of <3 mum consisting largely of unicellular cyanobacteria accounted for 15 to 40% of the total primary production and generally represented <5% of the total phototrophic plankton biovolume in three South Carolina reservoirs.     

微塑料污染对浮游生物影响研究进展

微塑料作为一种新型的环境污染物,大量存在于水环境中,给水生生物带来了极大的危害。浮游生物是水生食物链的基础,是水生生态系统物质循环和能量流动的重要环节;同时,浮游生物也是对各种环境污染物最敏感的类群。了解微塑料对浮游生物的影响是评价其生态风险的重要依据。本文介绍了环境中微塑料来源、特征及水生态系统微塑料污染现状,阐述了微塑料对水生生物的直接和间接危害,并重点聚焦于浮游植物和浮游动物,从个体、种群和群落的层次详细总结了微塑料的影响及其作用机制。最后,本文指出当前针对浮游生物微观基因和蛋白质组学,以及宏观种群和群落响应等方面的研究还非常缺乏,为今后开展微塑料危害研究提供参考。     

Plankton blooms induced by turbulent flows

Plankton play an important role in the ecology of the ocean and the climate because of their participation in the global carbon cycle at the base of the food chain. However, damaging plankton blooms can sometimes occur and are initially characterized by sudden transient increases in the phytoplankton population. They are thought to be driven by several effects, such as seasonal variations in temperature and salinity, and nutrient mixing. Furthermore, phytoplankton and zooplankton have different buoyancy properties, leading to a differential response in turbulent environments. In this paper, we investigate this effect in a model of advected plankton dynamics. We find that, over a range of parameter values, flows of marine species subjected to inertial/viscous forces naturally lead to patchiness and, in turn, periodically sustained plankton blooms.     

Plankton ecology in Long Pond,St. John's,Newfoundland: A polluted pond characterized by a high flushing rate

Plankton was studied seasonally and quantitatively in Long Pond, St. John's, Newfoundland. This pond receives both rural and urban runoff and is characterized by a high flushing rate. A comparison is made with Clarkes Pond, Hogans Pond and Bauline Long Pond. Long Pond phytoplankton was characterized by nannoplankton (particularly flagellated forms). The most important zooplankters were Bosmina coregoni and Daphnia catawba. Aspects of plankton ecology are discussed in relation to eutrophication and water renewal.     

Mesozooplankton assemblage and first record of Paracartia grani Sars G.O., 1904 (Copepoda: Calanoida) in the Western harbour of Genova (Ligurian Sea).

Harbours are characterized by high pollutant charge and by the occurrence of well adapted and resistant species. This paper reports the results of an annual plankton survey (May 1997-June 1998) carried out in the western harbour of Genova (Ligurian Sea) and in its mouth. Plankton samples were collected by horizontal trawls using a WP2 net. Copepods were the bulk of plankton in almost all samples. Eight copepod species were recognized: Paracalanus parvus and Acartia clausi were the most abundant. The first record of Paracartia grani in the harbour of Genova is here reported; this species, which is known to occur in polluted harbour waters of the Mediterranean Sea and was found in semi-confined Mediterranean and Atlantic coastal areas, was dominant during October 1997. Also Clausocalanus spp., Centropages typicus, Oithona helgolandica, Oithona nana, Farranula spp., Eurytemora spp., Isias clavipes and Lucicutia spp. were frequently sampled. Among other zooplankters, cladocerans, ostracods and tunicates occurred frequently, while cnidarians, mysids and chaetognaths showed low densities. These results show the occurrence of a well defined harbour plankton and point out the differences between harbour and neritic plankton of the Gulf of Genova.     

The role of higher predation in plankton population models

Zooplankton mortality in plankton population models is oftenrepresented by the so-called closure term. Recently, much attentionhas been paid to the choice of functional form used for theclosure term, primarily due to the influential paper by Steeleand Henderson (J. Plankton Res., 14, 157–172, 1992). Herewe reveal an inconsistency in the normalization of Steele andHenderson's models, and show that unforced short-term oscillations(limit cycles) can occur when a quadratic closure term is used.Furthermore, we contradict the hypothesis regarding the relationshipbetween nutrient steady-state values and the choice of closureterm: using the seven-component plankton model of Fasham (TheGlobal Carbon Cycle, Heimann,M. (ed.), pp. 457–504, 1993)with four alternative closure terms, we find the nutrient valueto depend more upon the choice of parameter values than on thechoice of closure term. However, our results agree with andstrengthen the general conclusion of Steele and Henderson'swork: that the choice of closure term can strongly influencethe dynamics of models.     

广州抽水蓄能电站蓄水库蓄水初期浮游生物调查

对我国首座核电站配套工程的抽水蓄能电站水库蓄水初期的浮游生物进行了调查。蓄水水库由上下两水库组成。两水库的浮游生物种类组成显著不同。上水库浮游植物共记录到３０种（属）,浮游动物１２种（属）;下水库浮游植物１９种（属）;浮游动物２５种（属）。上下两水库浮游生物数量均较贫乏,表明浮游生物群落尚处于初期发育阶段,但在局部浅水处已出现小规模的蓝藻水花,认为是水库蓄水初期必然的结果     

The Diatom Genus Tabellaria: II. Taxonomy and Morphology of the Plankton Varieties

Plankton samples of Tabellaria from all the lakes of the EnglishLake District have been examined and evidence of morphologicallydistinct populations has been found in samples from (a) a singlelake at one time, (b) different lakes, and (c) a single lakeat different times. Clone cultures have been used to study thenature of these differences. Fifteen characters have been foundto show quantitative or qualitative variation in plankton populationsof Tabellaria, and the morphological diversity of differentpopulations is largely due to different combinations of thesecharacters. All known plankton populations of Tabellaria arereferred to the species T. flocculosa.     

Zooplankton biomass variation in relation to climatic conditions in the Barents Sea

Over the last two decades, there have been large changes in the zooplankton biomass in the Barents Sea. These biomass variations are mainly attributed to predation pressure and environmental factors (e.g. advective transport). When stock size of capelin (Mallotus villosus), a major planktivorous fish in the Barents Sea ecosystem, was quite low as in 1986 and 1994, the zooplankton biomass showed marked increase. However, the increase in the zooplankton biomass occurred in different water masses during 1986 and 1994. In 1986, a climatically cold year, the plankton biomass was highest in the Arctic waters of the northeastern Barents Sea. This is probably due to the increase in larger Arctic amphipod species, such as Themisto libellula. In 1994, a climatically warm year, the zooplankton biomass was high in the Atlantic waters of the southwestern Barents Sea. The large increase in zooplankton biomass in the Atlantic waters in 1994 was presumably due to the higher inflow of advected organisms, e.g. Calanus spp., as well as high temperatures, which may lead to high growth rates of zooplankton. Throughout the studied region, the plankton biomass in the "cold year" of 1986 was generally much lower than in the "warm year" of 1994.     

Climate,plankton and cod

While a few North Atlantic cod stocks are stable, none have increased and many have declined in recent years. Although overfishing is the main cause of most observed declines, this study shows that in some regions, climate by its influence on plankton may exert a strong control on cod stocks, complicating the management of this species that often assumes a constant carrying capacity. First, we investigate the likely drivers of changes in the cod stock in the North Sea by evaluating the potential relationships between climate, plankton and cod. We do this by deriving a Plankton Index that reflects the quality and quantity of plankton food available for larval cod. We show that this Plankton Index explains 46.24% of the total variance in cod recruitment and 68.89% of the variance in total cod biomass. Because the effects of climate act predominantly through plankton during the larval stage of cod development, our results indicate a pronounced sensitivity of cod stocks to climate at the warmer, southern edge of their distribution, for example in the North Sea. Our analyses also reveal for the first time, that at a large basin scale, the abundance of Calanus finmarchicus is associated with a high probability of cod occurrence, whereas the genus Pseudocalanus appears less important. Ecosystem‐based fisheries management (EBFM) generally considers the effect of fishing on the ecosystem and not the effect of climate‐induced changes in the ecosystem state for the living resources. These results suggest that EBFM must consider the position of a stock within its ecological niche, the direct effects of climate and the influence of climate on the trophodynamics of the ecosystem.     

Influence of Environmental Heterogeneity on the Structure of Testate Amoebae (Protozoa,Rhizopoda) Assemblages in the Plankton of the Upper Paraná River Floodplain,Brazil

In freshwater environments, testate amoebae are usually found associated with macrophytes and sediments and many studies have suggested that their occurrence in plankton samples is accidental. This implies that predictable patterns detected in planktonic assemblages should not be observed in testate amoebae assemblages. This hypothesis was tested in this study. Plankton samples were collected from different environments in the Upper Paraná River floodplain. Results show that patterns in species composition and abundance of testate amoebae are predictable, and that dominant species tend to present characteristic shell morphology in hydrologically different environments. We suggest that testate amoebae must be routinely included in plankton ecology studies, at least in floodplain environments.     

Tauchbeobachtungen an Plankton und an Echostreuschichten

Zusammenfassung 1. Das Tauchen als Methode zur Untersuchung von Plankton und Echostreuschichten wird durch vier Beispiele erläutert: (a) Visuelle Beobachtungen an Wasserschichtungen und Grenzschichten durch Schwimmtaucher. (b) Untersuchung von Echostreuschichten durch Freitaucher, wobei sich ergab, daß angesammeltes biogenes Material in den untersuchten Sprung- beziehungsweise Streuschichten die Schallreflektion nicht beeinflußt. (c) Beobachtung von Großplankton und Feststellung von Planktonund Sestonkonzentrationen beim Tauchen mit dem Bathyscaph. (d) Untersuchung der Tiefenstreuschicht (deep scattering layer) durch Beobachtung der Vertikalwanderung bestimmter Arten des Großplanktons mit den Tauchbooten Bathyscaph und Soucoupe Plongeante. Physonectide Siphonophoren und Myctophiden standen in deutlicher Beziehung zur Tiefenstreuschicht und wurden als Echogeber erkannt.2. Die Möglichkeiten, von Tauchbooten aus quantitative und qualitative Proben von Plankton und auch vom Benthos zu nehmen, sind zur Zeit noch unzureichend. Die Entwicklung entsprechender Geräte für den wahlweisen und mehrfachen Einsatz bei demselben Tauchgang wird empfohlen.

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Diving observations on plankton and on scattering layers

Diving techniques are employed as a research tool in plankton investigations carried out in shallow water of the western Baltic Sea. Observations and samplings were made by skin divers on scattering layers corresponding to the discontinuity layers. Biogene materials, sometimes concentrated at the thermocline, are not responsible for this special kind of scattering, but rather discontinuity of salinity and temperature (Lenz 1965). For observations in deep water the use of undersea vehicles is recommended. From the Bathyscaph and the diving saucer, single plankton organisms and plankton concentrations were observed (e. g.Bernard 1958); investigations on the deep scattering layer have shown physonectid siphonophores and myctophids to be scatterers (Barham 1966). The equipment for sampling plankton and benthos from undersea vehicles is poorly developed. We need urgently gear for quantitative and qualitative sampling and for manifold use during single dives, i. e., multiple sampling gear and magazins for storage of samples.

     

Nitrogen and phosphorus in plankton

Summary The total nitrogen and phosphorus content in the plankton of Porto Novo water has been investigated. The total nitrogen content varied from 0.28% to 11.70% depending upon the organisms studied. In the same organism or same group of organisms the peak values were noted during the peak season of that plankton. The phosphorus content in the different planktonic organisms varied from 0.0620% to 0.8025% dry weight. Here also the peak values coincided with a peak population of the organism. During a rich diatom period, the phosphorus content in both water (as phosphate) and the diatoms showed a significant rise. However, with a peak zooplankton season, the phosphate in the water did not show any increase.

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Sommario La quantita di nitrogene e di fosforo contenuta nel Plankton delle acque di Poroto Nuovo è stata studiata.La quantità di nitrogeno varia dal 0.28% al 11.70% a seconda degli organismi studiati. Nello stesso organismo di uno stesso gruppo — i valori massimi furono notati durante la stagione alta di quel Plankton.Il fosforo contenuto nei differenti organismi del plankton varia dal 0.0620% el 0.8025% a secco. Anche qui i massimi valori coincidono colla massima concentrazione degli organismi.Durante un periodo ottimale di diatome, il fosforo contenuto sia nell, acque (come fosfato) e nei diatome, mostrava un significativo aumento. Viceversa con la punta massima del zooplankton, il fosfato nell'acqua non rivelava nessum aumento.

     

Lifeform indicators reveal large‐scale shifts in plankton across the North‐West European shelf

Increasing direct human pressures on the marine environment, coupled with climate‐driven changes, is a concern to marine ecosystems globally. This requires the development and monitoring of ecosystem indicators for effective management and adaptation planning. Plankton lifeforms (broad functional groups) are sensitive indicators of marine environmental change and can provide a simplified view of plankton biodiversity, building an understanding of change in lower trophic levels. Here, we visualize regional‐scale multi‐decadal trends in six key plankton lifeforms as well as their correlative relationships with sea surface temperature (SST). For the first time, we collate trends across multiple disparate surveys, comparing the spatially and temporally extensive Continuous Plankton Recorder (CPR) survey (offshore) with multiple long‐term fixed station‐based time‐series (inshore) from around the UK coastline. These analyses of plankton lifeforms showed profound long‐term changes, which were coherent across large spatial scales. For example, ‘diatom’ and ‘meroplankton’ lifeforms showed strong alignment between surveys and coherent regional‐scale trends, with the 1998–2017 decadal average abundance of meroplankton being 2.3 times that of 1958–1967 for CPR samples in the North Sea. This major, shelf‐wide increase in meroplankton correlated with increasing SSTs, and contrasted with a general decrease in holoplankton (dominated by small copepods), indicating a changing balance of benthic and pelagic fauna. Likewise, inshore‐offshore gradients in dinoflagellate trends, with contemporary increases inshore contrasting with multi‐decadal decreases offshore (approx. 75% lower decadal mean abundance), urgently require the identification of causal mechanisms. Our lifeform approach allows the collation of many different data types and time‐series across the NW European shelf, providing a crucial evidence base for informing ecosystem‐based management, and the development of regional adaptation plans.     

嘉陵江浮游生物群落结构研究

为揭示嘉陵江梯级水库浮游生物群落结构特征,按枯水期和丰水期对嘉陵江12个梯级水库24个样点进行浮游生物的野外采集,分析其群落结构的物种组成,并采用Shannon-wiener指数、Margalef指数和Pielou均匀度指数进行分析.结果表明:嘉陵江四川段浮游植物共8门42科95属171种,浮游动物的组成共有4纲9目21科30属62种;浮游动物优势种类有21种.浮游生物评价结果表明梯级库区水质处于中度污染状态.     

Community photosynthesis and respiration in experimental streams

Changes in relative contribution to total stream photosynthetic and respiratory rates by various community components of an open channel stream were estimated. Rates of photosynthetic production of plankton, benthos and macrophytes (with associated epiphytes) were followed through the growing season and compared with total estimates from a diurnal oxygen technique. Photosynthetic production by macrophytes was extremely high early in the growing season; but later declined and heterotrophic processes became predominant. In contrast, benthos production was initially low but became the primary source of photosynthesis later in the season. Plankton contributed little to stream photosynthesis and respiration.