Cycling of organic nitrogen in marine plankton communities studied in enclosed water columns

Concentrations of fluorescamine-positive substances (primary amines) and turnover rates of L-leucine pools were measured concurrently in seawater samples taken from 1300 m³ plastic enclosures moored in Saanich Inlet, British Columbia, Canada. Concentration and turnover rates of dissolved free amino acids were calculated and then used to determine the instantaneous flux of dissolved free amino acids, which ranged from 0.09 to 2.42 M d^-1 (i.e.,5 to 145 gC l^-1 d^-1). This flux was highest in the euphotic zone, and was related to net primary production but not to the type of dominant primary producer. Comparison of the flux to changes in the concentration of ammonia in deep water suggested that amino acid degradation accounted for 60% of the flux into the ammonia pool. For a given sample, the amino acid carbon flux ranged from 17 to 210% (mean=78%) of the primary production. Such fluxes of amino acid carbon, if used exclusively by the bacterioplankton, would give growth rates ranging from 0.3 to 3.0 (mean=1.7) bacterial doublings d^-1. These calculations indicate that a large fraction of the community carbon and nitrogen flux passes through the bacterioplankton.     

Computer modeling of genome complexity variation trends in prokaryotic communities under varying habitat conditions

There are two types of organisms’ grouping in nature: mono-species populations and multi-species communities. Here at during the process of evolution the adaptability of a trait is to be tested both at population and ecocenotic levels. Size of a genome is one of the major adaptive traits, which widely varies in eukaryotic species. By contrast, prokaryotes with their small genomes are considered to have genome reduction evolutionary trend. Domination of this trend is mostly founded on population-level models. In this paper we in silico study interactions of ecocenotic and population levels. The trend of genome and metabolism reduction in prokaryotic communities was shown to be major only in comfortable environmental conditions. In subcomfortable conditions, genome and metabolism reduction leads to community simplification (in extreme case to community death). Pessimum conditions promote metabolism integration of a community and induce reciprocal genes acquiring.     

Some development patterns of plankton communities in the upwelling areas of the Pacific Ocean

The principal trophic levels, each subdivided into groups of organismic elements, are distinguished in the planktonic communities of the Eastern Equatorial and the Peruvian upwellings. Production intensity or metabolism have been determined experimentally for all elements. A scheme is suggested for computing production from data on metabolism for all the elements of a community, as well as for computing net and real production and other functional characteristics for definite trophic levels and the community as a whole. Based on the quantitative estimation of the efficiency of primary production and other functional characteristics, the development of communities is divided into production and destruction periods; they are, in turn, subdivided into steps associated with a certain degree of water trophicity. The balance of net production of the communities in the Peruvian upwelling indicates that the excess production of a community above the shelf is utilized completely in the narrow (100 to 150 sea miles) band of off-shore water. This paper describes an attempt to trace the changes taking place in the functional characteristics of plankton communities and to compare them with the changes observed in the communities of the Peruvian and East-Equatorial upwellings.     

The occurrence of glycolic acid in coastal sea water

A reasonably fast and reliable chemical method for the determination of glycolic acid in sea water is described in detail. It consists of adsorption of glycolic acid by alumina, followed by extraction with sulphuric acid and then colorimetry. The overall efficiency of recovery of this method, which is standardized internally, is approximately 67%, and about 20-fold concentration of glycolic acid is achieved. Using this method, the occurrence of glycolic acid in Ipswich Bay (Gulf of Maine, USA) was studied over a period of 6 months and was found to fluctuate between 0 and 80 g/l. The zero values occurred in January, when the phytoplankton chlorophyll values were also at their winter minimum.     

Effect of enclosure in large plastic bags on diurnal change in oxygen concentration in tropical ocean water

From November 1980 to February 1981 the concentration of oxygen dissolved in the surface mixed layer of the oligotrophic Caribbean Sea off Curaçao was quite constant (420.77±1.98 g at l^-1). However, immediately following enclosure in 4500-1 plastic bags reaching to a depth of 5 m the oxygen concentration began to decrease, down to values below saturation (405 g at l^-1) within 48 h. Autotrophic and heterotrophic nanoplankton cell numbers and algal pigments in bags remained constant or increased slightly during the first 24 h of enclosure. The rate of decrease in oxygen concentration in bags was significantly higher during daylight hours than in the night, which suggests that photo-oxidative processes were involved in the additional daytime loss of oxygen. The dramatic enclosure effect on the oxygen content of the water in the bags can be taken as evidence of the dependence of the oxygen concentration near the tropical ocean's surface on supply from below: in water freely circulating in the euphotic zone deviations from the mean oxygen concentration during a diurnal cycle were 0.47% at most, differential losses near the surface being counteracted through vertical exchange; while in water separated from the rest of the mixed layer in the plastic bags losses due to respiration of the enclosed plankton community plus an even greater loss, assigned to non-biological, photosensitized oxidation processes, were up to 10 g at O₂ l^-1 in 24 h. Although photo-oxidation is confined to the very surface the oxygen flux involved may be important enough to necessitate consideration of a photochemically induced loss factor in oxygen budget calculations, e.g. when primary production is to be estimated from diurnal oxygen curves.     

Colonization dynamics in trophic-functional structure of periphytic protist communities in coastal waters

The colonization dynamics in trophic-functional patterns of periphytic protist communities was studied in coastal waters of the Yellow Sea, northern China, from May to June, 2010. The periphytic protists represented different trophic-functional structures during colonization process. Only certain trophic-functional groups (e.g., photoautotrophs, algivores and non-selectives) occurred within the protist communities with low species number and abundance at the initial stage (1–3 days), while more trophic-functional groups (e.g., photoautotrophs, algivores, non-selectives and raptors) contributed to the communities with increased and peaked species number and abundance at the transitional (7–10 days) and equilibrium (14–28 days) stages, respectively. All heterotrophic groups were significantly fitted the MacArthur–Wilson model in colonization curves and represented higher species number and colonization rates at a depth of 1 m than at 3 m. These results may provide necessary understandings for ecological researches and monitoring programs using periphytic protists with different colonization ages in marine ecosystems.     

广州市南沙区海岸防护林群落构建技术研究

森林是稳固和改善生态环境的重要载体,因其能提供巨大的生态服务功能而备受各国政府和学界的关注。珠江三角洲地区城市化进程的步伐逐渐加快,带来一系列环境问题。以广州市南沙区海岸景观防护林（也即河涌水网林、公路隔离林、海岸防风林）建设为例,主要研究了防护林的关键构建模式、林分群落结构等方面内容。结果显示,采用多层次的乔灌草配置,遵循适地适树的原则,以本土树种为主,搭配部分优良的引进树种,采取适合的营林措施,可构建出具有一定防护功能的人工林群落。广州南沙防护林建设是珠三角地区城市森林建设的一个缩影和代表,为我国南方城市森林建设理论的创建提供了一定的参考经验。破解城市化危机,创建宜居城市环境,实现城市可持续发展,应综合考虑城市的人口集中程度,经济发展规模,环境污染模式,针对具体的水分、气候和土壤等要素,运用多学科理论和技术,制定合适的森林构建模式,并需要政府、社会组织、以及公众的协同努力。     

Vertical and horizontal structure in the picoplankton communities of a coastal upwelling system

The distribution of prokaryotic and eukaryotic picoplankton in the west coast upwelling-region off the South Island of New Zealand was investigated during midwinter (1988) the time of year when several commercially important fish species migrate into the region to breed. Picoplanktonic cells were major contributors to the autotrophic biomass, with > 80% of the particulate nitrogen and 39 to 55% of the total chlorophylla contained in the <2µm size-fraction. The prokaryotic picoplankton concentrations ranged from 6.3 × 10⁵ to 2.1 × 10⁷ cell l^–1, and the eukaryotic picoplankton between 3.9 × 10⁵ to 1.2 × 10⁷ cells l^–1. Picoplankton numbers increased with distance offshore to a maximum of ~ 3.0 × 10⁷ cells l^–1 at ~ 35 km from the coast, and then diminished towards the outer shelf and open ocean. The ratio of prokaryotic to eukaryotic cells varied between 1.01 and 4.71 in the mixed layer. Both groups declined substantially beneath the pycnocline, with no evidence of deep maxima. Prokaryotic cells dominated the planktonic cell concentrations at all but two stations, but eukaryotic cells dominated picoplankton biovolume as a result of their larger average cell size. The prokaryotic to eukaryotic picoplankton cell-number ratios in this system were considerably lower than often recorded elsewhere, and were inversely correlated with nitrate concentration. These observations show that a eukaryoticdominated picoplankton community makes a substantial contribution to autotrophic biomass in this nutrient-rich upwelling system, and may thereby play a major role in the food-web dynamics of this coastal fishery.     

Non-photosynthetic oxygen production and non-respiratory oxygen uptake in the dark: a theory of oxygen dynamics in plankton communities

Plankton respiration is commonly measured in terms of oxygen uptake, usually employing the Winkler method, much less commonly the polarographic method. Both methods produce results that can be misinterpreted when H₂O₂ production and decomposition are ignored. This paper: (1) presents experimental evidence of significant H₂O₂ involvement during plankton incubation in dark bottles, (2) explains how results differ between the Winkler and polarographic methods in the presence of H₂O₂, (3) discusses how this difference is clouded by side issues of variability inherent in the Winkler technique and the use of different bottle sizes, and (4) shows that unexpected and variable results of light-/dark-bottle incubations can all be explained by a theory of H₂O₂ production and decomposition. During an initial period in the dark, when plankton respiration has been poisoned by mercuric chloride or chloroform, O₂ increase can be measured with a polarographic oxy‐gen sensor (POS). The trend in O₂ changes is linear for several days when only respiration is occurring, but curvilinear when there is concurrent O₂ production. O₂ production in the dark and H₂O₂ decomposition are one and the same process. Measurement of oxygen by Winkler analysis and POS produce different results when H₂O₂ is present because the former method measures oxidizing equivalent while a POS measures O₂ pressure. A real difference in results between the two methods is prima facie evidence that H₂O₂ is involved. The synthesis of this new empirical evidence with diverse knowledge from various fields shows that the common practice of estimating gross community primary production from oxygen changes in light and dark bottles is based on untenable assumptions. Received: 15 April 1997 / Accepted: 17 June 1997     

Temperature adaptation in sea anemones: Physiological and biochemical variability in geographically separate populations of Metridium senile

Latitudinally separate populations of the sea anemone Metridium senile (L.) are very similar genetically by electrophoretic criteria, yet respond differently to temperature. Anemones from southern and northern California (USA) have different oxygen consumption patterns in response to acclimatory and acute changes in temperature. Northern anemones show a pronounced increase in Q₁₀ at temperatures just above the normal environmental range, but southern anemones do not. The two populations also differed in the extent of metabolic compensation to temperature following several weeks of acclimation. This acclimation regime resulted in changes in the activities of several enzymes of intermediary metabolism, yet the extent and direction of these changes did not display a consistent trend with regard to acclimation temperature or population. The biochemical concomitants of acclimatory and acute temperature effects were studied further by measuring the concentrations of adenylates (ATP, ADP, and AMP) in anemones from the two populations exposed to different temperature regimes. During cold acclimation for several weeks, total adenylate concentrations (A_T) increased in both the southern and northern populations, possibly due to metabolic rate compensation, since A_T is positively correlated with tissue metabolic rate in many species. Moreover, the extremely low weight-specific oxygen consumption rates of M. senile are probably related to its very low A_T values. Acute temperature decreases had no effect on adenylate concentrations and adenylate energy charge (AEC); in contrast, acute temperature increases led to large changes in adenylate concentrations. The effects of starvation on adenylate concentrations are pronounced, and the effect is temperature-dependent. In starved individuals held at 20°C, AEC values fell to 50% of normal values after 8 d, while those held at 10°C maintained normal AEC values.     

Implications of sea level rise for coastal dune habitat conservation in Wales,UK

The potential impact of future sea level rise and climate change on 15 Welsh coastal dune systems has been investigated. Historical Trend Analysis was undertaken using Ordnance Survey maps to quantify past shoreline change and to permit extrapolation of past trends to predict possible future shoreline positions by 2080–2100. Predictions were also made using the Bruun Rule relationship between sea level rise and shoreline response and an integrated method of assessment, Expert Geomorphological Assessment (EGA), which provides a ‘best estimate’ of future coastline change, taking into account such factors as geological constraints, the nature of past, present and future environmental forcing factors, and known coastal process–response relationships. The majority of the 15 systems investigated experienced a net increase in dune area over the last 100–120 years. Only one (Whiteford Burrows) experienced significant net area loss (>5 ha). EGA predictions suggest that several systems are likely to experience significant net loss of dune habitat over the next century, whilst continued net gain is likely to occur for systems where sediment supply rates remain high. Little net change is predicted in some systems. Considering the 15 dune systems together, it is considered unlikely that net dune habitat loss will exceed net gain over the next 100 years provided that there are no major disruptions to sediment supply and natural coastal processes.     

The role of ciliates,heterotrophic dinoflagellates and copepods in structuring spring plankton communities at Helgoland Roads,North Sea

Mesocosm experiments coupled with dilution grazing experiments were carried out during the phytoplankton spring bloom 2009. The interactions between phytoplankton, microzooplankton and copepods were investigated using natural plankton communities obtained from Helgoland Roads (54°11.3′N; 7°54.0′E), North Sea. In the absence of mesozooplankton grazers, the microzooplankton rapidly responded to different prey availabilities; this was most pronounced for ciliates such as strombidiids and strobilids. The occurrence of ciliates was strongly dependent on specific prey and abrupt losses in their relative importance with the disappearance of their prey were observed. Thecate and athecate dinoflagellates had a broader food spectrum and slower reaction times compared with ciliates. In general, high microzooplankton potential grazing impacts with an average consumption of 120% of the phytoplankton production (P _p ) were measured. Thus, the decline in phytoplankton biomass could be mainly attributed to an intense grazing by microzooplankton. Copepods were less important phytoplankton grazers consuming on average only 47% of P _p . Microzooplankton in turn contributed a substantial part to the copepods’ diets especially with decreasing quality of phytoplankton food due to nutrient limitation over the course of the bloom. Copepod grazing rates exceeded microzooplankton growth, suggesting their strong top-down control potential on microzooplankton in the field. Selective grazing by microzooplankton was an important factor for stabilising a bloom of less-preferred diatom species in our mesocosms with specific species (Thalassiosira spp., Rhizosolenia spp. and Chaetoceros spp.) dominating the bloom. This study demonstrates the importance of microzooplankton grazers for structuring and controlling phytoplankton spring blooms in temperate waters and the important role of copepods as top-down regulators of microzooplankton.     

Characterization of bacterial communities during persistent fog and haze events in the Qingdao coastal region

• Light haze had little effect on bacterial communities. • Fog and heavy haze had significant effects on these communities. • Air pollution exerted a greater influence than particle size on bacterial community. Here, we report the characteristics of bacterial communities in aerosols with different particle sizes during two persistent fog and haze events in December of 2015 and 2016 in Qingdao, China. In the early stage of pollution, the accumulation of PM_2.5 led to the accumulation of microorganisms, thus increasing the bacterial richness and diversity of fine particle sizes. With the persistence and aggravation of pollution, the toxic effect was strengthened, and the bacterial richness and diversity of each particle size decreased. When the particle concentration was highest, the richness and diversity were low for each particle size. Light haze had little influence on bacterial communities. The occurrence of highly polluted humid weather and heavy haze resulted in significant changes in bacterial community diversity, composition and structure, and air pollution exerted a greater influence than particle size on bacterial community structure. During persistent fog and haze events, with the increase of pollutants, bacteria associated with each particle size may be extensively involved in aerosol chemistry, but the degree of participation varies, which requires further study.     

The development of a natural plankton population in an outdoor tank with nutrient-poor sea water. I. Phytoplankton succession

Due to complex hydrodynamic and biological inhomogeneities, the phytoplankton species succession cannot be satisfactorily observed, apart from the seasonal blooms which occur in temperate waters. Large flexible plastic tanks have proved to be useful for such observations. In 1972, for 28 days, a phytoplankton succession in nutrient-poor water in the outer harbor of Helgoland was observed in a flexible plastic tank (3 m³). During this period, 3 phytoplankton biomass maxima were formed with many significant correlations. In the first 7 days the ammonia concentration decreased from over 6 to 2 mol 1^-1 for 14 days. The nitrate concentration remained in the range of 3–6 mol 1^-1 and then fell abruptly to 0–2 mol 1^-1. The phosphate concentration was about 0.1 mol 1^-1. Lauderia borealis dominated the first period, and its increase was significantly correlated with the decrease in ammonia. The diatom was succeeded by two dinoflagellates, Dinophysis acuminata and Prorocentrum micans. The last period of the experiment was characterized by a stronger development of Rhizosolenia species. The rapid recovery of the crop in the nutrient-poor water points to intensive remineralization processes. The irregular occurrence of ammonia near the surface was correlated with the appearance of Noctiluca miliaris at this depth. It is expected that repetitions of this type of experiment will permit further explanations of statistical correlations which are not yet clear. As a first step, in order to test hypotheses, a correlation analysis was employed to eliminate the statistically non-significant correlations.This work was supported by the Sonderforschungsbereich 94, Hamburg, of the Deutsche Forschungsgemeinschaft.     

Production and respiration of overall plankton and ultraplankton communities at the entrance to the Gulf of Finland in the Baltic Sea

Primary productivity and respiration of the overall plankton community and of ultraplankton (organisms passing through a 3-m Nuclepore filter) were studied at the entrance to the Gulf of Finland during the growth season in 1982. Data of the respiration measurements from previous years are also presented. During the development of a diatom spring bloom, the algal component could be successfully separated from the bacterial component by size fractionation with a 3-m Nuclepore filter and thus the algal respiration could be approximated, being on the order of 10 to 20% of the gross production. After the phytoplankton spring maximum, bacteria played an important role in mediating the energy flow from phytoplankton exudates to higher trophic levels. Maximum values of 1 230 and 740 mg O₂ m^-2 d^-1 were recorded for overall and for ultraplankton respiration, respectively, during late July. High productivity values coupled with low phytoplankton biomass and low inorganic nutrient values were also recorded in late July, indicating effective nutrient regeneration and rapid turnover of the plankton community. During late summer, a considerable fraction (over 30%) of phytoplankton production was released as exudates, suggesting that much of the energy is channeled to higher trophic levels via bacterial pathways rather than by direct herbivorous grazing during this season. The summer development of phytoplankton community structure and functioning is strongly controlled by hydrographic conditions, i.e. by nutrient inputs via upwelling and by water temperature. A carbon budget for late summer indicated that bacteria may contribute only up to 50% of the overall respiration of the plankton community, which suggests that heterotrophs other than bacteria play an important role in nutrient regeneration. The present study stresses the importance of energy flow via the phytoplankton exudatebacteria-micrograzer pathway in relatively oligotrophic, brackish water ecosystems.     

Growth of sea bass,Dicentrarchus labrax,larval and juvenile stages and their otoliths under quasi-steady temperature conditions

The relationship between somatic growth and growth of otoliths of sea bass larvae, postlarvae and juveniles under relatively steady temperature conditions was studied. Larvae were incubated at the constant ambient temperature of 13.5°C, whereas postlarvae and juveniles were reared at a comparatively steady temperature ranging from 18.6 to 20.4°C, with a mean of 19.67°C. The patterns of both somatic and otolith growth were found to be similar. Differentiated data on larvae length and otolith diameters indicated three periods of change in their growth rates. Since temperature was kept relatively steady during the experiment, and larvae fed ad libitum, these periods could be attributed with relative certainty to intrinsic changes which occur during stage-specific periods of growth. The third period of change in both growth rates indicates a specific phase of growth during metamorphosis. The changes in growth rates, as well as the raw time series of the growth of both larval lengths and otolith diameters, may be described by higher order polynomials with a high degree of probability levels. A non-linear relationship between body length and otolith diameters was established, indicating positive allometric growth of otoliths. It was also observed that the coefficient of allometric growth changed at the time estimated for the end of metamorphosis. Thus, a non-linear relationship and changes in the coefficients of allometry should be borne in mind when back-calculating somatic growth from the growth of otoliths.     

Diurnal vertical migration of Cochlodinium polykrikoides during the red tide in Korean coastal sea waters

The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally < or = 2.86 micromol l(-1), but at 1400-1500, the concentration in the surface layer reduced to < or = 0.14 micromol l(-1). Moreover, the concentration gradually increased as the depth increased to > or = 5 m. These results showed that the nutrient-consumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources ratherthan the inorganic-phosphorus compounds.     

Differences in photosynthetic pigment signatures between phytoneuston and phytoplankton communities in a coastal lagoon of Baja California

In order to understand the relationships between the dynamics of phytoplankton populations in the surface microlayer (MIL) and in the water column below (SSW), this study used high-performance liquid chromatography-derived pigment markers in samples from a coastal lagoon of Baja California (Estero de Punta Banda, EPB) under summer (October 2003) and winter (December 2003) conditions. Photosynthetic pigment signatures of phytoplankton at the air–sea interface (phytoneuston) and subsurface measurements were related to bottom-up (temperature, salinity, nutrient concentrations) and top-down factors (zooplankton abundance). Slicks and scum layers were observed in the inner part of the lagoon and coincided with greater stratification of layers just below the sea surface and lower wind intensities. In general, spatial variability in pigment markers and ancillary data was very high and resulted in non-significant differences between MIL and subsurface samples when different regions of EPB or sampling dates were compared. However, different patterns were found between pigments and environmental factors of MIL and SSW samples when the relative numbers of stations with positive and negative differences (ΔX = X _MIL−X _SSW) were computed. For each survey, pigment markers of phytoneuston and phytoplankton samples were not necessarily correlated. Further analysis revealed that those markers (19′-butanoyloxyfucoxanthin, prasinoxanthin, divinil-chlorophyll a) corresponded to picophytoplankton groups (haptophyte, prasinophyte, and prochlorophyte). On both dates, the MIL was enriched in 19′-hexanoyloxyfucoxanthin (a marker for a type 4 haptophyte) and fucoxanthin (marker for bacillariophytes, haptophytes, and crysophytes) and depleted in peridinin (marker for dinophytes). Different zooplankton grazers accumulated in the MIL (loricate tintinnids) and in SSW (copepod nauplii).     

Trophic structure of coastal Antarctic food webs associated with changes in sea ice and food supply

Predicting the dynamics of ecosystems requires an understanding of how trophic interactions respond to environmental change. In Antarctic marine ecosystems, food web dynamics are inextricably linked to sea ice conditions that affect the nature and magnitude of primary food sources available to higher trophic levels. Recent attention on the changing sea ice conditions in polar seas highlights the need to better understand how marine food webs respond to changes in such broad-scale environmental drivers. This study investigated the importance of sea ice and advected primary food sources to the structure of benthic food webs in coastal Antarctica. We compared the isotopic composition of several seafloor taxa (including primary producers and invertebrates with a variety of feeding modes) that are widely distributed in the Antarctic. We assessed shifts in the trophic role of numerically dominant benthic omnivores at five coastal Ross Sea locations. These locations vary in primary productivity and food availability, due to their different levels of sea ice cover, and proximity to polynyas and advected primary production. The delta15N signatures and isotope mixing model results for the bivalves Laternula elliptica and Adamussium colbecki and the urchin Sterechinus neumeyeri indicate a shift from consumption of a higher proportion of detritus at locations with more permanent sea ice in the south to more freshly produced algal material associated with proximity to ice-free water in the north and east. The detrital pathways utilized by many benthic species may act to dampen the impacts of large seasonal fluctuations in the availability of primary production. The limiting relationship between sea ice distribution and in situ primary productivity emphasizes the role of connectivity and spatial subsidies of organic matter in fueling the food web. Our results begin to provide a basis for predicting how benthic ecosystems will respond to changes in sea ice persistence and extent along environmental gradients in the high Antarctic.