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Sampling, preservation, enumeration and biomass of marine protozooplankton
Abstract
This chapter reviews the commonly used methods in marine studies. Although the chapter is directed primarily toward marine protozooplankton assemblages, many of the methods cited in the chapter may be modified, such as by using buffers, for application to freshwater organisms. There are many reasons to sample the protozooplankton. These organisms perform a number of functions in pelagic ecosystems. They are major grazers of bacteria and phytoplankton and are important nutrient recyclers. Forms such as plastidic ciliates, which contain functional chloroplasts or whole algal cells, are primary producers. As prey for higher order consumers, nano- and microzooplankton constitute a trophic link between the microbial loop and the classical metazoan food web. A quantitative evaluation of any of these functions requires accurate estimates of the numerical abundance and biomass of nano- and microzooplankton. To estimate abundance and biomass, it is necessary to collect—usually preserve—and enumerate the target organisms. With the exception of the sarcodines, collection methods are similar for the majority of nano- and microzooplankton taxa. Techniques of preservation and enumeration may differ for the nano- and microzooplankton, and in some cases are taxon-specific, depending on the objectives of the individual study. Alternatively, live counting may be done for some protozooplankton taxa.
... Niskin bottles). Firstly, it minimizes the cell disruption due to the turbulence and pressure, caused by pumps and plankton nets (Gifford & Caron, 2000). Moreover, plankton nets collect only a large fraction of ciliates (such as Tintinnids, in pioneering studies), but let nano-ciliates (<20 µm) pass through. ...
... For the precise quantifying of ciliates, Lugol's solution is better than many aldehyde-based fixatives (Stoecker et al., 1994). The disadvantage of Lugol's solution is in masking the chlorophyll fluorescence, which may be needed to recognize mixotrophic ciliates (Gifford & Caron, 2000). Preservation in glutaraldehyde is used mainly for epifluorescence and electronic microscopy. ...
... The abundance of ciliates can be obtained in special settling chambers by counting under a microscope (Gifford & Caron, 2000). Lugol's fixation enhances the sinking of cells and also stains them a dark brown colour, that simplifies counting of ciliates. ...
This is the third volume in a series of zooplankton atlases of the Baltic Sea. It describes zooplankton community of the open Baltic waters, which is a mixture of marine species and diverse representatives of brackish water and limnetic faunas. Brief information on morphology and ecology of zooplankton, picture key of higher invertebrate taxa and methodological recommendations for sampling, identification and counting of zooplankton are provided. Two checklists present ca. 1000 names of micro-, meso- and macrozooplankton organisms. The volume is illustrated by 290 colour photographs that are combined into 48 photo plates depicting most common species of Protozoa (Ciliata), Cnidaria, Ctenophora, Turbellaria, Rotifera, Branchiopoda, Copepoda, Chaetognatha and Copelata, as well as meroplanktonic larvae of Polychaeta, Mollusca, Cirripedia, Bryozoa and Echinodermata. The atlas is recommended for university students, zoologists and aquatic ecologists who are investigating and monitoring the pelagic ecosystem of the Baltic Sea.
... Niskin bottles). Firstly, it minimizes the cell disruption due to the turbulence and pressure, caused by pumps and plankton nets (Gifford & Caron, 2000). Moreover, plankton nets collect only a large fraction of ciliates (such as Tintinnids, in pioneering studies), but let nano-ciliates (<20 µm) pass through. ...
... For the precise quantifying of ciliates, Lugol's solution is better than many aldehyde-based fixatives (Stoecker et al., 1994). The disadvantage of Lugol's solution is in masking the chlorophyll fluorescence, which may be needed to recognize mixotrophic ciliates (Gifford & Caron, 2000). Preservation in glutaraldehyde is used mainly for epifluorescence and electronic microscopy. ...
... The abundance of ciliates can be obtained in special settling chambers by counting under a microscope (Gifford & Caron, 2000). Lugol's fixation enhances the sinking of cells and also stains them a dark brown colour, that simplifies counting of ciliates. ...
This is the Second Edition (improved and extended) of the third volume in a series of zooplankton atlases of the Baltic Sea. It describes zooplankton community of the open Baltic waters, which is a mixture of marine species and diverse representatives of brackish water and limnetic faunas. Brief information on morphology and ecology of zooplankters, picture key to higher invertebrate taxa and methodological recommendations for sampling, identification and counting of zooplankton are provided. Two checklists present more than 1030 names of micro-, meso- and macrozooplankton organisms. The volume is enhanced by 4 tables, 31 line drawing, and 462 colour photographs. The photographs of zooplankters are combined into 63 photo plates depicting most common species of Protozoa (Ciliata), Cnidaria, Ctenophora, Turbellaria, Rotifera, Phyllopoda, Copepoda, Chaetognatha and Copelata, as well as meroplanktonic larvae of Polychaeta, Mollusca, Cirripedia, Bryozoa and Echinodermata. The atlas is recommended for university students, zoologists and aquatic ecologists who are investigating and monitoring the pelagic ecosystem of the Baltic Sea.
... Some disadvantages reported in using Lugol's iodine solution are that it does not preserve the cell shape and size of live specimens and the gas vacuoles of cyanobacteria were reported to be largely destroyed (John et al. 2011). It also tends to mask chlorophyll fluorescence that hinders counting of cells in mixotrophic species (Gifford and Caron 2000). Lugol's solution tends to dissolve hard structures such as coccoliths and diatom frustules and hence, it is not an ideal preservative for these taxa (Gifford and Caron 2000). ...
... It also tends to mask chlorophyll fluorescence that hinders counting of cells in mixotrophic species (Gifford and Caron 2000). Lugol's solution tends to dissolve hard structures such as coccoliths and diatom frustules and hence, it is not an ideal preservative for these taxa (Gifford and Caron 2000). ...
... A solution of potassium-iodide and iodine (Lugol's iodine solution) is commonly used as a fixative for microscopic analysis of phytoplankton, nanozooplankton, microzooplankton (Gifford and Caron 2000), and mesozooplankton samples (Knoechel and Steel-Flynn 1989;Koski et al. 2005;Jaspers and Carstensen 2009). As neutral Lugol's iodine solution does not include carbon and nitrogen, neutral Lugol's iodine solution is expected to also be an effective fixative for carbon or nitrogen stable isotope analyses. ...
... Thus, Lugol's iodine can fix sediment trap samples in situ. However, we recommend that a sediment trap filled with 10% Lugol be deployed at the water depth in low light intensity and low temperature (< 5 C) to prevent decomposition of Lugol's iodine due to light and high temperature (Gifford and Caron 2000). ...
Carbon and nitrogen stable isotope and molecular analyses are common tools for marine ecological and biological research. However, it is difficult to fix samples for both analyses using only one preservative. A solution of potassium iodide and iodine (known as Lugol's iodine solution) is considered to be a suitable preservative; however, the effectiveness of Lugol's iodine solution for long‐term preservation of samples for stable isotope analysis and molecular analysis has not yet been investigated. We tested the effectiveness of 5% and 10% Lugol's iodine solutions by comparing them with marine plankton samples preserved in a 5% formalin solution, as well as preserved by freezing. Although δ13C and δ15N values of samples fixed in 5% formalin and 5% Lugol's iodine solution were significantly different from those of frozen samples, there were no significant differences in both δ13C and δ15N values between samples fixed in 10% Lugol's iodine solution and frozen samples, when preserved for a duration from 1 week up to 6 months. Polymerase chain reaction (PCR) assay of samples fixed in 10% Lugol's iodine solution after 18 months of preservation succeeded; however, the DNA in samples fixed in 5% formalin and 5% Lugol's iodine solution could not be amplified using PCR. There was no difference in the sequences of partial 18S rRNA genes between samples fixed in 10% Lugol's solution and frozen samples. Thus, we conclude that 10% Lugol's solution is a suitable fixative for both of carbon and nitrogen stable isotope and molecular analyses.
... Thus, early on, the axiom of plankton research, "no plankton sampler or combination of plankton samplers, can provide a true estimate of abundance for all components of the plankton at any one time" (Owens et al. 2013) was established. In recognition of the fact that plankton nets do not retain most soft--bodied ciliates and dinoflagellates, for microzooplankton studies, the examination of settled material from whole water samples is typically recommended; the exception is for protists with shells or skeletons such as many rhizaria taxa or tintinnid ciliates for which net sampling may be employed (e.g., Gifford & Caron 2000). ...
... There is a lack of firm recommendations for microzooplankton sampling in both the older (see Tranter 1968, pp 150--152) and newer handbooks of zooplankton sampling (Gifford and Caron 2000) reflecting the fact that sampling needs to be adapted to the goal in mind. For example, a complete census of species richness requires temporally intensive sampling over long periods of time while estimating average abundance can likely be derived from a few samples representative of different seasons. ...
Most tintinnid species have a shortest linear dimension < 50 μm. Hence, a priori, nets of mesh sizes ≥ 50 μm will likely under‐sample most tintinnid species. However, studies often appear (23 since 2015) using sampling with nets of meshes sizes ≥ 50 μm, reporting both tintinnid concentrations, and community composition. How biased are results from using coarse mesh nets? We provide a comparison of whole water vs. net sampling based on fortuitous, that is, unplanned, parallel sampling. Pairs of samples from a standard monitoring station in the Bay of Villefranche (N.W. Mediterranean Sea) taken on 44 dates from 2013 to 2018 were compared. Tintinnids were enumerated in settled material from a water column sample, an integration of six discrete depth samples between 5 and 70 m, prepared for analysis of phytoplankton composition and in material from a plankton net (52 μm mesh) tow from 70 to 0 m, taken the same day. Despite the large confidence limits due to low raw cell counts from whole water samples, cell concentration estimates were about an order of magnitude higher than those from plankton net samples and frequently biomass estimates as well. Community composition also differed. The most common species in whole water samples were small (diameter ≤ 20 μm), and some common forms were absent, or nearly, from the net samples. We show that, while valuable for collecting larger and rarer species, coarse net samples do not yield robust estimations of overall concentrations, nor allow identification of the dominant tintinnid species.
... Choreotrichia and Oligotrichia biomass was in general higher at BK (Fig. 6aþb) when compared to OFF station (Fig. 6cþd) and no distinct seasonality patterns could be observed. However, it must be noted that the present data on Ciliophora must be treated with caution since reverse filtration might have caused a loss in some delicate, aloricate ciliate species (Gifford and Caron, 2000;Gowing et al., 2003). ...
... However, the tintinnid biomass at the BK and OFF stations was considerably higher than that for the southern Indian Ocean regions. However, the actual biomass of ciliates might have been underestimated in the pre3sent study since reverse filtration was used during the sampling process which might have caused a bias in the biomass estimates of delicate, aloricate ciliate species (Gifford and Caron, 2000;Gowing et al., 2003). ...
Seasonal dynamics of microzooplankton and changes in environmental condition were analysed during a one-year field sampling campaign in the Sea of Oman at two different stations. Monsoon winds in this region cause distinct seasonality patterns with high primary productivity during the south-west monsoon in summer (June to October) and north-east monsoon periods in winter (November to March). Microzooplankton in the Sea of Oman showed several biomass peaks throughout the year. In general, higher biomass occurred during the south-west monsoon when compared to the north-east monsoon period with maxima of 190 µg C l⁻¹at the inshore station Bandar Al-Khyran at 1m and 308 µg C l⁻¹ at 10m water depth. At the offshore-station, peaks of 372 µg C l⁻¹ (1m) and 256 µg C l⁻¹ (20m) occurred during the south-west monsoon. A strong coupling between phytoplankton and microzooplankton was observed during monsoon periods but some microzooplankton peaked during inter-monsoon periods when chlorophyll concentration was low (Bandar Al-Khyran: 372 µg C l⁻¹ at 1m and 196 µg C l⁻¹, 10m; Offshore-station: 419 µg C l⁻¹, 20 m). The initiation of phytoplankton blooms in the Sea of Oman was bottom-up controlled due to strong seasonal nutrient influx during south-west and north-east monsoon periods. Highest microzooplankton biomass occurred during monsoon periods with a dominance of Noctiluciphyceae and peaks of 7596 µg C l⁻¹ at Bandar Al-Khyran (1m) and 5942 µg C l⁻¹ (10m). Copepod nauplii, Amoebozoa and Larvacea contributed substantially to microzooplankton biomass throughout the year. Ciliophora contributed low proportion to the total microzooplankton biomass peaking both during monsoon and inter-monsoon periods. During the spring inter-monsoon, choreotrich ciliates (tintinnids) showed distinct peaks of 15.9 µg C l⁻¹ at Bandar Al-Khyran (1m) and 17.7 µg C l⁻¹ (10m) as well as 18.2 µg C l⁻¹ at Offshore-station (20m). The interplay between bottom-up controlled primary production and top-down control mechanisms regulates the phenology patterns of specific microzooplankton groups in the Sea of Oman thus pointing at complex trophodynamic interactions at the lowermost food-web level in this low-latitude ecosystem.
... This is reflected in the kinds of samplers developed for their capture from the water column. Small microzooplankton species often occur in large numbers in a litre of seawater and can be collected by water-bottle samplers that take discrete samples of small volumes of water (a few litres) ( Gifford and Caron, 2000). For the somewhat less abundant mesozooplankton, pumping systems were developed that sample intermediate volumes of water (tens of litres to tens of cubic metres) ( Miller and Judkins, 1981). ...
... For microzooplankton (heterotrophic flagellates, dinoflagellates, ciliates, and sarcodines), the complexity of the make-up of the animals requires several different preservation methods in order to assess the entire suite of taxa in a sample ( Stoecker et al., 1994). Commonly used are formaldehyde, glutaraldehyde, Bouin's solution, and Lugal's iodine solution ( Gifford and Caron, 2000). For heterotrophic dinoflagellates, formalin or glutaraldehyde is suitable since they do not interfere with chlorophyll fluorescence. ...
... The extensive morphologies of ciliates allowed researchers to characterise them, and investigate their abundances using various microscopy-based methodologies. Some of the most common quantification approaches that have been extensively used throughout the last few decades include the use of counting chambers (e.g., the Utermöhl method; Kemp et al., 1993;Utermöhl, 1931) the Quantitative Protargol Staining (QPS) Gifford & Caron, 2000;Lynn & Montagnes, 1991) and fluorescence in situ hybridization (FISH), which simplified the enumeration by using a target-specific probe and fluorescence microscopy Filker et al., 2015). Relatively recent advances introduced an automated imaging and cell counting of diverse protistan groups (Mangot et al., 2018), however, the typical bias of microscopy-based methods remains also in this automated solution: weaker fluorescence signals are easily overlooked, the fluorescence of non-target particles may lead to false positives, and only small volumes of water can be screened at a time, making the detection of low-abundant target organisms very difficult. ...
Ciliates play a key role in most ecosystems. Their abundance in natural samples is crucial for answering many ecological questions. Traditional methods of quantifying individual species, which rely on microscopy, are often labour‐intensive, time‐consuming and can be highly biassed. As a result, we investigated the potential of digital polymerase chain reaction (dPCR) for quantifying ciliates. A significant challenge in this process is the high variation in the copy number of the taxonomic marker gene (ribosomal RNA [rRNA]). We first quantified the rRNA gene copy numbers (GCN) of the model ciliate, Paramecium tetraurelia , during different stages of the cell cycle and growth phases. The per‐cell rRNA GCN varied between approximately 11,000 and 130,000, averaging around 50,000 copies per cell. Despite these variations in per‐cell rRNA GCN, we found a highly significant correlation between GCN and cell numbers. This is likely due to the coexistence of different cellular stages in an uncontrolled (environmental) ciliate population. Thanks to the high sensitivity of dPCR, we were able to detect the target gene in a sample that contained only a single cell. The dPCR approach presented here is a valuable addition to the molecular toolbox in protistan ecology. It may guide future studies in quantifying and monitoring the abundance of targeted (even rare) ciliates in natural samples.
... Because of their fragility, they often require sampling methods other than plankton nets (e.g., Niskin bottles). Also, protozooplankton species identification requires preservation procedures for ultrastructural characterization by electronic microscopy (Gifford and Caron, 2000). ...
... Since the dissolved Sr in seawater is below the level of saturation , 1973, 1974, the SrSO 4 skeletons of Acantharia are highly susceptible to dissolution after death, and are not conserved in preservatives that are commonly used for Radiolaria such as 5% buffered formalin (Beers and Stewart 1970). Adding Sr at a concentration 10-20 times higher than that in natural seawater was found to be effective for preventing skeletal dissolution (Beers and Stewart 1970;Gifford and Caron 2000;Michaels 1988) or the use of ethanol is also known to be effective to preserve Acantharia (De Deckker 2004), although those methods have not been applied to routine plankton sampling. Alternatively, the use of acid-Lugol's solution with a lower concentration of SrSO 4 (1.25 times higher than that in natural seawater) has been recommended for the preservation of microzooplankton including Acantharia in the Protocols for the Joint Global Ocean Flux Study Core Measurements (Knap et al. 1996). ...
Acantharia are marine planktonic unicellular eukaryotes belonging to Radiolaria that are difficult to preserve in formalin seawater due to the rapid disintegration of their internal skeleton composed of strontium sulfate (SrSO4; also known as celestite) upon death. Adding Sr at concentrations 10–20 times higher than that in natural seawater to formalin is effective in preventing skeletal dissolution, although this method has not been applied to routine plankton sampling. In this study, we examined the effectiveness of 2% acid-Lugol’s solution for preserving Acantharia. The concentration of Acantharia in field-collected samples stored in a 250-mL bottle containing 2% acid-Lugol’s solution did not change significantly over 390 days. In contrast, the concentration of Acantharia stored in 5% formalin seawater with Sr addition significantly decreased over this period, indicating that acid-Lugol’s solution is a more effective preservative for the cells. These results expand the opportunities for studying Acantharia which have been considered as a difficult group to be quantified in routine microplankton sampling.
... Different biomass conversion factors have been applied to a wide diversity of nano, micro, and macro organisms, including foraminifera or other similar groups (Gifford & Caron, 2000). The conversion factor from biovolume to wet body mass of 1.027 g cm −3 was adopted for deep-sea benthic foraminifera by Saidova (1967), who considered the plasma density as not less than the seawater specific gravity in deep waters. ...
Foraminifers are widespread, highly abundant protists and active participants in marine carbon cycling. Their biomass might represent almost half of the total meiobenthic biomass in the deep sea. Foraminiferal biomass is frequently assessed through geometric models and biovolume estimates due to its non-destructive nature, which allows estimates of individuals from palaeoecological, museum, and living samples. To increase the accuracy of foraminiferal biovolume and biomass assessment we evaluate and propose geometric models for 207 foraminiferal taxa and the species’ average cell occupancy of the test. Individual test dimensions were measured to calculate volume (µm³), and the percent of cell occupancy (PCO) of the test was measured to assess the biovolume (µm³). These data were converted into individual biomass measurements (µg Corg ind−1). Our high intra- and interspecific PCO variance suggest that a mean PCO for each species represents the natural variability of occupancy more accurately than a predetermined fixed percentage for the whole assemblage, as previously asserted in the literature. Regression equations based on the relationship between test dimensions and volumes are presented. The geometric models, the PCO adjustment, and the equations will reduce time, effort, and discrepancies in foraminiferal biovolume and biomass assessments. Therefore, these results can improve the use and reliability of foraminiferal biomass in the future, facilitating its use in (1) distinct approaches including carbon flux estimations, (2) determining the effects of climate change on the marine trophic webs, and (3) environmental monitoring programs.
... The entire area of the Utermöhl chamber was examined at magnifications of 200× or 400×, by using an inverted microscope (Nikon-TMD 300). The carbon to volume ratios of 0.148 and 0.19 pg C μm 3 for ciliates and dinoflagellates, respectively, were used (Ohman and Snyder 1991;Gifford and Caron 2000). Statistical analyses were performed by using Statistical for Windows (StatSoft Inc.). ...
... The opening and closing depths for each station are specified in Table 1. The MOCNESS samples were fixed in-situ with 5% formaldehyde buffered with sodium tetraborate to preserve the morphological structures of planktonic organisms (Gifford and Caron, 2000). ...
The deep-sea blue and red shrimp Aristeus antennatus is a valuable fishing resource in the Northwestern Mediterranean Sea, currently under a local co-management plan in the port of Palamós (Spain). The management measures, although effective, might benefit other ports due to the dispersal patterns of the species pelagic larvae. Gathering information about A. antennatus larval distribution is a key step to describe these patterns, towards the establishment of well-dimensioned management measures. After a first detection of its larvae as the dominant species in the decapod community in Blanes submarine canyon, this broader approach tackles the entire management area along the Eastern Spanish Mediterranean coast (Geographic Subarea 6; GSA 6). Zooplankton sampling was carried out at 101 stations in surface waters (0.5–1 m) and in 8 stations in stratified vertical sampling (0–1200 m) during July–August 2016. Over 6500 A. antennatus larvae of all known stages were found, the first protozoea (PZ I) representing over 95% of the total. This is the first study taking into account the vertical migration of A. antennatus larvae, and we observed a broad distribution of PZ I throughout the water column. Plankton observations of the species larval distribution were supported by an Individual-Based Model suggesting aggregations in the northern submarine canyons, influenced by cold waters from the Northern current and the geomorphology of the Ibiza Channel. The present study proposes a division of the GSA 6 in three zones to improve fishery management measures.
... Class 1: tll ≤ 200 µm and ahl < 10 µm; class 2: tll = 200-230 µm and ahl = 10-30 µm; class 3 tll = 230-310 µm and ahl = 30-110 µm. Cell volumes were converted to carbon values using the appropriate formulae and conversion factors, as: tintinnids, pg C cell −1 = µm 3 × 0.053 + 444.5 (Verity and Langdon 1984); aloricate ciliates, pg C cell −1 = µm 3 × 0.14 (Putt and Stoecker 1989); heterotrophic dinoflagellates, pg C cell −1 = µm 3 × 0.11 (Edler 1979); others protozoans, pg C (Gifford and Caron 2000); micrometazoans, pg C cell −1 = µm 3 × 0.08 (Beers and Stewart 1970). ...
The Western Antarctic Peninsula (WAP) is experiencing rapid climate warming, resulting in affecting the marine food web. To investigate the microzooplankton spatial distribution and to assess how climate change could affect the tintinnids community, sea water samples were collected during late summer 2018 at 19 stations in three different areas: Deception Island, Elephant Island and Antarctic Sound. The microzooplankton community comprised mainly tintinnids, aloricate ciliates, heterotrophic dinoflagellates and micrometazoans. Microzooplankton abundance varied between 3 and 109 ind. L ⁻¹ and biomass ranged from 0.009 to 2.55 µg C L ⁻¹ . Significant differences in terms of abundance and taxonomic composition of microzooplankton were found among the three sampling areas. Deception Island area showed 44% of tintinnids and the rest were heterotrophic dinoflagellate, aloricate ciliates and micrometazoans. In Elephant Island and Antarctic Sound areas, tintinnids reached, respectively, 73% and 83% of the microzooplankton composition, with all the other groups varying between 20 and 30%. Tintinnids were the most representative group in the area, with the species Codonellopsis balechi , Codonellopsis glacialis , Cymatocylis convallaria and Cymatocylis drygalskii. The highest amounts of tintinnids were found at the surface and 100 m depth. The above mentioned species may be considered key species for the WAP and therefore they can be used to track environmental and hydrographical changes in the area. In late summer, microzooplankton presented low abundances and biomass, nevertheless they represented an important fraction of the planktonic community in the area.
... Наблюдения за живыми инфузориями производили на предметных стеклах. Особь из «живой» пробы отлавливали при помощи микропипетки и помещали в лунку с фиксирующей жидкостью (10%-ый раствор глутаральдегида или жидкость Буэна) (Dragesco, Dragesco-Kerneis, 1986;Сarey, 1992;Foissner et al., 1999;Gifford, Caron, 2000;Kurilov, 2010). После кратковременной фиксации (5-10 мин) инфузорий помещали в каплю чистого глицерина или подкисленного уксусной кислотой раствора красителя в чистом глицерине (для окраски ядер). ...
Монография посвящена изучению морских экосистем крупных портовых городов северо-восточного шельфа Черного моря – Новороссийска и Туапсе, подверженных высокому уровню антро-погенного загрязнения. Приводятся результаты исследований фитопланктона, гетеротрофного бактериопланктона, простейших (зоофлагеллят, инфузорий), голопланктона, меропланктона, ихтиопланктона. Особое внимание уделено анализу зообентоса рыхлых грунтов как индикатору эвтрофирования донных отложений. Выявлено, что накопление лабильных сульфидов в верхнем слое донных осадков в Новороссийском и Туапсинском портах является одним из наиболее опасных экологических последствий антропогенного загрязнения. Представлены результаты мониторинга балластных вод коммерческих судов, выполненного в Новороссийском порту; даны оценки экологических рисков морских биоинвазий с водным транспортом в северо-восточную часть Черного моря. Разработаны энергетические трофодинамические модели портовых экосистем, произведен анализ их структурно-функциональной трансформации. Выявлены тенденции изменчивости качества водных ресурсов и их потенциальные способности к естественному самоочищению. Оценена роль антропогенного загрязнения и инвазий чужеродных видов в биоразнообразии и продуктивности северо-восточного шельфа Черного моря.
The monograph is devoted researches of marine ecosystems of large seaports of the northeastern Black Sea – Novorossiysk and Tuapse exposed to anthropogenic impact. Results of research of phytoplankton, heterotrophic bacteria, protozoan, holoplankton, meroplankton, ichthyoplankton are presented. The analysis of zoobenthos as indicator of euthrophication of benthic sediments are performed. It is revealed that sulfides accumulation in the top layer of benthic sediments of the ports of Novorossiysk and Tuapse is the most dangerous ecological consequence of anthropogenous pollution. Results of monitoring biological invasions and ships’ballast waters in the Novorossiysk port are submitted. Tendencies of variability of quality of water resources and their potential abilities to ambiental selfpurification are revealed. The estimations of ecological risks of marine biological invasions with water transport in the northeastern Black Sea are given. Trophodynamic models of port ecosystems have been developed, the analysis of their structurally functional transformation has been made. Role of anthropogenic pollution and invasions of alien species in the biodiversity and the productivity of the northeastern Black Sea has been estimated.
... If doliolids were visually abundant, the sample was split in parts suitable for examination using a Folsom plankton sample splitter (Griffiths et al. 1984). Samples were diluted to a total known volume, and doliolids were identified and counted in duplicate aliquots, according to sample concentration (Gifford and Caron 2000). Generally, 1-2% of the total sample was counted. ...
Gelatinous zooplankton play a crucial role in pelagic marine food webs, however, due to methodological challenges and persistent misconceptions of their importance, the trophic role of gelatinous zooplankton remains poorly investigated. This is particularly true for small gelatinous zooplankton including the marine pelagic tunicate, Dolioletta gegenbauri. D. gegenbauri and other doliolid species occur persistently on wide subtropical shelves where they often produce massive blooms in association with shelf upwelling conditions. As efficient filter feeders and prodigious producers of relatively low‐density organic‐rich aggregates, doliolids are understood to contribute significantly to shelf production, pelagic ecology, and pelagic–benthic coupling. Utilizing molecular gut content analysis and stable isotope analysis approaches, the trophic interactions of doliolids were explored during bloom and non‐bloom conditions on the South Atlantic Bight continental shelf in the Western North Atlantic. Based on molecular gut content analysis, relative ingestion selectivity varied with D. gegenbauri life stage. At all life stages, doliolids ingested a wide range of prey types and sizes, but exhibited selectivity for larger prey types including diatoms, ciliates, and metazoans. Experimental growth studies confirmed that metazoan prey were ingested, but indicated that they were not digested and assimilated. Stable isotopic composition (δ13C and δ15N) of wild‐caught doliolids, during bloom and non‐bloom conditions, were most consistent with a detrital‐supplemented diet. These observations suggest that the feeding ecology of D. gegenbauri is more complex than previously reported, and have strong and unusual linkages to the microbial food web.
... helgolandicus (average size > 2 mm) and one hundred A. clausi (average size > 850 µm) specimens. Hence, biomasses typically exhibited by field samples are likely to oscillate between the boundaries of these regressions (Gaughan & Potter, 1995;Gifford & Caron, 2000;Pardal & Azeiteiro, 2001). As such, these regressions are adequate for the analysis of nearly all environmental samples, after the appropriate splitting and subsampling. ...
Lately, a substantial global effort has been undertaken to implement an ecosystem-based management legislation for the conservation of marine ecosystems and the enhancement of the marine health status. In Europe, the Marine Strategy Framework Directive (2008) dictates that the EU countries must achieve a Good Environmental Status of their seas by 2020. Thus, it implies the need for the protection, sustainable management and restoration of the European seas.
Furthermore, this directive emphasises zooplankton under its Descriptor 4, Food Webs. Zooplankton has been traditionally identified using techniques as the light microscopy. This analysis is costly and time-consuming, besides requiring several expert taxonomists. Nonetheless, the rigorous species-specific data produced by these people provide information that cannot be obtained when considering bulk communities as a proxy.
In fact, a species-specific analysis of zooplankton biomasses, namely copepods, is paramount. Besides being highly relevant in the biochemical Carbon cycle, different copepod species exert a differential pressure on distinct food sources and are predated selectively by direct consumers.
To enhance the ecosystem-based management policies and legislation, a cost-effective solution for the routine analysis of zooplankton must arise. The proposed method is based on an absolute quantitative PCR. It is simultaneously able to discriminate different marine copepods species and account for its biomass. Additionally, it considers the use of a positive internal control, the estuarine Acartia tonsa. It is added before the DNA extraction process and acts as a normalisation agent. Thus, sample comparison is possible, and different DNA extraction efficiencies are taken into consideration.
Using carefully designed species-specific primer-pairs for the mitochondrial Cytochrome Oxidase I, tested over a wide range of planktonic species, two strong standard curves were assembled. Each regression correlates the logarithm of Acartia clausi’s or Calanus helgolandicus’ biomasses with the control-normalised Cq (fractional PCR cycle number where the fluorescence signal crosses an arbitrary threshold). Standard samples were prepared by taking accurate measurements of every target species’ adult/copepodite at that given aliquot.
The molecular method was tested on five independent environmental samples. Results indicate that the standard curves produced a biomass estimate similar to the traditional approach, provided that there is an adequate dilution, besides an efficient DNA extraction.
x
Results also suggest the existence of a general calanoid biomass-Cq regression. Proven valid in the future, it would effortlessly extend the range of detectable species. Finally, this method is pronouncedly less laborious than the traditional. Overall, the present study proved that the proposed method is a valid alternative for the routine analysis of zooplankton’s biomasses. This confirmation suggests that it may be used to benefit fishing models’ predictability. At last, it also suggests that zooplankton-based biological monitoring indexes may be improved, and their results accelerated with simplicity.
... Diatoms abundance was obtained by settling the fixed samples in settling chambers, stained by Lugol'92s solution (Throndsen, 1978) and examined under an inverted microscope (Hasle, 1978;Gifford and Caron, 2000). Wet samples were smeared onto a slide for immediate examination and determination of possible further treatments. ...
The present work describes the effect of silicon (Na2SiO3.6H2O) on biodiesel production and growth of freshwater diatoms. The results revealed that the growth of diatoms in terms of number of cells was better at lower concentrations of silicon .Maximum growth (1x104 cells/ml) could be recorded at 0.05 mg/l which was maintained up to 1.0 mg/l of silicon concentration However, the growth of diatoms decreased Considerably with the increasing concentration of silicon Beyond 1.0 mg/l. When the silicon concentration was increased to 5.0 mg/l, the growth of diatoms was reduced drastically (4x103 cells /ml). The minimum growth (2 x 102) of diatoms in terms of number of cells was recorded in presence of 50 mg/l of silicon. The addition of silicon as a supplement was responsible for more chitin production which produced more biodiesel. It was also observed that the rate of biodiesel production was maximum at 900C.
(PDF) Effect of Phosphate on Growth and Lipid (Tag) Production in Fresh Water Diatoms. Available from: https://www.researchgate.net/publication/341902483_Effect_of_Phosphate_on_Growth_and_Lipid_Tag_Production_in_Fresh_Water_Diatoms [accessed Jun 04 2020].
... Symbols correspond to the exact location where CMs were found. Colour-cast provinces indicate the presence of CMs, whereas white provinces correspond to absence owing to lack of data; the grid indicates Longhurst's biogeographical provinces (Supporting Information Appendix S1, Table S1.2) (a) (b) smaller size fractions within the plankton (Edwards, Johns, Leterme, Svendsen, & Richardson, 2006;Gifford & Caron, 2000). The resultant distorted picture of plankton composition across the oceans (Biard et al., 2016) is typified by, for example, survey data from the historic Continuous Plankton Recorder (CPR), a device best suited (designed) for sampling mesozooplankton and larger (> 250 µm in size) robust phytoplankton . ...
Aim
Most protist plankton are mixotrophic, with potential to engage in photoautotrophy and phagotrophy; however, the ecology of these organisms has been misdiagnosed for over a century. A large proportion of these organisms are constitutive mixotrophs (CMs), with an innate ability to photosynthesize. Here, for the first time, an analysis is presented of the biogeography of CMs across the oceans.
Location
Global marine ecosystems.
Time period
1970–2018.
Major taxa studied
Marine planktonic protists.
Methods
Records for CM species, primarily from the Ocean Biogeographic Information System (OBIS), were grouped by taxonomy and size to evaluate sampling efforts across Longhurst's oceanic provinces. Biases were evaluated through nonparametric tests and multivariate analysis. Biogeographies of CMs from OBIS data were compared with data from studies that specifically targeted these organisms.
Results
Constitutive mixotrophs of different taxonomic groups, across all size ranges, are ubiquitous. However, strong database biases were detected with respect to organism size, taxonomic groups and region. A strong bias was seen towards dinophytes. Species < 20 µm, especially non‐dinophytes, were least represented, with their recorded distribution limited to coastal regions and to temperate and polar seas. Studies specifically targeting these organisms revealed their distribution to be much wider. Such biases are likely to have occurred owing to a failure to capture and correctly identify these organisms in routine sampling protocols.
Main conclusions
Constitutive mixotrophs are dominant members of organisms traditionally termed “phytoplankton”. However, lack of routine protocols for measuring phagotrophy in “phytoplankton” protists has led to widespread misrepresentation of the fundamental nature of marine planktonic primary producers; most express both “animal‐like” and “plant‐like” nutrition. Our results have implications for studies of the global biogeography of plankton, of food web dynamics (including models) and of biogeochemical cycling in the oceans.
... CPR). Lugol's iodine solution (commonly used for phytoplankton and PZP) avoids this issue but does not allow long-term storage of samples (Gifford and Caron, 2000). ...
Protozooplankton (PZP) (here size range: 12–200 μm) are rarely sampled over a broad scale, especially in ecosystem monitoring programs, despite their trophodynamic importance as grazers in the microbial loop and as prey for larger zooplankton and early life stages of fish. In this study we sampled PZP from Dutch, French, German and Norwegian research vessels taking part in the annual ICES coordinated International Bottom Trawl Survey (IBTS) which provides data on fish stock abundances and status for the entire North Sea. The abundance, biomass, composition and distribution of PZP were examined at 39 stations across the North Sea (from 3.2°W to 7.6°E and 50.5 to 59.8°N) in mid-winter (January–February 2014), a period of the year which is under-investigated so far. Twenty four taxa of dinoflagellates and ciliates were identified. Two groups comprised 89% of the total abundance of PZP: Gymnodinium spp. and other athecate dinoflagellates (68%) and Strombidium spp. and other naked ciliates (21%). The biomass of PZP at each station ranged between 0.08 and 2.4 μg C L⁻¹, which is much lower than that reported for spring or summer (≥100 μg C L⁻¹) in the North Sea. Relatively small-sized (<40 μm) PZP contributed 46% of the total biomass. No significant spatial pattern in the composition of the PZP community was found, although the total abundance of tintinnids was highest in the southern North Sea, an important over-wintering area for marine fish larvae. Using this fish survey (IBTS) as a sampling platform allowed us to obtain a synoptic view of the PZP community over a large area. The present collaborative effort provides an example of how existing monitoring platforms can be augmented in the future to collect relevant data and potential ecological indicators needed to advance the ecosystem-based approach to managing marine systems.
... We assumed carbon:plasma volume ratios of 0.11 pg C μm −3 for diatoms (Edler 1979), 0.3 and 0.19 pg C μm −3 for heavily thecate and athecate dinoflagellate forms (E. J. Lessard unpublished data from Gifford and Caron 2000), and 0.148 pg C μm −3 for ciliates (Ohman and Snyder 1991). ...
It is relevant to understand the processes and factors that modulate the efficiency of the carbon pump throughout the ecosystem of Patagonian fjords. Spatial variability of primary productivity and bacteria-microplankton biomass was assessed in relation to inorganic nutrients and stratification across nearshore zones of southern Patagonia (50–53°S) in austral spring 2009. Estimates of primary productivity (300–500 mg C m⁻² d⁻¹) and phytoplankton biomass (9–180 mg chlorophyll-a m⁻²) were low at offshore and inshore waters. Synergistic effects of low silicic acid concentrations and poor light penetration because of salinity-driven stratification of glacier meltwater in springtime appeared to negatively affect phytoplankton carbon biomass and primary production in this sub-Antarctic region. The knowledge of the relative importance of nutrient sources and light is especially significant for Patagonian glacier-fjord systems that are expected to receive higher freshwater inputs and will be more stratified in the future.
... The negative effects of increased phytoplankton biomass and production have been summarised by Gowen et al. (2012) associated benthic mortalities, fish kills and the loss of aquaculture production. More subtle changes include shifts in species composition and community structure (Officer & Ryther, 1980;Gillbricht, 1988;Gifford & Caron, 2000;Cadèe & Hegeman, 2002;Lancelot et al., 2006), that could, in turn alter food web structure and nutrient cycling. ...
This report reviews the current state of the science and best practice relating to the implementation of the Ecosystem Approach (EA) to managing ecosystem services in coastal waters and shelf seas. The report focuses on Irish fisheries and marine ecosystems and gives three recommendations to the Department of Agriculture and Rural Development, Northern Ireland:
(i) Fisheries management should be undertaken as part of a holistic approach to managing the human use of ecosystem services; (ii) the Department should undertake an assessment of the Irish Sea to determine: current ecological state; quantify the probability of future change in state; determine the economic consequences of any future change in ecosystem state on the sustainable use of ecosystem services; (iii) undertake further research on emergent ecosystem properties and their use in providing a holistic assessment of ecosystem structure and functioning.
... Specimens were identified to the level of order and enumerated. An average of 960 individuals was counted per sample and we estimated an enumeration error of 6.4% [Gifford and Caron, 2000]. The category copepod nauplii comprised a mix of calanoid, cyclopoid, and poecilostomatoid copepods. ...
Knowledge of the relative contributions of phytoplankton size classes to zooplankton biomass is necessary to understand food-web functioning and response to climate change. During the DEep Water formation EXperiment (DEWEX), conducted in the north-west Mediterranean Sea in winter (February) and spring (April) of 2013, we investigated phytoplankton-zooplankton trophic links in contrasting oligotrophic and eutrophic conditions. Size fractionated particulate matter (pico, nano and micro POM) and zooplankton (64 to > 4000 μm) composition and carbon and nitrogen stable isotope ratios were measured inside and outside of the nutrient rich deep convection zone in the central Liguro-Provencal basin. In winter, phytoplankton biomass was low (0.28 mg.m−3) and evenly spread among pico, nano and micro phytoplankton. Using an isotope mixing model we estimated average contributions to zooplankton biomass by pico, nano and micro POM of 28, 59 and 15% respectively. In spring, the nutrient poor region outside of the convection zone had low phytoplankton biomass (0.58 mg.m−3) and was dominated by pico/nano phytoplankton. Estimated average contributions to zooplankton biomass by pico, nano and micro POM were 64, 28 and 10% respectively, although the model did not differentiate well between pico and nano POM in this region. In the deep convection zone, spring phytoplankton biomass was high (1.34 mg.m−3) and dominated by micro/nano phytoplankton. Estimated average contributions to zooplankton biomass by pico, nano and micro POM were 42, 42 and 20% respectively, indicating that a large part of the microphytoplankton biomass may have remained ungrazed.
... Water samples (100-500 ml) for chlorophyll-a concentration determination were filtrated through GF/F filters (47 mm diameter) and kept on ice until analysis. Water samples for picoplankton determination were preserved with 2% paraformaldehyde, while nano-and microplankton water samples were preserved with 2% Lugol's iodine, following the recommendation by Gifford & Caron (2000). Copepods were collected in triplicate by surface horizontal hauls using nets of both 64 and 200 mm mesh size (0.3 and 0.6 m of diameter, respectively), with a flowmeter attached in each net; copepods were preserved with 4% Borax buffered formaldehyde. ...
A Lagrangian study was conducted in a eutrophic estuary (Guanabara Bay, Brazil) to investigate in situ plankton trophodynamics under the influence of the cold, nutrient-rich South Atlantic Coastal Water in a short-term temporal variability (scale of hours). We tested the hypothesis that the base of the plankton food web is composed of small cells and that microzooplankton is the main consumer of this assemblage. Samples of pico-, nano- and microplankton, as well as copepods, were collected during spring, when the entry of upwelling water in the Bay is commonly observed, and near the surface every 3 h during the 1-day sampling period. Potential predation of dinoflagellates, ciliates, copepod nauplii, copepodites and adult copepods was estimated based on predator-prey size relationships. The main trophic links in the Guanabara Bay food web for the period analysed were nanophytoplankton-copepods, nanophytoplankton-ciliates, and autotrophic dinoflagellates-heterotrophic dinoflagellates. According to microphytoplankton availability, adult copepods could not satisfy their food requirement, and nanophytoplankton represented an important supplementary food source. In fact, diel variations of nano- and microplankton biomass were opposite to that of copepods suggesting predation control by the latter on the former. The trophodynamics of Guanabara Bay, under the influence of upwelling water, resulted in marked differences from other eutrophic estuaries around the world.
... Prey were quantified using a Coulter Counter, facilitating rapid enumeration of the abundant small, spherical cells at the study site and avoiding laborious microscopy methods which may also underestimate cells that do not preserve well or which have low levels of autofluorescence (Gifford and Caron, 2000). Flow cytometry, while useful for differentiating phytoplankton from other suspended particles (Cucci et al., 1985;Sieracki et al., 2005), would not provide accurate sizing information for mixed prey populations, and would require preservation and staining of samples to evaluate heterotrophic biomass in the samples. ...
Copepod naupliar grazing estimates often appear to represent an insignificant fraction of prey community mortality, despite high naupliar abundances and weight-specific ingestion rates. To address this seeming paradox, the impact of incubation time on grazing by nauplii of the subtropical copepod Parvocalanus crassirostris on natural prey assemblages was evaluated. Measurements of prey removal during feeding experiments were taken every 6-h over a 24-h period during two experiments (E1, E2), where the initial 2–35 μm natural prey biomass differed by 3-fold, i.e., 66 μg C L− 1 (E1) vs. 198 μg C L− 1 (E2). Results showed that total prey ingestion rate estimates decreased over the course of incubation by up to 75% after 24-h, with highest ingestion rates obtained during the initial 6-h. In no predator controls, total prey biomass also decreased significantly during the 24-h incubation particularly in the smallest prey size groups despite the absence of nauplii, and positive non-significant trends were observed in prey > 10 μm in the experiment with higher initial prey abundances. Predator density effects in this experiment provided additional evidence for trophic cascades. Results of this work suggest that in communities with rapidly changing natural prey assemblages and predators with short development times, short incubations minimize bottle effects and reduce the risk of measuring grazing rates on prey communities that no longer resemble the in situ populations.
... Microeukaryotes are a group of extremely diverse organisms that possess a wide range of distinct morphologies (Caron et al. 2012;Landry and Calbet 2004;Sherr and Sherr 1994), physiologies, and links to higher trophic levels (Caron et al. 2012;Bik et al. 2012;Calbet and Saiz 2005). Very few studies have attempted to identify and enumerate all protist taxa because of their complexities (Caron et al. 2009;Gifford and Caron 2000;Tomas and Haste 1997). Therefore, it is still uncommon to delineate microeukaryotic species based on their genetic signatures. ...
To investigate the differences in the microbial community composition and assembly process in two lake zones (Meiliang Bay (MLB) and Xukou Bay (XKB) in Taihu Lake, China) with different nutrient loadings, water samples were collected. Both the 16S ribosomal RNA (rRNA) gene for the bacterial community and the 18S rRNA gene for the microeukaryote community were investigated using the Illumina second-generation sequencing platform (2 × 250 paired-end). The results indicated that both the bacterioplankton and microeukaryote community composition derived from the two lake zones were significantly different. Significantly higher operational taxonomic unit (OTU) richness (P < 0.01) and phylogenetic diversity (P < 0.05) were found for the bacterioplankton community of MLB. However, a comparable alpha diversity was found between the microeukaryote communities of MLB and XKB (P > 0.05). Environmental factors significantly affected the community compositions in XKB for both the bacterioplankton and microeukaryotes. However, they did not significantly influence the microbial community composition in MLB, except for a weak correlation between dissolved organic carbon (DOC) and the microeukaryote community. The microbial communities tended to be more phylogenetically clustered than expected by chance in the two lake zones. Moreover, the results of the phylogenetic structure suggest that deterministic processes played overwhelming roles in driving the assembly of both the bacterioplankton and microeukaryote community in XKB.
... Ceratium sp.) followed by ciliates (naked and with lorica) were most abundant. A cautionary note refers to the use of neutral formaldehyde as fixative for microzooplankton, which may work best for micro-crustaceans (i.e., copepod eggs and nauplii, small cladocerans, other) but may result in lower abundance estimates for taxa like ciliates (Gifford and Carson, 2000). Consequently, the total amount of ciliates could have been even higher than the figures here reported. ...
... Ciliate communities were examined in samples fixed with strong acid Lugol's solution (Edler 1979; stock solution: 5% iodine, 10% potassium iodide, 10% v/v glacial acetic acid; 1-2 ml of stock solution was added to 200 ml sample) with the standard Utermöhl method (Hasle 1978). Acid Lugol's solution was chosen as the fixative, because it does not cause loss of protozoan cells, which means it is the best fixative for quantitative studies of ciliates Leakey et al. 1994a;Gifford & Caron 2000). The specimens were identified according to Marshall (1969), Foissner & Berger (1996, Patterson & Hedley (2003), and other guides. ...
In aquatic environments, ciliates integrate the energy flowing through bacteria, smaller protozoa, and the prevailing fraction of algae and are further grazed upon by metazooplankton. Ciliates are incorporated into budgets and models describing ecosystem functioning. However, data for the parameterization and validation of models remain insufficient. In this study, annual production to biomass (P/B) ratios of pelagic ciliates were estimated in four lakes of different trophic status and at two sites located in the coastal zone of the Baltic Sea. All study sites were located in the temperate zone. The calculations were based on bulk data reflecting seasonal changes in ciliate production, which was estimated using an allometric equation. The annual ciliate P/B ratio for surface waters was 308 ± 81 yr-1 (mean ± standard deviation). There was no statistically significant relationship between the mean annual ciliate biomass in particular water bodies and the annual P/B ratio. In the near-bottom waters, the annual P/B ratio was 78 ± 39 yr-1. Because of the possible food limitation of ciliate growth and reconstructions of the community due to changes in environmental conditions, the ciliate P/B ratio applied in models of temperate waters should range from 50% to 100% of the P/B ratios estimated in this study.
... For counting microzooplankton (dinoflagellates, ciliates and crustacean nauplii), 10 to 30 l of seawater from different depths (0, 5, 10, 25 and 50 m) were filtered gently through a sieve (10 µm mesh size), then concentrated to a final volume of ~100 ml and preserved with buffered formalin (5% final concentration). Carbon:plasma volume ratios of 0.30 and 0.19 pg C µm −3 were used for heavily thecate and athecate dinoflagellate forms, respectively (Gifford & Caron 2000), and 0.148 pg C µm −3 was applied for ciliates (Ohman & Snyder 1991). ...
The southernmost Patagonian region constitutes a major glaciered area with a high freshwater input loaded with particulate and dissolved matter. We assessed the relevance of the terrestrial (allochthonous) and marine (autochthonous) matter that permeates into the fjord and channel system and their possible impact on the euphausiid-based food web. A research cruise (CIMAR 16) was conducted from 18 October to 13 November 2010 (austral spring) in the area between Magellan Strait and Drake Passage to study the physical-chemical and biological characteristics of the pelagic food web, as well as the main biological processes linked with the food web. The dominance of phytoplankton within the autochthonous fractions of particulate organic carbon (POC) and the high abundance and bacterivory rate shown by the heterotrophic nanoflagellates suggest an interplay between microbial and classical food webs. Euphausia vallentini showed a moderate grazing impact (3% of the gross primary production) and a daily ration of 18.6%, and the fecal pellet production rate corresponded to 24.5% of the ingestion rate. This species removed heterotrophic prey (67.5%) preferentially over diatoms (32.5%), and the ingested diet was mainly dinoflagellates, tintinnids, crustacean nauplii and centric diatoms. Overall, euphausiids fed preferentially on marine matter, which showed a tight link with the pelagic food web. Congeneric species of the genus Euphausia shared the condition of 'key species' as they constitute a major carbon and energy flow from lower to higher trophic levels and an important part of the POC flux through their active vertical migration and passive fecal-carbon export.
... Prior to identification, zooplankton samples were stained with Rose Bengal for 24 h (Goswami 2004;Thiel and Sauer 1995). Identification of zooplankton was conducted by taking 25 % of the overall sample and counting all of the organisms within the subsample in a Bogorov counting chamber under a dissecting microscope (Leica M80, Illinois, USA) at 960 magnification (Gifford and Caron 2000;Goswami 2004;USEPA 2003). This procedure generally ensured that plankton counts exceeded the required 48 individuals to achieve acceptable precision levels according to published methodology (Postel et al. 2000). ...
Synthetic surfactants in cleaners and detergents commonly contaminate freshwater systems, therefore use of low-toxicity alternatives is becoming increasingly important. Alkyl polyglucosides (APGs) derived from natural products are less toxic than synthetic surfactants, and degrade rapidly reducing chemical exposure time. However, single species toxicity tests showed APGs have toxic effects on aquatic primary producers and zooplankton, and that species demonstrate different sensitivities to APGs. Furthermore, species unaffected by APGs directly may be indirectly affected by removal of a food source or changes in predator densities, thereby changing plankton community structure. To determine the effects of APGs on plankton communities under environmental conditions, floating mesocosms were deployed in a shallow pond in southeast Georgia, USA and dosed with 0, 0.01, 2.5, 5, or 10 mg L−1 APG. Zooplankton community composition and abundance, phytoplankton abundance (as chlorophyll a), and water column dissolved oxygen concentration were determined weekly for 1 month. Zooplankton abundance decreased primarily due to loss of copepods, and community composition shifted toward small-bodied cladocerans (Bosmina sp.), and chlorophyll a concentrations declined by up to 81 % following exposure to APG concentrations of 2.5 mg L−1 or greater. Concentrations of dissolved oxygen never dropped below 5.70 mg L−1, but the observed declines of ~2 mg L−1 could become stressful during periods of high water temperatures. Nevertheless, the APG-induced shift from copepod to cladoceran dominated communities and decrease in autochthonous carbon availability has important implications for food availability and quality to higher trophic levels such as planktivorous fishes.
... For the experiments, cells were harvested during the late exponential growth phase (18- d after inoculation) by centrifuging at 2500Â g 10 min. Culture-cell density was determined by counting in Sedgwick-Rafter chamber 1801-A10 model (Cole-Parmer, Vernon Hills, U.S.A.) after cell fixation with Lugol's solution (Gifford and Caron, 2000 ) under an optical microscope Olympus BX41 (Olympus, Tokyo, Japan). The Isochrysis galbana (strain ISG-1) was provided by CIBNOR Live Food Laboratory at La Paz BCS, Mexico. ...
... Specimens were identified to the level of order and enumerated. An average of 960 individuals were counted per sample and we estimated an enumeration error of 6.4 % (Gifford and Caron, 2000). The category copepod nauplii comprised a mix of calanoid, cyclopoid, and poecilostomatoid copepods. ...
In oligotrophic tropical and subtropical oceans, where strong stratification
can limit the replenishment of surface nitrate, dinitrogen (N2)
fixation by diazotrophs can represent a significant source of nitrogen (N)
for primary production. The VAHINE (VAriability of vertical and tropHIc
transfer of fixed N2 in the south-wEst Pacific) experiment was designed to
examine the fate of diazotroph-derived nitrogen (DDN) in such ecosystems. In
austral summer 2013, three large ( ∼ 50 m3) in situ mesocosms were
deployed for 23 days in the New Caledonia lagoon, an ecosystem that typifies
the low-nutrient, low-chlorophyll environment, to stimulate diazotroph
production. The zooplankton component of the study aimed to measure the
incorporation of DDN into zooplankton biomass, and assess the role of direct
diazotroph grazing by zooplankton as a DDN uptake pathway. Inside the
mesocosms, the diatom–diazotroph association (DDA) het-1 predominated during
days 5–15 while the unicellular diazotrophic cyanobacteria UCYN-C
predominated during days 15–23. A Trichodesmium bloom was observed in the lagoon (outside
the mesocosms) towards the end of the experiment. The zooplankton community
was dominated by copepods (63 % of total abundance) for the duration of
the experiment. Using two-source N isotope mixing models we estimated a mean
∼ 28 % contribution of DDN to zooplankton nitrogen biomass
at the start of the experiment, indicating that the natural summer peak of
N2 fixation in the lagoon was already contributing significantly to the
zooplankton. Stimulation of N2 fixation in the mesocosms corresponded
with a generally low-level enhancement of DDN contribution to zooplankton
nitrogen biomass, but with a peak of ∼ 73 % in mesocosm 1
following the UCYN-C bloom. qPCR analysis targeting four of the common
diazotroph groups present in the mesocosms (Trichodesmium, het-1, het-2, UCYN-C)
demonstrated that all four were ingested by copepod grazers, and that their
abundance in copepod stomachs generally corresponded with their in situ abundance.
15N2 labelled grazing experiments therefore provided evidence for
direct ingestion and assimilation of UCYN-C-derived N by the zooplankton,
but not for het-1 and Trichodesmium, supporting an important role of secondary pathways
of DDN to the zooplankton for the latter groups, i.e. DDN contributions to
the dissolved N pool and uptake by nondiazotrophs. This study appears to
provide the first evidence of direct UCYN-C grazing by zooplankton, and
indicates that UCYN-C-derived N contributes significantly to the zooplankton
food web in the New Caledonia lagoon through a combination of direct grazing
and secondary pathways.
... At least 30 organisms were measured for each morphotype to calculate their biovolumes by comparing their forms to those of standard geometrical bodies (Hillebrand et al., 1999). The factor 190 fg C µm –3 for the Lugol's iodine-fixed samples (Putt and Stoecker, 1989) was employed to calculate the biomass from the biovolume because this factor considers the ciliate shrinkage of the fixed samples (Gifford and Caron, 2000 ). The ciliate biomasses were further divided into total ciliates and nanociliates. ...
The recent interest in the plankton structures and dynamics in tropical and subtropical lakes has revealed important trends that set these lakes apart from temperate lakes, and one of the main differences is the enhanced importance of the microbial food web with respect to net plankton. Ciliates are a key component of subtropical and tropical microbial webs because of their role as dominant picoplankton grazers and their ability to channel picoplankton production to the uppermost trophic levels. Plankton ciliates have been found to play a crucial role in the survival of fish larvae in lakes that share several features with Lake Catemaco, a eutrophic tropical Mexican lake. Therefore, the plankton ciliate composition, abundance, and biomass of Lake Catemaco were studied to assess their role in the microbial food web. The data were obtained from surface and bottom water samples collected at eleven points during three surveys in 2011 and an additional survey in 2013, with the surveys covering the local climatic seasons. The most abundant components of the plankton ciliate assemblages were small prostomatids (Urotricha spp.), choreotrichs (Rimostrombidium spp.), cyclotrichs (Mesodinium and Askenasia), and scuticociliates (Cyclidium, Cinetochilum, Pleuronema, and Uronema). Other important ciliates in terms of abundance and/or biomass were haptorids (Actinobolina, Belonophrya, Monodinium, Paradileptus, and Laginophrya), Halteria, oligotrichs (Limnostrombidium and Pelagostrombidium), Linostomella, Bursaridium, Cyrtolophosis, and Litonotus. The ciliate abundance averaged 57 cells mL-1 and ranged from 14 to 113 cells mL-1. The mean ciliate biomass was 71 µg C L-1 and ranged from 10 to 202 µg C L-1. Differences were not detected in ciliate abundance or biomass between the sampling points or sampling depths (surface to bottom); however, significant differences were observed between seasons for both variables. Nano-sized filamentous cyanobacteria were the most abundant component of the plankton, and their abundance was assessed through epifluorescence microscopy counts. The autotrophic and heterotrophic picoplankton abundance was measured through epifluorescence, and their abundance and biomass were higher at the study site relative to other shallow freshwater ecosystems. The total ciliate biomass distribution patterns were similar to those of filamentous cyanobacteria and autotrophic or heterotrophic picoplankton, although the nanociliate biomasses peaked when the picoplankton and filamentous cyanobacteria were least abundant. The consequences of this increased importance of ciliates on the structure of the plankton at Lake Catemaco will be discussed along with the probable causes.
... I. galbana was obtained from the Live Food Laboratory at CIBNOR and used as nontoxic diet in the control (Gerdes 1983;Bougrier, Hawkins & H eral 1997). The dinoflagellate cell concentration, in both cultures and feeding experiments was determined by cell counts in Sedgwick–Rafter counting slides and Neubauer chamber (0.1 mm in depth) after fixation with Lugol's solution (Gifford & Caron 2000) with an optical microscope. For bioassays, cells were harvested by centrifuge (800 x g for 10 min) on the late exponential growth phase (L opez-Cuevas 2009) and adjusted to the required concentrations for each case with sterile seawater. ...
This is the first report providing information at molecular level on C. gigas response to dinoflagellate blooms.
... For the bioassays, cells were harvested during the late exponential growth phase by centrifugation at 2500 Â g for 10 min 19 d after inoculation (Band-Schmidt et al., 2005). Culture-cell density was determined by counting in Sedgwick-Rafter chambers after cell fixation with Lugol's solution (Gifford & Caron, 2000) under an optical microscope (Olympus BX41, Tokyo). ...
The harmful alga Gymnodinium catenatum is one of the species that produces the neurotoxic, hydrophilic, tetrahydropurine derivatives known as paralytic shellfish
toxins (PST). Studies have shown that several classes of marine toxins have genotoxic effects on bivalves. However, there
are few studies on PST and their genotoxic effects on bivalves such as oysters. Experiments were performed to assess the effects
of the toxic dinoflagellate G. catenatum on changes in the transcription level of the genes involved in cell-cycle regulation (p21, p53, cafp55) and initial inflammatory (casp1) processes and injuries in tissues of juvenile Crassostrea gigas. Our results reveal an effect at the level of transcription. The high transcription levels of the p21 and p53 genes found in oysters exposed to dinoflagellate diets suggest an activation of the cell-cycle checkpoints by DNA damage
induction. At the histological level, the oysters exposed to the toxic dinoflagellate showed exfoliation, epithelial rupture
and inflammation, which correlate with the observed changes in expression level of casp1 that is known to play a role in initial inflammatory responses. Our results provide molecular data suggesting probable DNA
damage through expression modulation of the analysed key genes, in addition to histological evidence of tissue injuries due
to PST dinoflagellate exposure.
... Plasma volumes were calculated (Edler, 1979) and averaged from a minimum of 50 ind/species. Carbon to plasma volume ratios of 0.11 pgC µm -3 for diatoms (Edler, 1979), 0.3 and 0.19 pgC µm -3 for heavily thecate and athecate dinoflagellates forms respectively (Gifford & Caron, 2000) were applied. An analysis of similarities (ANOSIM) based upon Bray-Curtis distances between river and coastal phytoplankton assemblages was conducted for each sampling campaign considering the mean surface biomass for river and coastal stations, respectively, by using the software Statistica. ...
The Biobío River in central Chile is the third largest watershed and second largest river in Chile in terms of discharge volume. Three sampling campaigns were made in the lower reaches of the river and the adjacent coastal ocean to evaluate the influence of the river plume on the physical/chemical conditions and the abundance/biomass of microphytoplankton during autumn-winter conditions. In addition, a preliminary quantification of riverine nutrients, dissolved silica, and phytoplankton carbon flux to the adjacent ocean was also conducted. High nitrate (NO3-) and silicic acid (Si(OH)4) concentration (>18 and 50 μM, respectively) was observed in the lower reaches of the river during all field campaigns. Si(OH)4 was even high in surface river plume waters. Hydrographic conditions indicate that river plume waters were piled coastward, and they could drove to the south at the Arauco Gulf. In all sampling, highest microphytoplankton biomass (>5000 μgC m-3) was associated to the lower reaches of the river and river plume waters as they were moving southward. During autumn-winter conditions a significant flux of phytoplankton carbon and nutrients to the adjacent coastal ocean also played an important role in the high biological productivity of this coastal upwelling area. These preliminary results evidence the need to conduct large-term studies, which should consider the importance of these allochthonous carbon sources in global carbon budgets and coastal food-web models.
... Pour toutes ces raison, nous avons fixé nos échantillons avec du chlorure de mercurique qui est moins destructif mais en revanche plus coûteux et fortement toxique (Pace & Orcutt, 1981 ;Stocker et al., 1994). Les échantillons (200 ml) sont stockés à l'obscurité à 4°C avant le dénombrement en microscopie inversée selon la méthode d'Utermöhl (1958) à l'aide du microscope inversé (Hasle, 1978 ;Gifford & Caron, 2000). On laisse sédimenter pendant 2h un volume de 10 à 20 ml de l'échantillon qui est ensuite observé au microscope inversé (grossissement: 400X). ...
A multi approach study, using geophysics, tracing tests, water balance, geology, hydrogeology and statistics analyses on physico-chemicals data, shows (1) leachate's infiltrations between 31 and 43% accross a shaly natural interface and superior to 45% accross an artificial geomembrane interface and (2) a localized physico-chemical impact on the existing piezometer network. Collected leachates are treated by a natural lagooning system. After the suspension of waste deposits, biodegradation activity reduces and generates a decrease in leachates noxiousness, thus changing the lagoons hydrobiologic mechanisms. We note a diversification of all the microbial loop components allowing the re-use of the organic material. The new trophic pyramid organization allowed to attain a viable ecosystem for fish fauna, in the last lagoon. Treated leachates undergo a second purification by natural attenuation in the receiving stream. A bacteriological approach on leachates, lagoons and groundwater quality allowed to assess presence and survival of faecal bacteria in these various environments. This landfill doesn't represent an important source of faecal bacteria. This studied site, where landfill's leachates and septic tank sewage are mixed together, confirms the use of Escherichia coli and Entoroccocus as markers of recent faecal contaminations. The shaly aquifer resembles more in a fractured area than in an impervious zone, with a preferential circulation along cracks and fractures which doesn't assure the natural filtration and lead to a vulnerable aquifer to bacterial contaminations.
Acantharia (Acantharea) are wide-spread marine protozoa, presenting one of the rare examples of strontium sulfate mineralization in the biosphere. Their endoskeletons consist of 20 spicules arranged according to a unique geometric pattern named Müller's principle. Given the diverse mineral architecture of the Acantharia class, we set out to examine the complex three-dimensional skeletal morphology at the nanometer scale using synchrotron X-ray nanotomography, followed by image segmentation based on deep learning methods. The present study focuses on how the spicules emanate from the robust central junction in the orders Symphyacanthida and Arthracanthida, the geometry of lateral spicule wings as well as pockets of interspicular space, which may be involved in cell compartmentalization. Through these morphometric studies, we observed subtle deviations from the previously described spatial arrangement of the spicules. According to our data, spicule shapes are adjusted in opposite spicules as to accommodate the overall spicule arrangement. In all types examined, previously unknown interspicular interstices were found in areas where radial spicules meet, which could have implications for the crystal growth mechanism and overall endoskeletal integrity. A deeper understanding of the spiculogenesis in Acantharia can provide biomimetic routes towards complex inorganic shapes. STATEMENT OF SIGNIFICANCE: Morphogenesis, the origin and control of shape, provides an avenue towards tailored inorganic materials. In this work, we explored the intricate skeletal organization of planktonic Acantharia, which are amongst the few strontium sulfate biomineralizing organisms in nature. By using nanoscale X-ray imaging and deep learning image segmentation, we found deviations from previously described geometric patterns and undiscovered skeletal features. The bio-inspired synthesis of inorganic materials with complex shape has important ramifications for solid-state chemistry and nanotechnology.
Molecular analysis is a common tool for marine ecological and biological research. For genomic analysis of zooplankton, ethanol preservation and freezing are often used to preserve samples until analysis. However, these methods have disadvantages, such as the loss of morphological information. Recently, 10% Lugol’s iodine solution (10% Lugol) has been shown to be an effective preservative of plankton samples for molecular analysis, even after 18 months. However, that study only reported a PCR-based molecular study using copepods. We tested the preservation effectiveness of 10% Lugol on various zooplankton over 33 months by comparing them to samples preserved by freezing or in 5% formalin seawater. The results revealed that the total amounts of DNA extracted from crustacean and gelatinous zooplankton preserved in 10% Lugol were the same or higher than those preserved in formalin or by freezing. Gel electrophoresis of the extracted DNA indicated that the DNA of the samples preserved in 10% Lugol was not fragmented during the preservation period. PCR amplification of a partial 18S rRNA gene using DNA extracted from various zooplankton taxa (siphonophores, copepods, ostracods, doliolids, polychaetes, pteropods, euphausiids, and chaetognaths) was successful. Sequences of morphologically identified species preserved in 10% Lugol had BLAST hits to sequences of these species deposited in Genbank, with a similarity of 100%, which indicated there was no sequence alteration during the preservation period. Thus, we conclude that 10% Lugol is a suitable preservative for molecular analysis of various zooplankton taxonomic groups.
Plankton ecologists ultimately focus on forecasting, both applied and environmental outcomes. We review how appreciating planktonic ciliates has become central to these predictions. We explore the 350-year old canon on planktonic ciliates and examine its steady progression, which has been punctuated by conceptual insights and technological breakthroughs. By reflecting on this process, we offer suggestions as to where future leaps are needed, with an emphasis on predicting outcomes of global warming. We conclude that in terms of climate change research: i. climatic hotspots (e.g., polar oceans) require attention; ii. simply adding ciliate measurements to zooplankton/phytoplankton-based sampling programs is inappropriate; iii. elucidating the rare biosphere’s functional ecology requires culture-independent genetic methods; iv. evaluating genetic adaptation (microevolution) and population composition shifts is required; v. contrasting marine and freshwaters needs attention; vi. mixotrophy needs attention; vii. laboratory and field studies must couple automated measurements and molecular assessment of functional gene expression; viii. ciliate trophic diversity requires appreciation; and, ix. marrying gene expression and function, coupled with climate change scenarios is needed. In short, continued academic efforts and financial support are essential to achieve the above; these will lead to understanding how ciliates will respond to climate change, providing tools for forecasting.
The northwestern Pacific Ocean and East China Sea (ECS) are frequently affected by typhoons during the summer period. To identify changes in production and consumption rates of phytoplankton (<20 and 20~200 µm) affected by Typhoon Maria (9-10 July 2018), 2 sampling periods were compared: a pre-typhoon cruise (4-9 July 2018) and a post-typhoon cruise (13-17 July 2018). Results showed that <20 and 20~200 µm phytoplankton production was 14- and 1.8-fold higher, respectively, in the post-typhoon period compared to the pre-typhoon. Accompanying this post-typhoon shift from pico- and nanophytoplankton to microphytoplankton, the consumption rate of microzooplankton on <20 µm phytoplankton was 11.6 mgC m ⁻³ d ⁻¹ in the pre-typhoon period, and increased to 203.3 mgC m ⁻³ d ⁻¹ after the typhoon. Furthermore, the ingestion fluxes were 4.9 and 8.0 mgC m ⁻³ d ⁻¹ through mesozooplankton grazing on microzooplankton (ciliates and dinoflagellates) pre- and post-typhoon, respectively. Our findings show that organisms from the microbial food web (i.e. ciliates and dinoflagellates) may control the phytoplankton assemblage during the post-typhoon period of increased productivity, and thus represent an important trophic link between the classical and microbial food webs in the southern ECS.
Монография посвящена изучению прибрежных морских экосистем северо-
восточного шельфа Черного моря, включая зоны интенсивного судоходства, рекреации,
Керченский пролив и Азовское море, подверженных высокому уровню антропогенного
загрязнения. Приводятся результаты исследований гетеротрофного бактериопланктона,
простейших (зоофлагеллят, инфузорий), голопланктона, меропланктона, ихтиопланкто-
на. Разработаны энергетические трофодинамические модели экосистем. Выявлены об-
щие и специфические особенности их трансформации под воздействием интенсивного
антропогенного воздействия. Показана роль зоопланктона в структурно-функциональной
организации таких экосистем.
Предназначена для гидробиологов, экологов, океанологов, преподавателей и сту-
дентов вузов соответствующих специальностей.
The monograph is devoted researches of coastal marine ecosystems of the northeastern
Black Sea, including zones of intensive shipping, recreation, the Kerch strait and the Sea of
Azov exposed to anthropogenic impact. Results of research of heterotrophic bacteria, protozoan,
holoplankton, meroplankton, ichthyoplankton are presented. Trophodynamic models of
port ecosystems have been developed. Common and specific features of their transformation
under the influence of intensive anthropogenous impact are revealed. Role of zooplpankton in
structurally functional organization of such ecosystem has been shown.
The book is addressed to hydrobiologists, oceanologists, teachers and students of institutes
of higher education.
Heterotrophic flagellates contribute significantly to the matter flux in aquatic and terrestrial ecosystems. Still today their quantification and taxonomic classification bear several problems in field studies, though these methodological problems seem to be increasingly ignored in current ecological studies. Here we describe and test different methods, the live-counting technique, different fixation techniques, cultivation methods like the liquid aliquot method (LAM), and a molecular single cell survey called aliquot PCR (aPCR). All these methods have been tested either using aquatic field samples or cultures of freshwater and marine taxa. Each of the described methods has its advantages and disadvantages, which have to be considered in every single case. With the live-counting technique a detection of living cells up to morphospecies level is possible. Fixation of cells and staining methods are advantageous due to the possible long-term storage and observation of samples. Cultivation methods (LAM) offer the possibility of subsequent molecular analyses, and aPCR tools might complete the deficiency of LAM in terms of the missing detection of non-cultivable flagellates. In summary, we propose a combination of several investigation techniques reducing the gap between the different methodological problems.
Sympagic microzooplankton were studied during late winter in the northern Weddell Sea for diversity, abundance and carbon biomass. Ice cores were collected on an ice floe along three dive transects and seawater was taken from under the ice through the central dive hole from which all transects were connected. The areal and vertical microzooplankton distributions in the ice and water were compared. Abundance (max. 1300 ind. l ⁻¹ ) and biomass (max. 28.2 µg C l ⁻¹ ) were high in the ice cores and low in the water below the sea ice (max. 19 ind. l ⁻¹ , 0.15 µg C l ⁻¹ , respectively). The highest abundances were observed in the bottom 10 cm of the ice cores. The microzooplankton community within the sea ice comprised mainly aloricate ciliates, foraminifers and micrometazoans. In winter, microzooplankton represent an important fraction of the sympagic community in the Antarctic sea ice. They can potentially control microalgal production and contribute to particulate organic carbon concentrations when released into the water column during the ice melt in spring. Continued reduction of the sea ice may undermine the roles of microzooplankton, leading to a reduction or complete loss of diversity, abundance and biomass of these sympagic protists.
The article examines the trophic relationships of mesozooplankton in coastal and estuarine systems. The first half of the article focuses on zooplankton feeding, including diet, nutrition, and feeding on toxic algae. The influence of diet on growth, reproduction, and secondary production is also covered. The second half of the article examines mesozooplankton as prey items for fish, gelatinous zooplankton, and other invertebrates. Finally, future directions of mesozooplankton research in neritic systems are presented.
1 - The quali-quantitative analysis of phytoplankton guild is usually carried out according to the method of Uthermöl (or sedimentation method), but in each step can be present a component of error that can affect the reliability of the final result, from sampling to data analysis. 2 - The following work is intended to focus attention on an important aspect of the phytoplankton analysis: the fixation, with the aim of assessing the effect of two chemical fixatives, formalin and Lugol's solution, on the taxonomic composition and size structure of phytoplankton guilds. Accordingly, water samples were collected from three different water bodies, coastal marine area facing the Alimini Lake (Southern Adriatic Sea), transitional water (Alimini Grande Lake) and freshwater (Fontanelle Lake). The three water bodies are characterized by a different taxonomic structure of phytoplankton guilds due to difference in chemical-physical and hydrodynamic conditions. 3 - The samples were fixed and then analyzed according to a monthly time series for a period of 125 days. 4 - This study clearly shows that do not exist a better fixative, but on the basis of the phytoplankton classes observed in a sample we could prefer one of the two fixative.
Protozoa are an important component of both the nano- and microplankton in marine and freshwater environments and are preyed upon by zooplankton, including suspension-feeding cope pods, some gelatinous zoopiankters and some first-feeding fish larvae. The clearance rates of suspension-feeding zooplankton for ciliates, in particular, are higher than for most phytoplankton. For at least some suspension-feeding zooplankton, protozoans are calculated to be quantitatively an important component of the diet during certain seasons. In laboratory studies, protozoan components in the diet appear to enhance growth and survival of certain life-history stages or enhance fecundity. These data suggest that protozoans are qualitatively as well as quantitatively important in the diets of marine zooplankton. Most studies of predation on Protozoa have focused on the euphotic zone in nearshore waters. Predation on Protozoa is expected, however, to be particularly important both quantitatively and qualitatively in marine environments and seasons in which primary production is dominated by cells <5 μm in size, such as nearshore environments after the spring phytoplankton bloom, in oligotrophic waters, and in environments dominated by detritus-dominated food webs, such as the deep sea. In detritus-dominated food webs, Protozoa may be a source of essential nutrients and may thus facilitate utilization of bacterial and detrital carbon by metazoan plankton.
The bioenergetics of growth of 6 species of heterotrophic (bacterivorous) microflagellates was studied in batch cultures. Maximum growth rates varied between 0.15 and 0.25 h-' among the species, but growth as slow as 0.028 h-' could be maintained. Yield (gross growth efficiency) was found to be ca. 30 % (volume) or, in 2 cases, 34 and 43 % (C basis) respectively; net growth efficiency (C) was 60 %. Respiratory and growth rates were directly proportional to consumption rate within the range of growth rates studied. Clearance (volume of water cleared for bacteria per unit time and measured in fractions of cell volume) ranged from about 5 X 104 to about 106 h-'; this large variation can in part be explained as a consequence of specialization to different food particle slzes. In general, the parameter values suggest that the type of flagellates studied may grow on and possibly control the concentration of bacteria found in marine plankton.
Stimulated by studies from marine waters there is now increasing evidence that the components of the microbial food web contribute to the pelagic flux of matter as significantly in freshwater environments as they do in the ocean. Up to now generally only heterotrophic nanoflagellates and ciliates have been quantitatively considered among limnetic protozooplankton. Our investigations using a special live-counting technique showed that large heterotrophic flagellates (LHF, >15µm; mainly chrysomonads and dinoflagellates) have been overlooked in quantitative estimations of limnetic protozooplankton biomass. We present estimations from 19 German lakes of different trophy during different seasons and from 4 rivers as well as detailed seasonal studies of a eutrophic lake and a brook indicating that LHF form a significant part (up to 5O%) of protozooplankton biomass. LHF reach highest importance in early spring when LHF are one of the most significant herbivorous component. In eutrophic running waters protozooplankton (incl. LHF) dominates by far the total zooplankton biomass. LHF doubling times lie in the range of O.2 to 2 d-1. Their abundance can be controlled by metazoan predation. LHF should be considered as significant components of limnetic food webs. This is in agreement with the present knowledge of marine pelagic ecosystems where LHF (mainly dinoflagellates) have already been recognized as an important part of the pelagic microbial web
Planktonic sarcodines have mostly been overlooked or ignored in limnological studies mainly due to methodological and taxonomical problems. However, studies which have considered sarcodines indicate that amoebae and heliozoans could be important components of limnetic plankton communities independent of trophic status and latitude of lakes investigated. Planktonic sarcodines are generally not as abundant as heterotrophic nanoflagellates, but they may be as abundant or even more abundant than ciliates - the classical protozooplankton component of lakes. The contribution of sarcodines to annual mean protozooplankton biomass seems to be only a few per cent ( 1-15%). Sporadically however, sarcodines may be a very important constituent of plankton communities. Small forms (5 to 20 µm) seem to prevail among naked amoebae and heliozoans. In some lakes planktonic testaceans (Diffugia) may be abundant. Similar to marine and estuarine systems, naked amoebae seem to be often associated to particles and aggregates and may be important functional components of lake snow. Rough estimations of the grazing impact of bacterivorous naked amoebae indicate their importance for the regulation of attached microbial communities on particles. In some cases amoeboid protists have been reported to be voracious consumers of algal blooms. Heliozoans consume autotrophic and heterotrophic nanoplankton, and omnivorous/carnivorous species have to be considered as potential grazers on other protozoans. It is suggested that planktonic sarcodines play an important role in the material flux of freshwater plankton communities as they do in marine plankton communities.
p>The seasonal abundance of ciliates and other microseston components a I t Calshot was investigated between January 1974 and March 1975. Samples were collected by pumping and were size fractionated. Ciliates were found to be present throughout the year. The standing crops of both tintinnids and naked ciliates were at a maximum in late spring; a second peak was found in the autumn for tintinnids. Thirteen species of tintinnid were found although two species, StenosWella ventricosa and Tintinnopsis beroidea, dominated the tintinnid,assemblage throughout the year. Some tintinnid species showed seasonal succession and could be divided into seasonal groups.Laboratory studies were carried out A The bacteriovorous ciliateUronema marinum. The effects of salinity, food type and temperature-on reproduction were investigated. Experiments were carried out to determine rates of consumption, growth and reproduction in relation to food concentration and temperature. I Mean cell volumes and gross growth efficiencies were also measured. Spectrophotometry, using calibration by bacterial organic carbon measurements,' was used to determine food concentration. A method was developed for separating ciliates from their food for biomass estimation using the ciliate's migratory behaviourv Models were derived for consumption, growth and reproduction based on the forcing functions of food concentration and temperature. Tentative estimates were made for the- production of naked ciliate; and 'their consumption of bacteria at Calshot by integrating the field work data with the models of consumption and growth. Estimates were also made for the production of tintinnids and their consumption of nanophytoplankton using field study data and-literature derived information on consumption and reproduction. The results obtained suggest that the grazing of bacteria by naked ciliates is negligible in proportion to bacterial standing crop and production but that tintinnids may be important' in controlling phytoplankton production.</p
It is becoming evident that, at least from the ecosystem point of view, a major ‘raison d’etre’ for planktonic protozoans is their function as agents of nutrient transfer and recycling. The term ‘nutrients’ is used here in the broadest sense and applies to carbon, nitrogen, phosphorus and perhaps to other elements despite their different potential pathways. As yet we know almost nothing about the biological cycling in aquatic systems of micronutrients such as iron, magnesium, zinc, cobalt or growth factors such as vitamins (Phillips, 1984). This paper first addresses the important role bacteria play in converting dissolved nutrients to particulates before discussing remineralization by protists and priorities for further research.
Aggregates have captured the attention of researchers, as sites of enhanced nutrient and biomass concentrations as well as increased microbial activity, for a long time (e.g. Suzuki and Kato 1953, Tsujita 1953, Riley 1963, Nishizawa 1966, Gordon 1970, Seki 1971, Wiebe and Pomeroy 1972, reviews by Fowler and Knauer 1986, Alldredge and Silver 1988). Microscopic observations of detrital aggregates usually reveal the presence of numerous bacteria and algal cells and often the occurrence of protozoa. Phototrophic and heterotrophic nanoflagellates are nearly always present; ciliates seem second in importance (Caron et al. 1982 and 1986, Silver et al. 1984); amoebae (Caron et al. 1982 and 1986, Paerl 1984), radiolaria (Silver and Alldredge 1981, Riemann 1989) and choanoflagellates (Silver and Alldredge 1981) have also been noted. Some of these organisms, especially naked amoebae, are probably highly underestimated because it is difficult to detect them in routine microscopic investigations.
Although oligotrichous ciliates (subclass Choreotrichia, order Choreotrichida) are often regarded as strict phagotrophs, deriving their nutrition from the ingestion of other cells, many species contain pigmented bodies which have long been thought to be residues of digestion of algal cells and only recently have been shown to be algal chloroplasts (Kahl 1932, Burkholder et al. 1967, Taylor 1982, McManus and Fuhrman 1986). Transmission electron microscopy has demonstrated that many marine oligotrichs retain isolated chloroplasts derived from phytoplankton (Blackbourn et al. 1973, Laval-Peuto and Febvre 1986, Jonsson 1987, Stoecker and Silver 1987). A substantial proportion of the planktonic oligotrich fauna contains chloroplasts and is probably mixotrophic, deriving
nutrition from both phagocytosis and photosynthesis (Laval-Peuto et al. 1986, Stoecker et al. 1987, Laval-Peuto and Rassoulzadegan 1988 ).
There has been considerable discussion over the last 10 years on the role that protozoa play in the cycling of major nutrients (nitrogen and phosphorus) in the marine environment. This discussion has been fostered by recent studies which have clearly demonstrated the importance of these heterotrophic protists in the flow of energy and materials in the ocean, and by recent efforts to model their activities in marine ecosystems (Pomeroy 1974, Sieburth 1976, Anderson 1980, Fenchel 1967, 1980, 1986, Azam et al. 1983, Laacke et al. 1983, Sherr and Sherr 1984, Sherr et al. 1986, 1988, Goldman and Caron 1985, Stoecker and Evans 1985).
Fluorescence microscopy has contributed to a major and recent shift in our understanding of plankton ecology. (Pomeroy 1974, Sieburth 1977, Azam et al. 1983, Ducklow 1983). This shift is illustrated by an increased awareness of the important role microorganisms play in marine carbon and nutrient cycles (Williams 1981, Goldman and Caron 1985).
The topic of nuisance algal blooms such as the brown tide’ has become a focus of attention in recent years for both the general public and the scientific community (Nuzzi, 1986; Olsen, 1986; Smayda, 1986, 1988; Okaichi et al., 1988; Wise, 1988). Attention has been drawn to the possibility of a correlation between man’s activities in the coastal zone and the occurrence and possible increasing abundance of massive algal accumulations (Anderson, 1988). As the input of allochthonous materials to our coastal waters continues to expand with coastal development, there is an increasing need to understand the processes that lead to the formation of these phenomenal algal blooms.
Over 200 species have been reported living on, in, or in association with Antarctic sea ice. The ice biota includes bacteria, a variety of algae, heterotrophic protozoans and small metazoans. The diatom assemblages are the only taxonomic group that is known well enough to make comparisons among the various habitats. Studies suggest some specific diatom assemblages along with occurrence of species that are widely-distributed in both ice and plankton. Ice may also serve as a temporary habitat for species that also comprise planktonic communities, so that providing a "seed population' for ice edge plankton blooms may be an important role of the ice biota. Trophic interactions among organisms in ice suggest that the ice assemblage is a true community with a well-developed microbial food web. The ice microbial community may be an important part of the Antarctic marine food web because large consumers from the adjacent planktonic and benthic communities appear to feed on the ice biota. -from Author
With the advent of maps of chlorophyll distribution in the world ocean (Feldman et al., 1989; Lewis, this volume), parochial questions can be asked on a global basis: (1) where, (2) when, and (3) why does phytoplankton occur in the open sea, and (4) how much is found? The first and fourth questions will be addressed briefly at the outset. The paper will treat the second and third questions at length, emphasizing the annual and seasonal time scales. Grazing will be shown to be a key variable that largely has been underrated. In addition to affecting phytoplankton, grazing will be recognized as central to the supply of substrate for the microbial loop.
Dinophysis acuminata C1aparède et Lachmann and Dinophysis norvegica Ehrenberg (two toxic species responsible for diarrhoeic shellfish poisoning) from West Boothbay Harbor were both found to contain food vacuoles. Cells with food vacuoles constituted up to 6 and 36% of the D. norvegica and D. acuminata populations respectively. Food vacuoles were detected whenever these species were present except for a period in August/September when they were missing from the D. norvegica population. Cells containing food vacuoles were filledwith transparent globules, matching the appearance of two related, heterotrophic species which feed upon ciliates, Dinophysis rotundata Claparède et Lachmann and Oxyphysis oxytoxoides Kofoid. Cells were often megacytic and displayed a more intense orange-red plastidic pigmentation than did cells lacking food vacuoles, although no food vacuoles themselves were red. Feeding behaviour in D. acuminata and D. norvegica was not seen.
The ultrastructure of food vacuoles was examined in all four species. Food vacuoles in D. acuminata contained membranous vesicles, lipid-like globules, cylindrical ejectile-like organelles, abundant paracrystalline vesicles and, in three cells, abundant concave starch-like grains. The food vacuoles of D. norvegica match those of some D. acuminata cells. In D. rotundata food vacuoles contained plastids (of the simple type with internal pyrenoid) and rare prasinophyte scales. Some O. oxytoxoides food vacuoles resembled certain D. acuminata food vacuoles. Others contained well-preserved trichocysts, virus particles and (in one instance) prasinophyte scales. Details of D. acuminata food vacuoles, including the high density of starch-like grains, the characteristic extrusomes, the paracrystalline vesicles and the close resemblance of some of these food vacuoles to those of O. oxytoxoides, suggest that D. acuminata preys upon ciliates.
The ultrastructure of food vacuoles was examined in all four species. Food vacuoles in D. acuminata contained membranous vesicles, lipid-like globules, cylindrical ejectile-like organelles, abundant paracrystalline vesicles and, in three cells, abundant concave starch-like grains. The food vacuoles of D. norvegica match those of some D. acuminata cells. In D. rotundata food vacuoles contained plastids (of the simple type with internal pyrenoid) and rare prasinophyte scales. Some O. oxytoxoides food vacuoles resembled certain D. acuminata food vacuoles. Others contained well-preserved trichocysts, virus particles and (in one instance) prasinophyte scales. Details of D. acuminata food vacuoles, including the high density of starch-like grains, the characteristic extrusomes, the paracrystalline vesicles and the close resemblance of some of these food vacuoles to those of O. oxytoxoides, suggest that D. acuminata preys upon ciliates.
Studies of the bathymetric distribution of planktonic foraminifera indicate that they are most abundant in the euphotic zone of the oceanic waters around Bermuda. Seasonal fluctuations in the relative and absolute abundances of fifteen species have been observed from 106 plankton samples, showing a regular succession in the foraminiferal populations. Globorotalia hirsuta, G. truncatulinoides, Globigerina inflata and G. bulloides were most abundant in winter and spring, when temperatures within the euphotic zone ranged between 18° and 23° C and salinities varied between 34.40‰ and 36.60‰. Globorotalia menardii, Globigerinoides sacculifer and G. conglobatus reached their maximum concentrations in summer and fall, when temperatures ranged between 23° and 27° C and salinities between 36.10‰ and 36.40‰. The oceanographic and paleoecologic implications of these observations are discussed for the northern Sargasso Sea.
Amoebae were cultured from 43 to 49 samples taken from 19 stations in North Atlantic waters: four samples from Narragansett Bay, Rhode Island; 20 samples between Rhode Island and Spain (R/V Trident cruise 170); and 25 samples from the open ocean waters of the Strails of Florida (R/V Gilliss cruise 7603). Both surface microlayers and subsurface samples were obtained. Particulate matter was concentrated and dilutions cultured in artificial sea water with OZR agar plugs. An average of 33.6 amoebae/liter were found in the surface microlayer samples (equal to 1,413 organisms/liter, assuming their association with a 5 µm-thick surface layer and a 70% collection efficiency), while subsurface water contained an average population of 1,4 organisms/liter, to a depth of 3,090 meters. The surface microlayer had a higher number of species isolated per sample than subsurface samples. Clydonella, Acanthamoeba, and Platyamoeba were the most frequently encountered genera in both oceanic samplings. Narragansett Bay samples showed a greater diversity of species than those from the Straits of Florida and trans-Atlantic stations. For the surface microlayer samples from all three sample sets, there were no significant differences in the numbers of amoebae/ liter. However, the subsurface values for the trans-Atlantic samples were significantly lower than those for either the Straits of Florida or Narragansett Bay. There was an inverse relationship between numbers of amoebae and dissolved oxygen in subsurface samples, and a positive correlation of amoebae with particulate ATP in the surface microlayer.
Modern planktonic foraminiferal assemblages from quantitative plankton samples collected in the western North Atlantic reflect broad ecologic zones. The relative abundance of eight species increases southward to the Sargasso Sea, whereas that of five other species increases northward to the colder slope waters. The greatest absolute abundance of planktonic foraminifera is in the Gulf Stream system, where strong temperature and salinity gradients exist.
This work describes the quantitative effects of fixatives on the storage of freshwater planktonic ciliates. Samples originated from a small eutrophic mountain lake (lac d' Aydat, France). Unconcentrated, filtered and centrifuged samples were preserved in five different fixatives: Mercuric chloride (HgCl2), Lugol, Formaldehyde, Glutaraldehyde, and Champy-Da Fano. Counts (in triplicates) were done over 9 months, with a Periodicity of 3 months, and compared by simple regression between loss rate (Y) and storage time (X).
Grazing on chlorophyll by microzooplankton (<200 mu m) and copepods was measured in the mixed layer of the high-latitude North Atlantic Ocean during May and August 1991. No significant grazing by microzooplankton occurred in May during a spring bloom dominated by colonial Phaeocystis pouchettii and Nitzschia spp. As the bloom declined, the size distribution of chlorophyll shifted from dominance by the >20 mu m chlorophyll fraction to dominance by the <20 mu m chlorophyll fraction. The impact of grazing by microzooplankton increased as the bloom declined, with microzooplankton consuming 100% of potential daily chlorophyll production following the bloom. In August, when the phytoplankton was dominated by the <20 mu m chlorophyll fraction, microzooplankton consumed 37-53% (mean = 41%+/-11% s.d.) of potential daily chlorophyll production. Averaged over all experiments, microzooplankton grazing accounted for 81% bf daily chlorophyll production. The grazing impact of Calanus finmarchicus-stages C4 and C5, which dominated mesozooplankton biomass in the upper euphotic zone. in both spring and late summer, was concentrated on chlorophyll >20 mu m in both seasons; C. finmarchicus did not consume significant amounts of chlorophyll <20 mu m in either season. Compared to the microzooplankton, copepods did not consume a significant fraction of total chlorophyll in either season, accounting for only similar to 1% of daily chlorophyll production.
Minute amounts of trace elcmcnts can affect phytoplankton metabolic processcs. Consc- quentl y, 14C primary productivity nic;isurcmc\nts may lx adversely affect4 by contaminant metals inadvertently adclcd cluring sampling aud handling proceclurcs. We ;malyzcd various components usccl in the stnnclard 14C method for metals; significant amounts of contaminants were found in many of the stock solutions used in this procedure and in associated containers. 14C: uptake rates were lower under contaminated conditions than those with clean techniques. The latter are dcscril>etl in &nil; their adoption is urged for more accurate and precise cstimatcs of this fundamentally important process.
The biomass of marine "oligotrichous' ciliates has often been estimated by measuring the cell volume of preserved samples and converting to units of carbon based on theoretical carbon:volume (C:vol) ratios of 0.07-0.11 pg μm-3. Using laboratory cultures of strains of Laboea strobila, Strombidium spp., and Strobilidium spiralis, a C:vol conversion factor of 0.19 pg μm-3 was experimentally derived for cells preserved with 2% vol:vol Lugol's iodine. A C:vol ratio of 0.14 pg μm-3 applies to Formalin-preserved cells. -from Authors
A complete analysis of the macro- and microzooplankton of a warm monomictic lake indi- cates that Protozoa dominate the community numerically. During winter mixis, ciliates are found at densities of l-8 x 103*liter-' and constitute up to 32% of the zooplankton community biomass, With summer stratification crustaceans decline, while both the relative and absolute abundance of protozoans and rotifers increase. Densities of protozoans are highest (l-2 x 105* liter-l) in the metalimnion where scuticociliates bloom in zones of intense bacterial ac- tivity. During the period of these blooms (July-October), Protozoa account for 15-62% of the zooplankton biomass. This suggests that Protozoa make a significant contribution to rates of grazing, nutrient regeneration, and secondary productivity and should not be overlooked in - -
Five species of colonial Radiolaria collected by divers on 27 cruises were used for experimental metabolic measurements. Carbon content as an indicator of colony size correlated well with cell number in three species, with approximately 50, 100, and 200 ng C per cell. Chlorophyll a per radiolarian cell (from symbiotic dinoflagellates) varied widely between colonies and could not be predicted from colony size by better than a factor of 2. Photosynthetic carbon incorporation at high levels of natural light ranged from 10 to 76 pmol C · cell ⁻¹ · h ⁻¹ . Mean respiration in two species was 5.3–5.5 µ l O 2 · mg C ⁻¹ · h ⁻¹ . Respiration is probably balanced by photosynthesis under normal light conditions.
Colonial Radiolaria were present at 92% of 268 oceanic stations and very abundant at 34%. Measured abundances ranged from 0.04 to 14 colonies · m ⁻³ in the water column and reached 540 colonies · m ⁻³ in patches at the surface. Because the primary productivity of their symbionts is probably consumed in maintenance metabolism, colonial Radiolaria may be most important to the epipelagic oligotrophic ecosystem as gelatinous predators.
In plankton samples from the Atlantic Ocean preserved in buffered seawater‐form‐aldehyde, it has been unusual for the spicules of Acantharia to be so seriously eroded as to interfere with their taxonomic study; some families are more susceptible to erosion than others. Acantharia are never rare in samples from reasonably deep oceans; in No. 10‐mesh net collections they almost always make up more than 1%, very often 10–20%, and frequently over 30% of the organisms caught. Available data show Acantharia generally more abundant than Foraminifera or Radiolaria, although these three groups of Sarcodina show covariance in abundance.
The abundance of non-testate ('naked'), free-living amoebae was examined in surface waters of the Black Sea during 5 cruises in 1992 and 1993. Amoebae (≤20 μm in size) were observed in samples collected during 2 of the 5 cruises at abundances up to approximately 380 ml-1. The abundance and biomass of amoebae were low relative to other nanoplanktonic protozoa when averaged over all stations, but amoebae occasionally constituted a major component of the heterotrophic nanoplanktonic assemblage (up to 16% of abundance and 93% of biomass of the protozoa 2 to 20 μm in size). Abundances of amoebae correlated weakly with the total number of heterotrophic nanoplankton, and with ash free dry weight, but not with several other physical, chemical and biological parameters. Based on the highest abundances of naked amoebae observed in this study we suggest that these protozoa can occasionally be important in energy and elemental cycling in Black Sea plankton.
Growth and ingestion rates of the marine mixotrophic dinoflagellate Fragilidium sub-globosum were studied as functions of light intensity with and without the presence of particulate food (Ceratium spp.). F. subglobosum was shown to be a facultative mixotroph; it was capable of phototrophic growth in monocultures as well as of heterotrophic (phagotrophic) growth in the dark. When F. subglobosum was growing in light in food-satiated cultures, growth rates were higher than pure phototrophic growth rates at corresponding light intensities. At high light intensities, ingestion was inversely related to light intensity, but this did not apply to lower light intensities. Phagotrophy thus accounted for 34 to 100% of total growth in food-satiated cultures according to light intensity. Chlorophyll a content per cell of F. subglobosum decreased with increasing light intensity and ingestion of prey also resulted in a decreased chlorophyll a content. Phototrophic monocultures of F. subglobosum needed approximately 24 h following the addition of prey to fully adapt to phagotrophic metabolism.