Temporal and spatial distribution of the dinoflagellate Ceratium hirundinella O.F. Müller within a small productive lake

The growth of Ceratium hirundinella in Esthwaite Water, a small productive lake, was investigated during 1975; the horizontal distribution of the alga was studied on four occasions over a 3-week period. Measurements of lake temperature, oxygen concentration, and vertical stratification of Ceratium at close intervals of depth, were also made. Lake population estimates from large samples at many stations were compared with small samples at the regular sampling station. On two occasions the means of these samples were significantly different (P<0·01). On one date, the estimate of Ceratium abundance in the lake from the large sample at many stations was more than twice the value obtained from the sample collected at the regular sampling station. The population of Ceratium was contagiously distributed in all the large samples. On 3 days the horizontal distribution showed an increase in Ceratium numbers towards the windward shore of the lake. Very large accumulations of Ceratium were found in the metalimnion, just above the anaerobic hypolimnion, during late afternoon. Possible mechanisms of horizontal pattern development are considered, based on the measurements of the vertical distribution of Ceratium, and meteorological factors. The ecological consequences for Ceratium of vertical and horizontal movements, and its spatial distribution in the lake, are discussed.     

Influence of Biological Factors on Connectivity Patterns for Concholepas concholepas (loco) in Chile

In marine benthic ecosystems, larval connectivity is a major process influencing the maintenance and distribution of invertebrate populations. Larval connectivity is a complex process to study as it is determined by several interacting factors. Here we use an individual-based, biophysical model, to disentangle the effects of such factors, namely larval vertical migration, larval growth, larval mortality, adults fecundity, and habitat availability, for the marine gastropod Concholepas concholepas (loco) in Chile. Lower transport success and higher dispersal distances are observed including larval vertical migration in the model. We find an overall decrease in larval transport success to settlement areas from northern to southern Chile. This spatial gradient results from the combination of current direction and intensity, seawater temperature, and available habitat. From our simulated connectivity patterns we then identify subpopulations of loco along the Chilean coast, which could serve as a basis for spatial management of this resource in the future.     

Inclusion bodies in several species of Ceratium Schrank (Dinophyceae) from the Caribbean Sea examined with DNA-specific staining

Several dinoflagellate species in the genus Ceraiium Schrankwere examined, with the help of a DNA-specific dye, for thepresence of a nucleus, chloroplasts and inclusion bodies. Theabundance of Ceratium in the Caribbean Sea in April 1990 wasbetween 1.3 and 4.9 x 10⁵ cells m^–3 Most Ceratium teresKofoid contained 5–10 small chloroplasts and among 529C.teres cells. 8% possessed an inclusion body. The shape andsize of inclusion bodies varied, and 7% of the inclusions hada DNA-containing particle inside. Similar inclusion bodies werealso observed in Ceratium declinatum f. normale Jörgensen,Ceratium furca (Ehrenberg) Claparede and Lachmann, and Ceratiumfusus (Ehrenberg) Dujardin. Our observations indicated thatinclusion bodies are common in oceanic Ceratium. ¹Present address: Institute of Marine Biology, National TaiwanOcean University, Keelung 20224, Taiwan, ROC     

Vertical microscale patchiness in nano- and microplankton distributions in a stratified estuary

Microscale (decimetre) vertical heterogeneity in the distributionof nano- and microplankton was studied on August 23, 1999 attwo different sites (separated by ~40 m) in Aarhus Bay, Denmark.At the time of sampling, the water column was stratified withrespect to both temperature and salinity and a subsurface fluorescencemaximum (corresponding to ~10 µg chlorophyll a l^-1) occurredimmediately below the primary pycnocline (9 m). Samples forspecies identification were taken at the surface, near the bottomof the water column and at 20 15-cm intervals in and aroundthe depth of maximum fluorescence. The plankton communitiesrecorded in the three different regions of the water columndiffered dramatically from one another. In addition, significantdifferences were found in the distribution patterns of speciesand functional groups in the region of sampling around the fluorescencepeak. The same patterns in vertical species distributions wereobserved at the two stations. In the region surrounding thesubsurface fluorescence peak, diatoms were, generally, regularlydistributed, although the total diatom biomass decreased slightlywith depth. Dinoflagellate species were mainly non-regularlydistributed and could be divided into two groups: (i) autotrophicor potentially mixotrophic species (Dinophysis norvegica, Dinophysisacuminata, Dinophysis cf. dens, Prorocentrum micans, Gymnodiniumchlorophorum and Ceratium macroceros) that mainly decreasedin numbers with depth or were aggregated in their distribution;and (ii) heterotrophic or potentially mixotrophic species (Ceratiumlineatum, Ceratium longipes, Ceratium furca, Ceratium tripos,Ceratium fusus, Protoperidinium curtipes, Protoperidinium steinii,Diplopsalis spp. and Katodinium glaucum). In the latter group,the species mainly increased in numbers with depth or were randomlydistributed. Most ciliates were uniformly distributed verticallyin the water column. However, small cells of the photosynthesizingciliate Mesodinium rubrum were most abundant at the depth ofmaximal fluorescence while large M. rubrum cells were equallyabundant at all the depths sampled, suggesting the two sizegroups of this organism may differ ecologically. Overall, thestudy demonstrates that traditional plankton sampling methodsmay lead to misinterpretations of speciesco-existence and interactions.     

The drifting dinoflagellate Ceratium furcoides (Levander) Langhans 1925: fundamental niche shift during global invasion

Hydrobiologia - Ceratium furcoides is a freshwater dinoflagellate originally from cold waters of northern Europe that has been expanding its distribution into new areas worldwide. Species...     

Small-scale spatial distribution of the euphausiid Euphausia pacifica and overlap with planktivorous fishes

The spatial distribution of zooplankton and planktivorous fishin Saanich Inlet, British Columbia was characterized with a445 kHz multibeam sonar capable of localizing individual animalsin three dimensions. Numerical simulation of data processingprocedures indicates that this instrument has sufficient resolutionto characterize zooplankton spatial distributions using Lloyd’sindex of patchiness and nearest neighbour distance (NND) measures.Zooplankters at this site were dominated by the euphausiid Euphausiapacifica which underwent diel vertical migration (DVM). Fish(mainly herring and walleye pollock) were only abundant at thisdeep-water station at night. Analysis of 4 m³ volumes over scalesof     

DIEL CHANGES IN PHASED-DIVIDING CULTURES OF CERATIUM FURCA (DINOPHYCEAE): NUCLEOTIDE TRIPHOSPHATES,ADENYLATE ENERGY CHARGE,CELL CARBON,AND PATTERNS OF VERTICAL MIGRATION1

The diel pattern of cell division, cell carbon, adenine nucleotides and vertical migration was determined for laboratory cultures of the photosynthetic marine dinoflagellate, Ceratium furca (Ehr.) Clap. & Lachm., entrained on an alternating 12:12 LD schedule at 20 C. Cell division was initiated during the latter portion of the dark period with ca. 30% of the population undergoing division. Cell C increased during the light period and exhibited a linear decrease with a loss of 33% during the dark period. ATP · cell^?1 increased during the light period and decreased by ca. 40–50% during the dark period. The diel patterns of cell C and ATP tended to “buffer” the magnitude of the change in C:ATP ratios around an overall mean value of 89. There was no obvious trend in the concentration of [GTP + UTP] · cell^?1 over the cell cycle. The cellular adenylate energy charge was maintained at values between 0.8 to 0.9 throughout the 24 h LD cycle, despite a ca. 40% decrease in total adenylates (A_T= ATP + ADP + AMP) during the dark period on 12:12 LD, and over a 68% decrease in ATP during 42 h of continuous darkness. These data lend experimental support to the theory of cellular metabolic control by the adenine nucleotides. With lateral illumination on 12:12 LD cycles, the cells began to concentrate at the surface of the experimental tubes shortly before the lights were turned on, and at the bottom of the tubes shortly before the lights were extinguished. This pattern continued for 6 days in continuous darkness, suggesting that the vertical migration pattern is independent of a phototactic response and may be under the control of an endogenous rhythm.     

Metapopulation processes and persistence in remnant water vole populations

We examined the spatial distribution of water vole populations in four consecutive years and investigated whether the regional population processes of extinction, recolonisation and migration influence distribution and persistence. We examined how such regional processes are influenced by spatial variation in habitat quality. In addition, we assessed the relevance of metapopulation concepts for understanding the dynamics of species that deviate from classical metapopulation assumptions and developing conservation measures for them. Populations were patchy and discrete, and the patchy distribution was not static between years. Population turnover occurred even in the absence of predatory mink, which only influenced the network of populations at the end of the study. Most populations were clustered close together in the upper tributaries. Local population persistence was predominantly influenced by population size: large populations were more persistent. Recolonisation rates were influenced by isolation and habitat quality. The isolation estimates which best explained the distribution of water vole populations incorporated straight‐line distances, suggesting water voles disperse overland. The distribution of recolonised sites indicated that dispersing voles actively selected habitat on the basis of its quality. Water voles depart from some of the assumptions made by frequently used metapopulation models. In particular there is no clear binary distinction between suitable and non‐suitable habitat. Accounting for variation in habitat quality before investigating temporal changes in population distribution allowed us to demonstrate that the key metapopulation processes were important. The significance of regional population processes relative to local population processes may have increased in declining, fragmented populations compared to pristine regional populations. We hypothesise that although mink predation is likely to eventually cause regional extinction in many areas, metapopulation processes have delayed this decline. Consequently, conservation measures should take into account mink predation rates and regional population processes, before considering aspects of habitat quality.     

Quantifying Littoral Vertical Habitat Structure and Fish Community Associations using Underwater Visual Census

Synopsis We developed and tested a new visual census technique to quantify the importance of vertical habitat structure on the associated fish assemblages in the littoral zone of a freshwater lake. We demonstrated that the primary environmental gradient, accounting for the most variation in the species data, represented a temporal gradient of seasonal characteristics. The secondary environmental gradient was related to the vertical structure at the sampling locations, showing the importance of the vertical component of the environment on fish community structure. Characterizing the vertical component at different resolutions provided different interpretations. The primary difference was the strength of influence of woody material on community structure. Woody material had a stronger influence on community structure throughout the water column when a single vertical unit defined the fish data. The appropriateness of defining the data by either multiple vertical strata or by a single vertical one would be dependent on the objectives of the study, as neither approach was found to explain substantially more variation in the species data. The current study demonstrates that fish are closely associated with particular elements of habitat structure in the littoral zone, even in the absence of major piscivorous predators. We provide a novel study quantifying the vertical multiple habitat structures and habitat use by fish in the water column of a freshwater lake. The new vertical visual census technique can be used to more comprehensively sample the three-dimensional environment of lake littoral zones, and quantify the fish–habitat spatial relationships across a range of abiotic and biotic habitat features.     

Potential distribution of the invasive freshwater dinoflagellate Ceratium furcoides (Levander) Langhans (Dinophyta) in South America

Dinoflagellates of the genus Ceratium are predominantly found in marine environments, with a few species in inland waters. Over the last decades, the freshwater species Ceratium hirundinella and Ceratium furcoides have colonized and invaded several South American basins. The purpose of this study was to create a distribution model for the invasive dinoflagellate C. furcoides in South America in order to further investigate the basins at potential risk, as well as the environmental conditions that influence its expansion. This species is known to develop blooms due to its mobility, resistance to sedimentation, and optimized use of resources. Although nontoxic, blooms of the species cause many problems to both the natural ecosystems and water users. Potential distribution was predicted by using a maximum entropy algorithm (MaxEnt). Model was run with 101 occurrences obtained from the scientific literature, and climatic, hydrological and topographic variables. The developed model had a very good performance for the study area. The most susceptible areas identified were mainly concentrated in the basins between southeastern Brazil and northeastern Argentina. Besides already affected regions, new potentially suitable areas were identified in temperate regions of South America. The information generated here will be useful for authorities responsible for water and watershed management to monitor the spread of this species and address problems related to its establishment in new environments.     

Observations on Alexandrium tamarense (Lebour) Balech and Other Dinoflagellate Populations in Golfo Nuevo, Patagonia (Argentina)

The toxic dinoflagellate Alexandrium tamarense and other dinoflagellatespecies were studied, along with water temperature and nutrientconcentrations, from September 1995 to December 1998 in theGolfo Nuevo, Chubut, Argentina. Nutrient concentrations werelow, showing a peak of high concentration in winter and a phaseof depletion in late spring and summer. Dinoflagellates tendedto be abundant during spring and summer, when Prorocentrum micanswas the most important species. Other dinoflagellates were Pyrophacushorologium and Dinophysis acuminata. Ceratium tripos, C. fususand C. horridum were present during the autumn, and a C. tripospeak up to 5.9 x 10³ cell l^–1 was observed in May 1997.Alexandrium tamarense showed strong interannual variation, thehighest concentration being found in spring (September–October)1995, with densities up to 15 x 10³ cells l^–1. The secondA.tamarense peak was observed during October–November1998 with maximal densities up to 5 x 10³ cells l^–1. Moderatelyhigh A. tamarense cyst densities, up to 300 cysts cm^–3of sediment, were found in the deep zone of the Golfo Nuevobasin. Among meteorolog-ical variables, increased late winterrain and higher solar radiation during spring may have influencedA. tamarense blooms.     

Streams over mountains: influence of riparian connectivity on gene flow in the Pacific jumping mouse (Zapus trinotatus)

In species affiliated with heterogeneous habitat, we expect gene flow to be restricted due to constraints placed on individual movement by habitat boundaries. This is likely to impact both individual dispersal and connectivity between populations. In this study, a GIS-based landscape genetics approach was used, in combination with fine-scale spatial autocorrelation analysis and the estimation of recent intersubpopulation migration rates, to infer patterns of dispersal and migration in the riparian-affiliated Pacific jumping mouse (Zapus trinotatus). A total of 228 individuals were sampled from nine subpopulations across a system of three rivers and genotyped at eight microsatellite loci. Significant spatial autocorrelation among individuals revealed a pattern of fine-scale spatial genetic structure indicative of limited dispersal. Geographical distances between pairwise subpopulations were defined following four criteria: (i) Euclidean distance, and three landscape-specific distances, (ii) river distance (distance travelled along the river only), (iii) overland distance (similar to Euclidean, but includes elevation), and (iv) habitat-path distance (a least-cost path distance that models movement along habitat pathways). Pairwise Mantel tests were used to test for a correlation between genetic distance and each of the geographical distances. Significant correlations were found between genetic distance and both the overland and habitat-path distances; however, the correlation with habitat-path distance was stronger. Lastly, estimates of recent migration rates revealed that migration occurs not only within drainages but also across large topographic barriers. These results suggest that patterns of dispersal and migration in Pacific jumping mice are largely determined by habitat connectivity.     

Vertical and temporal heterogeneity of planktonic ciliated protozoa in a humic lake

Seasonal population dynamics and the vertical distribution ofciliates were studied in relation to the particular food resourcesoccurring in a humic and moderately acidic lake (Lake Vassivière).The abundance (1.4 x 10³–20.4 x 10³ cells l^–1 mean= 4.8 x 10³ cells l^–1) and biomass (0.5–34.6 µgC l^–1, mean = 6.0 µg C l^–1) of ciliated protozoawere low and close to values reported for oligotrophic environments.The species composition of the population varied greatly withdepth. Whereas large-sized species of oligotrichs, some of whichwere mixotrophic, dominated at the surface, haptorids were bestrepresented in deep waters. The spatial distribution of thevarious groups of ciliates was largely determined by light andthe vertical distribution of microbial food resources (detritus,bacteria, algae) within the water column of this brown-coloredlake.     

A fish-kill in Heart Lake, Ontario, associated with the collapse of a massive population of Ceratium hirundinella (Dinophyceae)

SUMMARY. A massive population of the common dinoflagellate Ceratium hirundinella developed in Heart Lake. Ontario, Canada during the summer of 1976 and its sudden collapse and subsequent decomposition depleted dissolved oxygen and resulted in a fish-kill in the lake. The lake was being artificially mixed at the time by supplying compressed air to the bottom waters and the limnological events contributing to the development of the Ceratium population and its collapse appear to be closely related to the artificial destratification process. Artificial destratification during 1976 precluded the development of blue-green algue. The process also led to an increase in the density of herbivorous zooplankters which controlled the development of smaller planktonic algae. Ceratium flourished in Heart Lake because there was little competition for nutrients from other algae and because Ceratium cells are too large to be grazed by the zooplankton. The maximum size of the Ceratium population (53 mm³ 1⁻¹) is apparently the highest biomass reported in the literature and its collapse may have been related to a depletion of inorganic nitrogen. There is apparently no previously published record of a Ceratium -induced fish-kill in a freshwater lake.     

Modelling spatial distributions of Ceratium hirundnella and Microcystis. in a small productive British lake

The short-term relationships between the spatial distributions of phytoplankton and the environmental conditions of Esthwaite Water, a small eutrophic lake in the English Lake District, UK, were examined using a hydrodynamic model. Spatial distributions of phytoplankton were simulated on two occasions the first, when the population was dominated by dinoflagellates; and the second, when the population was dominated by cyanobacteria.Vertical motility of the dinoflagellate Ceratium hirundinellaand buoyancy of the cyanobacteria Microcystis ssprm.were estimated as functions of irradiance. Water velocity fields were estimated through solving the 3-D Navier–Stokes equations on a finite-volume, unstructured non-orthogonal grid. Simulated circulation patterns of water and phytoplankton were similar to those obtained through field observations. Near-surface drift currents were initiated by wind stress, which then generated return currents along the seasonal thermocline. Aggregations of motile Ceratiumthat existed near the thermocline were pushed upwind by the deep return currents and accumulated at upwelling areas. In contrast, near-surface aggregations of Microcystiswere pushed downwind by the surface currents and accumulated at downwelling areas. Horizontal and vertical phytoplankton distributions resulted from the interaction between the vertical motility of the phytoplankton (dependent upon the light environment) and the velocity vectors at the depths at which the phytoplankton accumulated (dependent upon wind stress and morphometry). Modelling showed that phytoplankton motility and buoyancy greatly affect phytoplankton spatial distributions.     

Diel vertical migration of Cryptomonas and Chromatium in the deep chlorophyll maximum of a eutrophic lake

Large populations of the phytoflagellates Cryptomonas rostratiformis,Cryptomonas phaseolus, Cryplomonas undulata and the phototrophicbacterium Chromatium cf. okenii have been observed in the oxic/anoxicboundary layer of the slightly eutrophic, dimictic lake Schlachtenseeduring the summer stratification. Vertical distribution of thesepopulations was studied with the help of a new close-intervalsampler and by in Situ fluorescence measurements with fine spatial(cm to dm) and temporal (h) resolution on 4 days in 1991, 1994and 1995. All populations lived close to the chemo dine butshowed a regular diel vertical migration with daytime ascentand night-time descent and a low migration amplitude. At leastfor one species— C. rostratiformis—the pattern ofmigration suggests that this behaviour has an endogenous origin.As a result of diel vertical migration, the population of C.rostratiformiswas spatially separated from the other dominating populationsduring daytime. Ultimate cause of diel vertical migration wasa better light supply of all populations. Another probable advantagewas the reduction in grazing pressure, as large percentagesof all populations moved into the anoxic, hydrogen sulphidecontaining water layers during night-time. ¹Present address Department of Lowland Rivers and Shallow Lakes,Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm260, D-12587 Berlin, FRG     

A seasonal sequence of diel distribution patterns for the planktonic dinoflagellate Ceratium hirundinella in a eutrophic lake

SUMMARY. 1. Diel depth distribution patterns of Ceratium hirundinella were studied during eleven sampling periods, covering the seasonal growth cycle. They were shown to result from short-term periodic or non-periodic external factors, endogenous responses of the alga, and interactions between these.
2. Diel variations in wind stress resulted in the net transport of algae into or out of the sampling position due to lateral water movements. A progressive surface accumulation of Ceratium , leading to a 3-fold increase in cell numbers at the sampling site over a 24 h period, was due to wind-induced upwelling of deeper cells. Near-surface accumulation of Ceratium on a completely overcast afternoon, similar to that associated with migrations, was attributable to advection.
3. Under sufficiently calm conditions, depth-differentiation of Ceratium was regulated by its vertical swimming movements with a diel periodicity. Migration patterns observed in earlier work were confirmed and extended. The alga migrated towards the surface during the daytime and downward during the night; this rhythm had an endogenous component.
4. At high surface illumination, the alga retreated from the surface and formed discrete sub-surface maxima; at low irradiance Ceratium showed positive phototaxis and concentrated near the surface. Under either condition of irradiance Ceratium actively aggregated at depths associated with irradiance levels of about 125–155 μEinsteins m ⁻² s ⁻¹. Downward movement was restricted by anoxic conditions and possibly by thermal/ density gradients. However, given sufficient light penetration, dissolved oxygen and nutrient availability, the thermal density gradient does not apparently eliminate downward movement by Ceratium.     

生境破坏的模式对集合种群动态和续存的影响

构建了空间关联的集合种群模型,该模型不但包含了种群的空间结构信息,而且引入了破坏生境的全局密度和局部密度两个指标,它们描述了破坏生境的模式.模型揭示了破坏生境的空间分布格局复杂地影响了集合种群的动态和续存,破坏和未破坏生境斑块的均匀混合不利于集合种群的增长和续存,而生境类型聚集分布可以促进集合种群的快速增长和长期续存;对于两种斑块类型相对均匀混合的生境来说,均匀场假设可能会高估集合种群的续存,对于相对斑块类型高度聚集的生境,均匀场假设可能会低估集合种群的续存;物种的迁移范围也会影响集合种群的续存,迁移范围越大的物种越容易抵御生境的破坏而免遭灭绝.这意味着在生物保护中不能仅仅考虑生境的恢复和斑块质量的改善,生境结构的构建也是很重要的,加强生境斑块之间的连通性也有利于物种的长期续存.     

Spatial and temporal aspects of Gyrodinium galatheanum in Chesapeake Bay: distribution and mixotrophy

Gyrodinium galatheanum (Braarud) Taylor 1995 is a common bloom-forming,potentially toxic photosynthetic dinoflagellate in ChesapeakeBay, USA. Abundance of this dinoflagellate achieved densities>4 x 10³ cells ml^–1 in the mid- and upper Bay duringlate spring and early summer of 1995 and 1996. Ingestion ofcryptophytes by this dinoflagellate was detected in most samplescollected from the Bay. During late spring and early summer,mean number of ingested cryptophytes per G.galatheanum was ashigh as 0.46 for dinoflagellate populations located in surfacewaters of the mid- and upper Bay where dissolved inorganic phosphoruswas low. Observations on the distribution of G.galatheanum inChesapeake Bay show that populations of this dinoflagellatewere usually restricted to waters with salinities ranging from7 to 18 psu, seasonally progressed up the estuary, and usuallyco-occurred with cryptophytes. Correlation analysis indicatesthat abundance of G.galatheanum and incidence of feeding wasnegatively correlated with dissolved inorganic phosphorus, andthat incidence of feeding was positively correlated with abundanceof cryptophyte prey. These results indicate that G.galatheanumis an important component of the Chesapeake Bay phytoplanktonduring the spring and summer. Our results suggest that the phagotrophiccapability possessed by this phototrophic dinoflagellate maycontribute to its success in a varying-resource environmentlike Chesapeake Bay.     

Etude des migrations verticales journalières du phytoplancton à l'aide d'enceintes placées dans un Rang peu profond

Two enclosures without a bottom were placed in a shallow non-stratified pond. One of these enclosures (B) had a transparent plastic wall and was open at the top. The second enclosure (N) was painted in black and covered over. The vertical distribution and daily migration of Ceratium hirundinella, Trachelomonas spp., Gomphosphaeria naegeliana and Aphanizomenon flos-aquae were studied. Investigations were carried out during a 24 h period both in the pond and inside the two enclosures. Vertical migration was shown by the four algae, even within the water column N. Differences between the behaviour patterns of the different algae are described.