Barrie Dale

Cyst formation, sedimentation, and preservation: Factors affecting dinoflagellate assemblages in recent sediments from trondheimsfjord, Norway

Plankton records and 25 samples of Recent sediment from Trondheimsfjord and the adjoining shelf were studied to investigate production, sedimentation, and preservation of cysts, as factors which influence the eventual composition of dinoflagellate cyst assembleges. All sediment samples were examined for dinoflagellate cysts using routine semiquantitative palynological procedures. In addition, fjord sediments were subjected to a limited sediment analysis, and, for three samples, results from preparations both with and without acid treatments were compared. For the first time, cyst assembleges from Recent sediments were directly compared with extensive plankton records from overlying waters. Results indicate that approximately 20% of the 55 locally recorded dinoflagellate species contribute cysts to bottom sediments. Once formed, cysts behave as fine silt particles in the sedimentary regime, increasing in abundance as the percentage abundance of finer sediment increases, usually with increased water depth. Cyst-forming species are almost entirely restricted to a few genera, particularly Gonyaulax and Peridinium, within the order Peridiniales. For some groups, reasonably good correspondence was found between percentage abundances of dinoflagellates in plankton and their cysts in sediment, though plankton records covering at least five years were required to establish this. Gonyaulax grindleyi Reinecke (Von Stosch 1969) appeared to be consistently overrepresented by cysts in sediment relative to available plankton evidence; possible explanations are suggested. At least 30% of the cyst species present, including most Peridinium species, were eliminated, or rendered unreliable for semiquantitative palynology, by application of routine palynological preparation treatments. Such cysts may provide useful, non-quantitative, palynological information from Recent and possibly Quaternary sediments, but their persistence would seem unlikely. Thus, factors of preservation probably further restrict the dinoflagellate fossil record. Cyst assemblages from Trondheimsfjord are comparable with those previously recorded from the northeastern coast of U.S.A., and from Scotland and northeastern England. Fjord assemblages are dominated by small, simple, spinose cysts which would be regarded as acritarchs if culture experiments had not proved that they are dinoflagellate cysts. Much potential biogeographic and palaeoenvironmental information was included within the less abundant species. Attention is drawn to the role which future culture experiments may be expected to play in helping to resolve taxonomic difficulties currently affecting dinoflagellate studies. Palynological significance of results from the present study is discussed especially with reference to recent work by Von Stosch which strongly suggests that cysts may be hypnozygotes formed routinely in sexual cycles of dinoflagellates.

New observations on Peridinium faeroense Paulsen (1905), and classification of small orthoperidinioid dinoflagellates

New observations on Peridinium faeroense include details of sulcal and cingular tabulation, thecal ultrastructure, and cysts, recently suggested to be taxonomically important criteria. The organism was studied both in preserved plankton from Norwegian fjords and in cultures started with cysts from Oslofjord sediment. Two similar species were compared: Scrippsiella trochoidea (Stein) A. R. Loeblich III (cultured with cysts from Oslofjord) and Peridinium loeblichii (Cox et Arnott) comb. nov. (culture LB 1595, Indiana University Collection). P. faeroense has four sulcal plates, five cingular plates, and distinctive trichocyst pores surrounded by concentric ridges. It produces acid-resistant, organic walled cysts which are probably hypnozygotes formed in a sexual life cycle involving fusion of gametes. It has been recorded from fjords or embayments in north temperate regions of eastern and western N. Atlantic, and in N.E. Pacific Ocean. Motile cells commonly occur in the spring plankton, and cysts provide a b...

Cysts of the toxic red-tide dinoflagellate Gonyaulax excavata (Braarud) Balech from Oslofjorden, Norway

Abstract Gonyaulax excavata was cultured from, resting cysts isolated from bottom sediments in Oslofjorden, the type locality. Resting cysts were elongate-ovoid with thick smooth walls surrounded by gelatinous material incorporating detritus; contents typically included starch grains, oil globules, and a conspicuous red-pigmented body. A resting period seems to be mandatory, and cysts are suggested to act as ‘seed beds’ for some toxic blooms. Other non-motile cells (temporary cysts) were formed in cultures, cooled from 15° C to less than 5° C. These had thinner walls and lacked gelatinous cover and typical cell contents of resting cysts. They quickly reestablished motile cells when returned to 15° C. Cultured motile cells were toxic to mice, bioluminescent, and consistently lacking ventral pores, in accordance with recent suggestions that these are specific criteria. Resting cyst morphology suggests a possible systematic relationship between G. excavata and Pyrophacus horologium.

Dinoflagellate cysts as environmental indicators in surface sediments from the Congo deep-sea fan and adjacent regions

Abstract Forty-nine surface sediment samples from the Congo deep-sea fan and adjacent hydrographic environments were prepared palynologically and analyzed for fossilizable dinoflagellate cysts. The main objective was to investigate the extent to which cysts reflect present-day hydrography, and therefore may be used downcore as paleoceanographic indicators. The region sampled covers a range of marine environments including the Congo River plume, the area of pronounced upwelling off West-Central Africa, and a nearshore–offshore gradient from coastal to oceanic waters. This is the first study of the effect of a major tropical river plume on associated cyst assemblages. Cyst counts were low, particularly near the river mouth and furthest offshore. A combination of statistical treatments was used to analyze the surface cyst assemblages, including cluster analysis, correspondence analysis and canonical correspondence analysis. This helped to identify five distinctive sample groupings representing the main ecological signals in the cyst assemblage data. Group A, dominated by spherical brown protoperidinioid cysts, is an upwelling signal. Group B, dominated by the cosmopolitan species O. centrocarpum, is the main signal for the river plume effect, interpreted as reflecting the environmental instability this creates. Group C, dominated by S. delicatus with accessory O. centrocarpum, characterizes the outer plume, somehow reflecting the mixing of progressively diluted river plume water and the surrounding oceanic waters. Group D, with high proportions of Impagidinium and Nematosphaeropsis together with O. centrocarpum and S. delicatus, characterizes the location of the Angola–Benguela Front. Group E, with mainly Impagidinium species, is an oceanic signal. The identification of nutrients and water stability as main determining factors influencing cyst signals has implications for cyst-based paleoenvironmental interpretations using transfer functions, which are developed almost exclusively from comparisons with more easily available data for sea-surface temperature, salinity, and sea ice.

Marine dinoflagellate cysts as indicators of eutrophication and industrial pollution: a discussion

The results from an investigation of dinoflagellate cysts as indicators of eutrophication in Tokyo Bay, Japan, by Matsuoka [Sci Total Environ 231 (1999) 17] are discussed with reference to other pertinent literature not discussed in the original article. Both the Japanese study and previous work from Norwegian fjords show that pollution (including cultural eutrophication) may produce changes in the phytoplankton reflected by a shift from more autotrophic--to more heterotrophic--dominance of cyst assemblages. However, this is a proportional change that seems likely to result from reduced autotrophic production rather than the increased heterotrophic production suggested by Matsuoka. This is not unequivocal evidence of eutrophication, since Tokyo Bay is impacted also by heavy industrial pollution, the possible effects of which cannot be distinguished, and the quantitative method used for estimating changes in cyst productivity is flawed.

Dinoflagellate cysts as potential indicators of industrial pollution in a Norwegian Fjord

Variation in dinoflagellate cyst assemblages through the last approximately 300 years was studied in two sediment cores, one from the heavily polluted Frierfjord, and one from the adjoining, relatively unpolluted Brevikfjord, in order to docu1ent possible dinoflagellate responses to pollution. Changes in the cyst-flora were compared with historical information on the development of industry and also with geochemistry of the sediments, reflecting aspects of pollution. In the Frierfjord core, increasing pollution was accompanied by a decrease in cyst concentration, possibly reflecting reduced production, at least of dinoflagellates, and a shift toward more heterotrophic species, possibly reflecting reduced light penetration in the euphotic zone, or increased production of prey for the heterotrophs. These trends seem to have reversed as pollution decreased after about 1975, suggesting that cyst assemblages contain signals that may prove useful for tracing the development of pollution. Cyst assemblages in the Brevikfjord core only showed minor changes.

Lipids as indicators of eutrophication in marine coastal sediments

Total organic carbon (TOC) and sedimentary lipid contents were investigated in the Bunnefjord, the most inner part of the Oslofjord (Norway). The Bunnefjord is an intermittent anoxic basin and has undergone major eutrophication since the early 1800s. A core from this fjord was collected at 100 m depths under anoxic remnant waters. The first 15 cm corresponding to deposits from 1500 to present were considered for analysis. Lipid classes were quantified by TLC-FID and the molecular composition of selected lipid classes was investigated by GC and GC-MS. Lipids were dominated by two main classes, phospholipids and hydrocarbons. The hydrocarbons represented up to 7.4% of total lipids in the sediment layers covering the period when the most extensive cultural eutrophication took place (1900 to 1970). The higher fluxes of organic carbon produced during this period may have controlled hydrocarbon inputs into the sediments, due to the hydrophobic character of these pollutants. The hydrocarbon concentration reversed toward pre-industrial levels in the more recent layers, which suggests an improvement of the water quality, possibly in response to improved treatment of the sewage in the cities around Bunnefjord. The second most abundant pool of lipids consists in phospholipids, mostly contributed by bacteria. Even though the concentration decreased with depth, their relative proportions to total lipids remained high, mainly in the deepest layers (>80% of total lipids). A rapid decrease of the polyunsaturated fatty acid methyl esters (FAME) from the phospholipid fraction in the upper 4 cm suggests a rapid biodegradation of planktonic inputs and meiofauna. Odd branched fatty acids were more probably contributed by bacteria linked to the high sedimentary hydrocarbon content. The down core distribution of 16:1omega7, 18:1omega7, 18:1omega5 esterified to phospholipids suggests a vertical zonation of the microbial community in relation to redox conditions and available organic matter. In addition to bacterial sulphur biomass, the presence of hopanoic acids in the phospholipids fraction suggests the contribution of bacteria growing on methane. According to the sterol composition, dominated by 4alpha(H)-methylsterols, dinoflagellates represent the major contributors to the organic matter produced in the water column, particularly during the period of extensive eutrophication. Long-chain diols (1,13-C(26), 1,15-C(30) and 1,15-C(32)) and long-chain keto-ols (1,15-C(30) and 1,15-C(32)) are reported for the first time at high latitudes. Their relative distributions (diol and keto-ol indexes of Versteegh et al. [Org. Geochem. 27 (1997)]) have allowed depicting a particular event during the eutrophication period, a freshwater intrusion with inputs of land-derived organic matter. This is in accordance with the downcore distribution of freshwater/terrestrial markers as sitosterol, dehydroabietic acid and iso- and anteiso-pimaric acids. The diol and keto-ol indexes have also underlined the general transition trend from marine to more brackish waters in the Bunnefjord. These last observations provide confidence into the use of these compounds in paleoenvironmental reconstruction.

Toxicity in Resting Cysts of the Red-Tide Dinoflagellate Gonyaulax excavata from Deeper Water Coastal Sediments

For the first time, Gonyaulax excavata cysts have been shown to be toxic. Bottom sediments from a water depth of 90 meters off the Maine coast were extremely rich in cysts, which were approximately ten times more toxic than the corresponding motile stages. Cysts are probably ingested by shellfish, thereby causing shellfish toxicity in deeper waters offshore and contributing to shellfish toxicity in shallower coastal waters. A new approach to the problem of paralytic shellfish poisoning is therefore needed, one that takes into account benthic cysts and sedimentary factors affecting their distribution. The possible dangers of spreading poisoning through human activities must be considered.

Spiniferites cruciformis: a fresh water dinoflagellate cyst?

Palynological studies of cored lacustrine sediments from the late Quaternary of Lake Kastoria, northern Greece, revealed a Late Glacial interval with abundant dinoflagellate cysts. Cyst assemblages include two identifiable species, Spiniferites cruciformis and Gonyaulax apiculata. The presence of the fresh water species G. apiculata is consistent with the lacustrine setting of these deposits, but that of S. cruciformis is anomalous. Previously, this species has only been recorded in abundance from presumed brackish marine sediments from the Black Sea and Marmara Sea sediments where geochemical data clearly record brackish salinities. Therefore, it has been regarded as a low salinity cyst type with a wide range of morphological variation that some workers have suggested to reflect salinity fluctuations. Specimens from Greece display only part of the range of morphological variability previously described from these (brackish) marine settings. Encountered morphological variation includes ellipsoidal/pentameral and cruciform endocyst shapes with rare intermediate shapes, and highly variable septa development. Specimens characterized by extremely reduced ornamentation known from (brackish) marine environments have not been recorded. Our records of S. cruciformis indicate that: (1) it could thrive in fresh water conditions; and (2) that apparently most of the strong morphological variations of the cysts are an intrinsic phenomenon for this taxon, and may only partly be linked to salinity variations as suggested earlier. We suggest that S. cruciformis essentially is a fresh water taxon, and that its records in (brackish) marine environments, with the exception of specimens with strongly reduced ornamentation, may be due to transportation, to short-lived fresh water surface conditions in such environments, or to tolerance of the species to brackish conditions.

Climate Change and Harmful Algal Blooms

Some authors have suggested that harmful algal blooms (HABs) are increasing throughout the world due to anthropogenic influences (Hallegraeff 1993). Others have stressed that climate variability may be an equally important contributor to the apparent increases (Sellner et al. 2003). Understanding the possible effects of climate change is therefore a critical requirement in the development of the risk assessments needed for the effective management of HABs. This chapter considers the effects of past, present and future climatic variability on HABs. The one thing we are certain of regarding climate is that it is changing – and it always has been. The geological and historical records show alternations between periods of relative warming and cooling at all timescales: extremes of glaciated to ice-free conditions on scales of millions of years to shorter-term oscillations on scales of a few to tens of years, such as the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). The last 1,000 years included periods as warm or warmer than now (at least in some regions) during the Medieval Warm Period (MWP), 550–1300 A.D., and colder than now during the Little Ice Age (LIA) 1300–1900 A.D. A major scientific effort is currently underway coordinated by the International Panel on Climate Change (IPCC) to assess the extent of human impact on climate, through the burning of fossil fuels, etc. This work has resulted in a much greater appreciation of the complex nature of climate, where temperature is only one of many factors to be considered. This complexity imposes a high degree of uncertainty on the predictive models used. There is a clear and convincing scientific consensus that anthropogenically forced global warming is taking place, but the extent of future warming, especially in the next 100 years, remains uncertain. In considering possible effects on phytoplankton, it is important to realize that at least in some regions, recent global warming has so far involved mainly a warming of winter temperatures. Continued