Clarice M. Yentsch

Particle selection, ingestion, and absorption in filter-feeding bivalves

Abstract Measurements were made of the clearance rate of six bivalve species each in the presence of mixed cell suspensions of the dinoflagellate Prorocentrum minimum (Pavillard) Schiller (clone Exuv), the diatom Phaeodactylum tricornutum Bohlin (clone Phaeo), and the cryptomonad flagellate Chroomonas salina (Wislouch) Butcher (clone 3C). Use of flow cytometry allowed estimation not only of the clearance rate of individual cell types, but also of their proportional occurrence in the pseudofaeces and faeces. It has been recognized that at least three mechanisms of selecting suspended particles may be present in isolation or in combination. These are: (a) preferential clearance on the ctenidia: Ostrea edulis L., for example, preferentially clears the dinoflagellate Exuv compared with similar sized cells of the diatom Phaeo and the cryptomonad flagellate 3C; (b) preingestive selection on the labial palps: the diatom Phaeo was consistently and preferentially rejected in the pseudofaeces of Ensis directus Conrad, Placopecten magellanicus (Gmelin) and Arctica islandica (L.), (c) differential absorption in the gut i.e., post-ingestive selection: of the mixed diet which was ingested, there is clear evidence of a preferential absorption of the cryptomonad flagellate 3C in the majority of the bivalves from which we obtained faecal material. The possibility of selective removal of particular components of the available food resource, especially in the case of our experiments with the cryptomonad flagellate 3C, suggests that such organisms may be quantitatively more important in the diet of bivalves than their relative abundance under natural conditions might lead us to suppose. The ability of the oyster Ostrea edulis to selectively clear the dinoflagellate Exuv from mixed cell suspensions also may have important implications in our understanding of how toxic dinoflagellates may be concentrated on the ctenidia of commercially significant bivalves.

Sunlight and water transparency: cornerstones in coral research

Abstract Reef-building corals throughout the world are considered endangered. The evidence is a decline in coral health and reduced coral cover. Competing hypotheses for the cause of coral loss include removal of grazers, nutrient enrichment, disease, coral bleaching, increase in temperature, and excess light/ultraviolet exposure. We suggest that light limitation as a second order effect of anthropogenic activity (e.g. sediment resuspension and nutrient enrichment) is a valid and tractable hypothesis. This experimental field and laboratory study demonstrates that corals of the Florida reefs are functioning close to the compensation point where respiration (of coral polyp plus zooxanthellae) consumes the products of photosynthesis of the zooxanthellae, with little if any remaining for growth. We extend this work into an optical nomograph that is useful for predicting coral loss and recovery. The nomograph is designed to elucidate compensation depth for waters of various transparencies.

Influence of upwelling relaxation on dinoflagellates and shellfish toxicity in Ria de Vigo, Spain

Abstract Outbreaks of paralytic shellfish poisoning (PSP) along the north-west coast of Spain have become a serious threat to the extensive mussel farming industry in that region over the last decade. During the summer, high phytoplankton productivity is supported by the sustained upwelling of nutrient-rich deep water into the rias. An episode of PSP in the autumn of 1985 in Ria de Vigo coincided with the sudden appearance, rapid numerical increase, and dominance of two chain-forming dinoflagellates, Gymnodinium catenatum and Protogonyaulax affinis . Field data suggest that warm offshore surface water was transported into the ria as the summer upwelling ceased. This occurred when winds changed from northerly (upwelling favourable) to southerly or westerly (upwelling unfavourable); the injected water contained established populations of oceanic and neritic dinoflagellates. The simultaneous appearance and dominance of two dinoflagellates that form long chains leads us to speculate that the small-scale downwelling of water within the ria favoured efficient swimmers among the phytoplankton. These data not only implicate these two species as possible sources of the PSP toxins in local mussels, but they also suggest the feasibility of developing a bloom prediction capability for some dinoflagellate species based in part on an upwelling index that can indicate when offshore surface waters might be forced into the rias.

Selective feeding by Balanion sp. (Ciliata: Balanionidae) on phytoplankton that best support its growth

Abstract The planktonic ciliate, Balanion sp., feeds preferentially on certain dinoflagellates when confronted with mixtures of microalgae. The preferred prey are species which support its fastest growth (≈ 3 div./day at 15°C). At high food densities, Balanion can grow as rapidly in algal mixtures which contain its preferred prey as its corresponding monocultures. Balanion are found year-round in estuaries in which dinoflagellates are common but are only occasionally the dominant phytoplankters. Preferential ingestion of suitable dinoflagellate prey may thus increase the growth rate of this ciliate in situ.

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.

Automated Individual Cell Analysis in Aquatic Research

Publisher Summary This chapter discusses the automated individual cell analysis in aquatic research. Most living organisms in aquatic systems exist as independent, single-cell entities in a fluid medium. In even the most nutrient-impoverished oligotrophic waters of the world, small cells occur at nearly one million cells per liter. In more eutrophic waters, numbers per unit volume are several orders of magnitude higher. The examination and characterization of individual cells were preoccupations of early naturalists interested in aquatic ecosystems. For the most part, cells, whether occurring as solitary units or as multicellular organisms, are in the 1–100 μm size range. Generally in open waters, the smaller the cells, the numerous they are. Microscopes were essential tools for examining cells. In its infancy, the era of aquatic research was paralleled by an explosion of chemical assessment methods. Thus, there was a thrust to improve biological sampling through chemical measurement in dynamic aquatic systems. Many aquatic scientists were proponents of the application of rapid chemical assays that could be quantitative and intercalibrated in various parts of the world. In vivo methods were found to be even more rapid and permitted real-time assessment of the organisms in the water mass via continuous flow and analysis systems, which were also compatible with the physical scientists conductivity temperature-depth (CTD) measurements, the chemical scientists autoanalyzer nutrient measurements, and the optical scientists light transmission measurements. Combining these methodologies remains very useful for data acquisition from aquatic systems today.

Autofluorescence And Other Optical Properties As Tools In Biological Oceanography

Bulk fluorescence measurements have been popular in algal culture studies and in oceanographic and limnological applications. Usually, fluorescence is interpreted as an indicator of chlorophyll concentration or phytoplankton biomass, but sometimes measurements of fluorescence can be related to physiological properties of phytoplankton, such as responses to light. Now that in situ fluorometers are being deployed routinely with optical packages, there is active interest in interpreting the relationships between fluorescence, beam transmission, diffuse attenuation, and the physiological characteristics of phytoplankton. Flow cytometry offers the potential to extend these interpretations to the scale of individual cells. It may be difficult to compare measurements of fluorescence, however, because instruments differ greatly in excitation irradiance and time scale of measurement. With this in mind, we examined the short-term responses of a marine diatom to bright light, comparing different instruments (SeaTech in situ fluorometer, Turner Designs fluorometer, EPICS flow cytometer, FACS Analyzer, SeaTech beam transmissometer) while making concurrent measurements of photosynthesis vs irradiance and absorption spectra. Each fluorometer yielded somewhat different information, yet all showed a similar pattern of inhibition after exposure. One instrument, the in situ pulsed fluorometer, could show rapid changes of fluorescence immediately after large shifts of irradiance. Beam attenuation did not decline with the bright light treatment, nor did the specific absorption of chlorophyll. Photosynthetic efficiency was reduced after exposure to bright light, but the capacity for photosynthesis in high irradiance increased at the same time. These results are preliminary: nonetheless they support some interpretations of fluorescence/beam attenuation ratios, clarify some aspects of photosynthetic response to bright light, and suggest that flow cytometry may be useful for assessing physiological heterogeneity in phytoplankton assemblages.

Immunochemical approaches to coastal, estuarine, and oceanographic questions

Background of the Immune System.- Understanding the Immune System.- Background.- What Does the Immunological Approach Offer Aquatic Research? An Overview.- Molecular Biology, Single Cell Analysis and Quantitative Genetics: New Evolutionary Genetic Approaches in Phytoplankton Ecology.- Techniques.- The Production of Monospecific Antisera to Soft-Bottom Benthic Taxa.- Preparation and use of Monospecific Antisera to Capitella SP. I.- Cell Affinity Chromatography for a Marine Nitrifying Bacterium.- Application of Immunoblotting for Dietary Analysis.- Two-Dimensional Electrophoresis with Silver Staining: A Sensitive Method for Analyzing Complex Protein Mixtures.- Brevetoxins and Binding: Sodium Channels Versus Antibodies.- Preparation of Model Haptens to Express Common Epitopes of PSP Toxins.- Monoclonal Antibodies (Monoabs) to Ciguatoxin and Related Polyethers.- Immunofluorescent Reagents: Preparation and Analysis.- Flow Cytometry and Immunofluorescence in Aquatic Sciences.- Detection Schemes for Antigen-Antibody Reactions.- Applications.- Identification of Marine Chroococcoid Cyanobacteria by Immunofluorescence.- An Immunofluorescence Approach toward the Identification of Endosymbiotic Diatoms in Several Species of Larger Foraminifera.- Immunofluorescent characterization of the Eukaryotic Ultraplankton.- Probes for Assessing Single-Cell Primary Production: Antibodies Againstribulose-1, 5-Bisphosphatecarboxylase (RuBPCASE) and Peridinin/Chlorophyll a Protein (PCP).- Examining Nitrate Reduction by Phytoplankton with an Immunoassay.- A Possible immunological Approach to The Study of Plasmalemma Redox Enzymes in Phytoplankton.- Antiluciferase Immunogold Labeling of two Different Organelles in the Marine Dinoflagellate Gonyaulax Polyedra.- Enzyme-Linked Immunosorbent Assay for Metal-Binding Proteins of Mytilus Edulis.- Environmental induction of Teleost cytochrome P-450 Detected by Immunochemical Analysis.- Quantifying Stomach Contents Using Immunoassays: A Critique.- Euphausiid predation on Larval Anchovy at two Contrasting Sites off California Determined with an Elispot immunoassay.- Enzyme immunoassay Utilizing Monoclonal Antibodies for identification of European Eel Virus (EEV), an Aquatic Birnavirus.- Monoclonal Antibodies to Atlantic Salmon (Salmo Salar) Immunoglobulin: Production And Preliminary Characterization.- Immunochemical evaluation of The infectious Pancreatic Necrosis (IPN) Carrier State in Salmonids and Other species.- References.

Phytoplankton optical properties: flow cytometric examinations of dilution-induced effects.

Flow cytometry is used to measure dilution-induced changes in the optical properties of Dunaliella tertiolecta-light scatter, cell fluorescence, and refractive index. Observed changes in cell optical properties are compared to simultaneous measures of cell volume and count, extracted chlorophyll a concentration, and the (14)C uptake rate. Flow cytometric measurements reveal short-term dilution effects (within 1 h of dilution) that, are not evident in other morphological or physiological measurements such as cell volume, extracted chlorophyll a concentration, and (14)C uptake rate. Data are presented which suggest that these short-term changes in cell optical properties are the result of changes in the real component of refractive index, possibly due to a rapid and temporary rearrangement of the internal cellular structure. Long-term changes are observed in time series measurements of cell volume and count, extracted chlorophyll a concentration, and (14)C uptake rate.

Observations on the intra- and interspecific single cell optical variability of marine phytoplankton

Phytoplankton occur as a wide variety of sizes, shapes, textures, and conformational inclusions. Optical reseachers, however, to date represent phytoplankton in models as uniform or varying by only a small amount. We give evidence here of changes in the distribution of light scatter for single cells of individual species. This observation is noted even within one species. Optical characteristics show ranges of intraspecific variability (as functions of physiological or nutritional state) comparable in magnitude to interspecific variability. Such variability may be attributed to changes in the cellular refractive-index distribution and the cell size and shape.