1. Introduction.- 2. Taxonomy and Species Features.- 2.1 Introduction.- 2.2 Species List.- 2.2.1 Spinose Planktonic Foraminifera.- 2.2.2 Non-spinose Planktonic Foraminifera.- 3. Collecting and Culture Methods.- 3.1 Introduction.- 3.2 Collection for Ecological Studies.- 3.3 Fixation and Storing of Samples.- 3.4 Laboratory Preparations.- 3.5 Collection for Physiological and Ecological Studies.- 3.5.1 Net Collection.- 3.5.2 SCUBA Collection.- 3.6 Isolation and Preparation for Maintenance Culture.- 3.7 Maintenance Cultures.- 3.8 Monitoring Vitality and Growth of the Cultures.- 3.9 Feeding Techniques.- 3.9.1 Algal Prey.- 3.9.2 Animal Prey.- 3.10 Cataloguing and Storing Shells.- 3.11 Summary.- 4. Cellular Ultrastructure.- 4.1 Introduction.- 4.2 Fixation of Planktonic Foraminifera for Fine Structure Analysis.- 4.3 Cytoplasmic Streaming.- 4.4 Peripheral Cytoplasm and Rhizopodial Morphology.- 4.4.1 Cytoskeletal Structures.- 4.4.2 Filaments.- 4.5 Fine Structure of Cytoplasmic Organelles.- 4.5.1 Nucleus.- 4.5.2 Mitochondria.- 4.5.3 Peroxisomes.- 4.5.4 Endoplasmic Reticulum, Golgi Complex, and Vacuolar System.- 4.5.5 Fibrillar Bodies.- 4.5.6 Lipids and Various Cytoplasmic Inclusions.- 4.6 Comparative Fine Structure Data of Benthic and Planktonic Species.- 4.7 Comparative Fine Structure of Planktonic Foraminifera and Radiolaria.- 4.8 Summary.- 5. Host and Symbiont Relationships.- 5.1 Introduction.- 5.2 Symbiosis, Commensalism and Parasitism.- 5.3 Symbiont Morphology and Structural Association with Host.- 5.3.1 Dinoflagellate Symbiont Fine Structure.- 5.3.2 Chrysophycophyte Symbiont Fine Structure.- 5.4 Symbiont and Host Physiological Interactions.- 5.5 Origin of Symbionts.- 5.6 Major Features of Algal Symbionts.- 5.7 Summary.- 6. Trophic Activity and Nutrition.- 6.1 Introduction.- 6.2 Natural Prey.- 6.3 Laboratory Studies of Trophic Activity.- 6.3.1 Prey Acceptance and Rate of Digestion.- 6.3.2 Cannibalism.- 6.3.3 Fine Structure Studies of Prey Capture and Digestion.- 6.3.4 Trophic Activity and Longevity.- 6.3.5 Laboratory Studies of Omnivorous Feeding.- 6.4 Prey Abundance and Foraminiferal Distribution.- 6.5 Predators on Planktonic Foraminifera.- 6.6 Comparative Data with Benthic Foraminifera and Radiolaria.- 6.7 Summary.- 7. Reproduction.- 7.1 Introduction.- 7.2 Gametogenesis.- 7.2.1 Light Microscopic Data.- 7.2.2 Fine Structure Data.- 7.3 Morphological Changes during Gametogenesis.- 7.4 Reproductive Cycles.- 7.5 Comparisons with Benthic Foraminifera and Radiolaria.- 7.6 Summary.- 8. Shell Ontogeny.- 8.1 Introduction.- 8.2 Ontogenetic Concept for Spinose Species.- 8.2.1 Five Stage Concept.- 8.2.2 Ontogeny of Globigerinoides sacculifer.- 8.3 Variations in Developmental Morphology of Spinose Species.- 8.4 Variations in Developmental Morphology of Non-spinose Species.- 8.5 Quantitative Ontogeny.- 8.6 Coiling Directions.- 8.7 Taxonomic Applications.- 8.8 Summary.- 9. Shell Architecture.- 9.1 Introduction.- 9.2 Chamber Deposition and Pore Formation.- 9.2.1 Chamber Formation in Non-spinose Species.- 9.2.2 Pore Formation and Wall Thickening.- 9.2.3 Keel Development.- 9.2.4 Pustule Formation.- 9.3 Chamber Formation in Spinose Species.- 9.3.1 Spine Types.- 9.4 Wall Thickening and Gametogenic Calcification.- 9.5 Physiological Mechanism and Rates of Calcification.- 9.6 Organic Composition of the Calcitic Wall.- 9.7 Resorption and Repair Processes.- 9.8 Abnormal Shell Growth.- 9.9 Summary.- 10. Ecology.- 10.1 Introduction.- 10.2 Statistical Treatment and the Transfer Function.- 10.3 Stable Isotopes.- 10.4 Distributional Pattern of Planktonic Foraminifera.- 10.4.1 Horizontal Distribution.- 10.4.2 Seasonal Distribution.- 10.4.3 Vertical Distribution.- 10.4.4 Patchiness and Daily Vertical Migration.- 10.4.5 General Sea Surface Temperature in the Past.- 10.5 Population Dynamics.- 10.5.1 Reproductive Strategies.- 10.5.1.1 Lunar Periodicity.- 10.5.1.2 Annual Periodicity.- 10.5.2 Water Mass Boundary Effects.- 10.6 Experimental Studies.- 10.7 Summary.- 11. Sedimentation - Settlement of Shells.- 11.1 Introduction.- 11.2 Shells Released by Reproduction and Juvenile Mortality.- 11.3 Aggregates - Sedimentation.- 11.4 Predation.- 11.5 Residence Time and Sinking Velocity.- 11.6 Seasonal Fluctuations in the Settlement.- 11.7 Dissolution in the Deep Water.- 11.8 Summary.- 12. Concluding Remarks.- 12.1 Effects Influencing the Isotopic Signal.- 12.1.1 Temperature Effect.- 12.1.2 GlacialEffect.- 12.1.3 Water Mass Effect.- 12.1.4 VitalEffect.- 12.1.5 Selective Production.- 12.1.6 Differential Dissolution.- 12.2 Carbon Isotopes.- 12.3 Summative Perspective.- 13. References.- 14. Glossary.- 15. Index.

Modern Planktonic Foraminifera

Organic detritus passing from the sea surface through the water column to the sea floor controls nutrient regeneration, fuels benthic life and affects burial of organic carbon in the sediment record1–3. Particle trap systems have enabled the first quantification of this important process. The results suggest that the dominant mechanism of vertical transport is by rapid settling of rare large particles, most likely of faecal pellets or marine snow of the order of >200 μm in diameter, whereas the more frequent small particles have an insignificant role in vertical mass flux4–6. The ultimate source of organic detritus is biological production in surface waters of the oceans. I determine here an empirical relationship that predicts organic carbon flux at any depth in the oceans below the base of the euphotic zone as a function of the mean net primary production rate at the surface and depth-dependent consumption. Such a relationship aids in estimating rates of decay of organic matter in the water column, benthic and water column respiration of oxygen in the deep sea and burial of organic carbon in the sediment record.

Particulate organic carbon flux in the oceans—surface productivity and oxygen utilization

Characteristics, dynamics and significance of marine snow

Rapid mass sinking of cells following diatom blooms, observed in lakes and the sea, is argued here to represent the transition from a growing to a resting stage in the life histories of these algae. Mass sinking is of survival value in those bloom diatoms that retain viability over long periods in cold, dark water but not in warm, nutrient-depleted surface water. Mechanisms for accelerating sinking speed of populations entering a resting or “seeding” mode are proposed. Previously unexplained features of diatom form and behaviour take on a new meaning in this context of diatom seeding strategies. Diatoms have physiological control over buoyancy as declining growth is accompanied by increasing sinking rates, where the frustule acts as ballast. Increased mucous secretion in conjunction with the cell protuberances characteristic of bloom diatoms leads to entanglement and aggregate formation during sinking; the “sticky” aggregates scavenge mineral and other particles during descent which further accelerates the sinking rate. Such diatom flocs will have sinking rates of ∼ 100 m d-1 or more. This is corroborated by recent observations of mass phytoplankton sedimentation to the deep sea. This mechanism would explain the origin of marine snow flocs containing diatoms in high productivity areas and also the well-known presence of a viable deep sea flora. That mortality is high in such a seeding strategy is not surprising. A number of species-specific variables pertaining to size, morphology, physiology, spore formation and frustule dissolution rate will determine the sinking behaviour and thus control positioning of resting stages in the water column or on the bottom. It is argued that sinking behaviour patterns will be environmentally selected and that some baffling aspects of diatom form and distribution can be explained in this light. Rapid diatom sedimentation is currently believed to be mediated by zooplankton faecal pellets, particularly those of copepods. This view is not supported by recently published observations. I speculate that copepod grazing actually retards rather than accelerates vertical flux, because faecal pellets tend to be recycled within the surface layer by the common herbivorous copepods. Egestion of undigested food by copepods during blooms acts as a storage mechanism, as ungrazed cells are likely to initiate mass precipitation and depletion of the surface layer in essential elements. Unique features of diatoms are discussed in the light of their possible evolution from resting spores of other algae. An evolutionary ecology of pelagic bloom diatoms is deduced from behavioural and morphological characteristics of meroplanktonic and tychopelagic forms. Other shell-bearing protistan plankters share common features with diatoms. Similar life-history patterns are likely to be present in species from all these groups. The geological significance of mass diatom sinking in rapidly affecting transfer of biogenic and mineral particles to the sea floor is pointed out.

Role of sinking in diatom life-history cycles: ecological, evolutionary and geological significance

Macroscopic organic aggregates, which are >500 µm and known as marine and lake snow, are important components in the turnover, decomposition and sinking flux of both organic and inorganic matter and elements in aquatic ecosystems. They are composed of various organic and inorganic materials depending largely on the given system and environmental conditions. The sys- tems include the pelagic limnetic, the neritic and oceanic marine region, as well as shallow turbid environments, e.g. rivers, the littoral zone of lakes, estuaries and tidally affected coastal areas with intense turbulence and a high load of suspended matter. Aggregate abundance and size vary greatly among these systems. Macroaggregates are heavily colonized by bacteria and other heterotrophic microbes and greatly enriched in organic and inorganic nutrients as compared to the surrounding water. During the last 15 yr, many studies have been carried out to examine various aspects of the formation of aggregates, their microbial colonization and decomposition, nutrient recycling and their significance for the sinking flux. They have been identified as hot-spots of the microbial decomposi- tion of organic matter. Further, microaggregates, which are <5 to 500 µm in size and stained by different dyes, such as transparent exopolymer particles (TEP) and Coomassie blue-stained particles, have been discovered and shown also to be important in the formation and decomposition of macroaggregates. In this review we give an overview of the present state of the microbial ecology of macro- and microaggregates, including the mentioned points but highlighting in particular the recent findings on the bacterial colonization of aggregates using molecular tools, their microbial decomposition and mineralization, and the significance of protozoans and metazoans for the colo- nization and decomposition of macroaggregates. Today it is evident that not only the aggregates but also their surroundings are sites and hot-spots of microbial processes, with the plume of solutes leak- ing out of the aggregates and greatly extending the volume of the intense decomposition processes. This microheterogeneity has important implications for the spatial and temporal dynamics of the organic-matter field in aquatic ecosystems and for our understanding of how heterotrophic organisms are involved in the decomposition of organic matter. The significance of aggregate-associated micro- bial processes as key processes and also for the overall decomposition and flux of organic matter- varies greatly among the various systems, and is greatly affected by the total amount of suspended particulate matter. A conclusion from the presented studies and results is that the significance of bac- teria for the formation and decomposition of aggregates appears to be much greater than previously estimated. For a better understanding of the functioning of aquatic ecosystems it is of great impor- tance to include aggregate-associated processes in ecosystem modeling approaches.

/pdf/microbial-ecology-of-organic-aggregates-in-aquatic-1kw4w22q3c.pdf

Microbial ecology of organic aggregates in aquatic ecosystems

The sinking rate of intact marine snow (macroscopic aggregates) was determined in settling chambers on seven occasions in Monterey Bay, California and in the northeastern Atlantic. Sinking rates ranged from 43 to 95 m day−1 (average 68 m day −1). The average calculated flux from the upper 20 m of the water column was 30.7 × 104 aggregates m−2 day−1. These calculations suggest that from 3 to 5% of the POC (particulate organic carbon) and 4% to 22% of the PON (particulate organic nitrogen) standing stocks were removed from the surface water each day by the sinking of marine snow.

Marine snow: sinking rates and potential role in vertical flux

In near-surface waters of the neritic zone, the fragile aggregate material called "marine snow" is enriched by a variety of planktonic organisms and detrital products of plankton Here marine snow is a source of patchiness and taxonomic diversity for microplankton populations and is a likely food resource and recycling agent for fecal particles

http://science.sciencemag.org/content/sci/201/4353/371.full.pdf

Marine snow: microplankton habitat and source of small-scale patchiness in pelagic populations.

Measurements of ammonia, nitrite, nitrate, and phosphate indicate significant differences in nutrient concentrations associated with marine snow from those of the surrounding water, In eight sets of nutrient measurements, ammonia was more concentrated in aggregates in seven sets, nitrite in three sets, and nitrate in one set, Phosphate was more concentrated in one set, but less concentrated in three sets. Aggregates represent nutrient micropatches ranging in size from <I mm to several centimeters in diameter.

Jonathan D. Trent

Papers

Marine snow: sinking rates and potential role in vertical flux

Marine snow: microplankton habitat and source of small-scale patchiness in pelagic populations.

Marine snow: Microscale nutrient patches1