Notes for Chapter 1–7: Marine Plankton Nutritional Strategies, Shells, and Patchiness

Chapter 1: Introduction

  • Central question: organizing by how organisms obtain energy and food in the ocean, focusing on three broad nutritional strategies; the third is a combination of the first two.
  • Three main categories introduced:
    • Phytoplankton (photosynthetic producers)
    • Prefix: phyto- means plant; phototrophs obtain energy from sunlight via photosynthesis.
    • Term: phototrophs are energy carbon sources from sunlight; producers in the food web.
    • Zooplankton (animal consumers)
    • Prefix: zoo- means animal; obligate heterotrophs must consume other organisms to obtain energy and carbon.
    • They are typical consumers/predators of the marine food web.
    • Myxoplankton (mixotrophs; combination of strategies)
    • Prefix: myxo- suggests “mixed.”
    • Capable of both photosynthesis and consuming other organisms (combines above strategies).
    • Common informal shorthand in lectures: call them myxoplankton or myxoplantern for simplicity.
  • Practical implications:
    • Misclassification can occur: organisms identified as phototrophs may later be found to also ingest other organisms under certain conditions, moving them to the “myxophytoplankton” category;
    • The reverse update also happens, though less common; chloroplast-containing organisms may be misidentified if not studied long enough.
    • Terminology varies in the literature; the speaker emphasizes focusing on function (energy source) rather than strict labels when convenient.
  • Examples to expect later in the course:
    • Cyanobacteria (blue-green bacteria): photosynthetic prokaryotes; nitrogen fixation; significant in marine ecosystems; not algae (which are eukaryotes).
    • Phytoplankton (eukaryotic): include diatoms, coccolithophores, dinoflagellates, and others.
    • Zooplankton examples: various proto- and micro-animals that graze on phytoplankton or other small organisms.
  • Important notes about terminology and contexts:
    • Producers (photosynthetic) vs consumers (heterotrophs) as foundational roles in energy flow.
    • Chemosynthetic (chemosynthesizers) organisms exist and do not rely on sunlight; introduced later as “chemotropes” or geotrophs in discussions of hydrothermal vents.
    • The discussion will move to consider zooplankton, then revisit mixotrophs and broader ecological interactions.

Chapter 2: Blue Green Algae

  • Cyanobacteria overview
    • Etymology: cyano- means blue; cyanobacteria are photosynthetic prokaryotes, not algae (algae = eukaryotes).
    • Roles: photosynthesis; nitrogen fixation (convert inorganic N2 to organic nitrogen), expanding biologically usable nitrogen in the marine environment.
    • Ecological significance: early contributors of oxygen to Earth’s atmosphere; oxygen production linked to cyanobacterial metabolism (analogous to CO2 for respiration in animals).
    • Genomic/structural note: prokaryotes have DNA not enclosed in a nucleus.
  • Notable cyanobacteria group: Trichodesmium
    • Forms dense filaments and mats visible to the naked eye when concentrated; rapid population growth under suitable conditions.
  • Terminology clarification
    • Cyanobacteria are not algae; use cyanobacteria rather than blue-green algae to emphasize their bacterial nature.
  • Context for later discussion
    • Cyanobacteria are a major contributor to marine photosynthesis, often equalling eukaryotic phytoplankton in prominence in certain ocean regions.
  • Chapter transition note
    • The chapter transitions to a deeper look at specific phytoplankton types (diatoms and coccolithophores) and then to mixotrophic organisms (dinoflagellates).

Chapter 3: Bloom Of Diatoms

  • Diatoms: key photosynthetic phytoplankton with silica-based shells
    • Outer covering made of silica (SiO$_2$) forming intricate, radiating, symmetrical shells.
    • Some diatoms are solitary; others form chains; chain-forming diatoms create long cellular strings.
    • Morphology examples: sickle-shaped forms, star-like shapes, and elongated chains.
    • Buoyancy and sinking:
    • The heavy silica shell makes diatoms prone to sinking when they die; blooms can lead to rapid downward flux of organic matter to the seafloor.
    • Buoyancy strategies include active motion (limited for diatoms), buoyant internal lipids, and surface projections to increase surface area without excessive density.
  • Ecological role of diatoms
    • Primary producers; form the base of the food web in many ocean regions.
    • When diatom blooms crest and nutrients are depleted, they die and sink, contributing to deep-sea organic carbon flux.
    • Diatomaceous earth is sedimentary remains of diatom shells; significant in geology and soil science; often used as an indicator of past diatom productivity.
  • Coccolithophores (coccolithophores) overview (brief segue to next section)
    • coccolithophores have calcium carbonate (CaCO$_3$) plates (coccoliths) that armor the cell.
    • When they die, their CaCO$_3$ plates accumulate as sediment, contributing to chalk deposits and carbonate sediments.
    • They are small and form the base of the food web in many ocean regions; they also form blooms detectable by color change in surface waters.
  • Visual and conceptual notes
    • The camera images show cells and their hard outer coverings; diatoms’ silica shells are robust and contribute to rapid sinking after bloom demise.
    • The presence of hard shells (CaCO$3$ for coccolithophores, SiO$2$ for diatoms) is a useful indicator of nutrient requirements and ecological niches.
  • Microcontext: differences in shell chemistry across phytoplankton groups
    • Cyanobacteria lack a mineral shell; diatoms have silica shells; coccolithophores have calcium carbonate shells.
    • Shell material reflects nutrient availability and ecological strategies for buoyancy and protection.
  • Broader implications
    • Shell-forming organisms influence carbonate chemistry of oceans and sediments; their blooms tie into global biogeochemical cycles, paleoclimate records, and sedimentological processes.

Chapter 4: The Right Places

  • Bloom conditions and geographic tendencies
    • Dinoflagellates (mixed group including photosynthetic, heterotrophic, and mixotrophic species) tend to bloom in warm waters, often in tropical regions or during summer in temperate zones.
    • Red tides are dense blooms of dinoflagellates that discolor water (true, not false color imagery).
    • A notable density example: up to 8,000,0008{,}000{,}000 cells per liter in a red tide bloom.
    • Toxin dynamics: many dinoflagellate blooms produce internal toxins; when cells are damaged or predated upon, toxins can leach into seawater and accumulate in the food web, leading to issues such as paralytic shellfish poisoning.
  • Trophic and ecological implications
    • Dinoflagellates illustrate the three nutritional strategies (photoautotrophy, heterotrophy, mixotrophy) within a single group, with species examples across all three modes.
    • The shell morphology of dinoflagellates is distinct (two flagella, corkscrew swimming motion; one flagellum in a groove; another flagellum around the equator enabling spinning).
  • Broader nutrient considerations
    • The carbonate-based shell (CaCO$_3$) of coccolithophores requires calcium in seawater; diatoms and other siliceous shells require silica; cyanobacteria lack such shells.
    • The presence or absence of certain shell materials reflects environmental chemistry and nutrient availability in local ecosystems.
  • Aside on microbial and chemosynthetic life
    • Brief mention of chemosynthetic (chemotropes) organisms as producers that rely on chemical energy rather than sunlight; these organisms are typically associated with hydrothermal vents and will be discussed later.
  • Clarifications on taxonomy and complexity
    • Not all phytoplankton fit neatly into one category; some groups are more mixed in nutritional strategies, and taxonomy is evolving with new research.
    • The class uses an adaptable framework (phototrophs, heterotrophs, mixotrophs) to explain broad ecological roles, not rigid classifications.

Chapter 5: Little Shrinking Things

  • Forams and calcite oozes
    • Foraminifera (forams) are a zooplankton group that build calcium carbonate (CaCO$_3$) shells with chambered structures reminiscent of nautilus or gastropod shells.
    • They contribute to deep-sea sediment layers called oozes when they die and accumulate on the seafloor.
    • Oozes defined: sediment layers containing at least 30% remains of a particular organic group (the term “ooze” here has a precise geologic meaning).
    • If the sediment composition includes 30% or more of forams or other groups, that layer is considered an ooze; e.g., a foram ooze, a diatom ooze, etc. The speaker notes a casual mispronunciation, saying “goose” instead of “ooze,” which is likely a slip in the lecture.
  • Size and visibility
    • Foram shells are microscopic; visible only under magnification; typical sizes are on the order of hundreds of microns or smaller.
    • Their shells contribute to the sediment when sinking, forming part of deep-sea geology and paleoclimate records.
  • Conceptual takeaway
    • Forams illustrate calcite-based calcite shell formation in zooplankton and their role in deep-sea sedimentation processes.

Chapter 6: Think Of Chlorophyll

  • Patchiness in the ocean
    • Plankton distributions are patchy in space and time due to multiple interacting processes:
    • Transport by currents: oceanic gyres and major currents move organisms around.
    • Diffusion: spreading and mixing create irregular, “messy” spatial patterns.
    • Reproduction and growth: local nutrient availability drives blooms.
    • Grazing and predation: predators reduce local concentrations, creating hot and cold spots.
    • Organismal movement: although limits exist (plankton can’t outrun major currents), tiny vertical swimming and vertical positioning can influence local distribution.
  • Visual aid: satellite chlorophyll imagery vs. physical coastline
    • True-color satellite image shows surface water; true color depicts surface features, but chlorophyll concentration is inferred from spectral signals,
    • False-color chlorophyll maps show concentrations: purple/blue = low; green/yellow/orange/red = higher chlorophyll (photosynthetic organisms).
    • The interface between physical oceanography and biology is shown as a “ribbon” of high chlorophyll that indicates a bloom moving with currents;
    • Diffusion leads to a mosaic of high and low chlorophyll patches rather than a single uniform transport lane.
  • Concept of patchiness and transport mechanisms
    • Currents (e.g., Gulf Stream) create coherent features such as rings that can trap or release water masses and organisms.
    • Diffusion creates spread and mixing across small scales.
    • Organisms’ life cycles and growth rates contribute to temporal patchiness (seasonal blooms).
  • Interlude: research context and PD1 discussion
    • The instructor previews a paper discussion (Flomberg paper) and notes upcoming PD1 talks on “ends and rings” that influence patchiness and transport.
    • Encourages students to come prepared to discuss how papers address plankton dynamics, patchiness, and transport.
  • Connection to nutrient shells and ecological roles
    • The shells (CaCO$3$, SiO$2$, and organic materials) influence sinking rates, nutrient cycling, and the distribution of communities.

Chapter 7: Conclusion

  • Synthesis of patchiness and transport mechanisms

    • Patchiness arises from currents, diffusion, growth, grazing, and organismal movement; these processes act together across space and time to shape plankton distributions.
    • Large-scale oceanic currents create features like warm-core rings and cold-core rings around the Gulf Stream.

  • Gulf Stream rings as transport and mixing vehicles

    • Warm-core rings: detached warm water masses moving northwards from the Gulf Stream.
    • Cold-core rings: detached cold water masses moving southward or interacting with warmer masses.
    • Rings act as barriers and corridors for transport: they can trap water and organisms, but are also mechanisms by which plankton can cross major currents and exchange material between regions.

  • Ring dynamics and ecological implications

    • Rings are transient; they persist for weeks to about a month before breaking apart.
    • Ring cohesion and persistence depend on environmental conditions; during this time, some organisms survive and temporarily colonize the cooler or warmer waters within the ring, while others decline.
    • Survival outcomes are species-specific: some can tolerate the temperature shifts or adapt quickly, while others die off or migrate.

  • Take-home message

    • Understanding patchiness and transport is crucial for predicting nutrient flows, bloom dynamics, and the distribution of marine organisms across ecosystems.
    • The Gulf Stream and its rings are important natural mechanisms driving cross-gyre mixing and connectivity in marine ecosystems.

  • Quick recap of essential shell materials and their ecological implications

    • Calcium carbonate shells (CaCO$_3$) — coccolithophores; nutrient calcium availability influences distribution and sediment formation (chalk deposits).
    • Silica shells (SiO$_2$) — diatoms; heavy shells promote sinking after blooms; silica availability shapes diatom success.
    • Organic-based shells (cell walls, organic matrices) — many mixotrophs and other groups; less mineralized shells influence buoyancy and nutrient cycling.

  • Final reflection on microbial and ecological diversity

    • Photosynthetic contributions come from both cyanobacteria (Prochlorococcus, Synechococcus) and eukaryotic phytoplankton (diatoms, coccolithophores, dinoflagellates).
    • The ocean’s photosynthetic base is distributed globally with distinct regional patterns (blue and green bands on global maps reflect cyanobacteria and prochlorococcus abundances; diatoms dominate around certain high-nutrient zones like near Antarctica).
    • The traditional view of ocean photosynthesis has broadened to include significant prokaryotic contributions alongside eukaryotic algae.

  • Notes for study and future topics

    • Review the distinction between producers (phototrophs) and consumers (heterotrophs), and how mixotrophy blurs these lines.
    • Understand how shell chemistry (CaCO$3$, SiO$2$, and organic shells) relates to nutrient availability and ecological niches.
    • Remember key examples: cyanobacteria (nitrogen fixation; oxygen production), diatoms (silica shells; blooms; sinking), coccolithophores (CaCO$3$ shells; chalk deposits), dinoflagellates (red tides; toxins; dual/triple nutrition modes), forams (CaCO$3$ shells; deep-sea ooze).
    • Grasp how physical oceanography (currents, rings, diffusion) interacts with biology to create patchiness and influence distribution and bloom dynamics.