Marine Botany, Phycology, and Ecophysiology

Flashcards covering endosymbiotic origins, algal systematics, diatom and dinoflagellate morphology and ecology, harmful algal blooms, environmental stressors, and photosynthesis/chlorophyll fluorometry.

Primary Endosymbiosis

The evolutionary event in which a heterotrophic eukaryotic host engulfed a free-living, photosynthetic cyanobacterium, which over time was reduced to a double-membraned plastid vertically transmitted to subsequent generations, establishing the Archaeplastida lineage.

Secondary Endosymbiosis

The process whereby a heterotrophic eukaryote engulfs a photosynthetic eukaryote (an alga) that already possesses a primary plastid, producing complex plastids surrounded by three or four bounding membranes.

Tertiary Endosymbiosis

An endosymbiotic event in which a eukaryote engulfs another eukaryote that previously acquired its plastid via secondary endosymbiosis, observed in dinoflagellates and leading to the acquisition of diatom-, haptophyte-, or cryptophyte-derived plastids.

Endosymbiotic Gene Transfer (EGT)

The evolutionary transfer of genetic material from the genome of an engulfed ancestral organelle or endosymbiont into the host cell's nuclear genome.

Archaeplastida

The monophyletic lineage of eukaryotes that acquired chloroplasts through a single primary endosymbiotic event with a cyanobacterium, comprising Glaucophyta, Rhodophyta (red algae), and Chloroplastida (green algae and land plants).

Cyanelles (Muroplasts)

The primitive double-membraned plastids found in Glaucophyta that retain a peptidoglycan cell wall layer between their inner and outer membranes, characteristic of their ancestral cyanobacterial origin.

Nucleomorph

The vestigial, highly reduced nucleus of an engulfed eukaryotic algal endosymbiont located within the periplastid space between the second and third membranes of complex plastids in cryptomonads (Cryptista) and chlorarachniophytes.

Chloroplast Endoplasmic Reticulum (CER)

The outer membrane system surrounding secondary plastids, whose outermost membrane is physically continuous with the outer nuclear envelope of the host cell.

Kleptoplasty

A mechanism by which a heterotrophic organism ingests photosynthetic prey and retains its functional chloroplasts (kleptoplastids) temporarily to utilize photosynthetically fixed carbon before the plastids degrade or are digested.

Frustule

The rigid, external siliceous cell wall characteristic of diatoms, comprised of two overlapping halves (valves) fitted together like a petri dish or lidded box.

Epitheca

The slightly larger, older 'top' half of a diatom frustule that overlaps the smaller hypotheca.

Hypotheca

The slightly smaller 'bottom' half of a diatom frustule that fits inside the epitheca and is newly formed during asexual vegetative division.

Copula (Girdle Band)

A thin siliceous connecting band that encircles the diatom frustule, linking the epivalve and hypovalve together.

Areola

A regularly repeated pore perforating the siliceous diatom valve wall, functioning in the exchange of water, dissolved gases, and nutrients.

Raphe

A longitudinal slit or groove perforating the valve wall of pennate diatoms, through which mucilage is extruded to enable gliding motility across surfaces.

Rimoportula (Labiate Process)

A specialized siliceous tubular structure through the valve wall of centric diatoms that extrudes polysaccharides and other organic carbon compounds.

Size Diminution

The progressive reduction in mean cell size of a diatom population during successive rounds of asexual mitotic division, caused by each daughter cell forming a new, smaller hypovalve inside the parent valve.

Auxospore

A specialized diatom cell or zygote formed following sexual reproduction (meiosis and syngamy) that expands to restore maximal vegetative cell size.

Chrysolaminarin

The primary soluble $\beta\text{-1,3-glucan}$ carbohydrate storage product accumulated in cytoplasmic vesicles of diatoms and other heterokonts.

Fucoxanthin

The dominant accessory carotenoid pigment found in diatoms and brown algae that absorbs blue-green light and imparts their characteristic golden-brown coloration.

Amphiesma

The complex, multi-layered cell covering of dinoflagellates, consisting of an outer and inner cytoplasmic membrane enclosing cellulose thecal plates inside flattened vesicles.

Cingulum (Girdle)

The transverse groove encircling a dinoflagellate cell that accommodates the ribbon-like transverse flagellum and delineates the cell into an anterior epicone and a posterior hypocone.

Sulcus

The longitudinal groove on a dinoflagellate cell running perpendicular to the cingulum that houses the posteriorly directed longitudinal flagellum.

Transverse Flagellum

The flattened, wave-like flagellum of a dinoflagellate that lies within the cingulum and generates rotational and forward propulsive thrust.

Longitudinal Flagellum

The whip-like flagellum extending posteriorly along the sulcus of a dinoflagellate that controls swimming direction and cell orientation.

Peridinin

A unique, ancestral light-harvesting carotenoid pigment characteristic of photosynthetic dinoflagellates harboring three-membrane secondary plastids derived from red algae.

Diel Vertical Migration (DVM)

The synchronized movement of motile dinoflagellates ascending into surface waters during daylight to maximize photosynthesis and descending into deeper, nutrient-rich layers at night.

Myzocytosis

A cellular feeding method employed by certain predatory dinoflagellates in which the cell pierces the prey's outer membrane and siphons out internal cellular contents.

Harmful Algal Bloom (HAB)

A rapid proliferation or accumulation of microscopic algae or cyanobacteria that causes adverse ecological, economic, or human health impacts through toxin secretion or environmental degradation.

Paralytic Shellfish Poisoning (PSP)

A human toxic syndrome caused by ingesting shellfish contaminated with saxitoxins and related analogs synthesized by dinoflagellates such as Alexandrium catenella and Gymnodinium catenatum.

Saxitoxin

A potent, neurotoxic alkaloid produced by certain marine dinoflagellates and cyanobacteria that selectively blocks voltage-gated sodium channels in nerve and muscle cells.

Brevetoxins

Cyclic polyether neurotoxins produced by dinoflagellates such as Karenia brevis and Karenia cristata that cause Neurotoxic Shellfish Poisoning (NSP) and extensive marine faunal mortality.

Domoic Acid

A potent water-soluble neurotoxin produced by diatoms of the genus Pseudo-nitzschia that acts as a glutamate receptor agonist, causing Amnesic Shellfish Poisoning (ASP) in humans.

Eutrophication

The enrichment of an aquatic ecosystem with inorganic plant nutrients, notably nitrogen and phosphorus, typically stimulating excessive primary productivity and phytoplankton blooms.

Environmental Driver

Any physical, chemical, or biological factor in the environment that influences or induces changes in the physiology, growth, or distribution of an organism or ecosystem.

Environmental Stressor

An environmental driver whose intensity or concentration exceeds an organism's physiological tolerance threshold, resulting in metabolic disruption or decreased fitness.

Limitation Stress

A stress condition caused by an insufficient supply of essential resources—such as light, dissolved inorganic carbon, or nitrogen—that restricts metabolic rates, growth, or reproduction without inflicting cellular structural damage.

Disruptive Stress

A stress condition that induces direct cellular or physiological injury, such as membrane disintegration, protein denaturation, or oxidative damage, demanding metabolic repair.

Emersion

The regular aerial exposure of intertidal macroalgae and marine organisms during low tide, subjecting them to desiccation, thermal extremes, and carbon limitation.

Osmotic Potential ($\psi_\pi$)

The chemical potential of water molecules governed by solute concentration, where higher concentrations of dissolved solutes yield increasingly negative $\psi_\pi$ values.

Turgor Pressure

The internal hydrostatic pressure exerted outward by the plant or algal protoplast against the rigid cell wall, required to drive cellular expansion and mechanical rigidity.

Euryhaline

Describing organisms capable of withstanding and functioning across a broad range of environmental salinity levels.

Stenohaline

Describing organisms restricted to an extremely narrow range of environmental salinity levels due to limited osmoregulatory capacity.

Compatible Solute

A low-molecular-weight, uncharged organic osmolyte (such as mannitol, proline, or sucrose) that accumulates within the cytoplasm to regulate cell water potential without inhibiting enzymatic activities.

Heat Shock Proteins (HSPs)

A conserved family of molecular chaperones synthesized under thermal stress to prevent irreversible denaturation, assist refolding of polypeptides, and maintain proper protein conformations.

Concentration Boundary Layer (CBL)

A stagnant, unstirred thin fluid layer immediately adjacent to an algal thallus surface where solute transport is governed primarily by molecular diffusion rather than bulk water convection.

Michaelis-Menten Uptake Kinetics

A hyperbolic nutrient transport model characterizing carrier-mediated active uptake across an algal membrane, characterized by a rapid initial increase in uptake rate with substrate concentration that asymptotically approaches a maximum capacity ($V_{\text{max}}$).

Biphasic Nutrient Uptake

A nutrient transport pattern characterized by saturable Michaelis-Menten kinetics at low external substrate concentrations coupled with a linear, non-saturating diffusive uptake mechanism at elevated concentrations.

Nitrate Reductase

The primary cytoplasmic enzyme catalyzing the two-electron reduction of inorganic nitrate ($NO_3^-$) to nitrite ($NO_2^-$) using electrons donated by $NAD(P)H$.

Nitrite Reductase

The plastidic enzyme that catalyzes the six-electron reduction of toxic nitrite ($NO_2^-$) into ammonium ($NH_4^+$) utilizing reduced ferredoxin.

Non-Photochemical Quenching (NPQ)

A regulated photoprotective mechanism whereby excess singlet excitation energy absorbed by light-harvesting complexes is harmlessly dissipated as thermal energy (heat) instead of driving photochemistry or singlet oxygen formation.

Xanthophyll Cycle

A light-driven, enzymatic interconversion of specific carotenoid pigments—such as diadinoxanthin to diatoxanthin in diatoms—that modulates excess excitation dissipation as heat.

Photoinhibition

A sustained light-induced reduction in photosynthetic efficiency and capacity that arises when the rate of photon capture and photochemical excitation exceeds the capacity for utilization and repair of Photosystem II (PSII).

Dynamic Down-Regulation

A rapid, reversible physiological closure and functional down-regulation of photosynthetic reaction centers during excess irradiance to avert photodamage.

Photosynthesis-Irradiance (P-I) Curve

A graphical representation plotting gross or net photosynthetic rate as a function of incident photon irradiance, utilized to quantify photoacclimation and light use parameters.

Photosynthetic Efficiency ($\alpha$)

The initial, linear slope of a Photosynthesis-Irradiance curve representing light-limited photochemical efficiency under low-light regimes.

Maximum Photosynthetic Rate ($P_{\text{max}}$)

The asymptote on a Photosynthesis-Irradiance curve representing the light-saturated maximum photosynthetic capacity of an organism under optimal biochemical conditions.

Saturating Irradiance ($E_k$)

The irradiance level marking the onset of photosynthetic saturation, calculated mathematically as the ratio of maximum photosynthetic rate to light-limited efficiency ($E_k = \frac{P_{\text{max}}}{\alpha}$).

Compensation Irradiance ($E_c$)

The specific light intensity on a Photosynthesis-Irradiance curve at which the rate of gross photosynthetic oxygen production equals the rate of respiratory oxygen consumption, resulting in net zero gas exchange.

Minimum Fluorescence ($F_o$)

The baseline chlorophyll fluorescence emission yield measured under non-actinic measuring light in dark-adapted tissue when all Photosystem II (PSII) reaction centers are fully oxidized and open.

Maximum Fluorescence ($F_m$)

The maximal chlorophyll fluorescence emission yield elicited by applying a saturating pulse of actinic light to dark-adapted tissue, temporarily closing all Photosystem II (PSII) reaction centers.

Maximum Quantum Yield of PSII ($F_v/F_m$)

A standardized proxy for the maximum photochemical efficiency of Photosystem II, computed as $\frac{F_m - F_o}{F_m}$ following dark adaptation.

PAM Fluorometry

Pulse-Amplitude-Modulated fluorometry; a non-destructive optical methodology that selectively measures chlorophyll fluorescence kinetics under modulated light to quantify photochemical quantum yield and non-photochemical dissipation.