Week 3 Flashcards
What are the general features of phytoplankton?
Sizes range from single-celled (~1 µm) to large kelps (~30 m). No tissue differentiation like land plants. Classified by pigments, food storage, and cell wall composition (e.g., cellulose, silica). Use flagella for movement and can exhibit molecular diversity (16S/18S ribosomal RNA).
How did eukaryotic phytoplankton evolve?
Eukaryotic phytoplankton arose from primary endosymbiosis of cyanobacteria with an apoplastidic host. Secondary symbiosis produced diverse groups, including green algae, red algae, diatoms, cryptophytes, and haptophytes.
What is kleptoplasty?
Kleptoplasty is a symbiotic process where chloroplasts from algae are sequestered and utilized by a host organism, allowing it to perform photosynthesis temporarily.
What are distinguishing characteristics of eukaryotic phytoplankton?
Chloroplasts with thylakoid membranes. Silica-based cell walls in diatoms; calcium carbonate plates in coccolithophores. Flagella used for movement and stimuli response. Diverse pigments, including chlorophyll a, b, c, and accessory pigments.
What pigments are found in phytoplankton?
Chlorophylls: a (universal), b (green algae, land plants), c (diatoms, haptophytes). Accessory pigments: carotenoids (e.g., fucoxanthin), biliproteins (e.g., phycoerythrin). Pigment diversity reflects evolutionary adaptations.
How are phytoplankton samples collected?
Nets: Collect large organisms but lack depth precision. Bottles on CTD: Sample smaller organisms at specific depths. CPR (Continuous Plankton Recorder): Preserves samples for later analysis. VPR (Video Plankton Recorder): Captures images in situ.
How are phytoplankton samples quantified?
Light microscopy (e.g., Lugol’s iodine staining). Flow cytometry measures cell size and fluorescence (chlorophyll a, phycoerythrin). HPLC separates and quantifies pigments via fluorescence and absorption.
What are key features of cyanobacteria?
Prokaryotic, small (1 µm), no membrane-bound organelles. Use chlorophyll a and phycobilins for photosynthesis. Some form gas vacuoles for buoyancy or heterocysts for nitrogen fixation.
How do Prochlorococcus and Synechococcus differ?
Prochlorococcus: Dominates nutrient-poor waters; uses divinyl chlorophyll a and b. Synechococcus: Found at nutrient-rich boundaries; contains phycoerythrin and zeaxanthin.
What makes Trichodesmium unique?
Filamentous cyanobacteria that fix nitrogen in oligotrophic tropical waters. Gas vacuoles provide buoyancy. Form brownish blooms called ‘sawdust of the sea.’
What are picoeukaryotes, and why are they important?
Picoeukaryotes (<2 µm) include diverse taxa like pelagophytes and prasinophytes. They dominate production in nutrient-poor regions and exhibit divergent evolutionary histories.
What are diatoms, and how do they reproduce?
Unicellular or colonial phytoplankton with silica cell walls. Two-part frustules (epitheca and hypotheca). Undergo size reduction during asexual reproduction; return to original size via sexual reproduction.
What pigments and structures define diatoms?
Contain chlorophyll c and fucoxanthin, giving a brown color. Silica-based frustules serve as defense and promote sinking when dead.
What are haptophytes, and what is their ecological role?
Haptophytes (e.g., coccolithophores) are unicellular or colonial, often motile, with chlorophyll a, c, and 19-hexanoyloxyfucoxanthin. They form massive blooms in high-latitude and coastal systems.
What defines dinoflagellates?
Mostly unicellular with paired flagella. Cell walls may be armored with cellulose plates (thecate) or naked (athecate). Contain diverse pigments, often including peridinin. Some species are toxic or form harmful blooms.
What is Symbiodinium, and where is it found?
Symbiodinium is an endosymbiont in coral, sea anemones, and sponges, providing photosynthetic energy in exchange for shelter.
What is the importance of mixotrophic phytoplankton?
Mixotrophs combine autotrophy (photosynthesis) and heterotrophy (organic consumption), adapting to varying nutrient and light conditions.
How do molecular methods help classify phytoplankton?
Molecular methods, such as analyzing 16S ribosomal RNA (prokaryotes) or 18S ribosomal RNA (eukaryotes), reveal genetic diversity and phylogenetic relationships. These techniques uncover evolutionary histories and ecological niches.
What adaptations help Trichodesmium survive in oligotrophic waters?
Trichodesmium forms colonies for nitrogen fixation, uses gas vacuoles for buoyancy, and blooms in nutrient-poor tropical waters. Its ability to fix atmospheric nitrogen compensates for low nutrient availability.
Why is pigment diversity important in phytoplankton?
Pigment diversity allows phytoplankton to absorb a broad spectrum of light wavelengths, optimizing photosynthesis in varied light environments. For example, carotenoids absorb green/blue light, and biliproteins capture green light.
What distinguishes centric from pennate diatoms?
Centric diatoms: Radial symmetry, often chain-forming, common in coastal waters. Pennate diatoms: Bilateral symmetry, linear forms, adapted to benthic and pelagic environments.
How do gas vacuoles benefit cyanobacteria?
Gas vacuoles provide buoyancy, enabling cyanobacteria to adjust their position in the water column for optimal light and nutrient conditions, enhancing photosynthesis and survival.
What are the ecological roles of coccolithophores?
Coccolithophores form calcium carbonate plates, contributing to the biological pump by sequestering carbon in the ocean. Their blooms impact ocean color and carbon cycling, especially in high latitudes.
What role does silica play in diatom structure and function?
Silica-based frustules protect diatoms from grazers and environmental stress. Dead diatoms sink quickly, transporting carbon to the deep ocean, influencing biogeochemical cycles.
