Microalgae Flashcards
What role do algae play in aquatic ecosystems?
They are primary producers, playing a role similar to terrestrial plants in nutrient and carbon cycling
Where are algae especially dominant?
In freshwater habitats (ponds, lakes, streams) and marine plankton communities
How do seaweeds on rocky shores demonstrate zonation?
Their distribution reflects tolerance to fluctuations in salinity, temperature, light, and humidity due to tides
What extreme conditions can polar seaweeds endure?
Months of darkness, grazing, pathogens, and harsh abiotic stress
What are kelp forests and why are they important?
Dense brown algal forests offshore that provide shelter and food to marine life and are harvested by humans
What types of algae can be encrusted with calcium carbonate?
Red, green, and brown algae
They contribute to long-term carbon sequestration
What organisms make up phytoplankton?
Photosynthetic microalgae (e.g., diatoms, dinoflagellates) and cyanobacteria
How do phytoplankton impact the global carbon cycle?
They fix CO₂ via photosynthesis and some also fix it into CaCO₃, which sinks to the seafloor
Responsible for ~50% of anthropogenic CO₂ uptake
What is ‘CO₂ drawdown’?
A process where calcified phytoplankton sink and remove CO₂ from the atmosphere by replacing it in ocean water
What is the sulphur-related role of haptophytes and dinoflagellates?
They produce sulphur compounds that influence atmospheric chemistry by promoting cloud formation
What causes algal blooms?
Nutrient enrichment (e.g., fertilizer runoff) combined with favorable light and temperature conditions
What are harmful algal blooms (HABs)?
Blooms that release toxins affecting wildlife and humans, often caused by dinoflagellates
What are some impacts of HABs?
Fish kills, respiratory illness in humans, and food web disruption
What is unique about dinoflagellate movement?
They spin as they swim using two dissimilar flagella in perpendicular grooves
What is peridinin?
A carotenoid pigment that masks chlorophyll a and c in dinoflagellates
Helps absorb light in different wavelengths
How do dinoflagellates reproduce?
Asexually via longitudinal division; also form resistant cysts under unfavorable conditions
What is a dinoflagellate resting cyst?
A dormant stage that settles on the seafloor and can remain viable for years until conditions improve
What is mixotrophy in dinoflagellates?
A feeding strategy combining photosynthesis with ingestion of prey via phagocytosis, peduncles, or pallium
What are zooxanthellae?
Symbiotic, photosynthetic dinoflagellates found in corals and other invertebrates, providing nutrients in exchange for shelter
How do dinoflagellates contribute to coral growth?
They photosynthesize and release glycerol used by corals, allowing growth in nutrient-poor waters
What is bioluminescence in dinoflagellates used for?
Anti-predator defense, either to startle predators or expose them to higher-level predators
What is Pfiesteria piscicida known for?
A dinoflagellate with a “hit-and-run” toxic feeding strategy causing fish kills and potential harm to humans
What illnesses are associated with dinoflagellate toxins?
Diarrhetic shellfish poisoning (DSP), neurotoxic effects (e.g., from Karenia brevis), and paralytic shellfish poisoning (e.g., saxitoxin)
