Phytoplankton & Marine Plants Lab | Mr. Brown's Marine Biology

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Diatoms

Single-celled algae encased in intricate glass houses made of silica. Diatoms are responsible for 20% of global oxygen production and form the base of many marine food chains.

🔬 What Makes Diatoms Special?

Diatoms have cell walls called frustules made of silica (glass). These frustules have incredibly intricate patterns—so precise they were historically used to test microscope quality! When diatoms die, their glass shells sink and accumulate as diatomaceous earth, used in everything from pool filters to toothpaste.

Centric Diatoms

Coscinodiscus, Thalassiosira

Radially symmetrical (circular) diatoms that dominate open ocean plankton. Their disk shape allows them to float near the surface for photosynthesis.

Planktonic Radial symmetry

Pennate Diatoms

Navicula, Pinnularia

Elongated, bilaterally symmetrical diatoms often found attached to surfaces. Some can actually glide along surfaces using a slit called a raphe.

Benthic Can move!

Chaetoceros

Chaetoceros spp.

Recognizable by long silica spines (setae) that help them stay buoyant. One of the most abundant diatom genera in the ocean and crucial food for copepods.

Chain-forming Has spines

Diatom Diversity

Various genera

There are over 100,000 diatom species! Their stunning geometric patterns include triangles, stars, chains, and intricate radial designs.

100,000+ species Art in nature

📚 Key Concepts: Diatoms

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Frustule: The silica (glass) cell wall of a diatom, made of two overlapping halves like a petri dish.

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Diatom Bloom: Rapid population explosion in spring when nutrients and light increase. Blooms can color the water brown.

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Biological Pump: When diatoms die, their heavy glass shells sink rapidly, carrying carbon to the deep ocean—a crucial carbon sequestration process.

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Dinoflagellates

Spinning, whip-tailed microorganisms that blur the line between plant and animal. They cause bioluminescence, red tides, and some even hunt other cells!

🔬 What Makes Dinoflagellates Unique?

Dinoflagellates have two flagella (whip-like tails) that make them spin as they swim—their name means "whirling whip." About half are photosynthetic, half hunt other organisms, and some do both! They're responsible for bioluminescent ocean glow and harmful red tides.

Ceratium

Ceratium furca

Recognizable by their horn-like projections. These photosynthetic dinoflagellates are common in Long Island waters and can form large blooms.

Photosynthetic Horned

Noctiluca (Sea Sparkle)

Noctiluca scintillans

The main cause of bioluminescent "glowing waves"! This heterotrophic dinoflagellate eats other plankton and lights up blue when disturbed.

Bioluminescent Predator

Karenia brevis

Causes Florida's notorious red tides. Produces brevetoxins that kill fish, make shellfish toxic, and cause respiratory irritation in humans near affected beaches.

Harmful bloom Toxic

Zooxanthellae

Symbiodinium spp.

These dinoflagellates live inside coral tissue, providing up to 90% of the coral's energy through photosynthesis. When stressed, corals expel them—causing coral bleaching.

Symbiotic Coral partner

📚 Key Concepts: Dinoflagellates

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Bioluminescence: Chemical light produced when dinoflagellates are disturbed. The enzyme luciferase oxidizes luciferin, releasing blue light.

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Harmful Algal Bloom (HAB): Rapid dinoflagellate growth that can produce toxins, deplete oxygen, or discolor water ("red tide").

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Mixotrophy: Some dinoflagellates can both photosynthesize AND eat other organisms—the best of both worlds!

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Ocean Bacteria

Invisible but essential—marine bacteria drive the ocean's nutrient cycles, break down organic matter, and even help fish glow in the dark!

🔬 The Hidden Majority

There are approximately 1 billion bacteria in every liter of seawater! Despite being invisible, they form the foundation of marine nutrient cycling. Without bacteria, dead organisms would never decompose, and nutrients would be locked away forever.

SAR11 (Pelagibacter)

Pelagibacter ubique

The most abundant organism on Earth! These tiny bacteria make up 25% of all ocean microbes. They have the smallest genome of any free-living organism.

Most abundant Tiny genome

Vibrio

Vibrio spp.

Comma-shaped bacteria found in coastal waters. Some species (V. vulnificus) can cause serious infections from raw oysters or wounds exposed to seawater.

Pathogenic Warm water

Aliivibrio fischeri

Bioluminescent bacteria that live in the light organs of Hawaiian bobtail squid! They use "quorum sensing"—only glowing when enough bacteria are together.

Bioluminescent Symbiotic

Sulfur Bacteria

Thioploca, Beggiatoa

Chemosynthetic bacteria that get energy from sulfur compounds instead of sunlight. They thrive at hydrothermal vents and in oxygen-depleted sediments.

Chemosynthetic Extremophile

📚 Key Concepts: Ocean Bacteria

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Microbial Loop: Bacteria consume dissolved organic matter and are then eaten by protists, recycling nutrients back into the food web.

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Quorum Sensing: Bacteria "count" their population using chemical signals, turning on group behaviors (like glowing) only when enough are present.

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Chemosynthesis: Making energy from chemical reactions instead of sunlight—allows life in the deep ocean without photosynthesis.

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Cyanobacteria

The blue-green bacteria that invented oxygen! These ancient photosynthesizers changed Earth's atmosphere and still produce much of the oxygen we breathe today.

🔬 The Oxygen Makers

Cyanobacteria are NOT true algae—they're bacteria that can photosynthesize! About 2.4 billion years ago, cyanobacteria caused the Great Oxidation Event, filling Earth's atmosphere with oxygen for the first time. Modern cyanobacteria still produce an estimated 20-30% of Earth's oxygen.

Prochlorococcus

Prochlorococcus marinus

The smallest and most abundant photosynthetic organism on Earth! Discovered only in 1986, it produces ~20% of the oxygen in our atmosphere.

Smallest photosynthesizer Oxygen producer

Trichodesmium (Sea Sawdust)

Trichodesmium erythraeum

Forms visible floating mats in tropical oceans. It's a nitrogen-fixer—converting atmospheric nitrogen into usable form, fertilizing the ocean!

Nitrogen fixer Colonial

Spirulina

Arthrospira platensis

A spiral-shaped cyanobacterium grown commercially as a superfood supplement. Contains up to 70% protein and was eaten by the Aztecs!

Edible High protein

Microcystis

Microcystis aeruginosa

Forms harmful blooms in warm, nutrient-rich waters. Produces microcystins—liver toxins dangerous to wildlife and humans. Climate change is increasing blooms.

Harmful bloom Freshwater

📚 Key Concepts: Cyanobacteria

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Great Oxidation Event: ~2.4 billion years ago, cyanobacteria produced so much oxygen they transformed Earth's atmosphere, enabling complex life.

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Nitrogen Fixation: Converting atmospheric N₂ into ammonia (NH₃) that other organisms can use. Only certain bacteria can do this!

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Endosymbiosis: Chloroplasts in plants evolved from cyanobacteria that were engulfed by ancient cells—we still carry their descendants!

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Seaweed & Marine Plants

From towering kelp forests to delicate seagrass meadows—explore the macroscopic photosynthesizers that create underwater habitats.

🔬 Seaweed vs. Seagrass: What's the Difference?

Seaweeds are algae—they lack true roots, stems, or leaves and absorb nutrients directly through their blades. Seagrasses are true flowering plants with roots, stems, leaves, and even flowers that pollinate underwater! They evolved from land plants that returned to the sea.

🟤 Brown Algae (Phaeophyta)

Giant Kelp

Macrocystis pyrifera

The fastest growing organism on Earth—up to 2 feet per day! Forms underwater forests up to 150 feet tall, supporting thousands of species.

Brown algae Fastest growing

Sargassum

Sargassum natans/fluitans

The only seaweed that lives its entire life floating in the open ocean! The Sargasso Sea is named after it. Provides critical habitat for sea turtles, fish, and eels.

Brown algae Floating

🔴 Red Algae (Rhodophyta)

Irish Moss

Chondrus crispus

Source of carrageenan, a thickener used in ice cream, toothpaste, and countless foods. Common on Long Island's rocky shores.

Red algae Food additive

Nori

Pyropia/Porphyra spp.

The seaweed wrapped around sushi! Cultivated in Asia for over 1,000 years. High in protein, vitamins, and umami flavor.

Red algae Edible

🟢 Green Algae (Chlorophyta)

Sea Lettuce

Ulva lactuca

Thin, translucent green sheets found worldwide in shallow waters. Edible and high in iron. Can indicate nutrient pollution when it blooms excessively.

Green algae Indicator species

🌱 True Marine Plants (Seagrasses)

Eelgrass

Zostera marina

Long Island's most important seagrass! Provides nursery habitat for bay scallops, seahorses, and countless fish. Declining due to water quality issues.

True plant Long Island native

Turtle Grass

Thalassia testudinum

The dominant seagrass of Florida and the Caribbean, named for the green sea turtles that graze on it. Wider blades than eelgrass.

True plant Turtle food

📚 Key Concepts: Seaweed & Marine Plants

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Pigment Depth: Brown, red, and green algae have different pigments that absorb different wavelengths, allowing them to photosynthesize at different depths.

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Blue Carbon: Seagrass meadows capture carbon 35x faster than rainforests, storing it in sediments for centuries—critical for climate regulation.

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Ecosystem Engineers: Kelp and seagrass create 3D habitat structure, providing shelter, food, and nursery areas for hundreds of species.

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Organism Matching Game

Test your knowledge! Match each organism to its correct description.

How to Play

Click an organism on the left, then click its matching description on the right. Match all 10 pairs to complete the game!

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🔬 Organisms

📝 Descriptions

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Congratulations!

You've matched all the organisms!

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