Algae 2

Eukaryotic Algae (Chromalveolates/Chromista)

Introduction

  • Final algal lecture, marine angiosperms (flowering plants) to be discussed later.

  • Focus on eukaryotic algae, which possess membrane-bound organelles, are more advanced, and generally larger than bacteria.

Chromalveolates (Chromista)

  • Today's lecture covers the Chromalveolates, also known as Chromista.

  • Includes brown algae and several smaller groups, some ecologically and commercially important (food, aquaculture).

  • Some chromists cause problems or diseases in aquaculture.

Serial Endosymbiosis

  • Cyanobacterium consumed by a flagellated organism led to photosynthetic single-celled organisms.

  • This gave rise to green and red algae.

  • Red algae underwent another endosymbiotic event, leading to more complex variations.

  • The haptophytes, heterochonts (including brown algae and diatoms), dinoflagellates, and other groups belong to this category.

Habitats

  • Mixture of marine and freshwater species.

  • Ochrophytes or Chromista include brown algae (Phaeophyceae), diatoms (Bacillariophyceae), and other planktonic groups.

  • Most are marine, but some have freshwater examples.

  • Golden-brown algae include haptophytes, cryptophytes, dinophytes (dinoflagellates), and euglenophytes (not discussed in detail).

Haptophytes

  • Produce a golden-brown color due to chlorophyll a (present in all photosynthetic organisms), chlorophyll c, and fucoxanthin derivatives.

  • These pigments mask the green of chlorophyll a and allow absorption of light at different wavelengths.

  • Store photosynthetic products as crizolaminaran.

  • Possess two flagella and a unique structure called a haptonema.

  • All are unicellular and flagellated, allowing them to swim.

  • Chloroplasts have thylakoids stacked in groups of three, a common feature related to serial endosymbiosis.

  • Cell covering consists of cellulose, common in these algae, but haptophytes can also have calcified scales.

  • Calcium carbonate fixation allows absorption of large amounts of carbon dioxide.

  • These scales make them heavy, promoting sinking.

  • Important for carbon sequestration to counter climate change.

  • Massive phytoplankton blooms absorb significant carbon dioxide, which is fixed into scales that sink upon bloom demise.

  • ~500 species of mostly marine nanoplankton.

  • Emiliania huxleyi is commonly cited in literature for large blooms.

  • Some species used in aquaculture and biotechnology.

  • Cultured for their fine calcium carbonate used in various processes.

Haptonema

  • Specialized flagella-like structure, but with dissimilar internal structure.

  • Contains a fold of endoplasmic reticulum, providing more cellular control.

  • Unlike regular flagella which only vibrate, the haptonema can move like a tentacle to capture food (e.g., bacteria).

  • Haptophytes are heterotrophic (eating other organisms) and photosynthetic.

  • Can be condensed or fully extended to capture food.

Coccoliths

  • Calcium carbonate scales on the cell surface.

  • Help maintain position in the water column just below the surface.

  • Involved in balancing ions in the water, improving photosynthetic efficiency.

  • Thought to be major global producers of calcium carbonate.

  • Remove carbon dioxide from the atmosphere and water column.

  • Upon bloom death, they sink and remove carbon dioxide, depositing it as deep-sea sediment.

Blooms

  • Produce some of the largest plankton blooms (e.g., Bering Sea).

  • Scale of blooms can be thousands of square kilometers.

  • Massive productivity and carbon dioxide absorption.

  • Blooms die, and the cells sink.

Cryptophyta

  • Also golden brown due to chlorophyll a, phycocyanin, and phycoerythrin.

  • Phycocyanin and phycoerythrin are the same pigments as in cyanobacteria, showing evolutionary links.

  • Store starch in the cytoplasm (like land plants) and oils.

  • Oils help maintain buoyancy, crucial for phytoplankton to stay in the photic zone.

  • Have two unequal hairy flagella, showing transition of different evolutionary lineages.

  • All are unicellular flagellates, swimming in plankton.

  • Plastids have thylakoids single or in pairs.

  • Phycobilin pigments are embedded in the thylakoid lumen.

  • Possess a chloroplast endoplasmic reticulum, enabling communication between the nucleus and organelles.

  • Cell covering made of protein-based periplast (structured shell) with polygonal plates.

  • ~200 species found in both marine and freshwater environments, planktonic.

Kilomonas

  • Contains ejectosomes which release slime when disturbed.

  • This slime can asphyxiate fish in aquaculture pens by clogging their gills.

  • Endoplasmic reticulum encapsulates the chloroplast for enhanced control.

Dinophyta (Dinoflagellates)

  • Golden brown due to chlorophyll a, chlorophyll c2, peridinin, dinoxanthin, and diadinoxanthin.

  • Store starch in the cytoplasm (like land plants) and lipids (fats).

  • Lipids maintain buoyancy.

  • Two dissimilar flagella in both length and orientation for corkscrew-like swimming motion.

  • One flagellum trails behind, pushing the cell, while the other wraps around the cell's girdle, causing it to spin.

  • All are unicellular flagellates, with some filamentous forms.

  • Plastids have thylakoids in stacks of three, surrounded by three membranes, indicating triple serial endosymbiosis.

  • Cell covering with vesicles containing cellulose plates.

  • ~2,000 mostly marine species.

Habitat

  • Many are planktonic, but some form symbiotic relationships (e.g., zooxanthellae).

  • Zooxanthellae reside inside corals, providing energy for reef building via photosynthesis.

  • Released during coral bleaching, redevelop flagella and swim as part of the plankton.

  • Can be absorbed and released by corals depending on life history and stress.

  • Symbiodinium associated with symbiotic relationships in corals, giant clams, sponges, etc.

Toxicity

  • Some are toxic, like Alexandrium.

Morphology

  • Exhibit diverse shapes with plates on the outside of the cell.

  • Have specialized structures like veins or spines to maintain position in the water column.

  • Can form cyst stages.

  • Some species have up to 37 different life history stages, making them hard to track and predict.

Internal Structure

  • Trailing and girdle flagella. The girdle flagellum is in a groove, causing the cell to spin.

  • Mesokaryotic nucleus with always-condensed chromosomes.

  • Vesicles contain oil for buoyancy.

Toxic Blooms (Red Tides)

  • Some are toxic; others cause fish kills due to deoxygenation.

  • Toxins can accumulate in fish and cause sickness in humans.

  • Toxins affect neural networks, altering the sense of temperature, causing paralysis, or affecting heart function.

  • Ciguatera poisoning from consuming large fish (e.g., grouper) that have accumulated toxins through bioaccumulation.

Toxic Microalgae Effects

  • Paralytic shellfish poisoning

  • Diuretic shellfish poisoning

  • Neurotoxic shellfish poisoning

  • Amnesic shellfish poisoning

  • Ciguatera fish poisoning

  • Some cause bioluminescence.

Ochrophyta

  • Large group including brown algae and diatoms.

  • Possess chlorophyll a and brown masking pigments like chlorophyll c, fucoxanthin, and vorscheryxanthin

  • Store crizolaminaran.

  • Have a long, hairy flagellum with two rows of stiff hairs and a shorter, smooth flagellum.

  • Variable morphology, from single-celled diatoms to giant kelps (40+ meters).

  • Plastids have thylakoids in stacks of three and a chloroplast endoplasmic reticulum.

  • Cell covering varies.

Diatoms (Bacillariophyceae)

  • Unique silica (glass) cell wall in two halves (like a petri dish).

  • Intricately sculpted and used to calibrate microscopes.

  • The silica cell wall includes pores enabling gases and nutrients exchange.

  • The cell wall cannot grow much except around the edges after division

  • One side will produce a new cell wall inside itself, and it will stay the same size through the generations.

  • What happens to the inside cell wall? It's just going to get gradually smaller.

  • Inner cell wall will get smaller and smaller through generations until it undergoes sexual reproduction.

Pores in Silica Cell Wall

  • Clusters of small pores enable gas exchange and nutrient uptake.

  • Sculpturing maintains position in the water column.

  • Can join together in filaments.

  • Use spines and other structures to avoid sinking and gas-filled hollow tubes.

Commercial Uses of Diatoms

  • Diatomaceous earth: Deposits of diatom shells uplifted to the surface. Used as an abrasive and filter material.

  • Swimming pool filters: Used as a filter until sand filters became more prevalent.

Pheophyceae (Brown Algae)

  • Most people think of them as seaweeds (kelps).

  • Have chlorophyll a, c, and fucoxanthin.

  • Multicellular, benthic, and entirely marine.

  • Include the largest marine plants (40+ meters).

  • Varied life histories.

Life Cycles of Pheophyceae

  • Meiosis produces gametophytes (male and female).

  • Gametes (egg and sperm) fuse to form a zygote, then a spore-producing stage (sporophyte).

  • Spores undergo meiosis, returning to the gametophyte stage.

  • Isomorphic alternation of generations: Gametophyte and sporophyte are morphologically similar.

  • Heteromorphic alternation of generations: Morphologically dissimilar, usually a large sporophyte and smaller gametophyte.

  • Reduced gametophyte stage: The gametophyte is reduced significantly, encased cells in the sporophyte.

  • Examples are Fucus and local example Hormosira.

Commercial Uses of Brown Algae

  • Alginates: Cell wall cellulose used as a gelling agent.

  • Harvested, dried, and ground up for thickening agents.

  • Harvested off of France and the state using the Scooby Doo method

  • Machines such as ships are used to harvest them.

  • Used for gelling and thickening commercial products.