About Microalgae:

• Microalgae are microscopic algae, typically found in freshwater and marine systems. 
• They are unicellular species that exist individually or in chains or groups.
• They are comprised of unicellular algal species, g. green algae, diatoms, and dinoflagellates.
• Depending on the species, their sizes can range from a few micrometers (µm) to a few hundreds of micrometers.
• The color of the algae is influenced by the predominant pigments in an algal cell. Thus, they are grouped according to their color: green, red, or brown. 
• Unlike higher plants, microalgae do not have roots, stems, or leaves.
• They are mostly photosynthetic. Their ability to photosynthesize is due to the presence of photosynthetic pigments. 
• Those that lack photosynthetic pigments are heterotrophs and therefore feed on other organisms.
• Importance:
  • They form the base of the food chain, providing essential nutrients for zooplankton, small fish, and other aquatic organisms. They are a primary food source for filter-feeding organisms.
  • Photosynthetic microalgae play a vital role in the global carbon and oxygen cycles. They absorb carbon dioxide and produce oxygen through photosynthesis, which helps mitigate climate change and contributes to oxygen generation. They produce approximately half of the atmospheric oxygen.
  • Microalgae can form symbiotic relationships with other organisms. For example, they live within the tissues of corals (zooxanthellae) and provide them with nutrients through photosynthesis.
  • Some of them are also capable of fixing nitrogen. Eg: Nostoc, Anabaena, and Oscillatoria.
  • They are rich in nutrients and can serve as a food source for humans. Spirulina and Chlorella, two types of microalgae, are often consumed as dietary supplements.

What is Macroalgae?

• Macroalgae, commonly called seaweeds, are marine plants that photosynthesize, but reproduce without flowers.
• They are visible to the naked eye (in contrast to microalgae) and generally grow attached to the seabed or reef substrate.
• They are important components of the reef ecosystem, providing food and habitat to a diverse range of species while also playing a key role in nutrient dynamics. 

What is an algal bloom?

• An algal bloom is the overgrowth of microscopic algae or algae-like bacteria in fresh, salt, or brackish waters.
• They are a result of excess nutrients from fertilizer, wastewater, and stormwater runoff, coinciding with lots of sunlight, warm temperatures, and shallow, slow-flowing water.
• Depending on the type of algae or bacteria that cause it, an algal bloom may produce bad-smelling scum, foam, froth, or a paintlike slick.
• Algal blooms can be many colors, including blue-green, yellow, brown, pink, and red.
• A harmful algal bloom, or HAB, is a bloom that produces toxins that are dangerous to humans and potentially other organisms.
• Not all algal blooms are toxic.