Study Notes on Plankton

Plankton
  - Free-floating organisms in the ocean.
  - Their movement is primarily influenced by ocean currents and waves rather than their own motility.
  - Primarily small (microscopic), but size is not a strict definitional criterion.

Femtoplankton:
  - Size: < 0.2 micrometers
  - Includes: Viruses, referred to as virioplankton.
  - Distribution: Ubiquitous, found in every marine environment.
    - Example: Marine viruses stained by SYBR Green.
Picoplankton:
  - Size: 0.2 to 2 micrometers
  - Composition: Archaea (bacteria-like extremophiles capable of living in extreme environments) and Bacteria.
    - Archaea examples: Found in hydrothermal vents, anoxic sludge, and polar ice.
Nanoplankton:
- Size: 2 to 20 micrometers
- Includes: Protists (e.g., silicoflagellates, coccolithophores, and cryptophytes), which are single-celled organisms belonging to the domain Eukarya.
Microplankton:
- Size: 20 to 200 micrometers
- Mainly consists of plant-like plankton (e.g., diatoms and dinoflagellates).
Mesoplankton:
- Size: 0.2 to 20 mm
- Composed mainly of animal plankton.
Macroplankton:
- Size: 2 to 20 cm
- Includes: Krill (important part of the marine food web), and is sometimes described as a size range for ingested plankton.
Megaplankton:
- Size: 20 to 200 cm
- Includes species such as jellyfish (e.g., Moon Jelly, Nomura’s jellyfish which can reach lengths of up to 2 m) and floating seaweeds (e.g., Sargassum).

Producers vs. Consumers:
  - Phytoplankton:
    - Primary producers, including diatoms and dinoflagellates.
  - Zooplankton:
    - Primary consumers, animal-like organisms, which feed on phytoplankton.

Diatoms:
- Phytoplankton with a unique box-and-lid siliceous frustule structure made of SiO₂ (silica).
Dinoflagellates:
- Responsible for phenomena like red tides, with toxic impacts highlighted by the Dungeness crab fishery disaster in 2015.
Coccolithophores:
- Calcareous phytoplankton contributing to sediments, recognizable in formations like the White Cliffs of Dover made from chalk.
Cyanobacteria:
- Not classified as protists, but are significant since they are considered vast contributors to primary production in marine ecosystems (approximately 90% NPP).

Concept:
- Illustrates biomass distribution among different trophic levels: the lower trophic levels (like phytoplankton) have greater biomass versus higher levels (like secondary consumers).

Zooplankton:
- Consume phytoplankton and some also predate on other zooplankton.

Copepods:
  - Account for approximately 70% of all zooplankton in marine samples.
  - Include anatomical features such as a cyclopian naupliar eye and antennules for filter feeding.
  - Feeding Mechanism:
    - Filter feeding via appendages that create a feeding current, allowing food to pass through.
Chaetognaths (Arrow Worms):
- Use mouthparts with claws for raptorial feeding.
- Define raptorial feeding as utilizing two-sided jaws/claws to capture prey.
Larvaceans:
- Small zooplankton that construct a mucous house for feeding, related closely to sea squirts.
Siphonophores:
- Colonial organisms working cooperatively with different body parts, each acting as separate individuals while being functionally interconnected.
Pteropods:
- Related to snails and characterized by a calcareous shell, but not meroplankton.
Ctenophores:
- Known as comb jellies with unique ctene structures.
- Are jellyfish-like yet belong to a different phylum (Ctenophora) with non-toxic tentacles.

Holoplankton:
- Organisms that spend their entire lives in the planktonic stage.
Meroplankton:
- Organisms that start as plankton but later transition to other life stages, including juvenile forms of various aquatic species (e.g., fish, crabs).
- Examples include larval stages of crabs, snails, sea stars, jellyfish, and fish, which later metamorphose into forms that are no longer considered plankton.

The life cycle of meroplankton entails stages such as:
  - Zoea: larval stage of crabs.
  - Veliger: typical stage of bivalves.
  - Pluteus: larval forms of echinoderms.
  - Planula: free-swimming or crawling larvae of certain organisms.
  - Alevin: early developmental stage of fish post-hatching.
Summary: Meroplankton transforms through various stages into non-plankton life forms, resulting in a shifting ecological role as organisms mature from planktonic to more complex, multicellular structures.