Meroplankton: 

Benthic Invertebrates

• 70% marine species have a juvenille planktonic stage (egg or larvae)
• could be minutes, months, or years
• either eaten or settle onto suitable substrate and metamorphose into adult
• deep sea species often lack the planktonic stage due to lack of food 

Shelled Veliger larva

• benthic invertebrate meroplankton 
• snails and clams
• ciliated membrane (velum) for food collection and locomotion 

bipinnaria of starfish

(meroplankton: benthic invertebrate)

Polychaete trochophore

(early stage larva)

• meroplankton: benthic invertebrate
• several bands of cilia
• develops a segmented body and appendages

Polychaete 

(late stage larva)

• later stage of polychaete trochophore
• meroplankton: benthic invertebrate

Barnacle nauplius larva

• meroplankton: benthic invertebrate
• free-swimming
• usually 6 stages

Crab Zoea

• meroplankton: benthic invertebrate
• stages of development separated by molting

Crab megalopa

• meroplankton: benthic invertebrate
• settled form of the larva that resembles adult 

Barnacle cypris

• meroplankton: benthic invertebrate
• attaches to substrate
• metamorphoses to the adult form 

Ichthyoplankton

(eggs + larvae)

Eggs...

• attach to substrate, free floating
• varying amounts of yolk (less time in egg = less yolk) and oil (more oil floats at a different level in the water column)
• rate of development is species-specific and affected by temp.
• large + few eggs vs. small + many eggs 

Pleuston

• suface zooplankton with an over water portion
• rich in warm and tropical water

Neuston

• zooplankton at surface of the water BUT all under water 
• rich in topical and warm waters

Siphonophore: Physalia

• holoplankton: cnidaria
• stinging cells on tentacles that are up to 10m
• pleuston/neuston
• jump out of water to avoid predation

Velella (by the wind sailor)

• pleuston/neuston
• jump out of water to avoid predation
• short tentacles
• captures food (copepods) very near surface
• turtles + suface molluscs feed on them 

Glaucus

• Pleutson/neuston
• counter-shading to avoid predation
• nudibranch
• float upside down at surface using air in digestive tract sacs
• eats Physalia, Velella, and ingests nematocysts triggering them, then cilia move them to dorsal surface where they become protection vs. predators

Janthina

• pleustion/neuston
• builds mucus-encased bubble rafts to hang upside down from
• east Physalia and Velella

Halobates

• Pleuston/neuston
• only insect in open ocean
• east Physalia, Velella, and copepods

Epipelagic Plankton

• below neuston (200-300m deep)
• euphotic --> disphotic
• many herbivores and omnivores
• high diversity, mostly small and transparent organisms (to avoid predation)
• zooplankton may be permanent here or migrate in/out of zone

Salps

• Epipelagic plankton 
• omnivore
• provide nutrients to deep water via fecal matter
• 
  

Larvaceans

• Epipelagic plankton
• omnivore
• form marine snow = move production to deep water

Thecosomatus pteropods

• epipelagic plankton
• omnivore

Copepods & Smaller Crustaceans

• epipelagic plankton
• herbivores 

Sargassum Weed

• a genus of brown algae with ~150 species
• MOST are temperate intertidal
• most famous are free-floating and pelagic
• large clumps occur in Sargasso Sea in the western Atlantic 
• provide habitat and shelter for entire specialized communities

Sargassum Frog Fish

Sargassum Crab

• in sargassum weed

Loggerhead Turtle Hatchling

• in sargassum weed

Flying Fish

• in sargassum weed

Sargassum Nudibranch

Mesopleagic plankton

• 200-300m --> 1000m
• larger than epipelagic relatives even though gelatinous (b/c no wave action deep down)
• some larger species partly herbivorous with nightly migration into epipelagic
• most carnivorous or detritivores 
• black/red coloring + big eyes with sensitivity to blue/green light

Vampire Squid

• mesopelagic plankton
• adapted to life at oxygen minimum zone
• 400-800m depth, density gradient causes accumulation of fecal material --> high bacterial growth and bacterial grazers --> respiration reduces oxygen content from 4-6mg/l to <2mg/l

Deep Sea Larvacean

mesopelagic plankton

Bioluminescence

• enzyme (luciferase) reaction in special cells (photophores)
• bact., dinoflag., inverts., fishes
• communication? predator defense? counter-illumination? lure?

Bathy- (1K-3/4Km)

Abbysso- (>3/4Km)

pelagic plankton

• zooplankton and fish dark red/black colored with small eyes
• fewer species, fewer individuals (less productive waters)
• longer generation times, lower fecundity (lots of energy into 1 offspring)
• bioluminescence occurs 
• 
  

Benthic environments

• demersal or epibenthic: live near or temporarily on sea floor
• like: bottom-dwelling fish, plaice, and crustaceans

Problems with vertical 

• 1. individuals and species are not uniformly distributed b/w these depths + many species may morve b/w depths ( deeper zones blur)
• 2. zone of a species can change with latitude 

Zooplankton

categories: what they eat (ex. herbivore)

Size

Habitat (oceanic vs. neritic)

length of residency in pelagic (holoplankton vs. meroplankton)

Collection Methods for zooplankton

Patchy distributions + broad size range = challenging

• concentrated using "net tow"
• now, optical plankton counters = standard

Dinoflagellate

•  holoplankton: protozoa
• gelatinous sphere >1mm
• eats small zooplankton, diatoms, etc.
• it eats by generating currents or extending cytoplasmic trap
• dense swarms near coast 

Foram

• holoplankton: protozoa
• CaCO3 perforated shell with chambers
• 30 µm to mm
• very abundant 40'N to 40'S
• eat bact., phytos., smalls zooplank. by capture with pseudopodia
• paleo importance: foraminiferan ooze

Radiolarian

•  Holoplankton: protozoa
• spherical amoeboid with central silica based capsule
• 50µm to mm
• occur everywhere but most common in cold or deep
• eat bact., phytos., protists and crustaceans by capture with branched pseudopodia
• paleo impt: radiolarian ooze

Zooflagellate

• holoplankton: protozoa
• colorless, strictly heterotrophic
• 2-5 µm, abundant when bloom
• eat bact., detritus
• 20-80% of nanoplankton --> important food source for zooplankton

Ciliate: Tintinnid

• large subgroup of Ciliates > 1000 species
• eat 4-60% of coastal phytos

Ciliates

• holoplankton: protozoa
• ubiquitous in oceans
• use cilia for locomotion, and food capture
• eat bact., small phyto-/zoo-plankton

Cnidaria

• holoplankton
• long tentacles with stinging cells (nematocysts) for capture of larger prey

Ctenophores

• holoplankton
• transparent animals
• swim by 8 rows of fused cilia (called comb plates)
• most cms to 2m
• complete digestive system + colloblast cells (adhesive)

Tentacula

• holoplankton: ctenophores
• long paired tentacles with colloblast for prey
• some have large ciliated oral lobes for prey
• have significant impact on fish populations via egg and larvae consumption 

Tentacula

also see other card

Nuda

• holoplankton: ctenophores
• lack tentacles
• large mouth to engulf prey
• eat mostly tentacula and ctenophores

Heteropod

• Holoplankton: mollusca
• closely related to snails, swim with single fin from "creeping foot"
• some can completely withdraw into shell others lack shells and are transparent
• well-developed eyes --> eat planktonic molluscs, copepods, chaetognaths, siphonophores
• large chitinous teeth protrude form mouth
• mostly in warm waters --> not abundant 

Thecosome

• holoplankton: mollusca
• shelled "snails" with paired wings for swimming (derived from foot)
• up to 30mm 
• suspension feeders --> exude a mucous web that captures phytos, small zoo., and detritus
• can be very abundant in epipelagic seas, and polar regions
• impt food source for fisheries
• paleo importance: pteropod ooze

Gymnosomes

• holoplankton: mollusca
• lack shells, but have paired wings
• 85mm long, prey upon specific pteropods
• capture prey with special tentacles and chitinous hooks, then remove soft tissue of pteropods before swallowing 

Ctenophora

• each comb row has many "teeth" and each tooth has many thousand cilia
• combs interact with light, creating prism-like effect
• refraction and diffraction NOT chemically mediated
• many also have true bioluminescence, not in combs 

Arthropods

• holoplankton
• Generally, the arthropods = the most successful animal group on earth - greatest diversity of habitats, eat the most food, have the highest numbers (75% of known animal spp ~1.1m spp.) - Key innovation = exoskeleton (protective, flexible, suit of armor = chitin + protein)

Euphausiids

(keystone of Antarctic ecosystem)

holoplankton

-86 spp, 15-20mm (100mm for E. superba)

-Eat diatoms at upwelling regions, when bloomed Euphausiid mass > human mass (750 million metric tons!)

-Fast swimming, undersampled by nets due to avoidance behavior -So abundant that 100m D.V.M. can actually mix deep-water nutrients into surface waters at the Antarctic Convergence

-Eaten by seabirds, squids, fishes, whales

Copepod

holoplankton

70% of the larger zooplankton -

1850 spp., usually <6mm in size -

Eat phytos, particularly diatoms using currents generated by movement of swimming legs and mouthparts -12 distinct anatomical life history stages

Caldocera: Arthropod

holoplankton

400 freshwater spp (e.g., Daphnia), only 8 marine spp -

coastal / brackish water

-Can rapidly increase #s parthenogenically (no male / no fertilization) when favorable

Amphipods: arthopod

holplankton

laterally compressed bodies

-Small fraction of zooplankton -

Parathemisto is common in polar regions

-Predators / parasites on medusae, ctenophores, salps, other amphipods

-Direct development (young = adults)

Decapod: Arthropod

holoplankton

-most advanced crustacea -

10-100mm, larger zooplankton

-Strong swimmers, live >150m depth,

eat copepods, euphausiids, planktonic crustacea -

Impt as food for albacore tuna, dolphins and whales

Ostracod: arthropod

holoplankton

-minor components of zooplankton -

Hinged bivavle exoskeleton

-<20mm, scavengers?

Mysids: arthropods

holoplankton

not important overall?

-benthic, but rise at night to form breeding swarms

Appendicularia(larvaceans): Chordota

holoplankton

-look like a “tadpole”

-secrete mucous ‘house’

-<5mm body, house 5- 40mm

-tail directs water into house to capture suspended material on a feeding filter

-clogged filter, discard house == “marine snow"