Marine Reproduction, Plankton, and Oceanic Food Webs Overview

Reproductive success

The ability of an organism to pass on its genes to the next generation.

Direct sperm transfer

A method of reproduction where sperm is transferred directly to the female, facing the problem of finding mates.

Free Spawners

Organisms that shed gametes into the water, relying on environmental factors for fertilization.

Fertilization success

The likelihood of successful fertilization, which decreases when the distance between individuals is far.

Epidemic spawning

A phenomenon where the stimulus of one spawner causes other individuals to shed gametes, as seen in mussels.

Mass Spawning

A reproductive strategy where many individuals spawn at the same time, commonly observed in corals.

Timing of spawning

The specific times when organisms release gametes, often during periods of quiet water, as seen in seaweeds.

Interspecific fertilization

Fertilization that occurs between different species.

Microscale fertilization

A type of fertilization that can lead to polyspermy, where multiple sperm fertilize an egg.

Small-scale turbulence

A challenge in reproduction related to the Reynolds number, affecting gamete dispersal.

Parental care

The investment of time and resources by parents to ensure the survival of their offspring, which is absent in most marine species.

Non sexual reproduction

A form of reproduction where descendants are genetically identical to the parent.

Colonial

Organisms that live in colonies, where individuals are genetically identical.

Artificial selection

A process where humans selectively breed organisms, exemplified by overfishing of protandrous shrimp leading to increased male to female sex changes at smaller sizes.

Asexual reproduction

A reproductive strategy where offspring are produced without the fusion of gametes, with mutation being the only source of genetic variation.

Clonal

A form of reproduction where organisms reproduce by binary fission, resulting in genetically identical offspring.

Module

A term referring to individuals in a colony that are all genetically identical, forming modules.

Sexual reproduction

Process to form new colonies/modules, favored when environment is unstable/variable in organisms that can do both.

Migration

Directed movement (as compared to dispersal).

Fully oceanic

Organisms that live entirely in ocean environments.

Diadromous

Organisms that divide life between freshwater and salt water.

Catadromous

Adults that live in freshwater.

Anadromous

Adults that live in the ocean.

Plankton

Organisms too small to swim against the current (Greek: planktos - wanderer, drifter).

Phytoplankton

Plankton that photosynthesize.

Zooplankton

Animal members of the plankton.

Mixoplankton

Planktonic organisms that can be classified as having both animal and plant characteristics.

Holoplankton

Permanent residents of the plankton, including viruses, bacteria, phytoplankton, copepods, jellyfish, etc.

Meroplankton

Temporary residents of the plankton, including the larval stages of most benthic invertebrates and fish.

Neuston

Organisms associated with the surface slick, including bacteria and some insects.

Pleuston

Planktonic organisms that protrude, such as By-the-wind-sailor (Vellella velella) and Portuguese-Man-of-War (Physalia physalis).

Megaplankton

Plankton larger than 20 cm, such as jellyfish.

Macroplankton

Plankton ranging from 2-20 cm, including pteropods and krill.

Mesoplankton

Plankton ranging from 0.2 mm to 2 cm, including copepods and forams.

Microplankton

Plankton ranging from 20-200 µm, including ciliates and coccolithophores.

Nanoplankton

Plankton ranging from 2-20 µm, including diatoms and dinoflagellates.

Picoplankton

Plankton ranging from 0.2-2 µm, including smaller eukaryotic protists and bacteria.

Femptoplankton

Plankton smaller than 0.2 µm, including viruses.

Viral shunt

Short circuits the food web and returns nutrients to the microbial loop.

Cyanobacteria

Invented oxygenic photosynthesis; responsible for oxygenating the earth's atmosphere and made multicellular life possible.

Toxic cyanobacteria

Cause problems in freshwater; Microcystis blooms in lakes produce a potent liver toxin (hepatotoxin).

Diatoms

Abundant phytoplankton in temperate and polar regions, occurring singly or forming chains, and encased in silica shells.

Dinoflagellates

Abundant phytoplankton, many are mixotrophic, some photosynthetic and some heterotrophic.

Coccolithophore

Abundant phytoplankton that secrete calcium carbonate plates (coccoliths) and can form massive blooms in the ocean.

Crustaceans

Largest group of crustaceans in zooplankton, including copepods and euphausiids (krill).

Krill populations

Shrinking ice in the Antarctic has reduced Krill populations by ~80%

Cnidarians

Contains Scyphozoan (true jelly fish), Hydrozoans, and Siphonophores (colonials)

Scyphozoans

True jellyfish that swim rhythmically by contracting their bell

Nematocysts

Organelles contained in cnidocytes that discharge upon contact, impaling prey

Box jellies

Have extremely potent and painful venom that can lead to cardiac arrest within minutes of being stung

Siphonophores

Colonial organisms where individuals specialize in feeding, reproduction, or defense

Physalia physalis

Commonly known as Portuguese Man of War

Physophora

Has tentacles that resemble copepods to lure copepod predators in

Hydrozoans

Usually found in plankton as small medusa resembling true jellyfish

Velella velella

Commonly known as By-the-wind sailor

Ctenophores

Also known as comb jellies, they are microcarnivores that feed on smaller zooplankton

Bioluminescent

Many ctenophores are bioluminescent or iridescent, though poorly understood

Salps

Related to benthic sea squirts, with incurrent and exit siphons on opposite ends of body

Larvaceans

Small organisms that create a mucoidal house around themselves and generate current through it

Mollusca

Includes Pteropods, which are holoplanktonic snails

Cilliates

Includes Foraminifera and Radiolaria

Foraminifera

Secrete skeleton of calcium carbonate, common in plankton, size ~ 1 mm to a few mm

Foram ooze

Deep-sea sediment composed of foraminifera

Radiolaria

Have skeletons of silica, common in plankton, size ~ 50 mm to a few mm

Radiolarian ooze

Deeper than foram ooze, composed of radiolaria

Diel vertical migration

Animals (zooplankton, fishes) rise to the surface of the ocean at night and then sink to depth during daytime

Strong light hypothesis

UV radiation has adverse impact on zooplankton so they retreat during the day.

Phytoplankton recovery hypothesis

Zooplankton feed at night and then allow phytoplankton populations to recover during the day.

Predation hypothesis

Predators use vision to capture prey, so zooplankton leave surface waters during the day to remain hidden.

Energy conservation hypothesis

Energetically advantageous to spend the day in colder, deeper waters (poikilotherms!).

Surface mixing hypothesis

Zooplankton move downward in the day in the hope that when they return at night, surface currents will have carried new water to the area with new food sources.

Nekton

Organisms that are large/strong enough to swim against ocean currents.

Reynold's numbers

A dimensionless number used to predict flow patterns in different fluid flow situations.

Cephalopods

Phylum Mollusca that includes organisms like chambered nautilus, cuttlefish, squid, and octopus.

Chambered nautilus

Considered a living fossil - has changed very little in the last 300 million years.

Cuttlefish

Contains a unique, internal bone called a cuttlebone which can be gas filled for use in buoyancy.

Squid

Strong swimmers (jet propulsion), well-developed nervous system.

Octopus

Lack any sort of shell/skeleton - may contain small vestigial shell.

Chondrichthyes

Cartilaginous fishes, including sharks, skates, rays - cartilaginous skeleton, replaceable tooth rows.

Osteichthyes

Bony fishes, true bony skeleton - much more diverse than Chondrichthyes, teeth fixed in jaws.

Cruising predators

Long and torpedo-shaped fishes such as tuna, marlin, sailfish, with fins spaced for maneuverability.

Schooling

Behaviorally based aggregation of fish.

Viviparous

Birth to live organisms.

Oviparous

Lay eggs.

Bullhead Sharks

Small order consisting of about 9 species with a unique head shape.

Mackerel Sharks

Includes familiar species like Great White and Whale Shark.

Shark senses

Include smell, eyesight, electricity detection, water pressure sensing, and hearing.

Cetaceans

Whales, porpoises, dolphins: all homeothermic with strong parental care.

Odontoceti

Toothed whales that are usually good hunters.

Mysticeti

Baleen whales that have baleen plates for straining zooplankton.

Pinnipeds

Include seals, sea lions, and walruses; rear legs modified as flippers.

Sea turtles

Nest on sandy beaches and migrate to feeding grounds; some use earth magnetic field for navigation.

Sea snakes

Approximately 62 species, fully aquatic and incapable of moving on land.

Spring Phytoplankton Bloom

Occurs when light decreases with decreasing depth in the water.

Compensation depth

The depth at which oxygen produced from photosynthesis is equal to oxygen consumed by respiration.

Compensation light intensity

The light intensity corresponding to the compensation depth.

Mixing depth

The depth at which all water above is thoroughly mixed, and is far deeper in the winter.

Critical depth

Depth above which total oxygen produced in the water column equals total consumed.

BLOOM

Occurs if Mixing Depth is shallower than Critical Depth.

NO BLOOM

Occurs if Mixing Depth is deeper than Critical Depth.