Marine Food Webs, Trophic Levels, and Ecological Concepts in Marine Biology

Food chain

a strand within a food web: the _____ is a series of who-eats-who connections, extending from the lowest trophic level (primary producers).

Food web

a kind of directed graph in which species are the nodes, and consumption links are the edges.

Trophic level

the relative position of a node in a food web; the lowest (1) is...

Primary producer a.k.a. autotroph

organisms that 'self-feed' (autotrophic) by converting mineral nutrients and an energy source to biomass are at the base of any food chain.

Photoautotrophs

primary producers whose energy source is the light from the sun.

Chemosynthesis

a process in which a chemical energy source, such as hydrogen sulfide leaking from vents, powers primary production.

Chemoautotrophs

organisms that perform chemosynthesis.

Primary consumer

organisms that directly consume the primary producers (that's trophic level 2).

Herbivores

organisms that primarily consume plants.

Trophic level 2

the level occupied by primary consumers.

Iron limitation

a concept discussed in relation to the skepticism about dumping iron in the sea.

Ecologists

scientists who study the relationships between organisms and their environment.

Sea otters

a species studied for their role in structuring nearshore communities.

Food web complexity

the concept that relates to the diversity of species within a food web.

Riparian plant diversity

the variety of plant species found along riverbanks, influenced by salmon.

Empirical article

a research paper based on observed and measured phenomena.

Directed graph

a representation of a food web where species are nodes and consumption links are edges.

Biomass

the total mass of organisms in a given area or volume.

Latin and Greek roots

the origins of many scientific terms that can aid in understanding biological vocabulary.

Maxillipeds

a term used in crustacean morphology to describe certain appendages.

Marine biology

the study of organisms in the ocean and other saltwater environments.

Trophic dynamics

the study of the flow of energy and nutrients through food webs.

Consumption links

the connections in a food web that indicate which species eat which.

Nodes

the species represented in a food web.

Troph

Means 'grow' or 'feed'.

Photoautotroph

An organism that feeds itself on light.

Chemolithotroph

Refers to organisms that grow on inorganic chemical energy sources.

Carnivore

Animal that eats other animals.

Apex predator

Organisms at the top of a food chain, with no natural predators.

Predation

Getting food by killing prey.

Parasitism

When you don't kill the thing you're eating.

Grazing

Killing the prey when the prey happens to be a plant.

Omnivore

An animal that eats both plants and animals.

Heterotroph

Organisms that feed on others.

Mixotroph

Organisms that blend autotrophy and heterotrophy.

Facultative heterotroph

An organism that can eat bacteria to sustain itself when light is unavailable.

Decomposers

Organisms that regenerate resources needed by primary producers.

Detritivore

Organisms that eat detritus, meaning dead bits of biomass.

Microbial loop

The subset of marine food webs dominated by prokaryotic microbes and their viruses.

Eutrophic

Characterized by good nutrient enrichment.

Oligotrophic

Characterized by few nutrients.

Species

The fundamental unit of biodiversity, defined as a set of potentially interbreeding natural populations that are reproductively isolated from other such groups.

Niche

An ecological role that may be filled by a particular species, or the set of requirements for an organism to thrive within an ecosystem.

Guild

A collection of species that exploit similar resources or make their living in similar ways.

Taxocene

A group of related species within a community.

Trophic species

The set of species that share common prey and probably common predators.

Keystone predator

A predator whose effect on the structure of an ecological community is significantly greater than its numbers within the community.

Keystone species

A species that has a disproportionately large effect on its environment relative to its abundance.

Ecosystem engineer

An organism that significantly modifies its habitat, impacting species richness in a community.

Foundation species

Organisms that are numerically dominant within a community and provide physical habitat.

Piscivores

Organisms that eat fish.

Common prey

Prey shared by a group of trophic species.

Common predators

Predators that are shared among a group of trophic species.

Top-down effects

Influences on community composition and diversity originating from higher trophic levels.

Non-predatory interactions

Interactions that affect community structure without direct predation.

Habitat

The natural environment where an organism lives.

Species richness

The number of different species represented in a given ecological community.

Ecological community

A group of interacting species living in the same area.

Pelagic

Living in the waters of the open ocean, as opposed to nearshore or estuarine waters.

Epipelagic

Near-surface waters, synonymous with the photic zone where light is sufficient for photosynthesis.

Mesopelagic

Middle depth - the twilight zone, where there is light but not enough to support photosynthesis.

Bathypelagic

Deep waters.

Holopelagic

Pelagic for the whole life cycle; holo- is Greek 'whole'.

Benthic or benthos

Literally, 'the depths', but is used to refer to the seafloor and the flora and fauna living thereon/in.

Littoral

The waters of the shore; more or less synonymous with the intertidal zone.

Supralittoral

Above the intertidal.

Neritic

The shallow near-shore portion of the ocean, i.e. above the continental shelf.

Estuary or estuarine

Where rivers meet the sea, and fresh and seawaters mix along a gradient.

Nekton

The set of all organisms that live in the water column but can out-swim the currents.

Sedentary

Organisms that stay in one place; sessile is a synonym.

Errant

Organisms that move around.

Trophic cascade

An ecosystem event in which the effects of perturbation at one trophic level cascades beyond adjacent trophic levels.

Facilitation

Refers to cases in which the effect of one species upon another makes the habitat more favorable for a third (or more).

Phase shifts

Perturbations may result in changes to equilibrium population levels, leading to alternative stable states.

Competitive exclusion

Two or more species with identical resource requirements will eventually compete as resources are exhausted.

Resource partitioning

Specialization on subsets of a resource pool to greater or lesser extent.

Intermediate disturbance

An occasional or periodic reset to community composition.