Marine Biology - Unit 2

pelagic

open water column where organisms swim or float

benthic

seafloor and sediments

benthic zones

intertidal, subtidal, bathyal, abyssal, hadal

intertidal

part of littoral; most stressful region of ocean; massive swings in temperature, salinity, desiccation, and wave action

subtidal

permanently submerged; well lit; structurally complex habitats

bathyal

continental slope, seamounts, submarine canyons, and cold-water coral mounds; topographically complex

abyssal

cold, flat, dark, food-poor; covers ~1/2 of the ocean floor; largest single habitat on the planet

hadal

trenches; highly isolated; island-like behavior

pelagic zones (horizontal)

neretic, oceanic

pelagic zones (vertical)

epipelagic, mesopelagic, bathypelagic, abyssalpelagic, hadalpelagic

neretic

water over the continental shelf on the shelf break; well-lit; sometimes nutrient-rich; disproportionately productive

oceanic

water beyond the continental shelf; vast; deep; nutrient depleted at the surface

epipelagic

net photosynthesis is possible; nearly all photosynthesis occurs here; nutrient-poor; 0-200m

mesopelagic

aka twilight or dysphotic zone;

bathypelagic

aka midnight or aphotic zone; no light; temp between 2-4°C; immense presure; energy economy is key; only light is biological; 1000-4000m

abyssalpelagic and hadalpelagic

cold, dark, and poorly sampled; 4000m+ (hadalpelagic is defined by trenches)

biomass

aka standing crop; mass of organisms in a defined area or volume

productivity

amount of living material or carbon produced per unit area over time

terrestrial tropic stucture

producers are large, long-lived, and structurally dominant; trophic pyramid correlates with biomass

marine trophic structure

producers are small, short-lives, single-celled phytoplankton; tropic pyramid is inverted at the base; primary consumers can outweigh phytoplankton

primary productivity requirements

light and nutrients

marine system light and nutrients

often physically separated; majorly impacted by climate and circulation

terrestrial habitat structure

comes from plants; animals live in the structure; sessile heterotrophy is not successful

marine habitat structure

comes from plants and animals and just water column; sessile heterotrophy is highly successful

population

group of individuals that are affected by the same overall environment and are relatively unconnected with other populations of the same species

terrestrial population

mot offspring of a population are of that population

marine population

populations are much more open; biphasic life cycle is common; local abundance is set by recruitment

gene flow

any movement of individuals and/or the genetic material they carry from one population to another

allopatric speciation

speciation due to physical or geographic barrier

sympatric speciation

speciation in the same habitat or geography region

terrestrial population barriers

obvious and relatively common

marine population barriers

often invisible and move; experience less allopatric fragmentation

terrestrial phylogenetics

more diverse in terms of species count

marine phylogenetics

relatively species poor; body plan diversity is enormous; life likely originated in the sea

terrestrial physiological contraints

behavioral acclimation; 21% oxygen in the atmosphere constantly (not limiting); desiccation is a major consideration (cuticles, amniotic eggs, excretion, fertilization)

marine physiological constraints

thermal stability with more difficulty for behavioral acclimation; range of DO content; desiccation is not a threat;

acclimation

short term, reversible physical or physiological modification, typically in response to an environmental stressor or change in an individual

adaptation

genetic process by which a population changes to accommodate environmental factors

endotherms

heat is generated internally via metabolism; energetically expensive but physiology proceeds in a stable and high rate

ectotherms

heat comes from the environment; energetically efficient, but physiology depends more on environment

homeotherms

body temperature stays constant

poikilotherms

body temperature may be variable

thermal refugia

places to escape heat

osmosis

spontaneous movement of water from area of low to high solute concentration

osmolality of seawater

1000 mOsm/kg

osmoconform

essentially all marine invertebrates; internal and external salt concentrations match; metabolically cheap; contrained by environmental salinity

osmoregulate

marine vertebrates; elasmobranchs conform and regulate; internal and external salt concentrations differ; environment does not dictate internal salt concentration; metabolically expensive

euryhaline

species that are adapted to a wide range of salinities

reynolds number

( velocity)(body size)(density)/(dynamic viscosity)

gonochoristic

separate sexes across individuals

hermaphroditic

can produce gametes of both sexes over a lifetime; may be simultaneous or sequential

percent of hermaphoriditic marine animals

25-30

plankton

drift with currents

nekton

swim against currents/set own position

benthos

live on seafloor or surface of some kind

migration

allows for exploitation of patchy or ephemeral resources; migration between feeding, breeding, and nursery grounds

migration advantages

maximizing reproductive success; resource division/competition

migration disadvantages

energetically expensive; more vulnerabilities across life cycle

direct release

brooded or small adults are released directly next to adult

broadcast spawning

release gametes into water column for fertilization (greater dispersal)

direct developers

young resemble adults

indirect developers

juvenile/larval phase is distinct

lecithotropic

non-feeding larvae; nutrition is provided by the mother

planktotrophic

larvae feed in the water collumn

facultative planktotrophic

larvae can feed but do not need to for settlement

biphasic life cycle advantages

dispersal; ontogenic niche separation; adaptive decoupling; habitat selection; bet hedging; local density escape

ontogenic

developmental

adaptive decoupling

adult and larval traits can evolve quasi-independently

habitat selection

settlement decisions are determined by physical chemical, or biological cues

pelagic larval duration

time between release and settlement

settlement

behavioral and physical transition from pelagic larva to benthic adult

recruitment

settlement - early post settlement mortality

connectivity

exchange of individuals among populations

demographic connectivity

enough exchange to affect growth, persistence, and recovery (many individuals)

genetic conectivity

enough exchange to prevent genetic divergence (fewer individuals)

thorson's rule

lecithotrophy is more common towards the poles

why do phytoplankton dominate

optimize surface area/volume; small particles sink slower; diffusion and nutrient uptake enhanced; rapid turnover

major nutrients of the sea

nitrogen, phosphorous, and silicon

phosphorous sources

mostly rock weathering; run-off; groundwater flow

nitrogen sources

nitrogen-fixing cyanobacteria; run-off

diazotrophs

organisms capable of nitrogen fixation

Beer's law

light intensity decays exponentially with depth

amount of light absorbed within the first meeter

65%

amount of light that reaches 100 m

1%

primary production

grams of carbon per square meter per year

gross primary production

total rate of energy capture and storage

net primary production

accounts for losses doe to respiration

DIC

dissolved inorganic carbon; bicarbonate and dissolved CO2; largest carbon reservoir of the three

DOC

dissolved organic carbon; sugars, amino acids, small organic molecule mixies

POC

particulate organic carbon; living cells, dead organisms, marine snow sinks

regenerative production

fueled by nitrogen and recycled within the euphotic zone; urea, ammonium, and nitrate; 80% of primary production

new production

fueled by nitrogen that enters the euphotic zone from outside; nitrate; 20% of primary production

biological pump

transport of organic carbon and nutrients from the surface ocean to the deep ocean which are then upwelled to the surface

food chain

simplified but useful model of feeding interactions and trophic levels

food web

closer representation of feeding interactions and trophic levels

trophic level

species of group of species that all feed on one or more other species

amount of energy lost to metabolism between levels

90%

reasons for trophic level inefficiency

not eaten and inefficient conversion

ingested

egestion + respiration + growth

food chain efficiency

aka eff; energy extracted from a trophic level divided by energy supplied to that trophic level