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Number of Results: 119

abiotic

abrasion

absorption

abyss

abyssal plain

abyssobenthic

abyssopelagic

acclimation

acclimatization

accumulation

acid

acid -soil

acid iron waste

acid rain

acid-base balance

acidophilic

activated sludge process

acute

acute toxicity

adaptation

adenosine triphosphate (ATP)

adhesion

adhesive eggs

adipose tissue

adsorption

adult

aeolian depostis

aeration

aerobic

aerobic bacteria

affinity index

age composition

age group (class)

agglutination

aggregation

agonistic behaviour

agricultural waste

air

air saturation value of dissolved oxygen

albinism

aldehydes

alga

algal bloom

algal toxicosis

algicides

alien

alkalinity

alkalinity, total

allele

allelic frequency

allopatric

alluvial deposit

alluvium

alpha-radiation

altruistic behaviour

ambient

amino acid

ammonia

ammonia toxicity

ammonification

amnesic shellfish poisoning (ASP)

amorphous

amphiatlantic

amphibiotic

amphidromous

amplitude

anadromous

anaerobic

anaerobic bacteria

anaerobic digestion

anaerobic respiration

analysis of variance

androgens

annelids

annual production

ANOVA

anoxia

anoxic

anoxic substratum

anoxic zone

antagonism

Antarctic cirumpolar current

Antarctic convergence

Antarctic divergence

anthropogenic

anti-fouling agent

antibiotic

antiboreal

antigenic drift

aphotic

Apogean tides

aquaculture

aquatic organism

aquifer

archibenthal zone

arenaceous

argillaceous

arithmetic mean

artefact

artificial fertilization

artificial reef

ash-free dry weight

assimilation

assimilative capacity

assimilative efficiency

association

astronomic tide

asymmetry

asymptomatic distribution

atmosphere

atmospheric inputs

aufwuchs

austral

autecology

autochthonous

autotroph

average distance

avoidance response

azoic

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euphotic zone

Definition

For the purpose of biological investigations, it is convenient to consider the sea as divided vertically into three zones with respect to the amount of light that is present. These are: (a) the euphotic zone, which is abundantly supplied with light sufficient for the photosynthetic processes of plants (in oceans down to 80 m); (b) the disphotic zone, which is only dimly lighted and extends in the open ocean from about 80 m to 200 or more metres. No effective plant production can take place here; (c) the aphotic zone, the lightless region below the disphotic zone. The depth of the euphotic zone varies with the water's extinction coefficient, the angle of incidence of the sunlight, the length of day and cloudiness.

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