Abdomen: The posterior of the three main body divisions.
Abdominal: Pertaining to the abdomen.
Abiotic: The physical and chemical non-living factors in an environment.
Absorption: The process by which chemicals in gaseous, liquid or solid phases are incorporated into and included within another gas, liquid, or solid chemical. For example, filter media (e.g., sponges) trap unwanted molecules by absorption.
Abyssal Plain: The deep ocean floor, an expanse of low relief at depths of 4,000 to 6,000 m.
Abyssopelagic Zone: The 4,000 to 6000-m-depth zone, seaward of the shelf-slope break.
Acceptable Daily Intake (ADI): The chemical ingestion level determined by combining the maximum No-Observed-Adverse-Effect-Level (NOAEL) with the addition of an uncertainty (safety) factor. Chemicals with ADI levels usually are not considered or suspected to be carcinogens. This classification results from toxicity data collected during prolonged ingestion studies conducted on a number of animals.
Acclimation: Given a change of a single parameter, a readjustment of the physiology of an organism, reaching a new steady state.
Acidic: A water condition which has a pH lower than 7.0. A trend towards acidic water may be a sign of overfeeding.
Acidity: The base neutralizing capacity of a water is known as acidity. Acids contribute to corrosiveness, influence chemical reactions, and chemical/biological processes. Acidity is determined using a titrametric or potentiometric method.
Acre-Foot: The volume of water (325,851 gallons of water) required to cover one acre of land with 12 inches of water.
Acrylic: A plastic material used to construct fish tanks, filters and accessories. Also known as Plexiglas.
Actinic: A type of fluorescent lighting that provides the proper spectra for photosynthesis and is the color of the sea below 10 meters. Best used for aquariums with live plants or chlorophyll containing species such as reef coral. Actinics are very blue.
Activated Carbon: A commonly used chemical filter media, which looks like crumbled charcoal. It can absorb many compounds and chemicals out of the water, such as unused ozone from the air and chlorine from the water and is especially good at removing yellowing compounds to keep the water clear. Carbon must be changed regularly, or it may leach impurities back into the water.
Adductor Muscle: Muscles in bivalves used to close the shell.
Adipose Fin: A small fleshy fin located behind the dorsal fin and in front of the caudal fin. It is usually only found on characins. It seems to serve no purpose.
Adsorption: The process by which filter media attracts unwanted molecules to its surface via a chemical charge. Odors from freezers and refrigerators are adsorbed to baking soda.
Advection: The process by which chemicals and heat are transported along with the bulk motion of flowing gas or liquid. For example, nitrates move through soils and aquifer formations due predominantly to the bulk motion or movement of water.
Adventitious Root: A root that develops from the node of a stem or similar organ, such as a rhizome, stolon or runner.
Aerobic: A term used to describe an organism that needs oxygen to survive.
Africans: Refers to freshwater cichlids from Africa. These fish come from the very hard, slightly salty water of the rift lakes.
Age structure: The relative abundance of different age classes in a population.
Aggregated Spatial Distribution: A case where individuals in a space occur in clusters too dense to be explained by chance.
Ahermatypic: Non-reef-building (referring to scleractinian corals).
Air Pump: A pump used to deliver air to the aquarium, usually for lift tubes, skimmers, and bubblers. The pump pushes air through silicon tubing and to air stones or other aquatic decor. They are also an essential for UGF's (undergravel filters). An airstone is placed in each clear tube. When the air bubbles travel upward, they generate steady current which brings water from the bottom, through the tubes and to the surface. The most common type of air pump is a diaphragm pump, though cylinder pumps are available for large installations.
Airstone: A device that attaches to the air pump to create various bubble effects.
Alevin: Newly hatched fish; the yolk sacs are still attached. This stage is prior to the fry stage of development.
Algae: Plant-like organisms, which grow in water without true roots, stems, or leaves. They also lack flowers or seeds. Algae are classified as plants, although they share many characteristics with monerans (fungus). It may become slimy over time and will grow in fresh or marine water. Algae will give water a greenish color. Seaweed is a well-known example of algae.
Algal Bloom: Rapid growth by algae producing large quantities of plant material which can result in low dissolved oxygen conditions as the algae dies and decays. Low dissolved oxygen can result in the death of fish and other aquatic organisms.
Alimentary Canal: The tube of the digestive system through which food passes, where digestion takes place.
Alkaline: Water with a pH between 7 and 14. Also known as Basic.
Alkalinity: This is the measure of a solution's resistance to changes in pH. It is commonly measured as carbonate alkalinity or total alkalinity, and is expressed in meq, dKH, or ppm of C03 ions. The alkalinity can be raised by adding a buffer.
Allele: One of several variants that can occupy a locus on a chromosome.
Allopatric Speciation: The differentiation of geographically isolated populations into distinct species.
Allozyme: A variant of an enzyme type. These may be variants of a specific enzyme (e.g., cytochrome c) that are the products of a single genetic locus.
Aluminum (Al): There is no published Maximum Contaminant Level (MCL), but 0.2 mg/L is considered safe. Elevated aluminum is believed to be associated with forms of dementia, such as: Alzheimer’s.
Amensal: Negatively affecting one or several species.
Amino Acids: Basic structural unit of proteins.
Ammonia (NH3): A dissolved gas that even in low concentrations is toxic to fish. It is produced by the breakdown of organic waste products.
Ammonia (NH4): There is no MCL established for ammonia. Ammonia is very toxic to fish and aquatic life. Ammonia concentrations of 0.06 mg/L can cause gill damage in fish and 0.2 mg/L is lethal to trout. Concentrations in excess of 0.1 mg/L suggest domestic or agricultural sources of waste.
Ammonia Tower: A biological filtration system which consists of a plastic chamber with a biological filtration media. Water runs through the media, which mixes with the air, and reacts with the bacteria which serve to remove ammonia and nitrites. It is this wet / dry exchange that promotes bacterial growth. Most commonly referred to as a wet/dry filter.
Ammonia: This is the first step in the nitrogen cycle. Ammonia is generated by fish urine and by the decay of dead fish and plant material. It is perhaps the deadliest agent to tropical fish. Care must be made to ensure that the ammonia levels stay at zero.
Amorphous: Not having any definite form.
Amyloodinium: Amyloodinium ocellateum is commonly called Oodinium, Marine Velvet, or Saltwater Ick. Possible signs of the disease are cloudy eyes, gasping for breath, listlessness, and white spots. Positive signs of the disease are gold or brown spots, rough skin, and rubbing against rocks, etc. Treatment can be done by a freshwater dip and the use of copper (as long as inverts are not in the tank).
Anadromous Fish: Fish that spends most of its life feeding in the open ocean but that migrates to spawn in fresh water (e.g., Salmon).
Anaerobic: A term used to describe an organism that lives in an environment with little or no oxygen, and means, literally, without air. It also refers to an area where there is no dissolved oxygen in the water. While necessary for some things such as bacterial reduction of nitrate to nitrogen, these areas can also produce hydrogen sulfide and other undesirable substances. Most of the harmful bacteria are anaerobic.
Anal Fin: Single fin mounted vertically below the fish, just in front of the caudal fin.
Anal: Pertaining to the hind or most posterior part of the body.
Anion Exchange: The chemical process where negative ions of one chemical are preferentially replaced by negative ions of another chemical. In water treatment, the net effect is the removal of an unwanted ion from a water supply. For example, some municipalities are installing anion exchange systems to remove nitrate from their water supplies.
Anion: A negatively charged chemical. Nitrate and chloride (Cl-) are examples of anions.
Annelids: A phylum that includes segmented terrestrial and aquatic worms.
Anoxic: Deficient or lacking oxygen.
Antenna (pl. antennae): A pair of segmented appendages located on the head above the mouthparts and usually sensory in function.
Anterior: At or directed toward the head or forward part of the body.
Anthostele: The lower part of the polyp, often stiffened, into which the distal portion of the polyp, the anthocodia (which includes the mouth and the eight tenacles) is withdrawn.
Antibiotic Resistance: Frequent exposure to an antibiotic provides conditions favorable to the evolution of germs, which are resistant to (i.e. not harmed by) that antibiotic.
Antimony (Sb): The maximum contaminant level is 0.006 mg/L. Elevated levels of antimony can increase blood cholesterol and decrease blood glucose.
Aperture: An opening or hole in the gastropod shell.
Apex: The tip or highest point of the shell.
Aphotic Zone: That part of the ocean in which light is insufficient to carry on photosynthesis.
Apical Bud: The principal growing point of the stem.
Aquaculture: Cultivation of aquatic organisms under controlled conditions.
Aquatic: Living in water.
Aquifer: The saturated underground formation that will yield usable amounts of water to a well or spring. The formation could be sand, gravel, limestone or sandstone. The water in an aquifer is called groundwater. A saturated formation that will not yield water in usable quantities is called an aquiclude. Most Pennsylvania aquifers may be categorized into confined and unconfined aquifers.
Aragonite: The substance that makes up coral skeletons and coral sand, as well as some shells. It's a form of CaCO3.
Arrow Worms: Members of the phylum Chaetognatha, a group of planktonic carnivores.
Arsenic (As): The MCL for arsenic is 0.05 mg/L. Arsenic is highly toxic and its prevalence is due to the natural occurrence of this metal and past use of arsenic in pesticides. Arsenic poisoning typically makes people feel tired and depressed and this poisoning is also associated with weight loss, nausea, hair loss, and marked by white lines across your toenails and fingernails. For freshwater the concentration should be less than 0.05 mg/L.
Artemia: A very common food for fresh and marine water fish. They are very tiny crustaceans that are easy to breed and maintain for long periods of time. They are a great source of food for young fry. They grow to about 3/4 inches max. See brine shrimp.
Artificial Recharge: The unnatural addition of surface waters to groundwater. Recharge could result from reservoirs, storage basins, leaky canals, direct injection of water into an aquifer, or by spreading water over a large land surface.
Asexual Reproduction: A natural process by which some plants and animals produce offspring within themselves, without the production of eggs or without fertilization from another plant or animal.
Assimilation Efficiency: The fraction of ingested food that is absorbed and used in metabolism.
Assortative Mating: The mating of a given genotype mates with another genotype at a frequency disproportionate to that expected from random encounter.
Atoll: A horseshoe or circular array of islands, capping a coral reef system perched around an oceanic volcanic seamount and enclosing or nearly enclosing a lagoon.
Attenuation of Light: Diminution of light intensity or a decrease in the energy of a wave or beam of particles occurring as the distance from the source increases; caused by absorption, scattering, and divergence from a point source; explained, in the ocean, in terms of absorption and scattering.
Aufwuchs: A term that refers to algae growing on rocks, wood or other surfaces.
Autotrophic: Pertaining to organisms able to manufacture their own food from inorganic substances.
Autotrophic Algae: Algae capable of photosynthesis and growth, requiring only a few organically derived substances, such as vitamins, along with dissolved inorganic nutrients.
Auxotrophic Algae: Algae requiring a few organically derived substances, such as vitamins, along with dissolved inorganic nutrients for photosynthesis
Average Trophic Transfer Efficiency: Amount of food eaten, which is converted to animal tissue. Typically, an animal requires 10 pounds of food to produce 1 pound of animal tissue, hence a trophic efficiency of 10%.
Axillary Bud: A bud, capable of developing into a lateral shoot, present in the angle between the stem and a leaf.