Abiotic:
non-biological

Accompanying species:
species present in a given biotope, but not exclusively.

Acid:
compound that tends to transfer hydrogen ions to another compound called a base. An acid is said to be strong if it dissociates (i.e., ionises, releasing hydrogen ions) to a high degree, and weak if it dissociates to a small degree. Acids turn litmus paper red (pH lower than 7). In geology, acid refers to magma and rocks that contain more than 65% silicates.

Adsorption:
process by which a fluid is fixed to the surface layer of a solid or liquid with which it is in contact. Unlike absorption, it affects only the interface between the two phases.

Aerobic:
of an organism that is able to survive (or of a metabolic process that can take place) only in the presence of oxygen.

Albedo:
a measure of the reflectivity of a surface or of an object, resulting from ratio of reflected to incident electromagnetic radiation. An albedo of 1 indicates a perfectly reflecting object, while an albedo of 0 indicates a totally dark object.

Algae:
uni- or multicellular aquatic plants; multicellular algae have no recognisable roots, stem or leaves. The term macroalgae refers to macroscopic algae, i.e., those that are visible to the naked eye. The term microalgae refers to algae that are not visible to the naked eye. Blue algae, also known as Cyanobacteria, are a group of autotrophic photosynthetic bacteria. Cf. Plate 6.

Allochthonous:
species which is not native to a given territory, into which it has been introduced intentionally or unintentionally. Allochthonous species may be invasive and enter into competition with autochthonous species (native to the location and spontaneous). Cf. Plate 100.

Alluvial cone:
cone-shape accumulation of detritus deposited by a river.

Alluvial plain:
plain formed over geological timescales by the transport and deposition of detritus by rivers.

Amphipods:
small crustaceans, e.g., sand fleas.

Anaerobic:
of an organism that is able to survive (or of a metabolic process that can take place) in the absence of oxygen.

Anion:
ion having a negative charge.

Annelida/annelids:
(phylum) worms whose bodies are divided into segments (e.g., Hediste diversicolor, Plate 39).

Anomaly:
in climatology, of an event which represents a deviation from the normal pattern. In operational terms, it is the difference between a value at a precise moment and the average value, usually calculated over a period of years. A thermal anomaly is an anomaly in the temperature.

Anoxia:
absence of oxygen. May refer to a given environment or biological tissues.

Anoxic:
of conditions, in a state of anoxia.

Anseriformes:
order of aquatic birds, generally with flat beaks and webbed feet, to which belong swans, geese and ducks. Cf. Plate 46.

Anthropic:
of human beings and human activities.

Ardeidae, ardeids:
family of aquatic birds with strong beaks and generally long feet, to which belong herons and bitterns. Cf. Plate 47.

Arenile:
distesa di sabbia sulla riva del mare, dei fiumi, dei laghi.

Artesian well:
well that draws water from confined (pressurised) groundwaters.

Atmosphere:
Gaseous fluid which, subject to the Earth’s gravitational pull, envelops it and follows its rotational and orbital movements and is thus also subject to centrifugal forces.

Atmospheric pressure:
the ratio of the weight of the air column above a given surface to the area of that surface.

Autochthonous:
1: of spontaneous species, native to a given territory; 2: of rocks, formed in the place where they are found, without having undergone tectonic shifts.

Autotrophic:
of an organism, able to create organic matter from inorganic matter. Autotrophic organisms my be photosynthetic (plants) or chemosynthetic (some bacteria) depending on whether they use solar energy or chemical energy.

Bacàn/Bacàni:
Venetian dialect word indicating sandy formations (sandbars) which originally existed near the bocche di porto. Only one exists today, the Bacàn di Sant’Erasmo.

Bathymetry:
the branch of oceanography which deals with the depth, the graphical representation and the morphology of the bottom of lakes and the sea.

Benthos:
the complex of aquatic organisms that live on the surface of the sea bed or lake bed or just below it. The benthos may prefer hard substrates, such as the banks of canals and bricole, or mobile (soft) substrates, such as the lagoon bed. Depending on its dimensions it may be divided into micro-, meio- and macrobenthos. Cf. Plate 37.

Bilge:
the part of the underwater body of a ship between the flat of the bottom and the vertical topsides

Bioaccumulation:
the process by which a living organism concentrates (accumulates) contaminants, both directly from the environmental medium and indirectly via its food. biomagnification is a special case of bioaccumulation, in which the organism (generally a predator) absorbs the pollutant mainly via its food (its prey). Cf. Plate 99.

Bioavailability:
the tendency of a substance to be in a chemical or chemico-physical state that can be absorbed and/or metabolised by one or more living organisms. The greater the bioavailability of a pollutant, the more it can be absorbed by organisms.

Biocoenosis:
the sum of all the organisms which live in the same environmental unit (biotope), closely linked by complex biological and ecological relations (competition, predation, food web etc.). The composition of biocoenoses is determined by the relationships between organisms and between these and the physical environment. When referring to the plant community, i.e., all the vegetal species that grow in a given area, the term phytocoenosis is used, and the animal community is referred to as the zoocoenosis.

Biodisturbance:
action performed by organisms that move or remove the sediments from the lagoon bed, sometimes leaving characteristic traces (footprints, tracks, tunnels).

Biodiversity:
variety of living forms present in a territory. Biodiversity can be studied on the level of genes, species, biocoenosis and landscape. The number of species is referred to as “species richness”, and constitutes one of the potential measures of the biodiversity of an area; it can also be used as a basis of comparison with other areas. Species richness is considered the simplest general measure of biodiversity, and the easiest to evaluate, although it is only an approximate and incomplete estimate of the variability of the organisms.

Biogeochemical cycle:
circulation of chemical elements and substances between the biota and the abiotic environment. For example, water (the water cycle) evaporates, falls as precipitation, is drunk, is metabolised, is excreted and returns to the start of the cycle.

Bioindicator:
a bioindicator is an easily identifiable and measurable aspect of a biological process which provides information about that process without necessarily going into a detailed analysis. A bioindicator may be the structure of the community, the demographics of the population, the physiological and behavioural characteristics of a single organism, the morphology and physiology of cells etc. In normal usage, an organism is considered to be a bioindicator if its “state of health” or its presence/absence indicates a given situation in the environment.

Biomass:
weight of the organisms present in a given moment, in a given place. It is expressed as either wet weight or dry weight.

Biome:
complex of ecosystems in a broad geographical area of the planet, generally defined on the basis of the dominant type of vegetation. The conformation of terrestrial biomes depends on the geography and the climate of the different regions, particularly the latitude, altitude, seasons, precipitation and temperature. Moving from the poles to the equator, there are as many biomes as there are climatic bands: from the tundra of the highest latitudes, characterised by the low vegetation of moss and lichens, through the taiga, made up of vast forests of conifers and then the area of the deciduous temperate forests, dominated by broadleaf trees such as oaks and beeches, followed by the prairies, deserts and, lastly, the tropical rain forest. Each biome also includes continental fresh waters (rivers, lakes, pools, marshes) within its territory and the biocoenoses that populate them. Marine environments are considered by some ecologists to count as biomes.

Biosphere:
the marine-terrestrial portion of the planet populated by living things, which also includes the lower atmosphere.

Biota:
the sum of all living things present in a given territory.

Biotic:
referring to life or living things.

Biotope:
geographical region (of variable surface area and volume) subject to conditions in which the dominant environmental features are homogeneous. The biological component of the biotope is called the biocoenosis.

Bloom:
in ecology, a sudden growth in the quantity of algae in the water.

Bocche di porto:
the inlets connecting the waters of the Lagoon of Venice with those of the Adriatic sea.

BOD (Biochemical Oxygen Demand):
measure of water quality; more precisely, the quantity of oxygen consumed by micro-organisms during the aerobic biodegradation of the organic matter present in the water. The BOD value measured over a period of five days is called BOD5 and is expressed in milligrams of oxygen per litre (mg/L of O₂). BOD analysis thus indicates the concentration of biodegradable organic matter present in a sample of water, and is typically used in the assessment of discharges. The higher the BOD value of the waters, the greater the content in biodegradable organic matter, implying possible negative effects on the environment.

Brackish:
water whose salinity is different from that of the sea, generally lower.

Bricola, briccola:
Venetian dialect word indicating the wooden posts sunk into the bed of the Lagoon and used to mark the edges of the navigable channels and sometimes as moorings for large ships.