Geobiology

Ecological Succession and Benthic Associations

LMud loving: pelofile. ove and require mix sediment, no pure mud: mistofile. Sand loving: psammofile.Gravel loving. Psefofile.How the benthos modifies its own substrate, any ecological succession can go on because there areopportunistic species, then other species come, until reaching the mature stage of an ecosystem.From unconsolidated sediment, the red algae can growth throw the nodules creating a bioconstruction and thena coralligenous.Even a biotic factor can change and create an ecosystem eg symbiosis between corals and zooxanthellae,dinoflagellates from genus sympodium. Hydrodynamics influences the distribution of the benthic associationsin the infralittoral zone.Coral reefs need oligotrophic water, cause they are strong competitor with algae, withmore nutrients algae win. Reef environment is a shortcut, oligotrophic. Without symbiosis there is no reef.Bleaching is when zooxanthella leaves the corals cause of the high temperature.Duration of larval life can change the

important factor in limiting the distribution of organisms. Some diseases can be specific to certain species or environments, causing a decline in population numbers or even extinction. Additionally, environmental factors such as temperature, salinity, and nutrient availability can also play a role in determining the distribution of organisms. In conclusion, the distribution of organisms is influenced by various factors including larval feeding strategies, barriers to movement, species interactions, and environmental conditions. Understanding these factors is crucial for studying and conserving biodiversity.

important problem, leading the disruption of an environment. Bacteria and viruses are responsible to this diseases.

Trophic resources are biotic factors, the availability is controlled by their transport. Internal waves are in the water mass waves even if there aren't external waves. They are induced by interactions of movement of water mass and seafloor topography. Warm water above cold water led to density boundaries, a lot of materials stay there, below the water is too dense so don't go down. The water mass can be brought toward topographic high where cold water corals can settle.

Commensalism and parasite difference? Parasite is using your body and eating it, the commensalism is eating with the other organism.

Benthic zonation and benthic marine bionomy: The discipline that investigates the identification of the different benthic environment with biological criteria. A descriptive science: environmental gradients. The environmental factors (biotic and abiotic) are considered to

interact and affect the biological associations. Several models: community, biocenosis (= bio unseamble), penetration of light and hydrodynamics. Different models using different way to describe the seafloor. Biocenosis is a self-sufficient community of naturally occurring organisms permanently occupying and interacting among themselves within a specific biotope, in which the dominant conditions are homogeneous. The number of species and individuals are controlled by the mean environmental conditions. The typical criteria are the fidelity: in a hb (Posidonia) biocenosis study the association of mollusk there is a group that is always there. Biocenosis is a statistical concept describing an association that is typically there. Communities are recognized by pilot-species, the most abundant and dominant, with a rather homogeneous distribution in the investigated area. The sample of seafloor contain different abundance of organisms, so opportunistic species are important, don't care about.

fidelity but abundance.abundance is the criterion. Also,How hydrodynamics influences the distribution of thebenthic associations in the infralittoral zone:HP (Posidonia meadows) is in the middle. Hydrodynamic isan important edaphic factor. Low concentration of organicmatter where the hydro is high. The sedimentary substrate isselected by the current (grain size), there is fine sediment.Fine sand of the high level on the left (SFHN), decreasingtoward the center, it occurs in high turbulence in deeperwater and in the mid water.On the opposite (LEE) there is euryhaline and eurytherm (ina big range of salinity and temperature). In the lagoon the communication with open ocean is not so good, inwinter water became cold, in summer very hot so strong variation. SVMC is muddy sand.

Extinctions:Extinct species are 99.5% of all species appeared on Earth. Species have a natural turnover (new species thatare displaced). Their mean duration lasted 1 to few My.Different kind of extinction: 13-

Selective extinction: it affects some species providing advantage to others. More likely for species with small areas and/or reduced populations, high position in trophic chain, high specialization, long biological cycle and large size. - Extinctions with substitutions: in some periods species were substitute with other species keeping the niche occupies. Species alternating through time are ecological vicariants, species changes not their role. Succession in the associations in biogenic reefs in geologic history. - Extinction without substitutions: no other group cover the entire niche. Extinction of one or many species but their role is left uncovered. - Local: disappearance (area affected) - Global: based on their spatial extension (area affected) - Normal: turnover - Mass: numerous taxa in a relatively short time - Catastrophic: mass extinction caused by catastrophic events on the basis of the time factor. A mass extinction is the disappearance of a high number of very diverse taxa during thesame (geologicallyshort) time. The physico-chemical variables are involved. Well-adapted taxa disappear because specializedand occupying too narrow ecological niches. When the specific combination of ecological factors that definetheir niche are modified, the specialized biota cannot survive. The survivors are opportunistic species,euryecious (many variables, large variation of everything), non- specialized.

Mass extinctions affected at the same time the marine and land biota, plants and animals, protozoans, andmetazoans. Mass extinctions are well beyond the normal turnover (Darwinian evolution). The characters thatallow species to escape mass extinctions are unrelated to those that make organisms survive in «normal» time.

Mass extinctions break the hegemony of long-evolved, well adapted, large groups and open new possibilities(=ecological niches) to emerging groups that can then evolve by adaptive radiation (radiating from the originalsite of speciation, spreading

The fossil record, although incomplete, provides evidence of several extinction events throughout Earth's history. Five of these events, known as the "Big Five," are universally recognized in the Phanerozoic era: at the end of the Ordovician, Devonian, Permian, Triassic, and Cretaceous periods. Additionally, four extinction events occurred in the Cambrian period, and some recognize another phase of extinction at the end of the Pleistocene.

Extinction intensity is represented on the vertical axis, while the horizontal axis represents geological time. The most significant extinction event occurred at the boundary between the Permian and Triassic periods. This intensity is calculated by determining the percentage of genera that did not pass from one interval to the next. In this particular event, more than 90% of species disappeared.

The evolution of life on Earth is marked by relatively short periods of global changes, often caused by external factors that lead to mass extinctions. These changes are often accompanied by dramatic climate shifts.

Rather than an exception in the earth's history, there have been different climate periods:

• Greenhouse earth: a time when the planet had tropical temperatures reaching the poles.
• Snowball earth: a global ice age where ice covers the entire planet.
• Icehouse earth: a global climate where ice ages are possible.

During ice ages, the sea level reduces due to less liquid water in the oceans, resulting in a decrease in magnitude of a few meters. For example, during the Last Glacial Maximum (LGM) around 20,000 years ago, the sea level was 130 meters below its current level. During interglacial periods, the sea level rises by a few meters to several meters.

The phanerozoic climate change is represented by a black line, which indicates the calculated average. There have been glacial periods in recent times, such as the Carboniferous/Permian (C/P) and the Ordovician/Silurian (O/S). These glacial periods are associated with extinctions.

The implication of climate change is that before human impact, climate change was not as fast, whereas now it is occurring at a rapid pace, making adaptation more difficult. The causes of climate change have also changed.

The radiation was different (Milinkoviccycle), the disposition of the plates, the moderating effects of ocean along the coast (extreme of extreme when it was super continent), the coastal line was reduced when there was a supercontinent, volcanic activity led gas and CO2 into the atmosphere. Even underwater volcanism is important. Supercontinent itself is an extreme condition cause of all these.

Esame: evidence and reason, separate things.

The geological evidence of glaciations during icehouse are marine ice floating at middle latitudes and glacial till in marine sediments. Evidence

Icehouse is fostered by periods of weak seafloor spreading or persistence of supercontinents. Reasons

In the late Paleozoic and Cenozoic, the continents joined N-S forced a strong longitudinal circulation, fostering the climate cooling.

During icehouse there was marine regression (sea level drop, contrary of transgression: sea level rise). There was good ocean circulation (sea water is homogeneous not thermocline).

good oxygenation, scarce volcanic activity (weak sea floor spreading), low CO2 concentration and deep CCD (carbonate compensation depth, ideal depth at which whatever is made by carbonite is dissolved below) there is the aragonite compensation depth and the calcite compensation depth both have the same chemical formula: CaCO3 the difference is the mineralogical structure (shape) this influences their solubility. Aragonite is more soluble than calcite and is the first to precipitate. ACD is shallower. Corals are made by aragonite and CRA by magnesium calcite, even more soluble than aragonite. This saturation state of water is important in order to understand what the physiological effort is to sustain the calcification. The physical environment has a lot to do with the distribution, but organisms may always proceed against the gradients cause they can control their equilibrium. During green-house: the other way round.

The reconstruction of the past CO2 concentration: in the past was very high,

Now in warm phases no. strong decrease from Carboniferous and Permian.