Introduction to marine biology

Food web

Ecosystems

Examples

Examples

Examples

Plankton

Zooplankton

Phytoplankton

Nekton

Pelagos

Benthos

Introduction to Marine Biology

Coccolithophores

- phore means round, lithos means rock and cocco means calcium carbonate/chalk => creates rocks with calcium carbonate - unique because they have these calcium carbonate shell/scales for protection - important microfossils because they can sediment and we can find them in rocks which can prove that the place where the rocks are found was an ocean for a long time where in the surface it was warm enough for that (ex Bourgogne and even Paris). - they are small so they can live in subtropical or tropical areas, but also in tempered areas. - interesting to study from the point of view of climate change because in the context of acidification of water, they will have to adapt because their calcium carbonate shell would be a problem to that. - when they die and sediment, they export the carbon they had to the bottom ⇒ they create carbon sinks in the bottoms of the ocean by exporting it from the surface. - they give us chalk.

- photosynthetic - mixotrophic (both autotrophic when there is a lot of light and heterotrophic when not so much light) - smaller than diatoms and require less nutrients to develop so they live mostly in tropical and subtropical areas where the warm water is less rich in nutrients - some species are endosymbionts, which means they can live in a symbiotic relationship with other organisms such as corals - the flagellates enable them to move - several species can cause visible colorification on the surface of water in a rapid agglomeration : “red tied” or Harmful Algal Bloom (HAB) which can contaminate shellfish which is dangerous for human consumption and some beaches can be closed too to prevent humans interacting with them. Other species can cause visible blue light on water surfaces. - they are present in all aquatic environments : sea, fresh water, even snow/ice

- big part of Earth biomass - 20-50% of oxygen - unicellular, can be just 1 individual or a colony of individuals - different shapes - they are big microalgae 0.1-0.2 mm - some can be used in cosmetics or health - they can’t move or move slowly so they mostly sink slowly or fast, but there is no way for them to get to the surface where there is light. - they are always found in places of water where there is silicate and a lot of nutrients, which are necessary to survive → these nutrients are closer to the bottom but when it’s cold there is a mixing which makes them rather get up to the surface ; so the diatoms bloom in spring

Box jelly

Tunicates

Salps

Ctenophores

Chaetognatha

Cnidareans

Meroplankton

Copepods

Phronima

Krill

Crustaceans

Vellela

Appendicularians

Ecosystems

- Small but very dangerous jellyfish (only some species)- The most dangerous species are the ones living in tropics like Australia, Malaysia, Philippines, Thailand - They sting so much that can cause a cardiac arrests in humans (not often but possible)

- A few cm long pelagic organism - It has two sets of eyes, peaks, a helmet-like structure - The female of this species uses its claws to kill much bigger animals, eat them partially and use the rest to put in eggs; when the eggs hatch, they'll be able to consume the rests of the animal - It has inspired the xenomorph alien from Alien Resurrection.

Viruses are not really alive : they contain elements of life that can only be activated by connecting to a host organism. By mixing the elements of life with the host, the virus will be able to reproduce and multiply. Most marine viruses can not interract with humans.

Copepods, often referred to as the "insects of the sea," are tiny crustaceans that inhabit both freshwater and saltwater environments. - They are primarily planktonic (not meroplankton). - They play a crucial role in marine and freshwater ecosystems, serving as a major food source for fish and representing a significant portion of zooplankton. - They actively participate in the carbon cycle. By consuming phytoplankton (such as diatoms) near the surface, copepods transfer carbon from the atmosphere to deeper waters. Their fecal pellets, rich in carbon, sink rapidly to the ocean depths, contributing to carbon sequestration. - They are incredibly adaptable and thrive in various habitats. - Most copepods measure 1 to 2 mm in length, with a teardrop-shaped body. - They actively hunt by extending their bodies to catch microalgae cells. They consume an astonishing 100,000 cells per day, filtering copious amounts of water.

Can only reproduce assexually

Can reproduce sexually and assexually

Mortal

Immortal unless sterilized

Can only rely on nutrients

Can be autotrophic, heterotrophic or parasitic

Cannot move (except for sperm and ova)

Can move independently

Eurkaryotic : DNA contained in the nucleus

Prokaryotic : no nucleus, DNA is contained in cytoplasm

Cell

Bacteria

Meroplankton is usually larvae of animals that will become something else than plankton. For example, crab, slipper lobster ⇒ plankton as baby and benthos habitant as adult. Another example, jellyfish ⇒ young ones drift with the courant then adult ones sleep other example, sea urchin ⇒ same

Tunicates have a sort of tunique as a house

Vellela polyp is a free floating polyp colony - It can be 5 to 10 cm long, deep blue - It has a sail that sticks out the surface of the sea and allows it to catch the wind to move - Sometimes they happen to get on the beach in spring due to the direction of the wind - They catch prey (generally phytoplankton) using tentacles or bear cnidocytes - A Vellela colony is either only female or only male and each of the individuals will produce a mini jellyfish of the corresponding gender. - They have stinging cells : on the external part, there is a hair-like trigger (cnidocil) which, if touched, will trigger a reaction of ejection of toxic contents (harpoon) in the body of the prey and immobilize it

Crustaceans represent the major part of phytoplankton and are very important in the marine ecosystem preservation efforts

Cnidarians are jellies, who have 2 basic forms (stages) of life : 1) swimming creatures : medusae (jellyfish) 2) static (sessile) polyps Both have bear cnidocytes, whiche are special cells used to capture the pray with toxins and one single body cavity used for digestion and respiration. Some cnidarians on polyp stage can produce colonies but in that case, they will not become jellyfish but form corals.

Krill are small crustaceans - They live in all types of ecosystems, especially in cold areas, which contain more phytoplankton - They are main source of food for a lot of bigger organisms - They represent the largest total biomass of the Southern Ocean - Over half of this biomass is eaten by Megafauna like seals, penguins, squids, whales - Krill is being fished commercially, which is a problem because it impacts the food chain and can make the system collapse.

Ctenophores (comb + carry) :

- Transparent type of jellyfish that is however different from the cnidarians - Doesn't have stinging cells, but sticky cells - They capture the prey by sticking to its body and using the cilia to ingest it - When the prey is swallowed, it is liquefied - The size of ctenophores can vary from a few mm to 1.5m - It is not dangerous to humans because it's too weak compared to us - The body is like one of a jelly with an internal cavity and those sticky cells - It has inspired the aliens from the movie The Abyss - It reflects light with its “combs” - Carnivorous even if fragile - Can live everywhere even in abyss

- solitary - free swimming - exist in all oceans of the world - has filtofiders (filters) - 1 cm long - looks like un têtard - produces a shell/house made of cellulose - for most, the house completely surrounds the animal and helps them find food by only agitating the tail which makes a courant of water inside the house and the nutritive matter will stick to their filters and they will put away the house with those matters and create a new house quite often as they grow (can change every 4h) - are smart

Chaetognatha (hair + jaw) : - transparent, tall, muscular, can jump and swim quickly to capture the prey - all species are hermaphroditic

- Solitary or in colony - Contracts the body to pump water through it to move (one of the most efficient examples of jet propension in the animal world) - Phronima can use salps party as food and party as a place to lay eggs so when the eggs hatch they can eat the rest of the cell → then phronima herself becomes prey for fish