Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals (e.g. dolphins, whales, otters, and seals) need to surface periodically to breathe air. (Full article...)
Thalassocnus evolved several marine adaptations over 4 million years, such as dense and heavy bones to counteract buoyancy, the internal nostrils migrating farther into the head to help with breathing while completely submerged, the snout becoming wider and more elongated to consume aquatic plants better, and the head angling farther and farther downwards to aid in bottom feeding. The long tail was probably used for diving and balance similar to the modern day beaver (Castor spp.) and platypus (Ornithorhynchus anatinus). (Full article...)
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The false killer whale (Pseudorca crassidens) is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly in tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from having a skull similar to the orca (Orcinus orca), or killer whale.
The false killer whale reaches a maximum length of 6 m (20 ft), though size can vary around the world. It is highly sociable, known to form pods of up to 50 members, and can also form pods with other dolphin species, such as the common bottlenose dolphin (Tursiops truncatus). It can form close bonds with other species, as well as have sexual interactions with them. But the false killer whale has also been known to eat other dolphins, though it typically eats squid and fish. It is a deep-diver; maximum known depth is 927.5 m (3,043 ft); maximum speed is ~ 29 km/h (18 mph). (Full article...)
The Echiura, or spoon worms, are a small group of marineanimals. Once treated as a separate phylum, they are now considered to belong to Annelida. Annelids typically have their bodies divided into segments, but echiurans have secondarily lost their segmentation. The majority of echiurans live in burrows in soft sediment in shallow water, but some live in rock crevices or under boulders, and there are also deep sea forms. More than 230 species have been described. Spoon worms are cylindrical, soft-bodied animals usually possessing a non-retractable proboscis which can be rolled into a scoop-shape to feed. In some species the proboscis is ribbon-like, longer than the trunk and may have a forked tip. Spoon worms vary in size from less than a centimetre in length to more than a metre.
Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Pinnipeds are semiaquatic; they spend the majority of their time in the water but need to return to land for important activities such as mating, breeding and molting. Sea otters tend to live in kelp forests and estuaries. In contrast, the polar bear is mostly terrestrial and only go into the water on occasions of necessity, and are thus much less adapted to aquatic living. The diets of marine mammals vary considerably as well; some eat zooplankton, others eat fish, squid, shellfish, or seagrass, and a few eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened. (Full article...)
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Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many have patterns of yellow, orange, red and green coloration.
The foregut, stomach and intestine run a little below the midline of the body, the anus is at the tip of the tail, and the mouth is under the front. A little above the gut is the rhynchocoel, a cavity which mostly runs above the midline and ends a little short of the rear of the body. All species have a proboscis which lies in the rhynchocoel when inactive but everts to emerge just above the mouth to capture the animal's prey with venom. A highly extensible muscle in the back of the rhynchocoel pulls the proboscis in when an attack ends. A few species with stubby bodies filter feed and have suckers at the front and back ends, with which they attach to a host. (Full article...)
Carson began her career as an aquatic biologist in the U.S. Bureau of Fisheries, and became a full-time nature writer in the 1950s. Her widely praised 1951 bestseller The Sea Around Us won her a U.S. National Book Award, recognition as a gifted writer and financial security. Its success prompted the republication of her first book, Under the Sea Wind (1941), in 1952, which was followed by The Edge of the Sea in 1955 — both were also bestsellers. This sea trilogy explores the whole of ocean life from the shores to the depths. (Full article...)
The emperor penguin (Aptenodytes forsteri) is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching 100 cm (39 in) in length and weighing from 22 to 45 kg (49 to 99 lb). Feathers of the head and back are black and sharply delineated from the white belly, pale-yellow breast and bright-yellow ear patches.
Like all penguins, it is flightless, with a streamlined body, and wings stiffened and flattened into flippers for a marine habitat. Its diet consists primarily of fish, but also includes crustaceans, such as krill, and cephalopods, such as squid. While hunting, the species can remain submerged around 20 minutes, diving to a depth of 535 m (1,755 ft). It has several adaptations to facilitate this, including an unusually structured haemoglobin to allow it to function at low oxygen levels, solid bones to reduce barotrauma, and the ability to reduce its metabolism and shut down non-essential organ functions. (Full article...)
Sea snakes, or coral reef snakes, are elapid snakes that inhabit marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Laticaudinae. Hydrophiinae also includes Australasian terrestrial snakes, whereas Laticaudinae only includes the sea kraits (Laticauda), of which three species are found exclusively in freshwater. If these three freshwater species are excluded, there are 69 species of sea snakes divided among seven genera.
Most sea snakes are venomous, except the genus Emydocephalus, which feeds almost exclusively on fish eggs. Sea snakes are extensively adapted to a fully aquatic life and are unable to move on land, except for the sea kraits, which have limited land movement. They are found in warm coastal waters from the Indian Ocean to the Pacific and are closely related to venomous terrestrial snakes in Australia. (Full article...)
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The pigeye shark or Java shark (Carcharhinus amboinensis) is an uncommon species of requiem shark, in the family Carcharhinidae, found in the warm coastal waters of the eastern Atlantic and western Indo-Pacific. It prefers shallow, murky environments with soft bottoms, and tends to roam within a fairly localised area. With its bulky grey body, small eyes, and short, blunt snout, the pigeye shark looks almost identical to (and is often confused with) the better-known bull shark (C. leucas). The two species differ in vertebral count, the relative sizes of the dorsal fins, and other subtle traits. This shark typically reaches lengths of 1.9–2.5 m (6.2–8.2 ft).
The pigeye shark is an apex predator that mostly hunts low in the water column. It has a varied diet, consisting mainly of bony and cartilaginous fishes and also including crustaceans, molluscs, sea snakes, and cetaceans. This species gives birth to live young, with the developing embryos sustained to term via a placental connection to their mother. Litters of three to thirteen pups are born after a gestation period of nine or twelve months. Young sharks spend their first few years of life in sheltered inshore habitats such as bays, where their movements follow tidal and seasonal patterns. The pigeye shark's size and dentition make it potentially dangerous, though it has not been known to attack humans. The shark is infrequently caught in shark nets protecting beaches and by fisheries, which use it for meat and fins. The IUCN presently assesses this species as vulnerable. (Full article...)
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The porbeagle or porbeagle shark (Lamna nasus) is a species of mackerel shark in the familyLamnidae, distributed widely in the cold and temperate marine waters of the North Atlantic and Southern Hemisphere. In the North Pacific, its ecological equivalent is the closely related salmon shark (L. ditropis). It typically reaches 2.5 m (8.2 ft) in length and a weight of 135 kg (298 lb); North Atlantic sharks grow larger than Southern Hemisphere sharks and differ in coloration and aspects of life history. Gray above and white below, the porbeagle has a very stout midsection that tapers towards the long, pointed snout and the narrow base of the tail. It has large pectoral and first dorsal fins, tiny pelvic, second dorsal, and anal fins, and a crescent-shaped caudal fin. The most distinctive features of this species are its three-cusped teeth, the white blotch at the aft base of its first dorsal fin, and the two pairs of lateral keels on its tail.
The porbeagle is an opportunistic hunter that preys mainly on bony fishes and cephalopods throughout the water column, including the bottom. Most commonly found over food-rich banks on the outer continental shelf, it makes occasional forays both close to shore and into the open ocean to a depth of 1,360 m (4,460 ft). It also conducts long-distance seasonal migrations, generally shifting between shallower and deeper water. The porbeagle is fast and highly active, with physiological adaptations that enable it to maintain a higher body temperature than the surrounding water. It can be solitary or gregarious, and has been known to perform seemingly playful behavior. This shark is aplacental viviparous with oophagy, developing embryos being retained within the mother's uterus and subsisting on non-viable eggs. Females typically bear four pups every year. (Full article...)
More narrow definitions may be restricted to Caridea, to smaller species of either group or to only the marine species. Under a broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long, narrow muscular tails (abdomens), long whiskers (antennae), and slender legs. Any small crustacean which resembles a shrimp tends to be called one. They swim forward by paddling with swimmerets on the underside of their abdomens, although their escape response is typically repeated flicks with the tail driving them backwards very quickly. Crabs and lobsters have strong walking legs, whereas shrimp have thin, fragile legs which they use primarily for perching. (Full article...)
Image 1Elevation-area graph showing the proportion of land area at given heights and the proportion of ocean area at given depths (from Marine habitat)
Image 7Ernst Haeckel's 96th plate, showing some marine invertebrates. Marine invertebrates have a large variety of body plans, which are currently categorised into over 30 phyla. (from Marine invertebrates)
Image 10An in situ perspective of a deep pelagic food web derived from ROV-based observations of feeding, as represented by 20 broad taxonomic groupings. The linkages between predator to prey are coloured according to predator group origin, and loops indicate within-group feeding. The thickness of the lines or edges connecting food web components is scaled to the log of the number of unique ROV feeding observations across the years 1991–2016 between the two groups of animals. The different groups have eight colour-coded types according to main animal types as indicated by the legend and defined here: red, cephalopods; orange, crustaceans; light green, fish; dark green, medusa; purple, siphonophores; blue, ctenophores and grey, all other animals. In this plot, the vertical axis does not correspond to trophic level, because this metric is not readily estimated for all members. (from Marine food web)
Image 11A protected sea turtle area that warns of fines and imprisonment on a beach in Miami, Florida. (from Marine conservation)
Image 12Topological positions versus mobility: (A) bottom-up groups (sessile and drifters), (B) groups at the top of the food web. Phyto, phytoplankton; MacroAlga, macroalgae; Proto, pelagic protozoa; Crus, Crustacea; PelBact, pelagic bacteria; Echino, Echinoderms; Amph, Amphipods; HerbFish, herbivorous fish; Zoopl, zooplankton; SuspFeed, suspension feeders; Polych, polychaetes; Mugil, Mugilidae; Gastropod, gastropods; Blenny, omnivorous blennies; Decapod, decapods; Dpunt, Diplodus puntazzo; Macropl, macroplankton; PlFish, planktivorous fish; Cephalopod, cephalopods; Mcarni, macrocarnivorous fish; Pisc, piscivorous fish; Bird, seabirds; InvFeed1 through InvFeed4, benthic invertebrate feeders. (from Marine food web)
Image 14A microbial mat encrusted with iron oxide on the flank of a seamount can harbour microbial communities dominated by the iron-oxidizing Zetaproteobacteria (from Marine prokaryotes)
Image 15The distribution of anthropogenic stressors faced by marine species threatened with extinction in various marine regions of the world. Numbers in the pie charts indicate the percentage contribution of an anthropogenic stressors' impact in a specific marine region. (from Marine food web)
Model of the energy generating mechanism in marine bacteria
(1) When sunlight strikes a rhodopsin molecule (2) it changes its configuration so a proton is expelled from the cell (3) the chemical potential causes the proton to flow back to the cell (4) thus generating energy (5) in the form of adenosine triphosphate. (from Marine prokaryotes)
Image 23Chytrid parasites of marine diatoms. (A) Chytrid sporangia on Pleurosigma sp. The white arrow indicates the operculate discharge pore. (B) Rhizoids (white arrow) extending into diatom host. (C) Chlorophyll aggregates localized to infection sites (white arrows). (D and E) Single hosts bearing multiple zoosporangia at different stages of development. The white arrow in panel E highlights branching rhizoids. (F) Endobiotic chytrid-like sporangia within diatom frustule. Bars = 10 μm. (from Marine fungi)
Image 28Waves and currents shape the intertidal shoreline, eroding the softer rocks and transporting and grading loose particles into shingles, sand or mud (from Marine habitat)
Image 33The Ocean Cleanup is one of many organizations working toward marine conservation such at this interceptor vessel that prevents plastic from entering the ocean. (from Marine conservation)
Image 37Food web structure in the euphotic zone. The linear food chain large phytoplankton-herbivore-predator (on the left with red arrow connections) has fewer levels than one with small phytoplankton at the base. The microbial loop refers to the flow from the dissolved organic carbon (DOC) via heterotrophic bacteria (Het. Bac.) and microzooplankton to predatory zooplankton (on the right with black solid arrows). Viruses play a major role in the mortality of phytoplankton and heterotrophic bacteria, and recycle organic carbon back to the DOC pool. Other sources of dissolved organic carbon (also dashed black arrows) includes exudation, sloppy feeding, etc. Particulate detritus pools and fluxes are not shown for simplicity. (from Marine food web)
Image 38Whales were close to extinction until legislation was put in place. (from Marine conservation)
Image 41Reconstruction of an ammonite, a highly successful early cephalopod that first appeared in the Devonian (about 400 mya). They became extinct during the same extinction event that killed the land dinosaurs (about 66 mya). (from Marine invertebrates)
Image 42Archaea were initially viewed as extremophiles living in harsh environments, such as the yellow archaea pictured here in a hot spring, but they have since been found in a much broader range of habitats. (from Marine prokaryotes)
Image 43Only 29 percent of the world surface is land. The rest is ocean, home to the marine habitats. The oceans are nearly four kilometres deep on average and are fringed with coastlines that run for nearly 380,000 kilometres.
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Different bacteria shapes (cocci, rods and spirochetes) and their sizes compared with the width of a human hair. A few bacteria are comma-shaped (vibrio). Archaea have similar shapes, though the archaeon Haloquadratum is flat and square.
The unit μm is a measurement of length, the micrometer, equal to 1/1,000 of a millimeter
Image 47Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes (from Marine prokaryotes)
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Mycoloop links between phytoplankton and zooplankton
Chytrid‐mediated trophic links between phytoplankton and zooplankton (mycoloop). While small phytoplankton species can be grazed upon by zooplankton, large phytoplankton species constitute poorly edible or even inedible prey. Chytrid infections on large phytoplankton can induce changes in palatability, as a result of host aggregation (reduced edibility) or mechanistic fragmentation of cells or filaments (increased palatability). First, chytrid parasites extract and repack nutrients and energy from their hosts in form of readily edible zoospores. Second, infected and fragmented hosts including attached sporangia can also be ingested by grazers (i.e. concomitant predation). (from Marine fungi)
Image 51Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes (from Marine fungi)
Image 52Scanning electron micrograph of a strain of Roseobacter, a widespread and important genus of marine bacteria. For scale, the membrane pore size is 0.2 μm in diameter. (from Marine prokaryotes)
Image 53Some representative ocean animal life (not drawn to scale) within their approximate depth-defined ecological habitats. Marine microorganisms exist on the surfaces and within the tissues and organs of the diverse life inhabiting the ocean, across all ocean habitats. (from Marine habitat)
Image 54Ocean surface chlorophyll concentrations in October 2019. The concentration of chlorophyll can be used as a proxy to indicate how many phytoplankton are present. Thus on this global map green indicates where a lot of phytoplankton are present, while blue indicates where few phytoplankton are present. – NASA Earth Observatory 2019. (from Marine food web)
Image 69Conference events, such as the events hosted by the United Nations, help to bring together many stakeholders for awareness and action. (from Marine conservation)
Image 70The pelagic food web, showing the central involvement of marine microorganisms in how the ocean imports nutrients from and then exports them back to the atmosphere and ocean floor (from Marine food web)
Image 72Some lobe-finned fishes, like the extinct Tiktaalik, developed limb-like fins that could take them onto land (from Marine vertebrate)
Image 73This algae bloom occupies sunlit epipelagic waters off the southern coast of England. The algae are maybe feeding on nutrients from land runoff or upwellings at the edge of the continental shelf. (from Marine habitat)
Image 74Oceanic pelagic food web showing energy flow from micronekton to top predators. Line thickness is scaled to the proportion in the diet. (from Marine food web)
Parasitic chytrids can transfer material from large inedible phytoplankton to zooplankton. Chytrids zoospores are excellent food for zooplankton in terms of size (2–5 μm in diameter), shape, nutritional quality (rich in polyunsaturated fatty acids and cholesterols). Large colonies of host phytoplankton may also be fragmented by chytrid infections and become edible to zooplankton. (from Marine fungi)
Image 79Cycling of marine phytoplankton. Phytoplankton live in the photic zone of the ocean, where photosynthesis is possible. During photosynthesis, they assimilate carbon dioxide and release oxygen. If solar radiation is too high, phytoplankton may fall victim to photodegradation. For growth, phytoplankton cells depend on nutrients, which enter the ocean by rivers, continental weathering, and glacial ice meltwater on the poles. Phytoplankton release dissolved organic carbon (DOC) into the ocean. Since phytoplankton are the basis of marine food webs, they serve as prey for zooplankton, fish larvae and other heterotrophic organisms. They can also be degraded by bacteria or by viral lysis. Although some phytoplankton cells, such as dinoflagellates, are able to migrate vertically, they are still incapable of actively moving against currents, so they slowly sink and ultimately fertilize the seafloor with dead cells and detritus. (from Marine food web)
Image 82In the open ocean, sunlit surface epipelagic waters get enough light for photosynthesis, but there are often not enough nutrients. As a result, large areas contain little life apart from migrating animals. (from Marine habitat)
Image 88Biomass pyramids. Compared to terrestrial biomass pyramids, aquatic pyramids are generally inverted at the base. (from Marine food web)
Image 89Conceptual diagram of faunal community structure and food-web patterns along fluid-flux gradients within Guaymas seep and vent ecosystems. (from Marine food web)
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Bacterioplankton and the pelagic marine food web
Solar radiation can have positive (+) or negative (−) effects resulting in increases or decreases in the heterotrophic activity of bacterioplankton. (from Marine prokaryotes)
Image 91Estuaries occur when rivers flow into a coastal bay or inlet. They are nutrient rich and have a transition zone which moves from freshwater to saltwater. (from Marine habitat)
Image 97Cnidarians are the simplest animals with cells organised into tissues. Yet the starlet sea anemone contains the same genes as those that form the vertebrate head. (from Marine invertebrates)
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Estimates of microbial species counts in the three domains of life
Bacteria are the oldest and most biodiverse group, followed by Archaea and Fungi (the most recent groups). In 1998, before awareness of the extent of microbial life had gotten underway, Robert M. May estimated there were 3 million species of living organisms on the planet. But in 2016, Locey and Lennon estimated the number of microorganism species could be as high as 1 trillion. (from Marine prokaryotes)
Image 99A 2016 metagenomic representation of the tree of life using ribosomal protein sequences. The tree includes 92 named bacterial phyla, 26 archaeal phyla and five eukaryotic supergroups. Major lineages are assigned arbitrary colours and named in italics with well-characterized lineage names. Lineages lacking an isolated representative are highlighted with non-italicized names and red dots. (from Marine prokaryotes)
Image 102Phylogenetic tree representing bacterial OTUs from clone libraries and next-generation sequencing. OTUs from next-generation sequencing are displayed if the OTU contained more than two sequences in the unrarefied OTU table (3626 OTUs). (from Marine prokaryotes)
Image 105The deep sea amphipodEurythenes plasticus, named after microplastics found in its body, demonstrating plastic pollution affects marine habitats even 6000m below sea level. (from Marine habitat)
Image 109Antarctic marine food web. Potter Cove 2018. Vertical position indicates trophic level and node widths are proportional to total degree (in and out). Node colors represent functional groups. (from Marine food web)
Image 114640 μm microplastic found in the deep sea amphipod Eurythenes plasticus (from Marine habitat)
Image 115Common-enemy graph of Antarctic food web. Potter Cove 2018. Nodes represent basal species and links indirect interactions (shared predators). Node and link widths are proportional to number of shared predators. Node colors represent functional groups. (from Marine food web)
Image 117Schematic representation of the changes in abundance between trophic groups in a temperate rocky reef ecosystem. (a) Interactions at equilibrium. (b) Trophic cascade following disturbance. In this case, the otter is the dominant predator and the macroalgae are kelp. Arrows with positive (green, +) signs indicate positive effects on abundance while those with negative (red, -) indicate negative effects on abundance. The size of the bubbles represents the change in population abundance and associated altered interaction strength following disturbance. (from Marine food web)
Image 121On average there are more than one million microbial cells in every drop of seawater, and their collective metabolisms not only recycle nutrients that can then be used by larger organisms but also catalyze key chemical transformations that maintain Earth's habitability. (from Marine food web)
Image 122Diagram above contains clickable links
Image 123Jellyfish are easy to capture and digest and may be more important as food sources than was previously thought. (from Marine food web)
Image 24Ecosystem services delivered by epibenthicbivalve reefs. Reefs provide coastal protection through erosion control and shoreline stabilization, and modify the physical landscape by ecosystem engineering, thereby providing habitat for species by facilitative interactions with other habitats such as tidal flat benthic communities, seagrasses and marshes. (from Marine ecosystem)
... whale and dolphin mothers ‘suckle’ their young underwater! Mothers have muscular mammary glands and ‘squirt’ their milk into the calf’s mouth, to ensure that the calf takes in as much of the energy rich milk as possible.
... in spite of their enormous mass, baleen whales are capable of leaping completely out of the water, particularly the Humpback Whale.
... Until the late 16th century sharks were usually referred to in the English language as sea-dogs. The name "Shark" first came into use around the late 1560s to refer to the large sharks of the Caribbean Sea.
... that the Southern Right Whale got its name because it was the ‘right’ whale to kill? Because they swim slowly, close to the shore and float when killed, the whalers thought them the right whales to kill!
... The name shark may have originated from the Mayan word for shark, xoc, pronounced "shock" or "shawk".
The Antarctic krill (Euphausia superba) is a species of krill found in the Antarctic waters of the Southern Ocean. Antarctic krill are shrimp-like invertebrates that live in large schools, called swarms, sometimes reaching densities of 10,000 - 30,000 individual animals per cubic meter.
Although the uses for and reasons behind the development of their massive black compound eyes (pictured above) remain a mystery, there is no doubt that Antarctic krill have one of the most fantastic structures for vision seen in nature.
Krill can shrink in size from one molt to the next, which is generally thought to be a survival strategy to adapt to scarce food supplies (a smaller body needs less energy, i.e., food). However, the animal's eyes do not shrink when this happens. The ratio between eye size and body length has thus been found to be a reliable indicator of starvation.