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...)
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Image 1
A fin whale surfacing in Greenland
The fin whale (Balaenoptera physalus), also known as the finback whale or common rorqual, is a species of
baleen whale and the second-longest
cetacean after the
blue whale. The biggest individual reportedly measured 26 m (85 ft) in length, with a maximum recorded weight of 77,000–81,000 kg (170,000–179,000 lb). The fin whale's body is long, slender and brownish-gray in color, with a paler underside to appear less conspicuous from below (
countershading).
At least two recognized subspecies exist, one in the
North Atlantic and one across the
Southern Hemisphere. It is found in all the major oceans, from
polar to tropical waters, though it is absent only from waters close to the
pack ice at the poles and relatively small areas of water away from the open ocean. The highest population density occurs in
temperate and cool waters. Its prey mainly consists of smaller
schooling fish, small squid, or crustaceans, including
copepods and
krill. Mating takes place in temperate, low-latitude seas during the winter. Fin whales are often observed in pods of 6–10 animals, with whom they communicate utilizing frequency-modulated sounds, ranging from 16 to 40 hertz. (Full article...)
Sea urchins (/ˈɜːrtʃɪnz/) are
spiny, globular
echinoderms in the class Echinoidea. About 950 species of sea urchin are distributed on the seabeds of every ocean and inhabit every depth zone from the
intertidal seashore down to 5,000 meters (16,000 ft; 2,700 fathoms). The spherical, hard shells (
tests) of sea urchins are round and covered in spines. Most urchin spines range in length from 3 to 10 cm (1 to 4 in), with outliers such as the
black sea urchin possessing spines as long as 30 cm (12 in). Sea urchins move slowly, crawling with
tube feet, and also propel themselves with their spines. Although
algae are the primary diet, sea urchins also eat slow-moving (
sessile) animals.
Predators that eat sea urchins include a wide variety of fish,
starfish,
crabs,
marine mammals, and humans.
Like all echinoderms, adult sea urchins have fivefold symmetry, but their
pluteus larvae feature
bilateral (mirror) symmetry, indicating that the sea urchin belongs to the
Bilateria, along with
chordates,
arthropods,
annelids and
molluscs. Sea urchins are found in every ocean and in every climate, from the
tropics to the
polar regions, and inhabit marine benthic (sea bed) habitats, from rocky shores to
hadal zone depths. The fossil record of the Echinoids dates from the
Ordovician period, some 450 million years ago. The closest echinoderm relatives of the sea urchin are the
sea cucumbers (Holothuroidea), which like them are
deuterostomes, a clade that includes the
chordates. (
Sand dollars are a separate order in the sea urchin class Echinoidea.) (Full article...)
The sea otter (Enhydra lutris) is a
marine mammal native to the coasts of the northern and eastern
North Pacific Ocean. Adult sea
otters typically weigh between 14 and 45 kg (30 and 100 lb), making them the heaviest members of the
weasel family, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of
fur, the densest in the animal kingdom. Although it can walk on land, the sea otter is capable of living exclusively in the ocean.
The sea otter inhabits nearshore environments, where it dives to the sea floor to
forage. It preys mostly on marine
invertebrates such as
sea urchins, various
mollusks and
crustaceans, and some species of
fish. Its foraging and eating habits are noteworthy in several respects. Its
use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a
keystone species, controlling
sea urchin populations which would otherwise inflict extensive damage to
kelp forestecosystems. Its diet includes prey species that are also valued by humans as food, leading to conflicts between sea otters and fisheries. (Full article...)
Image 4
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...)
Image 5
Bottlenose dolphin surfing in the wake of a research boat
Numerous investigations of bottlenose dolphin intelligence have been conducted, examining
mimicry, use of
artificial language, object categorization, and
self-recognition. They can use tools (sponging; using marine sponges to forage for food sources they normally could not access) and transmit cultural knowledge from generation to generation, and their considerable intelligence has driven interaction with humans. Bottlenose dolphins gained popularity from
aquarium shows and television programs such as Flipper. They have also been trained by militaries to locate
sea mines or detect and mark enemy divers. In some areas, they cooperate with local fishermen by driving fish into their nets and eating the fish that escape. Some encounters with humans are harmful to the dolphins: people hunt them for food, and dolphins are killed inadvertently as a
bycatch of
tuna fishing and by getting caught in
crab traps. (Full article...)
The dugong (/ˈd(j)uːɡɒŋ/; Dugong dugon) is a
marine mammal. It is one of four living species of the order
Sirenia, which also includes three species of
manatees. It is the only living representative of the once-diverse family
Dugongidae; its closest modern relative,
Steller's sea cow (Hydrodamalis gigas), was hunted to
extinction in the 18th century.
The dugong is the only sirenian in its range, which spans the waters of some 40 countries and territories throughout the
Indo-West Pacific. The dugong is largely dependent on
seagrass communities for subsistence and is thus restricted to the coastal habitats that support
seagrass meadows, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as
bays,
mangrovechannels, the waters of large
inshore islands and inter-reefal waters. The northern waters of Australia between
Shark Bay and
Moreton Bay are believed to be the dugong's contemporary stronghold. (Full article...)
Acamptonectes is a
genus of
ophthalmosauridichthyosaurs, a type of dolphin-like
marine reptiles, that lived during the
Early Cretaceous around 130 million years ago. The first specimen, a partial adult skeleton, was discovered in
Speeton, England, in 1958, but was not formally described until 2012 by Valentin Fischer and colleagues. They also recognised a partial
subadult skeleton belonging to the genus from
Cremlingen, Germany, and specimens from other localities in England. The genus contains the single
speciesAcamptonectes densus; the generic name means "rigid swimmer" and the specific name means "compact" or "tightly packed".
The
generic name refers to unusual adaptations in the body of Acamptonectes that made its trunk rigid, including tightly fitting bones in the
occiput (back and lower part of the skull) and interlocking vertebral centra ("bodies" of the vertebrae), which were likely adaptations that enabled it to swim at high speeds with
a tuna-like form of locomotion. Other distinguishing characteristics include an extremely slender snout and unique ridges on the
basioccipital bone of the braincase. As an ichthyosaur, Acamptonectes had large
eye sockets and a
tail fluke. Acamptonectes was similar in
morphology to the related but earlier
ophthalmosaurinesOphthalmosaurus and Mollesaurus. (Full article...)
Image 10
Four examples of cnidaria (clockwise, from top left):
Cnidaria (/nɪˈdɛəriə,naɪ-/) is a
phylum under kingdom
Animalia containing over 11,000
species of
aquatic animals found both in
fresh water and
marine environments (predominantly the latter), including
jellyfish,
hydroids,
sea anemones,
corals and some of the smallest marine
parasites. Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of
cnidocytes or cnidoblasts, specialized cells with ejectable
flagella used mainly for
envenomation and capturing
prey. Their bodies consist of
mesoglea, a non-living, jelly-like substance, sandwiched between two layers of
epithelium that are mostly one
cell thick. Cnidarians are also some of the only animals that can reproduce both sexually and asexually.
Cnidarians mostly have two basic body forms: swimming
medusae and
sessilepolyps, both of which are
radially symmetrical with mouths surrounded by
tentacles that bear cnidocytes, which are specialized stinging cells used to capture prey. Both forms have a single
orifice and body cavity that are used for
digestion and
respiration. Many cnidarian species produce
colonies that are single organisms composed of medusa-like or
polyp-like
zooids, or both (hence they are
trimorphic). Cnidarians' activities are coordinated by a decentralized
nerve net and
simple receptors. Cnidarians also have Rhopalia, which are involved in gravity sensing and sometimes chemoreception. Several free-swimming species of
Cubozoa and
Scyphozoa possess balance-sensing
statocysts, and some have
simple eyes. Not all cnidarians
reproduce sexually, but many species have complex life cycles of
asexual polyp stages and sexual medusae stages. Some, however, omit either the polyp or the medusa stage, and the parasitic classes evolved to have neither form. (Full article...)
Marine microorganisms have been variously estimated to make up about 70%, or about 90%, of the
biomass in the ocean. Taken together they form the
marine microbiome. Over billions of years this microbiome has evolved many life styles and adaptations and come to participate in the
global cycling of almost all chemical elements. Microorganisms are crucial to nutrient recycling in
ecosystems as they act as
decomposers. They are also responsible for nearly all
photosynthesis that occurs in the ocean, as well as the cycling of
carbon,
nitrogen,
phosphorus and other
nutrients and trace elements. Marine microorganisms sequester large amounts of carbon and produce much of the world's oxygen. (Full article...)
Image 5Common-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 6Ocean 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 13On 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 18Topological 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 19
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 27Reconstruction 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 28Microplastics found in sediments on the seafloor (from Marine habitat)
Image 35Sponges have no nervous, digestive or circulatory system (from Marine invertebrates)
Image 36Estuaries 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 39Whales were close to extinction until legislation was put in place. (from Marine conservation)
Image 40A 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 41The 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 42
Diagram of a mycoloop (fungus loop)
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 43The 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 48Food 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 49Waves 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 50Cryptic interactions in the marine food web. Red:
mixotrophy; green:
ontogenetic and species differences; purple: microbial cross‐feeding; orange:
auxotrophy; blue: cellular carbon partitioning. (from Marine food web)
Image 53Cycling 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 57The 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 60Biomass pyramids. Compared to terrestrial biomass pyramids, aquatic pyramids are generally inverted at the base. (from Marine food web)
Image 61Conceptual diagram of faunal community structure and food-web patterns along fluid-flux gradients within
Guaymas seep and vent ecosystems. (from Marine food web)
Image 62A 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 63A protected sea turtle area that warns of fines and imprisonment on a beach in Miami, Florida. (from Marine conservation)
Image 64Chytrid 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 65Schematic 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 69640 µm microplastic found in the deep sea amphipod Eurythenes plasticus (from Marine habitat)
Image 70Cnidarians 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)
Image 71The 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)
Image 72In 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 76Elevation-area graph showing the proportion of land area at given heights and the proportion of ocean area at given depths (from Marine habitat)
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 84Marine Species Changes in Latitude and Depth in three different ocean regions(1973-2019) (from Marine food web)
Image 85Diagram above contains clickable links
Image 86
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 87Antarctic 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)
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
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 96Ocean or marine biomass, in a reversal of terrestrial biomass, can increase at higher trophic levels. (from Marine food web)
Image 98Scanning 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 99Tidepools on rocky shores make turbulent habitats for many forms of marine life (from Marine habitat)
Image 100This
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 101Oceanic 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)
Image 104Ernst 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 105Some 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 107Conference events, such as the events hosted by the
United Nations, help to bring together many stakeholders for awareness and action. (from Marine conservation)
Image 111Lampreys are often parasitic and have a toothed, funnel-like sucking mouth (from Marine vertebrate)
Image 112Phylogenetic 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 113Dickinsonia may be the earliest animal. They appear in the fossil record 571 million to 541 million years ago. (from Marine invertebrates)
Image 117An 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 121Sandy shores provide shifting homes to many species (from Marine habitat)
Image 122Only 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.
Image 125Archaea 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 16Ecosystem 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)
... groups of
bottlenose dolphinss around the Australian Pacific have displayed basic
tool use by wrapping pieces of sponge around their beaks to prevent abrasions. This is a display of a cognitive process similar to that of
great apess.