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...)
Phoronids (scientific name Phoronida, sometimes called horseshoe worms) are a small
phylum of marine animals that
filter-feed with a
lophophore (a "crown" of tentacles), and build upright tubes of
chitin to support and protect their soft bodies. They live in most of the oceans and seas, including the Arctic Ocean but excluding the
Antarctic Ocean, and between the
intertidal zone and about 400 meters down. Most adult phoronids are 2 cm long and about 1.5 mm wide, although the largest are 50 cm long.
The sei whale (/seɪ/SAY, Norwegian:[sæɪ]; Balaenoptera borealis) is a
baleen whale. It is one of ten
rorqual species, and the third-largest member after the
blue and
fin whales. They can grow up to 19.5 m (64 ft) in length and weigh as much as 28 t (28 long tons; 31 short tons). Two subspecies are recognized: B. b. borealis and B. b. schlegelii. The whale's
ventral surface has sporadic markings ranging from light grey to white, and its body is usually dark steel grey in colour. It is among the fastest of all
cetaceans, and can reach speeds of up to 50 km/h (31 mph) over short distances.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids
polar and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool, subpolar waters in summer to
temperate, subtropical waters in winter with a lifespan of 70 years. It is a
filter feeder, with its diet consisting primarily of
copepods,
krill, and other
zooplankton. It is typically solitary or can be found in groups numbering half a dozen. During the breeding period, a mating pair will remain together. Sei whale vocalizations usually lasts half a second, and occurs at 240–625 hertz. (Full article...)
Image 3
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...)
Image 4
Cetacea is an
infraorder that comprises the 94 species of
whales,
dolphins, and
porpoises. It is divided into
toothed whales (Odontoceti) and
baleen whales (Mysticeti), which diverged from each other in the
Eocene some 50
million years ago (mya). Cetaceans are descended from land-dwelling hoofed mammals, and the now extinct
archaeocetes represent the several transitional phases from terrestrial to completely aquatic. Historically, cetaceans were thought to have descended from the wolf-like
mesonychians, but
cladistic analyses confirm their placement with
even-toed ungulates in the order Cetartiodactyla.
Whale populations were drastically reduced in the 20th century from intensive
whaling, and the activity was globally banned in 1982. Smaller cetaceans are at risk of accidentally getting caught by fishing vessels using, namely,
seine fishing,
drift netting, or
gill netting operations. (Full article...)
The sea mink (Neogale macrodon) is a
recently extinct species of
mink that lived on the eastern coast of North America around the
Gulf of Maine on the
New England seaboard. It was most closely related to the
American mink (Neogale vison), with continuing debate about whether or not the sea mink should be considered a subspecies of the American mink (as Neogale vison macrodon) or a species of its own. The main justification for a separate species designation is the size difference between the two minks, but other distinctions have been made, such as its redder fur. The only known remains are bone fragments unearthed in Native American
shell middens. Its actual size is speculative, based largely on tooth remains.
The sea mink was first
described in 1903, after its
extinction; information regarding its external appearance and habits stem from speculation and from accounts made by
fur traders and Native Americans. It may have exhibited behavior similar to the American mink, in that it probably maintained
home ranges, was
polygynandrous, and had a similar diet, though more seaward-oriented. It was probably found on the
New England coast and the
Maritime Provinces, though its range may have stretched further south during the
last glacial period. Conversely, its range may have been restricted solely to the New England coast, specifically the
Gulf of Maine, or just to the nearby islands. The largest of the minks, the sea mink was more desirable to fur traders and became extinct in the late 19th or early 20th century. (Full article...)
Image 6
The silky shark (Carcharhinus falciformis), also known by numerous names such as blackspot shark, gray whaler shark, olive shark, ridgeback shark, sickle shark, sickle-shaped shark and sickle silk shark, is a
species of
requiem shark, in the
familyCarcharhinidae, named for the smooth texture of its skin. It is one of the most abundant sharks in the
pelagic zone, and can be found around the world in tropical waters. Highly mobile and
migratory, this shark is most often found over the edge of the
continental shelf down to 50 m (164 ft). The silky shark has a slender, streamlined body and typically grows to a length of 2.5 m (8 ft 2 in). It can be distinguished from other large requiem sharks by its relatively small first
dorsal fin with a curving rear margin, its tiny second dorsal fin with a long free rear tip, and its long, sickle-shaped
pectoral fins. It is a deep, metallic bronze-gray above and white below.
With prey often scarce in its oceanic environment, the silky shark is a swift, inquisitive, and persistent hunter. It feeds mainly on
bony fishes and
cephalopods, and has been known to drive them into compacted
schools before launching open-mouthed, slashing attacks. This species often trails schools of
tuna, a favored prey. Its sense of hearing is extremely acute, allowing it to localize the low-frequency noises generated by other feeding animals, and, by extension, sources of food. The silky shark is
viviparous, meaning that the developing
embryos are sustained by a
placental connection to their mother. Significant geographical variation is seen in its
life history details. Reproduction occurs year-round except in the
Gulf of Mexico, where it follows a seasonal cycle. Females give birth to litters of up to 16 pups annually or biennially. The newborn sharks spend their first months in relatively sheltered reef nurseries on the outer continental shelf, growing substantially before moving into the open ocean. (Full article...)
Bivalvia (/baɪˈvælviə/), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a
class of marine and freshwater
molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no
head and they lack some usual molluscan organs, like the
radula and the
odontophore. The class includes the
clams,
oysters,
cockles,
mussels,
scallops, and numerous other
families that live in saltwater, as well as a number of families that live in freshwater. The majority are
filter feeders. The
gills have evolved into
ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from
predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and
file shells, can
swim.
Shipworms bore into wood, clay, or stone and live inside these substances.
The
shell of a bivalve is composed of
calcium carbonate, and consists of two, usually similar, parts called
valves. These valves are for feeding and for disposal of waste. These are joined together along one edge (the
hinge line) by a flexible
ligament that, usually in conjunction with interlocking "teeth" on each of the valves, forms the
hinge. This arrangement allows the shell to be opened and closed without the two halves detaching. The shell is typically
bilaterally symmetrical, with the hinge lying in the
sagittal plane. Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length, but the majority of species do not exceed 10 cm (4 in). (Full article...)
Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing
tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for efficient
locomotion. The tentacles are armed with
stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex
life cycle. The medusa is normally the sexual phase, which produces
planula larvae. These then disperse widely and enter a sedentary
polyp phase which may include asexual budding before reaching sexual maturity. (Full article...)
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162
species of
unsegmentedmarineannelid worms. Sipuncula was once considered a
phylum, but was demoted to a class of Annelida, based on recent molecular work.
Sipunculans vary in size but most species are under 10 cm (4 in) in length. The body is divided into an unsegmented, bulbous trunk and a narrower,
anterior section, called the "introvert", which can be retracted into the trunk. The mouth is at the tip of the introvert and is surrounded in most groups by a ring of short tentacles. With no hard parts, the body is flexible and mobile. Although found in a range of habitats throughout the world's oceans, the majority of species live in shallow water habitats, burrowing under the surface of sandy and muddy substrates. Others live under stones, in rock crevices or in other concealed locations. (Full article...)
The echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the
biotic desert of the
deep sea, as well as shallower oceans. Most echinoderms are able to
reproduce asexually and
regenerate tissue, organs and limbs; in some cases, they can undergo complete regeneration from a single limb. Geologically, the value of echinoderms is in their
ossifieddermalendoskeletons, which are major contributors to many
limestone formations and can provide valuable clues as to the geological environment. They were the most used species in regenerative research in the 19th and 20th centuries. Further, some scientists hold that the
radiation of echinoderms was responsible for the
Mesozoic Marine Revolution. (Full article...)
Image 1Only 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 2Conceptual diagram of faunal community structure and food-web patterns along fluid-flux gradients within
Guaymas seep and vent ecosystems. (from Marine food web)
Image 4Cnidarians 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 5Estuaries 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 6Ernst 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 7Sandy shores provide shifting homes to many species (from Marine habitat)
Image 9The 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 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 12Oceanic 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 15Waves 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 17The 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 18Sponges have no nervous, digestive or circulatory system (from Marine invertebrates)
Image 19Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes (from Marine fungi)
Solar radiation can have positive (+) or negative (−) effects resulting in increases or decreases in the heterotrophic activity of bacterioplankton. (from Marine prokaryotes)
Image 35Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes (from Marine prokaryotes)
Image 37Biomass pyramids. Compared to terrestrial biomass pyramids, aquatic pyramids are generally inverted at the base. (from Marine food web)
Image 38Elevation-area graph showing the proportion of land area at given heights and the proportion of ocean area at given depths (from Marine habitat)
Image 39
The global continental shelf, highlighted in light green, defines the extent of marine coastal habitats, and occupies 5% of the total world area
Image 40Archaea 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 41Coral reefs provide marine habitats for tube sponges, which in turn become marine habitats for fishes (from Marine habitat)
Image 42Cryptic 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 44Ocean 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 45Topological 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 46Reconstruction 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 47A 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 54Cycling 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 57A protected sea turtle area that warns of fines and imprisonment on a beach in Miami, Florida. (from Marine conservation)
Image 58Scanning 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 60The 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 63Conference events, such as the events hosted by the
United Nations, help to bring together many stakeholders for awareness and action. (from Marine conservation)
Image 69The 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)
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 74Jellyfish are easy to capture and digest and may be more important as food sources than was previously thought. (from Marine food web)
Image 75Ocean Conservation Namibia rescuing a seal that was entangled in discarded fishing nets. (from Marine conservation)
Image 76
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 80Phylogenetic 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 81
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 87On 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 92Antarctic 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 95Some lobe-finned fishes, like the extinct Tiktaalik, developed limb-like fins that could take them onto land (from Marine vertebrate)
Image 96Food 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 98Common-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 99Halfbeak as larvae are one of the organisms adapted to the unique properties of the microlayer (from Marine habitat)
Image 100Ocean or marine biomass, in a reversal of terrestrial biomass, can increase at higher trophic levels. (from Marine food web)
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 106In 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)
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 109This
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 111Chytrid 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 112Schematic 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 115A 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 116Some 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 9Ecosystem 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)
... that Concurrent Computer Corporation was consumed in a "minnow-swallows-the-whale" merger during the junk bonds era, but unusually, kept its name, CEO, and headquarters?
... Despite the common myth that sharks are largely instinct-driven "eating machines", recent studies have indicated that many species possess powerful problem-solving skills, social complexity and curiosity.
... newborn cetacean calves ‘suckle’ three to four times each hour and will suckle from their mothers for six months or more.
... the
Beluga Whale's milkfat is so high, the calf gains up to 2 kilograms per day on the diet. It is so fatty that the colour is green.
... the
songs of
whales were
sent into space aboard the
Voyager spacecraft to represent sounds from Planet
Earth.
... observations of cetaceans date back to at least
the classical period in Greece, when fisherpeople made notches on the dorsal fins of
dolphinss entangled in nets in order to tell them apart years later.
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