Jellyfish Blooms
The presence of ocean blooms is usually seasonal, responding to prey availability and increasing with temperature and sunshine. Ocean currents tend to congregate jellyfish into large swarms or "blooms", consisting of hundreds or thousands of individuals. In addition to sometimes being concentrated by ocean currents, blooms can result from unusually high populations in some years. Bloom formation is a complex process that depends on ocean currents, nutrients, temperature, predation, and oxygen concentrations. Jellyfish are better able to survive in oxygen-poor water than competitors, and thus can thrive on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are better able to survive in warmer waters. Jellyfish are likely to stay in blooms that are quite large and can reach up to 100,000 in each.
The global increase in jellyfish bloom frequency may stem from human impact. In some locations jellyfish may be filling ecological niches formerly occupied by now overfished creatures, but this hypothesis lacks supporting data. Jellyfish researcher Marsh Youngbluth further clarifies that "jellyfish feed on the same kinds of prey as adult and young fish, so if fish are removed from the equation, jellyfish are likely to move in."
Jellyfish blooms cause problems for mankind. The most obvious are human stings (sometimes deadly) and tourism declines on coasts.
Other severe implications are destroying fish nets, poisoning or crushing captured fish, consuming fish eggs and young fish.
Clogging also causes many problems including stoppage of nuclear power plants and desalination plants, as well as clogging engines of ships and even overturning of boats by one of the largest species, the Nomura's jellyfish.
Moray Eel
Moray eels are cosmopolitan eels of the family Muraenidae. The approximately 200 species in 15 genera are almost exclusively marine, but several species are regularly seen in brackish water and a few, for example the freshwater moray (Gymnothorax polyuranodon) can sometimes be found in freshwater. With a maximum length of 11.5 centimetres (4.5 in), the smallest moray is likely the Snyder's moray (Anarchias leucurus), while the longest species, the slender giant moray (Strophidon sathete) reaches up to 4 metres (13 ft). The largest in terms of total mass is the giant moray (Gymnothorax javanicus), which reaches almost 3 metres (9.8 ft) and can weigh over 36 kilograms (79 lb).
The dorsal fin extends from just behind the head along the back and joins seamlessly with the caudal and anal fins. Most species lack pectoral and pelvic fins, adding to their serpentine appearance. Their eyes are rather small; morays rely on their highly developed sense of smell, lying in wait to ambush prey.
The body is generally patterned. Camouflage is also present inside the mouth. Their jaws are wide, framing a protruding snout. They possess large teeth, designed to tear flesh as opposed to holding or chewing.
Moray eels' heads are too narrow to create the negative pressure that most fish use to swallow prey. Quite possibly because of this, they have a second set of jaws in their throat called pharyngeal jaws, which also possess teeth. When feeding, morays launch these jaws into the mouth, where they grasp prey and transport it into the throat and digestive system. Moray eels are the only animal that uses pharyngeal jaws to actively capture and restrain prey. Larger morays are capable of seriously wounding humans.
The Morays are frequently thought of as particularly vicious or ill-tempered animals. In truth, morays hide from humans in crevices and would rather flee than fight. Morays are shy and secretive, and attack humans only in self-defense or mistaken identity. Most attacks stem from disruption of a moray's burrow (to which they do react strongly), but an increasing number also occur during hand-feeding of morays by divers, an activity often used by dive companies to attract tourists. Morays have poor vision and rely mostly on their acute sense of smell, making distinguishing between fingers and held food difficult; numerous divers have lost fingers while attempting hand feedings. For this reason the hand feeding of moray eels has been banned in some locations, including the Great Barrier Reef. The moray's rear-hooked teeth and primitive but strong bite mechanism also makes bites on humans more severe, as the eel cannot release its grip even in death and must be manually pried off. While the majority are not believed to be venomous, circumstantial evidence suggests that a few species may be.
