Pelagic fish
Pelagic fish live in the pelagic zone of ocean or lake waters – being neither close to the bottom nor near the shore – in contrast with demersal fish, which do live on or near the bottom, reef fish, which are associated with coral reefs. The marine pelagic environment is the largest aquatic habitat on Earth, occupying 1,370 million cubic kilometres, is the habitat for 11% of known fish species; the oceans have a mean depth of 4000 metres. About 98% of the total water volume is below 100 metres, 75% is below 1,000 metres. Marine pelagic fish can be divided into oceanic pelagic fish. Coastal fish inhabit the shallow and sunlit waters above the continental shelf, while oceanic fish inhabit the vast and deep waters beyond the continental shelf. Pelagic fish range in size from small coastal forage fish, such as herrings and sardines, to large apex predator oceanic fishes, such as bluefin tuna and oceanic sharks, they are agile swimmers with streamlined bodies, capable of sustained cruising on long-distance migrations.
Many pelagic fish swim in schools weighing hundreds of tonnes. Others are solitary, like the large ocean sunfish weighing over 500 kilograms, which sometimes drift passively with ocean currents, eating jellyfish. Epipelagic fish inhabit the epipelagic zone; the epipelagic zone is the water from the surface of the sea down to 200 metres. It is referred to as the surface waters or the sunlit zone, includes the photic zone; the photic zone is defined as the surface waters down to the point where the sunlight has attenuated to 1% of the surface value. This depth depends on how turbid the water is, but in clear water can extend to 200 metres, coinciding with the epipelagic zone; the photic zone has sufficient light for phytoplankton to photosynthese. The epipelagic zone is vast, is the home for most pelagic fish; the zone is well lit so visual predators can use their eyesight, is well mixed and oxygenated from wave action, can be a good habitat for algae to grow. However, it is an featureless habitat.
This lack of habitat diversity results in a lack of species diversity, so the zone supports less than 2% of the world's known fish species. Much of the zone lacks nutrients for supporting fish, so epipelagic fish tend to be found in coastal water above the continental shelves, where land runoff can provide nutrients, or in those parts of the ocean where upwelling moves nutrients into the area. Epipelagic fish can be broadly divided into small forage fish and larger predator fish which feed on them. Forage fish school and filter feed on plankton. Most epipelagic fish have streamlined bodies capable of sustained cruising on migrations. In general and forage fish share the same morphological features. Predator fish are fusiform with large mouths, smooth bodies, forked tails. Many use vision to prey on smaller fish, while others filter feed on plankton. Most epipelagic predator fish and their smaller prey fish are countershaded with silvery colours which reduce visibility by scattering incoming light.
The silvering is achieved with reflective fish scales. This can give an effect of transparency. At medium depths at sea, light comes from above, so a mirror oriented vertically makes animals such as fish invisible from the side. In the shallower epipelagic waters, the mirrors must reflect a mixture of wavelengths, the fish accordingly has crystal stacks with a range of different spacings. A further complication for fish with bodies that are rounded in cross-section is that the mirrors would be ineffective if laid flat on the skin, as they would fail to reflect horizontally; the overall mirror effect is achieved with all oriented vertically. Though the number of species is limited, epipelagic fishes are abundant. What they lack in diversity they make up in numbers. Forage fish occur in huge numbers, large fish that prey on them are sought after as premier food fish; as a group, epipelagic fishes form the most valuable fisheries in the world. Many forage fish are facultative predators that can pick individual copepods or fish larvae out of the water column, change to filter feeding on phytoplankton when energetically that gives better results.
Filter feeding fish use long fine gill rakers to strain small organisms from the water column. Some of the largest epipelagic fishes, such as the basking shark and whale shark, are filter feeders, so are some of the smallest, such as adult sprats and anchovies. Ocean waters that are exceptionally clear contain little food. Areas of high productivity tend to be somewhat turbid from plankton blooms; these attract the filter feeding plankton eaters. Tuna fishing tends to be optimum when water turbidity, measured by the maximum depth a secchi disc can be seen during a sunny day, is 15 to 35 metres. Epipelagic fish are fascinated with floating objects, they aggregate in considerable numbers around objects such as drifting flotsam, rafts and floating seaweed. The objects appear to provide a "visual stimulus in an optical void". Floating objects can offer refuge for juvenile fish from predators. An abundance of drifting seaweed or jellyfish can result in significant increases in the survival rates of some juvenile species.
Many coastal juveniles use seaweed for the shelter and the food, available from invertebrates and other fish associated with it. Drifting seaweed the pelagic Sargassum, provide a niche habitat with its own shelter and food, supports its own unique fauna, such as the sargassum fish. One study, off Florida, found 54 species from 23 families living in flotsam from Sargassum m
Benthos
Benthos is the community of organisms that live on, in, or near the seabed known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, down to the abyssal depths. Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column; the pressure difference can be significant. Because light is absorbed before it can reach deep ocean-water, the energy source for deep benthic ecosystems is organic matter from higher up in the water column that drifts down to the depths; this dead and decaying matter sustains the benthic food chain. The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος "depth of the sea". Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes and streams. There is a redundant synonym, benthon; the main food sources for the benthos are algae and organic runoff from land.
The depth of water and salinity, type of local substrate all affect what benthos is present. In coastal waters and other places where light reaches the bottom, benthic photosynthesizing diatoms can proliferate. Filter feeders, such as sponges and bivalves, dominate sandy bottoms. Deposit feeders, such as polychaetes, populate softer bottoms. Fish, such as dragonets, as well as sea stars, snails and crustaceans are important predators and scavengers. Benthic organisms, such as sea stars, clams, sea cucumbers, brittle stars and sea anemones, play an important role as a food source for fish, such as the California sheephead, humans, they are visible to the naked eye with the lower range of body size at 0.5 mm but larger than 3 mm. In the coastal water ecosystem, they include several species of organisms from different taxa including Porifera, Coelenterates, Crustaceans, Arthropods etc. Zoobenthos comprises the animals belonging to the benthos. Phytobenthos comprises the plants belonging to the benthos benthic diatoms and macroalgae.
Endobenthos lives buried, or burrowing in the sediment in the oxygenated top layer, e.g. a sea pen or a sand dollar. Epibenthos lives on e.g. like a sea cucumber or a sea snail crawling about. Hyperbenthos lives just above the sediment. Contrast the terms plankton and neuston. "Benthos". Encyclopædia Britannica. Ryan, Paddy "Benthic communities" Te Ara - the Encyclopædia of New Zealand, updated 21 September 2007. Yip and Madl, Pierre "Benthos" University of Salzburg. "Benthos"
Biomass (ecology)
The biomass is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, the mass of one or more species, or to community biomass, the mass of all species in the community, it can include plants or animals. The mass can be expressed as the total mass in the community. How biomass is measured depends on why it is being measured. Sometimes, the biomass is regarded as the natural mass of organisms in situ. For example, in a salmon fishery, the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water. In other contexts, biomass can be measured in terms of the dried organic mass, so only 30% of the actual weight might count, the rest being water. For other purposes, only biological tissues count, teeth and shells are excluded. In some applications, biomass is measured as the mass of organically bound carbon, present; the total live biomass on Earth is about 550–560 billion tonnes C, the total annual primary production of biomass is just over 100 billion tonnes C/yr.
The total live biomass of bacteria may be much less. The total number of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at ×1037, weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4×1012 tonnes of carbon. An ecological pyramid is a graphical representation that shows, for a given ecosystem, the relationship between biomass or biological productivity and trophic levels. A biomass pyramid shows the amount of biomass at each trophic level. A productivity pyramid shows the turn-over in biomass at each trophic level. An ecological pyramid provides a snapshot in time of an ecological community; the bottom of the pyramid represents the primary producers. The primary producers take energy from the environment in the form of sunlight or inorganic chemicals and use it to create energy-rich molecules such as carbohydrates; this mechanism is called primary production. The pyramid proceeds through the various trophic levels to the apex predators at the top.
When energy is transferred from one trophic level to the next only ten percent is used to build new biomass. The remaining ninety percent is dissipated as heat; this energy loss means that productivity pyramids are never inverted, limits food chains to about six levels. However, in oceans, biomass pyramids can be wholly or inverted, with more biomass at higher levels. Terrestrial biomass decreases markedly at each higher trophic level. Examples of terrestrial producers are grasses and shrubs; these have a much higher biomass than the animals that consume them, such as deer and insects. The level with the least biomass are the highest predators in the food chain, such as foxes and eagles. In a temperate grassland and other plants are the primary producers at the bottom of the pyramid. Come the primary consumers, such as grasshoppers and bison, followed by the secondary consumers, shrews and small cats; the tertiary consumers, large cats and wolves. The biomass pyramid decreases markedly at each higher level.
Ocean or marine biomass, in a reversal of terrestrial biomass, can increase at higher trophic levels. In the ocean, the food chain starts with phytoplankton, follows the course: Phytoplankton → zooplankton → predatory zooplankton → filter feeders → predatory fish Phytoplankton are the main primary producers at the bottom of the marine food chain. Phytoplankton use photosynthesis to convert inorganic carbon into protoplasm, they are consumed by microscopic animals called zooplankton. Zooplankton comprise the second level in the food chain, includes small crustaceans, such as copepods and krill, the larva of fish, squid and crabs. In turn, small zooplankton are consumed by both larger predatory zooplankters, such as krill, by forage fish, which are small, filter-feeding fish; this makes up the third level in the food chain. The fourth trophic level consists of predatory fish, marine mammals and seabirds that consume forage fish. Examples are swordfish and gannets. Apex predators, such as orcas, which can consume seals, shortfin mako sharks, which can consume swordfish, make up the fifth trophic level.
Baleen whales can consume zooplankton and krill directly, leading to a food chain with only three or four trophic levels. Marine environments can have inverted biomass pyramids. In particular, the biomass of consumers is larger than the biomass of primary producers; this happens because the ocean's primary producers are tiny phytoplankton that grow and reproduce so a small mass can have a fast rate of primary production. In contrast, terrestrial primary producers reproduce slowly. There is an exception with cyanobacteria. Marine cyanobacteria are the smallest known photosynthetic organisms. Prochlorococcus is the most plentiful species on Earth: a single millilitre of surface seawater may contain 100,000 cells or more. Worldwide, there are estimated to be several octillion individuals. Prochlorococcus is ubiquitous between 40°N and 40°S and dominates in the oligotrophic regions of the oceans; the bacterium accounts for an estimated 20% of the oxygen in the Earth's atmosphere, forms part of the base of the ocean food chain.
There are 50 million bacterial cells in
Aquatic mammal
Aquatic and semiaquatic mammals are a diverse group of mammals that dwell or in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter, they are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies among species. Among freshwater taxa, the Amazonian manatee and river dolphins are aquatic and dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests and breeds on land. Mammal adaptation to an aquatic lifestyle vary between species. River dolphins and manatees are both aquatic and therefore are tethered to a life in the water. Seals are semiaquatic. In contrast, many other aquatic mammals, such as hippopotamus and water shrews, are much less adapted to aquatic living, their diet ranges as well, anywhere from aquatic plants and leaves to small fish and crustaceans.
They play major roles in beavers especially. Aquatic mammals were the target for commercial industry, leading to a sharp decline in all populations of exploited species, such as beavers, their pelts, suited for conserving heat, were taken during the fur trade and made into coats and hats. Other aquatic mammals, such as the Indian rhinoceros, were targets for sport hunting and had a sharp population decline in the 1900s. After it was made illegal, many aquatic mammals became subject to poaching. Other than hunting, aquatic mammals can be killed as bycatch from fisheries, where they become entangled in fixed netting and drown or starve. Increased river traffic, most notably in the Yangtze river, causes collisions between fast ocean vessels and aquatic mammals, damming of rivers may land migratory aquatic mammals in unsuitable areas or destroy habitat upstream; the industrialization of rivers led to the extinction of the Chinese river dolphin, with the last confirmed sighting in 2004. This list covers only mammals.
For a list of saltwater mammals, see Marine mammal. Order Sirenia: sirenians Family Trichechidae: manatees Amazonian manatee African manatee Dwarf manatee validity questionable Order Cetartiodactyla: even-toed ungulates Suborder Whippomorpha Family Platanistidae South Asian river dolphin with two subspecies Ganges river dolphin, or susu Indus river dolphin, or bhulan Family Iniidae Amazon river dolphin, or boto Araguaian river dolphin Family Lipotidae Chinese river dolphin, or baiji functionally extinct since December 2006 Family Pontoporiidae La Plata dolphin, or franciscana Family Hippopotamidae: hippopotamuses Hippopotamus Pygmy hippopotamus Suborder Ruminantia Family Cervidae Moose Order Carnivora Family Mustelidae Subfamily Lutrinae Eurasian otter Hairy-nosed otter Spotted-necked otter Smooth-coated otter North American river otter Southern river otter Neotropical river otter Giant otter African clawless otter Oriental small-clawed otter Subfamily Mustelinae European mink American mink Family Phocidae Genus Pusa Baikal seal Ladoga seal Saimaa seal Order Rodentia: rodents Suborder Hystricomorpha Capybara Lesser capybara Coypu Family Castoridae: beavers North American beaver Eurasian beaver Family Cricetidae Muskrat European water vole Order Monotremata: monotremes Platypus Order Perissodactyla:odd-toed ungulates Family Rhinocerotidae: rhinoceroses Javan rhinoceros Indian rhinoceros Order Afrosoricida Giant otter shrew Order Soricomorpha Family Soricidae: shrews Malayan water shrew Himalayan water shrew Sunda water shrew Japanese water shrew Chinese water shrew Sumatran water shrew Elegant water shrew Mediterranean water shrew Eurasian water shrew Transcaucasian water shrew Glacier Bay water shrew American water shrew Pacific water shrew, or marsh shrew Family Talpidae Russian desman Order Didelphimorphia: opossums Family Didelphidae: opossums Lutrine opossum Yapok One of the first known proto-mammals similar to modern placentals was aquatic, the Jurassic therapsid Castorocauda.
It seems to have been adapted to water much like a beaver, with teeth different in many ways from all other docodonts due to a difference in diet. Most docodonts had teeth specialized for an omnivorous diet; the teeth of Castorocauda suggest that the animal wa
Aquatic insect
Aquatic insects or water insects live some portion of their life cycle in the water. They feed in the same ways as other insects; some diving insects, such as predatory diving beetles, can hunt for food underwater where land-living insects cannot compete. One problem that aquatic insects must overcome is. All animals require a source of oxygen to live. Insects draw air into their bodies through spiracles, holes found along the sides of the abdomen; these spiracles are connected to tracheal tubes. All aquatic insects have become adapted to their environment with the specialization of these structures Aquatic adaptationsSimple diffusion over a thin integument Temporary use of an air bubble Extraction of oxygen from water using a plastron or physical gill Storage of oxygen in hemoglobin molecules in hemolymph Taking oxygen from surface via breathing tubes The larvae and nymphs of mayflies and stoneflies possess tracheae but when in larval stage the tracheae are connected to gills, which are thin extensions of the exoskeleton through which oxygen in the water can diffuse.
Some insects have densely packed hairs around the spiracles that allow air to remain near, while keeping water away from, the body. The trachea open through spiracles into this air film. In many such cases, when the insect dives into the water, it carries a layer of air over parts of its surface, breathes using this trapped air bubble until it is depleted returns to the surface to repeat the process. Other types of insects have a plastron or physical gill that can be various combinations of hairs and undulations projecting from the cuticle, which hold a thin layer of air along the outer surface of the body. In these insects, the volume of the film is small enough, their respiration slow enough, that diffusion from the surrounding water is enough to replenish the oxygen in the pocket of air as fast as it is used; the large proportion of nitrogen in the air dissolves in water and maintains the gas volume, supporting oxygen diffusion. Insects of this type only need to replenish their supply of air.
Other aquatic insects can remain under water for long periods due to high concentrations of hemoglobin in their hemolymph circulating within their body. Hemoglobin bonds to oxygen molecules. A few insects such as water scorpions and mosquito larvae have breathing tubes with the opening surrounded by hydrofuge hairs, allowing them to breathe without having to leave the water. Collembola - springtails Ephemeroptera - mayflies Odonata - dragonflies and damselflies Plecoptera - stoneflies Megaloptera - alderflies and dobsonflies Neuroptera - lacewings Coleoptera - beetles Hemiptera - true bugs Hymenoptera - ants and wasps Diptera - flies and mosquitoes Mecoptera - scorpionflies Lepidoptera - moths Trichoptera - caddisflies Drees, B. M. and Jackman, J. "Diving Beetle" in Field Guide to Texas Insects, Gulf Publishing Company, Texas. Farb, P.. The Water Dwellers INSECTS pg. 142. Meyer, J. R. "Respiration in Aquatic Insects". Stanley, D. and Bedick, J.. "Respiration in aquatic insects". Wigglesworth, Vincent B.
Sir. The life of insects. Weidenfeld & Nicolson, London Insect stages - "Some larvae and adult insects that live in freshwater." A UK-based web site with microscopic photos of various insects and other microorganisms as well as biological information
Ocean
An ocean is a body of water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean; these are, in descending order by area, the Pacific, Indian and Arctic Oceans. The word "ocean" is used interchangeably with "sea" in American English. Speaking, a sea is a body of water or enclosed by land, though "the sea" refers to the oceans. Saline water covers 361,000,000 km2 and is customarily divided into several principal oceans and smaller seas, with the ocean covering 71% of Earth's surface and 90% of the Earth's biosphere; the ocean contains 97% of Earth's water, oceanographers have stated that less than 5% of the World Ocean has been explored. The total volume is 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the principal component of Earth's hydrosphere, it is integral to life, forms part of the carbon cycle, influences climate and weather patterns; the World Ocean is the habitat of 230,000 known species, but because much of it is unexplored, the number of species that exist in the ocean is much larger over two million.
The origin of Earth's oceans is unknown. Extraterrestrial oceans may be composed of water or other compounds; the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories and Venus are theorized to have had large water oceans; the Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of natural satellites; the Solar System's giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone.
Ocean planets are a hypothetical type of planet with a surface covered with liquid. The word ocean comes from the figure in classical antiquity, the elder of the Titans in classical Greek mythology, believed by the ancient Greeks and Romans to be the divine personification of the sea, an enormous river encircling the world; the concept of Ōkeanós has an Indo-European connection. Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases. Though described as several separate oceans, the global, interconnected body of salt water is sometimes referred to as the World Ocean or global ocean; the concept of a continuous body of water with free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, other criteria.
Oceans are fringed by smaller, adjoining bodies of water such as seas, bays and straits. The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system, part of every ocean and the longest mountain range in the world; the continuous mountain range is 65,000 km long. The total mass of the hydrosphere is about 1.4 quintillion metric tons, about 0.023% of Earth's total mass. Less than 3% is freshwater; the area of the World Ocean is about 361.9 million square kilometers, which covers about 70.9% of Earth's surface, its volume is 1.335 billion cubic kilometers. This can be thought of as a cube of water with an edge length of 1,101 kilometers, its average depth is about 3,688 meters, its maximum depth is 10,994 meters at the Mariana Trench. Nearly half of the world's marine waters are over 3,000 meters deep; the vast expanses of deep ocean cover about 66% of Earth's surface. This does not include seas not connected to the World Ocean, such as the Caspian Sea; the bluish ocean color is a composite of several contributing agents.
Prominent contributors include dissolved organic chlorophyll. Mariners and other seafarers have reported that the ocean emits a visible glow which extends for miles at night. In 2005, scientists announced that for the first time, they had obtained photographic evidence of this glow, it is most caused by bioluminescence. Oceanographers divide the ocean into different vertical zones defined by physical and biological conditions; the pelagic zone includes all open ocean regions, can be divided into further regions categorized by depth and light abundance. The photic zone includes the oceans from the surface to a depth of
Algal bloom
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, is recognized by the discoloration in the water from their pigments. Cyanobacteria were mistaken for algae in the past, so cyanobacterial blooms are sometimes called algal blooms. Blooms which can injure animals or the ecology are called "harmful algal blooms", can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. A bloom can block out the sunlight from other organisms, deplete oxygen levels in the water; some algae secrete poisons into the water. Since'algae' is a broad term including organisms of varying sizes, growth rates and nutrient requirements, there is no recognized threshold level as to what is defined as a bloom. For some species, algae can be considered to be blooming at concentrations reaching millions of cells per milliliter, while others form blooms of tens of thousands of cells per liter; the photosynthetic pigments in the algal cells determine the color of the algal bloom, are thus a greenish color, but they can be a wide variety of other colors such as yellow, brown or red, depending on the species of algae and the type of pigments contained therein.
Bright green blooms in freshwater systems are a result of cyanobacteria such as Microcystis. Blooms may consist of macroalgal species; these blooms are recognizable by large blades of algae. Of particular note are the rare harmful algal blooms, which are algal bloom events involving toxic or otherwise harmful phytoplankton such as dinoflagellates of the genus Alexandrium and Karenia, or diatoms of the genus Pseudo-nitzschia; such blooms take on a red or brown hue and are known colloquially as red tides. Freshwater algal blooms are the result of an excess of nutrients some phosphates; the excess of nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes. They may originate from household cleaning products containing phosphorus; these nutrients can enter watersheds through water runoff. Excess carbon and nitrogen have been suspected as causes. Presence of residual sodium carbonate acts as catalyst for the algae to bloom by providing dissolved carbon dioxide for enhanced photosynthesis in the presence of nutrients.
When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants. Algae tend to grow quickly under high nutrient availability, but each alga is short-lived, the result is a high concentration of dead organic matter which starts to decay; the decay process consumes dissolved oxygen in the water. Without sufficient dissolved oxygen in the water and plants may die off in large numbers. Use of an Olszewski tube can help combat these problems with hypolimnetic withdrawal. Blooms may be observed in freshwater aquariums when fish are overfed and excess nutrients are not absorbed by plants; these are harmful for fish, the situation can be corrected by changing the water in the tank and reducing the amount of food given. A harmful algal bloom is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. HABs are associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings.
In studies at the population level bloom coverage has been related to the risk of non-alcoholic liver disease death. In the marine environment, single-celled, plant-like organisms occur in the well-lit surface layer of any body of water; these organisms, referred to as phytoplankton or microalgae, form the base of the food web upon which nearly all other marine organisms depend. Of the 5000+ species of marine phytoplankton that exist worldwide, about 2% are known to be harmful or toxic. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, the mechanism by which they exert negative effects. Harmful algal blooms have been observed to cause adverse effects to a wide variety of aquatic organisms, most notably marine mammals, sea turtles and finfish; the impacts of HAB toxins on these groups can include harmful changes to their developmental, neurological, or reproductive capacities. The most conspicuous effects of HABs on marine wildlife are large-scale mortality events associated with toxin-producing blooms.
For example, a mass mortality event of 107 bottlenose dolphins occurred along the Florida panhandle in the spring of 2004 due to ingestion of contaminated menhaden with high levels of brevetoxin. Manatee mortalities have been attributed to brevetoxin but unlike dolphins, the main toxin vector was endemic seagrass species in which high concentrations of brevetoxins were detected and subsequently found as a main component of the stomach contents of manatees. Additional marine mammal species, like the endangered North Atlantic Right Whale, have been exposed to neurotoxins by preying on contaminated zooplankton. With the summertime habitat of this species overlapping with seasonal blooms of the toxic dinoflagellate Alexandrium fundyense, subsequent copepod grazing, foraging right whales will ingest large concentrations of these contaminated copepods. Ingestion of such contaminated prey can affect respiratory capabilities, feeding behavior, the reprod
