Travel, Science, Mountains and Oceans

>

Marine Species:

1. Plankton - drifting organisms

Size classification

2.3 Coccolithophores

Characteristics

·         Occur as single cells.

·         Covered by plates made of calcite (calcium carbonate) called coccoliths which make up some calcareous sediments on the sea floor.

·         Have 2 flagella.

·         Are smaller in size than most diatoms or dinoflagellates.

Habitat

·         Dominate in warm, low nutrient, low productivity waters of the oceans.

However, blooms occur in colder waters as well, e.g., Bering Sea since 1997, North Atlantic, Barents Sea

3. Bacterioplankton

The most abundant organisms in the ocean (1,000,000 per ml). Have the greatest “standing stock” of biomass in low-productivity regions of the ocean.

Characteristics

·         Very small (usually <1µm in diameter). Prokaryotes (lack nuclear membrane). Come in many shapes:

·         May be either free or attached to surfaces, including other organisms.

Habitat

·         Everywhere.

·         Cyanobacteria are more numerous than other primary producers where nutrient concentrations are very low, because they have the ability to fix nitrogen.

·         Heterotrophic bacteria are more numerous where there is a lot of organic material, i.e., areas of high primary productivity

Role

·         Primary producers or decomposers of organic matter and recyclers of nutrients.

·         “Blue-green algae” are actually prokaryotic organisms that are bacteria, not algae. They are photosynthetic (autotrophic) primary producers.

Heterotrophic bacteria are the main decomposers of the sea, and are responsible for most nutrient recycling and oxygen consumption in the oceans.

4. Summary

 (1) Plankton are drifting organisms at the mercy of the currents.

(2) There are 3major groups of plankton, phytoplankton, the main primary producers of the ocean; bacterioplankton, which can be either primary producers or decomposers; and zooplankton, which are animals.

(3) The four major groups of primary producers (autotrophs) in the ocean are:

diatoms, golden-brown algae with siliceous frustules that are commonest in cold, nutrient-rich water

coccolithophores, algae that are covered with small, calcareous plates (coccoliths) and are commonest in warm, tropical waters.

dinoflagellates, red or brown algae that usually have hard coverings of cellulose and are motile by means of a flagellum. They are commonest in summer and fall in the temperate zone of the oceans, and can cause PSP.

cyanobacteria (blue-green algae) are really bacteria that are photosynthetic primary producers, commonest in nutrient-depleted areas of the open ocean.

Zooplankton

Heterotrophs— consume organic matter rather than manufacturing it, as do autotrophs.

Zooplankton can be:

herbivores

carnivores (several levels)

detritus feeders

omnivores

Zooplankton, in addition to being much smaller than familiar land animals, have shorter generation times and grow more rapidly (in terms of % of body wt / day).

 1. Crustaceans- include shrimp, copepods, euphausiids (“krill”)

Characteristics: Copepods, euphausiids and shrimp superficially resemble one another. All have:

• exoskeletons of chitin
• jointed appendages
• 2 pair of antennae
• complex body structure, with well developed internal organs and sensory organs

Habitats: Ubiquitous.

• Euphausiids predominate in the Antarctic Ocean, but are common in most temperate and polar oceans.
• Copepods are found everywhere, but are less important in low-productivity areas of the ocean - the “central ocean gyres”. They are found at all depths but are more abundant near the surface.
• Role in food webs:
•  Euphausiids and copepods are filter-feeders. Copepods are usually herbivores, while the larger euphausiids consume both phytoplankton and other zooplankton.

Shrimp are usually carnivores or scavengers.

2. Chaetognaths - (“Arrow worms”)

Characteristics:

• 2-3 cm long
• wormlike, but non-segmented
• no appendages (legs or antennae)
• complex body structure with internal organs

Habitat: Ubiquitous

Role in food web: Carnivore feeding on small zooplankton such as copepods.

3. Protozoan - Include foraminifera, radiolarians, tintinnids and “microflagellates” ca. 0.002 mm

Characteristics:

• Single-celled animals.
• Forams have calcareous shell
• Radiolarians have siliceous shell.
• Both Forams and Radiolarians have spines.

Habitat: Ubiquitous

• Radiolarians are especially abundant in the Pacific equatorial upwelling region.
• Protozoa are especially important components of the food web in low-productivity ocean areas.
• Both are found in sediments as well as in the water column.

Role in food web: Feed on small phytoplankton, bacterioplankton, and other protozoans. They can be bacteriovores, herbivores, or carnivores.

4. Gelatinous Zooplankton: includes a variety of fragile, jelly-like organisms which are not closely related taxonomically.

Cnidarians: jellyfish

Characteristics:

Very simple body structure, with 3 layers: inner membrane, jelly,

• and outer membrane.
• No internal organs but have a digestive cavity.
• Have stinging cells on their tentacles called nematocysts.

Habitat: Found everywhere and at all depths. More abundant in surface waters.

Role in food web: Carnivores, trap prey in tentacles.

Ctenophores: “comb jellies”.

Characteristics:

• Also have a simple body structure without internal organs.
• Move by means of cilia,.
• Sometimes have 2 long tentacles.
• Are often bioluminescent.

Habitat: Found everywhere

Role in food web: Carnivores, predators.

Salps: A type of tunicate.

Characteristics:

• Members of the phylum Chordata.
• Have a complex body structure including internal organs and a nervous system as larvae but are “degenerate” as adults.
• May be solitary or colonial.

Habitat: Warm surface waters. Rare at high latitudes.

Role in food web: Largely feeds on phytoplankton. A “ciliary-mucous” filter feeder.

Overall: Gelatinous zooplankton are very important, but little-studied because of sampling problems; they often disintegrate in nets or other sampling devices.

5. Pteropods

 Characteristics:

• Mollusks related to snails.
• Small, ~ 1 cm long.
• May or may not have a conical shell.
• Move by means of “wings” (modified foot).

Habitat: Found everywhere

Role in food web: May be herbivores or carnivores. Filter-feed using a “mucous net”.

6. Meroplankton

Meroplankton are organisms which are part of the plankton for only part of their life cycle, usually an early, larval stage.

As adults the meroplankton are benthos (including intertidal organisms) or nekton.

The meroplankton often do not resemble the adult forms, to the extent that some were once thought to be separate species.

Meroplanktonic larvae promote survival of the species:

• Currents carry the offspring to new areas, especially important for sessile (immobile) benthic animals. Thus, the offspring do not compete with the parents for scarce resources such as food or space. Also, local “disasters” will not wipe out all close relatives.
• Meroplankton live in surface waters where food is abundant. Sometimes, the habitat of the adult would not have enough food, especially for a very small organism that could not effectively use the feeding strategy (for example, predation, filter feeding) of the adult.

Meroplanktonic larvae also have disadvantages:

• Often, reproduction occurs to coincide with the spring bloom and abundant food. If the spring bloom is not “on time”, meroplankton may starve.
• Meroplankton are food for the many predators on plankton.
• The currents may not carry the meroplankton to an area that provides suitable conditions for adults.

Therefore, organisms which have meroplanktonic larvae usually produce hundreds or thousands of eggs, so that a few will survive.

Nekton: swimmers

Taxonomic Classification of Nekton

1. Phylum Mollusca

a. Cephalopoda

·         squid

2. Phylum Chordata, Subphylum Vertebrata

a. Agnatha - jawless fishes

·         lampreys and hagfish

b. Chondrichthyes- jawed fishes with skeleton composed of cartilage

·         sharks

·         skates and rays

. Osteichthyes - jawed fishes with a bony skeleton

·         common fishes, such as salmon, herring, and halibut

d. Reptilia

·         sea snakes

·         sea turtles

e. Aves (birds)

·         Penguins

·         Seabirds capable of flight, such as murres, kittiwakes, puffins, etc. (Although some of these spend little time in the water, they are part of the marine food web.)

f. Mammalia

·         seals, sea lions, walrus

·         whales

·         sea otter

·         polar bears

·         manatees and dugongs

Of the taxonomic groups listed above, the most important globally are the bony and cartilagenous fishes and the squids. Other groups can be locally important predators, e.g., birds and mammals in the Arctic and Antarctic.

Nearly all nekton are carnivores (= meat eaters) and predators (organisms that kill and eat other animals). This lifestyle requires the rapid swimming that is characteristic of nekton. Adaptations related to swimming include:

• means of propulsion (fins, flippers, etc.)

streamlined shape. Nekton also generally have relatively (compared to most animals) highly developed nervous systems,

• with acute senses of sight, hearing, and/or smell, and are capable of complex behaviours.

However, a few nekton are filter feeders and scavengers are fairly common. Often predators will eat dead animals if available.

2. Fish

Cartilagenous Fish

Sharks: Most are predators. They have many abilities related to finding and capturing prey:

• strong, fast swimmers
• sharp, numerous, continuously replaced teeth
• very acute senses:
• eyesight
• hearing
• smell / taste, chemical sense
• mechanical sense
• electroreception

A few sharks (whale shark, basking shark) filter feed on zooplankton.

Rays and skates: most are predators also. They have many of the same sensory abilities as sharks, but are generally rather slow swimmers. They often feed on slow-moving or sessile (immobile) benthos. Manta rays are filter feeders on zooplankton.

Bony fish

Pelagic fish: live in the water column. They are often streamlined, swift swimmers, predators and carnivores.

examples: salmon, tuna, swordfish

Herring prey largely on zooplankton, as do many other small fishes. Anchovies are filter feeders on phytoplankton or zooplankton. There is a productive anchovy fishery in Peru upwelling region.

Demersal fish: Live on or near the bottom. Some have a flattened shape. They tend to be slower swimmers, since their prey is often slow or sessile.

examples: halibut, sole, cod, adult pollock.

Deep-sea fish: Predators, (scavengers opportunistically), carnivores. Deep-sea fish have adaptations to an environment where food is scarce.

• Light organs: Attract prey and mates
• Large eyes: (in mesopelagic only to see light given off by other organisms as well as residual sunlight
• Large, sharp teeth
• Large mouth, dislocatable jaw, stretchy body and gut, can eat prey larger than themselves

Small, thin body, low food needs

3. Squids

Squid are abundant in the ocean but hard to catch, and so population estimates are uncertain.

• Especially common in mesoplagic (200-1000 m depth)
• Swim by jet propulsion.
• Use tentacles to capture prey.
• All are carnivorous predators.

Have large eyes and highly developed nervous systems.

4. Reptiles

Sea snakes

• all are poisonous
• predators, carnivores
• live only in Pacific & Indian Oceans

Sea turtles -many endangered species

• Green- eats algae (herbivore)
• Hawksbill- eats sponges
• Loggerhead- eats sponges, crabs, mollusks
• Leatherback- eats jellyfish (endangered by plastic bags)

Other dangers:

• Fishing (drown in nets)
• Egg laying sites destroyed

Hunting, especially while laying eggs, or egg gathering.

5. Marine Mammals

1. Cetaceans: whales

All are nekton and carnivorous.

• Baleen whales feed on zooplankton (except the grey whale eats benthos). They are filter feeders, using their baleen to strain the plankton out of the water.
• Toothed whales usually feed on fish and squid. They are predators.

2. Pinnipeds: seals, sea lions and walrus

All are nekton, carnivores, and predators except the manatee and dugong, which are herbivores.

• Seals and sea lions usually eat fish or squid; some also eat large zooplankton such as krill or shrimp.
• Walrus eat benthic invertebrates such as clams. The tusks are not essential for feeding; rather, they are mainly for fighting with other walruses.

Mustelids

• Sea Otters are nekton, predators, and carnivores that feed on benthos.

Ursidae

• Polar Bears are predators and carnivores that eat seals. They are classified as marine mammals because they spend much of their lives on sea ice, and because they are part of the marine food web in the Arctic.

Seal Classification

Order Carnivora

Suborder Pinnipedia = “Feather feet”

Families:

Otariidae = eared seals

Phocidae = earless seals

Odobenidae = walrus

Pinniped characteristics:

• Pinnipeds are amphibious; they eat at sea, but must mate, give birth, and rear young on shore.
• Their sense organs function well either in or out of the water.
• They have 4 webbed flippers, a streamlined shape, and fur, but they are mainly insulated by blubber
• Many are capable of very deep dives, up to 4500 feet deep and 2 hours duration. To accomplish this they have special adaptations, including:
• High blood volume.
• Special blood chemistry to retain oxygen (a special haemoglobin)
• Tolerance to high levels of carbon dioxide and lactic acid in muscle and blood.
• Lungs and ribs are collapsible, to avoid damage at high pressure.

Earless Seals

• No external ears
• Short necks
• Short front flipper
• Hind flippers that do not fold under the body
• Poor agility on land
• Not usually sexually dimorphic (except elephant seal). That is, the male and female are about the same size.
• Young have only a brief dependence; may nurse for only one month.

Eared seals

• Visible but small ears
• Long necks
• Long front flippers
• Can pull hind flippers up under their bodies
• Fairly agile on land
• Sexually dimorphic; males are larger than females, and defend a “harem” of females during the mating season.
• Longer dependence of young; usually at least several months.

Walrus

• No visible ears
• Can use hind flippers to assist movement on land
• Very elongated canine teeth (tusks) in both sexes.

Earless seals include the elephant seal, ribbon seal, spotted seal, harbour seal, ringed seal, and bearded seal.

Eared seals include the California sea lion, the Northern fur seal, and the Steller sea lion.

Walrus are divided into Pacific and Atlantic walrus, but these two groups are very similar.

Cetaceans

Cetaceans are entirely aquatic mammals. Their body structure has undergone many evolutionary changes from that of the ancestral land mammals. The hind limbs are absent, fore limbs are adapted to flippers, and the tail has evolved into horizontal flukes. The skin is smooth and lacks fur or hair. Breathing is through a blowhole on the top of the head.

Suborders of Cetacea 

Characteristics of baleen whales

Right whale group, including the right and bowhead whales.

• Adults are up to 50-60 feet long and average bowhead weight is more than 75 tons.
• Long baleen (often more than 10 feet long)
• Massive head
• No dorsal fin
• Eat zooplankton predominantly, especially copepods and euphausids.
• Northern right whales (which got this name from whalers who considered them the “right” whale to kill) are critically endangered, with as few as 200 animals each surviving in the North Pacific and North Atlantic, perhaps below the minimum population for survival. Southern right whales are endangered but have a population of 3000-5000 animals.
• The bowhead whale is also endangered, with a population of about 7500 in western and northern Alaskan waters. It is hunted for subsistence use by Alaska Natives.

Rorquals include the blue whale (the largest animal ever to live on Earth), the fin whale, the sei whale, the minke whale, and the humpback whale.

• The largest group of whales (and animals) on earth, ranging from the Minke (adults average 27 feet long and 7 tons) to the blue (average adult 85 feet long and 100 tons).
• Short baleen, only 2 or 3 feet long.
• Ventral throat grooves that expand to allow intake of huge volumes of water.
• Small dorsal fin.
• Eat zooplankton and small, schooling fish (up to 4 tons/day for the blue whale).
• The blue whale has the lowest population, about 12,000 worldwide, and is the most endangered of this group. All species except the Minke are listed as Endangered.

Gray whales are a single species, with subpopulations in the western and eastern Pacific; the eastern population is larger. Gray whales were once found in the Atlantic, but are now extinct there.

• Average adults are 46 feet long and 33 tons.
• Short baleen, only about 6” long.
• No dorsal fin.
• Feed by dredging through mud, scooping mud and water into their mouths, and filtering out benthic amphipods and other small bottom animals.

Hunted to near-extinction in the 1930s, they are now considered Recovered

Characteristics of toothed whales:

Sperm whale

• The largest toothed whale at 50 feet and 40 tons.
• Huge, square head.
• Small dorsal fin.
• Deepest- and longest-diving cetacean, for up to 90 minutes and to depths of 10,000 feet.
• Eat squid, preferring giant squid, and fish.
• Worldwide population of about 1.5 million, but still listed as an Endangered species.

Beaked whales include the Cuvier’s, Baird’s, and Stejneger’s beaked whales. These whales are rarely observed, since they mostly remain in deep water and appear to avoid ships, so little is known about them.

• The Stejneger’s whale is smallest (16 feet long and 1.3 tons), the Baird’s whale the largest (34 feet, 10 tons).
• Beak similar to that of dolphins.
• Small dorsal fin.
• Probably eat mainly squid.
• The population is unknown. The Baird’s beaked whale is the only species deliberately hunted by man.

Dolphins include the orca (killer whale) and Pacific white-sided dolphin in Alaskan waters, and many other species worldwide.

• Most are small (7 feet, 300 pounds), but the female orca averages 23 feet and 4 tons, males 26 feet and 8 tons.
• Have a beak, relatively large dorsal fin (especially male orcas)
• Have a “melon”.
• Have conical teeth.

• Eat fish and squid; the orca also eats seals, sea lions, sea otters, and sometimes other whales.
• Not listed as Endangered. Sometimes killed in fishing nets.

Porpoises include the Dalls and harbour porpoises in Alaskan waters, many others worldwide.

• Dalls is 6 feet and 300 lbs., harbour 5 feet and 120 lbs.
• No beak, relatively large dorsal fin.
• Spade-shaped teeth.
• Eat fish and squid.
• Not Endangered. Sometimes killed in fishing nets.

Belukha, the white whale

• Averages about 12 feet long and 3000 lbs.
• Short beak and large “melon”. No dorsal fin.
• Conical teeth.
• Eat fish, squid, and probably anything else they can catch.

Not currently endangered, but the Cook Inlet population seems to have declined. Population estimated at 70,000 worldwide.

Echolocation

Many marine animals use sound to locate prey, to avoid obstructions, and to communicate. Echolocation is specifically the use of sound to locate objects, usually food. Echolocation is particularly well-developed in the toothed whales, but may be used by some baleen whales also. The sound is generated by the blowhole (often focused by the “melon”) and received by the jaw, thereby channeled to the middle ear.

Whaling and its Regulation

European whaling was recorded as early as 800-1000 A.D. Inuit and other native peoples hunted whales long ago. However, the focus of this lecture is on European, American, and Asian whaling of the 19^th and 20^th centuries, since the this whaling industry endangered many whale species.

Before 1867, all whaling was done with hand-held harpoons. It was a fairly even contest between man and whale.

In 1868 the harpoon gun was invented. But, whales could be hunted only close to shore, because they could not be butchered at sea.

By 1925 “factory” ships made it possible to process whales killed far from shore.

During the 1930s, several species, including the right, bowhead, and gray, were hunted nearly to extinction.

In 1946 the International Whaling Commission (IWC) was established and the gray, bowhead, and right whales were protected. However, whaling of other species continued. The IWC had little power to enforce regulations.

In 1962-63, the peak years of whaling, >60,000 whales were killed.

In 1972 the Marine Mammal Protection Act ended whaling in U.S. waters or by U.S. vessels.

In 1982 the IWC passed a moratorium on whaling that took effect in 1985-86, with some exceptions for “scientific” whaling by Japan, Norway, Iceland, the USSR, and Korea. Although the IWC ban continues, Japan and Norway currently harvest minke whales. The IWC also permits subsistence whaling for traditional uses by native peoples.

Gray Whales

Characteristics:

• Males average 14.5 m in length, females 15.5 m; they weigh about 33 tons.
• Gray whales are dark gray mottled with lighter gray, and lighter gray on the underside. They are often encrusted with barnacles and orange, parasitic whale lice.
• They are sexually mature at age 5-11 years.
• Female gray whales give birth every 2 years.
• They mate in November-December, while on their southward migration, and give birth the following year (13.5 mos. later).
• Calves are 5 meters long and weigh 1100 lbs. They nurse for 7-9 mos; the milk has 53% fat content.
• As with all great whales, the life span is not well known, but it may be 50 years or more.

Migration:

• Between summer feeding grounds in the northern Bering and Chukchi Seas and the warm lagoons along the Baja California coast where the females give birth. They reach the lagoons in January, and leave by March.
• The migration spans 50^o of latitude and >10,000 km.
• The gray whales swim slowly, at 1.5-3 knots on average and 6-8 knots maximum. The migration takes more than 2 months each way.
• They often travel close to shore and can be seen from land, or from small boats.
• They apparently do not eat substantial amounts while migrating, or in the Baja lagoons.

Feeding:

• Gray whales are benthic (bottom) feeders.
• They eat mainly amphipods (small crustaceans) that live in dense beds in sediments of the northern Bering and Chukchi Seas. They will also eat other benthos, but apparently prefer the amphipods because they grow in remarkably high densities and are consistently found in the same places each year.
• Gray whales eat by swimming on their side and sucking sediment and benthos into their mouths by pulling back their huge tongue.
• They expel sediment and water through the baleen while they trap the benthos in their baleen.
• The dimensions of one “suction mark” are 1-4 m long and 0.5-2 m wide and 15 cm deep. They make feeding excavations ca. 25 m in diameter. They eat about 1200 kg of food/day while feeding.
• Large areas of the N. Bering and Chukchi Sea floor are disturbed by this feeding activity each year.
• This feeding activity may have a major impact on that region’s benthic ecosystem, analogous to the impact of grazers on grasslands.

Human Impact:

• The pre-whaling population in the eastern Pacific is estimated at 20-25,000 individuals. There were an unknown number of gray whales in the western Pacific and Atlantic.
• They were relatively easy to hunt because they travel close to shore and swim slowly. Also, they were hunted in the lagoons where they gave birth, since females were reluctant to abandon the calves to escape. This lead to their rapid decimation after the harpoon gun was invented.
• Gray whales became extinct in the Atlantic in the 19^th century. The Pacific population was reduced to about 2000 animals by the 1920s.
• The gray whale was protected by international agreement in 1938.
• They population rebounded slowly at first; there were still only a few thousand animals in 1960.
• By the late 1980s, the gray whale had reached its pre-whaling population in the western Pacific. It was removed from the Endangered Species list in 1994.
• However, the western Pacific population never recovered and now numbers less than a few hundred whales; probably, this population will soon be extinct.
• The recovery of the gray whale resulted from effective protection in the eastern Pacific (including breeding areas) and the early sexual maturity and frequent calf production of this whale. Other great whales reproduce at a much lower rate.
• Also, the surviving animals congregated in a small area (northern Bering and Chukchi) each year. The widely dispersed populations of some other great whales make recovery more difficult.
• Humans continue to have some impact on this whale. Subsistence hunting is limited to about 140 animals (Alaska and Siberia).
• Of dead animals washed up on shore in California (excluding newborns), more than half were apparently killed by humans, either by entanglement in fishing gear or boat collisions.
• There is some concern about whale watchers disturbing the whales during migration, breeding, and birth and care of newborns. Most boats observe rules and keep their distance, some do not. Also, some whales approach boats and even move close enough to be touched.

The gray whale has successfully recovered from near-extinction. But, it remains vulnerable to harm by humans. Its reliance on two small, critical habitat areas (the amphipod beds and the coastal lagoons of Mexico and Central America) could lead to new problems for the species due to climate change, fishing, or coastal development.

Benthost

Benthos: organisms that live on the ocean bottom or within the sediments.

The benthos includes plants (in shallow water where there is enough light for plant growth), bacteria, and animals.

 1. Intertidal Zonation

The distribution of plants and animals in the intertidal zone (as well as other areas of the sea bottom) is controlled by variations in the physical environment, by competition among organisms for scarce resources, and by predation on animals (or herbivory on plants).

Physical Environment includes the following:

• Light intensity and wavelength is important for seaweeds and other plants.
• Ultraviolet light can damage intertidal organisms when they are exposed at high tide.
• Air exposure is important for animals and plants in the high intertidal zone. They must be able to withstand or prevent desiccation. One strategy is to have a fairly watertight shell.
• Temperature varies relatively little in water, much more in air. High intertidal organisms must be able to withstand temperature variations.
• Salinity variations can be due to rainfall or to freshwater drainage across the intertidal.
• Wave energy can rip attached organisms away from surfaces, and subject all organisms to mechanical stresses and abrasion (by suspended sediment).
• Bottom type, hard or soft (rock and gravel, or sand and mud).

Competition for scarce resources, including:

• Food, a factor everywhere but especially so in the deep sea where little food is available.
• Space, a factor mainly in the intertidal and very shallow water, where often all surfaces are occupied by plants or animals.

Predation on animals and herbivory on plants:

• Animal defenses against predation include shells, accumulation of noxious chemicals (often present in plants consumed as food), and living in high intertidal habitats where most predators can’t tolerate the physical conditions.
• Plant defences against herbivory also include a high content of indigestible material (e.g., calcium carbonate in the case of coralline red algae), noxious chemicals, and locations with physical conditions that grazers can tolerate.

 2. Benthic Plants

Benthic plant types:

• Single-celled algae that are similar to phytoplankton. In certain circumstances, phytoplankton themselves may grow on the bottom, also. (This sometimes happens following a bloom in shallow water.)
• These are found in shallow water where there is enough light for photosynthesis.
• They are found on any type of bottom, rock, sand, or mud.
• Macroalgae (seaweeds) are multicellular plants that are related to the single-celled algae. Unlike most land plants, they do not produce flowers or seeds, and they lack true leaves, stems, and roots. Also unlike land plants, different parts of the seaweed do not have markedly different types of cells with very different functions. Most of the cells in a seaweed are similar to one another.
• Grow only in shallow water (less than 200 m deep in most cases) where light is available for photosynthesis.
• Are more abundant in rocky intertidal zones and on rocky or gravel bottoms, since these provide anchors.
• Flowering plants that are very similar to land plants. These include eelgrass, turtle grass, cord grass (Spartina) and other sea grasses, and mangroves.
• Grow in shallow water, only (generally less than 1 m deep).
• Generally are restricted to water that is much less saline than average ocean water.

Seaweed types include green, brown, and red algae.

• These are named for their color, which is due to the accessory or extra pigments they have in addition to chlorophyll. (However, some species within these categories do not appear brown or red. Chlorophyll may mask the other pigments, so that they appear green, or they may have so much accessory pigment that they appear purple (reds) or almost black (browns).
• Because their pigments are better than chlorophyll for absorbing blue-green light, brown and red algae have more light energy available to them for photosynthesis in deeper water.
• Examples

Green: Sea lettuce (Ulva)

Dead man’s fingers (Codium)

Brown: Kelp (the largest seaweed)

Brown rockweed (Fucus)

Red: Corallina (found on coral reefs)

Porphyra

Seaweed parts:

• The holdfast anchors the plant to the bottom. It is not a root; it does not absorb water or nutrients as roots do.
• The stipe is the stem-like portion, but unlike true stems in land plants, it lacks specialized tissues for transporting water and nutrients.
• The blades are the leaf-like portions, but these too lack specialized transport tissues. These are not needed because the algae are immersed in water, and each cell has direct access to water, dissolved carbon dioxide, and dissolved nutrients. The blades of seaweeds are very thin to allow this direct access.

Seaweed importance:

• Seaweeds are major primary producers in many intertidal and shallow-water areas.
• Seaweeds provide shelter or sites for attachment for other algae and for a wide variety of animals.

Calcareous red algae help to build coral reefs and contribute to sediments and beach deposits.

3. Bacteria

As they are in the water column, bacteria are important decomposers of dead organic matter and recyclers of nutrients.

There are about 1 billion bacteria per each cubic centimeter of sediments.

4. Benthic Animals

Categories of benthic animals:

• Epifauna are animals that live on the surface of the ocean bottom. They live either on hard or soft bottoms.
• Soft bottoms consist of mud or sand.
• Hard bottoms consist of gravel, cobbles, or solid rock.
• Epifauna are usually filter feeders, surface grazers, scavengers, or predators.
• Infauna are animals that live in the bottom sediments. They can live only in soft bottoms.
• Infauna are often deposit feeders. Deposit feeders eat by ingesting the sediment, including large amounts of sand or mud, digesting the small proportion of organic material (1%-5%) and excreting the remainder. Infauna can also be predators or scavengers.

Major groups (phyla) of benthic animals:

Protozoans

• Single-celled, ameba-like animals related to the foraminifera and radiolarians and microflagellates of the zooplankton.
• Eat mainly bacteria (are bacteriovores) by engulfing the food to bring it within the cell.

Porifera (sponges)

• Very simple animals with no tissues or organs.
• Sponges are carnivores, filter feeders on (mainly) zooplankton.
• All adult sponges are sessile, that is, immobile and usually attached to a surface. Reproductive cells have flagella (can swim weakly) and are meroplankton.

Cnidaria (sea anemones and corals)

• The jellyfish of the zooplankton is also a member of this phylum.
• The body of cnidarians has 3 layers: outer “skin”, jelly or mesoglea, and inner lining of the digestive cavity.
• All Cnidaria are radially symmetrical and have tentacles with stinging cells called nematocysts.
• Most Cnidarians are carnivores and predators that feed on zooplankton.
• Some (especially the corals) are filter feeders that trap particles (zooplankton and detritus) on their tentacles with mucous.
• Corals also get some of their nutrition from symbiotic algae, called zooxanthellae, within their bodies.

Mollusks (clams, mussels, oysters, snails, slugs, octopuses)

• Related to the pteropods of the zooplankton.
• Typically have a muscular “foot”, a calcium carbonate shell, and a feeding organ called a radula. They have highly-developed tissues and organs.
• Gastropods are the snails.
• They have a well-developed head, twisted body, spiral shell, and flat foot used for creeping.
• The nudibranchs, or naked snails, lack a shell and have straight bodies.
• Almost all feeding types are found in the gastropods, including filter feeders, predatory carnivores, herbivores, scavengers and deposit feeders.
• Bivalves are the clams, oysters, and mussels.
• Bivalve shells have two, equal parts, joined by a hinge.
• The head is indistinct.
• Most mussels and oysters are sessile, growing attached to surfaces.
• Clams use their foot for digging rather than creeping.
• Most bivalves are filter feeders that trap particles on enlarged gills. A few are deposit feeders.
• Cephalopods are the octopuses.
• Octopuses are closely related to the squid and nautiluses of the nekton.
• Unlike other mollusks, they lack a shell.
• They have a well-developed head and nervous system, are are the most intelligent invertebrates.
• Their large, prehensile tentacles are for seizing prey. The tentacles are an evolutionary modification of the typical mollusk foot.
• All are carnivores and predators; some octopuses are scavengers, also.

Annelids are segmented worms, similar to earthworms.

• Annelid bodies are divided into a series of similar parts, but the head and tail sections do not have segments. Each segment has a pair of small appendages, with bristles (setae).
• They are round or oval in cross-section, not extremely thin and flat.
• Some annelids burrow through the mud (errant polychaetes) and are deposit feeders.
• Some annelids remain in tubes that they construct from secreted mucous that cements sediment particles together. These tube worms, such as the feather duster worm, are often filter feeders.

Arthropods include insects (rare in the ocean but common in lakes) and crustaceans (very numerous in the oceans).

• Arthropods have segmented bodies, outer shells of chitin, and jointed appendages.
• They have well-developed internal organs and complex nervous systems with large (for invertebrates) brains and elaborate sensory organs.
• Crustaceans are the major marine group of arthropods, including crabs, shrimps, lobsters, amphipods, and isopods.
• Crustaceans are related to the copepods and euphausiids of the plankton.
• They have 3 body parts, a head, thorax, and abdomen, two pair of antennae, and branched appendages (legs).
• The major groups include.
• Decapods (10 legs), the crabs, lobsters, and shrimp. Most are carnivores and predators, or scavengers.
• Isopods are oval, ca. 1 cm long, and flattened front to back, resembling pill bugs. Most are scavengers or deposit feeders.
• Amphipods are also about 1 cm long but are flattened side-to-side. They look shrimplike except that they usually have tiny eyes. Usually they are scavengers.
• Barnacles are sessile when adults, living within a shell shaped like a molar tooth that is attached to a surface. They are filter feeders on plankton and detritus particles in the water (omnivores).

Echinoderms include the sea stars (starfish), sea urchins, sand dollars, and sea cucumber.

• The larvae are bilaterally symmetrical, but the adults are radially symmetrical.
• The adults have a well-developed digestive tract, but other organ systems (e.g., reproductive, excretory, sensory, respiratory are relatively simple, compared with the arthropods, or absent.)
• All types have an internal or external skeleton of small ossicles, which sometimes fuse to form a solid shell (the sea urchins and sand dollars).
• A water-vascular system and tube feet for locomotion are also characteristic of this animal group.
• Types of echinoderms:
• Sea Stars (starfish) generally have 5 arms (or a multiple of 5 arms). They are predators and carnivores, often eating bivalve mollusks.
• Brittle stars and basket stars have 5 thin arms, which are highly branched in the case of the basket stars. This group includes scavengers, deposit feeders or filter feeders (especially the basket stars).
• Sea urchins, heart urchins and sand dollars are round and spiny, although the spines are small in the sand dollars, and the ossicles are fused into a rigid shell. Sea urchins are usually herbivores that graze by scraping off algae that grow on hard surfaces. Heart urchins are deposit feeders. Sand dollars are deposit or filter feeders.
• Sea cucumbers are sausage or cucumber-shaped animals, with small ossicles and thus relatively soft squishy bodies. They are deposit or filter feeders.
• Sea lilies and feather stars are the most ancient group of echinoderms, existing more than 300 million years ago. They most often have 10 arms, but may have 5 to >100. The feather stars can swim via a sinuous motion of their arms. They are filter feeders.

Chordates include the fishes (already discussed) and the tunicates (such as sea squirts).

• Chordates characteristically have a dorsal (back) nerve chord, bilateral symmetry, and well-developed organs including sensory organs. However, the tunicates have some of these characteristics only as larvae. They are related to the larvaceans and salps of the zooplankton.
• As adults, tunicates are sessile, and lack a complete dorsal nerve cord and bilateral symmetry. They have a tunic or fibrous outer coating. They are often colonial (an assemblage of many individual organisms).
• Adult tunicates do have a digestive tract, heart and circulatory system, and reproductive organs. They have a rudimentary brain, but no sensory organs.

Adult tunicates are filter feeders (ciliary mucous feeders), omnivores that trap and consume particles in the water.

5. Benthos Summary

 The kinds of plants and animals found in the intertidal zone or on/in the sea bottom are controlled by the physical environment, competition for scarce resources, and predation or herbivory.

The physical environment is highly variable in the intertidal, and often results in intertidal zonation, distinct plant and animal communities found in bands spanning narrow ranges of tidal height.

Competition for space is especially important in the intertidal, competition for food is crucial in most other areas of the sea floor. Predation is important in most areas, but is less in extreme environments like the high intertidal, and herbivory is important wherever plants can grow.

The kinds of plants and animals found in or on the bottom include:

• Bacteria :
• Plants:
• Vascular plants, only in brackish, shallow water.
• Seaweeds
• Green, red, and brown algae.
• Microalgae
• Most types found among the plankton, particularly diatoms.
• Animals:
• Protozoans like foraminiferans.
• Sponges.
• Cnidarians like sea anemones and corals.
• Annelids like the feather-duster worm.
• Crustaceans like crabs and amphipods.
• Mollusks like clams, snails, and octopuses.
• Echinoderms like sea stars, sea urchins, and sea cucumbers.
• Chordates like tunicates and fish.

Epifauna live on the bottom surface. They are often filter feeders or surface grazers. They are found on hard or soft bottoms.

Infauna live in the sediment of sandy and muddy bottoms. They are often deposit feeders, but also can be filter feeders. They are found in soft bottoms.

The major feeding strategies of benthos are:

• Filter feeding
• Deposit feeding
• Surface grazing
• Scavenging

Predation

Food Webs

1. Food webs and food chains are the feeding relationships among organisms in an ecosystem.

Food webs show more complex, but complete feeding relationships, for example see class notes or notes in the library.

The trophic level is the feeding level in a food web, e.g.,:

3^rd level carnivore (top predator)

2^nd level carnivore

1^st level carnivore

herbivore

primary producer (plant)

Trophic efficiency is the efficiency of energy transfer from one trophic level to the next.

E = (growth + reproduction)

food consumption

Productivity is the rate of production of biomass. Biomass is the weight of living organisms.

In the oceans (but not on land), the size of organisms tends to increase with increasing trophic level. The number of individuals and their total productivity decreases with increasing trophic level.

2. Controls on Primary Productivity

Since primary productivity is the basis of the entire food web, primary productivity is one important factor determining the productivity of higher trophic levels.

The two major factors controlling primary productivity (plant productivity) are the availability of:

Light and Nutrients

Nutrients are the main factor controlling the geographic differences in the amount of primary production in ocean surface waters.

• Nutrients are the chemical substances that a plant needs to grow in addition to carbon dioxide and water.
• They include phosphate and fixed nitrogen (usually ammonium or nitrate). They also include silica (for siliceous organisms only) and iron.

Light (or, rather, lack of light) limits primary production in waters beneath the photic zone (depths greater than 100-200 m) and in temperate and polar regions in winter.

The Nutrient Cycle

The nutrient cycle refers to the recycling of nitrogen, phosphorus, silica, and other substances that phytoplankton need in order to grow.

• Dead organic matter (dissolved or particulate) is broken down by bacteria, producing carbon dioxide and the nutrients ammonium, nitrate, and phosphate.
• If the nutrients are recycled in the photic zone, they are rapidly used again by the phytoplankton.
• Some organic matter sinks out of the photic zone and decomposes deeper in the ocean. This strips nutrients out of surface waters, and results in high nutrient concentrations in the aphotic zone.
• Nutrient resupply to the photic zone occurs when surface and deeper waters mix or when there is upwelling.

Geographic variations in nutrient availability:

• Oligotrophic ocean areas have low primary productivity. They are found in tropical ocean areas, away from land. This corresponds to the central regions of the major ocean gyres.
• At these latitudes (about 10^°-35^°) thermal stratification is fairly strong year-round. (Surface waters are warm year-round).
• This means that there is little vertical mixing of the water, so the supply of nutrients (fixed nitrogen and phosphate) from deep waters to surface waters is small.
• Fixed nitrogen and phosphate concentrations in the photic zone are extremely small.
• Since fixed nitrogen is usually depleted before phosphate, fixed nitrogen has been called the limiting nutrient for ocean primary productivity.
• However, nitrogen fixation by blue green algae can allow primary productivity where fixed nitrogen concentrations are very low.
• Iron concentrations are extremely low in seawater, less than 5 nanograms of iron per liter of water (1 nanogram = 0.000000001 g), and seem to limit the productivity of diatoms.
• Temperate and high-latitude ocean areas have medium levels of primary productivity.
• Seasonal cooling of the surface water leads to absence of stratification in winter.
• Vertical mixing of the water is strong and supplies nutrients to the surface water. But, phytoplankton are mixed too deeply to get enough light to grow.
• In spring, surface water warms and the water becomes stratified. Vertical mixing decreases, and phytoplankton get enough light to grow.
• Phytoplankton grow rapidly until the nutrients supplied by winter mixing are used up, a spring phytoplankton bloom.
• Primary productivity continues at a lower rate through the summer, largely using nutrients recycled from dead or eaten phytoplankton.
• Fall mixing, when the surface water cools, can cause another bloom until vertical mixing extends too deeply and light limitation prevents plant growth.
• The seasonal changes are similar in temperate and polar oceans, except that the productive season becomes shorter with increasing latitude.
• Areas of the ocean that have permanent ice cover (mainly the central Arctic) have very low productivity due to lack of light under the ice.

• Upwelling areas at tropical and temperate latitudes have very high primary productivity.
• Winds cause upwelling (a slow, upward flow) of water), which brings a continuous supply of nutrients to the ocean surface. In most upwelling areas, the winds very seasonally, and upwelling is strong only part of the year.
• At temperate and tropical latitudes, there is sufficient stratification of surface waters most or all of the year to keep phytoplankton in the photic zone.
• Since phytoplankton have both light and nutrients, they grow rapidly.
• Coastal areas at tropical and temperate latitudes often have high productivity.
• Nutrients are supplied by rivers and streams. Freshwaters usually have higher nutrient concentrations than ocean waters.
• Nutrients are also supplied from subsurface waters, because particles can’t sink to great depths before decomposing, as they can in the deep ocean areas

3. Fish Production

Fishery productivity is controlled by primary productivity and food web structure.

• Primary productivity is the basic food source for the food web.
• Primary productivity can be affected by weather and climate. For example, usually warm, calm summers can lead to lower productivity because of lower nutrient supply.
• The coupling of primary productivity to higher trophic levels is also important. Sometimes, spring phytoplankton blooms do not occur at the right time or place to supply food to newly-hatched zooplankton and meroplankton.
• Food web structure is important to fishery productivity in several ways, including:
• The trophic level of the fish, since there is about a 90% decrease in productivity with each trophic level.
• The competition for food at each trophic level. Only the fraction of the available food that leads directly to the fish will benefit fishery productivity.

• Benthic and demersal productivity correlates negatively with depth, because the greater the water depth, the more animals compete for the food on its way to the bottom. Nearly all commercial fisheries for benthos are in water less than 200 m deep.
• Humans also affect fishery productivity:
• Excessive removal of adults, leading directly to reduced populations or to reductions in spawners and thus reproduction.
• Commerical harvests, susbsistence harvests. By-catch (catch of non-target species, often discarded.
• Destruction or damage to habitat, e.g., by trawling or damming of spawning streams (for freshwater spawners)

• Pollution (eutrophication, toxins)
• Note that fishing does not necessarily lead to decreased fish populations, although, there are many examples of overfishing destroying fisheries.
• If food supply is limiting juvenile survival or adult growth, then removal of a limited number of adults is possible without harming the fishery.
• The quantity that can be removed without decreasing the resource is called “Maximum Sustainable Yield” or MSY.

The problem for fishery managers is that they have only the foggiest idea what the MSY is.

4. Summary

Primary productivity is controlled by the availablilty of light and nutrients.

Primary productivity is lowest in the central ocean gyres (equivalent to deserts on land in yield per acre), medium in temperate and subpolar oceans (comparable to grasslands or savanna on land), high in many coastal areas (comparable to wheat fields), and very high in upwelling areas (comparable to the most productive croplands, e.g., sugar cane or rice).

Fishery productivity is affected by primary productivity, food web structure, and human exploitation of fisheries.

Human Impacts on the Ocean: The Ocean’s Future

topics covered

Which human activities are changing the oceans and affecting marine life?

1. Fossil fuel burning

Increases atmospheric carbon dioxide concentrations, which will probably double over the next century.

• Substantial climatic warming over the next century is very likely.
• Sea level rise is very likely, due both to thermal expansion of seawater and to melting of glaciers, mainly those in Antarctica.

·         Sea level rise will flood low-lying coastal areas and increase coastal erosion and the damaging impact of hurricanes.

·         Some coastal ecosystems may not be able to adapt to the sea level rise, e.g., coral reefs, salt marshes, mangroves.

• Changes in precipitation and wind patterns are likely. Precipitation changes will affect land productivity; changes in winds and thermal stratification could affect ocean productivity.
• In addition to changes in total productivity, changes in community structure (the numbers and kinds of organisms present) are likely.
• For example, the 1970’s “regime shift” in Gulf of Alaska and Bering Sea waters, associated with a temperature increase of 1-2^o C, was reflected in major changes in fish and marine mammal populations.
• Large-scale changes in deep-ocean circulation are possible, with difficult-to-predict but potentially large changes in global climate. (Ocean circulation changes have been associated with past ice-age glaciations and deglaciations.)

Fossil fuel burning also introduces sulfur compounds into the atmosphere.

• This causes acid rain, which has little direct impact on the oceans because of their high acid neutralizing capacity. However, acid rain has severely damaged some lakes.
• Sulfate particles may increase clouds, decreasing warming due to carbon dioxide.

International agreements have been made to decrease rate of increase in burning of fossil fuels.

• The 1992 Global Climate Change Treaty (among 34 industrial nations) called for voluntary cutbacks in fossil fuel burning, to 1990 levels by the year 2000. This was ineffective.
• On Dec. 11, 1997 nations meeting in Kyoto, Japan agreed to mandatory cutbacks: 5-6% lower than 1990 levels by 2008-2012.
• The US has 5% of the world’s population, but burns 20% of total fossil fuel consumption. The top CO₂ producers, in millions of tons per year, are: US 1370; China 835; Russia 455; Japan 299; Germany 234. (Global total, about 7000.)
• Developing nations are exempt from controls at present.
• Industry has estimated that the treaty-mandated fossil fuel restrictions could:

·         Cost 1 million jobs in coal, oil, and chemical industries.

·         Increase gasoline prices $0.50/gallon.

·         Decrease the gross domestic product by 1.5% (relative to no-treaty 2010 level).

2. Eutrophication and harmful algal blooms

·         Eutrophication (excessive productivity of algae) is caused mainly by the use of artificial fertilizers.

• Fertilizer concentrations in major rivers have increased 3 to 10-fold over the past 40 years.
• Bottom waters of several coastal areas, including Chesapeake Bay, the continental shelf off the Mississippi River, and the Baltic Sea, have become anoxic.
• Excessive fertilizer inputs are likely also responsible, at least in part, for an increase in harmful algal blooms.
• HABs include toxic species (dinoflagellates, mainly) and species that harm fish by clogging their gills (Chaetoceros).
• In addition to fertilizer use, transport of harmful species in ballast water of ships and climate change have been cited as possible causes of the increase.
• Fish and shellfish farming probably both cause blooms and make their effects more obvious.
• There are very few records of HABs before the 1970s; however, it is not clear whether this reflects a true absence or simply a lack of record-keeping.

·         Controls on fertilizer use and sewage discharge have been very effective in developed countries (although clearly much more can be done.)

Third-world and developing nations usually cannot afford the capital costs of controlling eutrophication (although these can be cost-effective in the long run).

3. Overfishing

• Probably was largely responsible for the 1990s collapse of the North Atlantic fishery.
• Probably was an important contributor to the 1970s collapse of the Peruvian anchovy fishery.
• Probably was an important contributor to the 1980s collapse of the Alaskan king crab fishery.
• May be contributing to declines of marine mammals in the Bering Sea and Gulf of Alaska. (Or, the damage may already be done, e.g., 1960s-70s decline of Bering Sea herring stocks.)
• On the other hand, removal of whales from the Bering Sea may have increased production of pollock.
• Management of fisheries is very difficult.

·         Industry has fixed (and often increasing) costs due to capital investment in vessels. This results in pressure to maximize quotas.

·         Fishery managers have very limited ability to predict the productivity of a fishery in a given year.

·         Natural climatic (or other) variations can cause large (10-fold or more) fluctuations.

·         The maximum sustainable yield in one year, or decade, may not be the same as the MSY this year.

·         Managers can almost never make definite predictions about effects of fishing or overfishing. Vessel owners, on the other hand, can be absolutely sure they will be bankrupt if limits are too low.

Many fishes spend all or part of their life cycle in international waters, where restrictions (if any) are even more difficult to impose and enforce.

4. Toxic pollutants

• Severe local problems exist, mainly in bays and estuaries contaminated with organochlorines and metals.

o        In the US, this has resulted in the closure of fisheries (e.g., New Bedford Harbor, Boston Harbor).

o        In other countries, people are probably consuming toxic seafoods; deaths and permanent disability have resulted in the past. Worst well-documented example: Minimata, Japan methyl mercury poisoning.

o        Third-world and developing countries (and some industrial nations, e.g., Russia, former East Germany) often do not have adequate monitoring, environmental regulations, or enforcement.

• Effects of pollutants on marine organisms, and poisoning of humans, mainly occurs due to biomagnification.

o        Some organisms (mainly filter-feeding shellfish, carnivorous fishes, and marine mammals) can concentrate metals (usually organo-metallics such as methyl mercury) or organochlorines by 1,000,000 times or more relative to the water concentration.

o        This is a function of mode of feeding, trophic level, fat content, and life span.

• Toxic pollutants can be distributed far from their source through the atmosphere.

o        “Global distillation” (transfer from warm to cold climates) has led to rather high concentrations of PCBs, DDT, and other organochlorines in the Arctic and subarctic.

o        Also, marine mammals are especially large bioconcentrators, due to their high trophic level, high fat (blubber) content, and long lives.

o        Subsistence diets including whales and seals (especially blubber and oil) may expose people to undesirable levels of some toxic pollutants, although detrimental effects on health have not been demonstrated.

Most developed nations have already instituted fairly effective controls on the most toxic pollutants. Again, many under-developed and developing nations cannot afford to.

Often, the problem of controlling human impacts on the ocean

boils down to short-term, certain cost vs. long-term, less certain benefit.

Too often, short-term costs prevent effective controls

My Web Page Links:  Yahoo! My Personal Page: About Me The Mountains Origins of the Mountains and Oceans The Oceans of the World Oceans in a changing World The Oceans and Man Human Aciivity Foodwebs Marine Life Marine Species  Plankton Zooplankton Atlantic Cod The Benthos Necton Loggerhead Turtle Leatherback Turtle Orcinus Orca: The Killer Whale Cetaceans Sharks Fishing Methods  My Info: Name: Bas Email: [email protected]   Sign Guestbook View Guestbook options View Page Stats See who's visiting this page.