MSC 111 Chapter 10

ph and acidity in seawater

- 0 to 6.9 acidic - 7 neutral - 7.1 to 14 basic - more hydrogen ions make the ocean more acidic - less hydrogen ions make the ocean more basic or alkaline

Other adaptations to maintain a preferred depth

- A wide variety of organisms have the ability to secrete and store gas in their bodies to lower their overall density and increase their flotation. Some jellyfish-like organisms like the Portuguese man-of-war (Physalia physalis) are able to secrete gases into a float which enables them to stay at and drift along the sea surface (Figure 8A). Another strategy is employed by the chambered nautilus (Nautilus pompilius), a cephalopod relative of the squid, that adds chambers to its shell as it grows but occupies only the last chamber (Figure 8B). The earlier chambers are connected by a tube called a siphuncle that runs the interior length of the shell, allowing the nautilus to control its buoyancy by regulating the balance between seawater and gas (mainly nitrogen) in the shell chambers. - kelp: macroalgae that has a pneumatocyst which is a bunch of specialized gas bladders used to keep the upper portions of the algae afloat close to sunlit water

Organisms use color

- Camoflauge- blend in with environment, fish do this Transparency- organims blend in with their background; examples: Jellyfish and many of the small animals like ctenophores (comb jellies) and salps that float near the surface are often difficult to see until right upon them. -For other animals, especially fish, color can be used as camouflage, to attract mates, or to serve as a warning that sharp venomous spines, poisonous flesh or the capacity to inflict painful or even fatal stings await potential predators. In clear tropical waters where light penetrates deepest, bright colors play their most important role. Some coral reef fish conceal themselves by utilizing bright color bands and false eye spots. Stripes allow different parts of the body to blend into the background and break up the outline of the fish. A band across the face is also a common feature among fish, helping to minimize the contrast and hide the eye. - countershading: Among fish that swim near the surface in open water, dark backs and light undersides are common. This pattern, typical of fish as diverse as tuna, herring, mackerel and sharks, allows the fish to blend in with the darker waters at depth when seen from above, and with the better lit surface when seen from below. - bioluminescence: mesopelagic fish have rows of photophores on their bellies that produce blue light which exactly matches the faint sunlight from above, making the fish invisible to predators below them.

osmosis

- Charged ions like Na+ and Cl- are unable to pass through most biological membranes. However, water molecules are able to easily pass through cell membranes so salinity imbalances within biological systems are naturally corrected via the diffusion of water across the membranes to equalize salt concentrations on both sides of the membrane.

Inertia and viscosity

- inertia is the resistance to a change in velocity Inertia for large animals dominates over the water's viscosity, but for smaller organisms, the reverse is true and viscosity dominates over inertial forces.

Bacteria and breakdown rates relate to hydrostatic pressure

- In terms of deep sea ecology, it implies that organic material that sinks to the abyssal seafloor remains in place for long periods of time before bacterial degradation has run its course. This provides more opportunity for larger scavengers and detritus feeders to find that food before it decays away, allowing a greater biomass to be supported by the limited supply of food that sinks from the surface. - rates of bacterial respiration and the breakdown of organic compounds by bacteria are indeed strongly inhibited by high hydrostatic pressures.

Density of seawater

- density of seawater is more than 800 times that of air, allowing organisms to grow larger and for plankton to perpetually float - weight can be supported and things can float

Ectotherms

- internal temperature is regulated by the outside temperature - also known as poikilotherms - marine ectotherms have a low range of temperatures that they can tolerate

Reynolds number

- dimensionless quantity defined as the ratio of inertial forces to viscous forces that is often used to quantify the relative importance of these two types of forces for given flow conditions - Re = ρ V D / µ - where ρ is the density of the fluid, V is the velocity of an object moving through it, D is the diameter or length of the object (basically its shape), and µ is the fluid's viscosity. A Reynolds number >1 indicates that inertial forces dominate over viscous forces, while a number <1 indicates that viscous forces dominate over inertial forces.

turbulent flow

- fluid flow in which the velocity varies in magnitude and direction - flow around moving organisms that have a Reynolds number less than 1 - plankton, bacteria, larvae, sperm

Temperatures and metabolic rates

- higher temperatures speed up metabolisms - as a result, organisms that live in warmer water grow faster, reach sexual maturity faster, and live shorter lives - they live shorter lives because oxygen is less soluble in warmer waters - The maximum temperatures that adult fish can tolerate vary with the species of fish, prior acclimatization, oxygen availability and the synergistic effects of other pollutants whose toxicity can also be temperature related. - very high temperature causes death

Oxygen minimum zone

- OMZ usually coincides with the pycnocline layer, the interval of the water column where there is a sharp density gradient that slows the sinking of organic detritus from the surface. Organisms of all kinds are attracted to the pycnocline layer because of the ample food supply, and as they respire, they deplete the oxygen content of the water. In addition, bacteria further reduce the O2 content of the water as they work to decompose the sinking organic matter. - By the time one reaches 1000 meters depth, 80-90% of the downward flux of organic matter has typically been consumed or remineralized. The high demand for oxygen created by animals and bacteria, combined with the low rate of O2 replenishment by mixing because of the stable water column, produces the oxygen minimum layer and creates an interval of the ocean at intermediate depths where low O2 levels can restrict the presence of larger animals.

temperature

- When sunlight is absorbed by water molecules at the sea surface, it is converted to heat energy and the motion of the water molecules increases. Temperature is the way we describe these changes in molecular motion and is a universal factor governing the existence and behavior of living organisms. - animals survive at an optimal temperature (not above the boiling point or below the freezing point) - metabolic processes of organims work better at warmer temperatures

Bioluminescence

- a chemical reaction in which organisms produce their own light, without using heat - mostly blue or green since those colors travel the farthest - because of this, organims at this depth can no longer see red

Q10 temperature coefficient

- a measure of how an increase of temperature by 10°C affects the rate of change of a particular biological or chemical system - For example, a doubling of the rate of a process with a 10°C warming yields a Q10 value of 2. For most biological systems, the Q10 value typically ranges between about 2 and 3.

Deep sea scattering layer

- an interruption in the sonar (Diffuse echoes from mid-depths in the ocean were observed that were sometimes mistaken for the seabed) - made the seabed seem to move up and down - During daylight, echoes were observed from roughly horizontal layers near a depth of about 400 m. With nightfall, the observed echoes indicated that whatever was causing them rose toward the sea surface and spread over a greater depth range. - millions of marine organisms with gas filled swim bladders (sonar disruption) went to shallow depths during the night to feed on plankton and then start going back to depths, to hide from predators, at dawn

Some ectothermic fish can regulate their body temperature

- are able to conserve heat in their swimming muscles and thus elevate their body temperatures. Because their muscles work more efficiently at higher temperatures, these fish are able to swim rapidly and cruise for long distances, making them efficient predators. Fish in this category include some tuna and billfish as well as certain sharks. In addition to a streamlined body form adapted to fast swimming, a number of physiological strategies are employed to help elevate internal temperatures. Swordfish, for example, possess special tissues rich in mitochrondria and cytochrome-c that generate heat for the animal's eye and brain. These heating elements keep the swordfish eye and brain significantly warmer than the surrounding water and keep these organs warm and thus more effective during deep dives into the cold ocean depths to search for prey. The bluefin tuna (Thunnus thynnus) is another well-studied example of a fish that has consistently high red muscle temperatures regardless of external water temperatures (Figure 4). Nearly 75% of the total body weight of a tuna is composed of swimming muscles with segregated masses of red and white muscle fibers and a higher proportion of red muscle than most other fish. Red muscle fibers are rich in myoglobin which has a strong chemical affinity for oxygen and hence a higher metabolic rate and power output. Large tuna also have what is known as a rete mirabile ("wonderful network"), a complex of arteries and veins lying very close to each other that maintains body temperatures above those of seawater by passing arterial blood through vascular countercurrent heat exchangers. The tuna is thus able to thermoregulate certain areas of their body. Additionally, this increase in temperature leads to an increase in basal metabolic temperature. The fish is now able to split ATP at a higher rate and ultimately can swim faster.

ocean acidification

- as carbon uptake by the ocean increases due more carbon being placed in the atmosphere, there are more hydrogen ions in the ocean and a decrease in ph - it is corrosive to calcium carbonate shells - it can erode reefs and kill reef builders

light in the aphotic zone

- bioluminescence

endotherms

- birds and mammals - can regulate their body temperature and can tolerate a wider variety of temperatures - expend more energy that ectotherms to keep themselves warm - often have a layer of insulation, making them heavier and causing them to expend more energy - have a larger number of mitochondria per cell than ectotherms that enables them to generate heat by increasing the rate at which they metabolize fats and sugars. - also known as homeotherms

Loriciferans

- can live in anoxic zones (bacteria and viruses can too) - The basins in which they were found contain salt-saturated brines that because of their high density do not mix with the waters above. As a consequence, the environment in which these animals live is completely anoxic and, due to the activity of sulfate reducers, contains hydrogen sulfide at concentrations that are normally toxic to metazoans. The researchers subsequently identified an adaptation that helps these Loriciferans survive in such an extreme environment. Instead of mitochondria, which rely on oxygen, the creatures have organelles that resemble hydrogenosomes, which some single-celled organisms use to produce energy-storing molecules anaerobically

Buffer system

- carbonic acid- bicarbonate carbonate system CO2 (aq) + H2O ↔ H2CO3 ↔ H+ + HCO3− ↔ 2 H+ + CO32− - Many marine organisms - such as coral, clams, mussels, sea urchins, barnacles, and the calcareous forms of microscopic plankton - rely on equilibrated chemical conditions and pH levels in the ocean to build their calcium carbonate -based shells and other structures.

Vampire squid

- deep-sea cephalopod that resides in the heart of the oxygen minimum zone at depths from 600 to 900 meters - can breathe and live normally at oxygen saturation levels as low as 3% (gills with an especially large surface area, a lowest metabolic rate to body mass of all cephalopods, and their blue blood's hemocyanin binds and transports oxygen more efficiently than other cephalopods)

Seawater can hold a lot of carbon dioxide

- it does not stay as a gas - CO2 combines with water to produce a weak acid, carbonic acid (H2CO3), which typically dissociates to form a hydrogen ion (H+) and a bicarbonate ion (HCO3−), or two H+ ions and a carbonate ion (CO32−)

osmoconformers

- keep their osmopolarity uniform with the surrounding environment - osmoconformers are marine invertebrates such as echinoderms, mussels, marine crabs, lobsters, jellyfish, and scallops. - euryhaline: can tolerate a wide range of salinities; mussel can do this since they can close their shell to avoid harsh external environments - stenohaline: can tolerate a very narrow range of salinities; echnoderms

Catadromous

- migrate from freshwater to seawater to reproduce - freshwater American and European eels which as adults make their way from freshwater rivers to their spawning grounds in the Sargasso Sea

Oxygen levels at the ocean's surface

- oxygen is most abundant at the surface waters since it is mixed and diffused across the air sea interface and it is a byprouct of photosynthesis

ocean zones

- pelagic: open ocean (where animals swim) - benthic: sea floor (where organisms crawl)

Gas filled swim bladders

- plays a role in buoyancy - two sacs with a flexible layer - located on the dorsal fin to keep the fish upright - used to maintain neutral buoyancy - used to deal with pressure changes: Fish at greater depths, and therefore higher pressure, must increase the amount of gas in their swim bladders in order not to be crushed by the pressure. - Some fish with swim bladders fill them by either gulping air at the surface while others release gas from their blood through a gas gland to the bladder.

hydrostatic pressure

- pressure exerted by gravity and upper water layers in the ocean - In the ocean, pressure works the same way, but instead of just having a column of air above you, you also have the weight of all the water on top of you, and water is much heavier than air. - For every 10 meters you descend below the surface, the pressure increases by one atmosphere.

organisms adapting to high pressure

- some organisms have water filled cavities (since water is incompressible) and small skeletal structures (movemement is impeded and they sit and wait for food) - Pressure decreases the fluidity of membranes as the molecules are crammed together. To compensate for this, deep-sea organisms have a greater proportion of unsaturated fatty acids, which enhance membrane fluidity, than shallow-water organisms. - proteins do not function at high pressure--have piezolytes: small organic molecules recently discovered that bind tightly to water molecules, which gives the proteins more space and stops water from being forced into the proteins' interiors and damaging them. - trimethylamine oxide (TMAO), a molecule that gives rise to the fishy smell of marine fish and shrimp. TMAO is found at low levels in shallow marine fish and shrimp that humans routinely eat, but TMAO levels increase linearly with depth and pressure in species with wider depth ranges.

Factors than can affect the amount of light

- the angle at which the sun's rays hit the ocean: when the rays hit the water from a lower angle, less light penetrates, and when the rays hit from a higher angle, more light penetrates - the more suspended particles and matter in the water, the less light will penetrate.

Ocean temperature distribution and marine life

- the equator has the warmest surface waters and toward the poles the surface water gets progressively colder - the equator and the poles do not vary much in temperature - the water at the mid-latitudes vary in temperature - deep waters vary between -1 to 4 degrees C - sunlit waters and deep waters vary greatly in temperature, except in polar latitudes - marine organims adapt to the cold water by having "loose" flexible proteins and unsaturated membranes which do not stiffen up in the cold

Barotrauma

- the trauma a fish experiences when it ascends too fast and cannot adjust to the pressure change - gas expansion in bladder

Fishes without gas filled swim bladders

- two groups - swim constantly and use their fins to maintain position (such as mackerel, some tuna, and sharks) and bottom-dwelling fish (including the cartilaginous rays).

pelagic

- two zones of the pelagic neritic: the waters over the continental shelf oceanic system: or zone in deeper water beyond the edge of the shelf. photic (epipelagic): where sunlight reaches aphotic: sunlight does not reach bathyal: between 1,000 to 4, 000 meters abyssal: between 4, 000 to 6,000 meters hadal: great depth of sea trenches- below 6,000 meters to about 11,000 meters - the bathyal, abyssal and hadal are in the aphotic zone

isotonic

- when separated by the semi-permeable membranes around cells, the internal fluids and seawater have equal concentrations of solutes and water - bottom dwelling organisms like sea cucumbers, sponges, sharks, rays

hypotonic

- when the salt concentration in the cells is greater than salt concentration of the water the organism is in - water from the outside will diffuse into the cells and the cells will swell and burst if the organism does not have a way of removing that water

hypertonic

- when the salt concentration in the cells is less than salt concentration of the water the organism is in - water from the inside of the cells will diffuse into the surrounding water and the cells will dehydrate - effort to decrease outside salinity

isolated basins that have anoxic zones

Dead Sea: Connected to the Mediterranean through the Bosphorus and Dardanelles Straits, the Black Sea is supplied with freshwater by a number of major rivers, such as the Danube, Dnieper, and Rioni. The input from these and other rivers lowers the salinity near the surface and makes the surface waters less dense. These waters flow out through the Straits into the Aegean and Mediterranean and are replaced by warmer, more saline, and hence denser, waters that enter the Black Sea through the Straits at depth. The strong halocline that results because of the contrasting salinities prevents mixing of oxygen downwards into the deep Black Sea basin. If the oxygen demand exceeds the oxygen supply, then anoxic conditions result; this is the case for the Black Sea. Other well studied basins with anoxic or very low O2 levels include the Cariaco Basin off the northern coast of Venezuela, the Santa Barbara Basin off southern California, and Saanich Inlet, located off the southern coast of Vancouver Island.

Why dissolved oxygen increases below the OMZ

Recall from Chapter 8 that the deep and bottom waters in the ocean today generally originate from sinking of cold, dense surface waters in the polar seas. These so-called thermohaline currents travel at depth around the globe as part of the large-scale overturning circulation, and oxygen remains sufficient for life at most locations because there is not enough biomass in the deep sea to use it all up.

Examples of bioluminescence

Scientists believe that bioluminescence serves multiple functions, but not all used by any one species. Lanternfish, such as the specimen of Diaphus you will see here, have light-producing photophores along their ventral surface (belly) and a forward facing nasal light organ that acts as a headlight. Unique light patterns can serve as a social signal for attracting mates or as lures to attract curious prey, such as the dangling "fishing lures" of anglerfish as can be seen here. Some squid generate bright flashes to confuse or stun their prey, while the aptly named Green Bomber Worm (Swima bombaviridis) utilizes bioluminescence as a decoy and ejects glowing green blobs in order to divert attention from itself (see the short video here to see these worms in action).

why marine mammals (whales) can deep dive even though they have lungs

These animals have a physiology that permits their blood to absorb more oxygen and tolerate higher build-ups of carbon dioxide than land mammals. They also have a vascular shunt system that preferentially directs blood flow through only the brain and heart when underwater. During deep dives, their lungs collapse completely, forcing the air out and minimizing the amount of compressed gases absorbed by the blood at high pressure. This allows them to resurface quickly without suffering from the "bends" that a human diver would experience if stops to decompress were not built into their dive plan.

Sharks and rays are osmoconformers

These fish maintain a high concentration of urea in their tissues which helps maintain osmotic balance by allowing their tissues to retain water, thus preventing the movement of salt into their bodies and keeping the salt content of their body fluids at approximately the same salt concentration as seawater. Urea is readily produced but high concentrations will disrupt peptide bonds and lead to breakdown of proteins. For this reason, sharks and rays also have high concentrations of TMAO (yes, the same molecule referred to earlier that gives fish their fishy smell) which helps stabilize proteins at high urea levels. After death, the urea in a shark's body converts rapidly to ammonia giving dead sharks a particularly unpleasant smell.

benthic

animals in this zone are benthos - two zones intertidal: where the sea meets the land- it is between the high tide and low tide marks subtidal: from the continental shelf below the low tide mark to the deepest parts of the sea (Bathyal, abyssal, hadal)

nekton

aquatic animals that swim independently of the currents.

light in the disphotic zone

below the euphotic zone, there is a faint amount of blue light (all other light has been absorbed)

chromatophore

cell containing pigment, that through contraction and expansion can produce temporary colors

How marine and fresh water fish osmoregulate themselves

freshwater fish (hyptonic)- Fish that live in freshwater must deal with the problem of preventing excessive amounts of water from entering their more saline bodies. They do so by actively taking up salt from the environment through their gills by the use of special mitochondria-rich cells, and by excreting large quantities of hypotonic (dilute) urine to expel all the excess water. saltwater fish (hypertonic)- nternal osmotic concentration lower than that of the surrounding seawater, so it tends to lose water and gain salt. It adapts to this by actively excreting salt out from the gills, by producing low quantities of urine, and also by drinking water as it swims, something freshwater fish don't need to do.

biotic factors

living organims that affect the life processes of organims living there

Anadromous

organism that migrate from saltwater to freshwater to spawn - have the ability to adapt to changes in salinity - salmon: spawn in freshwater but swim down the rivers as juveniles to live their adult lives in the open sea. After several years (variable depending on the species), the salmon return to their home streams to lay their eggs and die. The body fluid of a salmon has a salinity of about 18‰ so once it migrates to the ocean its body tends to dehydrate and the salmon constantly drinks seawater and excretes the salt through its gills so the fish can replace its lost water. When salmon return to freshwater to reproduce, their cells take on water and the salmon stops drinking and its kidneys begin to produce large amounts of urine. - shad and striped bass

Chlorophyll

organisms not only need light, but the quality of the light matters as well - chlorophyll is a green pigment that best absorbs red and blue wavelengths - Since very little red light penetrates deeper than about 10 meters, phytoplankton such as diatoms stay near the surface to absorb the longer red wavelengths. Cyanobacteria, on the other hand, are better adapted to absorb blue light for photosynthesis and hence can live somewhat deeper in the water column.

Osmoregulators

organisms that actively control salt concentrations in their body despite the external environment - most bony fish, however they are usually stenohaline and are restricted to either freshwater or saltwater

abiotic factors

physical factors - temperature, these include light availability, oxygen levels, pressure, salinity, density and pH.

hemocyanin

protein that binds and transports oxygen throughout the body

laminar flow

relaxed flow, without strong current and minimizes drag and the expenditure of energy - desired flow for organisms with streamlined shapes (larger marine organisms) - flow around moving organisms that have a Reynolds number greater than 1

compensation depth

the depth at which photosynthesis equals respiration - At this point, the uptake of carbon dioxide through photosynthetic pathways is exactly matched by the respiratory release of carbon dioxide, and the uptake of O2 by respiration is exactly matched to the photosynthetic release of oxygen. The compensation depth usually corresponds to the depth to which about 1 percent of the surface light penetrates and by definition marks the base of the euphotic zone.

Difference between the photic zone and the euphotic zone

the photic zone is where light penetrates, the euphotic zone is where enough light is available for photosynthesis

Most plankton are denser than the water they live in

the plankton are denser than the water they live in which makes it harder from them to float, causing them to expend more energy - especially true in warmer waters - they adapt to this by increasing their surface area (maintain their position in the water column by increasing the frictional drag with the surrounding water), sometimes by adding appendages Globigerinoides: Note the long, delicate spines of this shallow-dwelling tropical species as well as the tiny yellowish-green particles visible along the spines or dispersed around the central shell. The latter are symbiotic dinoflagellates known as zooxanthellae that live within the foraminifer's cytoplasm. As the zooxanthellae require sunlight to photosynthesize, this particular species of foraminifer is restricted to spending its life in the sunlit shallow euphotic zone.

Viscosity

the thickness or resistance of a fluid that allows an organism to swim - more viscous in colder water, less viscous in warmer water - When large organisms such as fish, dolphins and whales swim through a sea of water molecules, the water molecules are proportionately much smaller than the organisms and exert significantly less resistance than that exerted on a smaller organism swimming through the same fluid. For very small organisms, the surrounding water molecules are proportionately very large and make locomotion through the water more difficult.

Best camoflague

those organisms that can change color rapidly - This includes fish such as flounder and cephalopods including octopus, cuttlefish, and squid. Cuttlefish are especially well known for their ability to rapidly blend in with their surroundings. - with more chromatophores, organisms can rapidly change colors

buoyancy

upward force that causes things to float - it supports marine organims - It helps keep floating organisms near the surface, reduces the amount of energy used by swimming organisms, and helps support the bodies of many bottom-dwelling organisms.