Lecture 7

Question 1

Describe Limnology and Oceanography

Answer 1

Limnologists work with the physical and chemical properties of freshwater and freshwater organisms, while oceanographers deal with the marine sciences known as geological, physical, chemical, biological and fisheries oceanography.

Question 2

The arctic ocean is considered as a part of the _______ seA

Answer 2

The Arctic Ocean is not considered one of the world’s oceans. Rather, it is considered part of a mediterranean sea enclosed between the North American and Eurasian continents. Many oceanographers call it the Arctic Mediterranean.

Question 3

Describe the physical properties of water: H2O

Answer 3

The water molecule, H2O, consists of two hydrogen (H) atoms and one oxygen (O) atom held together by strong chemical bonding caused by the negative charge of the oxygen atom and the positive charge of the hydrogen atom. The hydrogen atoms form an angle of 104.5o on either side of the oxygen atom (Figure 7-2) giving the molecule a negatively charged side and a positively charged side. This polarity allows water molecules to attract each other. The positive (hydrogen) side of one molecule attracts the negative (oxygen) side of another molecule. Bonding between water molecules is known as hydrogen bonding.

Question 4

hydrogen bonding

Answer 4

Bonding between water molecules is known as

Question 5

Latent heat of melting: define and provide calories of heat needed

Answer 5

The quantity of heat required to transform snow and ice into liquid water is known as the latent heat of melting and consumes 80 calories (375 Joules) of heat per gram of ice. Some hydrogen bonds break when heat is supplied and this causes the ice to melt. Adding more heat increases the number of broken hydrogen bonds until at 4oC freshwater attains its maximum density.

Question 6

Latent heat of vaporization: define and provide calories of heat needed

Answer 6

The quantity of heat required to transform liquid water into water vapour is known as the latent heat of vaporization and consumes 540 calories (2259 Joules) of heat per gram of water. Water becomes less dense as its temperature increases until all hydrogen bonds are broken and the water vaporizes.

Question 7

Seawater is a solution of dissolved minerals consisting of ions with positive or negative electrical charges.
The most common chemical constituents in seawater constituting 99.28% of the total amount of dissolved solids at any salinity are…name top ones

Answer 7

Chloride Cl- 55.04 
Sodium Na+ 30.61 
Sulphate SO42- 7-68 
Magnesium Mg2+ 3.69 
Calcium Ca2+ 1.16 
Potassium K+ 1.10

Question 8

Freezing Point depression

Answer 8

The density of seawater increases steadily as its temperature decreases below 0oC without freezing. Ions dissolved in seawater create the effect known as freezing point depression such that seawater freezes at -1.9oC at its maximum density.

Question 9

Aerosols

Answer 9

Droplets of seawater and salt particles suspended in the air during vigorous storms are called aerosols and have important consequences when they are washed out by rain or snow over a coastal landscape. Saline precipitation contributes to the chemical weathering of rocks releasing minerals such as sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and phosphorus (P) into lakes and rivers. These dissolved minerals are eventually returned to the ocean by surface runoff from land. The quantity of marine aerosols decreases with altitude and distance from the coast and is seldom noticeable in inland watercourses. There may be considerable differences in the chemical quality of coastal and inland freshwater systems (Figure 7-3).

Question 10

the flow of dry air on the leeward side of the mountain barrier creates a ____ _____ effect.

Answer 10

rain shadow

Question 11

______ ______ is what makes air masses rise and release all their water contents before moving over the top of the mountain

Answer 11

orographic uplift

Chemical weathering of rocks is facilitated by the deposition of these saline materials in precipitation, releasing dissolved minerals into lakes and rivers to be returned to the oceans in surface runoff from the land)

Question 12

Precipitation is naturally rich in dissolved _____ ______ making rainwater _______.

Answer 12

carbon dioxide

acidic

Question 13

Limestone lakes

Answer 13

Lake water holding abundant dissolved calcium, known as “hard” water, helps organisms regulate the salt balance of their bodies. Dissolved carbonate reacts with water molecules to maintain freshwater at a neutral pH that allows for high biodiversity in limestone lakes

Question 14

Humic Matter

Answer 14

Humic matter consists of organic molecules left over when decomposers have finished consuming detritus. Dissolved humic matter is especially abundant in peat bogs turning the water brown and acidic and excluding many species that reduce the bog biota’s biodiversity.

Question 15

Dissolved iron produced by the chemical weathering of rock minerals is an important constituent in the ________ processes in all cells.

Answer 15

respiratory

Question 16

Phosporous and Nitrogen limitations for River/Lakes vs. oceans

Answer 16

River water is poor in dissolved phosphate, which is a limiting factor for the growth of freshwater plants and algae. Phosphate is conserved in aquatic environments when organic matter accumulates in bottom sediments of freshwater lakes and bogs. Deep-sea basins are also immense storage tanks for phosphate-rich seawater. Phosphate is released into water by decomposers and used by aquatic producers. In ocean basins dissolved phosphate is brought to the sea surface by turbulent mixing and in this environment it represents a surplus nutrient compared to nitrate. Nitrate is more limiting to the growth of marine algae than phosphate. However, the N:P ratio changes with the salinity gradient from river mouths to open ocean making phosphate limiting near the river and nitrogen limiting towards open sea. Phosphate input from households to lakes, rivers and nearshore marine environments causes eutrophication, meaning the growth of aquatic plants and algae exceeds natural production

Question 17

Normal seawater has a salt content that is ___ %, if all the water evaporates. The salt content of seawater is expressed as a quantity measured in…(PSU, type of unit)

The salinity of seawater usually varies within the range of 30-40 psu

Answer 17

3.5: meaning 1 kg of seawater will yield 35 g of salt

practical salinity units, psu,

30 – 40

Question 18

Brackish Water

PSU range:

Answer 18

The term brackish water is widely used to describe a mixture of seawater and freshwater with salinity in the 0.5 – 30 psu range which normally occurs in marine surface waters near river outlets and where sea ice melts.

Question 19

The salinity of freshwater is lower than ___ psu.

Answer 19

0.5

Question 20

Lakes have surface areas larger than __ hectares

Answer 20

2 hectares or (20,000 m2)

Question 21

Gravity causes water with a ___ density to accumulate at the bottom of a basin while ____ water floats on top.

Answer 21

high

lighter

Question 22

At northern latitudes the bottom temperature of a deep lake is usually __ degrees C because at this temperature freshwater is at its maximum density.

Answer 22

4

The bottom water may become anoxic and even contain hydrogen sulfide (H2S) if allowed to remain isolated from air in response to the depletion of oxygen by biota.

Question 23

Describe the Layers of Lake water and their lineup in fresh water during:

Spring
Summer
Autumn
Autumn/Winter
Winter

Answer 23

1. Spring:
   - water temp is normalized throughout cycling from surface to bottom and has 100% oxygen content
   - spring overturn

2.Summer:
.2 distinct layers
-top is cycling water at >4 degrees
- bottom is about 4 degrees and has less than 100% oxygen content
-hydrogen sulphide present

3.Autumn:
.Same as Spring
-autumn overturn

4.Autumn/Winter:
.2 distinct layers
-top is cycling water at <4 degrees
-bottom is cycling water at 4 degrees and has 100% oxygen

5.Winter:
.3 layers
-Top is ice layer
-then a layer of <4 degrees
-then a layer of 4  degrees and has less than 100% oxygen and hydrogen sulphide is present

Question 24

thermocline

Answer 24

the temperature gradient between the upper and lower layer

Question 25

Autumn Overturn and Spring Overturn

Answer 25

During autumn when solar radiation decreases lake surfaces lose more heat energy than solar radiation can replace. Cooling increases the density of the wind-mixed layer, until the temperature has dropped to 4oC and the density is the same from the surface to the bottom of the lake. This period known as autumn overturn is when the whole water body circulates. Water saturated with oxygen is mixed with bottom water and removes hydrogen sulfide if present. As surface cooling continues below 4oC water with lower density forms a new upper layer eventually forming an ice cover at 0oC. Considering the length of time Arctic lakes are isolated from the atmosphere by ice some lakes may become anoxic at the bottom. When the ice breaks and the surface water is heated to 4oC the water column becomes aerated, establishing conditions for spring overturn.

Question 26

Estuary

Answer 26

An estuary is a partly enclosed coastal body of water with one or more rivers flowing into it, and with a free connection to the open sea.

Question 27

halocline

Answer 27

halocline, the transition zone between freshwater and seawater,

Question 28

estuarine circulation

Answer 28

The surface flow causes a loss of brackish water that is replaced by a compensation current transporting seawater flowing in the opposite direction underneath the brackish layer: this is called estuarine circulation.

Question 29

The density (σt) of seawater is calculated by measuring (2)

Answer 29

salinity and temperature. Density increases with increasing salinity and decreasing temperature. A salinity change of 1 psu corresponds to roughly 10oC change in temperature meaning thermal stratification is only significant when a water layer with uniform salinity accumulates solar heat at the surface. The density gradient between two uniform layers with different densities is known as a pycnocline.

Question 30

convergence front

Answer 30

The outer margin of a coastal current meets and exchanges water with shelf water in a dynamic mixing zone known as a convergence front. The mixed water flows away from the front at the surface while the more saline water from outside sinks below the front.

Question 31

Freshwater discharged into the Arctic Ocean from large rivers in Eurasia and North America generates brackish plumes of polar water that flow eastward over the continental shelves due to the ______ ______

Answer 31

Coriolis effect

Some polar water flows between Greenland and Canada into the Labrador Sea or may circulate to the Beaufort Gyre where it is retained and forms masses of multi-year ice. Most surface water and drift ice is transported by the Trans-Polar Drift past the North Pole and through Fram Strait between Greenland and Svalbard where transport becomes the East Greenland Current bound for the Labrador Sea.

Question 32

Name these Gyres and describe where they are:

BG=

GSG=

NSG=

Answer 32

Beaufort Gyre

• between Northern Canada and Russia
• area where water may become multi-year ice

Greenland Sea Gyre
Between Greenland, Svalbard, and Norway

Norwegian Sea Gyre
.Just a bit farther south of Greenland Sea Gyre between Greenland and Norway

Question 33

Seawater lost by surface currents from the Arctic Ocean is compensated by the _____ _____ ____, a current of warmer and more saline water flowing northward from the Atlantic Ocean, which is forced to sink north of Svalbard and forms an intermediate layer in the Arctic Ocean at a depth of 200 – 900 m (Figure 7-9).

Answer 33

North Atlantic Drift

Question 34

Global Thermohaline Circulation

Answer 34

Of particular interest is the Greenland Sea Gyre where cooling surface water sinks to a depth of about 600 m giving rise to the Global Thermohaline Circulation (Figure 7-10). Deep water from the Greenland Sea flows southward in the Norwegian Sea and sinks to the bottom of the North Atlantic Basin, flowing then into the Southern Ocean and circulating around Antarctica before entering the Indian and Pacific Oceans where it is brought to the surface by vertical mixing. Surface currents return the water to the southern Atlantic Ocean where it is transported across the Equator and into the Gulf of Mexico where it becomes the Gulf Stream. The Gulf Stream supplies warm and salt water across the Atlantic and into the Norwegian Sea closing the cycle as the Atlantic water submerges into the Arctic Ocean.

Question 35

Aquatic life forms are known as _____ when they live on or within bottom sediments and ______ when they can move freely in water masses above the bottom.

Life forms associated with floating sea ice are known as ______ animals.

______ is a term for all pelagic organisms that cannot resist transportation by currents and includes everything from bacteria to jellyfish more than 1 m in diameter.

______ are pelagic animals capable of horizontal migration between chosen habitats within their population system.

Answer 35

benthic,pelagic
-Benthos is a collective term for all benthic organisms.

sympagic

Plankton

Nekton

Question 36

Phototaxis

Answer 36

animals which live in water and perform vertical migration to stay at a preferred light intensity
-diurnal migration is when they move up during the night and slowly sink down during the day

Question 37

Nekton are ______ when feeding on plankton and _______ when feeding on fish.

Answer 37

planktivorous, piscivorous

Question 38

Aquatic plants and algae grow in the _____ zone where there is sufficient light for photosynthesis.

Answer 38

euphotic

Question 39

Clear water allows photosynthesis to occur in the upper __ m depth range and sometimes deeper.

Answer 39

50

Question 40

Two main groups of phytoplankton

Answer 40

Diatoms

Flagellates-use flagellum to move around

Question 41

Sympagic

Answer 41

Sympagic biota belong to the pelagic biome of the polar sea ice, although its producers have much in common with benthic micro-algae. Some ice algae may inhabit freshwater ponds on the ice or tiny channels inside the ice, while marine species stick together in long threads and thick mats attached to the underside of the ice. Some join the phytoplankton and continue production in ice-free water when their sympagic habitat melts.

Question 42

Zooplankton

2 types

Answer 42

Zooplankton are the fauna of planktonic animals in freshwater and marine ecosystems (Figure 7-12). First order consumers that feed on phytoplankton are mainly small crustaceans. Cladocerans constitute a large group of species that dominate in lakes and a few marine species are important in coastal waters. A group of copepods dominate the consumption of marine phytoplankton and contains some important freshwater species. Some mysid shrimps are nearshore phytoplankton consumers that move up and down estuaries with the tide. One species lives in brackish habitats along Arctic coasts and are present as an Arctic relict in lakes. Many other mysids are important detritus feeders in deep marine basins.

1. Holoplankton
2. Meroplankton-only part of their life is spent as plankton
   - ex: fish

Question 43

The epipelagic zone is the zone extending..

Answer 43

extending from the ocean surface to a depth of 200 m is the feeding habitat of fish like herring and capelin, and is roughly equivalent with the upper mixed layer of ice-free Arctic waters during winter.

Question 44

mesopelagic zone between ____ and ____ m

Answer 44

200 and 1000
-These organisms make fast diurnal migrations feeding in the epipelagic zone at night and migrating down to hide in darkness during the day.

Question 45

Three zones of Ocean water and depth

Answer 45

epipelagic zone:first 200 meters

mesopelagic zone: 200-1000 meters

bathypelagic zone: below 1000 meters

Question 46

bathypelagic zone

Answer 46

The bathypelagic zone, below 1000 m depth, contains Arctic deepwater characterized by sub-zero temperatures. Bathypelagic animals only see bioluminescence, which is light produced to detect or trick prey, confuse predators or attract mates. Bioluminescent algae and animals are also frequently observed at night near the ocean surface.

Question 47

Halophytes

Answer 47

Coastal salt marshes develop in estuaries where low salinity allows some plants to grow in fine-grained sediments deposited by rivers. Such halophytes may tolerate high ambient salinity by shedding salts from their leaves. Plants produce seeds that may be consumed by birds and rodents performing a major ecological function by shaping habitats for other organisms.

Question 48

The only truly marine vascular plants belong to the genus..

Answer 48

Zostera that form sea-grass beds in shallow water, mostly in estuaries. These plants disappeared from Arctic Norway due to a disease that hit Europe early in the 20th century and are still rare. The sea-grass now seems to be declining in Hudson Bay (Canada), which may deprive many populations of animals of an important habitat.

Question 49

ice foot

Answer 49

Many arctic shorelines develop an ice-foot in early winter, which gradually grows when the intertidal zone gets wet on high tide and freezes a new ice layer at each low-water tide. The ice-foot is completed when it fills the intertidal zone and establishes a vertical front as high as the local tidal range. Some intertidal animal species allow themselves to be trapped by the ice-foot and thus gain protection from sea ice scouring.These organisms contain anti-freeze molecules that prevent ice crystals from forming in their cells. Anti-freeze molecules are produced by a wide range of aquatic and terrestrial species exposed to supercooled water, ice cover or frosty air.

Question 50

Langmuir cells

Answer 50

Strong winds generate surface motions resulting in counter-rotating Langmuir cells (Figure 7-13) that occur in lakes and at sea. They are recognized by stripes of floating debris and foam where two cells rotate toward each other. Vertical water movements organize and concentrate organisms according to their buoyancy or preferred vertical migration. The result is small-scale habitats where one kind of biota may exist close to another. Once the wind stops the organisms reorganize themselves in response to factors such as light, tidal mixing, intra-specific relations, inter-specific attraction and avoidance.

Question 51

Synecological Relations : two types

Answer 51

1. Vertical water movements organize and concentrate organisms according to their buoyancy or preferred vertical migration. The result is small-scale habitats where one kind of biota may exist close to another.
2. Once the wind stops the organisms reorganize themselves in response to factors such as light, tidal mixing, intra-specific relations, inter-specific attraction and avoidance.

Question 52

Limiting factors for phytoplankton production are the availability of ______ and ______ ______.

Answer 52

light and inorganic nutrients

-Temperature is of less importance, which explains why phytoplankton production may be greater in higher rather than in lower latitudes.

Question 53

Describe timing of Phytoplankton growth

Answer 53

Permanent ice-cover in late winter and spring delays the production of phytoplankton in fjords and open seas. Production starts when the ice gets thinner and more transparent allowing penetration of light to ice-algae and phytoplankton. Production is restricted to a few summer months after ice break up, which is why ice-covered waters have low annual production.

Question 54

Marginal Ice Zone

Answer 54

The Marginal Ice Zone (MIZ), where polar sea ice meets subarctic water, is a convergence zone where tidal motion, wind and waves mix fresh meltwater with nutrientrich seawater causing vigorous production of sympagic diatoms while the sea-ice melts. As the ice-edge retreats due to melting, the production system shifts its geographic position and may end up far away from where it started.

Question 55

diadromous species

Catadromous

anadromous

Answer 55

Many organismic systems in freshwater communicate with the sea via diadromous species, organisms that migrate between freshwater and marine habitats.

Catadromous fish that reproduce in the sea and spend life stages in freshwater are few in Arctic waters.

anadromous meaning their populations spawn and spend juvenile stages in freshwater habitats.
ex: Anadromy is particularly associated with salmonids, a family of species well known to people that fish in rivers. All salmonid species spawn in freshwater and bury their eggs in sand or gravel on river bottoms where after some months they hatch.

Question 56

Man is a __-selected species

Answer 56

Man is an extremely K-selected species.

Question 57

Top-down control

Answer 57

Top down control in food webs occurs when animal populations at high trophic levels regulate flows of energy and matter at lower trophic levels

Question 58

Bottom-up control

Answer 58

Climate seems to control biological production at lower trophic levels by its regulation of physical processes that provide light and nutrients for primary producers.