Shelf Seas

Question 1

Continental Shelf

Answer 1

Ends at ~200m depth
8% of global ocean
Ecology strongly influenced by physical processes
Sharp tidal fronts divide two areas with differing temperatures due to difference in mixing in Wern Europe.

Question 2

Phytoplankton

Answer 2

Prokaryotes, picoplankton:
- Cyanobacteria
Eukaryotes, micro/mesoplankton:
- Dinos
- Haptophyte
- Bacillariophycae

Question 3

Cyanobacteria

Answer 3

Highest biodiversity in tropical zones
Symbiotic associations
Single long filaments or clumps of filaments

Question 4

Dinoflagellates

Answer 4

2nd most abundant
Auto, hetero or mixotrophic
Motile
Blooms often form red tides
Some toxic species

Question 5

Diatoms

Answer 5

All environments, most abundant.
Silica frustule, non motile
Spring blooms

Question 6

Coccolithophores

Answer 6

Posses ~30 Coccoliths per cell
150 species
Coccoliths reflects sunlight and heat back out of water
OA effects

Question 7

Phyto requirements

Answer 7

Light, CO2, O and Nutrients

Question 8

Nutrients

Answer 8

N, P and S macronutrients
Diatoms require Si
Redfield ratio
K, Ca, Mg
found from many sources in seawater

Question 9

Light

Answer 9

Euphotic zone, light extinction coefficient of water depends on wavelength, dissolved material and particles
Water absorbs red light strongly
Blue penetrates deepest

Question 10

P/E Curve

Answer 10

Response of photosynthesis to changes in light intensity. Photosynthesis increases with increasing light intensity until a point where photoinhibition occurs. Photosynthetic rate v. light will differ in sun or shade adapted algae, producing different photosynthetic efficiency curves.
Compensation depth, Light intensity is such that P=R in a single cell. Above compensation depth P>R
Critical depth, if algal cells mixed beyond this depth no net photosynthesis occurs

Question 11

Nutrients and PP

Answer 11

Oligotrophic, low concs of essential nutrients for algal growth, low PP
Eutrophic is opposite

Question 12

Seasonal trends

Answer 12

Winter: low PP, poor light, high nutrients, cold water
Spring: Warmer surface water, increasing light and decreasing nutrients. Blooms
Summer: Highest sun and temperatures. Low nutrients and stratification.
Autumn: Weakening thermocline, decreasing light and increasing nutrients.

Question 13

Zooplankton

Answer 13

Little ability to swim.
Diverse group of larval and adult forms, representing most animal phyla.
Occupy several trophic levels
Play key role in pelagic food webs and biogeochemical cycling

Question 14

Zooplankton diversity and distribution

Answer 14

Holoplankton, permanent
Meroplankton, temporary
Mostly heterotrophs but some are mixotrophs
Patchy distribution is very common, occurring at a variety of spatio-temporal scales caused by physical and biological processes.

Question 15

Diel Vertical Migration

Answer 15

Epipelagic, 0-200m and mesopelagic, 200-1000m
Preferred depth ranges vary with life stage, weather, season and latitude.
Light stimulus
Nocturnal, twilight and reverse migrations
Influence particle flux to seabed

Question 16

Seasonal vertical migration

Answer 16

Non-feeding adults overwinter at ~400m
Lay eggs at Dec to April
Population matures at surface when PP is high
By June, storage lipids accumulated
Migrate to deeper waters in Autumn
Temperature and food cues

Question 17

Food webs

Answer 17

Growth/production = Metabolism - egestion- excretion - food
10% efficiency, producers use 2% of solar energy
Growth yield is 10-30%
Trophic yield, production at trophic level 2/ level 1.
Upwelling region has greatest efficiency as food chains are shorter compared to coastal and open ocean.
V large fish production also