Chapter 8- oceans and fisheries Flashcards
coral reefs
really struggling will be the canary in the coal mine for climate change
Ocean ecosystems
- 72% of Earth’s surface
- up to 9000m (no O2 when really deep)
- costal zones & continental shelves= most productive (in top 100m) (find estuaries)
- Nutrient availability, temperatures, and light=major ecological factors
- large bodies of water have a higher specific heat capacity
- can regulate temperatures around land masses
Land
limiting factor=water
- productivity increases from poles to tropics
- biotic pyramids- reduced at each trophic level
Ocean
limiting factor= nutrients
some most productive areas in Canada
-rapid turnover at 1st trophic level
-some areas in arctic are most productive due to interplay between ocean & land
Nutrients in the Ocean
- concentrations increase with depth
- most productive area=costal zones and areas of upwellings
- can be held for long periods of time due to low oxygen and bacterial influence
- Hope to Vancouver estuary= VERY diverse
Carbon sequestration
All carbon stored in dead animals in the ocean sink to the bottom of ocean and deompose there
1/4 to 1/3 of human CO2 emissions are absorbed creating carbonic acid= change in pH
-potential way to combat climate change
Carbon in the ocean
- oceans key in absorbing CO2
- carbon moved out of surface water to deeper ocean
- stored in dead organisms, ocean sediments, coral reefs
- takes up 2 billion tonnes of carbon/year
Coral Reefs
- regulation of environmental disturbances (due to biodiversity)
- treatment of organic waste too much= death of coral reef
- food production
- recreational opportunities
- high biodiversity= higher resilience
Coral Bleaching
happens when exposed to higher acidity
Coral and Global Warming
CaCO3 + COOH= erosion/dissolve
zooxanthellae produce CHO that feed corals, helps with photosynthesis
increased temperatures=expelling zooanthellae so coral leaching occurs
Coral
individual polyps and calcium carbonate skeletons
Dead coral
white due to absence of algae
Marine food webs
HUGE biodiversity
complex=resilient
global warming=negative implications
Marine Food Webs cold water
- simple in colder waters
- cannot afford to lose a lot of species
Thermocline
line where temperature in ocean gets colder
- sharp transition in temperature between warm surface waters and cool deeper waters
- colder water below thermocline due to carbon being absorbed and sinking
Thermocline Circulation
- Cooled water sinks into deeper basin with water close to 0C (not frozen due to salt)
- High salt content critical (increases water density)
- Dense water sinks and carries carbon with it
Implications of Global warming on thermocline circulation
- Ocean temperature increases therfore changing water density
- Freshwater glaciers melting males seas water less salty which changes the salt:fresh water ratio
Management Challenges
The real problem is that we do not undersatnd our ocean ecosystems and we have yet to learn they cannot be managed
- need to learn about them before we can manage them well
- deep sea vents 50 to 100 years behind general natural history because they are really hard to explore
Costal Development
half of world’s costal wetlands destoryed to support development
-lose estuary ecosystem and interface between terrestrial and ocean world just so we can have an inner harbour
-Canada= bad
US=worse
How much of the world’s population lives in costal zones?
60%
Implications of Costal Development
lots of flooding
no way to absorb storms *hurricane Katrina
loss of biodiversity with loss of land/water interface (waves hit a wall and head back out to sea)
Fisheries
- 1950s saw onset of industrial fisheries *almost to death
- resource base now less than 10% for entire communities of large fish species
- eating ourselves our of an ocean ecosystem
Global Fisheries
Major source of protein (too many people reliant on fish
- total catch grew, now stabalizing (but declining per capita amount of fish being caught)
- major employer (many towns dependant)
- high revenues (but many subsidies) help buy fishing boat
Global Fisheries Harvest
aquaculture=13% of worlds fish harvest
fish farming or salmon & oyster
Top marine and Inland Fisheries
=China
many countries highly dependent on fish
then Peru, USA, indonesia, Japan, Chilie, India, Russia, Thailand, Norway
Depleting Fisheries
- 1/3 of fisheries are over-exploited
- 70% of species used at or above sustainable levels
- now fishing down the food chain (good for good stuff until it runs out then we catch the next most desirable thing)
- equivalent to prey switching
By-catch
non targeted fish
Aquaculture
=farming of aquatic organisms (fish, shellfish, plants, in controlled environments -BC and NB dominant -Atlantic salmon is leading export Effects: -fish disease -genetically modified fish -impacts on wild species (too many nutrients with dead zone due to overabundance of salmon feces
What is the limiting factor in terrestrial ecosystems?
water
What is the most common limiting factor in marine ecosystems?
nutrients
Fisheries and Marine mammals
- manages by fisheries and oceans
- many whales now hunted to extinction
- Northern Right Whale (one of most rare)
- get 160,000L of oil from 1 whale
- whale populations declining
- accumulates biotoxins
Fishing Methods
- Seine Fishing
- Bottom-Trawling
- Trawling
- Longline Fishing
- Trolling
- Dredging
Seine Fishing
using a large fishing net with weights along the net’s bottom and floats along the top
- encircle school of fish
- dolphins may get caught
Bottom Trawling
heavy nets dragged along ocean floor- ground fish and cod, squid, halibut, rockfish
- lots of by-catch
- incidental damage to ocean floor
Drift netting
=illegal (hang line out for kms and leave it)
Trawling
pulling a large fishing net behind more than 1 boat
-midwater trawling=anchovies, shrimp, mackerel, tuna
Longline FIshing
uses 100s or 1000s of baited hooks hanging from a single line (swordfish, tuna, halibut, sablefish)
Trolling
one or more fishing lines baited with lure or bait fish are drawn through the water behind a moving boat (makerel, kingfish, tuna, marlin)
-go slowly through the water
Pollution
oceans are a sink for many pollutants *agriculture, industry, urbanization, waste disposal
-Chemical pollutants
-toxic materials
-nutriends
-endocrine disrupter (DDT) fish and polar bears
rain goes into ocean and takes all the stuff from the street with it
Bioaccumulation
accumulation of toxins in higher trophic level species
Dredging
towing a dredge along the ocean bottom (scallops, oysters, sea cucumbers)
-pull along productive zone of ecosystem
Worst method of fishing
drift nets, illegal
catch whales, sea turtles, dolphins as by-catch)
Oil and Gas development
60% of world’s global oil production is from sedimentary basins under the ocean
Canada’s oceans
-longest coastline in the world
-Management
fisheries and marine species (department of fisheries and Oceans)
sea birds=Environment Canada
shoreline=provinces and municipalities
-silo effect when they don’t meet and talk
-lots of overlap but can also cause administrative difficulties
200 mile limit
set limit that is ours to manage
Pacific Ocean
- sea temperatures higher than Arctic
- important for waterfowl, seasbirds, and shoreline
- seas lions seals, whales
Threats to Pacific Ocean
- pollution
- habitat loss
- overfishing
- aquaculture
Arctic Ocean
- often covered by permanent pack ice
- biological and productivity generally low (poynas=high)
- bowhead, beluga, narwhal aka northern right whale floats when killed)
Threats to Arctic Ocean
- increase oil and gas activities
- habitat loss (melting)
- climate change
- political disputes
Atlantic Ocean
20C warmer than arctic
- highly productive
- abundant marine life
- 22 species of whales and 6 species of seals
- cod fishery collapse (federal gov allowed this to happen)
Threats to Atlantic Ocean
- oil and gas activities
- over harvesting
- political disputes
Aboriginal Uses of Resources
treaty rights to subsistence fishing
-conflicts court cases cooperation
Ocean’s Act
- Sustainable development
- Integrated Management
- Precautionary Principle
Marine Protected Areas
Sagunenay St. Lawrence NMP Fathom 5 NMP Lake Superior NMP Endeavour Hydropthermal Vents MPA (managed by Parks Canada)
