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34 Cards in this Set
- Front
- Back
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peaks in late spring
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-lots of organic matter is produced
-much of the organic matter sinks from surface -fueled by nitrate |
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peaks in the mid- summer
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decomposition and respiration of organic matter produced earlier by pytoplankton
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stratification
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-formation of distinct layers of water due to differences in density
-warmer temp, and fresh water from rivers |
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less dense surface water prevents deep water from mixing____
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oxygen from atmosphere
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Why is the dead zone new?
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-First reported in the 1970s
-has grown in extent and duration since monitoring started in 1985 |
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_____are the base of the marine
food chain |
algae
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Red Tides
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-Discolouration of the water caused by
specific phytoplankton species -accompanied by fish mortality, human illness and death |
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Aboriginal people would use colour changes to determine when to harvest shellfish
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-coastal British Columbia
-not harvest when bioluminescent Alexandrium were present |
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4 types of harmful algae bloom
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-bio toxins
-anoxia (dead zone)w -modified food webs -water discoloration |
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water discoloration
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-not toxic or damaging
-impacts recreation |
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Proliferation of a single species (a bloom)
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-dominant phytoplankton is not
eaten by grazers -disrupts a food web -brown tides |
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brown tides
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small phytoplankton
completely dominants ecosystem |
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phytoplankton-produced organic toxins
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-among most toxic compounds known.
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Paralytic shellfish poisoning (PSP)
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-closely related to Tetradoxin (fugu)
-neurotoxin (animals/humans) |
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Amnesic shellfish poisoning
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-domoic acid
-neurotoxin |
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Neurotoxins
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damage and destroy brain and nervous system
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Hepatotoxins
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is a toxic chemical substance which damages the liver.
-affects mammals & birds |
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toxic phytoplankton are ingested
by _____ |
shellfish (mussels, clams) and
grazers (copepods, fish) |
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toxics have ____ effect on their direct competitors and grazers
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minor
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domoic acid could = iron starvation
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cells use domoic acid to acquire iron
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where is fertilizer use increasing the most?
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developing nations like china & india
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Gill Nets
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-large nets of flexible material
-directly trap fish, efficient -attached to shore, vessel, bottom, or drifting. |
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Seine
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net blocks fish escape
-first open, then drawn closed & fish are captured -smaller, undesired fish can escape -attached to vessel or shower |
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Longline
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long string of many baited hooks
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trawl
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net pulled through water, net prevents fish escape
-vessels can chase fish -net size limited by size of fishing vessel -very efficient -smaller fish may escape |
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Traps
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a cage with a flexible entry
-baited -smaller organisms can escape - |
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Bycatch
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-undesired species captured during fishing
-sometimes economically valuable |
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Gill Nets
-good, bad, ugly |
-efficient, cheap
-bycatch, cheap, nets are often discarded -bycatch of rare & charismatic organisms |
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Seine
-good, bad, ugly |
-vessel not required, reusable nets
-labour intensive, not selective, sometimes not efficient |
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Longline
-good, bad, ugly |
-selective by choice of hook, dept, bait, high quality fish, no damage to nets
-labour intensive, capital intensive, -some bycatch issues (birds) |
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trawl
-good bad ugly |
-efficient
-capital intensive, by catch -by catch, bottom damaging |
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traps
-good bad ugly |
-selective, high quality product
-labor intensive, capital intensive |
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population grows fastest at _____ population sizes
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intermediate
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maximum sustainable yield
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most intensive fishing which leaves enough fish or squid to sustain high growth rates
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