Carl Reefs 4 Flashcards

1
Q

why don’t corals grow in water deeper than ~50-70m?

A

most coral grown in depths of 25m or less because they need sufficient light for photosynthesis. They are associated with usually clear, unproductive waters

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2
Q

what are the three most common forms of shading for coral reefs?

A
  • Increased turbidity in association with changes in land-use practices and its affects freshwater discharge
  • Eutrophication of coastal waters
  • changes in the population numbers of natural grazers which keep the reefs clean of external algae build-ups
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3
Q

“The richness of both _______ and __________ decreased with increasing turbidity and chlorophyll.

A

hard corals and phototrophic octocorals

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4
Q

maximum mean annual concentration of chlorophyll and minimum annual secchi depth

A
[Chlorophyl]= 0.45um
secchi= 10m
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5
Q

how far did the Burdekin River discharge plume extend to in the 2010-2011 wet season?

A

> 50km offshore and >100km northward

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6
Q

what kind of deposition of sedimentation poses a greater threat to corals? why?

A

organic, greater than mineral.

-corals find it more difficult to remove STICKY, MUDDY MARINE SNOW than discrete mineral particles

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7
Q

how has the increase in sugarcane farming in australia affected the corals reefs?

A

had led to both the increased turbitity and increased nutrient concentrations of freshwater discharge

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8
Q

what environmental effect are COTS linked to?

A

Increased eutrophication

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9
Q

COTS along with what other factor are the leading causes of coral cover losses of the past 27 years?

A

tropical cyclones

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10
Q

COTS has attibuted what percent of damage to the coral reefs?

A

42%

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11
Q

name 6 main threats to corals

A
  • cyclones
  • COTS
  • bleaching
  • run-off
  • pollution
  • coral (growth r`ates)
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12
Q

How do future plans need to change in comparison with the historical efforts of conservation efforts directed toward reserve implementations

A

new approaches are needed to sustain ecosystem function in exploited areas

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13
Q

how can macroalgae negatively impact coral?

A
  • interferes with coral recruitment
  • surpresses coral growth and fecundity
  • can cause direct albeit localised coral mortality to certain species.
  • recovery rate of coral poplns is disminished by macroalgal blooms and forms feedbacks taht drive reef decline further
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14
Q

what determines positive or negative feedback, driving a reef toward either unhealthy or healthy systems?

A

depends on grazing intensity is high enough to prevent the start of an algal bloom

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15
Q

what is a major grazer of patch reefs in the caribbean?

A

the urchin Diadema antillarum

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16
Q

is there one specific species of herbivous fish that is important to coral reefs?
name some

A

no, the best is a diverse amount of different herbivorous fish.

  • redband parrotfish
  • princess parrotfish
  • ocean surgeonfish
17
Q

the shift from coral to algal dominance of most carribean reefs ince the mid 1990s has been initiated by what?

A

a combination of

  • the mass die-off of sea urchings
  • overfishing of parrotfish
18
Q

what is the main determining factor for the health of caribbean coral reefs?

A

overfishing, not climate change or pollution

19
Q

what are some of the conventional fisheries management tools and strategies put in place to protect carribbean coral reefs?

A
  • area closures
  • gear restrictions
  • species ban
  • temporal closures
  • active restoration
20
Q

what are some identified characteristic thresholds which can identify coral reef regime shifts?

A
  • structural complexity
  • water depth
  • fish density
  • -> to predict reef responses to an extreme weather event
21
Q

regime shifts from corals to macroalgae occur mostly due to what event?

A

coral bleaching

22
Q

recovery from regime shift was favored when?

A

when reefs were structurally complex and in deeper water

  • when density of juvenile corals and herbivorous fishes was relatively high
  • when nutrient loads were relatively low