Carl Reefs 4 Flashcards
why don’t corals grow in water deeper than ~50-70m?
most coral grown in depths of 25m or less because they need sufficient light for photosynthesis. They are associated with usually clear, unproductive waters
what are the three most common forms of shading for coral reefs?
- 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
“The richness of both _______ and __________ decreased with increasing turbidity and chlorophyll.
hard corals and phototrophic octocorals
maximum mean annual concentration of chlorophyll and minimum annual secchi depth
[Chlorophyl]= 0.45um secchi= 10m
how far did the Burdekin River discharge plume extend to in the 2010-2011 wet season?
> 50km offshore and >100km northward
what kind of deposition of sedimentation poses a greater threat to corals? why?
organic, greater than mineral.
-corals find it more difficult to remove STICKY, MUDDY MARINE SNOW than discrete mineral particles
how has the increase in sugarcane farming in australia affected the corals reefs?
had led to both the increased turbitity and increased nutrient concentrations of freshwater discharge
what environmental effect are COTS linked to?
Increased eutrophication
COTS along with what other factor are the leading causes of coral cover losses of the past 27 years?
tropical cyclones
COTS has attibuted what percent of damage to the coral reefs?
42%
name 6 main threats to corals
- cyclones
- COTS
- bleaching
- run-off
- pollution
- coral (growth r`ates)
How do future plans need to change in comparison with the historical efforts of conservation efforts directed toward reserve implementations
new approaches are needed to sustain ecosystem function in exploited areas
how can macroalgae negatively impact coral?
- 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
what determines positive or negative feedback, driving a reef toward either unhealthy or healthy systems?
depends on grazing intensity is high enough to prevent the start of an algal bloom
what is a major grazer of patch reefs in the caribbean?
the urchin Diadema antillarum
is there one specific species of herbivous fish that is important to coral reefs?
name some
no, the best is a diverse amount of different herbivorous fish.
- redband parrotfish
- princess parrotfish
- ocean surgeonfish
the shift from coral to algal dominance of most carribean reefs ince the mid 1990s has been initiated by what?
a combination of
- the mass die-off of sea urchings
- overfishing of parrotfish
what is the main determining factor for the health of caribbean coral reefs?
overfishing, not climate change or pollution
what are some of the conventional fisheries management tools and strategies put in place to protect carribbean coral reefs?
- area closures
- gear restrictions
- species ban
- temporal closures
- active restoration
what are some identified characteristic thresholds which can identify coral reef regime shifts?
- structural complexity
- water depth
- fish density
- -> to predict reef responses to an extreme weather event
regime shifts from corals to macroalgae occur mostly due to what event?
coral bleaching
recovery from regime shift was favored when?
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
