Coral reefs increasingly face a number of threats including climate

Question

Coral reefs increasingly face a number of threats including climate change, ocean acidification, overfishing, and eutrophication. Due to a number of these threats, coral reefs have experienced a distressing decline in the past several decades, associated in many places with an increase in algal biomass. Accordingly, the loss of live coral cover is often associated with a phase-shift from a coral-dominated community structure to a fleshy algae dominated ecosystem.

There are many ways that this community shift can happen, and controversy exists over the relative importance of different factors in contributing to change. According to the bottom-up model, nutrient enrichment of coral reef areas results in an increase of benthic algae, which can grow quicker than coral in large blooms and out compete coral for resources, leading to reef degradation. In the top-down model, herbivory keeps macro algae biomass in check and allows the coral-dominated community to persist. Furthermore, disturbance events like bleaching can lead to a community shift because coral cover grows at a slower rate after a disturbance event and competitive interactions with macro algae become more frequent. The health of corals has come under more scrutiny particularly because of incidences of bleaching, which has been linked to heat stress. Thus, knowledge of coral physiology and coral-algae interaction is becoming increasingly relevant to understanding how corals can recover from stress events.

Previous studies have shown that a number of algae species have negative effects on coral health and physiology. For example, coral tissue mortality may be strongly affected by the presence of competing macro algae. However, in some cases, coral has been shown to actually overgrow and displace algae, while in other cases the algae has no significant impact on the coral. It seems the impact of macro algae on coral is dependent on both the coral and algae species, and that the competition between the two is highly variable, sometimes showing very little to no effect.

Despite the importance of understanding coral-algal competition and the phase-shifts in community structure, there has been very little previous experimental research on quantifying this interaction. Past studies have focused on the impact of herbivory or nutrient enrichment on algal growth and resulting competition with corals, but few quantify the effects of algae on coral physiology to measure the possible competition between the two.   1 
 1. The primary purpose of the passage is to

(A) discuss the competition for survival that exists between the coral tissue and the macro algae. 
(B) Evaluate the environmental consequences the loss of live coral cover has and suggest some reparative measures. 
(C) Discuss a factor that could be causative for the loss of live coral cover and suggest the need for further research to ascertain its impact. 
(D) Present a concern about the possible consequences of promoting macro algae population growth in marine ecosystems. 
(E) Explain why a particular strategy to increase coral reef population has been less successful than was anticipated.

2 
 2. Which of the following can be inferred about macro algae?

(A) They are often more hardy than the coral reef during disturbance events like bleaching. 
(B) They pose the biggest threat to the coral reef population. 
(C) They are less likely than are the corals to be affected by competition from other marine organisms. 
(D) Some species of macro algae are more competitive than others. 
(E) Some macro algae are considered inedible by many herbivores resulting in their being unchecked by herbivory.

3 
 3. According to the passage, the decline of coral reef could occur because of all of the following EXCEPT?

(A) Substantial elevation of temperature 
(B) Competition with other marine organisms 
(C) Increased levels of acidity in water 
(D) Herbivory of macro algae 
(E) Unscrupulous fishing practices

Source - CrackVerbal - GMAT Reading Comprehension Guide

KanishkM · Answer

For Question 1

Is the answer "C" because of these lines

Past studies have focused on the impact of herbivory or nutrient enrichment on algal growth and resulting competition with corals, but few quantify the effects of algae on coral physiology to measure the possible competition between the two.

Did it mean that "Some studies do not talk about the effects of algae" So they need to study more on this - by saying further research needs to be done ??

aragonn · Answer

Official Explanation for Q1 - Hope this will be helpful.

1.Answer: C Question 
type: Big picture 
A - Although A is discussed in the passage, it does not qualify as being the primary purpose. It's too narrow. 
B - The environmental consequences of the loss of coral are not discussed in this passage. 
C - The passage talks about the relationship between the coral cover and the macro algae. It also talks about how research results are inconsistent regarding the level of impact. The author also suggests that more research be done to understand this relationship and its consequences better. Option “C” best describes the purpose of the passage. 
D - “Promoting macro algae population growth” is outside the scope of this passage. 
E - No strategy to increase coral population is discussed.

aragonn · Answer

push12345  
Coral reefs increasingly face a number of threats including climate change, ocean acidification, overfishing, and eutrophication. Due to a number of these threats, coral reefs have experienced a distressing decline in the past several decades, associated in many

Accordingly, the loss of live coral cover is often associated with a phase-shift from a coral-dominated community structure to a fleshy algae dominated ecosystem.

enrichment on algal growth and resulting competition with corals, but few quantify the effects of algae on coral physiology to measure the possible competition between the two.

3. According to the passage, the decline of coral reef could occur because of all of the following EXCEPT?
(A) Substantial elevation of temperature - Y
(B) Competition with other marine organisms - Y
(C) Increased levels of acidity in water - y
(D) Herbivory of macro algae -- whats macro algae and it Herbivory ? Not given in passage.
(E) Unscrupulous fishing practices - y

On the basis of above lines I can eliminate All except D.

dave13 · Answer

aragonn  do you think RC passages of gmat prep companies are easier compared to official gmat prep ?

aragonn · Answer

dave13  - yes this one is really very easy passage. though people who start need to go a bit slow and practice on easy passages. This way they can practice their plan before implementing on real GMAT questions.

Mo2men · Answer

aragonn

Can you please post an official answer for question 2. I do not understand how answer is D. Where in the passage is mentioned anything about competition between macro species?

globaldesi · Answer

official explanation for all questions

Solution 1 OA: C
Tag: Big Picture
The passage talks about the relationship between the coral cover and the macroalgae. I also talks about how research results are inconsistent regarding the level of impact. The author also suggests that more research be done to understand this relationship and its consequences better. Option C best fits the purpose of the passage.

A: Although A is discussed in the passage, it does not qualify as being the primary purpose. It's too narrow.
B: The environmental consequences of loss of coral is not discussed in this passage.
D: “promoting macroalgae population growth” is out of the scope of this passage
E: No strategy to increase coral population is discussed

Solution 2. OA: D
Tag: inference
The scope lies here “It seems the impact of macroalgae on coral is dependent on both the coral and algae species, and that the competition between the two is highly variable”

A: untrue- the passage suggests that this is not the case all the time
B: This is untrue – they are a threat yes, but as to whether they are the biggest is never discussed.
C: Likelihood of facing competition as compared to coral is not discussed
D: This is true and is implied by the passage
E: “Inedible” is not supported by the passage
Solution 3. OA: D
Tag: Anchor Phrase
The passage provides proof for all of the options except D.
Herbivory actually helps keep coral reef communities intact. See lines 11-12 for evidence.
A: “Climate Change”
B: “can grow quicker than coral in large blooms and out-compete….” Suggest competition can reduce coral reef as well
C: “ocean acidification”
D: This is not true as the passage only discuss about Bleaching as a geological phenomenon not about “bleaching IN coral” – this is the correct response
E: “overfishing”

arora1 · Answer

For 2, the hint is here : For example, coral tissue mortality may be strongly affected by the presence of  competing  macro algae.

VerbalBot · Answer

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Coral reefs increasingly face a number of threats including climate

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GMAT Reading Comprehension (RC) Questions

Coral reefs increasingly face a number of threats including climate

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615 to 715 in 15 Days (Ria's Strategies)

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