Global disparity in the resilience of coral reef

Author George Roff and Peter J. Mumby

Presented by Shweta Sharma

Introdution

What is resilience ?

Why coral reef is one of the most intensively studied system

in context of resilience ?

Coral reef resilience and geographic bias.

The two major biogeographic provinces of coral reef

1. The caribbean 2. Indo-Pacific

Great caribbean coral reef

Deep water coral

Great caribbean coral reef

5 Meter Reef Coral

Indo-Pacific Corals

Indo-Pacific Coral

Differences in the recovery and state of Caribbean versus Indo-Pacific reefs

Indo-Pacific and Caribbean reefs differ in many ways.

1) Faunal composition, Grazing pressure

2) Greater niche partitioning of herbivore in the Indo-Pacific

while herbivore biomass in the Caribbean lies below

potential carrying capacity.

3) Species richness(Acanthudidae), Coral reproductive trait

4) Ecological resilience capacity

5) Greater proportion of macroalgal dominance and a higher severity of phase shift in the caribbean than in the Indo- Pacific.

Differences in the recovery and state of Caribbean versus Indo-Pacific reefs

Indo-Pacific and Caribbean differ in many ways.

Caribbean reef shows decline of trajectories, with no

observation of recovery following disturbance .

46% of reef in Indo-Pacific have showed evidence of recovery following disturbance.

83% of Caribbean reefs exhibited either no recovery(47%)

or no decline 36%.

39% of Indo-Pacific reef exhibited either no recovery(24%) or no decline(15%).

Bar Graph showing Recovery, No decline, No recovery of coral reef

Graph showing macroalgal dominance

Biodiversity-based hypotheses

Hypotheses 1

Loss of fast-growing Acropora corals in the Caribbean

are responsible for low resilience of coral in this region.

1) Two categories of corals

I) Fast-growing branching corals from families Acroporidae

and Pocilloporidae capable of extending > 100 mm per

year.

II) Slow-growing corals capable of extending<50 mm per

year.

Biodiversity-based hypotheses

Hypothesis 2

Higher diversity and greater functional redundancy of

herbivores in the Indo-Pacific than in caribbean.

1) Elevated herbivore diversity can increase reef resilience

by providing greater niche diversification and creating

functional redundancy.

2) Burkepile and Hay found that two complementary herbivore species were more effective in mitigating algal bloom than was a single species

Biodiversity-based hypotheses

3) There is striking difference in the species and generic

richness in Caribbean and Indo-Pacific.

a) Of the 88 species and six genera of Acanthuridae that

inhabit in the Indo-Pacific and Caribbean regions,

Caribbean have only four species represented by a single

genus(Acanthurus).

b) Caribbean lacks acanthurids of the genus Naso, some of

which consume the largest of reef macrophytesargassum spp.

Bottom-up hypothesesMacroalgae bloom faster in the Caribbean

Bottom-up hypothesis

Bottom-up hypotheses

Hypothesis 3

Higher adult stock of macro algae on Caribbean reefs

imply higher rate of algal recruitment in this region.

1) Speed of algal bloom is high where herbivory is intense so this finding leads to fourth hypothesis.

Hypothesis 4

Various anthropogenic activity like land cultivation, deforestation, producing nutrients, and nutrient supply from terrestrial sources might be higher in Caribbean leading to Coral algal phase shift.

Bottom-up hypotheses

Hypothesis 5

Nutrient nitrogen and phosphorus helps in algal growth but it growth is limited by various metals e.g iron. Algal growth is less limited in the Caribbean due to increase in Aeolian dust a good source of iron , resulting increase in algal bloom when other enabling condition are met.

Top-down hypotheses

Hypothesis 6

Herbivore biomass is greater in Indo-Pacific than in Caribbean creating higher absolute grazing pressure in Indo- Pacific

1)Total herbivores fish biomass in the Indo-Pacific averaged

29.0gm-2 while Caribbean have 9.25gm-2.

2) Parrotfish biomass in the Indo-Pacific was nearly twice that of the Caribbean. (13.12gm-2 VS 6.7 gm-2)

3) Biomass of surgeonfish is more than fourfold higher in the Indo-Pacific than in the Caribbean( 11.61gm-2VS2.56gm-2) and maximum biomass found 12 fold higher in the Indo-Pacific than in the Caribbean.

Conclusion

Indo-Pacific reef have greater capacity of resilience than

the Caribbean.

Algal bloom occur more readily in the Caribbean .

Disease that resulted in loss of both fast growing coral, are responsible for present state of the caribbean.

Referances:- Roff, G., & Mumby, P. J. (2012). Global disparity in the resilience of coral reefs.Trends in ecology & evolution, 27(7), 404-413.

Thanks