Storm impacts on benthic community structure on Kiritimati atoll

Methods

§  Photo quadrats at four sites (2 each of high and low human

disturbance) were taken before, just after, and three months

after the storm that occurred in late January, 2015 to quantify the effect of the storm on

benthic community assemblages (n=352).

§  The impacts of the storm were investigated using multinomial regression looking at two

aspects of benthic communities:

Overall changes in substrate The changes in percent cover of

coral, algae, and sediment were examined to look at the overall changes in substrate

composition at each site.

Changes in dominant coral morphologies

The impacts of the storm on five coral morphologies were

examined to determine changes in structural complexity of reef ecosystems and dominant coral morphologies.

Acknowledgments

We thank our collaborators and field assistants: K. Tietjen, J. McDevitt-Irwin, J. Burns, K. Cox. We gratefully acknowledge the support NSERC, JCURA, Rufford Smalll Grants for Nature, and NSF provide for our research goals. Images used by permission of the Baum lab.

Background

Results

Changes in substrate types:

Figure 1. Changes in the occurrences of substrate types at two sites of low human disturbance (Low1 and Low2) and two sites of high human disturbance (High1 and High2) with 95% credible intervals. A shows the changes in the probability of occurrence of each substrate type across three sample

times: before- August 2014, After 1-February 2015 (immediately after the storm) and After 2-May 2015 (3 months after the storm). B shows the changes in substrate composition between the Before and After1 sampling times; a negative value indicates a decline in the proportion of that substrate. The group “other” includes invertebrates other than coral, hard substrates and sand.

Storm waves on Kiritimati in January 2015; storm damage at a site of low human disturbance;

Montipora sp. covered in sediment after the storm

Changes in coral morphologies:

Figure 2. Changes in the occurrences of five coral morphologies at two sites of low human

disturbance (Low1 and Low2) and two sites of high human disturbance (High1 and High2) with 95% credible intervals. A shows the probability of occurrence of each morphology across three

sample times: before- August 2014, After 1-February 2015 (immediately after the storm) and After 2-May 2015 (3 months after the storm). B shows the changes in morphology composition between the Before and After1 sampling times; a negative value indicates a decline in the proportion of that

morphology.

Results

Changes in substrate types:

Changes in dominant coral morphologies:

Lisa Szostek, Geoffrey J. Osgood, Danielle C. Claar, Julia K. Baum

Department of Biology, University of Victoria

PO Box 1700 STN CSC

Victoria, BC, V8W 2Y2, Canada

Literature Cited

1. Pandolfi, J.M., Bradbury, R.H., Sala, E., Hughes, T.P., Bjorndal, K.A., Cooke, R. G., McArdle, D., McClenachan, L., Newman, M.J.H., Paredes, G., Warner, R.R., & Jackson,

J.B.C. (2003). Global trajectories of the long-term decline of coral reef ecosystems. Science, 301,

955-958.

2. Fribourg, A.S. (1999). Global change and the decline of coral reefs. Swiss Journal of Geography,

54, 125-131.

3. Emanuel, K. (2005). Increasing destructiveness

of tropical cyclones over the past 30 years.

Nature, 436, 686-688.

4. Webster, P.J., Holland, G.J., & Curry, J.A.

(2005) Change, H.R. Changes in tropical cyclone number, duration and intensity in a warming environment. Science, 309, 1844-1846.

5. Norstrom, A.V., Nystrom, M., Lokrantz, J., & Folke, C. 2009. Alternative states on coral reefs: beyond coral-macroalgal phase shifts. Marine

Ecology Progress Series. 376, 295-306.

6.. Alvarez-Filip, L., Dulvy, N.K., Gill, J.A., Cote, I.M., & Watkinson, A.R. 2009. Flattening of

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Further Information

§  Contact information:

Email: lszostek@uvic.ca

§  We invite you to learn more about: research in the Baum Lab

baumlab.weebly.com

Next Steps

§  Incorporating more sites of both high and low human disturbance into this study

§  Continued monitoring of the reef ecosystem to assess

recovery, as well as the impacts of other threats such as ENSO events.

§  Coral reef communities are in

decline as a result of anthropogenic

and natural threats including storm

events, which are hypothesized to

increase in intensity and frequency

due to climate change

_.

§  Disturbances have a tendency to

shift benthic communities to a

macro-algae dominated state and

to shift coral species from

structurally complex reef building

species to less complex species

_.

§  These changes lead to a decreased

ability to support reef fishes which

thousands of people rely on

worldwide for subsistence

_.

§  This study quantified the impacts

that a severe storm had on benthic

community structure on Kiritimati,

Kiribati.

B

A

A

B

§  Our results indicate that coral cover and algae cover declined after the storm to favour a sediment

dominated state (Figure 1).

§  These results were consistent across sites of high and low human

disturbance and no significant difference in the magnitude of

changes between sites of different disturbance levels was observed. §  An insignificant difference in

changes in substrates between the two post-storm sampling times

indicate that the storm was the driver of the changes in benthic

substrates and that recovery did not occur within three months of the

storm event (Figure 1A).

§  Our results indicate significant

changes in the composition of the

five coral morphologies (Figure 2).

§  The proportion of massive corals

declined and the proportion of

encrusting corals increased as

expected; however the direction of

change in proportions of the other

three morphologies were not

significant in either direction

(Figure 2B).

§  These changes in the relative

amounts of coral morphologies has

important implications for the

structural complexity provided for

for reef fishes.