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Donald C. PottsDonald C. Potts11, Kristin M. McCully, Kristin M. McCully11*, *, Wendy A. Wendy A. CoverCover1,21,2, Anne B. Warner, Anne B. Warner11

11University of California, Santa CruzUniversity of California, Santa Cruz22Fagatele Bay National Marine Sanctuary, American SamoaFagatele Bay National Marine Sanctuary, American Samoa

*Corresponding author: mccully@biology.ucsc.edu*Corresponding author: mccully@biology.ucsc.edu

A Multidisciplinary Approach to Restoration and

Sustainability of Midway Atoll's Shallow Reef Habitats

A Multidisciplinary Approach to Restoration and

Sustainability of Midway Atoll's Shallow Reef Habitats

Hawaii Conservation Conference

August 2012 Hawaiian Archipelago

Midway Atoll(Pihemanu)

Protected

Intact food chain

High latitude

Disturbance history

Key element in PMNM

Aims

• Scientific Basis for enhanced conservation, management, and ecosystem sustainability of Midway Atoll’s islands, reefs and biota.

• Dynamic Baselines for understanding future changes by establishing the nature and magnitudes of past and present patterns of biological and physical variation.

• Experimental investigations of important species and processes affecting cover, composition, and growth and destruction of coral reef structures and communities.

• Knowledge and technologies to enhance effective long-term conservation and management of reefs throughout the PMNM, as well as other marine protected areas of the Pacific.

Coral reef community interactions Herbivore impacts on algae & coral recruitment

Factorial experiment

• Algal biomass

• Algal species

composition

• Coral

recruitment

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Fish grazing prevented macroalgal growth Fish grazing increased coral recruitment

Coral reef community interactions Coral reef community interactions

?

urchins present: urchins removed:

Bioerosion of corals by urchins

n = 10n = 10

Porites Montipora

Rock-boring urchin(Echinometra mathaei)

6 - 34/m2

Urchins damaged coral tissue & skeleton

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Coral reef community interactions Conclusions & implications for conservation

• Fishes are the dominant herbivores on Midway

• Fish grazing indirectly promotes coral recruitment

• Particularly important to protect fish herbivores

• Urchins can directly damage corals through bioerosion

• May be able to promote coral cover by reducing urchin abundance

Restoration of Porites compressa patch reefs Methods

Transplant Sites

Source

All coral recruits were Pocillopora sp.

• 10 tiles at source site and at 2

transplant sites

• No significant difference between sites

• Very low recruitment compared to

previous Midway recruitment studies

– mean 2.7 recruits per tile

• All coral recruits were Pocillopora sp.

• No natural recovery possible via

recruitment of Porites compressa

Most transplants survived 10 months

0%

20%

40%

60%

80%

100%

RB1 RB2 RB3 RB4 RB5

Perc

en

t S

urv

ival

Site

Shallow (1-2 m)

Deep

Shallow

(1-2 m)

Deep

(3-4 m)

Near Island Far from Island

More analysis coming soon!

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Black-lipped pearl oysters are rare & hard to restore

Talk in this session at: 11:50 am

Much more analysis in progress

USFWS

Sediment & rubble collectionsReef cores

Reef accretion/erosion Coral reproduction

Conclusions & implications for conservation

• Particularly important to protect fish herbivores

• May be able to promote coral cover by reducing urchin abundance

• Restoring Porites compressa reefs by transplantation holds great promise

• May be very difficult to restore pearl oyster beds

• More information coming soon!

THANK YOU!Info & photos at:

http://bio.research.ucsc.edu/people/potts/midway/