Impacts of non-point source nutrient pollution and water turbidity pulses on threatened

Acropora palmata (Elkhorn coral) populations in Vega Baja, PR

Jesyka Meléndez-Rosa1, Edwin A. Hernández-Delgado2, Alejandra Alvarado2, Ricardo Laureano3

1Department of Biology, University of Puerto Rico, Cayey, 2University of Puerto Rico, Center for Applied Ecology and Conservation, Coral Reef

Research Group, 3Vegabajeños Impulsando Desarrollo Ambiental Sustentable

Objectives

 To present and discuss: Important issues that affect one of the largest Elkhorn coral populations in the U.S. Caribbean.Preliminary results associated with our research.

Corals, Why should we care?

They are the principal builders of coral reef frameworks.

They remove and recycle carbon dioxide, thus buffering climate change impacts.

Shelter the land from harsh ocean storms and floods.

Provide resources for fisheries.

Promote tourism.

It is an intricate ecosystem and contains a paramount biodiversity comparable with tropical forests.

Corals could potentially provide important anti-cancer drugs and a compound that blocks ultraviolet rays (Proksch et al. 2002).

Coral skeletons are being used as bone substitutes in reconstructive bone surgery. Bone tissue and blood vessels gradually spread into the coral graft. (Yun-Chun Wu et al. 2007)

The coral reef provides a living laboratory.

Healthy reefs represent the principal source of proteins, income and livelihood of coastal communities across multiple developing nations.

Just off our very own shore…

…of Vega Baja, Puerto Rico, lies one the largest threatened Elkhorn coral (Acropora palmata) remnant populations on the U.S. Caribbean

http://www2.luventicus.org/mapas/puertorico/vegabaja.gif

http://patricklynch.net/florida-keys-2008/molasses-reef-dives/elkhorn-coral-lynch.jpg

What is threatening our hot spot?

Raw sewage discharges.

Highly turbid, nutrient-rich waters from:

An adjacent seawall construction site. Non-point sources (i.e., stormwater runoff). Adjacent river runoff (which is also home to a garbage dumping site ).

Main Question

Healthy communities may exist in very turbid environments (Pastorok & Bilyard 1985), but it may depend on the hydrology and currents of the system.

The main problem at Vega Baja is the high frequency of pollution pulses impacting the reefs, thus…

Are these pollution pulses impacting the threatened Elkhorn coral population?

And if so...

How? And to what extent?

Hypothesis

These pollution pulses are indeed contributing to the decline in coral health and abundance.

There is a pollution stress gradient that diminishes as we head further out into the ocean and further west of the impacted zone.

What we are doing to address this issue…

We initiated a long-term monitoring program to assess concentrations of:

PhosphateAmmoniaNitrate Nitrite

Along the coast and across permanent coral reef transects.

Also, measurements for suspended solid material, turbidity and changes in coral conditions are taken.

Preliminary Results

Increased levels of turbidity and sediment bedload, potentially from the seawall construction site, during August 13-20, 2010, caused significant localized coral mortality.

Frequency of impacted colonies increased up to 90% adjacent to the project site, and decreased with increasing distance.

Patchy necrosis in Acropora palmata

White pox inA. palmata

Black band disease in Diploria strigosa

Increasing distance

Percent of A. palmata colonies impacted by partial tissue mortality across a distance gradient from the

rip-rap expansion project

Preliminary Results

The two highest chronic turbidity levels recorded have been from the Cibuco River runoff and from areas adjacent to the seawall, respectively.

Nutrient concentrations are highly variable but recurrent pulses are highly frequent and in the long-term have significantly contributed to coral reef decline.

Site

Cibuco Rive

r

Public Beach

Seawall

Discharge

Plazoleta

El Eco

Sarapa

Tur

bidi

ty L

og10

NT

U (

95%

C.I

.)

0.1

1

10

100

1000

Sep SepOctNovDecJan

Water turbidity

Site

Cibuco Rive

r

Public Beach

Seawall

Discharge

Plazoleta

El Eco

Sarapa

PO

4 L

og10

uM

(95

% C

.I.)

0.1

1

10

100

1000

SepSepOctNovDecJan

Phosphate

Site

Cibuco R

iver

Public Beach

Seawall

Discharge

Plazoleta

El Eco

Sarapa

NH

3 L

og1

0 u

M (

95%

C.I

.)

1

10

100

1000

10000

SepSepOctNovDecJan

Ammonia

Site

Cibuco R

iver

Public Beach

Seawall

Discharge

Plazoleta

El Eco

Sarapa

NO

3 Lo

g 10 u

M (

95%

C.I

.)

1

10

100

1000

SepSepOctNovDecJan

Nitrate

Site

Cibuco Rive

r

Public Beach

Seawall

Discharge

Plazoleta

El Eco

Sarapa

NO

2 Lo

g 10 u

M (

95%

C.I

.)

0.1

1

10

100

1000

SepSepOctNovDecJan

Nitrite

Conclusions

Threatened Elkhorn coral populations have been significantly impacted by recurrent pollution pulses from different sources.

Sediment bedload, high turbidity and non-point source sewage pollution have caused significant coral mortality pulses.

No meaningful actions have been taken yet by government agencies to reduce or prevent these impacts.

Further Research

Install sediment traps in sites along the transects.Measure pH and dissolved oxygen levels.Continue working on suspended solid measurements.Correlate environmental parameters with documented changes in coral reef communities.

References

• Yu-Chun Wu, Tzer-Min Lee, Kuo-Hsun Chin, Shyn-Tu Shaw & Chyun-Yu Yan, 2007. A Comparative Study of the Physical and Mechanical Properties of Three Natural Corals based on the Criteria for Bone-Tissue Engineering Scaffolds. Journal of Materials Science: Materials in Medicine 20(6): 1273- 1280

• P. Proksch, R. Edrada & R. Ebel, 2002. Drugs from the Seas: Current Status and Microbiological Implications. Applied Microbiology & Biotechnology 59(2-3): 125-134

• R.A. Pastorok & G. R. Bilyard, 1985. Effects of Sewage Pollution of Coral Reef Communitites. Mar. Ecol. Prog. Ser. 21: 175-189

Acknowledgements

Edwin Hernández Ph.D.Alejandra AlvaradoRicardo Laureano

The EPA (Environmental Protection Agency) GRO (Greater Research Opportunities) Fellowship Program. MA- 91721201-0Center for Applied Ecology and Conservation, Coral Reef Research Group.

I wish to extend a special thanks to the RISE program and its entire staff for their always enthusiastic support and guidance.