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Seasonal rainfall and runoff promote coral disease on an inshore reef.

Haapkylä J, Unsworth RK, Flavell M, Bourne DG, Schaffelke B, Willis BL - PLoS ONE (2011)

Bottom Line: Declining water quality coupled with the effects of climate change are rapidly increasing coral diseases on reefs worldwide, although links between coral diseases and environmental parameters remain poorly understood.The results suggest that rainfall and associated runoff may facilitate seasonal disease outbreaks, potentially by reducing host fitness or by increasing pathogen virulence due to higher availability of nutrients and organic matter.In the future, rainfall and seawater temperatures are likely to increase due to climate change which may lead to decreased health of inshore reefs.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Coral Reef Studies, School of Marine and Tropical Biology, James Cook University, Townsville, Australia. Jessica.Haapkyla@jcu.edu.au

ABSTRACT

Background: Declining water quality coupled with the effects of climate change are rapidly increasing coral diseases on reefs worldwide, although links between coral diseases and environmental parameters remain poorly understood. This is the first study to document a correlation between coral disease and water quality on an inshore reef.

Methodology/principal findings: The temporal dynamics of the coral disease atramentous necrosis (AN) was investigated over two years within inshore populations of Montipora aequituberculata in the central Great Barrier Reef, in relation to rainfall, salinity, temperature, water column chlorophyll a, suspended solids, sedimentation, dissolved organic carbon, and particulate nitrogen, phosphorus and organic carbon. Overall, mean AN prevalence was 10-fold greater during summer wet seasons than winter dry seasons. A 2.5-fold greater mean disease abundance was detected during the summer of 2009 (44 ± SE 6.7 diseased colonies per 25 m(2)), when rainfall was 1.6-fold greater than in the summer of 2008. Two water quality parameters explained 67% of the variance in monthly disease prevalence in a Partial Least Squares regression analysis; disease abundance was negatively correlated with salinity (R2 = -0.6) but positively correlated with water column particulate organic carbon concentration (R2 = 0.32). Seasonal temperature patterns were also positively correlated with disease abundance, but explained only a small portion of the variance.

Conclusions/significance: The results suggest that rainfall and associated runoff may facilitate seasonal disease outbreaks, potentially by reducing host fitness or by increasing pathogen virulence due to higher availability of nutrients and organic matter. In the future, rainfall and seawater temperatures are likely to increase due to climate change which may lead to decreased health of inshore reefs.

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Temporal patterns in environmental variables.Temporal patterns in (a) salinity and rainfall, (b) daily mean sea water                            temperature combining temperatures from both bays, (c) ash-free dry                            weight of sediment (AFDW), (d) suspended solids (SS), (e) dissolved                            organic carbon (DOC), (f) chlorophyll a                                (chl-a), (g) particulate organic carbon (POC), (h)                            particulate nitrogen (PN), and (i) particulate phosphorus (PP) during                            the two-year study in Nelly and Geoffrey Bays. Values represent means of                            two samples at each study site. (NB = dark circles,                            GB = white circles).
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pone-0016893-g004: Temporal patterns in environmental variables.Temporal patterns in (a) salinity and rainfall, (b) daily mean sea water temperature combining temperatures from both bays, (c) ash-free dry weight of sediment (AFDW), (d) suspended solids (SS), (e) dissolved organic carbon (DOC), (f) chlorophyll a (chl-a), (g) particulate organic carbon (POC), (h) particulate nitrogen (PN), and (i) particulate phosphorus (PP) during the two-year study in Nelly and Geoffrey Bays. Values represent means of two samples at each study site. (NB = dark circles, GB = white circles).

Mentions: The highest values for both mean abundance of diseased colonies and mean disease incidence corresponded with the highest values in all of the environmental parameters investigated except for salinity, for which the lowest values were recorded at the disease peak (Fig. 2 and 4). An increasing trend in environmental parameters (decreasing for salinity) was observed preceding the disease outbreaks in both years, with values tending to be higher in 2009 than in 2008. The summer of 2009 was the wettest in 10 years in the Townsville region, with a total rainfall of 1901.6 mm compared to 1187 mm in 2008. A dramatic (∼40%) decrease in salinity over four weeks was observed in 2009 prior to the disease outbreak (from 31.7 to 19.0 in NB, and from 32.3 to 20.1 in GB). Salinity data prior to the 2008 outbreak are lacking because measurements for this study started in February 2008. Sedimentation was very seasonal, with higher values during summer rain events, especially in 2009. Mean water temperatures increased by only 0.3°C (to 30.5°C) in the month prior to the disease outbreak in 2008, whereas temperatures increased by 1.7°C in the month prior to the 2009 outbreak and reached 31.7°C. The highest value of particulate nitrogen (PN) was observed one month prior to the 2008 outbreak, with lower and more even distribution of recorded values in 2009. Particulate phosphorus (PP) showed 10-fold higher values two weeks prior to the 2009 outbreak and particulate organic carbon (POC) values were higher in 2009 than in 2008 (Fig. 4, Table 1).


Seasonal rainfall and runoff promote coral disease on an inshore reef.

Haapkylä J, Unsworth RK, Flavell M, Bourne DG, Schaffelke B, Willis BL - PLoS ONE (2011)

Temporal patterns in environmental variables.Temporal patterns in (a) salinity and rainfall, (b) daily mean sea water                            temperature combining temperatures from both bays, (c) ash-free dry                            weight of sediment (AFDW), (d) suspended solids (SS), (e) dissolved                            organic carbon (DOC), (f) chlorophyll a                                (chl-a), (g) particulate organic carbon (POC), (h)                            particulate nitrogen (PN), and (i) particulate phosphorus (PP) during                            the two-year study in Nelly and Geoffrey Bays. Values represent means of                            two samples at each study site. (NB = dark circles,                            GB = white circles).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3037388&req=5

pone-0016893-g004: Temporal patterns in environmental variables.Temporal patterns in (a) salinity and rainfall, (b) daily mean sea water temperature combining temperatures from both bays, (c) ash-free dry weight of sediment (AFDW), (d) suspended solids (SS), (e) dissolved organic carbon (DOC), (f) chlorophyll a (chl-a), (g) particulate organic carbon (POC), (h) particulate nitrogen (PN), and (i) particulate phosphorus (PP) during the two-year study in Nelly and Geoffrey Bays. Values represent means of two samples at each study site. (NB = dark circles, GB = white circles).
Mentions: The highest values for both mean abundance of diseased colonies and mean disease incidence corresponded with the highest values in all of the environmental parameters investigated except for salinity, for which the lowest values were recorded at the disease peak (Fig. 2 and 4). An increasing trend in environmental parameters (decreasing for salinity) was observed preceding the disease outbreaks in both years, with values tending to be higher in 2009 than in 2008. The summer of 2009 was the wettest in 10 years in the Townsville region, with a total rainfall of 1901.6 mm compared to 1187 mm in 2008. A dramatic (∼40%) decrease in salinity over four weeks was observed in 2009 prior to the disease outbreak (from 31.7 to 19.0 in NB, and from 32.3 to 20.1 in GB). Salinity data prior to the 2008 outbreak are lacking because measurements for this study started in February 2008. Sedimentation was very seasonal, with higher values during summer rain events, especially in 2009. Mean water temperatures increased by only 0.3°C (to 30.5°C) in the month prior to the disease outbreak in 2008, whereas temperatures increased by 1.7°C in the month prior to the 2009 outbreak and reached 31.7°C. The highest value of particulate nitrogen (PN) was observed one month prior to the 2008 outbreak, with lower and more even distribution of recorded values in 2009. Particulate phosphorus (PP) showed 10-fold higher values two weeks prior to the 2009 outbreak and particulate organic carbon (POC) values were higher in 2009 than in 2008 (Fig. 4, Table 1).

Bottom Line: Declining water quality coupled with the effects of climate change are rapidly increasing coral diseases on reefs worldwide, although links between coral diseases and environmental parameters remain poorly understood.The results suggest that rainfall and associated runoff may facilitate seasonal disease outbreaks, potentially by reducing host fitness or by increasing pathogen virulence due to higher availability of nutrients and organic matter.In the future, rainfall and seawater temperatures are likely to increase due to climate change which may lead to decreased health of inshore reefs.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Coral Reef Studies, School of Marine and Tropical Biology, James Cook University, Townsville, Australia. Jessica.Haapkyla@jcu.edu.au

ABSTRACT

Background: Declining water quality coupled with the effects of climate change are rapidly increasing coral diseases on reefs worldwide, although links between coral diseases and environmental parameters remain poorly understood. This is the first study to document a correlation between coral disease and water quality on an inshore reef.

Methodology/principal findings: The temporal dynamics of the coral disease atramentous necrosis (AN) was investigated over two years within inshore populations of Montipora aequituberculata in the central Great Barrier Reef, in relation to rainfall, salinity, temperature, water column chlorophyll a, suspended solids, sedimentation, dissolved organic carbon, and particulate nitrogen, phosphorus and organic carbon. Overall, mean AN prevalence was 10-fold greater during summer wet seasons than winter dry seasons. A 2.5-fold greater mean disease abundance was detected during the summer of 2009 (44 ± SE 6.7 diseased colonies per 25 m(2)), when rainfall was 1.6-fold greater than in the summer of 2008. Two water quality parameters explained 67% of the variance in monthly disease prevalence in a Partial Least Squares regression analysis; disease abundance was negatively correlated with salinity (R2 = -0.6) but positively correlated with water column particulate organic carbon concentration (R2 = 0.32). Seasonal temperature patterns were also positively correlated with disease abundance, but explained only a small portion of the variance.

Conclusions/significance: The results suggest that rainfall and associated runoff may facilitate seasonal disease outbreaks, potentially by reducing host fitness or by increasing pathogen virulence due to higher availability of nutrients and organic matter. In the future, rainfall and seawater temperatures are likely to increase due to climate change which may lead to decreased health of inshore reefs.

Show MeSH
Related in: MedlinePlus