Paul Jokiel - Academia.edu (original) (raw)
Papers by Paul Jokiel
PeerJ, 2015
Nine coral survey methods were compared at ten sites in various reef habitats with different leve... more Nine coral survey methods were compared at ten sites in various reef habitats with different levels of coral cover in Kāne'ohe Bay, O'ahu, Hawai'i. Mean estimated coverage at the different sites ranged from less than 10% cover to greater than 90% cover. The methods evaluated include line transects, various visual and photographic belt transects, video transects and visual estimates. At each site 25 m transect lines were laid out and secured. Observers skilled in each method measured coral cover at each site. The time required to run each transect, time required to process data and time to record the results were documented. Cost of hardware and software for each method was also tabulated. Results of this investigation indicate that all of the methods used provide a good first estimate of coral cover on a reef. However, there were differences between the methods in detecting the number of coral species. For example, the classic…
Until recently, subtropical Hawai‘i escaped the major bleaching events that have devastated many ... more Until recently, subtropical Hawai‘i escaped the major bleaching events that have
devastated many tropical regions, but the continued increases in global long-term
mean temperatures and the apparent ending of the Pacific Decadal Oscillation
(PDO) cool phase have increased the risk of bleaching events. Climate models and
observations predict that bleaching in Hawai‘i will occur with increasing frequency
and increasing severity over future decades. A freshwater “kill” event occurred during
July 2014 in the northern part of K¯ane‘ohe Bay that reduced coral cover by 22.5% in
the area directly impacted by flooding. A subsequent major bleaching event during
September 2014 caused extensive coral bleaching and mortality throughout the
bay and further reduced coral cover in the freshwater kill area by 60.0%. The high
temperature bleaching event only caused a 1.0% reduction in live coral throughout
the portion of the bay not directly impacted by the freshwater event. Thus, the
combined impact of the low salinity event and the thermal bleaching event appears
to be more than simply additive. The temperature regime during the September
2014 bleaching event was analogous in duration and intensity to that of the large
bleaching event that occurred previously during August 1996, but resulted in amuch
larger area of bleaching and coral mortality. Apparently seasonal timing as well as
duration and magnitude of heating is important. Coral spawning in the dominant
coral species occurs early in the summer, so reservoirs of stored lipid in the corals
had been depleted by spawning prior to the September 2014 event.Warm months
above 27 ◦C result in lower coral growth and presumably could further decrease
lipid reserves, leading to a bleaching event that was more severe than would have
happened if the high temperatures occurred earlier in the summer. Hawaiian reef
corals decrease skeletal growth at temperatures above 27 ◦C, so perhaps the “stress
period” actually started long before the bleaching threshold of 29 ◦C was reached.
Hawai‘i is directly influenced by the PDO which may become a factor influencing
bleaching events in subtropicalHawai‘i inmuch the same manner as variations in the
El Ni˜no Southern Oscillation (ENSO) influences bleaching events at low latitudes in
the tropical Pacific. Records show that offshore temperatures measured by satellite
will not always predict inshore bleaching because other factors (high cloud cover,
high wind and wave action, tidal exchange rate) can limit inshore heating and prevent
temperatures in the bay from reaching the bleaching threshold. Low light levels due
to cloud cover or high turbidity can also serve to prevent bleaching.
Ambient irradiance levels determine the rate of carbon influx into zooxanthellae at any given tim... more Ambient irradiance levels determine the rate of carbon influx into zooxanthellae at any given time, and thereby the energy available for the whole coral symbiotic association. Long-term photoacclimation of zooxanthellae to the time-averaged light regime at which the host coral grows results in optimization of light harvesting and utilization. Under high irradiance light harvesting is reduced, thereby avoiding photodynamic damage, whereas under low light, photon capture and quantum yield are maximized. Most of the photosynthate produced by the algae is respired. However, the capability of the zooxanthellae and the coral to retain carbon beyond that required to meet their respiratory needs depends on the availability of the commonly limiting nutrients, nitrogen and phosphorus. Therefore, the ratio of the flux of these nutrients into the colony to that of the photosynthetically driven carbon flux will regulate the growth of the zooxanthellae and ofthe animal. Nutrients acquired by predation of the coral on zooplankton are available first to the animal, whereas those absorbed by the zooxanthellae from seawater as inorganic compounds lead first to growth of the algae.
Major storms are infrequent events of high intensity and short duration that can exert a profound... more Major storms are infrequent events of high intensity and short duration that can exert a profound influence the structure of Hawaiian reefs. Extreme wave energy directly damages corals and retards coral community development. A paradox is that storm surf also represents a positive factor that maintains vitality of many communities through the mobilization and removal of terrigenous, calcareous and organic sediments that otherwise will smother a reef system. Flood events erode watersheds and deposit sediments on the reefs that can kill corals and block recruitment of new coral colonies. Fresh water delivered by storms also can lower local salinity to levels that are lethal to corals and other reef organisms. Nutrients and pollutants associated with fresh water runoff are transported onto coral reefs during such storms. The impact of these events is poorly understood for several reasons. These events are very transient in nature and seldom are observed directly on reefs due to difficulties in making observations during conditions of extreme wave motion or turbidity. The duration of most coral reef investigations is too short to allow evaluation of the major storm events that occur with a frequency of decades to hundreds of years. The pattern of impact for a major storm is highly complex, and influenced by local bathymetry, shoreline topography and directionality of the storm event. Nevertheless, sufficient data are available to provide a general spatial and temporal description of the relative importance of major storm waves and storm floods on reefs throughout the main Hawaiian Islands. The relative impact of wave damage, damage due to terrigenous sediment runoff and damage due to factors associated with fresh water are described for the major Hawaiian coral reef habitats.
Survival and settlement of Pocillopora damicornis larvae on hard surfaces covered with fine (<63 ... more Survival and settlement of Pocillopora damicornis larvae on hard surfaces covered with fine (<63 µm) terrigenous red clay was measured in laboratory Petri dishes. The dishes were prepared with sediment films of various thicknesses covering the bottoms. Coral larvae were incubated in the dishes for two weeks and the percent that settled on the bottom was determined. There was a statistically significant relationship between the amount of sediment and coral recruitment on the bottom, with no recruitment on surfaces having a sediment cover above 0.9 mg cm −2 . Experimental conditions for the delicate coral larvae were favorable in these experiments. Total survival over the two week settlement tests expressed as the sum of coral recruits and live larvae at the end of the experiment did not show a significant decline, so the major impact of the sediment was on successful settlement rather than on mortality. Larval substrate selection behavior was the primary factor in the observed result. How to cite this article Perez III et al. (2014), Effects of terrigenous sediment on settlement and survival of the reef coral Pocillopora damicornis. PeerJ 2:e387; . Davies PS et al. 2014. A cross-ocean comparison of responses to settlement cues in reef-building corals. PeerJ 2:e333 DOI 10.7717/peerj.333. DeMartini E, Jokiel P, Beets J, Stender Y, Storlazzi C, Minton D, Conklin E. 2012. Terrigenous sediment impact on coral recruitment and growth affects the use of coral habitat by recruit parrotfishes (F. Scaridae). Journal of Coast Conservation 17(3):417-429 . Gilmour J. 1999. Experimental investigation into the effects of suspended sediment on fertilisation, larval survival and settlement in a scleractinian coral. Marine Biology 135(3):451-462
An intensive research effort was organized as a 1-week workshop with the specific goal of resolvi... more An intensive research effort was organized as a 1-week workshop with the specific goal of resolving difficult questions concerning whether or not zooxanthellae are nutrient limited within host corals. Over 30 scientists participated. Participants applied various techniques to the same set of corals, which had been preincubated under different nutrient regimes for various time periods. Interdisciplinary research projects of this scale and intensity have rarely been attempted by coral reef biologists, yet the evidence developed during the workshop demonstrates the usefulness of this approach. This was a true "workshop" rather than a "talk-shop" and produced important research results while allowing participants to compare research methods and discuss various theories and research philosophies. Important new data were developed. Apparent contradictions were resolved through development of models that consider the dynamics of carbon fixation relative to nutrient avai...
The question of nutrient limitation and of its regulatory effect on population densities of zooxa... more The question of nutrient limitation and of its regulatory effect on population densities of zooxanthellae in hospice was studied by an international team of researchers during an intensive 5-day workshop. Participants studied colonies of two coral species that were preincubated over different time periods ranging from 0 to 8 weeks under four different nutrient concentrations. A broad spectrum of parameters was measured simultaneously at the molecular, cellular, and colony levels of organization using a variety of techniques. This paper describes the overall experimental design.
Integrative and Comparative Biology
Laboratory experiments were conducted to determine survival rates from the effects of sediment on... more Laboratory experiments were conducted to determine survival rates from the effects of sediment on planulae of the coral Pocillopora damicornis.
Biogeosciences Discussions, 2009
Acidification of seawater owing to oceanic uptake of atmospheric CO 2 originating from human acti... more Acidification of seawater owing to oceanic uptake of atmospheric CO 2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns for its adverse effects on corals, coral reefs and carbonate communities in general. Here we demonstrate a transition from net accumulation towards net loss 5 of calcium carbonate (CaCO 3 ) material owing to decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to present and future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC = CaCO 3 pro-10 duction -dissolution) was positive at 4.5 mmol CaCO 3 m −2 h −1 under ambient seawater pCO 2 conditions as opposed to negative at −0.1 mmol CaCO 3 m −2 h −1 under seawater conditions of double the ambient pCO 2 . These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. 15 2− 3 ). A 20 decrease of CO 2− 3 produces a drop in the seawater saturation state with respect to carbonate minerals (Ω), which is the quotient of the product of the seawater concentration of calcium and carbonate ions and an experimentally determined stoichiometric solubility product (Ω=[Ca 2+ ][CO 2− 3 ]/K * sp ). Simplified, the seawater carbonate saturation state index can provide information on the rates at which marine calcifiers can deposit 25 skeletons and shells of CaCO 3 , or the opposite, the rates of dissolution and disinte-2164 BGD production -dissolution) (e.g., Andersson et al., 2005) of a typical subtropical coral reef community including its sediments incubated in mesocosms over a complete, 24-h, diel cycle. 2 Methods Abstract 25 salinity/conductivity/temperature; ±0.1 • C; ±0.1 ppt), dissolved oxygen (YSI 95 Dissolved Oxygen Microelectrode Array Model; ±0.2 mg L −1 ), pH NBS (Accumet AP72 pH/mV/temperature meter and Oakton fully enclosed Ag/AgCl combination electrode; ±0.01 pH units), TA and nutrients (PO 3− 4 , NO − 2 , NO − 3 , NH 4 , Si(OH) 4 ; all data are 2166 Abstract 25
PeerJ, 2015
Until recently, subtropical Hawai'i escaped the major bleaching events that have devastat... more Until recently, subtropical Hawai'i escaped the major bleaching events that have devastated many tropical regions, but the continued increases in global long-term mean temperatures and the apparent ending of the Pacific Decadal Oscillation (PDO) cool phase have increased the risk of bleaching events. Climate models and observations predict that bleaching in Hawai'i will occur with increasing frequency and increasing severity over future decades. A freshwater "kill" event occurred during July 2014 in the northern part of Kāne'ohe Bay that reduced coral cover by 22.5% in the area directly impacted by flooding. A subsequent major bleaching event during September 2014 caused extensive coral bleaching and mortality throughout the bay and further reduced coral cover in the freshwater kill area by 60.0%. The high temperature bleaching event only caused a 1.0% reduction in live coral throughout the portion of the bay not directly impacted by the freshwater event. Thus, the combined impact of the low salinity event and the thermal bleaching event appears to be more than simply additive. The temperature regime during the September 2014 bleaching event was analogous in duration and intensity to that of the large bleaching event that occurred previously during August 1996, but resulted in a much larger area of bleaching and coral mortality. Apparently seasonal timing as well as duration and magnitude of heating is important. Coral spawning in the dominant coral species occurs early in the summer, so reservoirs of stored lipid in the corals had been depleted by spawning prior to the September 2014 event. Warm months above 27 °C result in lower coral growth and presumably could further decrease lipid reserves, leading to a bleaching event that was more severe than would have happened if the high temperatures occurred earlier in the summer. Hawaiian reef corals decrease skeletal growth at temperatures above 27 °C, so perhaps the "stress period" actually started long before the bleaching threshold of 29 °C was reached. Hawai'i is directly influenced by the PDO which may become a factor influencing bleaching events in subtropical Hawai'i in much the same manner as variations in the El Niño Southern Oscillation (ENSO) influences bleaching events at low latitudes in the tropical Pacific. Records show that offshore temperatures measured by satellite will not always predict inshore bleaching because other factors (high cloud cover, high wind and wave action, tidal exchange rate) can limit inshore heating and prevent temperatures in the bay from reaching the bleaching threshold. Low light levels due to cloud cover or high turbidity can also serve to prevent bleaching.
ICES Journal of Marine Science, 2015
The literature on ocean acidification (OA) contains a prevalent misconception that reduced organi... more The literature on ocean acidification (OA) contains a prevalent misconception that reduced organismal calcification rates in an acidifying ocean are driven by a reduction in carbonate ion (CO 2− 3 ) substrate availability (e.g. Omega or V). However, recent research in diverse organisms suggests that a reduction in seawater pH (i.e. increasing proton concentrations, [H + ]) is the most likely driver of reduced calcification rates in these organisms. OA leads to higher [H + ] in seawater which alters the proton gradient between internal cellular reservoirs and external bulk seawater, making it difficult for organisms to maintain pH homeostasis. Biologically mediated calcification is a complex process, so it is unlikely that simple CO 2− 3 substrate limitation is responsible for the observed decreases in calcification rates under OA conditions. Despite these inherent complexities, current predictions concerning the fate of calcifying organisms in an acidifying ocean have relied on the relationship between calcification rates and V. To more accurately predict how OA will affect the calcification of marine organisms, and consequently the global carbon cycle, we need to further elucidate the mechanisms driving observed decreases in calcification under acidified conditions.
Exposure (wave energy) was shown to be a significant factor in determining the structure of Hawai... more Exposure (wave energy) was shown to be a significant factor in determining the structure of Hawaiian benthic and fish communities.
I n Hawaii, coral reefs are subjected to a variety of natural and anthropo-genic stresses at seve... more I n Hawaii, coral reefs are subjected to a variety of natural and anthropo-genic stresses at several spatial and temporal scales (Grigg and Dollar, 1990). The intensity and duration of these factors can both directly and indirectly alter the physical and biological structure of the reef (Connell and others, 1997). Natural factors, such as acute wave disturbances (Dollar and Tribble, 1993), freshwater inputs (Jokiel and others, 1993), and preda-tor outbreaks (Done, 1992) can affect the shallow-water reef communities at small spatial (10 –100 m) and temporal (0 –1 yr) scales. Chronic dis-turbances, such as non-point source pollution, are more difficult to detect because changes to the community landscape are subtle and occur over longer time periods (Pastorok and Bilyard, 1985). How different types of disturbance influence coral community structure is only beginning to be understood and quantified (Edmunds, 2000). Disturbances can lead to a deteriorating or "unhealthy" coral...
Geochemistry, Geophysics, Geosystems, 2012
1] Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater te... more 1] Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater temperatures during skeletal deposition, but studies have shown additional variables may affect the ratio. Here we measured Sr/Ca in the reef coral Montipora capitata grown in six mesocosms continuously supplied with seawater from the adjacent reef flat. Three mesocosms were ambient controls, and three had seawater chemistry simulating "ocean acidification" (OA). We found that Sr/Ca was not affected by the OA treatment and neither was coral calcification for these small colonies (larger colonies did show an OA effect). The lack of OA effects allowed us to test the hypothesis that coral growth rate can affect Sr/Ca using the natural range in calcification rates of the corals grown at the same temperature. We found that Sr/Ca was inversely related to calcification rate (Sr/Ca = 9.385 À 0.0040 (calcification rate)). Using a previously published calibration curve for this species, a 22 mg d À1 colony À1 increase in calcification rate introduced a 1 C warmer temperature estimate, with the 27 corals reporting "temperatures" ranging from 24.9 to 28.9 C, with mean 26.6 AE 0.9 C standard deviation. Our results lend support to hypotheses invoking kinetic processes and growth rate to explain vital effects on Sr/Ca. However, uncertainty in the slope of the regression of Sr/Ca on calcification and a low R-squared value lead us to conclude that Sr/Ca could still be a useful proxy in this species given sufficient replication or by including growth rate in the calibration.
MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295), 2001
PeerJ, 2015
Nine coral survey methods were compared at ten sites in various reef habitats with different leve... more Nine coral survey methods were compared at ten sites in various reef habitats with different levels of coral cover in Kāne'ohe Bay, O'ahu, Hawai'i. Mean estimated coverage at the different sites ranged from less than 10% cover to greater than 90% cover. The methods evaluated include line transects, various visual and photographic belt transects, video transects and visual estimates. At each site 25 m transect lines were laid out and secured. Observers skilled in each method measured coral cover at each site. The time required to run each transect, time required to process data and time to record the results were documented. Cost of hardware and software for each method was also tabulated. Results of this investigation indicate that all of the methods used provide a good first estimate of coral cover on a reef. However, there were differences between the methods in detecting the number of coral species. For example, the classic…
Until recently, subtropical Hawai‘i escaped the major bleaching events that have devastated many ... more Until recently, subtropical Hawai‘i escaped the major bleaching events that have
devastated many tropical regions, but the continued increases in global long-term
mean temperatures and the apparent ending of the Pacific Decadal Oscillation
(PDO) cool phase have increased the risk of bleaching events. Climate models and
observations predict that bleaching in Hawai‘i will occur with increasing frequency
and increasing severity over future decades. A freshwater “kill” event occurred during
July 2014 in the northern part of K¯ane‘ohe Bay that reduced coral cover by 22.5% in
the area directly impacted by flooding. A subsequent major bleaching event during
September 2014 caused extensive coral bleaching and mortality throughout the
bay and further reduced coral cover in the freshwater kill area by 60.0%. The high
temperature bleaching event only caused a 1.0% reduction in live coral throughout
the portion of the bay not directly impacted by the freshwater event. Thus, the
combined impact of the low salinity event and the thermal bleaching event appears
to be more than simply additive. The temperature regime during the September
2014 bleaching event was analogous in duration and intensity to that of the large
bleaching event that occurred previously during August 1996, but resulted in amuch
larger area of bleaching and coral mortality. Apparently seasonal timing as well as
duration and magnitude of heating is important. Coral spawning in the dominant
coral species occurs early in the summer, so reservoirs of stored lipid in the corals
had been depleted by spawning prior to the September 2014 event.Warm months
above 27 ◦C result in lower coral growth and presumably could further decrease
lipid reserves, leading to a bleaching event that was more severe than would have
happened if the high temperatures occurred earlier in the summer. Hawaiian reef
corals decrease skeletal growth at temperatures above 27 ◦C, so perhaps the “stress
period” actually started long before the bleaching threshold of 29 ◦C was reached.
Hawai‘i is directly influenced by the PDO which may become a factor influencing
bleaching events in subtropicalHawai‘i inmuch the same manner as variations in the
El Ni˜no Southern Oscillation (ENSO) influences bleaching events at low latitudes in
the tropical Pacific. Records show that offshore temperatures measured by satellite
will not always predict inshore bleaching because other factors (high cloud cover,
high wind and wave action, tidal exchange rate) can limit inshore heating and prevent
temperatures in the bay from reaching the bleaching threshold. Low light levels due
to cloud cover or high turbidity can also serve to prevent bleaching.
Ambient irradiance levels determine the rate of carbon influx into zooxanthellae at any given tim... more Ambient irradiance levels determine the rate of carbon influx into zooxanthellae at any given time, and thereby the energy available for the whole coral symbiotic association. Long-term photoacclimation of zooxanthellae to the time-averaged light regime at which the host coral grows results in optimization of light harvesting and utilization. Under high irradiance light harvesting is reduced, thereby avoiding photodynamic damage, whereas under low light, photon capture and quantum yield are maximized. Most of the photosynthate produced by the algae is respired. However, the capability of the zooxanthellae and the coral to retain carbon beyond that required to meet their respiratory needs depends on the availability of the commonly limiting nutrients, nitrogen and phosphorus. Therefore, the ratio of the flux of these nutrients into the colony to that of the photosynthetically driven carbon flux will regulate the growth of the zooxanthellae and ofthe animal. Nutrients acquired by predation of the coral on zooplankton are available first to the animal, whereas those absorbed by the zooxanthellae from seawater as inorganic compounds lead first to growth of the algae.
Major storms are infrequent events of high intensity and short duration that can exert a profound... more Major storms are infrequent events of high intensity and short duration that can exert a profound influence the structure of Hawaiian reefs. Extreme wave energy directly damages corals and retards coral community development. A paradox is that storm surf also represents a positive factor that maintains vitality of many communities through the mobilization and removal of terrigenous, calcareous and organic sediments that otherwise will smother a reef system. Flood events erode watersheds and deposit sediments on the reefs that can kill corals and block recruitment of new coral colonies. Fresh water delivered by storms also can lower local salinity to levels that are lethal to corals and other reef organisms. Nutrients and pollutants associated with fresh water runoff are transported onto coral reefs during such storms. The impact of these events is poorly understood for several reasons. These events are very transient in nature and seldom are observed directly on reefs due to difficulties in making observations during conditions of extreme wave motion or turbidity. The duration of most coral reef investigations is too short to allow evaluation of the major storm events that occur with a frequency of decades to hundreds of years. The pattern of impact for a major storm is highly complex, and influenced by local bathymetry, shoreline topography and directionality of the storm event. Nevertheless, sufficient data are available to provide a general spatial and temporal description of the relative importance of major storm waves and storm floods on reefs throughout the main Hawaiian Islands. The relative impact of wave damage, damage due to terrigenous sediment runoff and damage due to factors associated with fresh water are described for the major Hawaiian coral reef habitats.
Survival and settlement of Pocillopora damicornis larvae on hard surfaces covered with fine (<63 ... more Survival and settlement of Pocillopora damicornis larvae on hard surfaces covered with fine (<63 µm) terrigenous red clay was measured in laboratory Petri dishes. The dishes were prepared with sediment films of various thicknesses covering the bottoms. Coral larvae were incubated in the dishes for two weeks and the percent that settled on the bottom was determined. There was a statistically significant relationship between the amount of sediment and coral recruitment on the bottom, with no recruitment on surfaces having a sediment cover above 0.9 mg cm −2 . Experimental conditions for the delicate coral larvae were favorable in these experiments. Total survival over the two week settlement tests expressed as the sum of coral recruits and live larvae at the end of the experiment did not show a significant decline, so the major impact of the sediment was on successful settlement rather than on mortality. Larval substrate selection behavior was the primary factor in the observed result. How to cite this article Perez III et al. (2014), Effects of terrigenous sediment on settlement and survival of the reef coral Pocillopora damicornis. PeerJ 2:e387; . Davies PS et al. 2014. A cross-ocean comparison of responses to settlement cues in reef-building corals. PeerJ 2:e333 DOI 10.7717/peerj.333. DeMartini E, Jokiel P, Beets J, Stender Y, Storlazzi C, Minton D, Conklin E. 2012. Terrigenous sediment impact on coral recruitment and growth affects the use of coral habitat by recruit parrotfishes (F. Scaridae). Journal of Coast Conservation 17(3):417-429 . Gilmour J. 1999. Experimental investigation into the effects of suspended sediment on fertilisation, larval survival and settlement in a scleractinian coral. Marine Biology 135(3):451-462
An intensive research effort was organized as a 1-week workshop with the specific goal of resolvi... more An intensive research effort was organized as a 1-week workshop with the specific goal of resolving difficult questions concerning whether or not zooxanthellae are nutrient limited within host corals. Over 30 scientists participated. Participants applied various techniques to the same set of corals, which had been preincubated under different nutrient regimes for various time periods. Interdisciplinary research projects of this scale and intensity have rarely been attempted by coral reef biologists, yet the evidence developed during the workshop demonstrates the usefulness of this approach. This was a true "workshop" rather than a "talk-shop" and produced important research results while allowing participants to compare research methods and discuss various theories and research philosophies. Important new data were developed. Apparent contradictions were resolved through development of models that consider the dynamics of carbon fixation relative to nutrient avai...
The question of nutrient limitation and of its regulatory effect on population densities of zooxa... more The question of nutrient limitation and of its regulatory effect on population densities of zooxanthellae in hospice was studied by an international team of researchers during an intensive 5-day workshop. Participants studied colonies of two coral species that were preincubated over different time periods ranging from 0 to 8 weeks under four different nutrient concentrations. A broad spectrum of parameters was measured simultaneously at the molecular, cellular, and colony levels of organization using a variety of techniques. This paper describes the overall experimental design.
Integrative and Comparative Biology
Laboratory experiments were conducted to determine survival rates from the effects of sediment on... more Laboratory experiments were conducted to determine survival rates from the effects of sediment on planulae of the coral Pocillopora damicornis.
Biogeosciences Discussions, 2009
Acidification of seawater owing to oceanic uptake of atmospheric CO 2 originating from human acti... more Acidification of seawater owing to oceanic uptake of atmospheric CO 2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns for its adverse effects on corals, coral reefs and carbonate communities in general. Here we demonstrate a transition from net accumulation towards net loss 5 of calcium carbonate (CaCO 3 ) material owing to decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to present and future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC = CaCO 3 pro-10 duction -dissolution) was positive at 4.5 mmol CaCO 3 m −2 h −1 under ambient seawater pCO 2 conditions as opposed to negative at −0.1 mmol CaCO 3 m −2 h −1 under seawater conditions of double the ambient pCO 2 . These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. 15 2− 3 ). A 20 decrease of CO 2− 3 produces a drop in the seawater saturation state with respect to carbonate minerals (Ω), which is the quotient of the product of the seawater concentration of calcium and carbonate ions and an experimentally determined stoichiometric solubility product (Ω=[Ca 2+ ][CO 2− 3 ]/K * sp ). Simplified, the seawater carbonate saturation state index can provide information on the rates at which marine calcifiers can deposit 25 skeletons and shells of CaCO 3 , or the opposite, the rates of dissolution and disinte-2164 BGD production -dissolution) (e.g., Andersson et al., 2005) of a typical subtropical coral reef community including its sediments incubated in mesocosms over a complete, 24-h, diel cycle. 2 Methods Abstract 25 salinity/conductivity/temperature; ±0.1 • C; ±0.1 ppt), dissolved oxygen (YSI 95 Dissolved Oxygen Microelectrode Array Model; ±0.2 mg L −1 ), pH NBS (Accumet AP72 pH/mV/temperature meter and Oakton fully enclosed Ag/AgCl combination electrode; ±0.01 pH units), TA and nutrients (PO 3− 4 , NO − 2 , NO − 3 , NH 4 , Si(OH) 4 ; all data are 2166 Abstract 25
PeerJ, 2015
Until recently, subtropical Hawai'i escaped the major bleaching events that have devastat... more Until recently, subtropical Hawai'i escaped the major bleaching events that have devastated many tropical regions, but the continued increases in global long-term mean temperatures and the apparent ending of the Pacific Decadal Oscillation (PDO) cool phase have increased the risk of bleaching events. Climate models and observations predict that bleaching in Hawai'i will occur with increasing frequency and increasing severity over future decades. A freshwater "kill" event occurred during July 2014 in the northern part of Kāne'ohe Bay that reduced coral cover by 22.5% in the area directly impacted by flooding. A subsequent major bleaching event during September 2014 caused extensive coral bleaching and mortality throughout the bay and further reduced coral cover in the freshwater kill area by 60.0%. The high temperature bleaching event only caused a 1.0% reduction in live coral throughout the portion of the bay not directly impacted by the freshwater event. Thus, the combined impact of the low salinity event and the thermal bleaching event appears to be more than simply additive. The temperature regime during the September 2014 bleaching event was analogous in duration and intensity to that of the large bleaching event that occurred previously during August 1996, but resulted in a much larger area of bleaching and coral mortality. Apparently seasonal timing as well as duration and magnitude of heating is important. Coral spawning in the dominant coral species occurs early in the summer, so reservoirs of stored lipid in the corals had been depleted by spawning prior to the September 2014 event. Warm months above 27 °C result in lower coral growth and presumably could further decrease lipid reserves, leading to a bleaching event that was more severe than would have happened if the high temperatures occurred earlier in the summer. Hawaiian reef corals decrease skeletal growth at temperatures above 27 °C, so perhaps the "stress period" actually started long before the bleaching threshold of 29 °C was reached. Hawai'i is directly influenced by the PDO which may become a factor influencing bleaching events in subtropical Hawai'i in much the same manner as variations in the El Niño Southern Oscillation (ENSO) influences bleaching events at low latitudes in the tropical Pacific. Records show that offshore temperatures measured by satellite will not always predict inshore bleaching because other factors (high cloud cover, high wind and wave action, tidal exchange rate) can limit inshore heating and prevent temperatures in the bay from reaching the bleaching threshold. Low light levels due to cloud cover or high turbidity can also serve to prevent bleaching.
ICES Journal of Marine Science, 2015
The literature on ocean acidification (OA) contains a prevalent misconception that reduced organi... more The literature on ocean acidification (OA) contains a prevalent misconception that reduced organismal calcification rates in an acidifying ocean are driven by a reduction in carbonate ion (CO 2− 3 ) substrate availability (e.g. Omega or V). However, recent research in diverse organisms suggests that a reduction in seawater pH (i.e. increasing proton concentrations, [H + ]) is the most likely driver of reduced calcification rates in these organisms. OA leads to higher [H + ] in seawater which alters the proton gradient between internal cellular reservoirs and external bulk seawater, making it difficult for organisms to maintain pH homeostasis. Biologically mediated calcification is a complex process, so it is unlikely that simple CO 2− 3 substrate limitation is responsible for the observed decreases in calcification rates under OA conditions. Despite these inherent complexities, current predictions concerning the fate of calcifying organisms in an acidifying ocean have relied on the relationship between calcification rates and V. To more accurately predict how OA will affect the calcification of marine organisms, and consequently the global carbon cycle, we need to further elucidate the mechanisms driving observed decreases in calcification under acidified conditions.
Exposure (wave energy) was shown to be a significant factor in determining the structure of Hawai... more Exposure (wave energy) was shown to be a significant factor in determining the structure of Hawaiian benthic and fish communities.
I n Hawaii, coral reefs are subjected to a variety of natural and anthropo-genic stresses at seve... more I n Hawaii, coral reefs are subjected to a variety of natural and anthropo-genic stresses at several spatial and temporal scales (Grigg and Dollar, 1990). The intensity and duration of these factors can both directly and indirectly alter the physical and biological structure of the reef (Connell and others, 1997). Natural factors, such as acute wave disturbances (Dollar and Tribble, 1993), freshwater inputs (Jokiel and others, 1993), and preda-tor outbreaks (Done, 1992) can affect the shallow-water reef communities at small spatial (10 –100 m) and temporal (0 –1 yr) scales. Chronic dis-turbances, such as non-point source pollution, are more difficult to detect because changes to the community landscape are subtle and occur over longer time periods (Pastorok and Bilyard, 1985). How different types of disturbance influence coral community structure is only beginning to be understood and quantified (Edmunds, 2000). Disturbances can lead to a deteriorating or "unhealthy" coral...
Geochemistry, Geophysics, Geosystems, 2012
1] Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater te... more 1] Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater temperatures during skeletal deposition, but studies have shown additional variables may affect the ratio. Here we measured Sr/Ca in the reef coral Montipora capitata grown in six mesocosms continuously supplied with seawater from the adjacent reef flat. Three mesocosms were ambient controls, and three had seawater chemistry simulating "ocean acidification" (OA). We found that Sr/Ca was not affected by the OA treatment and neither was coral calcification for these small colonies (larger colonies did show an OA effect). The lack of OA effects allowed us to test the hypothesis that coral growth rate can affect Sr/Ca using the natural range in calcification rates of the corals grown at the same temperature. We found that Sr/Ca was inversely related to calcification rate (Sr/Ca = 9.385 À 0.0040 (calcification rate)). Using a previously published calibration curve for this species, a 22 mg d À1 colony À1 increase in calcification rate introduced a 1 C warmer temperature estimate, with the 27 corals reporting "temperatures" ranging from 24.9 to 28.9 C, with mean 26.6 AE 0.9 C standard deviation. Our results lend support to hypotheses invoking kinetic processes and growth rate to explain vital effects on Sr/Ca. However, uncertainty in the slope of the regression of Sr/Ca on calcification and a low R-squared value lead us to conclude that Sr/Ca could still be a useful proxy in this species given sufficient replication or by including growth rate in the calibration.
MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295), 2001