Cohen Anne L.

Last Name

Cohen

First Name

Anne L.

ORCID

0000-0002-5570-780X

Full item page

Search Results

Now showing 1 - 20 of 81

Vulnerability of coral reefs to bioerosion from land-based sources of pollution

(John Wiley & Sons, 2017-12-01) Prouty, Nancy G. ; Cohen, Anne L. ; Yates, Kimberly K. ; Storlazzi, Curt D. ; Swarzenski, Peter W. ; White, Darla

Ocean acidification (OA), the gradual decline in ocean pH and [ inline image] caused by rising levels of atmospheric CO2, poses a significant threat to coral reef ecosystems, depressing rates of calcium carbonate (CaCO3) production, and enhancing rates of bioerosion and dissolution. As ocean pH and [ inline image] decline globally, there is increasing emphasis on managing local stressors that can exacerbate the vulnerability of coral reefs to the effects of OA. We show that sustained, nutrient rich, lower pH submarine groundwater discharging onto nearshore coral reefs off west Maui lowers the pH of seawater and exposes corals to nitrate concentrations 50 times higher than ambient. Rates of coral calcification are substantially decreased, and rates of bioerosion are orders of magnitude higher than those observed in coral cores collected in the Pacific under equivalent low pH conditions but living in oligotrophic waters. Heavier coral nitrogen isotope (δ15N) values pinpoint not only site-specific eutrophication, but also a sewage nitrogen source enriched in 15N. Our results show that eutrophication of reef seawater by land-based sources of pollution can magnify the effects of OA through nutrient driven-bioerosion. These conditions could contribute to the collapse of coastal coral reef ecosystems sooner than current projections predict based only on ocean acidification.
Tidal modulation of Sr/Ca ratios in a Pacific reef coral

(American Geophysical Union, 2004-08-21) Cohen, Anne L. ; Sohn, Robert A.

The strontium-to-calcium ratio (Sr/Ca) of reef coral skeleton is an important tool for reconstructing past sea surface temperatures (SSTs). However, the accuracy of paleoSSTs derived from fossil coral Sr/Ca is challenged by evidence that physiological processes influence skeletal chemistry. Here we show that water level variations from tidal forcing are correlated with changes in coral Sr/Ca that cannot be accounted for by changes in SST. Ion microprobe measurements of Sr/Ca ratios in a Pacific Porites lutea reveal high-frequency variations at periods of ~6, ~10, and ~25 days. The relationship between Sr/Ca and temperature on these short timescales does not follow trends observed at longer periods, indicating that an additional forcing is required to explain our observations. We demonstrate that Sr/Ca is correlated with both tidal water level variations and SST, and that their contributions to the Sr/Ca content of the skeleton vary as a function of period. We propose that water level influences Sr/Ca indirectly via modulation of photosynthetically-active radiation (PAR) that drives large changes in zooxanthellate photosynthesis.
Comment on “Equatorial Pacific coral geochemical records show recent weakening of the Walker circulation” by J. Carilli et al.

(John Wiley & Sons, 2015-05-18) Karnauskas, Kristopher B. ; Cohen, Anne L. ; Drenkard, Elizabeth J.

This article is a comment on Carilli et al. [2014] doi:10.1002/2014PA002683
Interpreting sea surface temperature from strontium/calcium ratios in Montastrea corals : link with growth rate and implications for proxy reconstructions

(American Geophysical Union, 2008-07-31) Saenger, Casey P. ; Cohen, Anne L. ; Oppo, Delia W. ; Hubbard, Dennis

We analyzed strontium/calcium ratios (Sr/Ca) in four colonies of the Atlantic coral genus Montastrea with growth rates ranging from 2.3 to 12.6 mm a−1. Derived Sr/Ca–sea surface temperature (SST) calibrations exhibit significant differences among the four colonies that cannot be explained by variations in SST or seawater Sr/Ca. For a single coral Sr/Ca ratio of 8.8 mmol mol−1, the four calibrations predict SSTs ranging from 24.0° to 30.9°C. We find that differences in the Sr/Ca–SST relationships are correlated systematically with the average annual extension rate (ext) of each colony such that Sr/Ca (mmol mol−1) = 11.82 (±0.13) – 0.058 (±0.004) × ext (mm a−1) – 0.092 (±0.005) × SST (°C). This observation is consistent with previous reports of a link between coral Sr/Ca and growth rate. Verification of our growth-dependent Sr/Ca–SST calibration using a coral excluded from the calibration reconstructs the mean and seasonal amplitude of the actual recorded SST to within 0.3°C. Applying a traditional, nongrowth-dependent Sr/Ca–SST calibration derived from a modern Montastrea to the Sr/Ca ratios of a conspecific coral that grew during the early Little Ice Age (LIA) (400 years B.P.) suggests that Caribbean SSTs were >5°C cooler than today. Conversely, application of our growth-dependent Sr/Ca–SST calibration to Sr/Ca ratios derived from the LIA coral indicates that SSTs during the 5-year period analyzed were within error (±1.4°C) of modern values.
Why corals care about ocean acidification : uncovering the mechanism

(Oceanography Society, 2009-12) Cohen, Anne L. ; Holcomb, Michael

Stony corals build hard skeletons of calcium carbonate (CaCO3) by combining calcium with carbonate ions derived, ultimately, from seawater. The concentration of carbonate ions relative to other carbonate species in seawater is rather low, so corals expend energy to raise the pH of seawater sequestered in an isolated, extracellular compartment where crystal growth occurs. This action converts plentiful bicarbonate ions to the carbonate ions required for calcification, allowing corals to produce CaCO3 about 100 times faster than it could otherwise form. It is this rapid and efficient production of CaCO3 crystals that enables corals to build coral reefs. Ocean acidification reduces the pH and thus the abundance of carbonate ions in seawater. Corals living in acidified seawater continue to produce CaCO3 and expend as much energy as their counterparts in normal seawater to raise the pH of the calcifying fluid. However, in acidified seawater, corals are unable to elevate the concentration of carbonate ions to the level required for normal skeletal growth. In several experiments, we found that boosting the energetic status of corals by enhanced heterotrophic feeding or moderate increases in inorganic nutrients helped to offset the negative impact of ocean acidification. However, this built-in defense is unlikely to benefit corals as levels of CO2 in the atmosphere continue to rise. Most climate models predict that the availability of inorganic nutrients and plankton in the surface waters where corals live will decrease as a consequence of global warming. Thus, corals and coral reefs may be significantly more vulnerable to ocean acidification than previously thought.
The impact of seawater saturation state and bicarbonate ion concentration on calcification by new recruits of two Atlantic corals

( 2010-11-05) de Putron, Samantha J. ; McCorkle, Daniel C. ; Cohen, Anne L. ; Dillon, A. B.

Rising concentrations of atmospheric CO2 are changing the carbonate chemistry of the oceans, a process known as ocean acidification (OA). Absorption of this CO2 by the surface oceans is increasing the amount of total dissolved inorganic carbon (DIC) and bicarbonate ion (HCO3 -) available for marine calcification, yet is simultaneously lowering the seawater pH and carbonate ion concentration ([CO3 2-]), and thus the saturation state of seawater with respect to aragonite (Ωar). We investigated the relative importance of [HCO3 -] versus [CO3 2-] for early calcification by new recruits (primary polyps settled from zooxanthellate larvae) of two tropical coral species, Favia fragum and Porites astreoides. The polyps were reared over a range of Ωar values, which were manipulated by both acid-addition at constant pCO2 (decreased total [HCO3 -] and [CO3 2-]) and by pCO2 elevation at constant alkalinity (increased [HCO3 -], decreased [CO3 2-]). Calcification after two weeks was quantified by weighing the complete skeleton (corallite) accreted by each polyp over the course of the experiment. Both species exhibited the same negative response to decreasing [CO3 2-] whether Ωar was lowered by acid-addition or by pCO2 elevation - calcification did not follow total DIC or [HCO3 -]. Nevertheless, the calcification response to decreasing [CO3 2-] was non-linear. A statistically significant decrease in calcification was only detected between Ωar = < 2.5 and Ωar = 1.1 – 1.5, where calcification of new recruits was reduced by 22 – 37 % per 1.0 decrease in Ωar. Our results differ from many previous studies that report a linear coral calcification response to OA, and from those showing that calcification increases with increasing [HCO3 -]. Clearly, the coral calcification response to OA is variable and complex. A deeper understanding of the biomineralization mechanisms and environmental conditions underlying these 3 variable responses is needed to support informed predictions about future OA impacts on corals and coral reefs.
Reduced calcification and lack of acclimatization by coral colonies growing in areas of persistent natural acidification

( 2013-05) Crook, Elizabeth D. ; Cohen, Anne L. ; Rebolledo-Vieyra, Mario ; Hernandez, Laura ; Paytan, Adina

As the surface ocean equilibrates with rising atmospheric CO2, the pH of surface seawater is decreasing with potentially negative impacts on coral calcification. A critical question is whether corals will be able to adapt or acclimate to these changes in seawater chemistry. We use high precision CT scanning of skeletal cores of Porites astreoides, an important Caribbean reef-building coral, to show that calcification rates decrease significantly along a natural gradient in pH and aragonite saturation (Ωarag). This decrease is accompanied by an increase in skeletal erosion and predation by boring organisms. The degree of sensitivity to reduced Ωarag measured on our field corals is consistent with that exhibited by the same species in laboratory CO2 manipulation experiments. We conclude that the Porites corals at our field site were not able to acclimatize enough to prevent the impacts of local ocean acidification on their skeletal growth and development, despite spending their entire lifespan in low pH, low Ωarag seawater.
Mid-Holocene, coral-based sea surface temperatures in the western tropical Atlantic

(American Geophysical Union, 2019-05-31) Rodriguez, Luis G. ; Cohen, Anne L. ; Ramirez, Wilson ; Oppo, Delia W. ; Pourmand, Ali ; Edwards, R. Lawrence ; Alpert, Alice ; Mollica, Nathaniel R.

The Holocene is considered a period of relative climatic stability, but significant proxy data‐model discrepancies exist that preclude consensus regarding the postglacial global temperature trajectory. In particular, a mid‐Holocene Climatic Optimum, ~9,000 to ~5,000 years BP, is evident in Northern Hemisphere marine sediment records, but its absence from model simulations raises key questions about the ability of the models to accurately simulate climate and seasonal biases that may be present in the proxy records. Here we present new mid‐Holocene sea surface temperature (SST) data from the western tropical Atlantic, where twentieth‐century temperature variability and amplitude of warming track the twentieth‐century global ocean. Using a new coral thermometer Sr‐U, we first developed a temporal Sr‐U SST calibration from three modern Atlantic corals and validated the calibration against Sr‐U time series from a fourth modern coral. Two fossil corals from the Enriquillo Valley, Dominican Republic, were screened for diagenesis, U‐series dated to 5,199 ± 26 and 6,427 ± 81 years BP, respectively, and analyzed for Sr/Ca and U/Ca, generating two annually resolved Sr‐U SST records, 27 and 17 years long, respectively. Average SSTs from both corals were significantly cooler than in early instrumental (1870–1920) and late instrumental (1965–2016) periods at this site, by ~0.5 and ~0.75 °C, respectively, a result inconsistent with the extended mid‐Holocene warm period inferred from sediment records. A more complete sampling of Atlantic Holocene corals can resolve this issue with confidence and address questions related to multidecadal and longer‐term variability in Holocene Atlantic climate.
A multicoral calibration method to approximate a universal equation relating Sr/Ca and growth rate to sea surface temperature

(American Geophysical Union, 2007-03-01) Goodkin, Nathalie F. ; Hughen, Konrad A. ; Cohen, Anne L.

Combining strontium-to-calcium ratios (Sr/Ca) with mean annual growth rates in Bermuda Diploria labyrinthiformis (brain corals) is shown to improve sea surface temperature (SST) calibrations relative to instrumental data. Growth-corrected Sr/Ca–SST calibrations based on single-coral colonies over the same calibration interval, however, are found to be poorly suited for application to data from different coral colonies. This raises concerns about the accuracy of SST reconstructions from fossil coral measurements that involve extrapolation beyond the range of values seen during the calibration period. Here we pursue a novel approach to this problem by incorporating data from multiple coral colonies into a single growth-corrected Sr/Ca–SST calibration equation, effectively expanding the range of modern values constraining the model. The use of a multiple-colony calibration model for reconstructing SST yields greater precision and accuracy relative to instrumental data than single-colony models, providing greater confidence for applications to fossil coral samples.
Adverse effects of ocean acidification on early development of squid (Doryteuthis pealeii)

(Public Library of Science, 2013-05-31) Kaplan, Maxwell B. ; Mooney, T. Aran ; McCorkle, Daniel C. ; Cohen, Anne L.

Anthropogenic carbon dioxide (CO2) is being absorbed into the ocean, altering seawater chemistry, with potentially negative impacts on a wide range of marine organisms. The early life stages of invertebrates with internal and external aragonite structures may be particularly vulnerable to this ocean acidification. Impacts to cephalopods, which form aragonite cuttlebones and statoliths, are of concern because of the central role they play in many ocean ecosystems and because of their importance to global fisheries. Atlantic longfin squid (Doryteuthis pealeii), an ecologically and economically valuable taxon, were reared from eggs to hatchlings (paralarvae) under ambient and elevated CO2 concentrations in replicated experimental trials. Animals raised under elevated pCO2 demonstrated significant developmental changes including increased time to hatching and shorter mantle lengths, although differences were small. Aragonite statoliths, critical for balance and detecting movement, had significantly reduced surface area and were abnormally shaped with increased porosity and altered crystal structure in elevated pCO2-reared paralarvae. These developmental and physiological effects could alter squid paralarvae behavior and survival in the wild, directly and indirectly impacting marine food webs and commercial fisheries.
Deglacial sea surface temperatures of the western tropical Pacific : a new look at old coral

(American Geophysical Union, 2004-12-30) Cohen, Anne L. ; Hart, Stanley R.

Using Secondary Ion Mass Spectrometry (SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149°W, 17°S), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 μm diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca–sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs ∼0.5°–1.5°C cooler during the Bølling-Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca-based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3°C) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth-dependent calibration yield Sr/Ca-derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic.
The challenges of detecting and attributing ocean acidification impacts on marine ecosystems

(Oxford University Press, 2020-08-09) Doo, Steve ; Kealoha, Andrea K. ; Andersson, Andreas ; Cohen, Anne L. ; Hicks, Tacey L. ; Johnson, Zackary I. ; Long, Matthew H. ; McElhany, Paul ; Mollica, Nathaniel R. ; Shamberger, Kathryn E. F. ; Silbiger, Nyssa J. ; Takeshita, Yuichiro ; Busch, D. Shallin

A substantial body of research now exists demonstrating sensitivities of marine organisms to ocean acidification (OA) in laboratory settings. However, corresponding in situ observations of marine species or ecosystem changes that can be unequivocally attributed to anthropogenic OA are limited. Challenges remain in detecting and attributing OA effects in nature, in part because multiple environmental changes are co-occurring with OA, all of which have the potential to influence marine ecosystem responses. Furthermore, the change in ocean pH since the industrial revolution is small relative to the natural variability within many systems, making it difficult to detect, and in some cases, has yet to cross physiological thresholds. The small number of studies that clearly document OA impacts in nature cannot be interpreted as a lack of larger-scale attributable impacts at the present time or in the future but highlights the need for innovative research approaches and analyses. We summarize the general findings in four relatively well-studied marine groups (seagrasses, pteropods, oysters, and coral reefs) and integrate overarching themes to highlight the challenges involved in detecting and attributing the effects of OA in natural environments. We then discuss four potential strategies to better evaluate and attribute OA impacts on species and ecosystems. First, we highlight the need for work quantifying the anthropogenic input of CO2 in coastal and open-ocean waters to understand how this increase in CO2 interacts with other physical and chemical factors to drive organismal conditions. Second, understanding OA-induced changes in population-level demography, potentially increased sensitivities in certain life stages, and how these effects scale to ecosystem-level processes (e.g. community metabolism) will improve our ability to attribute impacts to OA among co-varying parameters. Third, there is a great need to understand the potential modulation of OA impacts through the interplay of ecology and evolution (eco–evo dynamics). Lastly, further research efforts designed to detect, quantify, and project the effects of OA on marine organisms and ecosystems utilizing a comparative approach with long-term data sets will also provide critical information for informing the management of marine ecosystems.
Stress bands in Jarvis coral cores

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-11-04) Cohen, Anne L

The dataset contains historical coral reef bleaching events on Jarvis Island reconstructed from stress bands in Porites coral cores. Samples are collected between 2008 and 2016. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/775828
Coral and algae cover, coral richness, and coral diversity from coral reef sites sampled by small boats in the Palauan archipelago from 2011-2013

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-12-30) Cohen, Anne L ; de Putron, Samantha J. ; Karnauskas, Kristopher ; McCorkle, Daniel C ; Tarrant, Ann M.

Average coral and algae cover, coral richness, and coral diversity from 8 coral reef sites in Palau. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/520476
Dongsha Atoll Coral 45 Years Bimonthly Stable Isotope Data from cores collected on June 29, 2013 from 1968-2012

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-20) Cohen, Anne L. ; Ren, Abby

Dongsha Atoll Coral 45 Years Bimonthly Stable Isotope Data from cores collected on June 29, 2013 from 1968-2012 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/738318
Annual calcification histories for corals from ten Palau reef sites representing lagoon and barrier reef environments

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-08-02) Cohen, Anne L

Annual calcification histories for corals from ten Palau reef sites representing lagoon and barrier reef environments. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/707106
Porites calcification rates from Dongsha Atoll from cores collected on June 29, 2013 from 1954-2012

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-24) Cohen, Anne L. ; Ren, Abby

Porites calcification rates from Dongsha Atoll from cores collected on June 29, 2013 from 1954-2012. The two coral skeletal cores were collected from living Porites sp. colonies in June 2013 using an underwater pneumatic drill. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/738251
pH - Jarvis Island

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-11-04) Cohen, Anne L

This dataset contains pH measurements collected at the height of El Niño on 12-15 November 2015 and after severe El Niño conditions had subsided on 16-24 May 2016 for the west and east sides of Jarvis Island at 7-10 m depth. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/775838
Vulnerability of coral reefs to bioerosion from land-based sources of pollution using parameters quantified by computerized tomography.

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-06-07) Cohen, Anne L ; Prouty, Nancy

Coral Growth Parameters Quantified by Computerized Tomography (CT) for Growth Rate (cm/yr), Density (g/cm3), and Calcification Rates (g/cm2/yr), Percent Volume Erosion (%), Measured Bioerosion Rate (mg/ cm2/ yr), Predicted Bioerosion Rate (mg/cm2/ yr) Based on DeCarlo et al (2015). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/739309
Water Chemistry - Jarvis Island

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-11-04) Cohen, Anne L

This dataset contains information about discrete seawater samples collected from 2012-2016 on Jarvis Island for salinity, nutrients, total alkalinity (TA), and dissolved inorganic carbon (DIC) during each sampling period. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/775834

Cohen Anne L.

Last Name

First Name

ORCID

Filters

Author

Subject

Date

Type

Has files

Settings

Sort By

Results per page

Search Results