Understanding Growth and Age of Red Tree Corals (Primnoa pacifica) in the North Pacific Ocean.” PLOS One, vol. 15, issue 12, 2020,
, Emma, , Branwen Williams, Robert Stone, Peter Etnoyer, Ellen Druffel, Thomas Lorenson, and Mary Knaak. “
Abstract: Massive, long-lived deep-sea red tree corals (Primnoa pacifica) form a solid, layered axis comprised of calcite and gorgonin skeleton. They are abundant on the outer continental shelf and upper slope of
the Northeast Pacific, providing habitat for fish and invertebrates. Yet, their large size and arborescent morphology makes them susceptible to disturbance from fishing activities. A better understanding of their growth patterns will
facilitate in-situ estimates of population age structure and biomass. Here, we evaluated relationships between ages, growth rates, gross morphological characteristics, and banding patterns in 11 colonies collected from depths of
~141–335 m off the Alaskan coast. These corals ranged in age from 12 to 80 years old. They grew faster radially (0.33–0.74 mm year-1) and axially (2.41–6.39 cm year-1) than in previously measured older colonies,
suggesting that growth in P. pacifica declines slowly with age, and that basal diameter and axial height eventually plateau. However, since coral morphology correlated with age in younger colonies (< century), we
developed an in-situ age estimation technique for corals from the Northeast Pacific Ocean providing a non-invasive method for evaluating coral age without removing colonies from the population. Furthermore, we determined that
annual bands provided the most accurate means for determining coral age in live-collected corals, relative to radiometric dating. Taken together, this work provides insight into P. pacifica growth patterns to inform
coastal managers about the demographics of this ecologically important species. With this new ability to estimate the age of red tree corals in-situ, we can readily determine the age-class structure and consequently, the maturity
status of thickets, using non-invasive video survey techniques when coupled with mensuration systems such as lasers or stereo-cameras. Enhanced surveys could identify which populations are most vulnerable to disturbance from human
activities, and which should be highlighted for protection.
Fu, Franck, Kathleen L. Purvis-Roberts, and Branwen Williams. "Impact of Covid-19 Pandemic Lockdown on PM, Ozone, SO2, NO2 and CO in 20 Major Cities around the World.”
Atmosphere, vol. 11, 2020, 1189.
Abstract: In order to fight against the spread of COVID-19, the most hard-hit countries in the spring of 2020 implemented different lockdown strategies. To assess the impact of the COVID-19 pandemic lockdown on air
quality worldwide, Air Quality Index (AQI) data was used to estimate the change in air quality in 20 major cities on six continents. Our results show significant declines of AQI in NO2, SO2, CO, PM2.5 and PM10 in most cities, mainly due to
the reduction of transportation, industry and commercial activities during lockdown. This work shows the reduction of primary pollutants, especially NO2, is mainly due to lockdown policies. However, preexisting local environmental policy
regulations also contributed to declining NO2, SO2 and PM2.5 emissions, especially in Asian countries. In addition, higher rainfall during the lockdown period could cause decline of PM2.5, especially in Johannesburg. By contrast, the
changes of AQI in ground-level O3 were not significant in most of cities, as meteorological variability and ratio of VOC/NOx are key factors in ground-level O3 formation.
Hargan, Kathryn E., Branwen Williams, Bunlung Nuangsaeng, Sarawut Siriwong, Pisut Tassawad, Chatdanai Chaiharn, Brian McAdoo, and Marc Los Huertos. “Understanding the Fate of Shrimp Aquaculture
Effluent in a Mangrove Ecosystem: Aiding Management for Coastal Conservation.” Journal of Applied Ecology, vol. 57, issue 4, 2020, pp. 754-765.
Abstract: Areas dedicated to shrimp aquaculture have increased dramatically over the last 50 years. Resultant land‐use changes directly threaten the extent of mangroves and yield conflicts on the discharge location of
aquaculture effluent. Khung Krabaen Bay (KBB), Thailand, is reforesting mangroves while increasing the efficiency of shrimp aquaculture for local farmers. In this coupled shrimp farm–mangrove system, effective management requires
understanding the fate of aquaculture organic matter (OM) in the coastal environment. We examined carbon and nitrogen stable isotope ratios (δ13C, δ15N) in primary producers and pools of particulate and sediment OM
(POM, SOM) from the KKB mangrove and marine ecosystem to determine how shrimp aquaculture OM contributes to the coastal environment. Here, soy‐based shrimp feed resulted in low shrimp δ15N, similar to marine POM, and thus we
focus on the use of δ13C in tracking shrimp pond effluent in the environment. δ13C signatures of SOM varied significantly along a land‐to‐ocean gradient (–29.1‰ to –23.9‰). We found consistently depleted mangrove SOM
δ13C signatures (–29.4‰ to –28.2‰) indicating that mangrove leaf litter is the primary source of OM to mangrove sediments, and there is little evidence that marine and shrimp pond OM contributes to the mangrove habitat. In
contrast, relatively low δ13C values for marine SOM (–25.7‰ to –23.9‰) overlap with the δ13C of shrimp feed (–25.3‰) and Bayesian mixing models indicate that shrimp aquaculture feed and mangrove vegetation contribute
the greatest OM to the marine ecosystem. Compared to 20 years ago, marine SOM δ13C signatures are depleted by ~10‰ and similar throughout KKB, indicating a homogenization of marine SOM carbon sources from 1998 to 2018.
Synthesis and applications. The doubling of shrimp aquaculture in Khung Krabaen Bay (KKB) since 1998 led to increased discharge to the bay, swamping organic matter (OM) contributions from 13C‐enriched seagrasses and
marine plankton. Because of this increase in effluent release to KKB, the chemical impact is likely to be greater for the marine ecosystem than the mangrove and should also be a focus of conservation efforts. Continued technological
improvements (e.g. closed systems, better feed efficiency) and support to local aquaculture farmers will help reduce OM discharge to coastal ecosystems and promote sustainable farming practices.
Examining Molluscs as Bioindicators of Shrimp Aquaculture Effluent Contamination in a Southeast Asian Mangrove.” Ecological Indicators, vol. 115,
, Kathryn E. Hargan, Branwen Williams, Bunlung Nuangsaeng, Sarawut Siriwong, Pisut Tassawad, Chatdanai Chaiharn, and Marc Los Huertos. “
Abstract: This study evaluates the presence of metal(loid) contamination from shrimp aquaculture effluent in a nearby mangrove ecosystem in Khung Krabaen Bay (KKB), Thailand. Our objectives were to: 1) examine how sediment
metal(loid) concentrations change spatially in KKB relative to the aquaculture ponds; (2) compare mollusc trophic dynamics of elements associated with shrimp aquaculture; and (3) determine if certain mangrove mollusc species present better
ecological indicators of aquaculture elemental contamination. We analyzed targeted elemental concentrations (As, Mn, Cu, Zn, Cr, Pb) in sediments sampled at increasing distance from intensive shrimp aquaculture and within the tissues of
five species of molluscs. Differences in mollusc diet were studied using carbon (ẟ13C) and nitrogen (ẟ15N) stable isotopes, and biomagnification and biodilution of metal(loid)s were examined using ẟ15N
values to infer trophic position. Elemental concentrations were low in farmed shrimp and pellet food relative to mangrove molluscs, but high in the sediments of drainage ponds filtering pond effluent. Declining elemental concentrations from
the aquaculture drainage ponds to the mangrove sediments closest to shrimp farms suggested that the management settling ponds are effective at attenuating metal(loid) contamination. Large differences in mollusc mean ẟ13C (–25.8
to –20.1‰) and ẟ15N (1.9 to 8.3‰) values indicate variable diets across species, and trophically-elevated molluscs had greater marine-based diets resulting in a significant, positive correlation between mollusc ẟ13C
and ẟ15N values. KKB molluscs biomagnify As, Zn, and Se, whereas declines in Mn and Cu with increasing trophic position indicate biodilution. The metals Pb, Fe, Al, Cr were elevated in the shrimp drainage pond sediments and in
the tissues of the gastropods Ellobium aurisjudae, Cerithidea obtusa (both mud grazing), and Nerita lineata (algal grazing at low tide), identifying these gastropod species as probable bioindicators of aquaculture
contamination in southeast Asian mangroves. Although we find biomagnification of some elements, mangrove mollusc metal(loid) concentrations are not likely to be of toxicological concern, and in fact, were lower than many mangroves elsewhere
impacted by industrial and sewage contamination.
Stewart, Joseph A., Laura F. Robinson, Russell D. Day, Ivo Strawson, Andrea Burke, James W.B. Rae, Peter T. Spooner, Ana Samperiz, Peter J. Etnoyer, Branwen Williams, Adina Paytan, Melanie J. Leng, Vreni Häussermann, Leslie N. Wickes,
Rachael Bratt, and Helena Pryer. “Refining Trace Metal Temperature Proxies in Cold-Water Scleractinian and Stylasterid Corals.” Earth and Planetary
Science Letters, vol. 545, 2020, 116412.
Abstract: The Li/Mg, Sr/Ca and oxygen isotopic (O) compositions of many marine biogenic carbonates are sensitive to seawater temperature. Corals, as cosmopolitan marine taxa with carbonate skeletons that can be precisely
dated, represent ideal hosts for these geochemical proxies. However, efforts to calibrate and refine temperature proxies in cold-water corals (<20 °C) remain limited. Here we present skeletal Li/Mg, Sr/Ca, O and carbon isotope (C)
data from live-collected specimens of aragonitic scleractinian corals (Balanophyllia, Caryophyllia, Desmophyllum, Enallopsammia, Flabellum, Lophelia, and Vaughanella), both aragonitic and high-Mg calcitic stylasterid
genera (Stylaster and Errina), and shallow-water high-Mg calcite crustose coralline algae (Lithophyllum, Hydrolithon, and Neogoniolithon). We interpret these data in conjunction with results from
previously explored taxa including aragonitic zooxanthellate scleractinia and foraminifera, and high-Mg calcite octocorals. We show that Li/Mg ratios covary most strongly with seawater temperature, both for aragonitic and high-Mg calcitic
taxa, making for reliable and universal seawater temperature proxies. Combining all of our biogenic aragonitic Li/Mg data with previous calibration efforts we report a refined relationship to temperature: Li/MgAll
Aragonite = (). This calibration now permits paleo-temperature reconstruction to better than ±3.4 °C (95% prediction intervals) across biogenic aragonites, regardless of taxon, from 0 to 30 °C. For taxa in this study,
aragonitic stylasterid Li/Mg offers the most robust temperature proxy (Li/MgStylasterid (Arag) = ()) with a reproducibility of ±2.3 °C. For the first time, we show that high-Mg calcites have a similar exponential
relationship with temperature, but with a lower intercept value (Li/Mg = ()). This calibration opens the possibility of temperature reconstruction using high-Mg calcite corals and coralline algae. The commonality in the relationship between
Li/Mg and temperature transcends phylogeny and suggests a similar abiogenic trace metal incorporation mechanism.
Williams, Branwen. “Proteinaceous Corals as Proxy Archives
of Paleo-Environmental Change.” Earth Science Reviews, vol. 209, 2020, pp. 103326.
Abstract: High-resolution marine data are critical to evaluating anthropogenic impacts on our environment. Considering the spatial and temporal limitations of direct instrumental measurements, proxy data extracted from
marine environmental archives are necessary to separate anthropogenic changes from those that would occur naturally. The majority of late-Holocene, high resolution environmental reconstructions are derived from marine carbonates including
tropical scleractinian corals, bivalves, crustose coralline algae, and sclerosponges. However, these archives are restricted to the top hundreds of meters of the water column, and only preserve environmental variability that is captured by
calcium carbonate skeletons. At a very few select locations, marine sediments archive annual environmental variability in organic and inorganic materials. Recently, additional types of corals are proving to yield information complimentary
to these traditional marine archives, including cold water scleractinian corals and proteinaceous corals. A taxonomically-diverse group, the proteinaceous corals are broadly defined as those having a branching gross-morphology with skeleton
comprised at least partly of protein-rich organic material. They encode characteristics of their food and ambient environment into the chemical and physical composition of their skeleton. This environmental-encoding combined with their
banded skeleton and significant longevity means that proteinaceous corals hold information in their skeleton that helps fill the spatial and temporal gaps in our knowledge of past and present ocean conditions.
External Grant: Williams, Branwen, Principal Investigator. “Collaborative Research: Using Multi-Proxy Paleo Data to Constrain Natural and
Anthropogenic Hydrographic Variability in the Gulf of Maine System over the Last 250 years.” National Science Foundation, NSF OCE #2028219, 2020-2023, $157,736.00.
Abstract: The Gulf of Maine is located in the Northwestern Atlantic Ocean. Its waters serve as home to the economically important Atlantic Cod and shellfish industry. But recent changes to this environment pose a threat to
the ecosystem and the commercial fishing industry. However, only a few long-term records of the environment exist in this area making it difficult to tell exactly when these changes started and how much is related to human activities. In
this project, a team of researchers from three universities will construct a 250-year history of the regional environment by measuring yearly growth bands in local clams and algae. Chemical fingerprints in these growth bands will be used to
determine the water temperature, salinity, biological productivity and pH conditions. This allow scientists to study how natural changes have affected the environment and compare these to changes caused by greenhouse global warming. This
information will inform policy decisions of the newly-formed Maine Climate Council on how to better manage this area. The proposed work will also support training for early career scientists, broaden participation in science programs, and
support undergraduate research opportunities. Specifically, the team will use a multi-pronged approach using geochemical proxies in two types of high-resolution marine climate archives (clams and crustose coralline algae) to reconstruct
past changes in oceanographic conditions, including near surface seawater temperatures, salinity, and pH in the Gulf of Maine through the last 250 years. Geochemical fingerprints (or proxies) preserved in the annual growth bands of clam
shells and skeletons of long-lived marine calcifiers have been used extensively as archives of past ocean conditions. Discrete calcium carbonate layers can be sampled from the growth bands of clams and crustose coralline algae for
geochemical analysis, generating proxy archive records. These reconstructions of past environmental conditions fill data gaps prior to instrumental records. Hence, the proposed research will potentially yield several multi-centennial,
annually-resolved, absolutely-dated datasets of oceanographic variability in the Northwestern Atlantic, including the Gulf of Maine, prior to the Industrial Revolution, which will be used to evaluate the role of Atlantic meridional
overturning circulation, and other climate forcings, on observed changes. By combining new data derived from traditional and novel proxies with existing hydrographic records, the relative contributions of source waters into the Gulf of
Maine through time will be characterized to better understand the drivers of variability within the Gulf of Maine. Understanding past oceanographic variability in the Gulf of Maine is therefore critical for predicting the likely extent and
magnitude of future change, and for planning to safeguard ecosystems and fisheries. Results will be widely disseminated to science and non-science audiences through publications, conference presentations, mentoring programs, coursework, and
outreach activities at area schools, museums, and science centers.