Richard Aronson | Florida Institute of Technology (original) (raw)

Papers by Richard Aronson

Japan Geoscience Union, 2019

This study aims to reveal the sedimentation process of the barrier reef lagoon in the Eastern Kum... more This study aims to reveal the sedimentation process of the barrier reef lagoon in the Eastern Kume Island. We drilled at two sites (the south of Ooha island and the east of Eef beach)in Kume Island and obtained 4 cores. The penetration depth of cores were from 2.4 to 4.2 m. Unlithified sediments in coral reef lagoons in Kume Island were mainly composed of bioclast such as branching coral pebbles, foraminifera, shell, algae and lime mud. We measured radiocarbon dating of 28 samples (18 coral pebbles and 10 foraminifera) in the cores and estimated their sedimentation rates. The results showed that the sedimentation rate was slow at the south of Ooha Island, but rapid at Eef beach. The timing of rapid sediment accumulation at Ooha Island coincided with the timing of relative sea-level rise around 6.7 ka and reached its highest level at Tonaki Island (Kan et al.,1997) locating next to Kume Island. The sediment accumulation at Eef Beach was from 4.1 to 3.2 ka and it lagged behind Ooha Is...

Acta Biomaterialia, 2020

The decapod crustacean exoskeleton is a multi-layered structure composed of chitin-protein fibers... more The decapod crustacean exoskeleton is a multi-layered structure composed of chitin-protein fibers embedded with calcium salts. Decapod claws display tooth-like denticles, which come into direct contact with predators and prey. They are subjected to more regular and intense mechanical stress than other parts of the exoskeleton and therefore must be especially resistant to wear and abrasion. Here, we characterized denticle properties in five decapod species. Dactyls from three brachyuran crabs (Cancer borealis, Callinectes sapidus, and Chionoecetes opilio) and two anomuran crabs (Paralomis birsteini and Paralithodes camtschaticus) were sectioned normal to the contact surface of the denticle, revealing the interior of the denticle and the bulk endocuticle in which it is embedded. Microhardness, micro-and ultrastructure, and elemental composition were assessed along a transect running the width of the cuticle using microindentation hardness testing, optical and electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS), respectively. In all species tested, hardness was dramatically higher-up to ten times-in the denticle than in the bulk endocuticle. Likewise, in all species there was an increase in packing density of mineralized chitin-protein fibers, a decrease in width of the pore canals that run through the cuticle, and a decrease in phosphorous content from endocuticle to denticle. The changes in hardness across the cuticle, and the relationship between hardness, calcium, and magnesium content, however, varied among species. Although mechanical resistance of the denticles was exceptionally high in all species, the basis for resistance appears to differ among species.

$Research paper thumbnail of Self-organized criticality and the fractal scaling of a predator-prey interaction$

The Paleontological Society Special Publications, 1992

In many cases, it is not possible to explain evolutionary-scale patterns by analogy to ecological... more In many cases, it is not possible to explain evolutionary-scale patterns by analogy to ecological processes. However, in at least some cases, biological interactions appear amenable to such extrapolation. The paleobiological literature contains examples of predation, competition, and herbivory in which the dynamics are similar on multiple spatiotemporal scales.Dense populations of epifaunal, suspension-feeding ophiuroids, or brittlestar beds, are widely distributed, but they are rare and are restricted in their habitat distribution. On a small scale (meters to kilometers, hours to days), brittlestar bed distribution in the British Isles and the Bahamas is limited by predatory fishes and crabs. On an intermediate scale (tens to hundreds of kilometers, decades to centuries), predation by seastars may cause cycles of ophiuroid abundance in the western English Channel, beyond the stringent restrictions imposed by fish and crab predators. On a large scale (globally, millions to tens of m...

The Paleontological Society Special Publications, 2014

Nature Climate Change, 2018

In the version of this Letter originally published, the x axes titles of Fig. 3 erroneously read ... more In the version of this Letter originally published, the x axes titles of Fig. 3 erroneously read 'Latitude'; they should have read 'Longitude'. This has been corrected in the online versions of the Letter.

Royal Society Open Science, 2018

The fossil record from Seymour Island, Antarctic Peninsula, provides a record of biotic response ... more The fossil record from Seymour Island, Antarctic Peninsula, provides a record of biotic response to the onset of global climatic cooling during the Eocene. Using drilling traces—small, round holes preserved on prey shells—we examined the effect of a cooling pulse 41 Ma on the cannibalistic behaviour of predatory naticid gastropods. We predicted that cannibalistic attacks would decline in response to the cooling climate, reflecting reduced activity levels, energy requirements and constraints on the chemically aided drilling process of the naticids. Surprisingly, however, cannibalism frequencies did not change. This counterintuitive result is best explained by a sharp reduction in durophagous (shell-crushing) predation in shallow-benthic communities in Antarctica that also occurred as the climate cooled. Reduced durophagous predation may have created a less-risky environment for foraging naticids, stimulating cannibalistic behaviour. The change in the top-down control exerted by shell...

Coral Reefs of the World, 2016

At small spatial and temporal scales reefs are non-equilibrial, dynamic, disturbance-dominated ec... more At small spatial and temporal scales reefs are non-equilibrial, dynamic, disturbance-dominated ecosystems. At larger scales, however, the community structure of coral reefs appears stable; coral assemblages from the same environments exhibit striking similarities in species composition and dominance on time scales of decades to hundreds of thousands years. Thus, community membership over time is commonly more stable and persistent than that expected by chance alone. In both the Caribbean and Indo-Pacific, patterns of zonation observed on modern reefs are faithfully recorded in fossil reef sequences preserved through successive Pleistocene high-stands of sea level. Many paleoecologists, however, view the changes in both sea level and sea-surface temperature (SST) recorded during Pleistocene glaciations as major disturbance events requiring community reassembly de novo after each event. Why did reef communities respond in a repetitive fashion to the frequent and supposedly large environmental fluctuations of the Ice Ages?

Palaeobiology II

... The variety of their trackways, however, records various other locomotor styles (eg half-swim... more ... The variety of their trackways, however, records various other locomotor styles (eg half-swimming). Some of the largest arthropod trackways known from the fossil record are attributed to eurypterids. Most eurypterid trackways are rare, apart from Palmichnium antarcticum (Fig. ...

Paleoceanography, 2015

Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in t... more Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño-Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene. Seasonal, wind-driven upwelling occurs in three locations where topographic lows in the Central American Cordillera allow strong easterly wind jets to reach the eastern Pacific: the Gulf of Tehuantepec in Mexico, the Gulf of Papagayo in Costa Rica, and the Gulf of Panamá (Figure 1a). During the boreal winter, persistent winds of~6 m s À1 and wind bursts up to 30 m s À1 occur in these "wind-gap" systems. Surface mixing and thermocline shoaling depress water temperatures [

Frontiers of Biogeography, 2019

Benthic assemblages of the Antarctic continental shelf are dominated by sessile and slow-moving, ... more Benthic assemblages of the Antarctic continental shelf are dominated by sessile and slow-moving, epifaunal invertebrates. This community structure persists because shell-crushing (durophagous) predators are absent or ecologically insignificant in shelf habitats. Durophagous teleosts, elasmobranchs, and crustaceans have been excluded by cold waters over the Antarctic shelf for millions of years. Now, as shallow waters warm rapidly, predatory king crabs (Lithodidae) living in the upper bathyal zone could emerge onto the shelf and into nearshore habitats. To assess the potential for a bathymetric expansion, we genetically inferred the historical demography of a population of the most abundant durophagous predator found in deep water off the western Antarctic Peninsula: the lithodid Paralomis birsteini Macpherson. Analysis of mitochondrial DNA sequences from crabs sampled at 1200-1400 m depth on the slope off Marguerite Bay suggests this population has expanded twice over the past 132,000 years. Those expansions were possibly coincident with episodes of climatic warming in Antarctica and elsewhere, raising the possibility of a third expansion in response to anthropogenic climate change.

Graph on the left shows the Eocene paleotemperature curve derived from the La Meseta For... more Graph on the left shows the Eocene paleotemperature curve derived from the La Meseta Formation at Seymour Island, based on mean oxygen-isotope values of shell material from two bivalve genera. Error bars represent standard deviations. Ages of horizons and the inferred presence of a middle Eocene unconformity are based on strontium-isotope stratigraphy (redrawn from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004385#pone.0004385-Ivany1" target="_blank">[10]</a>). Icons on the right denote dense, autochthonous or parautochthonous fossil concentrations that represent abundant paleopopulations of rhynchonelliform brachiopods, Bouchardia antarctica; stalked crinoids, Metacrinus fossilis; unstalked (comatulid) crinoids, Notocrinus rasmusseni; and ophiuroids, Ophiura hendleri. Paleontological data are based on surveys conducted in 1986, 1994, 2000, and 2001.</p

These two axes represent 73.4% of the total variation in the correlation matrix. Indepen... more These two axes represent 73.4% of the total variation in the correlation matrix. Independent variables listed on each axis indicate variables with significant eigenvector loadings. Abbreviations for variables are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010835#pone-0010835-t002" target="_blank">Table 2</a>. Mean S. planifrons densities are given for each site (n = 6 transects per site).</p

Journal of Foraminiferal Research, 2020

The marginal marine environments of the eastern tropical Pacific (ETP) serve as an ideal natural ... more The marginal marine environments of the eastern tropical Pacific (ETP) serve as an ideal natural laboratory to study how oceanographic and climatic variability influence coral-reef ecosystems. Reefs along the Pacific coast of Panamá span a natural gradient of nutrients, pH, and temperature as a result of stronger seasonal upwelling in the Gulf of Panamá relative to the Gulf of Chiriquí. The ecosystems are not only influenced by spatial and seasonal variations in oceanography but are affected by the climatic variability of the El Niño-Southern Oscillation (ENSO). Foraminifera can be robust indicators of ecosystem condition because the composition of their assemblages and the geochemistry of their tests can change rapidly in response to environmental variability. We studied benthic foraminifera in sediment samples collected from 3 m below mean sea level in the Gulf of Panamá and the Gulf of Chiriquí. Temperature loggers deployed from 2016 to 2019 showed that average temperatures were ...

ANOVA tables, discussed in Results, for counts of juvenile corals, counts of Echinometra viridis,... more ANOVA tables, discussed in Results, for counts of juvenile corals, counts of Echinometra viridis, and the proportional cover of macroalgae at Channel Cay, Belize.

This manuscript sets out to explore the relationship between an accretion hiatus in a Panamanian ... more This manuscript sets out to explore the relationship between an accretion hiatus in a Panamanian coral reef (and reef growth hiatuses in other locations) and the 4.2ka event. The manuscript puts forward that the two are linked via changes in mid to late Holocene El Niño-Southern Oscillation (ENSO) variability. The co-timing and possible inter-relatedness of the Panama reef growth hiatus and the 4.2ka event is an intriguing possibility, however the narrow focus of the manuscript on ENSO as the cause is problematic. As the manuscript discusses, two out of the three major El Niño events of the past 40 years did not result in major mass coral death in the tropical eastern Pacific, La Niña events may or may not also lead to coral death in the region, and the relationship may be indirect (e.g. via Acanthaster outbreaks). Furthermore there is mixed evidence that there has even been a change in ENSO over the time period

Coral Reefs of the Eastern Tropical Pacific, 2016

Contrary to early assessments, the eastern tropical Pacific (ETP) is not devoid of well-developed... more Contrary to early assessments, the eastern tropical Pacific (ETP) is not devoid of well-developed reefs. Significant accumulations of Holocene reef framework are present throughout the region, although they tend to be poorly consolidated, lack the submarine cementation common on most reefs elsewhere in the world, and are subject to considerable bioerosion. These reef frameworks began accreting as early as 7000 years ago. The thickest accumulations of Pocillopora frameworks occur in coastal areas of Mexico, Costa Rica, Panama, and Colombia, but reefs composed of massive corals—species of Porites, Pavona, or Gardineroseris—are present throughout the region. Reef development in the ETP is limited by a variety of characteristics of the physical environment. Because of high turbidity in most areas, reef development is generally restricted to less than ~10 m depth. The spatial extent of reefs in the ETP is also limited from the combined influences of wave action and upwelling. Most reefs in the ETP are only a few hectares in size and the best-developed reefs generally occur in areas sheltered from strong oceanic influence. Upwelling also influences long-term trends in reef development in the region. There does not appear to be a significant impact of upwelling on the millennial-scale growth rates of Panamanian reefs; however, reefs in upwelling environments typically have thinner frameworks than nearby reefs in non-upwelling environments. Furthermore, upwelling may have contributed to a historic shutdown of reef development in Costa Rica and Panama. Although both ecological and oceanographic disturbances have had some impact on the long-term development of reefs in the ETP, the most important control on reef development in this region throughout the Holocene has most likely been the El Nino–Southern Oscillation (ENSO). ENSO activity—especially that of the 1982–83 and 1997–98 El Nino events—has shaped the landscape of coral reefs across the ETP both in recent decades and in the past. Reefs in Pacific Panama and Costa Rica experienced a 2500-year hiatus in vertical growth beginning ~4100 years ago as a result of enhanced ENSO activity. Although the degree of framework accumulation and rate of reef accretion in some parts of the ETP are more similar to that of the western Atlantic than previously thought, the region still remains a marginal environment for reef development. Given the dominant role that climatic variability has played in controlling reef development in the past, the future of reefs in the ETP under accelerating climate change remains uncertain.

Advances in Marine Biology, 2020

Caribbean reefs have experienced unprecedented changes in the past four decades. Of great concern... more Caribbean reefs have experienced unprecedented changes in the past four decades. Of great concern is the perceived widespread shift from coral to macroalgal dominance and the question of whether it represents a new, stable equilibrium for coral-reef communities. The primary causes of the shift-grazing pressure (top-down), nutrient loading (bottom-up) or direct coral mortality (side-in)-still remain somewhat controversial in the coral-reef literature. We have attempted to tease out the relative importance of each of these causes. Four insights emerge from our analysis of an early regional dataset of information on the benthic composition of Caribbean reefs spanning the years 1977-2001. First, although three-quarters of reef sites have experienced coral declines concomitant with macroalgal increases, fewer than 10% of the more than 200 sites studied were dominated by macroalgae in 2001, by even the most conservative definition of dominance. Using relative dominance as the threshold, a total of 49 coral-to-macroalgae shifts were detected. This total represents ~35% of all sites that were dominated by coral at the start of their monitoring periods. Four shifts (8.2%) occurred because of coral loss with no change in macroalgal cover, 15 (30.6%) occurred because of macroalgal gain without coral loss, and 30 (61.2%) occurred owing to concomitant coral decline and macroalgal increase. Second, the timing of shifts at the regional scale is most consistent with the side-in model of reef degradation, which invokes coral mortality as a precursor to macroalgal takeover, because more shifts occurred after regional coral-mortality events than expected by chance. Third, instantaneous observations taken at the start and end of the time-series for individual sites showed these reefs existed along a continuum of coral and macroalgal cover. The continuous, broadly negative relationship between coral and macroalgal cover suggests that in some cases coral-to-macroalgae phase shifts may be reversed by removing sources of perturbation or restoring critical components such as the herbivorous sea urchin Diadema antillarum to the system. The five instances in which macroalgal dominance was reversed corroborate the conclusion that macroalgal dominance is not a stable, alternative community state as has been commonly assumed. Fourth, the fact that the loss in regional coral cover and concomitant changes to the benthic community are related to punctuated, discrete events with known causes (i.e. coral disease and bleaching), lends credence to the hypothesis that coral reefs of the Caribbean have been under assault from climate-change-related maladies since the 1970s.

Climate of the Past Discussions, 2018

Variability of sea-surface temperature related to shifts in the mode of the El Niño-Southern Osci... more Variability of sea-surface temperature related to shifts in the mode of the El Niño-Southern Oscillation (ENSO) has been implicated as a possible forcing mechanism for the changes in global-scale, tropical and subtropical precipitation known as the 4.2-ka event. We explore records of coral-reef development and paleoceanography from the tropical eastern Pacific (TEP) to evaluate the potential impact of the 4.2-ka event on coral reefs. Our goal is to identify the 10 regional climatic and oceanographic drivers of a 2500-year shutdown of vertical reef accretion in the TEP beginning 4.2 ka. The 2500-year hiatus represents ~40% of the Holocene history of reefs in the TEP and was tied to increased variability of ENSO. When ENSO variability abated approximately 1.7-1.6 ka, coral populations recovered and vertical accretion of reef framework resumed apace. The 4.2-ka event appears to have suppressed coral populations and reef accretion elsewhere in the Pacific Ocean as well. Although the ultimate causality behind the global 4.2-ka 15 event remains elusive, correlations between shifts in ENSO variability and the impacts of the 4.2-ka event suggest that ENSO played a role in climatic changes at that time, at least in the tropical and subtropical Pacific. We outline a framework for testing hypotheses of where and under what conditions ENSO may be expected to have impacted coralreef environments around 4.2 ka. Although most studies of the 4.2-ka event have focused on terrestrial environments, we suggest that understanding the event in marine systems may prove to be the key to deciphering its ultimate cause. 20 25 Although the signature of the 4.2-ka event is not as ubiquitous as the north-Atlantic cooling episode known as the 8.2-ka event, which is the demarcation between the early and middle Holocene, it is now clear that the 4.2-ka event had global climatic, ecological, and cultural impacts (Mayewski et al., 2004; Weiss, 2016). In most locations, the 4.2-ka event was manifested as extreme and abrupt changes in terrestrial hydroclimate (Straubwasser et al., 2003;

Evolutionary Paleoecology, 2001