Larval ecology and synchronous reproduction of two crustacean species : Semibalanus balanoides in New England, USA and Gecarcinus quadratus in Veraguas, Panama

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2011The environmental cues for synchronous reproduction were investigated for two highly abundant, ecologically important crustacean species: the temperate acorn barnacle, Semibalanus balanoides, and the tropical terrestrial crab, Gecarcinus quadratus. Larval ecology of these two species was also studied to determine potential sources of larval mortality and recruitment success. High-frequency observations revealed that early-stage larval abundance of S. balanoides was related to storms, and possibly turbidity. Field observations and experiments studied the effect of turbidity and phytoplankton on larval release response. Release coincided with increased turbidity at three sites along the northeast coast of the United States. A three-year time series of phytoplankton and zooplankton data showed that larval release was not consistently related to phytoplankton abundance (total or single species). When gravid barnacles were exposed to phytoplankton or synthetic beads, they released in response to both, suggesting that presence of particles is more important than identity of particles. Feeding experiments showed that adult cannibalism on newly released larvae is lower in highly turbid conditions. It is suggested here that S. balanoides synchronizes its reproduction with the onset of phytoplankton blooms, but turbidity may fine-tune the timing if it provides predation refuge for larvae. Adult G. quadratus females undertake synchronized breeding migrations to the ocean after the first rains of the rainy season, presumably when the risk of desiccation is lowest. They wait for darkness and an ebbing tide before releasing their eggs into the water. First-stage zoeas have dark pigmentation, long dorsal and rostral spines, and a pair of lateral spines. Hatching in darkness may help zoeas avoid predation from planktivorous diurnal fish, and the zoeal spines may deter predation from planktivorous nocturnal fish. In the laboratory, a G. quadratus zoea reached the megalopa stage in 21 days. A mass migration of megalopae and juveniles out of the water was observed 30 days after adult females released their eggs. Plankton pump samples taken near the island suggest that zoea abundance and distribution may be related to the phase of the internal tide. Synchronous reproduction in these two species appears to be the result of predator avoidance behaviors.My funding was provided by a National Science Foundation Graduate Research Fellowship, three WHOI Ocean Life Institute grants (Grant # 27071337, 27071342, and 25051361), two WHOI Coastal Ocean Institute grants (Grant # 32031022 and 27040136), and financial support from the WHOI Academic Programs Office

Turbidity triggers larval release by the intertidal barnacle Semibalanus balanoides

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marien Ecology Progress Series 476 (2013): 141-151, doi:10.3354/meps10186.Gravid adults of the common intertidal barnacle Semibalanus balanoides (L.) brood fully developed larvae until individuals perceive some cue from the environment that triggers synchronous larval release. The prevailing hypothesis has been that phytoplankton blooms trigger release because they provide a food source for nauplius larvae. Through observations and field experiments, we tested the hypothesis that turbidity from any source, not just phytoplankton blooms, can trigger release. We documented five larval release events at three sites in the northeastern United States. Two events coincided with chlorophyll increases, and all five coincided with turbidity increases. In experiments, the larval release response was equivalent when adults were exposed to diatoms or inert synthetic beads, and it was significantly higher than under exposure to filtered seawater. We also tested the hypothesis that turbidity can decrease the risk of cannibalism for newly-released nauplii. Under experimentally manipulated conditions, adults consumed significantly fewer nauplii in a high-turbidity environment. We suggest that reproduction in this species may have evolved to coincide roughly with the local onset of winter/spring phytoplankton blooms, but the timing of larval release may have been fine-tuned further by cannibalism and predation pressures. The potential for turbid conditions to serve as a refuge for planktonic larvae of other marine organisms merits further investigation.Support for this work came from a National Science Foundation Graduate Research Fellowship and a student award from the Coastal Ocean Institute at Woods Hole Oceanographic Institution (both to JG)

Did the political climate exacerbate the pandemic in the U.S.?

The global pandemic that began in the United States in early 2020 continues to be a topic of controversy. The added aspect of affect polarization in the country’s political realm may have exacerbated the effects of COVID-19. In their published article in Nature Human Behaviour, Gollwitzer et. al. found that it was possible to link voting partisanship, physical distancing, and COVID-19 outcomes showing that a county’s partisanship might be used to predict the degree to which that county would socially distance and then, therefore, the rate of cases and fatalities in that error on a lagged timescale. This researcher attempted to replicate and validate the findings of an analysis conducted in the earliest months of the pandemic using approximately the same variables, models, and covariates, but over a longer span of time in the pandemic. Three possible mediator variables (physical distancing data, mask mandate data, and online sentiment data) were gathered and tested for usability in the main mediation analysis. Preliminary analysis of the data gathered did not support the assertion of sentiment or masking data would be useful to the mediation analysis due to insufficient data. Though the distancing data was significantly linked to partisanship to become a proxy, mixed models showed that pandemic dates after the period of the original analysis could not support physical distancing as a mediator for partisanship. Only the segment of the final dataset which matched the dates of the original work were processed through the same mediation analysis in STATA. Significant effects of partisanship on case growth rates were discovered, but not to the same degree as the original work

The role of season and salinity in influencing barnacle distributions in two adjacent coastal mangrove lagoons

Author Posting. © University of Miami - Rosenstiel School of Marine and Atmospheric Science, 2011. This article is posted here by permission of University of Miami - Rosenstiel School of Marine and Atmospheric Science for personal use, not for redistribution. The definitive version was published in Bulletin of Marine Science 87 (2011): 275-299, doi:10.5343/bms.2010.1022.Barnacles are often abundant on roots and branches of mangrove trees in tidal channels and coastal lagoons of the Pacific coast of Panama. Yet, in some coastal lagoons, barnacles are absent. We investigated pre- and post-settlement factors that affect barnacle distributions in two adjacent coastal lagoons in Bahía Honda, Panama, one with moderate to large barnacle populations, and the other with nearly non-existent populations. Although mean barnacle recruitment was higher on mangrove root segments during the dry season (December-April) than in the wet season (May-November), it was not significantly different between the two coastal lagoons. The coastal lagoon with fewer barnacles is considered an estuary, with high freshwater flow and low salinities (0.1) during the wet season that were lethal to barnacle nauplii and cyprids. Furthermore, coastal water was not observed to enter the lagoon, even during flood tides. In contrast, more barnacles were found in the lagoon with higher salinities (8.5). During the dry season, freshwater flow was greatly reduced in both lagoons, resulting in a similar salinity range (22-33). We conclude that the lack of barnacles in the estuarine coastal lagoon is largely due to high flushing rates and low salinities that reduce larval concentrations during the wet season. Moreover, low adult abundance in the lagoon's interior may further reduce larval supply and settlement.Finally, we would like to thank the Ocean Life Institute of the Woods Hole Oceanographic Institution for funding to JP to complete research in the Liquid Jungle Lab.2014-07-0

Story grammar recovery: The first 2 years post-TBI (Greenslade et al., 2024)

Purpose: Narration within a story grammar framework requires speakers to organize characters and events logically. Despite abundant research characterizing narrative deficits following a traumatic brain injury (TBI), the evolution of narrative story grammar over the first 2 years post-TBI has rarely been explored. This study analyzed story grammar in complex narratives of adults with and without severe TBI to (a) examine between-group differences and (b) investigate longitudinal changes over the first 2 years post-TBI.Method: Story grammar analyses of Cinderella narratives from 57 participants with TBI and 57 participants with no brain injury yielded measures of productivity (total number of episodes, total number of story grammar elements), elaboration (total number of elaborated–complete episodes, mean number of episodic elements per episode), and completeness (total number of incomplete episodes). Mann–Whitney U tests compared measures across groups; generalized estimating equation (GEE) models identified predictors of change, including recovery time (3, 6, 9, 12, and 24 months post-TBI) and demographic/injury-related characteristics.Results: Between-group differences were statistically significant for all productivity and elaboration measures at 3, 6, and 9 months post-TBI; one productivity measure and one elaboration measure at 12 months; and none of the measures at 24 months. GEE models showed significant improvements in all productivity and elaboration measures over the first 24 months post-TBI, with educational attainment and duration of posttraumatic amnesia affecting recovery. Incomplete episodes only showed between-group differences at 12 months and did not capture recovery.Conclusion: Productivity and elaboration are key story grammar variables that (a) differentiate complex narration in individuals with and without severe TBI and (b) capture narrative improvements over the first 2 years post-TBI.Supplemental Material S1. Sex comparisons in the NBI group for each narrative variable.Greenslade, K. J., Bogart, E., Gyory, J., Jaskolka, S., & Ramage, A. E. (2024). Story grammar analyses capture discourse improvement in the first 2 years following a severe traumatic brain injury. American Journal of Speech-Language Pathology, 33(2), 1004–1020. https://doi.org/10.1044/2023_AJSLP-23-00269</p

Seasonal Variability in Calorimetric Energy Content of Two Caribbean Mesophotic Corals

<div><p>Energetic responses of zooxanthellate reef corals along depth gradients have relevance to the refugia potential of mesophotic coral ecosystems (MCEs). Previous observations suggested that MCEs in the Caribbean are thermally buffered during the warmest parts of the year and occur within or just below the chlorophyll maximum, suggesting abundant trophic resources. However, it is not known if mesophotic corals can maintain constant energy needs throughout the year with changing environmental and biological conditions. The energetic content of tissues from the stony coral species <i>Orbicella faveolata</i> and <i>Agaricia lamarcki</i> was measured on the southern insular shelf of St. Thomas, US Virgin Islands (USVI), using micro-bomb calorimetry. Three sites for each species, at depths of 6m, 25m, 38m and 63m, were selected to capture energetic differences across the major vertical range extent of both species in the USVI—and sampled over five periods from April 2013 to April 2014. Mesophotic colonies of <i>O</i>. <i>faveolata</i> exhibited a significant reduction in energetic content during the month of September 2013 compared to mid-depth and shallow colonies (p = 0.032), whereas <i>A</i>. <i>lamarcki</i> experienced similar energetic variability, but with a significant reduction in energy content that occurred in July 2013 for colonies at sites deeper than 25m (p = 0.014). The results of calorimetric analyses indicate that <i>O</i>. <i>faveolata</i> may be at risk during late summer stress events, possibly due to the timing of reproductive activities. The low-point of <i>A</i>. <i>lamarcki</i> energy content, which may also coincide with reproduction, occurs prior to seasonal stress events, indicating contrasting, species-specific responses to environmental variability on MCEs.</p></div

Environmental Characterization of Sampling Sites.

<p>PAR, chl-a fluorescence and temperature at sampling locations. Data points indicate the mean value taken within one meter of the sampling depth indicated in the legend.</p

ANOVA Results.

<p>ANOVA Results.</p

Mesophotic Chlorophyll Fluorescence.

<p>Mean daily Chlorophyl-a fluorescence at Grammanik Bank and Ginsburgs Fringe from 9/21/13 to 11/19/13. Shaded regions represent daily standard deviation.</p