It’s about time: A synthesis of changing phenology in the Gulf of Maine ecosystem

The timing of recurring biological and seasonal environmental events is changing on a global scale relative to temperature and other climate drivers. This study considers the Gulf of Maine ecosystem, a region of high social and ecological importance in the Northwest Atlantic Ocean and synthesizes current knowledge of (a) key seasonal processes, patterns, and events; (b) direct evidence for shifts in timing; (c) implications of phenological responses for linked ecological-human systems; and (d) potential phenology-focused adaptation strategies and actions. Twenty studies demonstrated shifts in timing of regional marine organisms and seasonal environmental events. The most common response was earlier timing, observed in spring onset, spring and winter hydrology, zooplankton abundance, occurrence of several larval fishes, and diadromous fish migrations. Later timing was documented for fall onset, reproduction and fledging in Atlantic puffins, spring and fall phytoplankton blooms, and occurrence of additional larval fishes. Changes in event duration generally increased and were detected in zooplankton peak abundance, early life history periods of macro-invertebrates, and lobster fishery landings. Reduced duration was observed in winter-spring ice-affected stream flows. Two studies projected phenological changes, both finding diapause duration would decrease in zooplankton under future climate scenarios. Phenological responses were species-specific and varied depending on the environmental driver, spatial, and temporal scales evaluated. Overall, a wide range of baseline phenology and relevant modeling studies exist, yet surprisingly few document long-term shifts. Results reveal a need for increased emphasis on phenological shifts in the Gulf of Maine and identify opportunities for future research and consideration of phenological changes in adaptation efforts

Biodiversity in a changing climate: a synthesis of current and projected trends in the US

This paper provides a synthesis of the recent literature describing how global biodiversity is being affected by climate change and is projected to respond in the future. Current studies reinforce earlier findings of major climate-change-related impacts on biological systems and document new, more subtle after-effects. For example, many species are shifting their distributions and phenologies at faster rates than were recorded just a few years ago; however, responses are not uniform across species. Shifts have been idiosyncratic and in some cases counterintuitive, promoting new community compositions and altering biotic interactions. Although genetic diversity enhances species\u27 potential to respond to variable conditions, climate change may outpace intrinsic adaptive capacities and increase the relative vulnerabilities of many organisms. Developing effective adaptation strategies for biodiversity conservation will not only require flexible decision-making and management approaches that account for uncertainties in climate projections and ecological responses but will also necessitate coordinated monitoring efforts

Active Nuclear Receptors Exhibit Highly Correlated AF-2 Domain Motions

Nuclear receptor ligand binding domains (LBDs) convert ligand binding events into changes in gene expression by recruiting transcriptional coregulators to a conserved activation function-2 (AF-2) surface. While most nuclear receptor LBDs form homo- or heterodimers, the human nuclear receptor pregnane X receptor (PXR) forms a unique and essential homodimer and is proposed to assemble into a functional heterotetramer with the retinoid X receptor (RXR). How the homodimer interface, which is located 30 Å from the AF-2, would affect function at this critical surface has remained unclear. By using 20- to 30-ns molecular dynamics simulations on PXR in various oligomerization states, we observed a remarkably high degree of correlated motion in the PXR–RXR heterotetramer, most notably in the four helices that create the AF-2 domain. The function of such correlation may be to create “active-capable” receptor complexes that are ready to bind to transcriptional coactivators. Indeed, we found in additional simulations that active-capable receptor complexes involving other orphan or steroid nuclear receptors also exhibit highly correlated AF-2 domain motions. We further propose a mechanism for the transmission of long-range motions through the nuclear receptor LBD to the AF-2 surface. Taken together, our findings indicate that long-range motions within the LBD scaffold are critical to nuclear receptor function by promoting a mobile AF-2 state ready to bind coactivators

Expression, localization and polymorphisms of the nuclear receptor PXR in Barrett's esophagus and esophageal adenocarcinoma

Background: The continuous exposure of esophageal epithelium to refluxate may induce ectopic expression of bile-responsive genes and contribute to the development of Barrett's esophagus (BE) and esophageal adenocarcinoma. In normal physiology of the gut and liver, the nuclear receptor Pregnane × Receptor (PXR) is an important factor in the detoxification of xenobiotics and bile acid homeostasis. This study aimed to investigate the expression and genetic variation of PXR in reflux esophagitis (RE), Barrett's esophagus (BE) and esophageal adenocarcinoma.Methods: PXR mRNA levels and protein expression were determined in biopsies from patients with adenocarcinoma, BE, or RE, and healthy controls. Esophageal cell lines were stimulated with lithocholic acid and rifampicin. PXR polymorphisms 25385C/T, 7635A/G, and 8055C/T were genotyped in 249 BE patients, 233 RE patients, and 201 controls matched for age and gender.Results: PXR mRNA levels were significantly higher in adenocarcinoma tissue and columnar Barrett's epithelium, compared to squamous epithelium of these BE patients (P < 0.001), and RE patients (P = 0.003). Immunohistochemical staining of PXR showed predominantly cytoplasmic expression in BE tissue, whereas nuclear expression was found in adenocarcinoma tissue. In cell lines, stimulation with lithocholic acid did not increase PXR mRNA levels, but did induce nuclear translocation of PXR protein. Genotyping of the PXR 7635A/G polymorphism revealed that the G allele was significantly more prevalent in BE than in RE or controls (P = 0.037).Conclusions: PXR expresses in BE and adenocarcinoma tissue, and showed nuclear localization in adenocarcinoma tissue. Upon stimulation with lithocholic acid, PXR translocates to the nuclei of OE19 adenocarcinoma cells. Together with the observed association of a PXR polymorphism and BE, this data implies that PXR may have a function in prediction and treatment of esophageal disease

A size-based approach to quantifying predation on longfin inshore squid Loligo pealeii in the northwest Atlantic

Cephalopods are primary prey to a wide range of predators in global marine ecosystems. Despite their apparent ecological importance, little information exists on size-based predation respective to this taxon. Using long-term food habits and data from population surveys and commercial landings, we quantified size-based patterns of predation respective to 11 species of finfish, elasmobranchs, and marine mammals over ontogenetic scales. General trends of sizeselective and seasonal foraging behavior are also presented for 25 species of predators from the northwest Atlantic Ocean. The functional role of squid was evaluated by contrasting patterns in sizebasedpredation between squid and fish prey types. Measurements of predator gape morphology and prey body depths ascertained if predators were physically limited when feeding on squid. Additionally, the amount of overlap between natural predators and the commercial fishing industry for squid size resources was estimated. Predation by finfish and elasmobranchs was generally focused on juvenile and sub-adult squid, while marine mammals primarily targeted adults. Consequently,marine mammals had the highest overlap with the commercial fishing indu&try for squid sizeresources. All predators exhibited size-selective feeding behavior, and trends persisted over seasonal time periods. Predators fed on a wider range of fish prey sizes than squid and did not appear to be gape limited when feeding on squid; however, large squid were not common in predator diets. Results suggest squid behavior and availability in the environment are paramount in shaping sizebased patterns of predation

Feeding tactics of a behaviorally plastic predator, summer flounder (Paralichthys dentatus)

In a series of laboratory experiments, the feeding behaviors of summer flounder (Paralichthys dentatus) were examined in response to squid and fish prey. Attack and capture tactics were evaluated for their influence on capture success, handling time, and prey-type selectivity. The ambush tactic was the primary behavior (50.6%) used to attack squid. Secondary attack types included active pursuit (42.7%) and stalking (6.7%). Regardless of the prey species targeted or the type of attack employed, summer flounder were equally efficient in capturing prey; capture success rates ranged from 50%–83%. The majority of prey were swallowed in a headfirst orientation (55.3% of squid), however swallow alignment did not significantly affect handling time. Approach times during ambush attacks were greater overall in comparison to active attacks, and relative prey size significantly affected capture times. Despite additional costs in handling time, summer flounder actively selected for mummichogs (Fundulus spp.) (attack rate (attacks per minute) = 0.11) over longfin squid (Loligo pealeii) (0.08) and Atlantic silversides (Menidia menidia) (0.02). Differential attack rates favoring mummichogs suggests a preference towards demersal prey. In the presence of relatively large, fast-moving, and pelagic prey, summer flounder used a greater diversity of attack tactics than have been observed previously under controlled conditions. The behavioral plasticity exhibited by summer flounder is likely mediated by prey behavior and local availability of prey resources in inshore and offshore environments