Carcharhinid sharks can make up a large fraction of the top predators inhabiting tropical marine ecosystems and have declined in many regions due to intense fishing pressure. There is some support ...for the hypothesis that carcharhinid species that complete their life-cycle within coral reef ecosystems, hereafter referred to as "reef sharks", are more abundant inside no-take marine reserves due to a reduction in fishing pressure (i.e., they benefit from marine reserves). Key predictions of this hypothesis are that (a) individual reef sharks exhibit high site-fidelity to these protected areas and (b) their relative abundance will generally be higher in these areas compared to fished reefs. To test this hypothesis for the first time in Caribbean coral reef ecosystems we combined acoustic monitoring and baited remote underwater video (BRUV) surveys to measure reef shark site-fidelity and relative abundance, respectively. We focused on the Caribbean reef shark (Carcharhinus perezi), the most common reef shark in the Western Atlantic, at Glover's Reef Marine Reserve (GRMR), Belize. Acoustically tagged sharks (N = 34) were detected throughout the year at this location and exhibited strong site-fidelity. Shark presence or absence on 200 BRUVs deployed at GRMR and three other sites (another reserve site and two fished reefs) showed that the factor "marine reserve" had a significant positive effect on reef shark presence. We rejected environmental factors or site-environment interactions as predominant drivers of this pattern. These results are consistent with the hypothesis that marine reserves can benefit reef shark populations and we suggest new hypotheses to determine the underlying mechanism(s) involved: reduced fishing mortality or enhanced prey availability.
Heterotrophic respiration (RH) is a major process releasing carbon to the atmosphere and is essential to understanding carbon dynamics in terrestrial ecosystems. Here we review what is known about ...this flux as related to forest disturbance using examples from North America. The global RH flux from soils has been estimated at 53–57 Pg C yr−1, but this does not include contributions from other sources (i.e., dead wood, heart‐rots). Disturbance‐related inputs likely account for 20–50% of all RH losses in forests, and disturbances lead to a reorganization of ecosystem carbon pools that influences how RH changes over succession. Multiple controls on RH related to climate, the material being decomposed, and the decomposers involved have been identified, but how each potentially interacts with disturbance remains an open question. An emerging paradigm of carbon dynamics suggests the possibility of multiple periods of carbon sinks and sources following disturbance; a large contributing factor is the possibility that postdisturbance RH does not always follow the monotonic decline assumed in the classic theory. Without a better understanding and modeling of RH and its controlling factors, it will be difficult to estimate, forecast, understand, and manage carbon balances of regions in which disturbance frequency and severity are changing. Meeting this challenge will require (1) improved field data on processes and stores, (2) an improved understanding of the physiological and environmental controls of RH, and (3) a more formal analysis of how model structure influences the RH responses that can be predicted.
Key Points
Sources of RH are diverse with very uneven levels of understanding
Disturbance is a major control of RH and carbon balances
Interactive effects of disturbance legacies and climate on RH need examination
Top predators can exert strong influences on community structure and function, both via direct, consumptive effects, as well as through non-consumptive, fear-based effects (i.e. predation risk). ...However, these effects are challenging to quantify, particularly for mobile predators in marine ecosystems. To advance this field of research, here we used baited remote underwater video stations (BRUVs) to assess how the behavior of mobile fish species off Cape Cod, Massachusetts, was affected by exposure to large sharks. We categorized sites into three levels of differential shark predation exposure (white sharks, Carcharodon carcharias) and quantified the relative abundance and arrival times (elapsed time before appearing on screen) for six mobile fish prey groups to the BRUV stations. Increased large shark exposure was associated with a decrease in overall prey abundance, but the overall response was prey group-specific. Foraging of smooth dogfish, a likely important prey item for large sharks in the system, was significantly reduced in areas frequented by white sharks. Specifically, the predicted probabilities of smooth dogfish bait contacts or bite attempts occurring were reduced by factors of 5.7 and 8.4, respectively, in areas of high exposure as compared to low exposure. These modifications were underscored by a decrease in smooth dogfish abundance in areas of high exposure as well. Our results suggest that populations of large, roving sharks may induce food-related costs in prey. We discuss the implications of this work within the context of the control of risk (COR) hypothesis, for the purposes of advancing our understanding of the ecological role and effects of large sharks on coastal marine ecosystems.
The great hammerhead (Sphyrna mokarran) is a highly mobile, large‐bodied shark primarily found in coastal‐pelagic and semi‐oceanic waters across a circumtropical range. It is a target or by‐catch ...species in multiple fisheries, and as a result, rapid population declines have occurred in many regions. These declines have contributed to the species being assessed as globally critically endangered on the IUCN Red List. Although conservation and management measures have yielded promising results in some regions, such as the United States, high levels of at‐vessel and post‐release mortality remain a major concern to the species population recovery. This examined the vertical space use and thermal range of pop‐off archival satellite–tagged S. mokarran in the western North Atlantic Ocean, expanding the understanding of the ecological niche of this species and providing insight into by‐catch mitigation strategies for fisheries managers. The results showed that S. mokarran predominantly used shallow depths (75% of records <30 m) and had a narrow temperature range (89% of records between 23 and 28°C). Individual differences in depth use were apparent, and a strong diel cycle was observed, with sharks occupying significantly deeper depths during the daytime. Furthermore, two individuals were confirmed pregnant with one migrating from the Bahamas to South Carolina, U.S.A., providing further evidence of regional connectivity and parturition off the U.S. East Coast. The findings suggest that S. mokarran may be vulnerable to incidental capture in the western North Atlantic commercial longline fisheries due to substantial vertical overlap between the species and the gear. The results can be incorporated into conservation and management efforts to develop and/or refine mitigation measures focused on reducing the by‐catch and associated mortality of this species, which can ultimately aide S. mokarran population recovery in areas with poor conservation status.
The genetic factors that modulate risk for developing lung cancer have not been fully defined. Here, we sought to determine the prevalence and clinical significance of germline pathogenic/likely ...pathogenic variants (PV) in patients with advanced lung cancer.
We studied clinical and tumor characteristics of germline PV in 5,118 patients who underwent prospective genomic profiling using paired tumor-normal tissue samples in 468 cancer genes.
Germline PV in high/moderate-penetrance genes were observed in 222 (4.3%) patients; of these, 193 patients had PV in DNA damage repair (DDR) pathway genes including BRCA2 (n = 54), CHEK2 (n = 30), and ATM (n = 26) that showed high rate of biallelic inactivation in tumors. BRCA2 heterozygotes with lung adenocarcinoma were more likely to be never smokers and had improved survival compared with noncarriers. Fourteen patients with germline PV in lung cancer predisposing genes (TP53, EGFR, BAP1, and MEN1) were diagnosed at younger age compared with noncarriers, and of tumor suppressors, 75% demonstrated biallelic inactivation in tumors. A significantly higher proportion of germline PV in high/moderate-penetrance genes were detected in high-risk patients who had either a family history of any cancer, multiple primary tumors, or early age at diagnosis compared with unselected patients (10.5% vs. 4.1%; P = 1.7e-04).
These data underscore the biological and clinical importance of germline mutations in highly penetrant DDR genes as a risk factor for lung cancer.
The family members of lung cancer patients harboring PV in cancer predisposing genes should be referred for genetic counseling and may benefit from proactive surveillance.
Fire and herbivory interact to alter ecosystems and carbon cycling. In savannas, herbivores can reduce fire activity by removing grass biomass, but the size of these effects and what regulates them ...remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density. We show that, broadly across African savannas, grazing herbivores substantially reduce both herbaceous biomass and fire activity. The size of these effects was strongly associated with grazing herbivore densities, and surprisingly, was mostly consistent across different environments. A one‐zebra increase in herbivore biomass density (~100 kg/km2 of metabolic biomass) resulted in a ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage point reduction in burned area. Our results indicate that fire models can be improved by incorporating grazing effects on grass biomass.
Grazing herbivores substantially influence terrestrial ecosystem processes, especially in African savannas where wild herbivores can occur at high densities and grass‐fuelled fires are frequent, but the size of these effects and what regulates them remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density. Our results indicate that (1) the magnitude of grazing effects on herbaceous biomass and fire activity is substantial across African savannas, (2) although there was some variation in herbivore effect on grass biomass across environmental gradients, this was minor compared with the effect of herbivore metabolic densities, and (3) grazing reduces fire activity, (4) most likely by consuming fuel loads.
Bulk stable isotope analysis was used to assess the trophic level and foraging habitats of Caribbean reef sharks (
Carcharhinus perezi
) compared to three large sympatric predatory teleosts (the ...Nassau grouper
Epinephelus striatus
, black grouper
Mycteroperca bonaci
, and great barracuda
Sphyraena barracuda
) in an isolated Caribbean coral reef ecosystem. Models and empirical studies have suggested that the depletion of large-bodied sharks in coral reef ecosystems triggers a trophic cascade that could affect the benthic community, favoring algae over coral. The hypothesized cascade is based on the premise that sharks prey on large piscivorous teleost fish that in turn prey on key herbivorous fish. Analysis of nitrogen-stable isotopes (δ
15
N) from white muscle tissue revealed neither adult or juvenile Caribbean reef sharks were significantly enriched in
15
N compared with sympatric predatory teleost species. Linear regression found no evidence of an ontogenetic increase in nitrogen with increasing body size for Caribbean reef sharks; however, there was a significant positive relationship between body size and carbon isotope (δ
13
C) values. These results suggest that Caribbean reef sharks in isolated systems do not act as the apex predator in coral reef ecosystems primarily feeding on large-bodied sympatric teleosts. Instead, Caribbean reef sharks form part of an upper trophic-level predator guild alongside large-bodied teleosts, which makes the predicted trophic cascade as a result of the removal of reef sharks unlikely. Moreover, the body size–δ
13
C relationship suggests Caribbean reef sharks exhibit ontogenetic and individual variation in where they feed. The ecological role of this species is, therefore, complex and contextual, similar to carcharhinid species in the Indo-Pacific, emphasizing the need to further elucidate the interactions between reef sharks and the overall coral reef ecosystem so as to best inform effective conservation and management of the species.
The indirect effect of predators on prey behavior, recruitment, and spatial relationships continues to attract considerable attention. However, top predators like sharks or large, mobile teleosts, ...which can have substantial top–down effects in ecosystems, are often difficult to study due to their large size and mobility. This has created a knowledge gap in understanding how they affect their prey through nonconsumptive effects. Here, we investigated how different functional groups of predators affected potential prey fish populations across various habitats within Biscayne Bay, FL. Using baited remote underwater videos (BRUVs), we quantified predator abundance and activity as a rough proxy for predation risk and analyzed key prey behaviors across coral reef, sea fan, seagrass, and sandy habitats. Both predator abundance and prey arrival times to the bait were strongly influenced by habitat type, with open homogenous habitats receiving faster arrival times by prey. Other prey behaviors, such as residency and risk‐associated behaviors, were potentially driven by predator interaction. Our data suggest that small predators across functional groups do not have large controlling effects on prey behavior or stress responses over short temporal scales; however, habitats where predators are more unpredictable in their occurrence (i.e., open areas) may trigger risk‐associated behaviors such as avoidance and vigilance. Our data shed new light on the importance of habitat and context for understanding how marine predators may influence prey behaviors in marine ecosystems.
Assessing behavioral risk effects of marine predators on mobile prey species across varying habitats in Biscayne Bay, FL. Providing new insights into the role marine predators play in influencing prey behavior in a variety of contexts.
To evaluate the effectiveness of the Genomics ADvISER (www.genomicsadviser.com) decision aid (DA) for selection of secondary findings (SF), compared with genetic counseling alone.
A randomized ...controlled trial (RCT) was conducted to evaluate whether the Genomics ADvISER is superior to genetic counseling when hypothetically selecting SF. Participants were randomized to use the DA followed by discussion with a genetic counselor, or to genetic counseling alone. Surveys were administered at baseline and post-intervention. Primary outcome was decisional conflict. Secondary outcomes were knowledge, preparation for, and satisfaction with decision-making, anxiety, and length of counseling session.
Participants (n = 133) were predominantly White/European (74%), female (90%), and ≥50 years old (60%). Decisional conflict (mean difference 0.05; P = 0.60), preparation for decision-making (0.17; P = 0.95), satisfaction with decision (–2.18; P = 0.06), anxiety (0.72; P = 0.56), and knowledge of sequencing limitations (0.14; P = 0.70) did not significantly differ between groups. However, intervention participants had significantly higher knowledge of SF (0.39; P < 0.001) and sequencing benefits (0.97; P = 0.01), and significantly shorter counseling time (24.40 minutes less; P < 0.001)
The Genomics ADvISER did not decrease decisional conflict but reduced counseling time and improved knowledge. This decision aid could serve as an educational tool, reducing in-clinic time and potentially health care costs.
We present photometry and spectroscopy of 11 and 35 potential cataclysmic variables, respectively, from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey, and vsnet alerts. The ...photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76 + or - 2 minutes, and possible eclipses in SDSS J2158+09 at an orbital period near 100 minutes. Time-resolved spectra reveal short orbital periods near 80 minutes for SDSS J0206+20, 85 minutes for SDSS J1502+33, and near 100 minutes for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15, and SDSS J2158+09. The prominent He II line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the absence of this line and a low velocity amplitude argue against this classification for RXS JO 150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects.
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