Tracking of marine predators to protect Southern Ocean ecosystems.

Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.

National trends in the endovascular and surgical treatment of idiopathic intracranial hypertension.

BACKGROUND: The pattern of surgical treatments for Idiopathic Intracranial Hypertension (IIH) in the United States is not well-studied, specifically the trend of utilizing endovascular venous stenting (EVS) as an emerging technique. METHODS: In this cross-sectional study, we aimed to explore the national trend of utilizing different procedures for the treatment of IIH including EVS, Optic Nerve Sheath Fenestration (ONSF), and CSF Shunting, with a focus on novel endovascular procedures. Moreover, we explored rates of 90-day readmission and length of hospital stay following different procedures, besides the effects of sociodemographic and clinical parameters on procedure choice. RESULTS: 36,437 IIH patients were identified from records between 2010 and 2018. Those in the EVS group were 29 years old on average, and 93.4 % were female. Large academic hospital setting was independently associated with higher EVS utilization, while other factors were not predictive of procedure choice. The proportion of EVS use in IIH hospitalizations increased significantly from 2010 to 2018 (P < 0.001), while there was a relative decline in the frequency of shunting procedures (P = 0.001), with ONSF utilization remaining stable (P = 0.39). The rate of 90-day readmission and length of hospital stay were considerably lower following EVS compared to other procedures (Ps < 0.001). CONCLUSION: This study presents novel population-level data on national trends in the frequency and outcome of EVS for IIH therapy. EVS was associated with shorter length of hospital stays and fewer readmission rates. In addition, a continuous increase in venous stenting compared to other procedures suggests an increasing role for endovascular therapies in IIH.

Prospective Observational Cohort Study of Tenecteplase Versus Alteplase in Routine Clinical Practice.

BACKGROUND: A 10-hospital regional network transitioned to tenecteplase as the standard of care stroke thrombolytic in September 2019 because of potential workflow advantages and reported noninferior clinical outcomes relative to alteplase in meta-analyses of randomized trials. We assessed whether tenecteplase use in routine clinical practice reduced thrombolytic workflow times with noninferior clinical outcomes. METHODS: We designed a prospective registry-based observational, sequential cohort comparison of tenecteplase- (n=234) to alteplase-treated (n=354) stroke patients. We hypothesized: (1) an increase in the proportion of patients meeting target times for target door-to-needle time and transfer door-in-door-out time, and (2) noninferior favorable (discharge to home with independent ambulation) and unfavorable (symptomatic intracranial hemorrhage, in-hospital mortality or discharge to hospice) in the tenecteplase group. Total hospital cost associated with each treatment was also compared. RESULTS: Target door-to-needle time within 45 minutes for all patients was superior for tenecteplase, 41% versus 29%; adjusted odds ratio, 1.85 (95% CI, 1.27-2.71); P=0.001; 58% versus 41% by Get With The Guidelines criteria. Target door-in-door-out time within 90 minutes was superior for tenecteplase 37% (15/43) versus 14% (9/65); adjusted odds ratio, 3.62 (95% CI, 1.30-10.74); P=0.02. Favorable outcome for tenecteplase fell within the 6.5% noninferiority margin; adjusted odds ratio, 1.26 (95% CI, 0.89-1.80). Unfavorable outcome was less for tenecteplase, 7.3% versus 11.9%, adjusted odds ratio, 0.77 (95% CI, 0.42-1.37) but did not fall within the prespecified 1% noninferior boundary. Net benefit (%favorable-%unfavorable) was greater for the tenecteplase sample: 37% versus 27%. P=0.02. Median cost per hospital encounter was less for tenecteplase cases ($13 382 versus $15 841; P<0.001). CONCLUSIONS: Switching to tenecteplase in routine clinical practice in a 10-hospital network was associated with shorter door-to-needle time and door-in-door-out times, noninferior favorable clinical outcomes at discharge, and reduced hospital costs. Evaluation in larger, multicenter cohorts is recommended to determine if these observations generalize.

Coastal regions of the northern Antarctic Peninsula are key for gentoo populations.

Southern Ocean ecosystems are rapidly changing due to climate variability. An apparent beneficiary of such change in the western Antarctic Peninsula (WAP) is the gentoo penguin Pygoscelis papua, which has increased its population size and expanded its range southward in the last 20 years. To better understand how this species has responded to large-scale changes, we tracked individuals during the non-breeding winter period from five colonies across the latitudinal range of breeding sites in the WAP, including from a recently established colony. Results highlight latitudinal gradients in movement; strong associations with shallow, coastal habitats along the entire Antarctic Peninsula; and movements that are independent of, yet constrained by, sea ice. It is clear that coastal habitats essential to gentoo penguins during the breeding season are similarly critical during winter. Larger movements of birds from northern colonies in the WAP further suggest that leap-frog migration may influence colonization events by facilitating nest-area prospecting and use of new haul-out sites. Our results support efforts to develop a marine protected area around the WAP. Winter habitats used by gentoo penguins outline high priority areas for improving the management of the spatio-temporally concentrated krill (Euphausia superba) fishery that operates in this region during winter.

Patient Characteristics and Outcomes Associated with Decline in Stroke Volumes During the Early COVID-19 Pandemic.

BACKGROUND AND PURPOSE: Delayed evaluation of stroke may contribute to COVID-19 pandemic-related morbidity and mortality. This study evaluated patient characteristics, process measures and outcomes associated with the decline in stroke presentation during the early pandemic. METHODS: Volumes of stroke presentations, intravenous thrombolytic administrations, and mechanical thrombectomies from 52 hospitals from January 1-June 30, 2020 were analyzed with piecewise linear regression and linear spline models. Univariate analysis compared pandemic (case) and pre-pandemic (control) groups defined in relation to the nadir of daily strokes during the study period. Significantly different patient characteristics were further evaluated with logistic regression, and significantly different process measures and outcomes were re-analyzed after propensity score matching. RESULTS: Analysis of 7,389 patients found daily stroke volumes decreased 0.91/day from March 12-26 (p < 0.0001), reaching a nadir 35.0% less than expected, and increased 0.15 strokes/day from March 27-June 23, 2020 (p < 0.0001). Intravenous thrombolytic administrations decreased 3.3/week from February 19-March 31 (p = 0.0023), reaching a nadir 33.4% less than expected, and increased 1.4 administrations/week from April 1-June 23 (p < 0.0001). Mechanical thrombectomy volumes decreased by 1.5/week from February 19-March 31, 2020 (p = 0.0039), reaching a nadir 11.3% less than expected. The pandemic group was more likely to ambulate independently at baseline (p = 0.02, OR = 1.60, 95% CI = 1.08-2.42), and less likely to present with mild stroke symptoms (NIH Stroke Scale ≤ 5; p = 0.04, OR = 1.01, 95% CI = 1.00-1.02). Process measures and outcomes of each group did not differ, including door-to-needle time, door-to-puncture time, and successful mechanical thrombectomy rate. CONCLUSION: Stroke presentations and acute interventions decreased during the early COVID-19 pandemic, at least in part due to patients with lower baseline functional status and milder symptoms not seeking medical care. Public health messaging and initiatives should target these populations.

Acute bottlenecks to the survival of juvenile Pygoscelis penguins occur immediately after fledging.

Estimating when and where survival bottlenecks occur in free-ranging marine predators is critical for effective demographic monitoring and spatial planning. This is particularly relevant to juvenile stages of long-lived species for which direct observations of death are typically not possible. We used satellite telemetry data from fledgling Adélie, chinstrap and gentoo penguins near the Antarctic Peninsula to estimate the spatio-temporal scale of a bottleneck after fledging. Fledglings were tracked up to 106 days over distances of up to 2140 km. Cumulative losses of tags increased to 73% within 16 days of deployment, followed by an order-of-magnitude reduction in loss rates thereafter. The timing and location of tag losses were consistent with at-sea observations of penguin carcasses and bioenergetics simulations of mass loss to thresholds associated with low recruitment probability. A bootstrapping procedure is used to assess tag loss owing to death versus other factors. Results suggest insensitivity in the timing of the bottleneck and quantify plausible ranges of mortality rates within the bottleneck. The weight of evidence indicates that a survival bottleneck for fledgling penguins is acute, attributable to predation and starvation, and may account for at least 33% of juvenile mortality.

Contributions of a modified electrodynamics to the molecular biochirality.

In this paper, we investigate the physical basis behind the molecular biochirality from the computation of a parity violation energy difference (PVED) in enantiomers of organic molecules (e.g., amino acids, which occur as levogyrous-type in nature), by considering the influence of fundamental interactions beyond the standard model of elementary particles and interactions. Particularly, we study the role of a 4-D Chern-Simons theory at the origin of this PVED, the Carroll-Field-Jackiw electrodynamics, which violates both Lorentz and parity symmetries. Then, we consider terrestrial and Jovian scenarios where the influence of a modified (effective) magnetic field generated by the planets on the molecules is taken into account in the calculation of PVED. Besides this quantity, we also calculate the relative quantity excess of an enantiomer over the other in a thermal bath. Finally, we compare the obtained results with those ones from other models based on fundamental interactions.

A technique for the salvage of megafistulas allowing immediate dialysis access.

OBJECTIVE: Almost two million individuals are undergoing renal replacement therapy worldwide, with hemodialysis being the common form. Many factors influence the primary patency of an arteriovenous fistula (AVF), including vessel size, fistula flow rates, cannulation practice, and thrombotic tendencies. Excess dilation of the AVF, resulting in the development of a megafistula, is a complication that can result in a need for AVF revision and subsequent failure. METHODS: The charts of patients who underwent autogenous AVF revision because of the development of a megafistula with aneurysmectomy and vein transposition by a single surgeon during a 7-year period from 2009 through 2016 were reviewed. A technique is described in which after aneurysmorrhaphy, the repaired venous component of the AVF is transposed through a new tunnel while the vein is rotated 90 degrees. This allows the AVF to be accessed immediately, making placement of a tunneled dialysis catheter unnecessary. RESULTS: There were 102 patients included in the study, with follow-up ranging from 7 to 95 months. In our cohort, 92 of the 102 revised AVFs (90.2%) maintained primary functional patency. Of the 102 patients who underwent this revision technique, there were 10 fistulas that subsequently failed after a mean of 29 months. There were only seven patients who experienced recurrent fistula dilation requiring repeated aneurysmectomy. CONCLUSIONS: We describe a technique for management of the development of a megafistula that uses only autogenous tissue and, perhaps most important, eliminates the need for temporary dialysis catheter placement.

Probabilistic measures of climate change vulnerability, adaptation action benefits, and related uncertainty from maximum temperature metric selection.

Predictions of the projected changes in species distributions and potential adaptation action benefits can help guide conservation actions. There is substantial uncertainty in projecting species distributions into an unknown future, however, which can undermine confidence in predictions or misdirect conservation actions if not properly considered. Recent studies have shown that the selection of alternative climate metrics describing very different climatic aspects (e.g., mean air temperature vs. mean precipitation) can be a substantial source of projection uncertainty. It is unclear, however, how much projection uncertainty might stem from selecting among highly correlated, ecologically similar climate metrics (e.g., maximum temperature in July, maximum 30-day temperature) describing the same climatic aspect (e.g., maximum temperatures) known to limit a species' distribution. It is also unclear how projection uncertainty might propagate into predictions of the potential benefits of adaptation actions that might lessen climate change effects. We provide probabilistic measures of climate change vulnerability, adaptation action benefits, and related uncertainty stemming from the selection of four maximum temperature metrics for brook trout (Salvelinus fontinalis), a cold-water salmonid of conservation concern in the eastern United States. Projected losses in suitable stream length varied by as much as 20% among alternative maximum temperature metrics for mid-century climate projections, which was similar to variation among three climate models. Similarly, the regional average predicted increase in brook trout occurrence probability under an adaptation action scenario of full riparian forest restoration varied by as much as .2 among metrics. Our use of Bayesian inference provides probabilistic measures of vulnerability and adaptation action benefits for individual stream reaches that properly address statistical uncertainty and can help guide conservation actions. Our study demonstrates that even relatively small differences in the definitions of climate metrics can result in very different projections and reveal high uncertainty in predicted climate change effects.

Rethinking "normal": The role of stochasticity in the phenology of a synchronously breeding seabird.

Phenological changes have been observed in a variety of systems over the past century. There is concern that, as a consequence, ecological interactions are becoming increasingly mismatched in time, with negative consequences for ecological function. Significant spatial heterogeneity (inter-site) and temporal variability (inter-annual) can make it difficult to separate intrinsic, extrinsic and stochastic drivers of phenological variability. The goal of this study was to understand the timing and variability in breeding phenology of Adélie penguins under fixed environmental conditions and to use those data to identify a "null model" appropriate for disentangling the sources of variation in wild populations. Data on clutch initiation were collected from both wild and captive populations of Adélie penguins. Clutch initiation in the captive population was modelled as a function of year, individual and age to better understand phenological patterns observed in the wild population. Captive populations displayed as much inter-annual variability in breeding phenology as wild populations, suggesting that variability in breeding phenology is the norm and thus may be an unreliable indicator of environmental forcing. The distribution of clutch initiation dates was found to be moderately asymmetric (right skewed) both in the wild and in captivity, consistent with the pattern expected under social facilitation. The role of stochasticity in phenological processes has heretofore been largely ignored. However, these results suggest that inter-annual variability in breeding phenology can arise independent of any environmental or demographic drivers and that synchronous breeding can enhance inherent stochasticity. This complicates efforts to relate phenological variation to environmental variability in the wild. Accordingly, we must be careful to consider random forcing in phenological processes, lest we fit models to data dominated by random noise. This is particularly true for colonial species where breeding synchrony may outweigh each individual's effort to time breeding with optimal environmental conditions. Our study highlights the importance of identifying appropriate null models for studying phenology.

Circumpolar analysis of the Adélie Penguin reveals the importance of environmental variability in phenological mismatch.

Evidence of climate-change-driven shifts in plant and animal phenology have raised concerns that certain trophic interactions may be increasingly mismatched in time, resulting in declines in reproductive success. Given the constraints imposed by extreme seasonality at high latitudes and the rapid shifts in phenology seen in the Arctic, we would also expect Antarctic species to be highly vulnerable to climate-change-driven phenological mismatches with their environment. However, few studies have assessed the impacts of phenological change in Antarctica. Using the largest database of phytoplankton phenology, sea-ice phenology, and Adélie Penguin breeding phenology and breeding success assembled to date, we find that, while a temporal match between Penguin breeding phenology and optimal environmental conditions sets an upper limit on breeding success, only a weak relationship to the mean exists. Despite previous work suggesting that divergent trends in Adélie Penguin breeding phenology are apparent across the Antarctic continent, we find no such trends. Furthermore, we find no trend in the magnitude of phenological mismatch, suggesting that mismatch is driven by interannual variability in environmental conditions rather than climate-change-driven trends, as observed in other systems. We propose several criteria necessary for a species to experience a strong climate-change-driven phenological mismatch, of which several may be violated by this system.

Stable isotope analyses of feather amino acids identify penguin migration strategies at ocean basin scales.

Identifying the at-sea distribution of wide-ranging marine predators is critical to understanding their ecology. Advances in electronic tracking devices and intrinsic biogeochemical markers have greatly improved our ability to track animal movements on ocean-wide scales. Here, we show that, in combination with direct tracking, stable carbon isotope analysis of essential amino acids in tail feathers provides the ability to track the movement patterns of two, wide-ranging penguin species over ocean basin scales. In addition, we use this isotopic approach across multiple breeding colonies in the Scotia Arc to evaluate migration trends at a regional scale that would be logistically challenging using direct tracking alone.

Short (6-mm) dental implants versus sinus floor elevation and placement of longer (≥10-mm) dental implants: a randomized controlled trial with a 3-year follow-up.

OBJECTIVES: To investigate whether short (6-mm) dental implants could be an alternative to sinus floor elevation (SFE) and placement of longer (≥10-mm) implants in the posterior maxilla. MATERIALS AND METHODS: Over a 3-year period, all patients presenting with partial edentulism in the posterior maxilla were considered for inclusion in this randomized controlled trial. Patients were randomly chosen either to receive short (6-mm) implants (test group [TG]) or to undergo SFE with simultaneous placement of standard-length (≥10-mm) implants (control group [CG]). SFE was performed using the lateral technique. In both groups, tapered implants (AnyRidge, MegaGen, Gyeongbuk, South Korea) were placed. All implants were loaded after 4 months of healing. At each annual follow-up session, clinical and radiographic parameters were assessed. Primary outcomes were implant survival, stability (measured with the implant stability quotient [ISQ]), marginal bone loss (MBL), and complications; secondary outcomes were patient satisfaction and treatment time and cost. RESULTS: Thirty-three patients were assigned to the TG and 20 to the CG. Forty-five implants were inserted in each group. At 3 years, implant survival rates were 100% and 95.0% for the TG and CG, respectively; this difference was not statistically significant (P = 0.38). The mean ISQ values of the TG and CG did not differ at placement (68.2 vs. 67.8, P = 0.1), at delivery of the final restoration (69.5 vs. 69.4, P = 0.9), and after 1 year (71.0 vs. 71.5, P = 0.1); at 3 years, the CG had a significantly higher mean ISQ than the TG (72.4 vs. 71.6, P = 0.004). Mean MBL was significantly higher in the CG than in the TG, both at 1 year (0.14 mm vs. 0.21 mm, P = 0.006) and at 3 years (0.20 mm vs. 0.27 mm, P = 0.01). A few complications were reported. Surgical time and cost were significantly higher in the CG than in the TG (P < 0.0001). Patient satisfaction was high in both groups. CONCLUSIONS: In this randomized controlled trial, results for short (6-mm) implants were similar to those for longer (≥10-mm) implants in augmented bone. Short implants might be preferable to SFE, because the treatment is faster and less expensive. Long-term randomized controlled trials are required to confirm these results.

Carbonate Buildups in the Pernambuco Basin, NE Brazil.

The Pernambuco Basin represents one of the most prominent regions for deep water oil and gas exploration off the Brazilian coast. This study aims to identify and describe the occurrence of carbonate buildups in the offshore regions of the basin. The study was based on an analysis of a set of 143 2D time-migrated seismic sections that cover the offshore region of the Pernambuco Basin. An interpretation of the seismic dataset was used to define the main seismic sequences related to the main regional pulses of deposition and to identify three main groups of carbonate buildups: 1) shelf margin reefs, 2) patch reefs, and 3) isolated carbonate buildups. The carbonate buildups formed in two main intervals during post-rift sequences of the Santonian-Maastrichtian and Paleocene-Middle Miocene, which extend the known periods of carbonate deposit formation in the basin. The formation of carbonate buildups was controlled by the tectonic evolution of the Pernambuco Plateau, which created a series of paleotopographic highs that enabled the establishment of oceanographically and climatically favorable conditions for carbonate formation and deposition. These findings are important for understanding the evolution of the basin and for future evaluations of its petroleum potential.

The effect of the toxic dinoflagellate Alexandrium fundyense on the fitness of the calanoid copepod Calanus finmarchicus.

Inshore and offshore waters of the Gulf of Maine (USA) have spring/summer harmful algal blooms (HABs) of the toxic dinoflagellate Alexandrium fundyense, which is responsible for paralytic shellfish poisoning (PSP) in humans. The calanoid copepod Calanus finmarchicus co-occurs with A. fundyense during the seasonal blooms. At that time, C. finmarchicus population abundances are high, dominated by immature copepods preparing for diapause, and by actively-reproducing adults. High survival has been reported for copepods exposed to toxic A. fundyense, but little is known about possible sublethal effects. In this study, C. finmarchicus adult females were fed either a control diet of non-toxic Rhodomonas spp. or one of two diets containing either low dose (LD) or high dose (HD) levels (50 and 200 cells mL-1, respectively) of toxic A. fundyense for a total of 7 days in two independent experiments. As expected, ingestion of the dinoflagellate had no effect on copepod survival and grazing activity. However, significant reductions of egg production and egg viability were observed in C. finmarchicus females fed on either experimental diet. After the 7-day experiment, total nauplius production by females on the LD and HD diets was reduced by 35% to 75% compared to the control females. These results suggest that blooms of A. fundyense in the Gulf of Maine may be an environmental challenge for C. finmarchicus populations, with a potential negative effect on copepod recruitment.

Zooplankton Community Grazing Impact on a Toxic Bloom of Alexandrium fundyense in the Nauset Marsh System, Cape Cod, Massachusetts, USA.

Embayments and salt ponds along the coast of Massachusetts can host localized blooms of the toxic dinoflagellate Alexandrium fundyense. One such system, exhibiting a long history of toxicity and annual closures of shellfish beds, is the Nauset Marsh System (NMS) on Cape Cod. In order measure net growth rates of natural A. fundyense populations in the NMS during spring 2012, incubation experiments were conducted on seawater samples from two salt ponds within the NMS (Salt Pond and Mill Pond). Seawater samples containing natural populations of grazers and A. fundyense were incubated at ambient temperatures. Concentrations of A. fundyense after incubations were compared to initial abundances to determine net increases from population growth, or decreases presumed to be primarily due to grazing losses. Abundances of both microzooplankton (ciliates, rotifers, copepod nauplii and heterotrophic dinoflagellates) and mesozooplankton (copepodites and adult copepods, marine cladocerans, and meroplankton) grazers were also determined. This study documented net growth rates that were highly variable throughout the bloom, calculated from weekly bloom cell counts from the start of sampling to bloom peak in both ponds (Mill Pond range = 0.12 - 0.46 d-1; Salt Pond range = -0.02 - 0.44 d-1). Microzooplankton grazers that were observed with ingested A. fundyense cells included polychaete larvae, rotifers, tintinnids, and heterotrophic dinoflagellates of the genera Polykrikos and Gymnodinium. Significant A. fundyense net growth was observed in two incubation experiments, and only a single experiment exhibited significant population losses. For the majority of experiments, due to high variability in data, net changes in A. fundyense abundance were not significant after the 24-hr incubations. However, experimental net growth rates through bloom peak were not statistically distinguishable from estimated long-term average net growth rates of natural populations in each pond (Mill Pond = 0.27 d-1 and Salt Pond = 0.20 d-1), which led to peak bloom concentrations on the order of 106 cells l-1 in both ponds. Experimental net growth rates from the incubations underestimated the observed natural net growth rates at several time intervals prior to bloom peak, which may indicate that natural populations experienced additional sources of vegetative cells or periods of reduced losses that the 24-hr incubation experiments did not capture, or that the experimental procedure introduced containment artifacts.

PSP toxin levels and plankton community composition and abundance in size-fractionated vertical profiles during spring/summer blooms of the toxic dinoflagellate Alexandrium fundyense in the Gulf of Maine and on Georges Bank, 2007, 2008, and 2010: 2. Plankton community composition and abundance.

As part of the Gulf of Maine Toxicity (GOMTOX) project, we determined Alexandrium fundyense abundance, paralytic shellfish poisoning (PSP) toxin levels in various plankton size fractions, and the community composition of potential grazers of A. fundyense in plankton size fractions during blooms of this toxic dinoflagellate in the coastal Gulf of Maine and on Georges Bank in spring and summer of 2007, 2008, and 2010. PSP toxins and A. fundyense cells were found throughout the sampled water column (down to 50 m) in the 20-64 µm size fractions. While PSP toxins were widespread throughout all size classes of the zooplankton grazing community, the majority of the toxin was measured in the 20-64 µm size fraction. A. fundyense cellular toxin content estimated from field samples was significantly higher in the coastal Gulf of Maine than on Georges Bank. Most samples containing PSP toxins in the present study had diverse assemblages of grazers. However, some samples clearly suggested PSP toxin accumulation in several different grazer taxa including tintinnids, heterotrophic dinoflagellates of the genus Protoperidinium, barnacle nauplii, the harpacticoid copepod Microsetella norvegica, the calanoid copepods Calanus finmarchicus and Pseudocalanus spp., the marine cladoceran Evadne nordmanni, and hydroids of the genus Clytia. Thus, a diverse assemblage of zooplankton grazers accumulated PSP toxins through food-web interactions. This raises the question of whether PSP toxins pose a potential human health risk not only from nearshore bivalve shellfish, but also potentially from fish and other upper-level consumers in zooplankton-based pelagic food webs.

PSP toxin levels and plankton community composition and abundance in size-fractionated vertical profiles during spring/summer blooms of the toxic dinoflagellate Alexandrium fundyense in the Gulf of Maine and on Georges Bank, 2007, 2008, and 2010: 1. Toxin levels.

As part of the NOAA ECOHAB funded Gulf of Maine Toxicity (GOMTOX) project, we determined Alexandrium fundyense abundance, paralytic shellfish poisoning (PSP) toxin composition, and concentration in quantitatively-sampled size-fractionated (20-64, 64-100, 100-200, 200-500, and > 500 µm) particulate water samples, and the community composition of potential grazers of A. fundyense in these size fractions, at multiple depths (typically 1, 10, 20 m, and near-bottom) during 10 large-scale sampling cruises during the A. fundyense bloom season (May-August) in the coastal Gulf of Maine and on Georges Bank in 2007, 2008, and 2010. Our findings were as follows: (1) when all sampling stations and all depths were summed by year, the majority (94% ± 4%) of total PSP toxicity was contained in the 20-64 µm size fraction; (2) when further analyzed by depth, the 20-64 µm size fraction was the primary source of toxin for 97% of the stations and depths samples over three years; (3) overall PSP toxin profiles were fairly consistent during the three seasons of sampling with gonyautoxins (1, 2, 3, and 4) dominating (90.7% ± 5.5%), followed by the carbamate toxins saxitoxin (STX) and neosaxitoxin (NEO) (7.7% ± 4.5%), followed by n-sulfocarbamoyl toxins (C1 and 2, GTX5) (1.3% ± 0.6%), followed by all decarbamoyl toxins (dcSTX, dcNEO, dcGTX2&3) (< 1%), although differences were noted between PSP toxin compositions for nearshore coastal Gulf of Maine sampling stations compared to offshore Georges Bank sampling stations for 2 out of 3 years; (4) surface cell counts of A. fundyense were a fairly reliable predictor of the presence of toxins throughout the water column; and (5) nearshore surface cell counts of A. fundyense in the coastal Gulf of Maine were not a reliable predictor of A. fundyense populations offshore on Georges Bank for 2 out of the 3 years sampled.

Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica.

The West Antarctic Peninsula (WAP) and adjacent Scotia Sea support abundant wildlife populations, many of which were nearly extirpated by humans. This region is also among the fastest-warming areas on the planet, with 5-6 °C increases in mean winter air temperatures and associated decreases in winter sea-ice cover. These biological and physical perturbations have affected the ecosystem profoundly. One hypothesis guiding ecological interpretations of changes in top predator populations in this region, the "sea-ice hypothesis," proposes that reductions in winter sea ice have led directly to declines in "ice-loving" species by decreasing their winter habitat, while populations of "ice-avoiding" species have increased. However, 30 y of field studies and recent surveys of penguins throughout the WAP and Scotia Sea demonstrate this mechanism is not controlling penguin populations; populations of both ice-loving Adélie and ice-avoiding chinstrap penguins have declined significantly. We argue in favor of an alternative, more robust hypothesis that attributes both increases and decreases in penguin populations to changes in the abundance of their main prey, Antarctic krill. Unlike many other predators in this region, Adélie and chinstrap penguins were never directly harvested by man; thus, their population trajectories track the impacts of biological and environmental changes in this ecosystem. Linking trends in penguin abundance with trends in krill biomass explains why populations of Adélie and chinstrap penguins increased after competitors (fur seals, baleen whales, and some fishes) were nearly extirpated in the 19th to mid-20th centuries and currently are decreasing in response to climate change.