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Plastic waste has been documented in nearly all types of marine environments and has been found in species spanning all levels of marine food webs. Within these marine environments, deep pelagic waters encompass the largest ecosystems on Earth. We lack a comprehensive understanding of the concentrations, cycling, and fate of plastic waste in sub-surface waters, constraining our ability to implement effective, large-scale policy and conservation strategies. We used remotely operated vehicles and engineered purpose-built samplers to collect and examine the distribution of microplastics in the Monterey Bay pelagic ecosystem at water column depths ranging from 5 to 1000 m. Laser Raman spectroscopy was used to identify microplastic particles collected from throughout the deep pelagic water column, with the highest concentrations present at depths between 200 and 600 m. Examination of two abundant particle feeders in this ecosystem, pelagic red crabs ( Pleuroncodes planipes ) and giant larvaceans ( Bathochordaeus stygius ), showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs. Our findings suggest that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within the water column and animal communities of the deep sea.

Understanding the distribution of life's variety has driven naturalists and scientists for centuries, yet this has been constrained both by the available data and the models needed for their analysis. Here we compiled data for over 67,000 marine and terrestrial species and used artificial neural networks to model species richness with the state and variability of climate, productivity, and multiple other environmental variables. We find terrestrial diversity is better predicted by the available environmental drivers than is marine diversity, and that marine diversity can be predicted with a smaller set of variables. Ecological mechanisms such as geographic isolation and structural complexity appear to explain model residuals and also identify regions and processes that deserve further attention at the global scale. Improving estimates of the relationships between the patterns of global biodiversity, and the environmental mechanisms that support them, should help in efforts to mitigate the impacts of climate change and provide guidance for adapting to life in the Anthropocene.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Intertidal and subtidal zones consist of heterogeneous habitats and dynamic environmental conditions, providing diverse options for fish to take advantage of marine resources. We explored how various environmental factors affected habitat use of an ecologically and economically important tropical marine fish, bonefish (Albula vulpes), on a fringing reef flat in Culebra, Puerto Rico, using a fine-scale acoustic telemetry positioning system. Machine learning algorithms and Bayesian inference via integrated nested Laplace approximation indicated diel period was the most important predictor of bonefish habitat use; bonefish occupied seagrass and mixed bottom (seagrass, macroalgae, sand) habitats most often at night, a deep-water soft sediment lagoon during the day, and infrequently used a shallow coral rubble reef crest. Zero-truncated (presence only) positioning frequency revealed more constrained utilization distributions during daytime and periods of higher water temperatures. Bonefish occupancy was highest in seagrass and mixed bottom habitats at lower water temperatures, and declined rapidly throughout the flat above 30 °C, which is consistent with temperature-mediated physiological constraints on performance (i.e. collapse of aerobic scope). Other factors including lunar phase, tidal state, and tide height had limited influence on bonefish habitat use. Building on a body of research, we propose several drivers of bonefish habitat use patterns amongst the diverse regions and habitats occupied, including predation risk, angling pressure, tidal variations, and temperature-related physiological performance. Our results emphasise the importance of conserving important seagrass foraging habitat through management and restoration.

Despite many positive benefits of ecotourism, increased human encounters with wildlife may have detrimental effects on wild animals. As charismatic megafauna, nesting and foraging sea turtles are increasingly the focus of ecotourism activities. The purpose of our study was to quantify the behavioral responses of immature green turtles (Chelonia mydas) to disturbance by snorkelers, and to investigate whether turtles have individual-level responses to snorkeler disturbance. Using a standardized disturbance stimulus in the field, we recorded turtle behaviors pre-and post-disturbance by snorkelers. Ninety percent of turtles disturbed by snorkeler (n = 192) initiated their flights at distances of ≤3 m. Using principal component analysis, we identified two distinct turtle personality types, ‘bold’and ‘timid’, based upon 145 encounters of 19 individually identified turtles and five disturbance response variables. There was significant intra-individual repeatability in behavioral responses to disturbance, but bolder turtles had more behavioral plasticity and less consistent responses than more timid individuals. Bolder individuals with reduced evasion responses might be at a higher risk of shark predation, while more timid turtles might have greater energetic consequences due to non-lethal predator effects and repeated snorkeler disturbance. Over the longer term, a turtle population with a mix of bold and timid individuals may promote more resilient populations. We recommend that snorkelers maintain > 3 m distance from immature green turtles when snorkeling, and that ecotourism activities be temporally and spatially stratified. Further, turtle watching guidelines need to be communicated to both tour operators and independent snorkelers to reduce the disturbance of turtles.

Bonefish (Albula spp.) have ecological, economic, and cultural importance throughout their tropical and subtropical range. These fish reside primarily in shallow, nearshore habitats, and their movement patterns are largely dominated by tidal flows, thermal regime, and seasonal spawning migrations. Previous studies of their spatial ecology show that bonefish exhibit moderate site fidelity to specific tidal creeks and flats; however, to date, limited research has looked at movement patterns of bonefish that reside in small fringing reef flats, such as those found associated with some islands in the Caribbean. This study used fixed station acoustic telemetry to quantify the movement patterns of bonefish inhabiting small fringing reef flats in the nearshore waters of Culebra, Puerto Rico, for nearly 3 years. Bonefish inhabiting these flats exhibited high site fidelity and small home ranges, with limited movements to flats that were no further than 3 km away. Network analyses revealed distinct groups of bonefish that were associated with the specific reef flats where they were tagged. This high site fidelity has considerable implications for the risk of disturbance to bonefish inhabiting reef flats. These small, isolated groups of fish are likely vulnerable to localized impacts such as habitat degradation or harvest and highly dependent on these specific locations.

Reliable age estimation is an essential tool to assess the status of wildlife populations and inform successful management. Aging methods, however, are often limited by too few data, skewed demographic representation, and by single or uncertain morphometric relationships. In this study, we synthesize age estimates in southern sea otters Enhydra lutris nereis from 761 individuals across 34 years of study, using multiple noninvasive techniques and capturing all life stages from 0 to 17 years of age. From wild, stranded, and captive individuals, we describe tooth eruptions, tooth wear, body length, nose scarring, and pelage coloration across ontogeny and fit sex‐based growth functions to the data. Dental eruption schedules provided reliable and identifiable metrics spanning 0.3–9 months. Tooth wear was the most reliable predictor of age of individuals aged 1–15 years, which when combined with total length, explained >93% of observed age. Beyond age estimation, dental attrition also indicated the maximum lifespan of adult teeth is 13‒17 years, corresponding with previous estimates of life expectancy. Von Bertalanffy growth function model simulations of length at age gave consistent estimates of asymptotic lengths (male Loo = 126.0‒126.8 cm, female Loo = 115.3‒115.7 cm), biologically realistic gestation periods (t0 = 115 days, SD = 10.2), and somatic growth (male k = 1.8, SD = 0.1; female k = 2.1, SD = 0.1). Though exploratory, we describe how field radiographic imaging of epiphyseal plate development or fusions may improve aging of immature sea otters. Together, our results highlight the value of integrating information from multiple and diverse datasets to help resolve conservation problems. By synthesizing more than two decades of southern sea otter physical examination data from strandings, captive‐rearing for release, and field studies, we provide strong support for adopting minimally invasive aging techniques based on metrics obtainable during brief field capture. These techniques provide the means to gather age‐specific information from a living, wild population to inform management decisions focused on restoring sea otters and their ecosystems throughout California. Our results also highlight the value of integrating information from multiple and diverse datasets to help resolve conservation problems.

We analyze recently-collected feather tissues from two species of seabirds, the sooty tern (Onychoprion fuscatus) and brown noddy (Anous stolidus), in three ocean regions (North Atlantic, North Pacific, South Pacific) with different human impacts. The species are similar morphologically and are similar in the trophic levels from which they feed within each location. In contrast, we detect reliable differences in trophic position amongst the regions. Trophic position appears to decline as the intensity of commercial fishing increases, and is at its lowest in the Caribbean. The spatial gradient in trophic position we document in these regions exceeds those detected over specimens from the last 130 years in the Hawaiian Islands. Modeling suggests that climate velocity and human impacts on fish populations strongly align with these differences.

Wildlife contaminant loads are often used to indicate ecosystem health, but their interpretation is complicated by the dynamics affecting the trophic transfer of toxins. Yet, coupled analyses of trophic position and contaminants may provide insights that help resolve the underlying signal of contaminants in ecosystems. Here, we analyze heavy metal concentrations and trophic positions for pelagic seabirds across time and space. We derive metal-specific trophic transfer coefficients from the literature and use them to interpret the changes in raw heavy metal concentrations in two settings: (i) for eight seabird species across a 125-year timeline in Hawaii, and (ii) for contemporary specimens of two tern species across three ocean basins. While previous studies report how trophic position varies in these two settings, here we investigate how trophic downgrading may affect the observed raw changes in contaminants. Using this approach, we find the highly-toxic metal elements (Hg, As, Pb) decline after 1980. However, several other metals (Cu, Mn, Mo, Cd, Fe) increase from 1990-2015. Though simultaneous biomagnification and trophic downgrading may obscure contaminant analyses across space and time, the trophic declines we observed (≤0.5 trophic level) are likely not sufficient to influence such comparisons. In addition, as extrapolating contaminant concentrations across broad ranges of trophic levels may be prone to large uncertainties, careful selection of the focal species for analysis is required. While high trophic level species, such as long-lived, fish-eating seabirds, are ideal for monitoring environmental contaminants across large spatial or time scales, lower trophic level species, like primary producers and consumers, may be more suitable for quantifying the concentrations of bio-available contaminants entering the marine ecosystem and the base of the marine food webs. Monitoring low and high trophic levels simultaneously may provide an integrated perspective that is needed to quantify the contaminants entering and bio-magnifying through marine ecosystems.