Biotic Habitat Research Articles

Variación intraespecífica de rasgos funcionales de Cedrela odorata L. en la Península de Nicoya, Costa Rica

El cambio climático modificará el régimen hidrológico global a causa de alteraciones en la magnitud de la precipitación y temperatura, y su interacción con las condiciones físicas y de vegetación de cada lugar; esto representa un gran riesgo para la conservación de las especies, ya que implica variaciones en las condiciones que les son cruciales para su desarrollo. En respuesta a los factores abióticos y bióticos del hábitat, las plantas muestran gran variabilidad intraespecífica de rasgos, esta habilidad les permite sobrevivir, crecer y reproducirse en diversos escenarios. Estudiar la variabilidad intraespecífica de caracteres morfológicos conlleva a entender el potencial de respuesta de las especies a factores de alteración, como el cambio climático. El objetivo del presente estudio fue evaluar la variabilidad intraespecífica del área foliar (mm2), el área foliar específica (mm-2 mg), contenido de materia seca foliar (mg-1 g), densidad de madera (g cm-3) y grosor de corteza (cm) de 90 individuos de Cedrela odorata en tres bosques naturales con distintos regímenes de precipitación anual. A partir de la hipótesis de que C. odorata podría modular la magnitud de expresión de los caracteres morfológicos antes mencionados, de acuerdo con las diferentes condiciones de precipitación. Los resultados demostraron que los valores de los atributos funcionales variaron significativamente entre las poblaciones estudiadas; además, se evidenció que el taxón expresó sus rasgos en un eje de especialización adquisitivo-conservativo en el uso de los recursos. La variabilidad intraespecífica de rasgos en C. odorata podría ser un mecanismo de resiliencia ante el cambio climático.

Managing organic matter content for restoring health and ecosystem services of soils of India

Soil health refers to its capacity to perform ecosystem services (ESs) as a living entity comprising of diverse flora and fauna. Soil organic matter (SOM) content, being an energy source and habitat for biota, is an important determinant of soil health. Through its impact on soil physical, chemical and biological properties, SOM content and its dynamics also determine numerous ecosystem services essential to human wellbeing and nature conservancy. However, SOM content in agricultural soils in India is often below the critical limit of -2% in the root zone because of widespread use of extractive farming practices, low input of organic fertilizers, and prevalence of soil degradation by erosion, salinization and other processes. Thus, agronomic productivity, water quality, and renewability, soil biodiversity and other ESs have been jeopardized, and several disservices (i.e., eutrophication of water, pollution of air, accelerated erosion, emission of greenhouse gases) are caused by poor soil health. Thus, there is an urgent need to restore SOM content, as well as enhance and sustain soil health through adoption of recommended management practices (RMPs). Afforestation of degraded soils, conversion to a restorative land use, and adoption of site-specific RMPs are critical to enhancing soil health. Some RMPs include conservation agriculture (CA), agroforestry, balanced input of fertilizers based on strategies of carbon-centric integrated nutrient management, nutritionsensitive agriculture, and use of cover cropping and complex systems. Incentivization through payments for ESs (PESs) by policy intervention is important for promoting adoption of RMPs. Soil scientists and agronomists must facilitate translation of science into action by communication with policy makers, land managers, and the general public. Soil science and environmental education must be included in the curricula at all levels (from primary and secondary schools to undergraduate and graduate courses). Religious organizations may also be involved in promoting stewardship of soil and other natural resources, and in advancing the concept of ‘Rights-of-Soil.’ Transformation of the fertilizer sector, with an emphasis on efficiency rather than rate of input, necessitates focus on restoration of soil health through increase in soil organic carbon content in the root zone by adoption of RMPs such as CA, agroforestry, and CNPK rather than NPK.

Occupancy Patterns in a Reintroduced Fisher Population during Reestablishment

ABSTRACTMonitoring population performance in the years following species reintroductions is key to assessing population restoration success and evaluating assumptions made in planning species restoration programs. From 2008–2010 we translocated 90 fishers (Pekania pennanti) from British Columbia, Canada, to Washington's Olympic Peninsula, USA, providing the opportunity to evaluate modeling assumptions used to identify the most suitable reintroduction areas in Washington and enhance understanding of fisher habitat associations in the late‐successional forest ecosystems in the coastal Pacific Northwest. From 2013–2016, we deployed 788 motion‐sensing cameras and hair (DNA)‐snaring devices distributed among 263 24‐km2 primary sampling units across the Olympic Peninsula. Our objectives were to determine whether occupancy patterns of the reestablishing population supported assumptions of the initial habitat assessment models, whether the population had expanded or shifted in distribution since the initial reintroductions, compare physical habitat attributes among land‐management designations, and determine whether the founding fishers had successfully reproduced. We predicted that site occupancy by fishers would be associated with landscapes characterized by high proportional coverage of dense forest canopies and medium‐sized and large trees, a diversity of stand structural classes, and area near the administrative boundary separating wilderness from more intensively managed forest lands. We detected fishers across designated wilderness, federal lands outside of wilderness, and other land designations in proportion to land availability on the Peninsula. We found negligible support for predictions that occupancy by fishers was associated with percent forest cover, tree‐size class, or structural class diversity. Rather, occupancy was strongly associated with lands near the wilderness boundary on both sides. We speculate that the boundary between wilderness and more intensively managed forest lands provided fishers with the most suitable prey in proximity to contiguous expanses of low‐ to mid‐elevation late‐successional forests that provided optimal resting, denning, and security values. Occupancy patterns shifted toward the west and south along a precipitation gradient during the study, indicating that population distribution had not yet stabilized 5–8 years following translocation. Genetic results indicated that ≥2 generations of fishers have been produced on the Peninsula. Annual occupancy rates across the Peninsula (0.08–0.24) were lower than in other previously studied and established fisher populations, indicating that not all habitat was fully occupied or that initial estimates of the extent of habitat was overestimated. The strong selection fishers exhibited for wilderness edge and weak selection against extensive forested wilderness areas suggested that habitat managers should strive for maintaining a suitable interspersion of required forest structures and biotic habitat components, such as prey resource availability. © 2019 The Wildlife Society.

Andean Tectonics and Mantle Dynamics as a Pervasive Influence on Amazonian Ecosystem

The Amazonian landscape evolution is the result of the combined effect of Andean tectonism, climate and the Earth’s interior dynamics. To reconstruct the landscape evolution and its influence on paleoenvironmental variations within Amazonia since the Oligocene, we conducted numerical experiments that incorporate different surface and geodynamic processes, reproducing many paleogeographic features as inferred from the sedimentary record. We show that the evolution of the drainage pattern gradually reduced the area of sedimentation derived from the Guiana and Brazilian shields while expanded the Andean derived deposits during the Miocene, affecting the nutrient availability. First order biotic habitats were inferred from these paleogeographical reconstructions, showing an eastward expansion of várzea and terra firme forests and consequent retraction of igapó forests, with a millennial-scale reconfiguration of a mosaic of habitats in the lowlands. We conclude that this dynamism probably guided the observed patterns of speciation in the most biodiverse biome on Earth.

The Ediacara Member, South Australia: Lithofacies and palaeoenvironments of the Ediacara biota

The Ediacara Member of the Rawnsley Quartzite in the Flinders Ranges (South Australia) has undergone considerable investigation due to its placement within the package of terminal Ediacaran sediments in the region and as the host sediments of the Ediacara biota fossils. A focus on palaeoenvironment reconstruction and taphonomy has seen a succession of lithofacies models presented. These have evolved with the expansion of recognised Ediacara biota localities and prevailing palaeontological methodologies. Much of the recent descriptive lithofacies work has focused on the Nilpena fossil site in the west of the Flinders Ranges. This location is particularly fossil-rich but does not represent a “typical” section through the Ediacara Member. The Ediacara Member elsewhere in the region contains up to six parasequences with total thicknesses varying from ten to 260 m. With the exclusion of the Ikara-Chace Range region, the majority of studied locations external to Nilpena do not show clear evidence for significant (canyon-scale), intra-member erosional features. In this study we review existing facies models for the Ediacara Member and compile a “best-fit” revised facies model by incorporating the modern facies interpretations (largely based at Nilpena) and previous basin-wide observations, models and stratigraphic sections. The revised model is assessed against a series of newly measured stratigraphic sections from across the basin. We propose the division of the wave-base facies into two facies, representative of the upper and lower storm wave-base environments respectively and the re-inclusion of a facies representative of a shoreface palaeoenvironment. Additional characters and identifiers for the facies have been incorporated to aid field identification, as the ability to identify facies of fossil-bearing isolated hand-specimens can allow fossils found on scree slopes to be traced back to source beds. Likewise, palaeoenvironmental interpretations are critical to the reconstruction of Ediacara biota habitat and preservational environments.

A Basin-Wide Survey of Coastal Wetlands of the Laurentian Great Lakes: Development and Comparison of Water Quality Indices

Coastal wetlands of the Laurentian Great Lakes are vital habitats for biota of ecological and economic importance. These habitats are susceptible to water quality impairments driven by runoff from the landscape due to their location along the shoreline. Monitoring of the overall status of biotic and abiotic conditions of coastal wetlands within the Great Lakes has been ongoing for over a decade. Here, we utilize measurements of aquatic physicochemical and land cover variables from 877 vegetation zones in 511 coastal wetland sites spanning the US and Canadian shorelines of the entire Great Lakes basin. Our objective is to develop water quality indices based on physicochemical measures (Chem-Rank), land use/land cover (LULC-Rank), and their combined effects (Sum-Rank and Simplified Sum-Rank), for both vegetation zones and wetland sites. We found that water quality differed among wetland vegetation types and among Great Lakes regions, corroborating previous findings that human land use alters coastal wetland water quality. Future monitoring can use these straightforward, easy-to-calculate indices to assess the abiotic condition of aquatic habitats. Our data support the need for management efforts focused on reducing nutrient and pollution loads that stem from human activities, particularly in the developed southern portions of the Great Lakes basin.

Seasonal habitat use and community structure of rockfishes in the Gulf of Alaska

Research is needed to determine the seasonal importance of high-relief habitats, particularly those containing biotic structures to rockfishes within the Gulf of Alaska. We examined the density and community structure of commercially important rockfishes in low-relief, high-relief, and biotic habitats in the spring, summer, and winter seasons at three sites in the central Gulf of Alaska using stereo drop cameras and bottom trawls. The fish community structure within all three sites was dominated by dusky rockfish (Sebastes variabilis), northern rockfish (S. polyspinis), Pacific ocean perch (S. alutus), and harlequin rockfish (S. variegatus). There was no effect of season on community structure and density of rockfish in the study area. While there were local differences in fish density and community structure, rockfish densities throughout the study areas were higher in complex than bare habitats. Significant differences in densities between high-relief and biotic habitats were not found and the additional value of structure- forming invertebrates was not proven. Juvenile rockfish were also associated with high-relief habitat, particularly complex boulder habitat. This study advances our knowledge of seasonal habitat preferences of commercially important rockfish species with the Gulf of Alaska and emphasizes the need to consider these preferences in surveying and managing these species.

Parallels and contrasts between intermittently freezing and drying streams: From individual adaptations to biodiversity variation

Abstract Intermittently freezing and drying lotic systems are common in many parts of the world. These ecosystems provide dynamic habitats for biota, as both freezing and drying processes result in the loss of water flow along stream and river channels. However, research into the ecological effects of intermittent freezing on stream biota has remained relatively scarce compared to the recent increase in studies exploring the ecology of intermittent streams that dry. Climate change is predicted to alter the distribution and dynamics of intermittently freezing stream types. A better understanding of the responses of stream biota to intermittent freezing would inform predictions of the effects of ongoing climate change on these ecosystems. In this review, we compare the effects of both freezing and drying events on stream biota, ranging from individual‐level adaptations to population effects, community‐level biodiversity variation and food webs. Despite major contrasts in environmental conditions (e.g. the drying stream channels are exposed to a direct interaction with the riparian zone during the dry phases and the freezing stream channels are enclosed during the freezing phases), we show that both freezing and drying phenomena have pervasive effects on the structure and dynamics of aquatic stream biota. At the individual organism level, aquatic taxa use a range of physiological, morphological, life‐history, and behavioural responses to persist despite changing habitat conditions in both freezing and drying streams. The variety of organisms’ responses can result in both biodiversity increases and decreases, which may affect population and community dynamics in both ecosystem types. Future research should further explore the population and community‐level effects of freezing in stream ecosystems. Due to the ecological parallels between intermittently drying and freezing streams, approaches developed in research into drying streams may also be applied in freezing stream ecosystems. This could improve our understanding of climate change effects on freezing stream ecosystems.

Large shrubs partly compensate negative effects of grazing on hydrological function in a semi-arid savanna

Semiarid woodlands and savannas are globally important biomes that provide ecosystem goods and services such as habitat for biota and sinks for carbon, support millions of people that rely primarily on pastoralism, and supply livelihoods for about a third of the global human population. Savannas, however, are prone to degradation by overgrazing, and encroachment by woody plants, reducing their capacity to produce forage that pastoral enterprises depend on. We examined the impacts of livestock grazing and woody encroachment on soil hydrological processes, hypothesizing that heavy grazing by livestock would reduce hydrological function, whereas woody plants would increase hydrological function, therefore, partially offsetting any negative effects of overgrazing by livestock. Understanding the major drivers of soil hydrology in savanna ecosystems is important because water is a critical, yet limited resource in savannas. We found that livestock grazing reduced the early (sorptivity) and late (steady-state infiltration) stages of infiltration under both ponding and tension, and attributed this to a reduction in porosity caused by livestock trampling. Steady-state infiltration and sorptivity under ponding were greater under the canopies of woody shrubs than in open areas, partly compensating for any negative effect of grazing. Structural equation modeling revealed a direct positive effect of shrub height on hydrological functions, and an indirect effect via increases in litter cover. Our results suggest that woody plants can play important roles in driving hydrological function in savannas, counteracting the suppressive effect of livestock overgrazing on infiltration processes. Management strategies in semiarid savannas should aim to reduce trampling by livestock and retain large woody plants in order to maintain hydrological function.

The current state of the use of large wood in river restoration and management

AbstractTrees fall naturally into rivers generating flow heterogeneity, inducing geomorphological features, and creating habitats for biota. Wood is increasingly used in restoration projects and the potential of wood acting as leaky barriers to deliver natural flood management by ‘slowing the flow’ is recognised. However, wood in rivers can pose a risk to infrastructure and locally increase flood hazards. The aim of this paper is to provide an up‐to‐date summary of the benefits and risks associated with using wood to promote geomorphological processes to restore and manage rivers. This summary was developed through a workshop that brought together academics, river managers, restoration practitioners and consultants in the UK to share science and best practice on wood in rivers. A consensus was developed on four key issues: (i) hydrogeomorphological effects, (ii) current use in restoration and management, (iii) uncertainties and risks and (iv) tools and guidance required to inform process‐based restoration and management.

Chronology of Terra Firme formation in Amazonian lowlands reveals a dynamic Quaternary landscape

In the Amazonian lowlands, the shift from a large wetland dominated by flooded forests (Várzea) to the modern incised valleys bounded by extensive areas of non-flooded forests (Terra Firme) is considered a key driver of the Amazonian mega-biodiversity. Dating the sedimentary beds covered by Terra Firme forest is crucial to constrain the timing of such landscape change. Here we determined the formation ages of widespread regions of Terra Firme substrates in central Amazonian lowlands combining optically stimulated luminescence (OSL) dating, magnetostratigraphy and palinostratigraphy. Our data suggest a very dynamic fluvial system leading to a recent expansion of Terra Firme forests and retraction of Várzea forests during the late Pleistocene. The shift from an extensively flooded to non-flooded surface resulted from river incision around 45-35 ka, which potentially influenced the distribution of taxa by expanding available habitat, creating new barriers to dispersal, or changing the permeability of previous barriers. Transitions between flooded and non-flooded landscapes may have driven diversification and caused changes to species distributions, contributing to the high species diversity and biogeographic patterns currently found in the region. The late Quaternary evolution of Terra Firme substrates reveals that physical landscape changes play a major role in shaping biotic habitats even in the 104–105 years time-scales.

Ecological consequences of anomalies in atmospheric moisture and snowpack.

Although increased frequency of extreme-weather events is one of the most secure predictions associated with contemporary climate change, effects of such events on distribution and abundance of climate-sensitive species remain poorly understood. Montane ecosystems may be especially sensitive to extreme weather because of complex abiotic and biotic interactions that propagate from climate-driven reductions in snowpack. Snowpack not only protects subnivean biotas from extreme cold, but also influences forage availability through timing of melt-off and water availability. We related relative abundances of an alpine mammal, the American pika (Ochotona princeps), to measures of weather and snowpack dynamics over an 8-yr period that included before and after a year of record-low snowpack in Washington, USA. We sought to (1) quantify any change in pika abundance associated with the snowpack anomaly and (2) identify aspects of weather and snowpack that influenced abundance of pikas. Pikas showed a 1-yr lag response to the snowpack anomaly and exhibited marked declines in abundance at elevations below 1,400m simultaneous with increased abundances at higher elevations. Atmospheric moisture, indexed by vapor pressure deficit (VPD), was especially important, evidenced by strong support for the top-ranked model that included the interaction of VPD with snowpack duration. Notably, our novel application of VPD from gridded climate data for analyses of animal abundances shows strong potential for improving species distribution models because VPD represents an important aspect of weather that influences the physiology and habitat of biota. Pikas were apparently affected by cold stress without snowpack at mid elevations, whereas changes to forage associated with snowpack andVPD were influential at high and low elevations. Our results reveal context dependency in pika responses to weather and illustrate how snow drought can lead to rapid change in the abundance of subnivean animals.

Elytrigia repens co-occurs with glycophytes rather than characteristic halophytes in low-growing salt meadows on the southern Baltic Sea coast

Baltic salt meadows of the supralittoral are recognizable by a low vegetation structure of perennial plants, distinct zonation, and the presence of characteristic species of high ecological value. This semi-natural, grazing-dependent vegetation is declining in overall distribution and habitat quality. Abiotic and biotic habitat changes as well as the loss of characteristic species and a simultaneous increase of Elytrigia repens are particularly concerning. We hypothesize that, if E. repens increases due to abandonment or other causes, characteristic salt-meadow species will be affected adversely. To investigate the floristic changes and salt meadow species loss over a wide area, we used a dataset of salt meadow plots from along the southern Baltic Sea coast, partitioned by different cover ranges of E. repens. Between these groups, we compared the abundance and frequency of characteristic salt meadow species. We additionally tested (Mann-Whitney-U test) relevant structural factors, plot-based indicator values and strategy types. E. repens indicated low incidence of characteristic salt-meadow species. Soil moisture, salinity and light availability were lower where E. repens occurred; mean vegetation height was increased. Five species co-occurred with Elytrigia repens (Achillea millefolium, Holcus lanatus, Poa pratensis, Schedonorus arundinaceus, Trifolium repens), showing simultaneously a low relative abundance in the remaining dataset. We discuss our findings in terms of frequently observed vegetation changes in the light of salt meadow abandonment. In conclusion, we draw up an easy-to-use method for monitoring salt-meadow medium-term dynamics for applied nature conservation purposes.

Adaptive zone, Petersen-type communities, geographical range and ecological niche. Report 1. Defnitions and relations of the concepts

Defnition of the term adaptive zone (AZ) is amended. The Petersen-type communities (PC) are not communities in every sense of the word. They are just the areas within which the same species prevail in their abundance. An accounting gear used for identifcation of PC must be suited for catching of the most abundant species. All dominant species must be represented in the lists, regardless of whether they are seasonal or permanent components of population. Only one factor (either number of individuals or biomass) has to be used for species abundance comparison. For recognition and naming of several PC, the same number of the dominant and subdominant species should be used. Under the abovementioned conditions, if this number is equal to 1 — this method selects nothing more than AZ, which are the elementary PC. The fundamental ecological niche (EN) of a species includes its realized AZ — the real space actually coincides with its geographical range (GR). The GR is situated inside the EN, and the realized AZ is a part of GR. The GR (and sometimes EN) of different species can be partially or fully overlapped, but their AZ cannot be overlapped. Each AZ is compliant with a certain species, but not each species is compliant with AZ. AZ are available to the most dominant species and the size of AZ may serve as one of simple measures of the species capability for survival or success in their struggle for existence, and corresponds to portion of total ecological capacity of the environment used by the species. The interiors of the species GR may contain from zero to several AZ, both of this and other species. The interiors of the species AZ also contain parts of GR of other species having similar requirements to the environment (prey, predators, parasites, competitors, symbionts, and other biotic habitat factors). Potential AZ may be located both inside and outside the real GR of a species, but only within its fundamental GR. The potential AZ can be realized by changing the environmental conditions or passing through existing barriers of distribution. Transformation of potential AZ into a realized one can cause an ecological catastrophe if it breaks the existing balance and leads to signifcant redistribution of the shares of total ecological capacity available for species. But even signifcant changes in the ratios of GR and AZ of species will not cause catastrophic consequences in conditions of abundant vital resources, if ecological capacity of the environment is not flled and packing density of EN is low. Changes in the environment, as well as ontogenetic, migratory, succession and evolutionary processes cause changes in ratio of abundance between different species, including mass ones, that leads to variability of their AZ. Number, sizes, shapes, location of the AZ change progressively, both on the actual and geological time scales, and cyclically in accordance with circadian, seasonal and perennial rhythms. Therefore AZ, as well as GR, EN and communities, should be studied in dynamics and in connection with changes in the environment. Defnitions of the main terms are presented in a Supplement.

Continents as Units for the Study of Floristic Assembly and Biodiversity: Focus on North America

Continents as Units for the Study of Floristic Assembly and Biodiversity: Focus on North America

Describing soil quality with aggregate index for Msange irrigation scheme of Tanzania

Soil quality is an important and integral aspect of soil health which is defined as the continued capacity of the soil to function as a living system within the ecosystem and land use boundaries. It refers to the capacity of soil to supply nutrients, maintain suitable biotic habitat and resist degradation. This study focuses on describing the soil quality through aggregate index termed as Soil Quality Index (SQI). The assessment of soil quality involves physical and chemical soil parameters along with the local climatic conditions and the experts’ opinion. The proposed aggregation method utilizes three scoring functions; ‘more is better’, ‘less is better’ and ‘optimum’ for which the score is interpreted either as very low, low, medium, high or very high. The methodology has been applied to Msange irrigation scheme which falls under semi‐arid climate conditions of Tanzania. The results show that the average SQI in the Msange irrigation scheme is 0.565 for the silt loam soil and can be classified as medium quality. In order to improve the soil quality and hence the land productivity, one should improve the organic matter contents, available water and nutrients availability to the soil. It is hoped that this study will be a baseline study on soil quality evaluation for effective agricultural practices.

Carbon budgets of top- and subsoil food webs in an arable system

This study assessed the carbon (C) budget and the C stocks in major compartments of the soil food web (bacteria, fungi, protists, nematodes, meso- and macrofauna) in an arable field with/without litter addition. The C stocks in the food web were more than three times higher in topsoil (0–10 cm) compared to subsoil (>40 cm). Microorganisms contained over 95% of food web C, with similar contributions of bacteria and fungi in topsoil. Litter addition did not alter C pools of soil biota after one growing season, except for the increase of fungi and fungal feeding nematodes in the topsoil. However, the C budget for functional groups changed with depth, particularly in the microfauna. This suggests food web resilience to litter amendment in terms of C pool sizes after one growing season. In contrast, the distinct depth dependent pattern indicates specific metacommunities, likely shaped by dominant abiotic and biotic habitat properties.

Environmental flow assessment for the Yaselda River in its Selets reservoir section

A comparative analysis of five environmental flow assessment methods was performed on the example of the Yaselda River in its Selets section. The significant difference in their results was revealed. The threshold methods provide a uniform environmental flow values along the year. The values vary among the methods. It is explained that the methods were developed in different economic and social conditions. Practically identical results were obtained with the methods used in Belarus and Ukraine. However, the other method would assume the environmental flow value above the natural flow in some periods of the year. The method of exceedance probability transfer appears to be the most promising one. Partial zoning of probability transfer parameters would make the method more efficient. For management purposes it is proposed to introduce yearly adjustments of environmental flow rates taking into account the discharges of previous years. This would allow to re-water floodplains overdried in dry years and recover habitats for biota.

Anthropogenic disturbance homogenizes seagrass fish communities.

Anthropogenic activities have led to the biotic homogenization of many ecological communities, yet in coastal systems this phenomenon remains understudied. In particular, activities that locally affect marine habitat-forming foundation species may perturb habitat and promote species with generalist, opportunistic traits, in turn affecting spatial patterns of biodiversity. Here, we quantified fish diversity in seagrass communities across 89 sites spanning 6° latitude along the Pacific coast of Canada, to test the hypothesis that anthropogenic disturbances homogenize (i.e., lower beta-diversity) assemblages within coastal ecosystems. We test for patterns of biotic homogenization at sites within different anthropogenic disturbance categories (low, medium, and high) at two spatial scales (within and across regions) using both abundance- and incidence-based beta-diversity metrics. Our models provide clear evidence that fish communities in high anthropogenic disturbance seagrass areas are homogenized relative to those in low disturbance areas. These results were consistent across within-region comparisons using abundance- and incidence-based measures of beta-diversity, and in across-region comparisons using incidence-based measures. Physical and biotic characteristics of seagrass meadows also influenced fish beta-diversity. Biotic habitat characteristics including seagrass biomass and shoot density were more differentiated among high disturbance sites, potentially indicative of a perturbed environment. Indicator species and trait analyses revealed fishes associated with low disturbance sites had characteristics including stenotopy, lower swimming ability, and egg guarding behavior. Our study is the first to show biotic homogenization of fishes across seagrass meadows within areas of relatively high human impact. These results support the importance of targeting conservation efforts in low anthropogenic disturbance areas across land- and seascapes, as well as managing anthropogenic impacts in high activity areas.

Evaluation of wetted surface area of commercial ships as biofouling habitat flux to the United States

Commercial ships inadvertently transfer vast numbers of living organisms beyond their evolutionary ranges, sometimes resulting in invasions of distant marine habitats. Biofouling on ship hulls translocate organisms that cling to the undersides and interstices of ships that function as hard substrate habitat for biota. Because biofouling accumulates over space and time continually, it poses risk to all ports visited. To better understand the potential magnitude of the biofouling vector in the United States, we compiled information on ship-specific dimensions as well as actual arrival histories of the fleets of ships calling at U.S. ports (2011–2014) in an effort to calculate wetted surface area (WSA) flux to the U.S. The annual mean flux of WSA from overseas bioregions to the U.S. is 333 km2 year−1. An additional 177 km2 year−1 of WSA moves among the eight distinct biogeographic regions of the lower 48 United States. We confirm that over 90% of all global marine bioregions (120 of 132 identified by IUCN) are visited by commercial ships within five port calls of arriving to the U.S. Our analysis is the first ever to quantify the extent of WSA flux among global marine bioregions and underscores the urgent need for management approaches and technologies that will reduce associated invasion risks.