Toxicological Considerations of Contaminants in the Terrestrial Environment for Ecological Risk Assessment

The terrestrial environment acts as a “sink” for contaminants that have been purposely or accidentally released into the environment. Science and policy that support protective measures for terrestrial ecosystems have run behind those of aquatic toxicology and water quality concerns. As a result ecological risk assessment (ERA) involving terrestrial environments tends to be conducted at a simplistic level, relying on numeric targets (soil quality criteria) as a basis for decision-making. However, soil criteria for ecological receptors are somewhat deficient in terms of the numbers available and the data that supports these numbers. Direct toxicity assessments (DTA) for terrestrial environments, such as those used for water quality evaluations, can provide additional useful information about the toxicity and bioavailability of mixtures of contaminants present in soils. This article outlines the approaches used for assessing the toxicity of soil contaminants in terrestrial environments and critiques their advantages and pitfalls.     

Degeneration patterns of the olfactory receptor genes in sea snakes

The sense of smell relies on the diversity of olfactory receptor (OR) repertoires in vertebrates. It has been hypothesized that different types of ORs are required in terrestrial and marine environments. Here we show that viviparous sea snakes, which do not rely on a terrestrial environment, have significantly lost ORs compared with their terrestrial relatives, supporting the hypothesis. On the other hand, oviparous sea snakes, which rely on a terrestrial environment for laying eggs, still maintain their ORs, reflecting the importance of the terrestrial environment for them. Furthermore, we found one Colubroidea snake (including sea snakes and their terrestrial relatives)‐specific OR subfamily which had diverged widely during snake evolution after the blind snake–Colubroidea snake split. Interestingly, no pseudogenes are included in this subfamily in sea snakes, and this subfamily seems to have been expanding rapidly even in an underwater environment. These findings suggest that the Colubroidea‐specific ORs detect nonvolatile odorants.     

The role of waves in the colonisation of terrestrial sediments deposited in the marine environment

Elevated rates of sediment run-off, as a result of changes in land-use and climate, are a significant threat to marine coastal communities, with a potential to cause broad-scale, long-term alteration of habitats. Individual sedimentation events can smother estuarine flats with terrigenous sediments, creating a significant disturbance to local benthic communities. Variations in the degree to which a habitat is altered, the rate at which mixing occurs, and species-specific dispersal and responses to the altered habitat, suggest that colonisation of terrestrial sediment depositions will vary with location, both between and within estuaries. This study was designed to explore the effect that variations in wave-induced hydrodynamics would have on long-term colonisation of terrestrial sediment depositions on intertidal flats. Sites for the experimental deposition of terrestrial sediment were located along a gradient in wave exposure, with only limited variation in immersion times (30 min) and ambient sediment particle sizes (predominantly fine sand). Over 20 months, periodic measurements were made of factors predicted to affect colonisation: the sediment characteristics of the deposited sediment; local-scale wave climate; bioturbation of the deposited sediment; and local populations of benthic invertebrates. Neither opportunistic use of the new resource, progressive recovery or facilitation by colonising macrofauna was observed. Little vertical mixing of the deposited and existing sediment by either waves or bioturbators occurred; instead bedload transport was the dominant process. Local differences in hydrodynamic conditions and macrobenthic communities resulted in site-specific colonisation of the experimental plots. The strength and duration of the macrofaunal response to deposited sediment observed in this study suggest that chronic small-scale (m's) patchy deposition of terrestrial sediment in the intertidal marine environment has a strong potential to alter both habitats and communities.     

Survival and colonisation potential of photoautotrophic microorganisms within a glacierised catchment on Svalbard, High Arctic

The survival and colonisation potential of photoautotrophic microbes (cyanobacteria and microalgae) were investigated in three terrestrial environments within a glacierised catchment on Svalbard: old vegetation-covered soil, recently deglaciated barren soil and subglacial sediments. One-year reciprocal transplant incubations of photoautotrophic microbial communities from the three soil/sediment environments were conducted in order to reveal the autochthonous or allochthonous origin of the present photoautotrophs. The abundance and taxonomic composition of photoautotrophic microbes and their changes over time and between soil/sediment types and physico-chemical characteristics of the soils/sediments were determined. The recovery time of a photoautotrophic community by import of cells was between several months in subglacial and vegetated soils and up to 27 years in proglacial soils. No active growth was recorded in subglacial sediments, whilst positive growth, and so the potential for autochthonous recovery, was found in proglacial and vegetated soils. The most suitable environment for the survival of transplanted microbes was provided in proglacial soil. We show here that the new proglacial substrata can be successfully colonised by photoautotrophic microbes, and that input of allochthonous cells may, in some cases, exceed in situ microbial growth. Whilst the subglacial environment is rather a conduit for photoautotrophic microbes than a place of growth and production, the supply of viable photoautotrophs in it is relatively high and may serve as a significant resource of nutrients for subglacial microbial communities.     

Why are there so few evolutionary transitions between aquatic and terrestrial ecosystems?

Insects and flowering plants have rarely invaded the sea. Explanations for this have traditionally centered on the unique shortcomings of these groups in the marine environment. We show, however, that transitions among terrestrial, freshwater, and marine environments are infrequent in all major plant and animal clades except tetrapod vertebrates. In general, well-adapted incumbents are at a competitive advantage over would-be invaders from a physically different habitat. Data on the times and places of transition are consistent with our contention that evolutionary transitions among physically different environments are most likely when incumbents in the recipient environment exist in a regime of low-intensity competition and prcdation, as in terrestrial communities of the middle Paleozoic or the land biotas of oceanic islands. Freshwater environments, in which inferred intensities of predation are lower than in most marine and terrestrial environments, offer less biotic resistance to invaders than do communities in the sea or on land. Most invaders respond to novel physical circumstances by shutting down their metabolic machinery, and therefore add to their subordinate status as competitors with active incumbents. Only active tetrapods, particularly those with high and endothermically driven rates of metabolism, have successfully overcome this limitation.     

How are the life history strategies of Antarctic terrestrial invertebrates influenced by extreme environmental conditions?

1. 1. Features of life history strategies of Antarctic terrestrial invertebrates are reviewed and compared with the predictions of two widely-used general life history models.

2. 2. Many features observed are consistent with the predictions of “adversity-” or “stress-selected” life histories, although “ruderal” characteristics are also observed.

3. 3. Many features are plesiotypic for the taxonomic groups concerned, suggesting a lack of evolved adaptations within the Antarctic biota.

4. 4. A large degree of flexibility is found in the life histories; this flexibility itself may allow passage of environmentally-imposed selective filters limiting colonisation and development in isolated and extreme terrestrial habitats.

5. 5. In general, Antarctic terrestrial invertebrates may be regarded as pre-adapted for survival of the various stresses imposed by their extreme environment.

     

Does size matter? Examining the drivers of mammalian vocalizations

Previous studies of the vocalization frequencies of mammals have suggested that it is either body mass or environment that drives these frequencies. Using 193 species across the globe from the terrestrial and aquatic environments and a model selection approach, we identified that the best‐supported model for minimum and maximum frequencies for vocalization included both body mass and environment. The minimum frequencies of vocalizations of species from all environments retained the influence of body mass. For maximum frequency however, aquatic species are released from such a trend with body mass having little constraint on frequencies. Surprisingly, phylogeny did not have a strong impact on the evolution of the maximum frequency of mammal vocalizations, largely due to the pinniped species divergence of frequency from their carnivoran relatives. We demonstrate that the divergence of signal frequencies in mammals has arisen from the need to adapt to their environment.     

Captive Bottlenose Dolphins (Tursiops truncatus) Spontaneously Using Water Flow to Manipulate Objects

Several terrestrial animals and delphinids manipulate objects in a tactile manner, using parts of their bodies, such as their mouths or hands. In this paper, we report that bottlenose dolphins (Tursiops truncatus) manipulate objects not by direct bodily contact, but by spontaneous water flow. Three of four dolphins at Suma Aqualife Park performed object manipulation with food. The typical sequence of object manipulation consisted of a three step procedure. First, the dolphins released the object from the sides of their mouths while assuming a head-down posture near the floor. They then manipulated the object around their mouths and caught it. Finally, they ceased to engage in their head-down posture and started to swim. When the dolphins moved the object, they used the water current in the pool or moved their head. These results showed that dolphins manipulate objects using movements that do not directly involve contact between a body part and the object. In the event the dolphins dropped the object on the floor, they lifted it by making water flow in one of three methods: opening and closing their mouths repeatedly, moving their heads lengthwise, or making circular head motions. This result suggests that bottlenose dolphins spontaneously change their environment to manipulate objects. The reason why aquatic animals like dolphins do object manipulation by changing their environment but terrestrial animals do not may be that the viscosity of the aquatic environment is much higher than it is in terrestrial environments. This is the first report thus far of any non-human mammal engaging in object manipulation using several methods to change their environment.     

Comparing scavenging in marine and terrestrial ecosystems: a case study with fish and gull carcasses in a small Mediterranean island

Carrion consumption by scavengers is a key component of both terrestrial and aquatic food webs. However, there are few direct comparisons of the structure and functioning of scavenging communities in different ecosystems. Here, we monitored the consumption of 23 fish (seabream Sparus aurata) and 34 bird (yellow-legged gull Larus michahellis) carcasses on a small Mediterranean island (Isla Grosa, southeastern Spain) and surrounding waters in summer to compare the structure of the scavenger assemblages and their carrion consumption efficiencies in terrestrial and shallow water habitats. Scavenging was highly efficient both in marine and terrestrial environments, especially in the presence of a highly abundant vertebrate scavenger species, the yellow-legged gull. The vertebrate scavenger community was richer in the marine environment, whereas the invertebrate community was richer on land. The scavenger network was usually well-structured (i.e., nested), with the exception of the community associated with fish terrestrial carcasses, which were almost monopolized by yellow-legged gulls. In contrast, gulls left conspecific carcasses untouched, thus allowing longer persistence of gull carcasses on land and their exploitation by a diverse insect community. Our study shows important differences in the scavenging process associated with environment and carcass type. Promising avenues for further eco-evolutionary and applied research arise from the comparison of scavenging processes in terrestrial and marine ecosystems, from small islands to continents.     

Wintering space use and site fidelity in a nomadic species,the snowy owl

Migratory species can exploit many habitats over vast geographic areas and adopt various patterns of space and habitat use throughout their annual cycle. In nomadic species, determinants of habitat use during the non‐breeding season are poorly known due to the unpredictability of their movement patterns. Here, we analysed variability in wintering space and habitat use by a highly nomadic species, the snowy owl, in eastern North America. Using 21 females tracked by satellite telemetry between 2007 and 2016, we 1) assessed how space use patterns in winter varied according to the type of environment (marine vs terrestrial), latitudinal zone (Arctic vs temperate), local snow conditions and lemming densities and 2) investigated winter habitat and site fidelity. Our results confirmed a high inter‐individual variation in patterns of habitat use by wintering snowy owls. Highly‐used areas were concentrated in the Arctic and in the marine and coastal environments. Owls wintering in the marine environment travelled over longer distances during the winter, had larger home ranges and these were divided in more smaller zones than individuals in terrestrial environments. Wintering home range sizes decreased with high winter lemming densities, use of the marine environment increased following high summer lemming densities, and a thick snow cover in autumn led to later settlement on the wintering ground. Contrary to expectations, snowy owls tended to make greater use of the marine environment when snow cover was thin. Snowy owls were highly consistent in their use of a given wintering environment and a specific latitudinal zone between years, but demonstrated flexibility in their space use and a modest site fidelity. The snowy owls’ consistency in wintering habitat use may provide them with advantages in terms of experience but their mobility and flexibility may help them to cope with changing environmental conditions at fine spatial scale.     

Life in the maelstrom: The biomechanics of wave-swept rocky shores

Nowhere on earth is water motion more violent than in the surf zone of rocky shores, and the hydrodynamic stresses imposed on plants and animals by wave-induced flows far exceed any in terrestrial or oceanic environments. Despite the harshness of the physical environment, wave-swept habitats support persistent, diverse communities. Knowledge of the physical mechanisms by which water motion affects plants and animals and of the ways in which they cope with their environment is essential for understanding the community ecology of these turbulent habitats.     

How muscles accommodate movement in different physical environments: aquatic vs. terrestrial locomotion in vertebrates.

Representatives of nearly all vertebrate classes are capable of coordinated movement through aquatic and terrestrial environments. Though there are good data from a variety of species on basic patterns of muscle recruitment during locomotion in a single environment, we know much less about how vertebrates use the same musculoskeletal structures to accommodate locomotion in physically distinct environments. To address this issue, we have gathered data from a broad range of vertebrates that move successfully through water and across land, including eels, toads, turtles and rats. Using high-speed video in combination with electromyography and sonomicrometry, we have quantified and compared the activity and strain of individual muscles and the movements they generate during aquatic vs. terrestrial locomotion. In each focal species, transitions in environment consistently elicit alterations in motor output by major locomotor muscles, including changes in the intensity and duration of muscle activity and shifts in the timing of activity with respect to muscle length change. In many cases, these alterations likely change the functional roles played by muscles between aquatic and terrestrial locomotion. Thus, a variety of forms of motor plasticity appear to underlie the ability of many species to move successfully through different physical environments and produce diverse behaviors in nature.     

Hypomethylation of the aquatic invasive plant,Ludwigia grandiflora subsp. hexapetala mimics the adaptive transition into the terrestrial morphotype

Ongoing global changes affect ecosystems and open up new opportunities for biological invasion. The ability of invasive species to rapidly adapt to new environments represents a relevant model for studying short-term adaptation mechanisms. The aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala, is classified as harmful in European rivers. In French wet meadows, this species has shown a rapid transition from aquatic to terrestrial environments with emergence of two distinct morphotypes in 5 years. To understand the heritable mechanisms involved in adjustment to such a new environment, we investigate both genetic and epigenetic as possible sources of flexibility involved in this fast terrestrial transition. We found a low overall genetic differentiation between the two morphotypes arguing against the possibility that terrestrial morphotype emerged from a new adaptive genetic capacity. Artificial hypomethylation was induced on both morphotypes to assess the epigenetic hypothesis. We analyzed global DNA methylation, morphological changes, phytohormones and metabolite profiles of both morphotype responses in both aquatic and terrestrial conditions in shoot and root tissues. Hypomethylation significantly affected morphological variables, phytohormone levels and the amount of some metabolites. The effects of hypomethylation depended on morphotypes, conditions and plant tissues, which highlighted differences among the morphotypes and their plasticity. Using a correlative integrative approach, we showed that hypomethylation of the aquatic morphotype mimicked the characteristics of the terrestrial morphotype. Our data suggest that DNA methylation rather than a new adaptive genetic capacity is playing a key role in L. grandiflora subsp. hexapetala plasticity during its rapid aquatic to terrestrial transition.     

Spatial and temporal patterns of non-colonial boring organisms (polychaetes,sipunculans and bivalve molluscs) in Porites at Lizard Island,Great Barrier Reef

A study of the spatial and temporal patterns of colonisation by non-colonial boring organisms to dead Porites coral substrate was conducted at Lizard Island, Great Barrier Reef over a 4 year period. These fluctuations were analysed for each group of borers, and most exhibited strong site preferences, with preferred sites being on the windward slope in 10 m and on the reef flat in 1 m. A lagoonal patch reef site exhibited consistently low colonisation. Most groups showed inter-year variations in colonisation with spring/early summer dominating. These variations are discussed in terms of what is known about their life histories. These results together with those of Kiene (in preparation) which document varying rates of bioerosion, at these sites over the same time period, demonstrate that variations in borer colonisation are responsible for the variations in rates of bioerosion calculated. Thus rates of bioerosion by borers will vary significantly between different reef environments.     

Latitudinal variation in habitat specificity of ameronothrid mites (Oribatida)

Ameronothroid mites, including Ameronothridae, Fortuyniidae and Selenoribatidae, are unique among the Oribatida through having a global distribution from the tropics to the poles, and occupying a diversity of habitats including terrestrial, marine and freshwater. Their ecological diversification is of considerable interest from both the perspective of evolution over geological timescales, and the detail of the underlying processes. Given their widespread global distribution, it seems likely that historical global events (tectonic and climatic) have played a fundamental role in their ecological diversification. Previous studies of sub-Antarctic island arthropods have generated considerable circumstantial evidence in support of glaciation being a primary factor influencing ecological patterns: lower habitat specificity and weaker interspecific interactions are associated with more recent (postglacial) vegetated terrestrial biotopes, as compared to the older epilithic and littoral biotopes (which are assumed to have been present, albeit reduced in extent, during Neogene glacial maxima). Here, we use ameronothrid mites as a case study to examine the extent to which the above island scenario generalizes globally across latitudes affected by glaciation. We show that, unlike congeners or even conspecifics at lower latitudes in each hemisphere which are restricted to marine environments, the species found at higher latitudes (especially Alaskozetes antarcticus, Ameronothrus dubinini, Ameronothrus lineatus, and Halozetes belgicae) show greater affinity for terrestrial environments. They show a transition or expansion of habitat use (from marine-influenced to terrestrial habitats) implicit with a lower degree of habitat specificity, in relation to increasing latitude. We contend that the terrestrial environment at higher latitudes in both hemispheres has been colonized by these ameronothrid mite species following the various glaciation events, facilitated by a lack of competition experienced in their low diversity communities, in a manner which represents a larger scale demonstration of the processes described on sub-Antarctic islands.     

Bioremediation Potential of Mercury by Bacillus Species Isolated from Marine Environment and Wastes of Steel Industry

ABSTRACT The marine environment is the most dynamic and most variable among the natural environments present on the globe due to its continuously changing patterns of salinity, sea surface temperature, pH, and pressure. Thus, bacteria inhabiting this environment possess the inbuilt mechanisms of adaptation necessary in such fluctuating environmental conditions, and the harboring of heavy metal–resistant genes adds to their efficiency with regard to metal remediation compared with their terrestrial counterparts. Two highly mercury-resistant isolates, one from the marine environment and another from steel industry waste, were identified as Bacillus thuringiensis PW-05 and Bacillus sp. SD-43, respectively, by 16S rRNA gene sequence analysis. When various characters of these two isolates, e.g., biochemical, morphological, antibiotic resistance, and tolerance to other heavy metals, were analyzed, they were found to share common features. However, the marine Bacillus isolate (PW-05) was found to be more capable than its terrestrial counterpart in terms of mercury volatilization capability, i.e., 94.72% in the case of PW-05 and 60.06% in the case of SD-43. Hence, marine bacteria can be used more efficiently than their terrestrial counterparts for enhanced bioremediation of mercury in contaminated envi-ronments.     

Phenological shifts assist colonisation of a novel environment in a range‐expanding raptor

In a rapidly changing world understanding the capacity of populations to adapt to novel environments is increasingly urgent. Timing of breeding can be a highly flexible trait and adjustments in this trait can potentially buffer populations from climate change and facilitate the colonisation of new environments. Recent range‐expansions into novel climatic regimes provide a valuable opportunity to investigate the implications of plasticity in timing of breeding for population processes. Black sparrowhawks have recently colonised the Cape Peninsula of South Africa where they experience dramatically different weather patterns to those in their historical range. These include a total reversal in the rainfall regime, with the majority of rain falling in the winter as opposed to the summer months. We investigate the breeding phenology of black sparrowhawks in relation to both regional and local climate variation and, using a long‐term dataset, explore the implications of phenological shifts for reproductive success and population growth following colonisation. In the recently colonised Cape Peninsula the breeding season began up to three months earlier than within their historical range and these early breeding attempts produced more offspring. Population models suggested that this adjustment assisted the colonisation of the Cape Peninsula, reducing the probability of extinction by 23%. Contrary to expectations, we found little support for the hypothesis that black sparrowhawks were responding to local variation in rainfall. We suggest that shifts in breeding phenology may be driven in part by other novel processes, such as interspecific competition for nest sites and lower temperatures during late summer. These results provide insight into the processes that facilitated the colonisation of a novel climatic regime highlighting the potential role of a diverse range of factors.     

Hexapoda phylogeny: implications for an aquatic origin hypothesis

Emergence from an aquatic environment to the land is one of the major evolutionary transitions within the arthropods. It is often considered that the first hexapods, and especially the first Collembola, went from the sea through intermediate freshwater environments to colonize fully terrestrial ecosystems. To understand the ancestral ecology of hexapods, a phylogenetic framework is used. By mapping ecological attributes onto the phylogeny, it is shown that hexapods colonized terrestrial environments directly from marine environment without a transition through freshwater. An edaphic life-style is the basal state for Collembola and more generally for hexapods as a whole. Aquatic ecology is inferred to be a secondary change that occurred several times independently, particularly in some group of Collembola and Pterygota. The answer is ambiguous for Pterygota, whether the first Pterygota had aquatic larvae and reversed toward fully terrestrial in Neoptera, or aquatic larvae appeared independently in Odonata and Ephemeroptera. Subsequently, aquatic larvae were secondarily acquired in various groups independently (e.g. Plecoptera, Trichoptera, Coleoptera).     

Evidence of positive selection suggests possible role of aquaporins in the water-to-land transition of mudskippers

Aquaporins are integral membrane proteins that exchange water and small solutes. They played an important role in the colonisation of terrestrial environments by tetrapod ancestors via the appearance of three exclusive paralogs. Like early tetrapods, mudskippers represent an independent case of amphibious lifestyle evolution that is unparalleled by other extant fish groups. Given this lifestyle parallelism and that aquaporins were relevant for tetrapod terrestrialisation, this study examines the aquaporins in mudskippers to investigate whether similar changes in aquaporins could have possibly occurred during their water-to-land transition. We have catalogued aquaporin genes in four mudskipper genomes and studied their diversity and molecular evolution (including detection of positive selection) in a broad phylogenetic context of vertebrates. Our genomic screening returned 55 aquaporin genes for mudskippers (none of them constituting novel paralogs) that can be assigned to 10 different known classes. We detected signatures of positive selection in AQP10a and AQP11b in mudskippers (both the entire clade and the clade containing the most terrestrial species, implying different evolutionary times). This suggests possible alteration of the molecular function of such paralogs caused by changes at specific protein sequence positions, some of them located in relatively close proximity to parts of the molecule involved in pore formation and substrate selectivity. Given the importance of aquaporins for osmotic regulation in fishes, it might be possible that these selective changes (perhaps allowing permeability to new solutes) could have played a role during the adaptation of mudskippers to an amphibious lifestyle.