Alter Ecosystem Function Research Articles

A meta-analysis on decomposition quantifies afterlife effects of plant diversity as a global change driver

Biodiversity loss can alter ecosystem functioning; however, it remains unclear how it alters decomposition—a critical component of biogeochemical cycles in the biosphere. Here, we provide a global-scale meta-analysis to quantify how changes in the diversity of organic matter derived from plants (i.e. litter) affect rates of decomposition. We find that the after-life effects of diversity were significant, and of substantial magnitude, in forests, grasslands, and wetlands. Changes in plant diversity could alter decomposition rates by as much as climate change is projected to alter them. Specifically, diversifying plant litter from mono- to mixed-species increases decomposition rate by 34.7% in forests worldwide, which is comparable in magnitude to the 13.6–26.4% increase in decomposition rates that is projected to occur over the next 50 years in response to climate warming. Thus, biodiversity changes cannot be solely viewed as a response to human influence, such as climate change, but could also be a non-negligible driver of future changes in biogeochemical cycles and climate feedbacks on Earth.

How Does Mining Salinisation Gradient Affect the Structure and Functioning of Macroinvertebrate Communities?

Elevated salinity creates degrading conditions for the development of aquatic biota in different regions of the world. There is a need for research on freshwater salinisation in order to understand how this stressor alters ecosystem function and to predict changes in biodiversity globally. Such data are missing from Central Europe, and therefore, the presented study was performed in inland anthropogenic ponds with different salinity levels located in the second largest European hard coal basin. The researcher indicated a positive correlation between water salinity and the biomass and density of macrozoobenthos as well as the percentage of shredders and the abundance of alien species, whereas there was a decrease in taxa diversity and richness and the abundance of filtering and gathering collectors and predators along with increasing salinity. The survey showed that a high level of nutrients and organic matter were also significantly correlated with the distribution of the macroinvertebrate taxa and functional feeding groups. The conducted research confirmed that mining salinisation acts as a strong filter that shapes the biodiversity because it affects the composition, abundance, biomass and functional traits of benthic macroinvertebrates and significantly contributes to the invasion of alien species.

Impeded Macrofaunal Colonization and Recovery Following Marine Deposition of Inert and Organically Modified Mine-Tailings

Fine-grained, waste rock (or tailings) produced during mining processes are the main waste product following the extraction of valuable minerals and metals from ores. The proximity of mineral resources to coastal regions in some countries has meant that the organically inert mine tailings are often deposited into the marine environment as a submarine tailings placement or STP. This creates a real environmental challenge since the deposition of tailings at the seafloor can completely smother the benthic environment and reduce benthic biodiversity and alter ecosystem function. A limited number of studies have attempted to quantify the speed of seafloor recovery following tailings disposal and have suggested that one of the main factors limiting seafloor colonisation is the lack of organic matter of the tailings deposited. In this experimental study, we used hydrodynamically unbiased settlement trays within a complete randomised block design to test whether macrofaunal colonisation of mine tailings, and resemblance towards ambient assemblages, is enhanced when tailings become more enriched in organic C (Corg). Our experiment showed that tailings with Corg contents 1% exhibited lower faunal abundance and biomass and different macrofaunal community composition after one year compared to background sediments. Macrofaunal species richness (defined as the total number of different taxa) in the 0% and 0.5% Corg tailings treatments, however, was statistically indistinguishable from ambient intertidal sediments after one year. Furthermore, macrofaunal community structure was more similar to that of the background intertidal sediments after one year, which collectively suggest partial recovery of seafloor biodiversity in tailings with zero to low Corg levels. Nevertheless, macrofaunal abundance and biomass in these treatments remained significantly less than the background community after one year suggesting factors other than the Corg content of tailings may be structuring macrofaunal colonisation and impeding seafloor recovery of tailings deposits. We propose that the non-marine physical structure of the tailings particles, which show great angularity is predominantly responsible for the observed delayed recovery.

A long-term and comprehensive assessment of urbanization-induced impacts on ecosystem services in the capital city of India

Globally, the present rate of urbanization in mega-urban centers is altering ecosystem functions and resultant ecosystem services of the landscapes. The natural and semi-natural ecosystems within the urban regions are under threat of loss and degradation. Estimating the economic values of the ecosystem services obtained from these natural and semi-natural ecosystems can play an important role in urban policy and decision making. The main objective of this paper is to quantify the changes in ecosystem service values (ESVs) in response to land use land cover (LULC) dynamics and urbanization in the capital city of India, Delhi. Using satellite imageries over the past two decades (1998–2018) we show the estimated changes in ESVs with the global value coefficient (VC) of proximate biomes. The study relies on benefit transfer approach of ESs valuation wherein the ESVs of proximate biomes, derived from one/multiple study site, are used in assessing ESVs at another site. For determining the reliability of the study, a sensitivity analysis is performed to check the effectiveness of VC. The results show a total decline of ecosystem services (ESs) in monetary terms by US$ 7.614 million ha−1 year−1 from 1998 to 2018 with prominent changes in LULC. The change analysis shows a loss (US$ 3.6141 million) of regulatory and provisional services. The prominent part (US$ 2.675 million) of this loss was due to decline in city forest cover by 6426.09 ha. The city has benefitted from initiatives in implementation of biodiversity parks and plantation drives, but also suffers widespread loss of forest over the years. The ESs monitoring at the city administrative divisions (i.e. district-wise) highlights the importance of conservation of natural ecosystems within the urban area with distribution equity. The results provide insights that should be considered for urban planning in order to protect natural resources, ESs, and thus overall well-being of residents.

Demographic trends in community functional tolerance reflect tree responses to climate and altered fire regimes.

Forests of the western United States are undergoing substantial stress from fire exclusion and increasing effects of climate change, altering ecosystem functions and processes. Changes in broad-scale drivers of forest community composition become apparent in their effect on survivorship and regeneration, driving demographic shifts. Here we take a community functional approach to forest demography, by investigating mean drought or shade functional tolerance in community assemblages. We created the Community Mean Tolerance Index (CMTI), a response metric utilizing drought/shade tolerance trade-offs to identify communities undergoing demographic change from a functional trait perspective. We applied the CMTI to Forest Inventory and Analysis data to investigate demographic trends in drought and shade tolerance across the southern Rocky Mountains. To find the major drivers of change in community tolerance within and across forest types, we compared index trends to climate and fire-exclusion-driven disturbance, and identified areas where demographic change was most pronounced. We predicted that greater shifts in drought tolerance would occur at lower forest type ecotones where climate stress is limiting and that shifts in shade tolerance would correspond to excursions from the historic fire regime leading to greater changes in forest types adapted to frequent, low-intensity fire. The CMTI was applied spatially to identify sites likely to transition to oak shrubfield, where disturbance history combined with a species-driven demographic shift toward drought tolerance. Within forest types, lower elevations are trending toward increased drought tolerance, while higher elevations are trending toward increased shade tolerance. Across forest types, CMTI difference peaked in mid-elevation ponderosa pine and mixed-conifer forests, where fire exclusion and autecology drive demographic changes. Peak CMTI difference was associated with fire exclusion in forest types adapted to frequent fire. At higher elevations, site-level stand dynamics appear to be influencing demographic tolerance trends more than broad climate drivers. Through a community demographic approach to functional traits, the CMTI highlights areas and forest types where ecosystem function is in the process of changing, before persistent vegetation type change occurs. Applied to regional plot networks, the CMTI provides an early warning of shifts in community functional processes as climate change pressures continue.

Effects of dibutyl phthalate contamination on physiology, phytohormone homeostasis, rhizospheric and endophytic bacterial communities of Brassica rapa var. chinensis

Phthalates are plasticizers and are ubiquitously detected in the environment, frequently at mg/kg levels. The present study aimed to evaluate the effects of dibutyl phthalate (DBP) on germination, growth, enzyme activity, phytohormone homeostasis and bacterial communities of two cultivars of Brassica rapa var. chinensis. The germination rate was decreased up to 20% compared to the control, and the growth of the vegetables was severely inhibited at the early stage when exposed to DBP at 20 mg/kg. Antioxidant defense enzyme activities and malondialdehyde (MDA) content increased upon exposure to DBP. A dose-response of auxin (IAA) was observed after a 2 d exposure. Gibberellin (GA3) and abscisic acid (ABA) responded at day 10 under DBP stress. GA3 did not show a clear dose-response effect and ABA increased about 3 times as the DBP concentration increased from 2 to 20 mg/L. Microbial population shifts were observed, especially in rhizosphere soil and roots. No obvious change occurred for the α diversity of rhizospheric bacteria among different treatments. Chao1, Shannon and Simpson indices of the root endophytic bacteria showed a decreasing trend with increasing DBP supplementation, while all the indices increased in shoot endophytic bacteria in comparison to the control. The results indicated that exposure to DBP may compromise the fitness of the leafy vagetables and alter the endophytic and rhizospheric bacteria, which might further affect the nutrients of the vegetables and alter ecosystem functions.

Black-Tailed Prairie Dog (Cynomys ludovicianus) Reintroduction Can Limit Woody Plant Proliferation in Grasslands

Tree and shrub proliferation has been widespread in grasslands worldwide, and has altered ecosystem function and wildlife habitat. Several causes have been proposed for the woody plant encroachment phenomenon. The widespread eradication of a native keystone herbivore in North American grasslands, the prairie dog (Cynomys spp.), is one potential contributing factor that has received relatively little attention. We hypothesized prairie dogs would have historically suppressed woody plants by creating “browse traps” through their systematic clipping of vegetation. We tested this hypothesis by conducting surveys and experimentally manipulating shrub accessibility via exclosures and artificial saplings on and around recently reestablished black-tailed prairie dog (C. ludovicianus) colonies in southeastern Arizona, USA. Shrubs were common on the nascent colonies (mean ± SE = 132 ± 32.7 plants ha-1), but at substantially reduced densities compared to off colonies (305 ± 94.9 plants ha-1). Among branches placed on colonies to simulate ‘saplings’, 89% were damaged within three days of ‘planting’, whereas those placed off colonies were virtually untouched. This was true for both a deciduous, N2-fixing shrub (velvet mesquite, Prosopis velutina) and an evergreen non-N2-fixing shrub (creosote bush, Larrea tridentata). Prairie dogs on newly established colonies did not extirpate woody plants over the time-frame of our study, but reduced their abundance and suppressed their growth, which would ostensibly prevent them from achieving dominance. Implications for extending the longevity of widely practiced ‘brush management’ grassland restoration treatments are discussed in the context of perceptions of prairie dogs as rangeland pests. Prairie dogs represent an enigma in keystone conservation. Whereas the reintroduction of large or charismatic keystone species (e.g. sea otters [Enhydra lutris]) are conducted to restore critical ecological function, reintroductions of other keystone species, such as gray wolves [Canis lupus] and in our case, prairie dogs, are highly controversial. Our findings suggest reintroductions of this negatively perceived small herbivore could function as a tool to locally suppress woody plant proliferation that is widely regarded as an impediment to livestock production. Accordingly, prairie dogs could promote restoration efforts to re-establish and maintain habitat for grassland endemics while promoting biological diversity and other ecosystem services.

Phosphorus addition regulates the responses of soil multifunctionality to nitrogen over-fertilization in a temperate grassland

Nitrogen (N) and phosphorus (P) are two major limiting factors in terrestrial ecosystems. Excessive N applications alter ecosystem functions by causing nutrient imbalances with P. Yet, little is known about why and how the balance between N and P regulates soil multifunctionality –the simultaneous provision of multiple soil functions–. We explored how P additions regulated the responses of soil multifunctionality to different levels of N fertilization (10, 20, 40 g N m−2 yr−1) using a mesocosm experiment in a temperate grassland in China. Nitrogen alone and P addition increased multifunctionality at rate of ≤10 and 20 g N m−2 yr−1, respectively. However, the magnitude of positive effects decreased with N additions over this level. P additions increased multifunctionality resistance to N at low rate of ≤10 g m−2 yr−1 compared to higher N levels. Soil N:P stoichiometry and plant diversity played dominant roles in regulating soil multifunctionality. We found that a balanced combination of N and P additions (20:10) can help maintain the highest multifunctionality in this temperate grassland. The results provide new insights that through P addition, we could better manage soil multifunctionality and increase its resistance to expected fertilization scenarios (≤ 10 g m−2 yr−1).

A Multi-Scale Approach to Predict the Fractional Cover of Medusahead (Taeniatherum Caput-Medusae)

Medusahead is an aggressive, winter annual that is of dire concern for the health and sustainability of western rangelands in the United States. Medusahead reduces plant diversity, alters ecosystem function, and reduces carrying capacities for both livestock and wildlife. The species has competitive advantages over cheatgrass and native grasses that causes an increased amount of fine fuels deposited on western rangelands. The Channeled Scablands of eastern Washington in the United States represent a typical example of a region being challenged by the expansion of this weed. The costs of the invasion are high and financial constraints can limit successful management. Managers need the ability to identify medusahead across entire landscapes, so they can work towards effective and efficient management approaches. Remote sensing offers the ability to measure vegetation cover at large spatial scales, which can lead to a better understanding of the invasive characteristics of problematic species like medusahead. For instance, research has been successful in creating large-scale distribution maps of cheatgrass over western rangelands. Many applications rely on the phenological characteristics of a target plant which can present problems in separating two species with similar phenologies (i.e. cheatgrass & medusahead). A medusahead-specific map gives managers the flexibility to prioritize and direct management needs when attempting to control the spread of medusahead into non-invaded areas. This study integrated GPS acquired field locations from three study sites (Sites S, C, & N) and imagery from two remote sensing platforms (1-m aerial imagery & 30-m Landsat), to model and predict fractional cover of medusahead over 37,000+ ha of rangelands in the Channeled Scabland region of eastern Washington. Using a multi-scaled approach, this research showed that regression tree algorithms can model the complex spectral response of senesced medusahead using late summer Landsat scenes. The predictive performances resulted in a R2 of 0.80 near the model's training site (Site S) and an average R2 of 0.68 away from the training site (Sites C & N). This research provides a non-phenological approach to produce accurate large-scale, distribution maps of medusahead which can aid land managers who are challenged by its invasion.

Drought promotes soil phosphorus transformation and reduces phosphorus bioavailability in a temperate forest

Drought can substantially alter ecosystem functions, especially biogeochemical cycles of key nutrients. As an essential but often limiting nutrient, P plays a central role in critical ecosystem processes (i.e. primary productivity). However, little is known about how drought can affect the soil phosphorus (P) cycle and its bioavailability in forest ecosystems. Here, we conducted a four-year field drought experiment using throughfall reduction approach to examine how drought can alter soil P dynamics and bioavailability in a warm temperate forest. We found that the P held in calcium phosphate was significantly decreased under drought, which was accompanied by the increases of inorganic and organic P bound with secondary minerals (Fe/Al oxides). These drought-induced P transformations can be well explained by the soil pH. The significant decline in soil pH under drought can drive the solubilization of P held in calcium phosphate. Our study further showed that drought directly decreased soil P bioavailability and altered the potential mechanisms of the replenishment of inorganic P into the soil solution. The potential of the inorganic P release driven by protons was reduced, while inorganic P release potentials driven by enzyme and organic acid were increased under drought. Therefore, our results strongly suggested that drought can significantly alter the soil P biogeochemical cycles and change the biological mechanisms underlying P bioavailability.

Foundation Species Loss Affects Leaf Breakdown and Aquatic Invertebrate Resource Use in Black Ash Wetlands

The invasion by emerald ash borer (Agrilus planipennis) of extensive black ash wetlands in the upper Great Lakes region of North America is expected to alter plant community structure and composition and, therefore, abiotic factors like temperature and hydrology. We conducted two experiments to examine how changes in leaf litter could alter ecosystem function via 1) changes in litter breakdown and 2) aquatic invertebrate feeding. For the first experiment, we placed litter bags containing black ash (Fraxinus nigra), swamp white oak (Quercus bicolor), and lake sedge (Carex lacustris), in either control or clear-cut black ash plots. We found that black ash litter broke down 2-3 times faster than other species and broke down faster in control plots than in clear-cuts. There was no effect of clear cutting on swamp white oak or lake sedge breakdown rates. For the second experiment, we fed shredding caddisfly larvae (Limnephilus indivisus) one of six species: black ash, swamp white oak, lake sedge, balsam poplar (Populus balsamifera), American elm (Ulmus americana), or speckled alder (Alnus incana) for 14 days. Caddisflies had the highest survival and greater resource use when given black ash or speckled alder, which are abundant in black ash wetlands. These results suggest that loss of black ash will alter ecosystem processes via changes in the physical environment, changes in leaf litter properties, and changes in shredder processing rates of leaf litter.

Cascading effects from plant to soil elucidate how the invasive Amorpha fruticosa L. impacts dry grasslands

AbstractQuestionsUnderstanding the mechanisms underlying the impacts of exotic plant invasions is a central issue in plant ecology. Considering the invasion process, any alteration of the nutrient cycle is of fundamental importance. We hypothesized that the woody N‐fixing invasive Amorpha fruticosa is indirectly depleting plant diversity by altering ecosystem functions of riverine grasslands, thus producing a conspicuous shift in species composition.LocationTemperate lowland riparian areas of northeast Italy.MethodsIn 12 sites, we selected uninvaded, partially invaded, and invaded grasslands (36 plots). In each plot, we performed a vegetation relevé, measured main A. fruticosa growth traits, light transmittance and soil features. We studied the effects of the invasion of A. fruticosa on grassland properties and plant diversity, examining the interactions between soil nutrient cycles, light availability and plant diversity.ResultsIncreased abundance of A. fruticosa affected main soil properties (i.e. increase in soil mineralization and nitrification) and light availability (i.e. decrease in light). The δ15N of soil organic matter was strongly related to A. fruticosa basal area, thus supporting the hypothesis of an increase in soil nitrogen (N) availability due to invasion by the N‐fixer. Plant taxonomical and functional diversity decreased significantly as A. fruticosa cover increased. Plant diversity was more related with N than light availability or soil organic carbon. Similarly, the shift in species composition (i.e. beta diversity) of invaded grasslands was related to increased soil nitrification rates.ConclusionsOur findings show how a nitrogen‐fixing invasive plant such as A. fruticosa may influence the main ecosystem properties, causing cascading effects on soil functions, decreasing plant diversity. Alteration of the N cycle represents the key process involved in this plant invasion, suggesting that further studies should focus on potential solutions to mitigate the soil N supply, curb the invasion and restore plant diversity of these riverine grasslands.

Food-web interactions in a coastal ecosystem influenced by upwelling and terrestrial runoff off North-West Spain

Ecopath with Ecosim has been used to create mass-balance models of different type of ecosystems around the world to explore and analyse their functioning and structure. This modelling framework has become a key tool in the ecosystem approach to fisheries management, by providing a more comprehensive and holistic understanding of the interactions between the different species. Additionally, Ecopath with Ecosim has provided a useful framework to study ecosystem maturity, changes in the ecosystem functioning over time and the impact of fisheries and aquaculture on the ecosystem, among other aspects. The present work explores the ecosystem functioning and structure in an anthropogenically impacted coastal area, influenced by seasonal coastal upwelling and high input of nutrients from rias (ancient drowned tectonic valleys) off North-West Spain. A mass-balance model with 23 functional groups was created using Ecopath to study the trophic interactions in the ecosystem during the post-upwelling period (August to October) in 2017. The model described an immature, wasp-waist ecosystem, that shared characteristics of ecosystems found in upwelling areas and ecosystems found in fjords or coastal embayments. Deeper analyses highlighted the importance of small planktivorous pelagic fish as a keystone functional group, and of zooplankton, blue whiting (Micromesistius poutassou) and phytoplankton as structuring groups in the ecosystem. Additionally, the study revealed that the existing fishing pressure on species of intermediate-high trophic levels could alter ecosystem functioning and structure, and ultimately affect top predators in the area. Findings of this study provide baseline information in ecosystem functioning and structure in the area and highlight the need to deeper study the effects of fisheries and their potential impacts on top predators.

Individual behavior drives ecosystem function and the impacts of harvest.

Current approaches for biodiversity conservation and management focus on sustaining high levels of diversity among species to maintain ecosystem function. We show that the diversity among individuals within a single population drives function at the ecosystem scale. Specifically, nutrient supply from individual fish differs from the population average >80% of the time, and accounting for this individual variation nearly doubles estimates of nutrients supplied to the ecosystem. We test how management (i.e., selective harvest regimes) can alter ecosystem function and find that strategies targeting more active individuals reduce nutrient supply to the ecosystem up to 69%, a greater effect than body size-selective or nonselective harvest. Findings show that movement behavior at the scale of the individual can have crucial repercussions for the functioning of an entire ecosystem, proving an important challenge to the species-centric definition of biodiversity if the conservation and management of ecosystem function is a primary goal.

Declines in native forb richness of an imperiled plant community across an anthropogenic nitrogen deposition gradient

AbstractAnthropogenic nitrogen (N) deposition is known to reduce plant diversity in ecosystems worldwide; however, effects on the diversity of Mediterranean‐type ecosystems—global hotspots of biodiversity—are relatively unexplored. In California, elevated N deposition due to air pollution has a multitude of ecological effects including the facilitation of nonnative plant invasion and altered ecosystem functioning, but impacts on plant richness have been inadequately quantified. We addressed this research gap by evaluating patterns of plant richness in coastal sage scrub (CSS), a severely threatened, highly diverse Mediterranean‐type shrubland, across the Santa Monica Mountains National Recreation Area. This is the largest urban national park in the United States and experiences a strong gradient of N deposition due to its proximity to urban Los Angeles. We measured soil N, plant cover, and richness at 30 CSS sites across this gradient and used regression analyses to explore relationships between richness, N deposition, and other environmental variables. We observed significant declines in plant richness across a steep gradient of soil N availability that paralleled patterns of N deposition, primarily due to decreases in native forb species. Our analyses identified soil N as the best predictor of patterns of native forb richness, but other factors, including nonnative plant cover and aridity, may also drive reduced richness. In addition to the marked decline in the number of native forb species, increasing N deposition was also associated with lower native shrub richness per area and increased cover of nonnatives. These results highlight the threat posed by N deposition to the conservation of this already imperiled ecosystem under continued environmental change.

Response of estuarine fish assemblages to an atypical climatic event in northeastern Brazil

Knowledge of the effects of environmental variables on estuaries with intermittent upstream rivers is scarce. Thus, understanding how environmental filters affect fish assemblages in these estuaries is important when an atypical drought occurs. Three zones in the Mamanguape River estuary designated according to the salinity gradient were sampled during an atypical climatic event in 2015. A total of 18,084 fishes of 125 species were recorded. Density and richness showed significant differences between seasons, while density, biomass, diversity and evenness showed significant differences in spatial pattern. By ecological guild, marine estuarine-dependent, solely estuarine, marine estuarine-opportunist and estuarine and marine were the most representative groups in the estuary during the sampling period. Chlorophyll a and salinity were major filters that explained only the spatial distribution of fish assemblages, relating mainly to richness increasing from the upper to the lower parts of the estuary. Our study supports the need to understand the filters for species richness and spatial distribution patterns. Changes in those filters may shift fish assemblages, hence altering ecosystem function.

Low-intensity monitoring of small-mammal habitat associations and species interactions in an urban forest-preserve network

Abstract ContextAnthropogenic landscape modification and fragmentation result in loss of species and can alter ecosystem function. Assessment of the ecological value of urban reserve networks requires baseline and continued monitoring. However, depending on the desired indicators and parameters, effective monitoring can involve extensive sampling that is often financially or logistically infeasible. AimsWe employed a low-intensity, mixed-detector survey design to monitor the small-mammal community across a network of 53 fragmented forest preserves (225 sites) in a highly urbanised landscape in the Chicago metropolitan area from August to October, 2009–2012. MethodsWe used a sequential process to fit single-season occupancy and pairwise co-occurrence models for six common small mammal species to evaluate habitat associations and interspecific interactions. Key resultsShrew species and meadow voles occurred more often in open canopy-associated habitats, whereas occupancy was greater for eastern chipmunks, grey squirrels and white-footed mice in closed-canopy habitats. Habitat associations were complicated by negative pairwise interactions, resulting in reduced occurrence of meadow voles when predatory short-tailed shrews were present and lower occupancy rates of white-footed mouse when chipmunk competitors where present. White-footed mice co-occurred with short-tailed shrews, but detection of white-footed mice was lower when either eastern chipmunks or short-tailed shrews were present, suggesting that densities of these species could be inversely related. ConclusionsWe found evidence for both habitat segregation and interspecific interactions among small mammal species, by using low-intensity sampling across the reserve network. Thus, our sampling and analysis approach allowed for adequate assessment of the habitat associations and species interactions within a small-mammal community. ImplicationsOur findings demonstrated the utility of this monitoring strategy and community as bioindicators for urban-reserve networks. The approach described holds promise for efficient monitoring of reserve networks in fragmented landscapes, critical as human population densities and urbanisation increase, and we discuss how adaptive sampling methods could be incorporated to further benefit conservation efforts.

Increasing temperatures, diversity loss and reorganization of deep-sea fish communities east of Greenland

In recent years, Arctic and sub-Arctic fish communities have shown extensive reorganization on shelves and in shallow waters, but little is known about the ecological impact of environmental changes in deeper waters. We examined temporal changes (1998-2016) in fish diversity and community structure based on research survey data from East Greenland, over a depth gradient spanning 400 to 1500 m. A northern and a southern continental slope region, 360 km apart, were analysed for temporal changes in water temperature and fish community structure. The bottom water temperature increased by up to 0.2 and 0.5°C, respectively. Contrary to expectations, there was a concomitant loss of species richness of up to 3 and 5 species, respectively, and a decrease in total abundance in both regions. Abundances of individual species displayed different trends between regions, with 3 species of wolf fishes (Anarhichas spp.) and American plaice Hippoglossoides platessoides decreasing in the north and blue antimora Antimora rostrata, Agassiz’ slickhead Alepocephalus agassizii and the roundnose grenadier Coryphaenoides rupestris decreasing in the south. The regional differences may reflect different oceanographic characteristics, as the northern region is more influenced by colder Arctic water, whereas the southern region is primarily influenced by the Subpolar Gyre (SPG). However, the observed temperature increase is expected to be due to an intensifying Atlantic Multidecadal Oscillation and/or anthropogenic climate change and not to SPG changes. The observed changes in biodiversity and community structure associated with warming are likely to affect community dynamics and alter ecosystem functioning.

Current and future biomass carbon uptake in Boston's urban forest

Ecosystem services provided by urban forests are increasingly included in municipal-level responses to climate change. However, the ecosystem functions that generate these services, such as biomass carbon (C) uptake, can differ substantially from nearby rural forest. In particular, the scaled effect of canopy spatial configuration on tree growth in cities is uncertain, as is the scope for medium-term policy intervention. This study integrates high spatial resolution data on tree canopy and biomass in the city of Boston, Massachusetts, with local measurements of tree growth rates to estimate the magnitude and distribution of annual biomass C uptake. We further project C uptake, biomass, and canopy cover change to 2040 under alternative policy scenarios affecting the planting and preservation of urban trees. Our analysis shows that 85% of tree canopy area was within 10 m of an edge, indicating essentially open growing conditions. Using growth models accounting for canopy edge effects and growth context, Boston's current biomass C uptake may be approximately double (median 10.9 GgC yr−1, 0.5 MgC ha−1 yr−1) the estimates based on rural forest growth, much of it occurring in high-density residential areas. Total annual C uptake to long-term biomass storage was equivalent to <1% of estimated annual fossil CO2 emissions for the city. In built-up areas, reducing mortality in larger trees resulted in the highest predicted increase in canopy cover (+25%) and biomass C stocks (236 GgC) by 2040, while planting trees in available road margins resulted in the greatest predicted annual C uptake (7.1 GgC yr−1). This study highlights the importance of accounting for the altered ecosystem structure and function in urban areas in evaluating ecosystem services. Effective municipal climate responses should consider the substantial fraction of total services performed by trees in developed areas, which may produce strong but localized atmospheric C sinks.

Effects of ciprofloxacin on metabolic activity and algal biomass of urban stream biofilms

Pharmaceuticals and personal care products (PPCPs), such as the commonly prescribed antibiotic ciprofloxacin, are present and persistent in freshwaters, yet their effects on aquatic ecosystem functions at environmentally-relevant concentrations are rarely explored. Stream biofilms provide multiple functions in stream ecosystems, but their functional response to PPCP contaminants such as ciprofloxacin is unclear. To establish the effect of ciprofloxacin on aquatic biofilms, we colonized biofilms in situ on tiles (n = 80) at four sites along an urban stream in Gainesville, Florida, including two sites above and two sites below a wastewater treatment plant (WWTP). We then incubated the tiles and associated biofilms in the laboratory for 6 d exposing biofilms to either 0, 0.01, 0.1, or 1.0 μg/L (target concentrations) of ciprofloxacin. At the end of the 6 d laboratory exposure, we quantified gross primary production (GPP), respiration (R), and biomass (as chlorophyll a) of biofilms, and calculated response ratios for each response. All response metrics were significantly differed across sites (p < 0.01). Ciprofloxacin significantly decreased GPP (p < 0.05) regardless of treatment concentration, most notably at the site immediately below the WWTP, where there was no measurable GPP on any ciprofloxacin-treated biofilms. In contrast, respiration (R) was not significantly affected by ciprofloxacin, despite an apparent increase in R at the WWTP site. However, the WWTP site R was significantly different from the most upstream and downstream sites (p < 0.001) but was not significantly different from a nearby site upstream of the WWTP (p > 0.05). These results indicate that chronic exposure to ciprofloxacin through WWTP effluent can alter ecosystem functions performed by biofilms, which can have consequences for higher trophic levels and stream processes. By quantifying biofilm metabolic responses to ciprofloxacin exposure, this study supports the concept that pharmaceuticals and personal care products can induce sub-lethal effects on ecological processes at environmentally-relevant concentrations.