scholarly journals Different drivers, common mechanism; the distribution of a reef fish is restricted by local-scale oxygen and temperature constraints on aerobic metabolism

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Murray I Duncan ◽  
Nicola C James ◽  
Warren M Potts ◽  
Amanda E Bates
Keyword(s):  
South African ◽  
Reef Fish ◽  
Regional Scale ◽  
Marine Organisms ◽  
Hypoxia Tolerance ◽  
Common Mechanism ◽  
Local Conservation ◽  
Management Decisions ◽  
Distribution Models ◽  
Temperature Range

Abstract The distributions of ectothermic marine organisms are limited to temperature ranges and oxygen conditions that support aerobic respiration, quantified within the metabolic index (ϕ) as the ratio of oxygen supply to metabolic oxygen demand. However, the utility of ϕ at local scales and across heterogenous environments is unknown; yet, these scales are often where actionable management decisions are made. Here, we test if ϕ can delimit the entire distribution of marine organisms when calibrated across an appropriate temperature range and at local scales (~10 km) using the endemic reef fish, Chrysoblephus laticeps, which is found in the highly heterogenous temperature and oxygen environment along the South African coastal zone, as a model species. In laboratory experiments, we find a bidirectional (at 12°C) hypoxia tolerance response across the temperature range tested (8 to 24°C), permitting a piecewise calibration of ϕ. We then project this calibrated ϕ model through temperature and oxygen data from a high spatial resolution (11 to 13 km) ocean model for the periods 2005 to 2009 and 2095 to 2099 to quantify various magnitudes of ϕ across space and time paired with complementary C. laticeps occurrence points. Using random forest species distribution models, we quantify a critical ϕ value of 2.78 below which C. laticeps cannot persist and predict current and future distributions of C. laticeps in line with already observed distribution shifts of other South African marine species. Overall, we find that C. laticeps’ distribution is limited by increasing temperatures towards its warm edge but by low oxygen availability towards its cool edge, which is captured within ϕ at fine scales and across heterogenous oxygen and temperature combinations. Our results support the application of ϕ for generating local- and regional-scale predictions of climate change effects on organisms that can inform local conservation management decisions.

Managing Alien Plants for Biodiversity Outcomes—the Need for Triage

2010 ◽  
Vol 3 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Paul O. Downey ◽  
Moira C. Williams ◽  
Leonie K. Whiffen ◽  
Bruce A. Auld ◽  
Mark A. Hamilton ◽  
...  
Keyword(s):  
Biodiversity Conservation ◽  
Native Species ◽  
Regional Scale ◽  
Management Strategies ◽  
Alien Plants ◽  
Plant Management ◽  
Policy Reforms ◽  
Management Decisions ◽  
Alien Plant ◽  
Triage System

AbstractRecognition that alien plants pose a significant threat to biodiversity has not always translated into effective management strategies, policy reforms, and systems to establish priorities. Thus, many alien plant management decisions for the protection of biodiversity occur with limited knowledge of what needs to be protected (other than biodiversity in a generalized sense) or the urgency of actions. To rectify this, we have developed a triage system that enables alien plant management decisions to be made based on (1) the urgency of control relative to the degree of threat posed to biodiversity, compared with (2) the likelihood of achieving a successful conservation outcome as a result of alien plant control. This triage system is underpinned by a two-step approach, which identifies the biodiversity at risk and assesses sites to determine priorities for control. This triage system was initially developed to manage the threat posed by bitou bush to native species in New South Wales (NSW), Australia. It has subsequently been improved with the national assessment of lantana in Australia, and the adaptation from a single to multiple alien plant species approach on a regional scale. This triage system identifies nine levels of priority for alien plant management aimed at biodiversity conservation, ranging from immediate, targeted action to limited or no action. The development of this approach has enabled long-term management priorities to be set for widespread alien plants that are unlikely to be eradicated. It also enables control to occur in a coordinated manner for biodiversity conservation at a landscape scale, rather than as a series of individual unconnected short-term actions.

scholarly journals Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: methodology

2015 ◽  
Vol 8 (2) ◽  
pp. 611-632 ◽  
Author(s):  
W. Su ◽  
J. Corbett ◽  
Z. Eitzen ◽  
L. Liang
Keyword(s):  
Angular Distribution ◽  
Sea Ice ◽  
Regional Scale ◽  
Radiant Energy ◽  
Energy System ◽  
Continuous Functions ◽  
Climate Feedback ◽  
Radiative Energy ◽  
Next Generation ◽  
Distribution Models

Abstract. The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance, radiative effects of clouds and aerosols, and climate feedback. The Clouds and the Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene-type-dependent angular distribution models (ADMs). This paper describes the next-generation ADMs that are developed for Terra and Aqua using all available CERES rotating azimuth plane radiance measurements. Coincident cloud and aerosol retrievals, and radiance measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from Goddard Earth Observing System (GEOS) data assimilation version 5.4.1 are used to define scene type. CERES radiance measurements are stratified by scene type and by other parameters that are important for determining the anisotropy of the given scene type. Anisotropic factors are then defined either for discrete intervals of relevant parameters or as a continuous functions of combined parameters, depending on the scene type. Significant differences between the ADMs described in this paper and the existing ADMs are over clear-sky scene types and polar scene types. Over clear ocean, we developed a set of shortwave (SW) ADMs that explicitly account for aerosols. Over clear land, the SW ADMs are developed for every 1° latitude × 1° longitude region for every calendar month using a kernel-based bidirectional reflectance model. Over clear Antarctic scenes, SW ADMs are developed by accounting the effects of sastrugi on anisotropy. Over sea ice, a sea-ice brightness index is used to classify the scene type. Under cloudy conditions over all surface types, the longwave (LW) and window (WN) ADMs are developed by combining surface and cloud-top temperature, surface and cloud emissivity, cloud fraction, and precipitable water. Compared to the existing ADMs, the new ADMs change the monthly mean instantaneous fluxes by up to 5 W m−2 on a regional scale of 1° latitude × 1° longitude, but the flux changes are less than 0.5 W m−2 on a global scale.

Regional-scale groundwater flow in a Canadian Shield setting

2009 ◽  
Vol 46 (7) ◽  
pp. 813-827 ◽  
Author(s):  
Jonathan F. Sykes ◽  
Stefano D. Normani ◽  
Mark R. Jensen ◽  
Edward A. Sudicky
Keyword(s):  
Groundwater Flow ◽  
Surface Topography ◽  
Regional Scale ◽  
Three Dimensional ◽  
Complex Surface ◽  
Crystalline Rock ◽  
Canadian Shield ◽  
Water Drainage ◽  
Distribution Models ◽  
Matrix Permeability

A three-dimensional numerical analysis of a 5734 km2 watershed situated in the Canadian Shield has been conducted to illustrate aspects of regional-scale groundwater flow in a crystalline rock setting. An essential requirement of the analysis is the preservation and accurate description of the complex topography, surface water drainage network, groundwater salinity distribution, and permeability distributions. The postglacial evolution of the groundwater flow system was investigated using the finite difference model SWIFT-III. Robustness was assessed by exploring the sensitivity of groundwater flow to topography, variable matrix permeability distribution models, pore-water salinity, and the dissipation of elevated initial pore pressures that result from ice that overlaid the watershed in the last glacial period. Groundwater flow analyses indicate that freshwater heads in all model layers are highly correlated with the complex surface topography such that the transition from zones of groundwater recharge to zones of discharge occurs over distances that can be relatively short. Shallow flow to a depth of tens of metres dominates the overall water balance, and the length of flow paths is relatively short. The analyses of this study indicate that the flow in deeper rock is not regional but rather is a subdued reflection of the local-scale surface topography.

scholarly journals Exceptionally high but still growing predatory reef fish biomass after 23 years of protection in a Marine Protected Area

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246335
Author(s):  
Irene Rojo ◽  
José Daniel Anadón ◽  
José Antonio García-Charton
Keyword(s):  
Reef Fish ◽  
Carrying Capacity ◽  
Fish Assemblages ◽  
Marine Protected Area ◽  
Regional Scale ◽  
Trophic Levels ◽  
Trophic Groups ◽  
Total Recovery ◽  
Entire Study

Marine Protected Areas (MPAs) help replenish fish assemblages, though different trophic levels may show diverse recovery patterns. Long-term protection is required to achieve total recovery but poaching events may prevent the achievement of full carrying capacity. Here, we have analysed the effect of long-term protection on the entire reef fish community and the different trophic levels in the Cabo de Palos-Islas Hormigas MPA (SE Spain; SW Mediterranean Sea) in order to assess their recovery patterns after 23 years of protection. We compared the values for carrying capacity obtained with the maximum values achieved at regional scale, and we assessed the effect of a reduction in the surveillance over a few years, during which poaching events increased, on the recovery patterns. We found that, overall, biomass of fishes increased with time while density diminished. In particular, piscivorous and macro-invertivore fish increased while the other trophic groups remained constant or declined, suggesting top-down processes. For the entire study period, those trophic groups were approaching carrying capacity; however, when accounting only for the period in which enforcement was high and constant, they grew exponentially, indicating that full carrying capacity may have not been achieved yet. When compared to other Mediterranean MPAs, the Cabo de Palos-Islas Hormigas MPA showed values for biomass that were disproportionately higher, suggesting that local factors, such as habitat structure and associated oceanographic processes, may be responsible for the dynamics found. Our results help to understand the potential trajectories of fish assemblages over a consolidated MPA and highlight empirically how the reduction of surveillance in a period may change the recovery patterns.

scholarly journals Co-occurrence variation explains the low host dependence of ambrosia beetles along altitude gradients in SW China

2021 ◽  
Author(s):  
Fang Luo ◽  
LINGZENG MENG ◽  
Jian Wang ◽  
Yan-Hong Liu
Keyword(s):  
Temporal Dynamics ◽  
Hierarchical Modeling ◽  
Species Turnover ◽  
Regional Scale ◽  
Biotic Interactions ◽  
Ambrosia Beetle ◽  
Minor Role ◽  
Climatic Gradient ◽  
Distribution Models ◽  
Ambrosia Beetles

Abstract Background Separation of biotic and abiotic impacts on species diversity distribution patterns across a significant climatic gradient is a challenge in the study of diversity maintenance mechanisms. The basic task is to reconcile scale-dependent effects of abiotic and biotic processes on species distribution models. However, Eltonian noise hypothesis predicted that the effects of biotic interactions will be averaged out at macroscales, and there are many empirical observations that biotic interactions would constrain species distributions at micro-ecological scales. Here, we used a hierarchical modeling method to detect the host specificities of ambrosia beetles (Scolytinae and Platypodinae) with their dependent tree communities across a steep climatic gradient, which was embedded within a relatively homogenous spatial niche. Results Species turnover of both trees and ambrosia beetles have a relatively similar pattern, characterized by the climatic proxy at a regional scale, but not at local scales. This pattern confirmed the Eltonian noise hypothesis wherein emphasis was on influences of macro-climate on local biotic interactions between trees and hosted ambrosia beetle communities, whereas local biotic relations, represented by host specificity dependence, were regionally conserved. Conclusions At a confined spatial scale, cross-taxa comparisons of co-occurrence highlighted the importance of the organism’s dispersal. The effects of tree abundance and phylogeny diversity on ambrosia beetle diversity were, to a large extent, indirect, operating via changes in ambrosia beetle abundance through spatial and temporal dynamics of resources distribution. Tree host dependence plays a minor role on the hosted ambrosia beetle community in this concealed wood decomposing interacting system.

scholarly journals New political economies of film distribution for South Africa’s townships? The ReaGilè concept

2017 ◽  
Author(s):  
Nyasha Mboti
Keyword(s):  
South African ◽  
Distribution Networks ◽  
Distribution Models ◽  
Film Distribution ◽  
Local Schools ◽  
Local Municipalities ◽  
The Disabled ◽  
Red Tape ◽  
Political Economies ◽  
Responsive Communication

ReaGilès are pre-fabricated, self-contained, education and entertainment complexes situated on 400m² sites at local schools or public open spaces consisting of a 60-seat cinema, 30- seat computer and Internet facility, community care and policing centre. These complexes are intended to service historically underserviced peri-urban black dormitory townships of South Africa and to help create jobs, especially amongst the youth, women and the disabled. The ReaGilè concept, on roll-out, has the potential to revolutionise exhibition and distribution in local film industries in ways mirroring the ground-breaking Nollywood straight-to-DVD model. The article discusses the potential of the ReaGilè concept to offer solutions to the twincrises of 1) representation stemming from existing film distribution networks that limit microbudget filmmakers, and 2) of government departments and local municipalities’ tendency towards dividing practices that objectivise the subject through frustrating development via delays, paperwork, never-ending meetings, fees, endless formalities and legalities, and red tape. The authors posit that ReaGilè has the potential to creatively disrupt and redesign formal distribution models and to fracture the narrow modernisation paradigm they deploy, replacing them with a responsive communication re/ordering and flexible distribution that restore subjectivity to the disenfranchised South African subject (the filmmaker and audience from the township).

Understanding the ecological niche to elucidate spatial strategies of the southernmost Tupinambis lizards

2013 ◽  
Vol 34 (4) ◽  
pp. 551-565 ◽  
Author(s):  
Sofía Lanfri ◽  
Valeria Di Cola ◽  
Sergio Naretto ◽  
Margarita Chiaraviglio ◽  
Gabriela Cardozo
Keyword(s):  
Species Distribution ◽  
Evolutionary Biology ◽  
Species Distribution Models ◽  
Regional Scale ◽  
Distribution Patterns ◽  
Niche Differentiation ◽  
Ecological Niches ◽  
Distribution Models ◽  
Interspecific Differences ◽  
Spatial Strategies

Understanding factors that shape ranges of species is central in evolutionary biology. Species distribution models have become important tools to test biogeographical, ecological and evolutionary hypotheses. Moreover, from an ecological and evolutionary perspective, these models help to elucidate the spatial strategies of species at a regional scale. We modelled species distributions of two phylogenetically, geographically and ecologically close Tupinambis species (Teiidae) that occupy the southernmost area of the genus distribution in South America. We hypothesized that similarities between these species might have induced spatial strategies at the species level, such as niche differentiation and divergence of distribution patterns at a regional scale. Using logistic regression and MaxEnt we obtained species distribution models that revealed interspecific differences in habitat requirements, such as environmental temperature, precipitation and altitude. Moreover, the models obtained suggest that although the ecological niches of Tupinambis merianae and T. rufescens are different, these species might co-occur in a large contact zone. We propose that niche plasticity could be the mechanism enabling their co-occurrence. Therefore, the approach used here allowed us to understand the spatial strategies of two Tupinambis lizards at a regional scale.

scholarly journals A coupled forage-grazer model predicts viability of livestock production and wildlife habitat at the regional scale

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Virginia A. Kowal ◽  
Sharon M. Jones ◽  
Felicia Keesing ◽  
Brian F. Allan ◽  
Jennifer M. Schieltz ◽  
...  
Keyword(s):  
Regional Scale ◽  
Stocking Density ◽  
Ecosystem Model ◽  
Livestock Production ◽  
Wildlife Habitat ◽  
Environmental Benefits ◽  
Production Model ◽  
Management Decisions ◽  
Livestock Management ◽  
Data Requirements

AbstractInformed management of livestock on rangelands underpins both the livelihoods of communities that depend on livestock for sustenance, and the conservation of wildlife that often depend on livestock-dominated landscapes for habitat. Understanding spatial patterns of rangeland productivity is therefore crucial to designing global development strategies that balance social and environmental benefits. Here we introduce a new rangeland production model that dynamically links the Century ecosystem model with a basic ruminant diet selection and physiology model. With lightweight input data requirements that can be met with global sources, the model estimates the viability of broad livestock management decisions, and suggests possible implications of these management decisions for grazing wildlife. Using minimal field data, the new rangeland production model enables the reliable estimation of cattle stocking density; this is an important predictor of the viability of livestock production and forage available for grazing wildlife.

scholarly journals Thermal tolerance and hypoxia tolerance are associated in blacktip reef shark (Carcharhinus melanopterus) neonates

2020 ◽  
Vol 223 (14) ◽  
pp. jeb221937
Author(s):  
Ian A. Bouyoucos ◽  
Phillip R. Morrison ◽  
Ornella C. Weideli ◽  
Eva Jacquesson ◽  
Serge Planes ◽  
...  
Keyword(s):  
Thermal Tolerance ◽  
Hypoxia Tolerance ◽  
Common Mechanism ◽  
Acclimation Temperature ◽  
Ph Effects ◽  
Thermal Dependence ◽  
Post Exercise ◽  
Reef Shark ◽  
Physiological Performance ◽  
Carcharhinus Melanopterus

ABSTRACTThermal dependence of growth and metabolism can influence thermal preference and tolerance in marine ectotherms, including threatened and data-deficient species. Here, we quantified the thermal dependence of physiological performance in neonates of a tropical shark species (blacktip reef shark, Carcharhinus melanopterus) from shallow, nearshore habitats. We measured minimum and maximum oxygen uptake rates (ṀO2), calculated aerobic scope, excess post-exercise oxygen consumption and recovery from exercise, and measured critical thermal maxima (CTmax), thermal safety margins, hypoxia tolerance, specific growth rates, body condition and food conversion efficiencies at two ecologically relevant acclimation temperatures (28 and 31°C). Owing to high post-exercise mortality, a third acclimation temperature (33°C) was not investigated further. Acclimation temperature did not affect ṀO2 or growth, but CTmax and hypoxia tolerance were greatest at 31°C and positively associated. We also quantified in vitro temperature (25, 30 and 35°C) and pH effects on haemoglobin–oxygen (Hb–O2) affinity of wild-caught, non-acclimated sharks. As expected, Hb–O2 affinity decreased with increasing temperatures, but pH effects observed at 30°C were absent at 25 and 35°C. Finally, we logged body temperatures of free-ranging sharks and determined that C. melanopterus neonates avoided 31°C in situ. We conclude that C. melanopterus neonates demonstrate minimal thermal dependence of whole-organism physiological performance across a seasonal temperature range and may use behaviour to avoid unfavourable environmental temperatures. The association between thermal tolerance and hypoxia tolerance suggests a common mechanism warranting further investigation. Future research should explore the consequences of ocean warming, especially in nearshore, tropical species.

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