Spatial Subsidies Research Articles

Unraveling the multiple facilitative effects of consumers on marine primary producers.

The loss of consumers threatens the integrity of ecological systems, but the mechanisms underlying the effects on communities and ecosystems remain difficult to predict. This is, in part, due to the complex roles that consumers play in those systems. Here, we highlight this complexity by quantifying two mechanisms by which molluscan grazers-typically thought of as consumers of their algal resources-facilitate algae on rocky shores. Initial observations in high-zone tide pools revealed that both water-column ammonium concentrations and photosynthetic biomass were higher in pools containing higher densities of grazers, suggesting that local-scale nutrient recycling by the grazers could be enhancing algal biomass. We assessed this possibility by experimentally manipulating grazer abundances at the level of whole tide pools but controlling access of those grazers to experimental plots within each pool. Contrary to predictions that algal biomass inside grazer exclusions would increase as grazer abundances in the pools increased, we found that algal biomass inside grazer-exclusion fences was unaffected by grazer abundances. Instead, the consumptive effects of grazers that were evident at low grazer abundances transitioned to facilitative effects as experimentally manipulated grazer abundances increased. This finding suggested that these positive interactions were associated with the physical presence of grazers and not just grazers' effects on nutrient availability. Subsequent experiments highlighted the potential role of "slime"-the pedal mucous trails left behind as the mollusks crawl on the substratum-in promoting the recruitment of algae and thereby mediating a spatial subsidy of new organic matter into the system. Furthermore, different grazer groups contributed disproportionately to ammonium excretion (i.e., turban snails) versus slime production (i.e., littorine snails), suggesting a potential role for grazer diversity. Our work highlights the complex ways in which consumers affect their resources, including multiple, complementary mechanisms by which these grazers facilitate the algae they consume.

Incorporation of the 15N-labeled simulated arthropod rain in the soil food web.

Direct trophic links between aboveground and belowground animal communities are rarely considered in food web models. Most invertebrate animals inhabiting aboveground space eventually become prey of soil predators and scavengers forming a gravity-driven spatial subsidy to detrital food webs, but its importance remains unquantified. We used laboratory-grown 15N-labeled Collembola to trace the incorporation of arthropod rain into soil food webs. Live or euthanized Collembola were supplemented once to field mesocosms in the amount equivalent to the mean daily input of the arthropod rain (19mg d.w. m-2). After the addition of live Collembola, the isotopic label was found most often in predatory Trombidiformes (83% of samples) and Mesostigmata mites (85%), followed by Araneae (58%), Chilopoda (45%), and Coleoptera (29%). Among non-predatory groups, the isotopic label was recorded in Thysanoptera (27%), Collembola (24%), and Oribatida (18%). The 15N-label was also detected in Symphyla, Formicidae, Diplura, Diplopoda, Opiliones, Diptera, Hemiptera, Oligochaeta, and Nematoda. There was a positive correlation between natural 15N abundance and the frequency of the isotopic label among predators, but not among decomposers. In the non-replicated treatment, in which dead collembolans were added, the label was found in predators and decomposers in approximately equal proportions (21-25%). Unlike other forms of the aboveground subsidy (such as leaflitter, frass, or honeydew) that are primarily processed by microorganisms, arthropod rain is assimilated directly by the animals. The high frequency of consumption of the aboveground subsidy suggests that it plays a significant role in maintaining the abundance of soil predators.

Relationship between salmon egg subsidy and the distribution of an avian predator.

As a spatial subsidy, which is the phenomenon of transferring resources from a donor system to a recipient system, anadromous salmonids contribute to the supply of marine-derived nutrients to freshwater and terrestrial systems. Live salmon and salmon carcasses and eggs are utilized by various organisms and affect their abundance and distribution. However, the evaluation of the effect of salmon subsidies on the abundance and distribution of terrestrial animals is biased toward predators or scavengers that utilize spawning adults and carcasses, and few studies have focused on the effect of salmon eggs as a subsidy. To avoid underestimating the function of salmon subsidies, the response to the availability of salmon eggs in various systems should be investigated. Here, we investigated the abundance and feeding behavior of the brown dipper Cinclus pallasii, as a consumer of salmon eggs, based on the hypothesis that the availability of salmon eggs affects the diet composition and stream distribution of this small predator. In addition, to test whether changes in the abundance of brown dippers are determined by salmon spawning, their abundance was compared upstream and downstream of the check dams in three streams during the peak spawning period. Brown dippers used salmon eggs during the spawning season (53.7% of diet composition), and their abundance increased as the number of spawning redds increased. In contrast, this pattern was not observed upstream of the check dam. These results suggested that the abundance and stream distribution of brown dippers vary according to the variation in the spatiotemporal availability of salmon eggs.

Leaving more than footprints: Anthropogenic nutrient subsidies to a protected area

AbstractMobile animals that traverse ecosystem boundaries can fundamentally reshape environments by providing critical nutrient and energy inputs to the ecosystems they inhabit. In particular, aggregations of seabirds often transform coastal and island ecosystems through large amounts of nutrient‐rich guano deposition. Anthropogenically driven losses of these subsidies can occur through changes in abundance of mobile species, including seabirds, and have been shown to drive whole‐scale ecosystem state change on islands. However, even though many species that forage on anthropogenic food sources are highly mobile and may thus play important roles in moving nutrients from urban systems to otherwise conserved ecosystems, the impacts of anthropogenic supplements on spatial subsidies have been largely ignored. Here we examine the effects of large nesting colonies of Western Gulls (Larus occidentalis), a generalist carnivore known to forage on human refuse, on the Channel Islands of California. Specifically, we explore how their foraging on human subsidies may change nutrient deposition patterns at their relatively remote and protected breeding islands. We equipped gulls with GPS loggers to assess the frequency of urban foraging, and we partnered this tracking data with bird density data to estimate the rate of wild and urban‐derived guano deposition on two different islands. Consistent with research on other gull species, we found high (up to 40%) but island‐specific rates of urban foraging, resulting between 66 and 93 kg ha−1 of guano in these two sites during the breeding season, a level greater than half the amount of fertilizer applied annually in typical commercial agricultural settings and likely the primary source of nitrogen and phosphorus inputs to this system. Specifically, we estimate that 27 kg ha−1 year−1 of nutrient‐rich guano is shuttled to these otherwise isolated islands from anthropogenic sources. This research highlights the large shadow (i.e., footprint) that human activity can cast on even remote ecosystems by driving significant nutrient enrichment through impacts on animal behavior and connectivity.

Metabolic rates in the squareback marsh crab Armases cinereum.

Metabolic rate is a basic individual metric that extends beyond the individual to link the ecology of populations, communities, and ecosystems via its role as a central component of energy budgets. Metabolic rates are often measured indirectly by quantifying respiration under simplified, standard laboratory conditions. This approach limits the application of these measurements to a small range of conditions that commonly do not reflect natural field conditions. We measured metabolic rates of the squareback marsh crab Armases cinereum under field conditions. Previous work highlights that movement of individual A. cinereum, especially females, provides a potential spatial subsidy of energy, as individuals consume foods in salt marshes and then transfer the resulting energy to upland forest ecosystems. We show that metabolic rate increases with size for both males and females and that metabolic rates are influenced by temperature and by whether females are vitellogenic. The metabolic rates that we measured more closely approximate field metabolic rates than standard metabolic rates and demonstrate that individual crabs experience high energy expenditures, reducing the amount of energy that may be transferred as a subsidy between marsh and forest as a result of the daily movements of individual crabs. Our measurements are therefore also a key component for the construction of an energy budget for this species.

Using ecosystem services to identify inequitable outcomes in migratory species conservation

AbstractBiodiversity conservation efforts have been criticized for generating inequitable socio‐economic outcomes. These equity challenges are largely analyzed as place‐based problems affecting local communities directly impacted by conservation programs. The conservation of migratory species extends this problem geographically since people in one place may benefit while those in another bear the costs of conservation. The spatial subsidies approach offers an effective tool for analyzing such relationships between places connected by migratory species. Designed to quantify ecosystem services provided and received in specific locations across a migratory species’ range—and the disparities between them—the spatial subsidies approach highlights three axes of inequity: between indigenous and settler colonial societies, between urban and rural populations, and between the Global North and Global South. Recognizing these relationships is critical to achieving two mutually reinforcing policy goals: avoiding inequitable conservation outcomes in efforts to conserve migratory species, and ensuring effective long‐term conservation of migratory species. In demonstrating how the spatial subsidies approach enables the identification and quantification of inequities involving three migratory species (northern pintail ducks, monarch butterflies, and Mexican free‐tailed bats), we argue that a spatial subsidies approach could apply to migratory species conservation efforts worldwide under the context of “payments for ecosystem services.”

The role of inputs of marine wrack and carrion in sandy-beach ecosystems: a global review.

Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross-ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed 'wrack', on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source ('carrion') for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy-beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land- and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy-beach ecosystems, where microbial decomposers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach-cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi-aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach-cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly mobile scavengers (e.g. foxes, coyotes, raptors, vultures). These consumers become important vectors in transferring marine productivity inland, thereby linking marine and terrestrial ecosystems. Whilst deposits of organic matter on sandy-beach ecosystems underpin a range of ecosystem functions and services, they can be at variance with aesthetic perceptions resulting in widespread activities, such as 'beach cleaning and grooming'. This practice diminishes the energetic base of food webs, intertidal fauna, and biodiversity. Global declines in seagrass beds and kelp forests (linked to global warming) are predicted to cause substantial reductions in the amounts of marine organic matter reaching many beach ecosystems, likely causing flow-on effects for food webs and biodiversity. Similarly, future sea-level rise and increased storm frequency are likely to alter profoundly the physical attributes of beaches, which in turn can change the rates at which beaches retain and process the influxes of wrack and animal carcasses. Conservation of the multi-faceted ecosystem services that sandy beaches provide will increasingly need to encompass a greater societal appreciation and the safeguarding of ecological functions reliant on beach-cast organic matter on innumerable ocean shores worldwide.

Diel Behaviors of Zooplankton Interact with Tidal Patterns to Drive Spatial Subsidies in the Northern San Francisco Estuary

Diel Behaviors of Zooplankton Interact with Tidal Patterns to Drive Spatial Subsidies in the Northern San Francisco Estuary

Spatial subsidies drive sweet spots of tropical marine biomass production.

Spatial subsidies increase local productivity and boost consumer abundance beyond the limits imposed by local resources. In marine ecosystems, deeper water and open ocean subsidies promote animal aggregations and enhance biomass that is critical for human harvesting. However, the scale of this phenomenon in tropical marine systems remains unknown. Here, we integrate a detailed assessment of biomass production in 3 key locations, spanning a major biodiversity and abundance gradient, with an ocean-scale dataset of fish counts to predict the extent and magnitude of plankton subsidies to fishes on coral reefs. We show that planktivorous fish-mediated spatial subsidies are widespread across the Indian and Pacific oceans and drive local spikes in biomass production that can lead to extreme productivity, up to 30 kg ha-1 day-1. Plankton subsidies form the basis of productivity "sweet spots" where planktivores provide more than 50% of the total fish production, more than all other trophic groups combined. These sweet spots operate at regional, site, and smaller local scales. By harvesting oceanic productivity, planktivores bypass spatial constraints imposed by local primary productivity, creating "oases" of tropical fish biomass that are accessible to humans.

Data for 'Spatial subsidies drive sweet spots of tropical marine biomass production'

Data for 'Spatial subsidies drive sweet spots of tropical marine biomass production'

Kelp-Associated Microbes Facilitate Spatial Subsidy in a Detrital-Based Food Web in a Shoreline Ecosystem

Microbes are ubiquitous but our knowledge of their effects on consumers is limited in benthic marine systems. Shorelines often form hotspots of microbial and detritivore activity due to the large amounts of detrital macrophytes that are exported from other coastal ecosystems, such as kelp forests, and accumulate in these systems. Shoreline ecosystems therefore provide a useful model system to examine microbial-detritivore interactions. We experimentally test whether bacteria in the biofilm of kelp provide a bottom-up influence on growth and reproductive output of detritivores in shorelines where detrital kelp accumulates, by manipulating the bacterial abundances on kelp (Ecklonia radiata). The growth rates for both male and female amphipods (Allorchestes compressa) were greater in treatments containing bacteria than those in which bacteria were reduced through antibiotic treatment, and this effect was greater for males offered aged kelp. The proportions of ovigerous females were greater when reared on kelp with intact bacteria, indicating a more rapid reproductive development in the presence of more bacteria. Bacterial abundance had little to no influence on nutrient content and palatability of kelp, based on tissue toughness, nitrogen and carbon content and C:N ratio. Thus, the most likely pathway for a microbial effect on detritivores was through feeding on kelp-associated bacteria. Regardless of the pathway, kelp-associated microbes have a strong influence on the fitness of a highly abundant detritivore that feeds preferentially on E. radiata in shoreline systems, and therefore form a hidden trophic step in this “brown” food web and a hotspot of secondary production.

Vegetation structure modulates ecosystem and community responses to spatial subsidies

AbstractEcosystem responses to external inputs of nutrients and organisms are highly variable. Theory predicts that ecosystem traits will determine the responses to spatial subsidies, but evidence for how vegetation structure can modulate those effects is lacking. We investigated how vegetation structure (i.e., leaf area index [LAI] and vegetation height) influenced the ecosystem and community responses to insect spatial subsidies in a subarctic grassland. Our experiment consisted of a 2 × 2 manipulation where in one treatment we either blocked flying insects over a 2‐yr period in 1‐m2 plots near the shore of Lake Mývatn, Iceland, where deposition of aquatic adult midges (Diptera: Chironomidae) to land is high, or left control plots accessible to flying midges. In the second treatment, grassland vegetation was cut (tall vs. short) at the start of each season and then allowed to regrow. We then measured litter decomposition and arthropod composition and density within each plot (n = 6 replicates × 4 treatments). Midge‐exclusion cages reduced midge deposition by 81% relative to the open plots. Vegetation cutting initially reduced LAI and vegetation height by 3× and 1.5×, respectively, but these were not different by the end of the second‐growing season. We found that vegetation structure modulated the effects of midge subsides on litter decomposition, with taller canopies intercepting more insect subsidies than shorter ones, leading to 18% faster litter decomposition. In contrast, the short‐vegetation plots intercepted fewer subsidies and had higher temperatures and sunlight, resulting in no effects of midges on decomposition. However, by the end of the experiment when all vegetation structure characteristics had converged across all plots, we found no differences in decomposition between treatments. The effects of midge subsidies on arthropod composition depended on the vegetation structure, suggesting that arthropods might also be responding to the structural effects on spatial subsidies. Our findings indicate that vegetation structure can modify the abiotic environment and the quantity of subsidies entering a recipient ecosystem as aerial insects, resulting in ecosystem‐ and community‐level responses. Thus, changing vegetation structure via habitat disturbances will likely have important implications for ecosystem functions that rely on spatial subsidies.

Pathways to Spatial Subsidies by Kelp in Seagrass Meadows

Spatial subsidies often occur from highly productive donor ecosystems to recipient systems with low productivity, but little is known about subsidies between highly productive ecosystems. Here, we investigated whether the kelp Ecklonia radiata, which is frequently dislodged from reefs, provides spatial subsidies in adjacent seagrass meadow where in situ productivity is already high. We clarified the pathways of the allochthonous kelp as a spatial subsidy by adding 15N-enriched kelp to Posidonia sinuosa seagrass meadows, tracing the uptake of kelp-derived nitrogen by seagrass epiphytes and epifauna. We observed a 32.5–52.2% loss of kelp biomass (wet weight), representing almost 13,000 μg of 15N from the labelled kelp. This corresponded with an increase in δ15N and 15N biomass of detritivores and epiphytes, showing either a direct or indirect (via epiphytes) assimilation of kelp-derived nutrients. The densities and biomass of the gastropod Strigosella lepidus and shrimps were higher in seagrass plots with input of E. radiata, but not for amphipods or the biomass of epiphytes. We estimate that the detritivores and epiphytes in the seagrass plots assimilated about 3% of the 15N released from the labelled kelp, and based on a data from previous study, the seagrass itself could have assimilated up to a further 6% of the released kelp 15N. Our findings show that in a highly productive seagrass ecosystem, where autochthonous food sources are available, the input of allochthonous resources such as kelp can supplement those resources and appears to play an important a role as a vector for a spatial subsidy.

Simulating the relative effects of movement and sociality on the distribution of animal-transported subsidies

Animal sociality (i.e., conspecific attraction or avoidance) can influence how animals move (i.e., sinuous to straight) across landscapes. Active subsidies are animal-transported resources (e.g., nutrients, detritus, prey) or consumers (e.g., predators, parasites, pathogens) across ecosystem boundaries and can affect ecosystem function. Animal movement has been shown to affect the spatial distributions of active subsidies. However, there is limited research on how conspecific interaction affects active subsidy distributions through animal movement. Based on dispersal from a donor to recipient ecosystem, we constructed a spatially explicit individual-based model (IBM) to quantify the effect of variation in conspecific interaction in three scenarios (attraction, avoidance, no interaction) and movement behavior as a correlated random walk on living and dead subsidy displacement, density, and clustering. In each conspecific interaction scenario, we examined emergent subsidy distributions from varying the straightness of movement path and the settlement probability as a function of settled conspecifics within dispersers’ perceptual range. Movement behavior predicted subsidy displacement, and conspecific interaction determined subsidy density and clustering patterns. We found that avoidance spread subsidies farther and at lower densities in the recipient ecosystem, generating more spread-out dead subsidy clusters. Attraction resulted in fewer, smaller, and denser living subsidy clusters closer to the ecosystem boundary. Higher settlement probability constrained living subsidy displacement with increased subsidy density and clustering across conspecific interaction scenarios. Subsidy density and clustering increased with perceptual range in attraction scenarios, limiting subsidy displacement. Subsidy displacement increased with perceptual range in avoidance scenarios, reducing subsidy density and clustering. This work is the first systematic simulation study on the influence of animal movement interactions with sociality on spatial subsidies across a broad parameter space. Our work provides context for empirical studies of active subsidy distribution and impact for a variety of taxa and ecosystems.

An improved spatial subsidy approach for ecological compensation in coastal seascapes for resilient land-sea management

Human activities are considered a critical impact factor for decision-making in coupled human-nature systems, such as conservation of coastal systems. Identifying key human activities that cause significant habitat degradation for coastal species remains challenging. We improved the spatial subsidy approach to identify and prioritize control strategies for human-caused distribution shifts of marine species. We applied this method to a threatened Indo-Pacific humpback dolphin (Sousa chinensis) in Xiamen Bay, China. Our results indicate that (1) a significant distribution shift for humpback dolphins from existing nature reserves to peripheral waters occurred from 2011 to 2014; (2) coastal tourism and industrial and urban construction had more significant negative impacts on humpback dolphins than maritime transportation and reclamation; and (3) proactive management should be implemented for maritime transportation and reclamation, while reactive management should be implemented for coastal tourism and industrial and urban construction. Human impact analysis, combined with spatially explicit modeling, contributes to determining the spatial alternatives for conservation planning. In response to possible ecological damage caused by human activities, the improved spatial subsidy results help provide knowledge and platforms for ecological compensation.

Role of saltmarsh production in subsidizing adjacent seagrass food webs: Implications for landscape-scale restoration

Restoration is an increasingly employed method for rehabilitating and enhancing the ecosystem services of lost or degraded coastal habitats, such as supporting high faunal densities and biomass. In certain ecosystems, faunal densities along habitat ecotones are greater than the densities observed in either adjoining habitat, potentially due to the provision of spatial subsidies (e.g., increased food availability). We tested the hypothesis that seagrass-associated consumers immediately adjacent to a saltmarsh are the recipients of food subsidies sourced from saltmarsh primary production. The food web biomarkers we used to evaluate spatial flows of energy across estuarine habitat boundaries included the stable isotope ratios of carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S). We collected primary producers (N = 102) including macrophytic vegetation, benthic microalgae, and epiphytes, as well as 11 key consumers (N = 190) across seagrass meadows either immediately adjacent to (N = 8) or isolated from (N = 8) saltmarsh. We also estimated particulate organic matter (POM) from filter-feeding bivalves and used literature values as proxies for detritus. These food-web biomarkers reveal that seagrass-associated consumers derived 20–23% of basal primary production from the saltmarsh, regardless of saltmarsh proximity. Seagrass sources (epiphytes and vegetation) as well as POM, likely were the dominant contributors for these consumers. This finding indicates that other mechanisms (i.e., refuge provision) might be the primary driver resulting in increased nekton density within seagrass along seagrass-saltmarsh ecotones. While a synergistic restoration of saltmarsh and seagrass habitat may have a positive effect on faunal biomass, it appears there may not be a primary food subsidy benefit to seagrass-associated consumers.

Complementarity in spatial subsidies of carbon associated with resource partitioning along multiple niche axes

The co-occurrence of several species, all of which share similar resource requirements, remains a paradox in ecology. Here, I evaluated resource use along multiple environmental axes to understand the potential for niche partitioning and complementarity in a guild of suspension-feeding rocky shore invertebrates. I focused on the mussels Perna canaliculus, Mytilus galloprovincialis, Aulacomya maoriana, and Xenostrobus pulex, all of which coexist along the coastline of the South Island of New Zealand. I quantified the mussels' distributions, both vertically on the shore and within the three-dimensional mussel bed matrix, and used carbon (δ13C) and nitrogen (δ15N) stable isotope ratios to compare species' diets. Mussels exhibited niche partitioning along all resource axes. Given the mussels' use of different spatial and food resources, I evaluated the potential for complementarity with respect to mussels' roles as mediators of an important spatial subsidy, carbon inputs from the nearshore ocean into rocky-shore ecosystems. In these systems, mussels are basal species, capturing and consuming particulate organic matter in the ocean and making it available for local consumption within the benthic community. I found that mussel diversity matters; even the most productive species-Perna canaliculus-only contributed about half of the mussel-mediated carbon that accumulated over a year. Multiple co-occurring species are, therefore, likely to provide more carbon at the base of the intertidal food web than any one species living independently, and complementarity in resource use along multiple environmental axes is likely an important mechanism underlying this relationship.

Shellfish subsidies along the Pacific coast of North America

Spatial subsidies are associated with pronounced ecosystem responses, as nutrients cross ecological boundaries and cascade through food webs. While the importance of subsidies is known, the role of shellfish, specifically molluscs, as a marine subsidy has not been formally described. Focusing primarily on the Pacific coast of North America, we identify vectors that transport shellfish‐derived nutrients into coastal terrestrial environments, including birds, mammals, and over 13 000 yr of marine resource use by people. Evidence from recipient ecosystems suggests shellfish drastically influence soil chemistry, forest productivity and the diversity of primary producers at the regional and landscape level. Responses in higher trophic levels have not yet been investigated, but given documented responses in lower trophic levels, this may be due to a lack of examination. To determine if the processes we describe within the northeast Pacific are pertinent to coastal environments worldwide, we also explore shellfish subsidies globally, with a specific focus on temperate and tropical islands. As shellfish are not as spatially or temporally constrained as other subsidies, our examination suggests our findings are applicable to many other geographical regions along the marine–terrestrial interface.

Dietary Patterns in Black Abalone Haliotis cracherodii Leach, 1814 as Indicated by Observation of Drift Algal and Seagrass Capture at San Nicolas Island, California, USA, 1982 to 2019

Black abalone Haliotis cracherodii Leach, 1814 are known to feed on drift plant macrodetritus moved about in the intertidal zone by waves and currents. Drift capture is a trait shared by at least several other abalone species. Drift materials are entrapped beneath the anterior foot and held for ingestion. The quantitative significance of feeding on entrapped drift macrodetritus for black abalone is unknown. Furthermore, there are no published data on the extent to which local and mesoscale spatial distributions of source plant populations influence the composition of drift plant material in black abalone diet as acquired by entrapment. From February 1982 through March 2019, occurrences of macrodetrital entrapment by black abalone were observed in nine rocky intertidal study plots, with a summed surface area of 2,054 m2, on the periphery of San Nicolas Island (SNI), California (Island centroid at ∼33.25°, –119.50°). A small preliminary survey and 27 complete surveys were performed during the study period (mean of ∼1.4 y between complete surveys). During the study, more than 1.5 × 105 black abalone were examined. The total likely included repeated observations of many individuals as a result of the known longevity and limited mobility of the species. Of those observed, ∼1.65 × 103 black abalone were recorded as apparently ingesting entrapped items. Frequency data were dominated (∼95% of all records) by three species of kelp Macrocystis pyrifera (Linnaeus) C. Agardh; commonly known as “giant kelp”, Egregia menziesii (Turner), and Eisenia arborea Areschoug. Of those, giant kelp was the most frequently observed entrapped category (∼76%). Living, attached giant kelp is rarely observed in intertidal habitats at SNI, and it follows that utilization of giant kelp by black abalone requires physical importation of the kelp from other locations. Frequencies of occurrence of giant kelp entrapment by individual study site were clearly associated with the relative surface canopy sizes and persistence patterns of offshore kelp forests adjacent (≤2 km) to the respective study sites. The pattern suggests that subsidies of drift giant kelp to black abalone diet involve mesoscale physical processes largely proximate to SNI but probably not subsidies from more distant locations such as other islands or the California mainland. Utilization of other frequently recorded kelps as food by black abalone likely involves spatial subsidies as well, but on smaller scales of distance (∼10–100 m for E. arborea; ∼0–100 m for E. menziesii). In the context of the imperiled status of black abalone, recovery actions may include outplants of captive-reared animals or transplantation of wild animals from other populations. For such actions, data from SNI suggest a need for consideration of scales of separation among release locations and nearby populations of the three apparently predominant kelp species in black abalone diet.

基于选择容量价值的生态补偿标准与自然资源资产价值核算——以珠江水资源供应为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于选择容量价值的生态补偿标准与自然资源资产价值核算——以珠江水资源供应为例 DOI: 10.5846/stxb201903230549 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: Quantifying the payments for ecosystem services and the value of natural resources based on the indicator of optional capacity value: a case study on water resources supply in Zhujiang River Basin, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选择容量价值是指，一项人类生存生产所必需的生态系统服务，其总量为消费该生态系统服务的消费活动所提供的选择自由度（即选择容量，optional capacity）与该消费活动所产生的经济社会价值的乘积。选择容量价值将经济发展状况和资源环境状况融合了起来，实现了经济社会发展与生态环境保护的价值统一，这对于推进保护与发展相辅相成的生态文明建设具有积极意义。为了探索以选择容量价值为指标的生态补偿标准与自然资源资产价值核算框架和核算方法，以珠江流域水资源供应为例，对跨水文单元的水资源供应流动进行了生态补偿核算，对各水文单元的水资源供应的自然资源资产价值进行了量化评估研究。研究结果显示，珠江三角洲地区的水资源供应的选择容量价值大部分（约74%）来自上游水文单元的跨区输入，而上游水文单元所提供的水资源供应的选择容量价值也在相当程度上依赖于下游水文单元的经济社会发展。基于跨区流动的水资源供应的选择容量价值，可以按照"共享共担"和"同工同酬"原则进行跨区生态补偿核算；基于各水文单元所提供的水资源供应的选择容量价值，可以对各单元内自然资源资产价值进行核定，这对于协调区域发展推进西江-珠江经济带流域生态文明建设具有重要意义。 Abstract:The ecosystem services (ES) optional capacity value (OCV) indicates the optional capacity of supporting the total value produced by human being's economic and social activities (TVPH) provided by the total volume of an ES which is indispensable to human survival. The OCV is described by the product of multiplying the TVPH by the optional capacity. The optional capacity is defined by the freedom of choosing the ES consumption from total ES volume, which is indicated by the average uncertainty of choosing the ES consumption from its total volume. The average uncertainty is described by log base 2, which indicates the uncertainty in a binary decision and is measured in bits. As combining the socio-economic index (i.e. TVPH) and the ES indexes (i.e. total ES volume and ES consumption), the OCV indicates the socio-economic conditions and the ES conditions at the same time. As the OCV describes the complementarity of development and protection, the usage of OCV in ES management will promote the endeavor for ecological civilization. However, how to introduce the OCV into management practice is still unclear. Especially, the method of how to introduce OCV into the frameworks and methods of quantifying the payments for ecosystem services (PES) and the value of natural resources (VNR) is needed to study urgently. To explore the frameworks and methods of quantifying the PES and the VNR based on the indicator of OCV, we analyzed the OCV of water resources supply in Zhujiang River Basin, China. Then, the PES between hydrologic units was discussed based on the OCV of ES spatial subsidies. The value of water resources in each hydrologic unit was quantified using the OCV of water resources supply. The results showed that the OCV of water resources supply of the hydrologic unit was supplied mostly (nearly 74%) by the subsidies from upstream hydrologic units. The value of water resources in each hydrologic unit (except the Zhujiang Delta) was more or less affected by the socio-economic conditions in downstream hydrologic units. We discussed the framework of the PES along with the principles of (1) interests sharing and responsibilities bearing, and (2) equal pay for equal work and based on the OCV of water resources supply of passing-by water. We also discussed the framework of water resources value quantification based on the OCV of water resources supply in our case study. It is obvious that these two frameworks based on the OCV will coordinate the development between hydrologic units and promote the watershed ecological civilization of Zhujiang River Basin. 参考文献 相似文献 引证文献