Ecosystem Drivers Research Articles

Habitat Partitioning in the Marine Sector of Karst Subterranean Estuaries and Bermuda's Marine Caves: Benthic Foraminiferal Evidence

Karst subterranean estuaries (KSEs) are created from the two- and three-way mixing of saline groundwater, rain, and oceanic water in the subsurface on carbonate landscapes, and this hydrographic framework promotes unique physical processes, biogeochemical cycling, and biological communities. Here we provide evidence that the source and quantity of particulate organic matter (POM) that is delivered to the benthos strongly correlates to benthic habitat partitioning in the oxygenated marine sectors of KSEs. A dataset of benthic foraminifera at 128 different locations from several large flooded cave systems in Bermuda were compiled and evaluated against common environmental characteristics (e.g., tidal exposure, substrate particle size, bulk organic matter, C:N, total organic carbon, and δ13Corg). Benthic areas receiving more carbon isotopically depleted organic matter sources (mean δ13Corg values < −23.2‰, C:N ratios >11), most likely from the terrestrial surface and some marine plankton, were dominated by Trochammina inflata, Bolivina spp., and Helenina anderseni. In contrast, benthic areas receiving more carbon isotopically enriched organic matter sources (mean δ13Corg values > −21.6‰, C:N ratios <10), most likely from marine plankton transported through marine cave openings cave from adjacent coastal waters, were dominated by Spirophthalmidium emaciatum, Spirillina vivipara, Patellina corrugata, and Rotaliella arctica. The benthic foraminifera most distal from any cave entrances were dominated by taxa also known from the deep-sea (e.g., Rotaliella, Spirophthalmidium) in sediment with the lowest bulk organic matter content (mean: 6%), or taxa that prefer hard substrates and are potentially living attached to cave walls (Patellina, Spirillina). While physical groundwater characteristics (e.g., salinity, dissolved oxygen) are expected drivers of benthic ecosystems in KSEs, these results suggest that POM source, quantity, and delivery mechanisms (e.g., groundwater-seawater circulation mechanisms, terrestrial flux) play an important role in benthic habitat partitioning and the spatial variability of biogeochemical cycles in the oxygenated marine sector of KSEs.

Synergistic effects of long-term herbivory and previous fire on fine-scale heterogeneity of prescribed grassland burns.

Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and resultant fire heterogeneity. We carried out 36 controlled burns within replicated experimental plots that had allowed differential access by wild and domestic large herbivores since 1995 in a savanna ecosystem in Kenya. Half of these were reburns of plots burned 5 yr previously. We show here that the fine-scale spatial heterogeneity of fire was greater in plots (1) previously burned, (2) accessible to large herbivores, and especially (3) these two in combination. An additional embedded experiment demonstrated that even small experimental burn-free patches can have strong positive effects on tree saplings, which experienced less damage during controlled burns and quicker postfire recovery. This work highlights the importance of simultaneously examining the interactions between fire and herbivory on fuel heterogeneity, which can have important impacts on the growth of woody saplings in savanna grasslands.

Grass functional trait responses to experimental warming and fire in Afromontane grasslands

Climate change is one of the main challenges facing humanity in the coming century. To understand the impact of climate change on biodiversity and ecosystem functioning, we urgently require a better understanding of plant responses to climate change. To address this knowledge gap we established a full-factorial warming experiment using open-top chambers (OTCs) inside a long-term fire-manipulation experiment in Afromontane fire-climax grasslands. Fire is an essential ecosystem driver in these grasslands, but has rarely been included in experimental climate change research. To assess growth responses to elevated temperatures and fire frequency, we measured four functional traits: vegetative height, leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC). Grasses responded to fire exclusion with increased height, and lower LA, SLA, and LDMC. Grasses responded to warming with lower height and LA, and higher LDMC, suggesting that plant growth was negatively affected by warming. This response was mostly attributed to intra-specific trait variability, highlighting an important role for trait plasticity in community-level processes to mediate the response of montane grassland communities to elevated temperatures and associated drought effects. These results are a first step towards establishing a more mechanistic basis for understanding future climatic changes in Afromontane grasslands.

Biophysical drivers of net ecosystem and methane exchange across phenological phases in a tidal salt marsh

Salt marshes are large carbon reservoirs as part of blue carbon ecosystems. Unfortunately, there is limited information about the net ecosystem (NEE) and methane (CH4) exchange between salt marshes and the atmosphere to fully understand their carbon dynamics. We tested the influence of biophysical drivers by plant phenological phases (i.e., Greenup, Maturity, Senescence and Dormancy) on NEE and CH4 exchange in a grass-dominated temperate tidal salt marsh. We used three years of data derived from eddy covariance, PhenoCam (to measure vegetation phenology), and ancillary meteorological and water/soil variables. Overall, NEE showed significant differences among all phenological phases (p < 0.05), while CH4 exchange had significant differences among all phases except for Greenup and Dormancy. Net CO2 uptake was higher across Maturity (-61 g C-CO2 m2), while CO2 emissions were higher during Dormancy (182 g C-CO2 m2). The lower but constant CO2 emissions during Dormancy overshadowed the CO2 uptake during the growing season and contributed to >72% of the annual CO2 emissions in this ecosystem. Net CH4 emissions were higher during Maturity (3.7 g C-CH4 m2) and Senescence (4.2 g C-CH4 m2). Photosynthetically active radiation (PAR) substantially influenced (r2 > 0.57) daytime NEE across phenological phases, but a combination of variables including water table level (WTL), water temperature and atmospheric pressure were relevant to explain CH4 exchange. The study site was an overall net carbon source to the atmosphere with annual emissions of 13-201 g C-CO2 m−2yr−1 and 8.5-15.2 g C-CH4 m−2yr−1. Our findings provide insights on: a) the role of plant phenological phases on ecosystem-scale CO2 and CH4 fluxes; b) challenges for modeling ecosystem-scale CO2 and CH4 fluxes in salt marshes; and c) the potential net loss of carbon to the atmosphere that should be considered for carbon management and accounting in these ecosystems.

A Study on the Evolution Characteristics and Key Drivers of Urban Entrepreneurial Ecosystem: From the Perspective of Complexity Science

activity is a typical complex social system with significant regional heterogeneity. Most of the existing studies focus on explaining a certain aspect of entrepreneurial activities or exploring the extent to which regional entrepreneurial activities promote regional economic growth. However, examining regional entrepreneurial activities from a systematic rather than fragmented perspective may be able to reflect their internal and external quality more comprehensively and accurately. The purpose of this paper is to study the key factors affecting the quality of entrepreneurial activities in large Chinese cities based on the theories of Entrepreneurial and Complexity System, and put forward corresponding recommendation on policy design and policy implementation. Based on a systematic review of studies on city-level entrepreneurial ecosystems and the application of complexity science in entrepreneurial research, The Urban Entrepreneurship Ecosystem Index (UEEI) system is constructed, which consists of three dimensions of synergy, emergence and phase change, 10 first-level indicators and 40 second-level indicators. The cross-section data of 2018 are used to make quantitative analysis on China's top ten quasi-first-tier cities such as Wuhan and Chengdu. The results show that the urban entrepreneurial ecosystem is characterized by coordination, emergence and phase transformation, and the more balanced the three characteristics are, the higher the quality of the urban entrepreneurial ecosystem will be. In terms of specific indicators, employment, technological innovation and education are the key order parameters, and the performance of a key order parameter is particularly excellent, which is a common characteristic of high-quality urban entrepreneurial ecosystem.

Differences in ungulate population use in different hunting ground units in Lithuania

Abundant ungulate populations are considered ecosystem drivers that affect forestry and agriculture. Their management is ecologically and economically based on game density regulations, considering the balance between density and carrying capacity of the territory, population status and dynamics, as well as hunting needs.&#x0D; Although the population status and dynamics are not new questions, it is still unclear how to manage populations properly depending on the hunting intensity. We aimed to analyse and compare the ungulate population status like moose, red deer, roe deer and wild boar in the Punia pine forest, where the commercial hunting is conducted, and in the hunting grounds managed by hunter clubs in Prienai forest. We performed the study during four hunting seasons of 2009-2010, 2010-2011, 2011-2012, and 2012-2013. The data on harvesting and abundance were obtained from the field works and using the official statistics of the Ministry of Environment.&#x0D; The moose local populations are not abundant, or animals occur occasionally, and their density does not reach the minimum permissible rate. At the same time within the study area, moose hunting is remained to be insufficient. The red deer population is rather stable in the hunting grounds used by hunter clubs while hardly reaches the minimum density rate. On the commercial hunting area, the population density 2-3 times exceeds the permissible density rate. The red deer population should be harvested more intensively. The wild boar is used intensively in the grounds of hunter clubs, while animal density is close to the permissible rate. Unfortunately, on the areas of commercial hunting, wild boar is not actively managed that is why their density exceeds permissible rate even four times.&#x0D; The main harvested species are red deer and wild boar in both hunting grounds. Their abundant populations stay close to permissible density rate. However, gamekeepers keep the larger animal numbers on the areas of commercial hunting. As the main aim is the trophy hunting, the stags and boars are most used when compared to females and young. Therefore, on the areas of commercial hunting, use of wild boar and red deer is unreasonable and their density exceeds permissible rate several times. Keywords: commercial hunting, hunting clubs, population, status, ungulate

Differences in ungulate population use in different hunting grounds in Lithuania

Abundant ungulate populations are considered ecosystem drivers that affect forestry and agriculture. Their management is ecologically and economically based on game density regulations, considering the balance between density and carrying capacity of the territory, population status and dynamics, and hunting needs.&#x0D; Although the population status and dynamics are not a new question, it is still unclear how to manage populations properly depending on the hunting intensity. We aimed to analyse and compare the ungulate population status like moose, red deer, roe deer and wild boar in the Punia pine forest, where the commercial hunting is conducted, and in the hunting grounds managed by hunter clubs in Prienai forest. We performed the study during four hunting seasons 2009 - 2013. The data on harvesting and abundance were obtained from the field works and using the official statistics of the Ministry of Environment.&#x0D; The moose local populations are not abundant, or animals occur occasionally, and their density does not reach the minimum permissible level. The control of moose is non-purposeful and insufficient on both of study territories. The red deer population is rather stable on areas of hunting clubs while hardly reaches the minimum density level. On the commercial hunting area, the population density 2-3 times exceeds the permissible density level. Red deer population should be used more intensively. Wild boar is used intensively on the areas of hunter clubs, and animal density is close to the permissible level. Unfortunately, on the areas of commercial hunting, wild boar is used passively that is why their density exceeds permissible level even four times.&#x0D; The main harvested species are red deer and wild boar in both hunting grounds. Their numerous populations stay close to permissible density level. However, gamekeepers keep the larger animal numbers on the areas of commercial hunting. As the main aim is the trophy hunting, the stags and boars are most used when compared to females and young. Therefore, on the areas of commercial hunting, use of wild boar and red deer is unreasonable and their density exceeds permissible level several times.&#x0D; Keywords: commercial hunting, hunting clubs, population, status, ungulate

Homogeneous selection shapes free‐living and particle‐associated bacterial communities in subtropical coastal waters

AbstractAimIn microbial biogeography, it is crucial to link spatial patterns with underlying drivers in natural ecosystems. Bacterial communities driving key biogeochemical processes in coastal zones, which are important interfaces between terrestrial and marine ecosystems, are affected by perturbations due to both natural and anthropogenic factors. However, the assembly of bacterioplankton communities, either free‐living (FL) or particle‐associated, in coastal ecosystems is still poorly understood.LocationCoastal South China Sea influenced by the Pearl River (SCSPR).MethodsIn this study, we investigated FL, nanoparticle‐associated (NA) and microparticle‐associated (MA) bacterial communities in the SCSPR, using environmental DNA metabarcoding based on the V4 region of the 16S rRNA gene. We assessed the relative importance of ecological processes using null model analyses based on a two‐step framework.ResultsWe found that the observed amplicon sequence variants (ASVs) increased from FL, NA to MA communities, and a remarkably pervasive core set of ASVs closely belonged to potential hydrocarbonoclastic bacteria with wide habitat niche breadths. Analyses of similarity tests revealed that FL, NA and MA communities differed significantly but weakly, based on unweighted (R = 0.27, p &lt; .001) and weighted (R = 0.18, p &lt; .001) dissimilarities. Fundamental regulation of bacterial communities via homogeneous selection was most prominent in FL (90%), followed by NA (86.8%) and MA (73.3%), whereas the relative importance of dispersal limitation was most pronounced in MA (13.2%), followed by NA (11.7%) and FL (8.6%).Main conclusionsBacterial communities in the SCSPR can be predominantly influenced by human activities, as indicated by the core ASVs closely related to hydrocarbonoclastic bacteria. Importantly, anthropogenic influences can temporally overwhelm the large environmental heterogeneities in coastal ecosystems. This study fills knowledge gaps in bacterial community assembly, which may facilitate future studies regarding anthropogenic influences on coastal ecosystems.

Cumulative effects of marine renewable energy and climate change on ecosystem properties: Sensitivity of ecological network analysis

In an increasingly anthropogenic world, the scientific community and managers have to take interactions between the drivers of ecosystems into consideration. Tools like ecological network analysis (ENA) indices offer the opportunity to study those interactions at the ecosystem level. However, ENA indices have never been used to test the incidence of cumulative drivers. The present study uses models combining the effects of (i) the reef caused by the future offshore wind farm of Courseulles-sur-Mer and (ii) climate change on species distribution, to test the response of multiple ENA indices. ENA indices proved sensitive to this cumulative impact, displaying a wide variety of cumulative effects. They were also very powerful to characterize the role of the cumulative impact on ecosystem functioning. These results demonstrate the capacity of ENA indices to describe and understand cumulative effects at the ecosystem scale. Using a sensitivity analysis approach, this study shows that ENA indices could be viable tools for managers. To help them in their tasks, the next step could be to link ecosystem services to ENA indices for a more practical use.

Estimating the Value of Global Ecosystem Structure and Productivity: A Geographic Information System and Emergy Based Approach

We have used the coverages of renewable emergy input developed from satellite derived data to determine the emergy supporting ecosystem productivity and biotic natural capital. In addition, the impact on global productivity and biotic natural capital that has resulted from human induced land cover change was evaluated. The actual evapotranpiration (AET), which is the portion of rain that is used by vegetation was the most significant driver of ecosystems. However, the accumulation of biomass over time is not only affected by the available water used, but also by solar input and negatively affected by wind. Additionally, we have estimated the value of ecosystem function and storages. In pre-anthroponcene era, total annual emdollar value of global gross primary production was em$ 12.3 trillion and the total emdollar value of biotic natural capital which includes below and above ground biomass as well as the soil carbon was em$ 578.5 trillion. However, total losses of biotic natural capital from land cover change since the anthropocene began equal to em$88.5 trillion or about 16% of total pre-anthropocene value.

Variation in mammal diversity and habitat affect heterogeneity and processes of a granite catena

A higher variety of habitats normally result in higher diversity of species. The granite catenas near Skukuza, Kruger National Park (KNP), consist of different soil types along the hillslope, creating different habitats. Objectives were to determine the mammal species present on a catena and surrounding areas; to indicate their main period of activity; and to indicate human visibility in each catenal zone to explain landscape of fear principles. Camera trap surveys were conducted for short periods and repeated over three years. In total, 31 mammal species were observed on the catena, and its nearest waterholes. Small to mega-sized mammals were present, but some species were only observed during one survey period. Small changes were noticed in activity periods between survey periods, probably due to the drought. A severe drought changed vegetation structure and visibility, but the study area appeared to act as a drought forage refuge. The lowest visibility was found at the sodic patch upper-midslope ecotone, and shrub veld. This can possibly explain the lower number of mammal observations in these areas. Different habitats and habitat features were described which can affect the presence of mammals, i.e. the mud wallows that were created and maintained by the mammals. Future studies can focus on the impact of seasonal changes in mammal presence and on mammal diversity during a normal rainfall year. Conservation implications: To understand the mechanisms of herbivores as ecosystem drivers, aspects such as vegetation, soil and mammals should be combined. Better understanding of mammals, their habitats and associated processes can lead to better conservation actions.

Groundwater Microbial Communities in Times of Climate Change.

Climate change has a massive impact on the global water cycle. Subsurface ecosystems, the earth largest reservoir of liquid freshwater, currently experience a significant increase in temperature and serious consequences from extreme hydrological events. Extended droughts as well as heavy rains and floods have measurable impacts on groundwater quality and availability. In addition, the growing water demand puts increasing pressure on the already vulnerable groundwater ecosystems. Global change induces undesired dynamics in the typically nutrient and energy poor aquifers that are home to a diverse and specialized microbiome and fauna. Current and future changes in subsurface environmental conditions, without doubt, alter the composition of communities, as well as important ecosystem functions, for instance the cycling of elements such as carbon and nitrogen. A key role is played by the microbes. Understanding the interplay of biotic and abiotic drivers in subterranean ecosystems is required to anticipate future effects of climate change on groundwater resources and habitats. This review summarizes potential threats to groundwater ecosystems with emphasis on climate change and the microbial world down below our feet in the water saturated subsurface.

Evaluation of a large-scale flow manipulation to the upper San Francisco Estuary: Response of habitat conditions for an endangered native fish.

While flow is known to be a major driver of estuarine ecosystems, targeted flow manipulations are rare because tidal systems are extremely variable in space and time, and because the necessary infrastructure is rarely available. In summer 2018 we used a unique water control structure in the San Francisco Estuary (SFE) to direct a managed flow pulse into Suisun Marsh, one of the largest contiguous tidal marshes on the west coast of the United States. The action was designed to increase habitat suitability for the endangered Delta Smelt Hypomesus transpacificus, a small osmerid fish endemic to the upper SFE. The approach was to operate the Suisun Marsh Salinity Control Gates (SMSCG) in conjunction with increased Sacramento River tributary inflow to direct an estimated 160 x 106 m3 pulse of low salinity water into Suisun Marsh during August, a critical time period for juvenile Delta Smelt rearing. Three-dimensional modeling showed that directing additional low salinity water into Suisun Marsh ("Flow Action") substantially increased the area of low salinity habitat for Delta Smelt that persisted beyond the period of SMSCG operations. Field monitoring showed that turbidity and chlorophyll were at higher levels in Suisun Marsh, representing better habitat conditions, than the upstream Sacramento River region throughout the study period. The Flow Action had no substantial effects on zooplankton abundance, nor did Suisun Marsh show enhanced levels of these prey species in comparison to the Sacramento River. Fish monitoring data suggested that small numbers of Delta Smelt colonized Suisun Marsh from the Sacramento River during the 2018 Flow Action. Comparison of the salinity effects of the Flow Action to historical catch data for Suisun Marsh further supported our hypothesis that the Flow Action would have some benefit for this rare species. Our study provides insight into both the potential use of targeted flow manipulations to support endangered fishes such as Delta Smelt, and into the general response of estuarine habitat to flow management.

Lifting the Lid: Nitrifying Archaea Sustain Diverse Microbial Communities Below the Ross Ice Shelf

The oceanic waters beneath Antarctica’s Ross Ice Shelf are among the largest unexplored habitats on Earth. Previous studies have shown active microorganisms reside in these waters, but their identity and capabilities remain unknown. Here, we combined multi-omics and biogeochemical measurements to determine the composition and metabolic activities of microbial communities in the water column under the Ross Ice Shelf. We reveal that these waters harbour diverse and distinct assemblages of microorganisms. In an ecosystem devoid of photosynthesis, the heterotrophic majority are largely sustained by highly active nitrifying archaea and bacteria (using ammonium from basal ice) and by other chemolitoautotrophs using reduced sulfur compounds. This suggests that chemolitoautotrophy is an important ecosystem driver in the waters below the RIS. Our data provide a valuable insight into the processes that sustain the largest sub-ice marine ecosystem, and will help predictions of the evolution of this system in a rapidly evolving climatic scenario.

The influence of soil age on ecosystem structure and function across biomes

The importance of soil age as an ecosystem driver across biomes remains largely unresolved. By combining a cross-biome global field survey, including data for 32 soil, plant, and microbial properties in 16 soil chronosequences, with a global meta-analysis, we show that soil age is a significant ecosystem driver, but only accounts for a relatively small proportion of the cross-biome variation in multiple ecosystem properties. Parent material, climate, vegetation and topography predict, collectively, 24 times more variation in ecosystem properties than soil age alone. Soil age is an important local-scale ecosystem driver; however, environmental context, rather than soil age, determines the rates and trajectories of ecosystem development in structure and function across biomes. Our work provides insights into the natural history of terrestrial ecosystems. We propose that, regardless of soil age, changes in the environmental context, such as those associated with global climatic and land-use changes, will have important long-term impacts on the structure and function of terrestrial ecosystems across biomes.

Ecological dynamics of a peri-urban lake: a multi-proxy paleolimnological study of Cultus Lake (British Columbia) over the past ~ 200 years

Peri-urban lakes offer many valued ecosystem services, but their vulnerability to climate change and anthropogenic disturbances increases with increasing human populations the effects and interactions of multiple stressors on lakes can lead to unexpected outcomes, affecting societal and ecological values, it is necessary to evaluate ecosystem trajectories and respective drivers in peri-urban lakes. Better management practices could thus be applied to preserve ecosystem services of peri-urban lakes. We conducted a multi-proxy paleolimnological study on Cultus Lake, British Columbia, a Canadian peri-urban lake experiencing cultural eutrophication, to reconstruct a comprehensive ecological trajectory of the lake over the past ~ 200 years. We also integrated historical data as well as historical archival information to identify the potential drivers of the changes. We identified ca. 1800–1900 CE as a reference period, reflected in muted variations across most paleo-indicators. Minor increases in sedimentary δ15N ca. 1880–1940 CE coincided with the onset of anthropogenic modifications to the Cultus Lake watershed. Signs of early eutrophication were evident by ca. 1940 CE, as indicated by increases in all sedimentary pigments. By ca. 1970–1990 CE, elevated concentrations of sedimentary cyanobacterial pigments and changes in diatom species assemblages highlighted the potential interactive effects of multiple stressors, including cultural eutrophication, climate warming and declines in the endangered Cultus Lake sockeye salmon population. Recent (ca. 1990–2008 CE) declines in sedimentary pigments and increases in cladoceran fluxes suggested an increase in top-down control of the lake food web. From the collection of changes observed in the past ~ 200 years in our study, it is clear that Cultus Lake and its associated ecosystem services would benefit from abatement of nutrient loadings from terrestrial and atmospheric sources. Our study emphasizes the complexity and interactivity of drivers in peri-urban lake ecosystems and the necessity of long-term perspectives to contextualize modern ecological conditions to inform lake and watershed management.

Restoring the ecological integrity of a dryland river: Why low flows in the Barwon–Darling River must flow

SummaryFor dryland rivers globally, understanding hydro‐ecological function is fundamental to informing trade‐offs between consumptive water use and aquatic ecosystem integrity. The Barwon–Darling is an Australian dryland river system recognised for its hydrological variability, which is considered a primary driver of the riverine ecosystem. Emphasis has been placed on extremes of zero flow and flood but examining low flow hydrology and hydraulics – through historical and modern droughts – demonstrates that under natural conditions, the river system also exhibits persistent and predictable flow characteristics. From 1885 to 1950, prior to flow regulation, the Barwon–Darling flowed 92% of the time, and throughout severe droughts (1895–1903 and 1939–1945) the river system was characterised by: near‐perennial flows (85% of the time), with lotic (flowing water) habitats; and near‐annual, in channel, flow pulses. Furthermore, evidence of lotic biota is found consistently in Aboriginal middens dating over the past 15,000 years, thus indicating the long‐term persistence of lotic conditions. We propose these consistent hydrological and hydrodynamic features have shaped the ecology of aquatic biota in the Barwon–Darling River but are now experiencing unprecedented change. Flow storage and diversion have increased the frequency and duration of zero flows in some reaches, but arguably the most substantial impacts, along the entire river, are on: (i) low flows, which are now frequently below lotic thresholds, and (ii) the magnitude of near‐annual flow pulses, which are reduced by over 90%. Consequently, in modern droughts, the river becomes predominantly lentic (still‐water), an impact that is exacerbated by weirpools which create artificial lentic conditions for approximately 1000 km (40%) of river. The ecological impacts of these changes are increasingly apparent, with the loss of lotic biota and a reduction in biodiversity. An ecohydraulic perspective explains present impacts, provides new directions and some immediate solutions for river management, and clarifies choices for stakeholders.

Ecosystem indicators of marine survival in Puget Sound steelhead trout

Understanding ecosystem drivers of fish stock performance is essential to improving conservation and management. We used a hypothesis-driven approach to identify potential ecosystem indicators and developed a retrospective analysis using regression models of steelhead trout marine survival in Puget Sound, an urban estuary in Washington State, USA, over a 30-year time series. Indicators related to predator abundance, the presence of hatchery Chinook salmon in the system, salinity of marine waters, and timing of cumulative river discharge explained the most variance in smolt survival. Seal abundance was the strongest predictor, showing a strong negative relationship with steelhead marine survival, indicating that predation pressure may influence marine survival. Several other predictors were supported in our models, but with much less individual explanatory power. Our results support the conclusion that a combination of factors with differing mechanisms have likely contributed to declining survival of steelhead in inland marine waters. This study emphasizes the importance of collecting long-term survival and environmental data, taking a hypothesis-based approach to understanding ecosystem drivers related to marine survival, and evaluating the mechanisms associated with survival for species with complex life histories like anadromous steelhead trout.

Emerging challenges for resource management under ecosystem change: Example of cod in the Baltic Sea

Eastern Baltic cod is an example of a fish stock where fishing pressure has substantially declined after decades of intensive exploitation. However, in contrast to the expected improvements in stock status, stock productivity has concurrently declined to a historic low level. Targeted fisheries for the eastern Baltic cod were recently banned. However, at present low growth and high natural mortality, the stock biomass is projected to remain low, even in the absence of fishing. Thus, the future development in this stock and its potential recovery are largely dependent on ecosystem drivers likely contributing to the presently poor state of the cod stock (e.g. oxygen conditions, spatial distribution of prey species, abundance of marine mammals). Some of these ecosystem drivers and associated impacts on cod may be possible to influence by management measures, which are however not straightforward to implement. Moreover, scientific knowledge to guide management decisions in a complex ecosystem context is lagging behind. The Baltic cod case exemplifies the complexity of questions emerging for management as well as scientific advice under rapidly changing ecosystem conditions, where traditional fisheries management alone may have a limited potential to rebuild the stock.

Land Cover Changes from 1990 to 2019 in Papua, Indonesia: Results of the Remote Sensing Imagery

Long-term land cover changes play a significant driver of ecosystem and function of natural biodiversity. Hence, their analysis can be used for evaluating and supporting government plans, especially conservation and management of natural habitats such as sago palm. In Papua Province of Indonesia, sago palm has been stated as one of the priority plants in the Medium-Term Development Plan (R.P.J.M.). However, limited studies have examined this palm in one of the Regencies of Papua Province, namely, Merauke Regency. In this study, we performed remotely sensed data imagery and supervised classification to produce land cover maps from 1990 to 2019. During the study period, twenty-one land cover classes were identified. The six classes of the natural forest consist of primary dryland forest, secondary dryland forest, primary mangrove forest, secondary mangrove forest, primary swamp forest, and secondary swamp forest; thus, fifteen classes of non-forested area. Concerning the sago palm habitat, our study evaluated two different categories (1) based on the land cover scheme from the Ministry of Environment and Forestry and (2) according to the peatland land cover ecosystem in Papua. Based on paired samples t-test, the result indicated statistically significant changes specifically at primary dryland (p-value = 0.015), grassland (p-value = 0.002) and swamp (p-value = 0.007). Twelve from 20 districts of Merauke Regency tend to lose the forecasted natural habitat of the sago palm. Therefore, this study suggests the further need to recognize and estimate the yield of sago palm area in these various ecosystems.