Ecosystem synchrony: an emerging property to elucidate ecosystem responses to global change.

Understanding ecosystem responses to global change have long challenged scientists due to notoriously complex properties arising from the interplay between biological and environmental factors. We propose the concept of ecosystem synchrony - that is, similarity in the temporal fluctuations of an ecosystem function between multiple ecosystems - to overcome this challenge. Ecosystem synchrony can manifest due to spatially correlated environmental fluctuations (Moran effect), exchange of energy, nutrients, and organic matter and similarity in biotic characteristics across ecosystems.

Watershed features shape spatial patterns of fish tissue mercury in a boreal river network.

Freshwater mercury (Hg) contamination is a widespread environmental concern but how proximate sources and downstream transport shape Hg spatial patterns in riverine food webs is poorly understood. We measured total Hg (THg) in slimy sculpin (Cottus cognatus) across the Kuskokwim River, a large boreal river in western Alaska and home to subsistence fishing communities which rely on fish for primary nutrition. We used spatial stream network models (SSNMs) to quantify watershed and instream conditions influencing sculpin THg.

Global investigation of lake habitat coupling by fishes.

Habitat coupling, where consumers acquire resources from different habitats, plays an important role in ecosystem functioning. In this study, we provide a global investigation of lake habitat coupling by freshwater fishes between littoral (nearshore) and pelagic (open water) zones and elucidate the extent to which magnitude of coupling varies according to environmental context and consumer traits. We consider the influence of lake factors (surface area, depth, shoreline complexity, and annual temperature), relative trophic position of consumers, fish community species richness, and fish morphological traits on habitat coupling by fishes.

Delayed trophic response of a marine predator to ocean condition and prey availability during the past century.

Understanding the response of predators to ecological change at multiple temporal scales can elucidate critical predator-prey dynamics that would otherwise go unrecognized. We performed compound-specific nitrogen stable isotope analysis of amino acids on 153 harbor seal museum skull specimens to determine how trophic position of this marine predator has responded to ecosystem change over the past century. The relationships between harbor seal trophic position, ocean condition, and prey abundance, were analyzed using hierarchical modeling of a multi-amino-acid framework and applying 1, 2, and 3 years temporal lags.

Optimizing Amazonian dams for nature.

Algorithms assess opportunities, forgone benefits, and environmental trade-offs.

Coupled CH production and oxidation support CO supersaturation in a tropical flood pulse lake (Tonle Sap Lake, Cambodia).

Carbon dioxide (CO) supersaturation in lakes and rivers worldwide is commonly attributed to terrestrial-aquatic transfers of organic and inorganic carbon (C) and subsequent, in situ aerobic respiration. Methane (CH) production and oxidation also contribute CO to freshwaters, yet this remains largely unquantified. Flood pulse lakes and rivers in the tropics are hypothesized to receive large inputs of dissolved CO and CH from floodplains characterized by hypoxia and reducing conditions.

Stable isotope signatures in historic harbor seal bone link food web-assimilated carbon and nitrogen resources to a century of environmental change.

Anthropogenic climate change will impact nutrient cycles, primary production, and ecosystem structure in the world's oceans, although considerable uncertainty exists regarding the magnitude and spatial variability of these changes. Understanding how regional-scale ocean conditions control nutrient availability and ultimately nutrient assimilation into food webs will inform how marine resources will change in response to climate. To evaluate how ocean conditions influence the assimilation of nitrogen and carbon into coastal marine food webs, we applied a novel dimension reduction analysis to a century of newly acquired molecular isotope data derived from historic harbor seal bone specimens.

Fluid-preserved fishes are one solution for assessing historical change in fish trophic level.

There are few resources available for assessing historical change in fish trophic dynamics, but specimens held in natural history collections could serve as this resource. In contemporary trophic ecology studies, trophic and source information can be obtained from compound-specific stable isotope analysis of amino acids of nitrogen (CSIA-AA-N).We subjected whole and to formalin fixation and 70% ethanol preservation.

Does lipid-correction introduce biases into isotopic mixing models? Implications for diet reconstruction studies.

Carbon isotopes are commonly used in trophic ecology to estimate consumer diet composition. This estimation is complicated by the fact that lipids exhibit a more depleted carbon signature (δC) than other macromolecules, and are often found at different concentrations among individual organisms. Some researchers argue that lipids bias diet reconstructions using stable isotopes and should be accounted for prior to analysis in food web mixing models, whereas others contend that removing lipids may result in erroneous interpretations of the trophic interactions under study.

Ocean acidification and warming effects on the physiology, skeletal properties, and microbiome of the purple-hinge rock scallop.

Ocean acidification and increased ocean temperature from elevated atmospheric carbon dioxide can significantly influence the physiology, growth and survival of marine organisms. Despite increasing research efforts, there are still many gaps in our knowledge of how these stressors interact to affect economically and ecologically important species. This project is the first to explore the physiological effects of high pCO and temperature on the acclimation potential of the purple-hinge rock scallop (Crassadoma gigantea), a widely distributed marine bivalve, important reef builder, and potential aquaculture product.

Response to Comment on "Designing river flows to improve food security futures in the Lower Mekong Basin".

Williams claim that the data used in Sabo were improperly scaled to account for fishing effort, thereby invalidating the analysis. Here, we reanalyze the data rescaled per Williams and following the methods in Sabo Our original conclusions are robust to rescaling, thereby invalidating the assertion that our original analysis is invalid.

Monitoring of tropical freshwater fish resources for sustainable use.

Tropical freshwater ecosystems are some of the world's most biodiverse and productive systems where determining what sustainable exploitation of inland fisheries looks like is particularly challenging. One of the greatest obstacles to sustainable management is collecting and using quality data on fish production and yield. The biodiversity and hydro-ecology of these systems often under open-access governance, add to the complexity of managing them.

Response to Comments on "Designing river flows to improve food security futures in the Lower Mekong Basin".

Sabo presented an empirically derived algorithm defining the socioecological response of the Tonle Sap Dai fishery in the Cambodian Mekong to basin-scale variation in hydrologic flow regime. Williams suggests that the analysis leading to the algorithm is flawed because of the large distance between the gauge used to measure water levels (hydrology) and the site of harvest for the fishery. Halls and Moyle argue that Sabo 's findings are well known and contend that the algorithm is not a comprehensive assessment of sustainability.

An assessment of assumptions and uncertainty in deuterium-based estimates of terrestrial subsidies to aquatic consumers.

The deuterium ratio ( H/ H) in tissue is often used to estimate terrestrial subsidies to aquatic consumers because of strongly differentiated values between terrestrial and aquatic primary producers. However, quantitative deuterium-based analyses of terrestrial resource assimilation are highly dependent on several poorly defined assumptions. We explored the sensitivity of these estimates to assumptions regarding environmental water contributions to consumer deuterium content (ω) and algal photosynthetic hydrogen discrimination (ε ).

Simulated eutrophication and browning alters zooplankton nutritional quality and determines juvenile fish growth and survival.

The first few months of life is the most vulnerable period for fish and their optimal hatching time with zooplankton prey is favored by natural selection. Traditionally, however, prey abundance (i.e.

A Fatty Acid Based Bayesian Approach for Inferring Diet in Aquatic Consumers.

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a 'consumer-resource library' of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This library corresponds to the resource or producer file in classic Bayesian mixing models such as MixSIR or SIAR.

Patterns of ecosystem metabolism in the Tonle Sap Lake, Cambodia with links to capture fisheries.

The Tonle Sap Lake in Cambodia is a dynamic flood-pulsed ecosystem that annually increases its surface area from roughly 2,500 km(2) to over 12,500 km(2) driven by seasonal flooding from the Mekong River. This flooding is thought to structure many of the critical ecological processes, including aquatic primary and secondary productivity. The lake also has a large fishery that supports the livelihoods of nearly 2 million people.

Centennial-scale fluctuations and regional complexity characterize Pacific salmon population dynamics over the past five centuries.

Observational data from the past century have highlighted the importance of interdecadal modes of variability in fish population dynamics, but how these patterns of variation fit into a broader temporal and spatial context remains largely unknown. We analyzed time series of stable nitrogen isotopes from the sediments of 20 sockeye salmon nursery lakes across western Alaska to characterize temporal and spatial patterns in salmon abundance over the past ∼500 y. Although some stocks varied on interdecadal time scales (30- to 80-y cycles), centennial-scale variation, undetectable in modern-day catch records and survey data, has dominated salmon population dynamics over the past 500 y.

Temperature-associated population diversity in salmon confers benefits to mobile consumers.

Habitat heterogeneity can generate intraspecific diversity through local adaptation of populations. While it is becoming increasingly clear that population diversity can increase stability in species abundance, less is known about how population diversity can benefit consumers that can integrate across population diversity in their prey. Here we demonstrate cascading effects of thermal heterogeneity on trout-salmon interactions in streams where rainbow trout rely heavily on the seasonal availability of anadromous salmon eggs.

Marine-derived nutrients, bioturbation, and ecosystem metabolism: reconsidering the role of salmon in streams.

In coastal areas of the North Pacific Ocean, annual returns of spawning salmon provide a substantial influx of nutrients and organic matter to streams and are generally believed to enhance the productivity of recipient ecosystems. Loss of this subsidy from areas with diminished salmon runs has been hypothesized to limit ecosystem productivity in juvenile salmon rearing habitats (lakes and streams), thereby reinforcing population declines. Using five to seven years of data from an Alaskan stream supporting moderate salmon densities, we show that salmon predictably increased stream water nutrient concentrations, which were on average 190% (nitrogen) and 390% (phosphorus) pre-salmon values, and that primary producers incorporated some of these nutrients into tissues.

Habitat structure determines resource use by zooplankton in temperate lakes.

While the importance of terrestrial linkages to aquatic ecosystems is well appreciated, the degree of terrestrial support of aquatic consumers remains debated. Estimates of terrestrial contributions to lake zooplankton have omitted a key food source, phytoplankton produced below the mixed layer. We used carbon and nitrogen stable isotope data from 25 Pacific Northwest lakes to assess the relative importance of particulate organic matter (POM) from the mixed layer, below the mixed layer and terrestrial detritus to zooplankton.

Bioaccumulation and transport of contaminants: migrating sockeye salmon as vectors of mercury.

Biological transport by migratory animals is increasingly recognized as important to the long-range dispersal of toxic contaminants. Mercury (Hg) contamination is a widespread environmental concern with serious health implications for humans and wildlife. Due to their unique life history, anadromous salmon may act as important vectors for this contaminant, transferring Hg between marine and freshwater ecosystems.