Influences of Multi-Scale Habitat on Metabolism in a Coastal Great Lakes Watershed

Spatial heterogeneity influences ecosystem structure and function across multiple habitat scales. Although primary production and respiration are fundamental to energy cycling in aquatic ecosystems, we know relatively little about how habitat scale influences metabolism. In this study, we adopted a multi-scale habitat approach to evaluate primary production and respiration in a coastal Great Lakes watershed that is experiencing pressure from past, present, and anticipated future human activities. We divided the watershed into five macrohabitats (stream, river, wetland, drowned-river mouth lake, and Great Lake), two mesohabitats (benthic and water column), and four microhabitats (periphytic substrates: sand/sediment, rock, wood, and plant) for evaluation of spatial patterns and synchrony in metabolism. Factors that influenced patterns of metabolism were scale dependent. Algal biomass strongly influenced spatial patterns in metabolism at the meso- and microhabitat scales; greater algal biomass translated to higher areal-specific and lower chlorophyll-specific metabolism at benthic mesohabitat and sand/sediment and rock microhabitats. Benthic metabolism overwhelmed water column metabolism, irrespective of location or time of year. Watershed position was important at the macrohabitat scale, with greater overall metabolism in macrohabitats located lower in the watershed. Average synchrony in metabolism rates was greatest at the macrohabitat scale, suggesting metabolic patterns that are evident at finer scales may become integrated at coarser scales. Our results (1) show that spatial and temporal patterns in metabolism are shaped by factors that are dependent upon habitat scale; (2) highlight the importance of benthic productivity across habitat and season; and (3) suggest that hydrologic connectivity strongly influences ecosystem processes, although physical factors can affect these responses as evidenced by the low levels of synchrony between Lake Michigan and the other macrohabitats.     

Stability and synchrony across ecological hierarchies in heterogeneous metacommunities: linking theory to data

Understanding stability across ecological hierarchies is critical for landscape management in a changing world. Recent studies showed that synchrony among lower‐level components is key to scaling temporal stability across two hierarchical levels, whether spatial or organizational. But an extended framework that integrates both spatial scale and organizational level simultaneously is required to clarify the sources of ecosystem stability at large scales. However, such an extension is far from trivial when taking into account the spatial heterogeneities in real‐world ecosystems. In this paper, we develop a partitioning framework that bridges variability and synchrony measures across spatial scales and organizational levels in heterogeneous metacommunities. In this framework, metacommunity variability is expressed as the product of local‐scale population variability and two synchrony indices that capture the temporal coherence across species and space, respectively. We develop an R function ‘var.partition’ and apply it to five types of desert plant communities to illustrate our framework and test how diversity shapes synchrony and variability at different hierarchical levels. As the observation scale increased from local populations to metacommunities, the temporal variability of plant productivity was reduced mainly by factors that decreased species synchrony. Species synchrony decreased from local to regional scales, and spatial synchrony decreased from species to community levels. Local and regional species diversity were key factors that reduced species synchrony at the two scales. Moreover, beta diversity contributed to decreasing spatial synchrony among communities. We conclude that our new framework offers a valuable toolbox for future empirical studies to disentangle the mechanisms and pathways by which ecological factors influence stability at large scales.     

RELATIONSHIP BETWEEN PERIODIC RESUSPENSION EVENTS AND PHYTO-PLANKTON BLOOMS IN LAKE MICHIGAN

Lake Michigan provides an ideal location for comparing episodic physical forcing effects (storm events) on phytoplankton processes and the more persistent seasonal variability of phytoplankton communities. This is because of the duration and extent of the highly turbid, recurrent coastal plume (RCP) in the lake during the winter/early spring. Although the RCP coincides with the initiation of the basin wide spring diatom bloom, linkages between the duration and intensity of the plume and the prominent role of light availability in regulating Lake Michigan phytoplankton growth during the spring isothermal period have been postulated, but not verified. As such the concurrent physical and biological events provide a novel opportunity to examine how variations in biological rate processes, coupled with transport and resuspension phenomena associated with the RCP, affect the distributions of organisms, evolution of communities, and growth and primary production of Lake Michigan phytoplankton. In this study, phytoplankton assemblages from pre, post, and active plume events are examined from three stations in Lake Michigan. Species assemblages include chlorophytes, chrysophytes, and diatoms. The diatom flora was particularly abundant. Species composition changed rapidly during storm events, with resting cell forming taxa playing a significant role in these modifications. Ephemeral species appeared during the circulation event and decreased once storm activity subsided. Other taxa were able to establish themselves in the phytoplankton community during the plume events and persisted after storm activity subsided. Understanding activity during these circulation events will lead to a better understanding of overall community structure development throughout the year.     

全球气候变暖对“植物-害虫-天敌”互作系统的影响

全球气候变化是近来人类关注的焦点问题,其最显著的特征是气候变暖。因为昆虫具有生活周期短、繁殖率高等特点,所以,气候变暖对昆虫的发育、繁殖和存活会产生强烈的直接影响。气候变暖促使一些昆虫提前春天的物候现象,向高纬度或高海拔地区迁移。然而,昆虫在自然界并非孤立地存在,它们与寄主植物和自然天敌相互联系、相互作用,并在长期的进化过程中逐渐适应特定区域的气候条件。因此,全球气候变暖对"植物-害虫-天敌"的种间关系必然产生直接或间接的影响,导致不同昆虫之间以及昆虫与其相关营养层的物种之间的相互关系在气候变化下呈现出时间上的异步性和空间上的错位,从而影响植物的适应性和抗虫性、害虫的发生规律和危害程度以及天敌的种群消长和控害效能。昆虫除了可以通过休眠或滞育的方式在时间上避开高温的影响外,还可以通过迁飞或移动的方式在空间上避开高温的影响,在这种迁移和扩散不同步的情况下可能使害虫食性和取食植物的害虫及其天敌的种类发生变化,从而改变生物群落的组成与结构,影响生态系统的服务和功能。     

Decomposition rate of carrion is dependent on composition not abundance of the assemblages of insect scavengers

Environmental factors and biodiversity affect ecosystem processes. As environmental change modifies also biodiversity it is unclear whether direct effects of environmental factors on ecosystem processes are more important than indirect effects mediated by changes in biodiversity. High-quality resources like carrion occur as heterogeneous pulses of energy and nutrients. Consequently, the distribution of scavenging insects is related to resource availability. Therefore, carrion decomposition represents a suitable process from which to unravel direct effects of environmental change from indirect biodiversity-related effects on ecosystem processes. During three field seasons in 2010 we exposed traps baited with small-mammal carrion at 21 sites along a temperature gradient to explore the insect carrion fauna and decomposition rate in the Bohemian Forest, Germany. The abundance component of beetle and fly assemblages decreased with decreasing temperature. Independently, the composition component of both taxa changed with temperature and season. The change in the composition component of beetles depicted a loss of larger species at higher temperatures. Decomposition rate did not change directly along the temperature gradient but was directly influenced by season. The composition component of beetles, and to a small extent of flies, but not their abundance component, directly affected carrion decomposition. Consequently, lower decomposition rates at lower temperatures can be explained by the absence of larger beetle species. Thus, we predict that future environmental change will modify carrion fauna composition and thereby indirectly decomposition rate. Moreover, reorganizations of the insect carrion composition will directly translate into modified decomposition rates, with potential consequences for nutrient availability and carbon storage.     

Scaling‐up biodiversity‐ecosystem functioning research

A rich body of knowledge links biodiversity to ecosystem functioning (BEF), but it is primarily focused on small scales. We review the current theory and identify six expectations for scale dependence in the BEF relationship: (1) a nonlinear change in the slope of the BEF relationship with spatial scale; (2) a scale‐dependent relationship between ecosystem stability and spatial extent; (3) coexistence within and among sites will result in a positive BEF relationship at larger scales; (4) temporal autocorrelation in environmental variability affects species turnover and thus the change in BEF slope with scale; (5) connectivity in metacommunities generates nonlinear BEF and stability relationships by affecting population  synchrony at local and regional scales; (6) spatial scaling in food web structure and diversity will generate scale dependence in ecosystem functioning. We suggest directions for synthesis that combine approaches in metaecosystem and metacommunity ecology and integrate cross‐scale feedbacks. Tests of this theory may combine remote sensing with a generation of networked experiments that assess effects at multiple scales. We also show how anthropogenic land cover change may alter the scaling of the BEF relationship. New research on the role of scale in BEF will guide policy linking the goals of managing biodiversity and ecosystems.     

The sugarcane borer Diatraea saccharalis (Fabr.) (Lep., Crambidae) and its parasitoids: a synchrony approach to spatial and temporal dynamics

Abstract:  A data set on Diatraea saccharalis and its parasitoids, Cotesia flavipes and tachinid flies, was analysed at five spatial scales – sugarcane mill, region, intermediary, farm and zone – to determine the role of spatial scale in synchrony patterns, and on temporal population variability. To analyse synchrony patterns, only the three highest spatial scales were considered, but for temporal population variability, all spatial scales were adopted. The synchrony–distance relationship revealed complex spatial structures depending on both species and spatial scale. Temporal population variability [SD log( x  + 1)] levels were highest at the smallest spatial scales although, in the majority of the cases, temporal variability was inversely dependent on sample size. All the species studied, with a few exceptions, presented spatial synchrony independent of spatial scale. The tachinid flies exhibited stronger synchrony dynamics than D. saccharalis and C. flavipes in all spatial scales with the latter displaying the weakest synchrony levels, except when mill spatial scales were compared. In some cases spatial synchrony may at first decay and then increase with distance, but the presence of such patterns can change depending on the spatial scale adopted.     

Population synchrony of a native fish across three Laurentian Great Lakes: evaluating the effects of dispersal and climate

Climate and dispersal are the two most commonly cited mechanisms to explain spatial synchrony among time series of animal populations, and climate is typically most important for fishes. Using data from 1978–2006, we quantified the spatial synchrony in recruitment and population catch-per-unit-effort (CPUE) for bloater (Coregonus hoyi) populations across lakes Superior, Michigan, and Huron. In this natural field experiment, climate was highly synchronous across lakes but the likelihood of dispersal between lakes differed. When data from all lakes were pooled, modified correlograms revealed spatial synchrony to occur up to 800 km for long-term (data not detrended) trends and up to 600 km for short-term (data detrended by the annual rate of change) trends. This large spatial synchrony more than doubles the scale previously observed in freshwater fish populations, and exceeds the scale found in most marine or estuarine populations. When analyzing the data separately for within- and between-lake pairs, spatial synchrony was always observed within lakes, up to 400 or 600 km. Conversely, between-lake synchrony did not occur among short-term trends, and for long-term trends, the scale of synchrony was highly variable. For recruit CPUE, synchrony occurred up to 600 km between both lakes Michigan and Huron (where dispersal was most likely) and lakes Michigan and Superior (where dispersal was least likely), but failed to occur between lakes Huron and Superior (where dispersal likelihood was intermediate). When considering the scale of putative bloater dispersal and genetic information from previous studies, we concluded that dispersal was likely underlying within-lake synchrony but climate was more likely underlying between-lake synchrony. The broad scale of synchrony in Great Lakes bloater populations increases their probability of extirpation, a timely message for fishery managers given current low levels of bloater abundance.     

Does spatial variation in egg thiamine and fatty‐acid concentration of Lake Michigan lake trout Salvelinus namaycush lead to differential early mortality syndrome and yolk oedema mortality in offspring?

Individual variation in fatty-acid and thiamine concentrations were determined in lake trout Salvelinus namaycush eggs collected at two spawning grounds in Lake Michigan. A suite of predictor variables, including spawning location, egg fatty-acid and thiamine concentrations, were used to attempt to explain cause-and-effect in early life stage mortality among S. namaycush families. Lipid and fatty-acid composition of S. namaycush eggs differed between spawning locations. Salvelinus namaycush offspring from south-western Lake Michigan were affected by a high occurrence of yolk oedema, whereas a higher frequency of early mortality syndrome (EMS) was observed among offspring from the north-western part of the lake. Random-forest regressions revealed location as the most influential predictor of yolk oedema mortality, whereas thiamine level in eggs was the strongest predictor of EMS-related mortality. Several polyunsaturated fatty acids were also found to be predictors of both mortalities. There is evidence of spatial variability in egg fatty-acid concentration among S. namaycush in Lake Michigan that, together with diminished thiamine concentration, contribute to low survival of S. namaycush progeny.     

Spatial dynamics in the absence of dispersal: acorn production by oaks in central coastal California

We examined spatial patterns and spatial autocorrelation (synchrony) of annual acorn production in three species of oaks (genus Quercus ) over A 288 km transect in central coastal California. Over small (within-site) distances of <4 km, synchrony of acorn production between individual trees wits significant but varied through time and. for coast live oaks Q. agrifolia. differed al two sites 135 km apart. On a larger geographic scale, valley Q. lobata and blue Q. douglasii oaks exhibited significant synchrony in most distance categories between trees and sites up to 135 km apart and. in the case of coast live oaks, up to the maximum extent of the transect. Spatial patterns over this geographic scale also differed among species, with valley and blue oaks, but not coast live oaks, exhibiting distinct declines in synchrony of acorn production with distance. Interspecific synchrony in acorn production was generally lower than that within species but still significant over the entire extent of the survey. Spatial synchrony between sites was to some extent related to the same environmental variables previously found to correlate with annual acorn production within a site, suggesting that the environmental factors determining acorn production locally also influence spatial patterns over larger geographic areas. These results demonstrate that mast-fruiting in oaks occurs not only on a widespread geographic scale but also across species. They also confirm that synchrony over large geographic areas and complex spatial patterns varying in time can occur in systems where dispersal does not occur and thus environmental variability (the Moran effect) alone is likely to be driving spatial dynamics.     

Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout (Salvelinus namaycush) from Its Prey

A technique for laboratory estimation of net trophic transfer efficiency (γ) of polychlorinated biphenyl (PCB) congeners to piscivorous fish from their prey is described herein. During a 135-day laboratory experiment, we fed bloater (Coregonus hoyi) that had been caught in Lake Michigan to lake trout (Salvelinus namaycush) kept in eight laboratory tanks. Bloater is a natural prey for lake trout. In four of the tanks, a relatively high flow rate was used to ensure relatively high activity by the lake trout, whereas a low flow rate was used in the other four tanks, allowing for low lake trout activity. On a tank-by-tank basis, the amount of food eaten by the lake trout on each day of the experiment was recorded. Each lake trout was weighed at the start and end of the experiment. Four to nine lake trout from each of the eight tanks were sacrificed at the start of the experiment, and all 10 lake trout remaining in each of the tanks were euthanized at the end of the experiment. We determined concentrations of 75 PCB congeners in the lake trout at the start of the experiment, in the lake trout at the end of the experiment, and in bloaters fed to the lake trout during the experiment. Based on these measurements, γ was calculated for each of 75 PCB congeners in each of the eight tanks. Mean γ was calculated for each of the 75 PCB congeners for both active and inactive lake trout. Because the experiment was replicated in eight tanks, the standard error about mean γ could be estimated. Results from this type of experiment are useful in risk assessment models to predict future risk to humans and wildlife eating contaminated fish under various scenarios of environmental contamination.     

The Moran effect revisited: spatial population synchrony under global warming

The world is spatially autocorrelated. Both abiotic and biotic properties are more similar among neighboring than distant locations, and their temporal co-fluctuations also decrease with distance. P. A. P. Moran realized the ecological importance of such ‘spatial synchrony’ when he predicted that isolated populations subject to identical log-linear density-dependent processes should have the same correlation in fluctuations of abundance as the correlation in environmental noise. The contribution from correlated weather to synchrony of populations has later been coined the ‘Moran effect’. Here, we investigate the potential role of the Moran effect in large-scale ecological outcomes of global warming. Although difficult to disentangle from dispersal and species interaction effects, there is compelling evidence from across taxa and ecosystems that spatial environmental synchrony causes population synchrony. Given this, and the accelerating number of studies reporting climate change effects on local population dynamics, surprisingly little attention has been paid to the implications of global warming for spatial population synchrony. However, a handful of studies of insects, birds, plants, mammals and marine plankton indicate decadal-scale changes in population synchrony due to trends in environmental synchrony. We combine a literature review with modeling to outline potential pathways for how global warming, through changes in the mean, variability and spatial autocorrelation of weather, can impact population synchrony over time. This is particularly likely under a ‘generalized Moran effect’, i.e. when relaxing Moran's strict assumption of identical log-linear density-dependence, which is highly unrealistic in the wild. Furthermore, climate change can influence spatial population synchrony indirectly, through its effects on dispersal and species interactions. Because changes in population synchrony may cascade through food-webs, we argue that the (generalized) Moran effect is key to understanding and predicting impacts of global warming on large-scale ecological dynamics, with implications for extinctions, conservation and management.     

泸沽湖鱼类区系现状及人为影响成因的初步探讨

泸沽湖是位于滇西北的一个断陷湖泊,为滇川两省共有。文献记录泸沽湖原始的鱼类区系由4种鱼类组成,隶属于裂腹鱼属和泥鳅属。于2001 ,2002和2004年3次考察泸沽湖,进行标本采集和鱼类区系现状调查。查看了采自泸沽湖的鱼类标本518号,结合历史上的采集记录和大量相关文献,确定泸沽湖记录有鱼类12种,隶属于3目4科10属;过度捕捞和毁林造成的泥石流是泸沽湖鱼类区系变化的主要原因。     

Climate change‐related regime shifts have altered spatial synchrony of plankton dynamics in the North Sea

During the 1980s, the North Sea plankton community underwent a well‐documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic‐level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic‐level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959–1980 and 1989–2010. Twenty‐three plankton taxa, sea surface temperature (SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para‐pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate‐change impacts on synchrony. We discuss why climate‐change impacts on synchrony may well be more common and consequential than previously recognized.     

The human population — An ultimate receptor for aquatic contaminants

Human consumption of sport-caught fish represents a significant route of exposure to aquatic chemical contaminants. To investigate this, a cohort of Michigan residents was established and evaluated in 1974 and 1981. PCB, DDT and DDE concentrations dominated the eleven contaminants found in participant blood specimens. Those who regularly ate Lake Michigan fish had serum PCB levels up to 30 times greater than those who did not eat these fish. Serum levels briefly increased following each fish meal, correlated with annual fish consumption and correlated with the number of years fish had been consumed. Some homologs of PCB found at elevated levels in fisheaters have toxic properties. It appears that the human population can be a final receptor for Dersistent toxic chemical contaminants found in the environment.     

Yellow perch genetic structure and habitat use among connected habitats in eastern Lake Michigan

Maintenance of genetic and phenotypic diversity is widely recognized as an important conservation priority, yet managers often lack basic information about spatial patterns of population structure and its relationship with habitat heterogeneity and species movement within it. To address this knowledge gap, we focused on the economically and ecologically prominent yellow perch (Perca flavescens). In the Lake Michigan basin, yellow perch reside in nearshore Lake Michigan, including drowned river mouths (DRMs)—protected, lake‐like habitats that link tributaries to Lake Michigan. The goal of this study was to examine the extent that population structure is associated with Great Lakes connected habitats (i.e., DRMs) in a mobile fish species using yellow perch as a model. Specifically, we tested whether DRMs and eastern Lake Michigan constitute distinct genetic stocks of yellow perch, and if so, whether those stocks migrate between the two connected habitats throughout the year. To do so, we genotyped yellow perch at 14 microsatellite loci collected from 10 DRMs in both deep and littoral habitats during spring, summer, and autumn and two nearshore sites in Lake Michigan (spring and autumn) during 2015–2016 and supplemented our sampling with fish collected in 2013. We found that yellow perch from littoral‐DRM habitats were genetically distinct from fish captured in nearshore Lake Michigan. Our data also suggested that Lake Michigan yellow perch likely use deep‐DRM habitats during autumn. Further, we found genetic structuring among DRMs. These patterns support hypotheses of fishery managers that yellow perch seasonally migrate to and from Lake Michigan, yet, interestingly, these fish do not appear to interbreed with littoral fish despite occupying the same DRM. We recommend that fisheries managers account for this complex population structure and movement when setting fishing regulations and assessing the effects of harvest in Lake Michigan.     

Radiocaesium concentrations in the muscle and eggs of salmonids from Lake Chuzenji,Japan, after the Fukushima fallout

Approximately 18 months (September to December 2012) after the Fukushima Dai‐ichi Nuclear Power Plant accident, elevated radiocaesium concentrations were measured in samples of muscle and eggs from masu salmon Oncorhynchus masou, kokanee Oncorhynchus nerka, brown trout Salmo trutta and lake trout Salvelinus namaycush from the Lake Chuzenji system, central Honshu Island, Japan (160 km from the station). Mean muscle concentrations were 142·9–249·2 Bq kg^?1 wet mass and mean concentrations in eggs were 38·7–79·0 Bq kg^?1 wet mass. There was no relationship between fork length and muscle radiocaesium concentration in any of the species, but there were significant relationships between individual muscle and egg radiocaesium concentrations from O. masou, S. trutta and S. namaycush.     

Population ecology and spatial synchrony in the abundance of leaf gall wasps within and among populations of valley oak (Quercus lobata)

What factors drive population variability through space and time? Here we assess patterns of abundance of seven species of gall wasps in three genera occurring on the leaves of valley oaks (Quercus lobata) at 10 sites throughout this species' statewide range in California, from 2000 to 2006. Our primary goals were to understand the factors driving variability in gall abundance and to assess the extent of spatial synchrony in gall wasp communities at both large and small geographic scales. On the large, statewide scale, there was significant site-to-site variation in gall abundance, driven in all cases primarily by differences in mean maximum seasonal temperatures, and lesser year-to-year variation. In contrast, on the small, local scale, differences were more pronounced from year to year than from tree to tree, and were to some extent correlated with differences in acorn production, suggesting an interaction with the reproductive effort of hosts. Significant spatial synchrony was detected, particularly at the statewide scale, but in no case did synchrony decline significantly with distance, despite sites being up to 741 km apart. Variation in spatial synchrony was correlated with a number of exogenous factors, including seasonal weather conditions, the acorn crop at the statewide scale and soil phosphorus availability at the local scale; however, most variation in spatial synchrony in our analyses remained unexplained.     

The role of predation for seasonal variability patterns among phytoplankton and ciliates

Investigating the mechanisms which underlie the biomass fluctuations of populations and communities is important to better understand the processes which buffer community biomass in a variable environment. Based on long-term data of plankton biomass in Lake Constance (Bodensee), this study aims at explaining the different degree of synchrony among populations observed within two freshwater plankton groups, phytoplankton and ciliates. Established measures of temporal variability such as the variance ratio and cross-correlation coefficients were combined with first-order autoregressive models that allow estimating species interactions from time-series data. We found that predation was an important driver of the observed seasonal variability patterns in phytoplankton and ciliates, and that competitive interactions only played a subordinate role. In Lake Constance copepods and cladocerans, two major invertebrate predator groups, focus their grazing pressure at different times of the season. Model results suggested that compensatory dynamics detected in phytoplankton originate from the differential vulnerability of species to either one of these two predator groups. For ciliates model results advocated that synchrony among species occurs because ciliates tend to be vulnerable to both predator groups. Our findings underline the necessity of extending studies of community variability to multiple trophic levels because accounting for predator-prey interactions may often be more important than accounting for competitive interactions at one trophic level.