John Eyres Hobbie

John Eyres Hobbie
Marine Biological Laboratory | MBL · Ecosystems Center

PhD

About

296
Publications
38,143
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21,147
Citations
Citations since 2017
3 Research Items
3591 Citations
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20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600
20172018201920202021202220230100200300400500600

Publications

Publications (296)
Chapter
Principal Investigators from several sites within the Long Term Ecological Research (LTER) program offer their insights about how long-term research has been effectively sustained from periods ranging from 20 to 40 years. The sites are: Hubbard Brook (New Hampshire), Konza Prairie (Kansas), Niwot Ridge (Colorado), Arctic (Alaska), Palmer Station (A...
Article
Full-text available
Arctic ground squirrels (Urocitellus parryii) rely primarily on dietary protein derived from plants to fuel gluconeogenesis during hibernation, yet fungal sporocarps may be an important, yet overlooked, protein source. Fungivory levels depend on sporocarp productivity, which varies with the dominant plant species and is higher on acidic than on non...
Article
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Long-term measurements of ecological effects of warming are often not statistically significant because of annual variability or signal noise. These are reduced in indicators that filter or reduce the noise around the signal and allow effects of climate warming to emerge. In this way, certain indicators act as medium pass filters integrating the si...
Article
The Long-Term Ecological Research (LTER) Program is, in a sense, an experiment to transform the nature of science, and represents one of the most effective mechanisms for catalyzing comprehensive site-based research that is collaborative, multidisciplinary, and long-term in nature. The scientific contributions of the Program are prodigious, but the...
Chapter
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This chapter examines the basic ecology of streams in the Toolik Region. It prov information gathered from monitoring year-to-year variability and to identify long-term changes in the ecology of streams. It looks into the importance of understanding the role nutrients have in limiting and structuring stream ecosystems. It describes the ecological c...
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This chapter outlines evidence of direct and indirect changes in the ecology of Arctic Alaska caused by changes in the climate, and predicts ecological changes that could occur by the year 2100. It looks into the alterations that have been carried out and that will happen to air temperatures, precipitation, water balance, river discharge, and arcti...
Book
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This book synthesizes the findings from the NSF-funded Arctic LTER project based in Toolik Lake, Alaska, a site that has been active since the mid-1970s. The book presents research concerning the core issues of climate-change science, and addresses the treeless regions of arctic Alaska, as well as the adjoining boreal forests. The book examines bot...
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Understanding microbial transformations in soils is important for predicting future carbon sequestration and nutrient cycling. This review questions some methods of assessing one key microbial process, the uptake of labile organic compounds. First, soil microbes have a starving-survival life style of dormancy, arrested activity, and low activity. Y...
Conference Paper
Full-text available
Background/Question/Methods An overarching goal of the Arctic LTER project on the North Slope of Alaska is to measure changes in climate and their effects on the ecology of tundra, streams, and lakes. The research site is at Toolik Lake, 200 km south of the Arctic Ocean. At the site, detailed climate measurements have been made since 1989 and oth...
Conference Paper
Background/Question/Methods The source of N for trees in forest and tundra is a major question of plant ecology. Many scientists believe an important source is the amino acids (AA’s) in soils. However there is a paradox here; forests and tundra are strongly N-limited yet relatively large amounts of organic N and free AA’s exist in soil. When these...
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Much of the phylogenetic diversity in microbial systems arises from rare taxa that comprise the long tail of taxon rank distribution curves. This vast diversity presents a challenge to testing hypotheses about the effects of perturbations on microbial community composition because variability of rare taxa among environmental replicates may be suffi...
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Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to t...
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The arctic tundra ponds at the International Biological Program (IBP) site in Barrow, AK, were studied extensively in the 1970s; however, very little aquatic research has been conducted there for over three decades. Due to the rapid climate changes already occurring in northern Alaska, identifying any changes in the ponds' structure and function ov...
Conference Paper
Background/Question/Methods Background and Questions. Heterotrophic microbes in soil, bacteria and fungi, obtain carbon and energy from hotspots of root processes or the slow breakdown of soil organic carbon. Analysis of the non-hotspot microbes reveals that microbial biomass is much higher than can be supported by the measured inputs of carbon....
Article
The carbon cycle of the Kuparuk River, a meandering tundra stream, is dominated by inputs of eroding peat and leaching dissolved organic carbon from the tundra. Net production of epilithic algae is about 13 g C∙m−2∙yr−1, an order of magnitude less than inputs of allochthonous particulate organic carbon and two orders of magnitude less than inputs o...
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Functional redundancy in bacterial communities is expected to allow microbial assemblages to survive perturbation by allowing continuity in function despite compositional changes in communities. Recent evidence suggests, however, that microbial communities change both composition and function as a result of disturbance. We present evidence for a th...
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In radioisotope studies in plankton, bacteria turn over the nanomolar ambient concentrations of dissolved amino acids within a few hours. Uptake follows Michaelis–Menten kinetics. In contrast, within minutes the very abundant bacteria and fungi in soil take up all labeled amino acids added at nanomolar to millimolar final concentrations; uptake kin...
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Continuous time-series estimates of net ecosystem carbon exchange (NEE) are routinely made using eddy covariance techniques. Identifying and compensating for errors in the NEE time series can be automated using a signal processing filter like the ensemble Kalman filter (EnKF). The EnKF compares each measurement in the time series to a model predict...
Article
Recent analyses of land-use change in the tropical regions and in the temperate and boreal regions of the earth were combined to yield a global estimate of 1.0 - 2.6 times 1015 g C for the net release of carbon to the atmosphere in 1980 from changes in land use. Deforestation in the tropics accounted for nearly all of the flux; the net release of c...
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Mean epilimnetic temperatures from mid-June through mid-August in a small, arctic kettle lake had no trend from 1975 to 2008 and varied annually up to +/-3 degrees C relative to the mean. Analysis of data from temperature arrays deployed on the lake from 1998 to 2007 showed that as mean summer temperatures shifted from 2.5 degrees C below the mean,...
Conference Paper
Background/Question/Methods Aquatic microbiologists have long quantified amino acid (AA) cycling in samples of plankton by adding labeled compounds at nanomolar concentrations in short incubations and analyzing the rate of incorporation. The results are ecologically reasonable: nM of AA are measured, turnover times of individual AAs vary from minut...
Conference Paper
Background/Question/Methods Are the predictions of a simple ecosystem C flux model that was well corroborated with chamber data consistent with eddy-flux time series data? Is there information in the eddy-flux time series that can be used to improve the model? We embedded a simple model of arctic carbon exchange into the Ensemble Kalman Filter (EnK...
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A primary focus among microbial ecologists in recent years has been to understand controls on the distribution of microorganisms in various habitats. Much less attention has been paid to the way that environmental disturbance interacts with processes that regulate bacterial community composition. We determined how human disturbance affected the dis...
Article
We examined the role of chronic low-level nutrient enrichment on the productivity of heterotrophic marsh bacteria via a marsh fertilization experiment in which we mimicked the conditions of widespread coastal eutrophication by enriching entire salt marshes to approximately 15 × background nutrient concentrations. We measured the uptake of tritiated...
Article
On the premise that today's complex environmental challenges require innovative long-term study over many types of habitat and over large areas of the landscape, the National Science Foundation established the Long Term Ecological Research (LTER) Network. The LTER Network consists of 24 sites located throughout the climates and habitats of North Am...
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The 24 projects of the National Science Foundation's Long Term Ecological Research Network, whose sites range from the poles to the Tropics, from rain forests to tundras and deserts, and from offshore marine to estuarine and freshwater habitats, address fundamental and applied ecological issues that can be understood only through a long-term approa...
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Symbiotic fungi's role in providing nitrogen to host plants is well-studied in tundra at Toolik Lake, Alaska, but little-studied in the adjoining boreal forest ecosystem. Along a 570 km north-south transect from the Yukon River to the North Slope of Alaska, the 15N content was strongly reduced in ectomycorrhizal and ericoid mycorrhizal plants inclu...
Chapter
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Polar lakes and rivers encompass a diverse range of aquatic habitats, and many of these environments have broad global significance. This introduction to polar aquatic ecosystems presents a summary of the history of lake research in the Arctic and Antarctica, an overview of the limnological diversity within the polar regions, and descriptions of hi...
Chapter
This chapter examines the activities of heterotrophic microbes (bacteria, flagellates, and ciliated protozoans) in Antarctic continental lakes and Arctic lakes and ponds (Europe, Asia, North America, and Greenland). These microbial food webs consume almost all of the organic carbon produced in these inland waters (autochthonous carbon) or produced...
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Nitrogen (N) and phosphorus (P) dynamics in the Kuparuk River in arctic Alaska were characterized in a 3-year study using routine samples near the mouth of the river at the Arctic Ocean, synoptic whole-river surveys, and temporally intense sampling during storms in three headwater basins. The Lower Kuparuk River has low nitrate concentrations (mean...
Article
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The hyphae of ectomycorrhizal and ericoid mycorrhizal fungi proliferate in nitrogen (N)-limited forests and tundra where the availability of inorganic N is low; under these conditions the most common fungal species are those capable of protein degradation that can supply their host plants with organic N. Although it is widely understood that these...
Article
The glucose uptake of a species of Chlamydomonas was studied at various concentrations of d-glucose plus glucose-1-14C (0.003–10.0 mg/liter) and at various light levels (0–220 ft-c). The alga grows at 4 C either in the light or in the dark with added glucose, cellobiose, maltose, or fructose. Uptake of glucose could be described by the Michaelis-Me...
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The Genomic Standards Consortium (GSC) invited a representative of the Long-Term Ecological Research (LTER) to its fifth workshop to present the Ecological Metadata Language (EML) metadata standard and its relationship to the Minimum Information about a Genome/Metagenome Sequence (MIGS/MIMS) and its implementation, the Genomic Contextual Data Marku...
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Antarctica is renowned for its extreme cold; yet surprisingly, there is liquid water at the base of the Antarctic ice sheet several kilometers beneath the surface. The exploration of these subglacial aquatic environments is in its initial stages, and many fundamental questions about these environments can only be answered by entering and sampling t...
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Bacterioplankton community composition was compared across 10 lakes and 14 streams within the catchment of Toolik Lake, a tundra lake in Arctic Alaska, during seven surveys conducted over three years using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified rDNA. Bacterioplankton communities in streams draining tundra were very differen...
Article
Salt marsh ecosystems have been considered not susceptible to nitrogen overloading because early studies suggested that salt marshes adsorbed excess nutrients in plant growth. However, the possible effect of nutrient loading on species composition, and the combined effects of nutrients and altered species composition on structure and function, was...
Chapter
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Lakes are the downstream integrators of their surrounding catchments and are therefore highly responsive to variations in landscape properties. High latitude lakes share many characteristics with those of temperate latitudes and are subject to many of the same landscape controls. However, polar lakes and their catchments also experience persistent...
Article
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Changes in climate and ultraviolet radiation levels in the Arctic will have far-reaching impacts, affecting aquatic species at various trophic levels, the physical and chemical environment that makes up their habitat, and the processes that act on and within freshwater ecosystems. Interactions of climatic variables, such as temperature and precipit...
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Large variations exist in the size, abundance and biota of the two principal categories of freshwater ecosystems, lotic (flowing water; e.g., rivers, streams, deltas and estuaries) and lentic (standing water; lakes, ponds and wetlands) found across the circumpolar Arctic. Arctic climate, many components of which exhibit strong variations along lati...
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Various types of ecosystem-based climate proxies have been used to assess past arctic change. Although lotic records are relatively poor because of the constant reworking of riverine material, high-quality lentic data have been assembled back to the end of the Pleistocene and deglaciation of the circumpolar Arctic. In general, climatic variations i...
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In general, the arctic freshwater-terrestrial system will warm more rapidly than the global average, particularly during the autumn and winter season. The decline or loss of many cryospheric components and a shift from a nival to an increasingly pluvial system will produce numerous physical effects on freshwater ecosystems. Of particular note will...
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Climate change is projected to cause significant alterations to aquatic biogeochemical processes, (including carbon dynamics), aquatic food web structure, dynamics and biodiversity, primary and secondary production; and, affect the range, distribution and habitat quality/quantity of aquatic mammals and waterfowl. Projected enhanced permafrost thawi...
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Climate change is likely to act as a multiple stressor, leading to cumulative and/or synergistic impacts on aquatic systems. Projected increases in temperature and corresponding alterations in precipitation regimes will enhance contaminant influxes to aquatic systems, and independently increase the susceptibility of aquatic organisms to contaminant...
Article
When soil nitrogen is in short supply, most terrestrial plants form symbioses with fungi (mycorrhizae): hyphae take up soil nitrogen, transport it into plant roots, and receive plant sugars in return. In ecosystems, the transfers within the pathway fractionate nitrogen isotopes so that the natural abundance of 15N in fungi differs from that in thei...
Article
Whole system fluxes of isoprene from a moist acidic tundra ecosystem and leaf level emission rates of isoprene and monoterpenes from two important species in that same ecosystem ( Salix pulchra and Betula nana) were measured during the summer of 2005 to assess the contribution of biogenic volatile organic compounds on the chemistry of the Arctic at...
Article
The bacterioplankton community composition (measured with denaturing gradient gel electrophoresis of 16S ribosomal DNA (rDNA)) of two nonintersecting temperate rivers was nearly identical and changed synchronously over 2.5 yr, suggesting that intrinsic controls on bacteria were similar in the two rivers and that seasonal changes were driven by extr...
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Full-text available
Sulfate reduction, mediated by sulfate-reducing bacteria (SRB), is the dominant remineralization pathway in sediments of New England salt marshes. High sulfate reduction rates are associated with the rhizosphere of Spartina alterniflora when plants elongate aboveground. The growth process concurrently produces significant amounts of new rhizome mat...
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Full-text available
Summary1. To study the bottom-up linkages in arctic lakes, we treated one side of a partitioned lake with inorganic nitrogen and phosphorus for a 6-week period each summer for 6 years starting in the summer of 1985. We took a variety of weekly measurements to determine the impact of the nutrient loading on the lake and continued weekly measurements...
Article
When soil nitrogen is in short supply, most terrestrial plants form symbioses with fungi (mycorrhizae) in which fine hyphal threads take up soil nitrogen, transport it into plant roots, and in return receive plant sugars. Because the transfer rates are very difficult to measure in nature, ecologists need new tools by which to assess the role of myc...
Article
Full-text available
The biogeochemistry of North Atlantic salt marshes is characterized by the interplay between the marsh grass Spartina and sulphate-reducing bacteria (SRB), which mineralize the diverse carbon substrates provided by the plants. It was hypothesized that SRB populations display high diversity within the sediment as a result of the rich spatial and che...
Article
The down-slope movement of water and nutrients should link plant and soil processes along hill slopes. This linkage ought to be particularly strong in Arctic ecosystems where permafrost confines flowing water near the surface. We examined whether these hill-slope processes are important in assessments of the responses of Arctic tundra to changes in...
Article
A long-term stream fertilization experiment was performed to evaluate the potential eutrophication of an arctic stream ecosystem. During 16 years of summer phos- phorus (H3PO4) fertilization, we observed a dramatic change in the community structure of the Kuparuk River on the North Slope of Alaska. A positive response to fertilization was observed...
Article
Full-text available
Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electr...
Chapter
The Arctic LTER site is located at 68º38'N and 149º43'W, at an elevation of 760 m in the northern foothills of the Brooks Range, Alaska. The location, 208 km south of Prudhoe Bay, was chosen for accessibility to the Dalton Highway, which extends along the Trans-Alaska Oil Pipeline from north of Fairbanks to Prudhoe Bay on the Arctic Ocean (figure 5...
Article
This volume in the Long-Term Ecological Research Network Series would present the work that has been done and the understanding and database that have been developed by work on climate change done at all the LTER sites. Global climate change is a central issue facing the world, which is being worked on by a very large number of scientists across a...
Article
This volume in the Long-Term Ecological Research Network Series would present the work that has been done and the understanding and database that have been developed by work on climate change done at all the LTER sites. Global climate change is a central issue facing the world, which is being worked on by a very large number of scientists across a...
Article
There is substantial evidence that soil thermal dynamics are changing in terrestrial ecosystems of the Northern Hemisphere and that these dynamics have implications for the exchange of carbon between terrestrial ecosystems and the atmosphere. To date, large-scale biogeochemical models have been slow to incorporate the effects of soil thermal dynami...
Article
There is substantial evidence that soil thermal dynamics are changing in terrestrial ecosystems of the Northern Hemisphere and that these dynamics have implications for the exchange of carbon between terrestrial ecosystems and the atmosphere. To date, large-scale biogeochemical models have been slow to incorporate the effects of soil thermal dynami...