Application of filtration rate models to field populations of bivalves: an assessment using experimental mesocosms

Gross sedimentation of 14C labelled carbon was 58% greater in mesocosms (13 m3) containing the bivalve Mercenaria mercenaria (16 in m-2) relative to controls without this filter feeder. This difference was attributed to the activities of M. mercenaria and presumably due to filtration of particles from the water column. Of this increase, 32% and 47% were attributable to assimilation into clam tissue and respiration by the benthic community respectively. Permanent biodeposition by the clams contributed the least (21%). The ability of 8 filtration rate models to predict the increase in gross sedimentation was examined. Those models (4) which were based on data for bivalves filtering natural suspensions of particulate matter gave estimates which agreed well with observed differences. Those models (4) which yielded poor predictions used dues or algal monocultures to generate data and overestimated gross sedimentation due to bivalves by up to an order of magnitude. Such overestimation may exaggerate the role of bivalves in enhancing sedimentation and controlling phytoplankton biomass in shallow waters

The effects of the filter-feeding clam Mercenaria mercenaria on carbon cycling in experimental marine mesocosms

The metabolism and the fate of 14C labelled carbon was examined in 4 outdoor mesocosm (13 m3) tanks containing both benthic and pelagic compartments. Mesocosms with (16/m2) and without the clam, Mercenaria mercenaria were compared. System production, net and gross sedimentation of particulate carbon and benthic remineralization of dissolved inorganic nitrogen were all greater in mesocosms with clams. A filtration rate model, dependent on clam size and temperature, explained between 74–114% of the increased gross sedimentation in clam tanks relative to controls.The higher production in the clam tanks was at least in part due to a greater flux of dissolved inorganic nitrogen from the benthos. Despite this greater production in the clam tanks, water column biomass remained similar to controls. Calculations based on the filtration rate model indicated that clams could have consumed between 30% and 46% of the excess biomass produced during the day. Loss of particles due to processes in the water column appeared to consume most of this excess biomass. Although clams enhanced production and sedimentation, they did not limit phytoplankton biomass in the water column through filtration

A comparison of system (O\u3csub\u3e2\u3c/sub\u3e and CO\u3csub\u3e2\u3c/sub\u3e) and C-14 measurements of metabolism in estuarine mesocosms

Metabolism in estuarine mesocosms was measured by total system oxygen and carbon dioxide and by C-14 bottle incubations to determine the effects of nutrient enrichment (6 levels) over a 9 mo period. These data provided an unprecedented opportunity for calculating metabolic ratios (photosynthetic quotient [P.Q.] and respiratory quotient [R.Q.]) based on the 3 measures of metabolism and determining the impact of other system processes. System metabolism ratios based on daily data varied from 0 to 5.0. System metabolism ratios of P.Q. and R Q. based on integrated data were highly correlated (r = 0.95 to 0.96) and similar to traditional ratios obtained in phytoplankton studies. A system photosynthetic quotient of 1.2 and a system respiratory quotient of 1.1 were calculated from the integrated data. These ratios were only slightly affected by carbon dioxide diffusion and 3 benthic processes: denitrification, sulfur metabolism and calcium carbonate dissolution. There was no trend for system metabolism ratios up the nutrient gradient. The C-14 estimations of productivity appeared nitrogen limited in the lower nutrient treatments and provided lower estimates than the 2 system measures of production

Phosphorus and nitrogen limitation of primary production in a simulated estuarine gradient

The transition between phosphorus limitation of primary production in freshwater and nitrogen limitation in seawater was examined along an estuarine gradient simulated in 4 large 13 m3 enclosures connected in a series and containing pelagic and benthic subsystems. Nominal salinities of 0, 5, 10 and 25 ppt were maintained by exchanging appropriate volumes of water between enclosures. River water, which served as a freshwater endmember, was naturally high in N relative to P, while the oceanic endmember (water from Narragansett Bay, RI, USA) was low in N relative to P. Production in the water column was supported by external inputs and recycled nutrients. Bioassays, inorganic nutrient concentrations and N:P ratios of the seston and inorganic nutrients indicated that phosphorus was limiting at 0, 5 and 10 ppt, while nitrogen was limiting at 25 ppt. Coincident with this shift in limiting nutrient was a shift in the N:P ratio of nutrient supply from greater than the Redfield ratio of 16 to less than 16. External inputs established relative rates of supply in each enclosure. The relative proportion of N and P in external inputs was largely a function of the hydrodynamic mixing of fresh (high N, low P) and salt water (low N, high P) endmembers. At the scale of the estuarine segment or enclosure, neither recycled inputs from the benthos and water column, nitrogen fixation nor internal losses of N and P to sedimentation and/or denitrification materially altered relative supply rates, despite a hydrodynamic residence time of 27 d

Coastal Lagoons and Climate Change: Ecological and Social Ramifications in the U.S. Atlantic and Gulf Coast Ecosystems

Lagoons are highly productive coastal features that provide a range of natural services that society values. Their setting within the coastal landscape leaves them especially vulnerable to profound physical, ecological, and associated societal disturbance from global climate change. Expected shifts in physical and ecological characteristics range from changes in flushing regime, freshwater inputs, and water chemistry to complete inundation and loss and the concomitant loss of natural and human communities. Therefore, managing coastal lagoons in the context of global climate change is critical. Although management approaches will vary depending on local conditions and cultural norms, all management scenarios will need to be nimble and to make full use of the spectrum of values through which society views these unique ecosystems. We propose that this spectrum includes pragmatic, scholarly, aesthetic, and tacit categories of value. Pragmatic values such as fishery or tourism revenue are most easily quantified and are therefore more likely to be considered in management strategies. In contrast, tacit values such as a sense of place are more difficult to quantify and therefore more likely to be left out of explicit management justifications. However, tacit values are the most influential to stakeholder involvement because they both derive from and shape individual experiences and beliefs. Tacit values underpin all categories of social values that we describe and can be expected to have a strong influence over human behavior. The articulation and inclusion of the full spectrum of values, especially tacit values, will facilitate and support nimble adaptive management of coastal lagoon ecosystems in the context of global climate change

Myristate and the ecology of AM fungi : significance, opportunities, applications and challenges

A recent study by Sugiura and coworkers reported the nonsymbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology

A retrospective and agenda for future research on Chinese outward foreign direct investment

Our original paper “The determinants of Chinese Outward Foreign Direct Investment” was the first theoretically based empirical analysis of the phenomenon. It utilised internalisation theory to show that Chinese state-owned firms reacted to home country market imperfections to surmount barriers to foreign entry arising from naivety and the lack of obvious ownership advantages, leveraging institutional factors including favourable policy stimuli. This special theory explained outward foreign direct investment (OFDI) but provided surprises. These included the apparent appetite for risk evinced by these early investors, causing us to conjecture that domestic market imperfections, particularly in the domestic capital market, might be responsible. The article stimulated a massive subsequent, largely successful, research effort on emerging country multinationals. In this Retrospective article we review some of the main strands of research that ensued, for the insight they offer for the theme of our commentary. Our theme is that theoretical development can only come through embracing yet more challenging, different, and new contexts, and we make suggestions for future research directions

Truffle crops and soil drugs : new fungal practices and epistemologies for the 21st century

Thesis: Ph. D. in History, Anthropology, and Science, Technology and Society (HASTS), Massachusetts Institute of Technology, Program in Science, Technology and Society, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 255-276).Perigord truffles (Tuber melanosporum) have, over the past 200 years, become a cultivated crop grown across the globe. Since the 1890s, soil microbes have been commodified to "fertilize" agricultural crops (and are now referred to as biofertilizers, biostimulants, or simply "soil drugs"). This dissertation examines both truffle crops and soil drugs to investigate how a beneficial relationship between plant roots and fungi has become meaningful in twenty-first century industrial societies. This fungus-root connection, which exists with over eighty percent of plant species, is called the mycorrhizal symbiosis.I draw on ethnographic research centered in Corvallis, Oregon, and Dijon, France to show how mycorrhizal practitioners (from foragers and farmers to laboratory researchers and industry boosters) have struggled against the biological constraints of the mycorrhizal symbiosis and have combined agronomic and agrarian epistemologies to develop a diverse suite of "sustainable" land management practices that promise "symbiotic efficiencies." In truffle farming, this has resulted in an ethic of professionalization (with "best practice" guidelines), and a desire for what Anna Tsing has called "scale making." At the same time, a contrasting ethos of "engaged waiting" guides a subset of truffle farmers who continue to steward agrarian ecologies by remaining attuned to a wide array of life forms and extended time frames. In the biofertilizer industry, mycorrhizal science has given rise to numerous methods for producing mycorrhizal inoculants, or soil drugs.Following the work of Christopher Henke, I discuss how mycorrhizal inoculants are poised to bring about two forms of repair to soil ecologies and industrial agriculture: maintenance and transformation. With both truffle farming and the mycorrhizal biofertilizer industry, I examine the challenges and controversies surrounding the efficacy of emergent mycorrhizal practices, testing claims about ecological restoration, universal standards of practice, and the role of farm consultants. A recent wave of mycorrhizal science employs experimental systems that look beyond a singular fungus-root pair to consider broad and indeterminate communities of fungi, bacteria, and plants; this new science critiques the use of commercial inoculants in favor of reformed agricultural practice (from plant breeding to tillage regimes) that directly consider the role of soil symbionts.by Peter Gibbs Oviatt.Ph. D. in History, Anthropology, and Science, Technology and Society (HASTS)Ph.D.inHistory,Anthropology,andScience,TechnologyandSociety(HASTS) Massachusetts Institute of Technology, Program in Science, Technology and Societ

Mycorrhizal technologies for an agriculture of the middle

Societal Impact Statement Across industrial societies, midsize farms are in decline. A future of sustainable agriculture will require more than industrial and cottage farmers. We show that emergent mycorrhizal science is well-suited to support applications for an “agriculture of the middle,” and note two obstacles to the development of more integrated mycorrhizal technologies: an overreliance on commercial inoculants (industrial agriculture) and a tendency to treat soil biology as a black box (cottage agriculture). In this paper, we aim to provoke conversation among policy makers, research funders, and corporate executives on the development of mycorrhizal technologies for an agriculture of the middle. Summary Arbuscular mycorrhizal fungi (AMF) are dealt with in agriculture in a strongly bifurcated way: products and techniques to optimize AMF communities are designed for either large-scale (industrial) or small-scale (cottage) farming operations. We show how research and applications with AMF are bound up in these contrasting visions for what agriculture should be—an industrial system based on economies of scale, or small-scale operations that cater to regional societies, economies, and ecologies. These distinct socially and technologically bound initiatives—which involve research institutions, government policies, corporate investment, activism, and public relations campaigns—we refer to as sociotechnical imaginaries. Drawing from emergent mycorrhizal research, we argue that mycorrhizal technologies are well-suited to an “agriculture of the middle,” a mode of farming that is not strictly scale-based, yet falls somewhere between the industrial and the cottage. Unlike these two extremes, middle agriculture does not have a well-established sociotechnical imaginary. Developing this collective vision poses a challenge: will a middle agriculture that uses AMF fall short of the established goals of industrial and cottage modes of farming? The process of determining appropriate compromises on a wide range of parameters is likely to be contested. However, we believe that calling attention to these extreme visions of agriculture, along with the divergent (if potential) roles of mycorrhizal applications, will jumpstart a productive dialogue among stakeholders, including farmers, policy makers, scientists, and industrialists. Highlighting extremes may also help stimulate ideas about building bridges between seemingly irreconcilable and contradictory approaches