Eutrophication and the macroscope

It is important to view eutrophication as an increase in the supply of organic matter to an ecosystem rather than as a simple problem of nutrient pollution. This emphasizes that eutrophication is a fundamental change in the energetic base that may propagate through the system in various ways and produce a variety of changes. Some of these changes may be desirable (e.g., increased secondary production) and some may not (e.g., hypoxia). Defining eutrophication in terms of changing nutrient concentrations or chlorophyll levels or species composition confuses symptoms with the underlying phenomenon. While nutrient enrichment is the most common cause of eutrophication, it is not the only one. As recent and ongoing nutrient reductions make an impact in the coastal waters of the wealthier nations, we will see an increasing number of systems in which primary production is decreasing. This reduction in the supply of organic matter is here defined as oligotrophication, a phenomenon now well documented in lakes. So far, there has been little appreciation of this limnological study by coastal marine ecologists or managers, but there is much we can learn from it. The great ecologist H.T. Odum long argued that we need ‘macroscopes’ to help ecologists see the problems they study as they are embedded in the larger scales of nature and society. Marine eutrophication (and oligotrophication) is a perfect example of a problem that must be studied with a view toward the larger scales as well as toward the microscopic details. While much of the hardware (e.g., satellite imagery) for the mythical macroscope has been developed in the last 30 years, many ecologists and managers still look at eutrophication as a local problem linked to local sources of nutrient enrichment. Such a parochial view isolates eutrophication from its long intellectual history—a history that is linked to the development of our understanding of production in coastal waters. It also neglects the intellectual richness and complexity of eutrophication. One example of the importance of the macroscopic view is the emerging importance of climate-induced changes in phenology and the consequences of changing phenology on productivity. These changes may lead to eutrophication or oligotrophication. Climate changes may also exacerbate or alleviate conditions such as hypoxia that are associated with eutrophication. Seeing eutrophication in the macroscopic view is important for understanding and managing the phenomenon

Direct measurements of light attenuation by epiphytes on eelgrass \u3cem\u3eZostera marina\u3c/em\u3e

Declines in the seagrass Zostera marina L. in estuaries and lagoons have been attributed in part to reductions in irradiance reaching the seagrass blades. Epiphytes growing on Z. marina have the potential to attenuate a large fraction of the light that would otherwise reach the blades. This problem has previously been studied by measuring light penetration through homogenized epiphytic slurries or through glass slides fouled with epiphytes. However, the latter may not represent the natural succession or species composition found on live Z. marina leaves and the former does not preserve the structure of the epiphytic complex. Further, past studies have not measured attenuation across the full range of epiphytic densities found in the field. In this study, we measured light penetration across a wide range of epiphytic densities by holding scraped and unscraped Z. marina blades over a submerged light sensor. Results compared well with past studies at low epiphyte densities, with strong reductions in light penetration as density increased. However, at higher densities, penetration leveled off to a relatively constant value as the epiphytes floated out from the edges of the blade. Studies using slurries did not capture this phenomenon and thus predicted decreasing penetration down to 0%

Benthic community metabolism in a coastal lagoon ecosystem

Measurements of benthic oxygen production and consumption at 3 stations over an annual cycle in a shallow (mean depth = 0.7 m) coastal lagoon on the Rhode Island (USA) coast provide evidence that shallow benthic communities may consume more organic matter than can be provided by impressive rates of in situ epifloral production. While sandy sediment areas in Potter Pond lagoon showed a net daytime production of about 140 g C m-2 yr-l, the more extensive areas of fine-grained sediment did not show any significant amount of net benthic daytime production annually. Moreover when nighttime respiratory costs were included, the lagoon benthos as a whole showed a net organic consumption of 30 g C m-2 yr-l in spite of a net annual daytime production rate of 50 g C m-2 yr-l. Rates of in situ oxygen uptake by fine-grained lagoon sediments in the dark were not separable from those of similar sediments in much deeper (mean = 8.6 m) Narragansett Bay. For the lagoon as a whole, the benthos consumed about 40 to 50% of the combined primary production by phytoplankton, macrophytes and benthic epiflora. This partitioning is similar to that found in deeper, plankton-based systems with completely heterotrophic bottom communities

Nitrogen Inputs to Rhode Island Coastal Salt Ponds - Too Much of a Good Thing

Reviews concerns about increase of nitrogen in Rhode Island salt ponds as a result of human activities

Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus

Pyrococcus furiosus grows optimally near 100°C by fermenting carbohydrates to produce hydrogen (H2) or, if elemental sulfur (S0) is present, hydrogen sulfide instead. It contains two cytoplasmic hydrogenases, SHI and SHII, that use NADP(H) as an electron carrier and a membrane-bound hydrogenase (MBH) that utilizes the redox protein ferredoxin. We previously constructed deletion strains lacking SHI and/or SHII and showed that they exhibited no obvious phenotype. This study has now been extended to include biochemical analyses and growth studies using the ΔSHI and ΔSHII deletion strains together with strains lacking a functional MBH (ΔmbhL). Hydrogenase activity in cytoplasmic extracts of various strains demonstrate that SHI is responsible for most of the cytoplasmic hydrogenase activity. The ΔmbhL strain showed no growth in the absence of S0, confirming the hypothesis that, in the absence of S0, MBH is the only enzyme that can dispose of reductant (in the form of H2) generated during sugar oxidation. Under conditions of limiting sulfur, a small but significant amount of H2 was produced by the ΔmbhL strain, showing that SHI can produce H2 from NADPH in vivo, although this does not enable growth of ΔmbhL in the absence of S0. We propose that the physiological function of SHI is to recycle H2 and provide a link between external H2 and the intracellular pool of NADPH needed for biosynthesis. This likely has a distinct energetic advantage in the environment, but it is clearly not required for growth of the organism under the usual laboratory conditions. The function of SHII, however, remains unknown

A one hundred and seventeen year coastal water temperature record from Woods Hole,

ABSTRACT: We have compiled what we believe is the longest coherent coastal sea surface temperature record in North America. Near-surface water temperature measurements have been made almost daily at Great Harbor, Woods Hole, Massachusetts, since 1886 with remarkably few gaps. The record shows that there was no significant trend in water temperature at this site for the first 60 yr of observation. There was some cooling during the 1960s that was followed by a significant warming from 1970-2002 at a rate of 0.04؇C yr Ϫ1 . During the 1990s annual mean temperatures averaged approximately 1.2؇C warmer than they had been on average between 1890 and 1970; winter (December, January, and February) temperatures were 1.7؇C warmer and summer (June, July, and August) temperatures were 1.0؇C warmer. There has not been a statistically significant decrease in the annual number of winter days below 1؇C or an increase in the annual number of winter days above 5؇C. The number of summer days each year with water temperature above 21؇C has not increased significantly. The dates of first observations of 10؇C and 20؇C water in the spring have not changed sufficiently to be statistically significant. There is a weak positive correlation between annual and winter water temperature and the annual and winter North Atlantic Oscillation index, respectively, during the period of record

Nutrient Enrichment Drives Gulf of Mexico Hypoxia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95312/1/eost16763.pd

A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship

Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship

Exoplanet Diversity in the Era of Space-based Direct Imaging Missions

This whitepaper discusses the diversity of exoplanets that could be detected by future observations, so that comparative exoplanetology can be performed in the upcoming era of large space-based flagship missions. The primary focus will be on characterizing Earth-like worlds around Sun-like stars. However, we will also be able to characterize companion planets in the system simultaneously. This will not only provide a contextual picture with regards to our Solar system, but also presents a unique opportunity to observe size dependent planetary atmospheres at different orbital distances. We propose a preliminary scheme based on chemical behavior of gases and condensates in a planet's atmosphere that classifies them with respect to planetary radius and incident stellar flux.Comment: A white paper submitted to the National Academy of Sciences Exoplanet Science Strateg