Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development

Satellite remote sensing (RS) is routinely used for the large-scale monitoring of microphytobenthos (MPB) biomass in intertidal mudflats and has greatly improved our knowledge of MPB spatio-temporal variability and its potential drivers. Processes operating on smaller scales however, such as the impact of benthic macrofauna on MPB development, to date remain underinvestigated. In this study, we analysed the influence of wild Crassostrea gigas oyster reefs on MPB biofilm development using multispectral RS. A 30-year time series (1985-2015) combining high-resolution (30 m) Landsat and SPOT data was built in order to explore the relationship between C. gigas reefs and MPB spatial distribution and seasonal dynamics, using the normalized difference vegetation index (NDVI). Emphasis was placed on the analysis of a before-after control-impact (BACI) experiment designed to assess the effect of oyster killing on the surrounding MPB biofilms. Our RS data reveal that the presence of oyster reefs positively affects MPB biofilm development. Analysis of the historical time series first showed the presence of persistent, highly concentrated MPB patches around oyster reefs. This observation was supported by the BACI experiment which showed that killing the oysters (while leaving the physical reef structure, i.e. oyster shells, intact) negatively affected both MPB biofilm biomass and spatial stability around the reef. As such, our results are consistent with the hypothesis of nutrient input as an explanation for the MPB growth-promoting effect of oysters, whereby organic and inorganic matter released through oyster excretion and biodeposition stimulates MPB biomass accumulation. MPB also showed marked seasonal variations in biomass and patch shape, size and degree of aggregation around the oyster reefs. Seasonal variations in biomass, with higher NDVI during spring and autumn, were consistent with those observed on broader scales in other European mudflats. Our study provides the first multi-sensor RS satellite evidence of the promoting and structuring effect of oyster reefs on MPB biofilms

A NEW ALGORITHM FOR COMPUTING COMPENSATED INCOME FROM ORDINARY DEMAND FUNCTIONS

This paper proposes a REversible Second-ORder Taylor (RESORT) expansion of the expenditure function to compute compensated income from ordinary demand functions as an alternative to the algorithm proposed by Vartia. These algorithms provide measures of Hicksian welfare changes and Konus-type cost of living indices. RESORT also validates the results by checking the matrix of compensated price effects. obtained through the Slutsky equation, for symmetry and negative semi-definiteness as required by expenditure minimization. In contrast, Vartia's algorithm provides no validation procedure. RESORT is similar to Vartia's algorithm in using price steps. It computes compensated income at each step "forward" from the initial to the terminal prices, and insures that the compensated income computed "backward" is equal to its value computed in the "forward" procedure. Thus, RESORT is "reversible" and guarantees unique values of compensated income for each set of prices and, as a result, also unique measures of welfare changes and cost of living indices. These unique results are not, however, guaranteed by the usual Taylor series expansion for computing compensated income.Research Methods/ Statistical Methods,

Electroweak Tests at Beta-beams

We explore the possibility of measuring the Weinberg angle from (anti)neutrino-electron scattering using low energy beta beams, a method that produces single flavour neutrino beams from the beta-decay of boosted radioactive ions. We study how the sensitivity of a possible measurement depends on the intensity of the ion beam and on a combination of different Lorentz boosts of the ions.Comment: 10 pages, 6 figure

An Alternative Framework for Sectoral Contributions to GDP Level and Growth: Application to the Philippines

This paper applies relative price weights–where relative price is the ratio of a sector’s GDP deflator to the aggregate GDP deflator–to convert sectoral real GDP to homogeneous units using the economy’s GDP as “numeraire” in an alternative framework for GDP level aggregation and growth decomposition. This alternative and the “traditional” framework–without relative price weights–are compared and applied to Philippine GDP to show that the latter framework is deficient and misleading for its inability to determine the effects on GDP growth of changes and differences in sectoral relative prices that need to be taken into account

Effects of Change in Relative Prices in Existing Decompositions of Aggregate Labor Productivity Growth: A Resolution of the Aggregate Effect

Diewert (2015) reworked Tang and Wang’s (2004) growth decomposition and claimed that: “Thus even if all industry labor productivity levels remain constant and all labor input shares remain constant, economy wide labor productivity growth can change due to changes in industry real output prices (italics added)” (p. 370). However, contrary to his 2015 claim, Diewert (2016) found “puzzling” results from Australian data where the sum of price change effects across industries did not matter much and explained this puzzle by an approximation formula that showed price effects sum to zero with the first-order accuracy. In contrast, this paper derives the exact formula that shows price effects sum to zero, depending on the quantity index underlying the GDP in the definition of aggregate labor productivity. It is shown that Diewert’s formula is an approximation to this paper’s exact formula showing that the aggregate effect of relative price changes is zer

Modifying the “Generalized Exactly Additive Decomposition” Decomposition”of GDP and Aggregate Labor Productivity Growth in Practice for Consistency with Theory

The generalized exactly additive decomposition (GEAD) of GDP and aggregate labor productivity (ALP) growth, originated by Tang and Wang (2004), is gaining attention in the literature and acceptance in practice. This paper shows, however, that the original GEAD is not always consistent with the “theory” that aggregate GDP growth is pure quantity growth and ALP growth depends only on productivity and labor share changes. This paper modifies the original GEAD for consistency, subject to certain requirement, depending on the GDP quantity index that in current practice is either (1) chained Laspeyres, (2) direct Laspeyres, or (3) chained Fisher. GEAD employs relative price to obtain contributions that exactly add up to GDP or ALP growth. Sector contributions equal pure growth effect plus price change effect (PCE) to GDP growth and with-in sector productivity growth effect plus inter-sectoral reallocation effect to ALP growth. When relative prices change, a sector’s PCE could be positive, zero, or negative but this paper shows that consistency with the above theory requires the Sum of PCE = 0 for all sectors. That is, there are no residual price effects. However, the original GEAD yields Sum of PCE = 0 only if the GDP quantity index is chained Laspeyres and, therefore, this paper modifies GEAD for theoretical consistency if the index is direct Laspeyres or chained Fisher. The findings are globally relevant because these three indexes underpin GDP in all countries in current practice

Consistency in Aggregation of GDP Indexes and Uniqueness of Quantity and Price Effects on Growth of GDP and Aggregate Labor Productivity

In traditional decomposition of GDP growth in constant prices, an industry’s contribution consisted only of a quantity effect from GDP growth. Tang and Wang’s (2004, 2014) innovation added a price effect from relative price change. Dumagan (2013a, 2016) showed that Tang and Wang’s quantity and price effects for all industries exactly add up to growth of GDP either in chained or in constant prices, that is, regardless of the GDP index. However, this paper shows that it is only when GDP is in chained prices and the GDP index is consistent-in-aggregation (CIA) that quantity and price effects are invariant with industry regroupings, that is, unique. Therefore, Tang and Wang’s (2004, 2014) growth decompositions in Canada and US—where GDP is in chained prices based on the Fisher index—yield effects that vary with industry regroupings because the Fisher index is not CIA. This variation prevents attributing unique price and quantity effects to industries and, thus, clouds Tang and Wang’s analysis of the role of industries in GDP growth and in aggregate labor productivity growth. This paper also examines price and quantity effects on GDP growth of representative countries with GDP different from that in the US to make the results globally relevant

Effects of Relative Prices on Contributions to the Level and Growth of Real GDP

Existing procedures for GDP in chained or in constant prices ignore relative prices – ratios of industry GDP deflators to the economy’s GDP deflator – and, consequently, yield economically misleading results by understating (overstating) level contributions of industries with above (below) average relative prices, at the same time understating (overstating) growth contributions of industries with rising (falling) relative prices. These are illustrated by US GDP in chained prices and Philippine GDP in constant prices. However, the above misleading results could be mitigated by this paper’s general formulas for level and growth contributions applied to the same GDP. While allowing for differences and changes in relative prices, these general formulas encompass existing formulas as special cases of constant relative prices. In principle, relative prices convert real GDP of industries to the same (i.e., homogeneous) units so that they can be added to equal (i.e., additive) aggregate real GDP. Without relative prices – and, therefore, no homogeneity and no additivity – industry contributions to the level and growth of aggregate real GDP are questionable