Mathematical modelling of primary production in Green Bay (Lake Michigan, USA), a phosphorus-and light-limited system

Application of mathematical models in the design and evaluation of lake restoration programmes must include due consideration of three basic concepts of model development; 1) that the model framework is appropriately matched to the intended management use, 2) that selection of the proper degree of model complexity is fundamental to the achievement of model credibility and 3) that field and laboratory studies must be designed and interpreted with the aid of the model to insure development of a comprehensive, integrated tool.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41726/1/10452_2005_Article_BF02291163.pd

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWASs for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally diverse individuals (European, African, Asian, and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole-genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n = 109,122 individuals. We identified 59 sentinel variants (p < 5 × 10−9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated that the independent signals colocalized with cell-type-specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated that our TL polygenic trait scores (PTSs) were associated with an increased risk of cancer-related phenotypes

Some notes on water color in Keweenaw Bay (Lake Superior)

Spectral subsurface irradiance reflectance—intrinsic water color—was derived from above-water radiance measurements using a hand-held spectroradiometer along a transect on Keweenaw Bay, Lake Superior. The reflectance spectra were typical of oligotrophic lacustrine waters. The reflectance peak wavelength shifted from 484 nm at stations farthest offshore to 540 nm near the head of the bay. This change coincided with a decrease in Secchi-disk depth from 16 to 8 m, and an increase in concentrations of chlorophyll a and total suspended matter from about 0.45 to 0.60 mg m–3 and from 0.3 to 0.5 g m–3, respectively. The concentration of chromophoric dissolved organic matter (gilvin), expressed as the absorption of filtrate at 440 nm, varied between 0.11 and 0.2 m–1. Like almost all inland waters, Keweenaw Bay should be classified as a Case 2 water due to the concentrations of gilvin and inanimate particles relative to plankton biomass. A model for chlorophyll-a estimation from spectral reflectance that adequately predicted concentrations in mesotrophic to highly eutrophic Case 2 waters elsewhere gave negative values when applied to the Keweenaw Bay transect. Evidently, there is a need of algorithm development for oligotrophic lacustrine waters. Estimates improved using a modified blue to green band ratio algorithm previously applied for remote sensing of oceanic waters. In optimization of semi-empirical algorithms for estimation of plankton biomass in Lake Superior, absorption by gilvin as well as by inanimate particles merits special consideration. [KEYWORDS: Chlorophyll ; Lake Superior ; remote sensing ; spectral reflectance ; water color]

MERIS satellite chlorophyll mapping of oligotrophic and eutrophic waters in the Laurentian Great Lakes

Chlorophyll-a (Chla) concentrations and ‘water-leaving’ reflectance were assessed along transects in Keweenaw Bay (Lake Superior) and in Green Bay (Lake Michigan) (two of the Laurentian Great Lakes, USA), featuring oligotrophic (0.4–0.8 mg Chla m− 3) and eutrophic to hyper-eutrophic waters (11–131 mg Chla m− 3), respectively. A red-to-NIR band Chla retrieval algorithm proved to be applicable to Green Bay, but gave mostly negative values for Keweenaw Bay. An alternative algorithm could be based on Chla fluorescence, which in Keweenaw Bay was indicated by enhanced reflectance near 680 nm. Bands 7, 8 and 9 of the Medium Resolution Imaging Spectrometer (MERIS) have been specifically designed to detect phytoplankton fluorescence in coastal waters. A quite strong linear relationship was found between Chla concentration and fluorescence line height (FLH) computed with these MERIS bands. The same relationship held for observations on oligotrophic waters elsewhere, but not for Green Bay, where the FLH diminished to become negative as Chla increased. The remote sensing application of the algorithms could be tested because a MERIS scene was acquired coinciding with the day of the field observations in Keweenaw Bay and one day after those in Green Bay. For Green Bay the pixel values from the red-to-NIR band algorithm compared well to the steep Chla gradient in situ. This result is very positive from the perspective of satellite use in monitoring eutrophic inland and coastal waters in many parts of the world. Implementation of the FLH relationship in the scene of Keweenaw Bay produced highly variable pixel values. The FLH in oligotrophic inland waters like Lake Superior appears to be very close to or below the MERIS detection limit. An empirical algorithm incorporating three MERIS bands in the blue-to-green spectral region might be used as an alternative, but its applicability to other regions and seasons remains to be verified. Moreover, none of the algorithms will be suitable for mesotrophic water bodies. The results indicate that Chla mapping in oligotrophic and mesotrophic areas of the Great Lakes remains problematic for the current generation of satellite sensors.