3 research outputs found
Stream hydraulics and temperature determine the metabolism of geothermal Icelandic streams
Stream ecosystem metabolism plays a critical role in planetary biogeochemical
cycling. Stream benthic habitat complexity and the available
surface area for microbes relative to the free-flowing water volume are
thought to be important determinants of ecosystem metabolism. Unfortunately,
the engineered deepening and straightening of streams for
drainage purposes could compromise stream natural services. Stream
channel complexity may be quantitatively expressed with hydraulic parameters
such as water transient storage, storage residence time, and
water spiralling length. The temperature dependence of whole stream
ecosystem respiration (ER), gross primary productivity (GPP) and net
ecosystem production (NEP = GPPâER) has recently been evaluated with
a ânatural experimentâ in Icelandic geothermal streams along a 5â25 âŠC
temperature gradient. There remained, however, a substantial amount of
unexplained variability in the statistical models, which may be explained
by hydraulic parameters found to be unrelated to temperature. We also
specifically tested the additional and predicted synergistic effects of water
transient storage and temperature on ER, using novel, more accurate,
methods. Both ER and GPP were highly related to water transient storage
(or water spiralling length) but not to the storage residence time. While
there was an additional effect of water transient storage and temperature
on ER (r2 = 0.57; P = 0.015), GPP was more related to water transient
storage than temperature. The predicted synergistic effect could not be
confirmed, most likely due to data limitation. Our interpretation, based on
causal statistical modelling, is that the metabolic balance of streams (NEP)
was primarily determined by the temperature dependence of respiration.
Further field and experimental work is required to test the predicted synergistic
effect on ER. Meanwhile, since higher metabolic activities allow
for higher pollutant degradation or uptake, river restoration and management
should promote habitat diversity and complexity (hyporheic zone,
macrophyte patches, substrate heterogeneity), especially for microbial
activity.Le métabolisme des écosystÚmes aquatiques fluviaux joue un rÎle critique dans
les cycles biogéochimiques planétaires. La complexité des habitats benthiques
et lâaire disponible pour les microbes par rapport au volume dâeau qui sâĂ©coule
sont considĂ©rĂ©es comme des facteurs importants pour le mĂ©tabolisme de lâĂ©cosystĂšme.
Malheureusement, le creusement et lâalignement des cours dâeau pour
le drainage des terres pourraient compromettre les services naturels fournis par
les cours dâeau. Cette complexitĂ© peut ĂȘtre exprimĂ©e quantitativement avec des
paramĂštres hydrauliques tels que le stokage transitoire de lâeau dans le lit de la
riviÚre, la durée de résidence du stockage transitoire, et la longueur du flux en
hĂ©lice (ou spirale) de lâeau (distance moyenne parcourue par une molĂ©cule dâeau
dans la zone dâeau courante libre avant dâentrer dans la zone calme). Lâeffet de
la température sur la respiration globale des ruisseaux (ER), productivité primaire
brute (GPP) et production nette de lâĂ©cosystĂšme (NEP) a rĂ©cemment Ă©tĂ© Ă©valuĂ© au
travers dâune « expĂ©rience naturelle » dans des ruisseaux gĂ©othermiques islandais
le long dâun gradient de tempĂ©rature de 5â25 âŠC. Il resta, cependant, une quantitĂ©
substantielle de variabilité non expliquée par les modÚles statistiques, qui pourrait
ĂȘtre expliquĂ©e par les paramĂštres hydrauliques non reliĂ©s Ă la tempĂ©rature. Nous
avons aussi tout particuliÚrement testé les effets additionnels et en synergie du
stokage transitoire de lâeau et de la tempĂ©rature sur la respiration, en utilisant de
nouvelles méthodes. ER and GPP furent hautement corrélées au stockage transitoire
de lâeau (ou flux en hĂ©lice de lâeau), mais pas Ă la durĂ©e de rĂ©sidence du
stockage. Le stokage transitoire de lâeau et de la tempĂ©rature eurent un effect additionnel
sur ER (r2 = 0,57 ; P = 0,015), en revanche GPP était plus liée au stockage
transitoire de lâeau quâĂ la tempĂ©rature. Lâeffet en synergie ne put ĂȘtre confirmĂ©,
probablement dû aux limitations des données. Notre interpretation, basée sur un
modĂšle statistique causal, est que lâĂ©quilibre mĂ©tabolique des cours dâeau (NEP)
était principalement contrainte par la réponse de la respiration à la température.
Dâautres travaux de terrain et expĂ©rimentaux sont nĂ©cessaires pour tester notre
nouvelle hypothĂšse dâun effet en synergie sur ER. Dans lâattente, puisquâune plus
haute activité métabolique permet une rétention ou dégradation plus importante
des polluants, la restoration et la gestion des cours dâeau devraient promouvoir la
diversité et la complexité des habitats (hyporhéos, touffes de macrophytes, hété-
rogĂ©nĂ©itĂ© du substrat) particuliĂšrement pour lâactivitĂ© microbienne.This study was funded by the Scottish Government Rural and Environment Research and Analysis Directorate (RERAD), now Rural and Environment Science and Analytical Services (RESAS). J.R.M. acknowledges the support of the Richard Stockton College of New Jersey. We would like to thank Tryggvi Thordarson, director of the Research Station at Hveragerdi for lodging and his warm hospitality, Marc Stutter and two anonymous referees for their insightful comments on the manuscript.Peer ReviewedRitrĂœnt tĂmari
Physical and cognitive impact following SARS-CoV-2 infection in a large population-based case-control study
© 2023. The Author(s).BACKGROUND: Persistent symptoms are common after SARS-CoV-2 infection but correlation with objective measures is unclear. METHODS: We invited all 3098 adults who tested SARS-CoV-2 positive in Iceland before October 2020 to the deCODE Health Study. We compared multiple symptoms and physical measures between 1706 Icelanders with confirmed prior infection (cases) who participated, and 619 contemporary and 13,779 historical controls. Cases participated in the study 5-18 months after infection. RESULTS: Here we report that 41 of 88 symptoms are associated with prior infection, most significantly disturbed smell and taste, memory disturbance, and dyspnea. Measured objectively, cases had poorer smell and taste results, less grip strength, and poorer memory recall. Differences in grip strength and memory recall were small. No other objective measure associated with prior infection including heart rate, blood pressure, postural orthostatic tachycardia, oxygen saturation, exercise tolerance, hearing, and traditional inflammatory, cardiac, liver, and kidney blood biomarkers. There was no evidence of more anxiety or depression among cases. We estimate the prevalence of long Covid to be 7% at a median of 8 months after infection. CONCLUSIONS: We confirm that diverse symptoms are common months after SARS-CoV-2 infection but find few differences between cases and controls in objective parameters measured. These discrepancies between symptoms and physical measures suggest a more complicated contribution to symptoms related to prior infection than is captured with conventional tests. Traditional clinical assessment is not expected to be particularly informative in relating symptoms to a past SARS-CoV-2 infection.Peer reviewe
ï»żDispersal rate of Potamophylax cingulatus and Micropterna sequax (Trichoptera) in Iceland
During the 20th and 21st century, two species of Trichoptera have colonised Iceland. One species is Potamophylax cingulatus and the other is Micropterna sequax. Potamophylax cingulatus was not found in several extensive surveys before 1942, conducted by several entomologists. During a survey in streams in 1974â1978, the species was found to be common in east and north-east Iceland, but the Trichoptera species Apatania zonella was absent, where it was common before 1942. Searching collections of unidentified Trichoptera, a single specimen was found in east Iceland on 30 July 1959. The survey was repeated in 2004â2006 and the species had colonised most streams and rivers in Iceland and A. zonella had disappeared from many of them. Potamophylax cingulatus was first recorded in two light traps in south Iceland in 1997 with two specimens. The catch has increased continuously to 267 in 2022. Micropterna sequax was found in a single light trap at MĂłgilsĂĄ near Reykjavik in 2008. The annual catch has since grown from two specimens to 144. The species was found at Hvanneyri, 40 km north of the original site it was recorded from in 2018 (8 specimens) and, in 2021, it was found in KjĂłs, 11 km from the original site (one specimen based on a photograph). The dispersal rate for P. cingulatus was about 7â9 km/year, but the dispersal rate for the more recent settler M. sequax was found to be 4 km/year