Search results for "diel vertical migration"

Direct measurement of NO<sub>3</sub> reactivity in a boreal forest

2017

Abstract. We present the first direct measurements of NO3 reactivity (or inverse lifetime, s−1) in the Finnish boreal forest. The data were obtained during the IBAIRN campaign (Influence of Biosphere-Atmosphere Interactions on the Reactive Nitrogen budget) which took place in Hyytiälä, Finland during the summer/autumn transition in September 2016. The NO3 reactivity was generally very high with a maximum value of 0.94 s−1 and displayed a strong diel variation with a campaign-averaged nighttime mean value of 0.11 s−1 compared to a daytime value of 0.04 s−1. The highest nighttime NO3-reactivity was accompanied by major depletion of canopy level ozone and was associated with strong temperature…

Night, day, sunrise, sunset: do fish under snow and ice recognize the difference?

2008

1. Although boreal lakes are ice-covered for several months annually, little is known about the behaviour of fish under ice. To consider the reasons for diel vertical migrations (DVM) it is important to compare periods under ice as opposed to under open water. Echosounding provides a tool for non-intrusive continuous monitoring of fish, even in winter. 2. Changes in the vertical distribution of fish through six 48-h periods were monitored using a stationary, mounted echosounder that beamed vertically either from the bottom up or from the surface down from February to April, 2003. The up-beaming and down-beaming transducers were run alternately for 24 h each over the 48-h period. Standard ec…

Behavioral responses of Atlantic cod to sea temperature changes

2015

Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30–80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increase…

Rotifer vertical distribution in a strongly stratified lake: a multivariate analysis

1998

The main source of variation of rotifer species distributions in lake Arcas-2, a small karstic lake near Cuenca (Spain), was explored by means of principal components factor (PCA) and canonical correlation (CCA) analyses. PCA was performed using rotifer densities and CCA using rotifer densities plus physical and chemical parameters. Factor 1 of PCA separated summer species from winter-spring species and Factor 2 accounted for the variation in the vertical profile. Three summer species with different food habits (Polyarthra dolichoptera, Hexarthra mira and Asplanchna girodi) were grouped together at the positive end of Factor 1, while Factor 2 separated the two hypolimnetic species (Filinia …

The effect of temperature fluctuations on oxygen consumption and ammonia excretion of underyearling Lake Inari Arctic charr

1998

Underyearling Lake Inari Arctic charr Salvelinus alpinus were acclimated to 11·0) C for 3 weeks, and then one group was maintained at 11·0) C and others were exposed to 14·4) Cconst, 17·7) Cconst or a diel fluctuating temperature of 14·3° C ± 1° C (14·3° Cfluc). Routine rates of oxygen consumption and ammonia excretion were measured over 10 days before the temperature change and over 31 days following the change. Measurements were made on fish that were feeding and growing. The temperature increase produced an immediate increase in oxygen consumption. There was then a decline over the next few days, suggesting that thermal acclimation was rapid. For groups exposed to constant temperature th…

Diel vertical movements of zooplankton in lake La Cruz (Cuenca, Spain)

2000

The study of diel vertical movements of zooplankton in a small meromictic karstic lake (lake La Cruz), presenting highly stratified waters, was performed using two different methodologies: (i) samples were taken along the vertical profile and were compared at different hours in a diel cycle; (ii) some plankton traps were located at different depths, covering different periods of time, to catch organisms going upwards and downwards. The main subject of this study has been the vertical movements affecting rotifers since they were dominant in the zooplankton of this lake, but we have also included the results obtained for other zooplankton groups. The results indicate an almost general movemen…

Copepod limnocalanus macrurus mating in relation to vertical migrations and aspects of feeding rates in the Bothnian Sea (Baltic Sea)

2006

The studies of calanoid copepod Limnocalanus macrurus feeding rates and mating related to vertical migration were conducted in October 2005 in the Bothnian Sea. The monocyclic copepod Limnocalanus macrurus develops mostly to adult and larger copepodites stages in autumn and these stages were investigated. Bothnian Sea is a brackish-water basin in Baltic Sea with comparatively big depth therefore Limnocalanus macrurus which prefer to live in deep and cold water is more abundant in this Baltic Sea part. Recent observations in the Bothnian Sea showed that Limnocalanus macrurus performs diel vertical migrations and adults approve stricter tendency to stay under thermocline layer at night than c…

Diel Feeding Features of Juveniles of Two Sparids in the Stagnone di Marsala Coastal Sound (Western Sicily, Italy)

2001

Diet composition, feeding rhythms, gastric evacuation rates, daily rations of Diplodus puntazzo (Gmelin 1789) and Sarpa salpa (Linneo 1758) juveniles were studied in order to investigate their trophic ecology, niche breadth and overlap. These Sparids were collected in the Stagnone di Marsala (Western Sicily), in April 1997, in a 24 hour sampling period. Gastric content of 86 specimens of D. puntazzo (standard length = 31.9 ± 6.6 mm; body wet weight = 1.0 Ī 0.5 g) and of 100 specimens of S. salpa (standard length = 32.3 ± 2.9 mm; body wet weight = 0.6 Ī 0.2 g) were examined. Amphipoda and Tanaidacea were the most frequent prey items in stomach content of D. puntozzo, while Hydrozoa, Bryozoa …

2016

Abstract. Characterization of daytime sources of nitrous acid (HONO) is crucial to understand atmospheric oxidation and radical cycling in the planetary boundary layer. HONO and numerous other atmospheric trace constituents were measured on the Mediterranean island of Cyprus during the CYPHEX (CYprus PHotochemical EXperiment) campaign in summer 2014. Average volume mixing ratios of HONO were 35 pptv (±25 pptv) with a HONO ∕ NOx ratio of 0.33, which was considerably higher than reported for most other rural and urban regions. Diel profiles of HONO showed peak values in the late morning (60 ± 28 pptv around 09:00 local time) and persistently high mixing ratios during daytime (45 ± 18 pptv), i…

Diel feeding habits of juveniles of Mullus surmuletus (Linneo, 1758) in the lagoon of the Stagnone di Marsala (Western Sicily, Italy)

1999

Diet composition, feeding rhythm, gastric evacuation rate and daily ration were investigated in juvenile Mulhis surmuletus (Linneo, 1758). Fish were collected in the lagoon of the Stagnone di Marsala in western Sicily, in July 1995, during a 24 h sampling period. Copepoda, Polychaeta, Amphipoda and Tanaidacea were shown to be the most frequent prey items. The feeding index values showed two different daily feeding times. A unimodal trend in the daily rhythm of food consumption was derived, with a peak in feeding between 1200 and 2000 h. Gastric evacuation in juvenile M. surmuletus is best described by an exponential model, with a gastric evacuation rate R = 0.66 g h-1 (r = 0.88) (T = 24.45 …