Langfristige (1968-1990) und jahreszeitliche Dynamik der planktischen Diatomeen im Neusiedlersee

Nach Artenzahl und Menge repräsentieren die Diatomeen die Wichtigste Algengruppe im Neusiedler See/Fertő (Österreich/Ungarn), einem groβen Flachsee. Vergleichen mit den hunderten Arten des Periphytons ist die Artenzahl der Planktondiatomeen allerdings gering. Die Dynamik dieser Populationen wird von wenigen Arten geprägt, zu denen Chaetoceros muelleri, Cyclotella spp. (im wesentlichen C. meneghiniana), kleine zentrische Formen, kleine Fragilaria-Arten (v.a. F. construens), Synedra acus, Campylodiscus clypeus und Surirella peisonis gehören. Im Gegensatz zu den meisten anderen Seen weisen die Diatomeen im Neusiedler See keinen ausgeprägten Jahresgang auf. Zwischen Jänner und Dezember bewegen sich die Biomassewerte zwischen 294 und 778 µg 1(-1) (Mittelwert 550 µg 1(-1)) was im 22-jährigen Durchschnitt etwa 50% der Gesamtbiomasse ausmacht. Einige Arten, wie etwa Surirella, Campylodiscus und Chaetoceros sind im Sommer quantitativ häufiger. Die kleinen Nitzschien hingegen haben zu dieser Zeit ihr Minimum. Andere Arten treten das ganze Jahr über in ziemlich gleichen Mengen auf. Der Anteil der Diatomeen an der Gesamtbiomasse lag in den 60er und 70er Jahren um 70% und ging in der darauffolgenden Dekade auf 30-40% zurück als Folge der zunehmenden Bedeutung zunächst der rünalgen und später der Blaualgen. In den letzten Jahren traten die Kieselalgen wieder vermehrt auf und ihr Anteil an der Gesamtbiomasse stieg wieder auf 60%. Die geringe saisonale Abfolge in der Biomasse des Phytoplanktons geht wohl auf die ständige Lichtlimitation des Wachstums infolge der hohen Trübung des Wassers im Neusiedler See zurück. Zwischen der Biomasse der Diatomeen und dem Sestongehalt des Wassers besteht eine gute Beziehung (r=0,55; p<0,1). Zu Ortophosphat, Nitrat und Ammonium lieβ sich hingegen keine Korrelation herstellen. Für die Änderungen der Artenzusammensetzung des Phytoplanktons in den 70er Jahren war jedoch die Veränderung der Nährstoffverhältnisse im See von entscheidener Bedeutung

Lake surface temperature [in “State of the Climate in 2017”]

Observed lake surface water temperature anomalies in 2017 are placed in the context of the recent warming observed in global surface air temperature by collating long-term in situ lake surface temperature observations from some of the world’s best-studied lakes and a satellite-derived global lake surface water temperature dataset. The period 1996–2015, 20 years for which satellite-derived lake temperatures are available, is used as the base period for all lake temperature anomaly calculations

Joint field experiments for comparisons of measuring methods of photosynthetic production

During the 1st GAP Workshop at Konstanz in April 1982 comparative measurements of phytoplankton primary production by several techniques were conducted simultaneously at an offshore station in Lake Konstanz and an experimental algal pond. Suspended glass bottle exposure techniques using 14C and 13C uptake gave Pz (mg C m−3 h−1) values which varied considerably near-surface, but estimates of areal rates for the euphotic zone ΣPcu(mg C m−3 h−1) which were reasonably close. In the lake, ΣPz, from a vertical tube exposure (with 14C uptake) was greater than rates derived for integrated bottle samples. The oxygen bottle method permitted a good estimate of compensation depth, corresponding to in situ growth studies. There were difficulties in direct comparison between O2 and carbon methods. Correlation between them for Pz was good in the lake but poor in the pond, both for suspended bottle and vertical tube methods. This series demonstrates that despite reasonable overall estimates, comparatively minor methodological differences in experimental technique can cause large variatio

The success of the cyanobacterium Cylindrospermopsis raciborskii in freshwaters is enhanced by the combined effects of light intensity and temperature

Toxic cyanobacterial blooms in freshwaters are thought to be a consequence of the combined effects of anthropogenic eutrophication and climate change. It is expected that climate change will affect water mixing regimes that alter the water transparency and ultimately the light environment for phytoplankton. Blooms of the potentially toxic cyanobacterium Cylindrospermopsis raciborskii are expanding from tropical towards temperate regions. Several hypotheses have been proposed to explain this expansion, including an increase in water temperature due to climate change and the high phenotypic plasticity of the species that allows it to exploit different light environments. We performed an analysis based on eight lakes in tropical, subtropical and temperate regions to examine the distribution and abundance of C. raciborskii in relation to water temperature and transparency. We then conducted a series of short-term factorial experiments that combined three temperatures and two light intensity levels using C. raciborskii cultures alone and in interaction with another cyanobacterium to identify its growth capacity. Our results from the field, in contrast to predictions, showed no differences in dominance (>40% to the total biovolume) of C. raciborskii between climate regions. C. raciborskii was able to dominate the phytoplankton in a wide range of light environments (euphotic zone=1.5 to 5 m, euphotic zone/mixing zone ratio 1.5). Moreover, C. raciborskii was capable of dominating the phytoplankton at low temperatures (<15°C). Our experimental results showed that C. raciborskii growing in interaction was enhanced by the increase of the temperature and light intensity. C. raciborskii growth in high light intensities and at a wide range of temperatures, suggests that any advantage that this species may derive from climate change that favors its dominance in the phytoplankton is likely due to changes in the light environment rather than changes in temperature. Predictive models that consider only temperature as a drive factor can therefore fail in predicting the expansion of this potentially toxic cyanobacterium

Warming of Central European lakes and their response to the 1980s climate regime shift

Lake surface water temperatures (LSWTs) are sensitive to atmospheric warming and have previously been shown to respond to regional changes in the climate. Using a combination of in situ and simulated surface temperatures from 20 Central European lakes, with data spanning between 50 and ∼100 years, we investigate the long-term increase in annually averaged LSWT. We demonstrate that Central European lakes are warming most in spring and experience a seasonal variation in LSWT trends. We calculate significant LSWT warming during the past few decades and illustrate, using a sequential t test analysis of regime shifts, a substantial increase in annually averaged LSWT during the late 1980s, in response to an abrupt shift in the climate. Surface air temperature measurements from 122 meteorological stations situated throughout Central Europe demonstrate similar increases at this time. Climatic modification of LSWT has numerous consequences for water quality and lake ecosystems. Quantifying the response of LSWT increase to large-scale and abrupt climatic shifts is essential to understand how lakes will respond in the future

The fine structure of the comparative

The paper provides evidence for a more articulated structure of the comparative as compared with the one in Bobaljik (2012). We propose to split up Bobaljik's cmpr head into two distinct heads, C1 and C2. Looking at Czech, Old Church Slavonic and English, we show that this proposal explains a range of facts about suppletion and allomorphy. A crucial ingredient of our analysis is the claim that adjectival roots are not a-categorial, but spell out adjectival functional structure. Specifically, we argue that adjectival roots come in various types, differing in the amount of functional structure they spell out. In order to correctly model the competition between roots, we further introduce a Faithfulness Restriction on Cyclic Override, which allows us to dispense with the Elsewhere Principle

Global data set of long-term summertime vertical temperature profiles in 153 lakes

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes