Data to investigate the role of Pomatoschistus microps in intertidal food webs, sampled off the island of Sylt

Ecological network analysis (ENA) was used to study the effects of Pomatoschistus microps on energy transport through the food web, its impact on other compartments and its possible role as a keystone species in the trophic webs of an Arenicola tidal flat ecosystem and a sparse Zostera noltii bed ecosystem. Three ENA models were constructed: (a) model 1 contains data of the original food web from prior research in the investigated area by Baird et al. (2007), (b) an updated model 2 which included biomass and diet data of P. microps from recent sampling, and (c) model 3 simulating a food web without P. microps. A comparison of energy transport between the different models revealed that more energy is transported from lower trophic levels up the food chain, in the presence of P. microps (models 1 and 2) than in its absence (model 3). Calculations of the keystone index (KSi) revealed the high overall impact (measured as eps_i) of this fish species on food webs. In model 1, P. microps was assigned a low KSi in the Arenicola flat and in the sparse Z. noltii bed. Calculations in model 2 ranked P. microps first for keystoneness and eps_i in both communities, the Arenicola flat and the sparse Z. noltii bed. Taken together, our results give insight into the role of P. microps when considering a whole food web and reveal direct and indirect trophic interactions of this small-sized fish species. These results might illustrate the impact and importance of abundant, widespread species in food webs and facilitate further investigations.

Temperature and photoperiod effects on sex determination in Leuresthes tenuis (fish)

In some gonochoristic species, sex is influenced not only by genotype at conception but also by the environment that offspring experience during early ontogeny (termed environmental sex determination or ESD). ESD is thought to be adaptive when seasonal variations in environmental conditions provide a sex-specific fitness advantage. In vertebrates, temperature is the most common determinant of sex, and seasonal variation in temperature serves as a temporal cue of environmental quality such as length of the growing season. Some environments, however, lack strong seasonal temperature fluctuations and other cues, particularly photoperiod, may provide a more reliable indicator of the environment offspring enter. We tested this hypothesis by rearing the offspring of the California grunion (Leuresthes tenuis, Ayres), which experiences low seasonal temperature variation in nature, under common garden conditions at three temperature and two photoperiod treatments. Our experiments revealed that both temperature and photoperiod significantly affected sex ratios in L. tenuis. More females were produced at cooler temperatures and longer day lengths, which is consistent with female biased sex ratios early in the breeding season, and likely adaptive through increased female size and fecundity. To our knowledge, this is the first documented case of photoperiod-dependent sex determination in a gonochoristic vertebrate.

Abundance, biomass, ingestion rates and daily ratios of Salpa thompsoni individuals sampled during POLARSTERN cruise ANT-XVIII/5b to the Eastern Belingshausen Sea

Distribution, density, and feeding dynamics of the pelagic tunicate Salpa thompsoni have been investigated during the expedition ANTARKTIS XVIII/5b to the Eastern Bellingshausen Sea on board RV Polarstern in April 2001. This expedition was the German contribution to the field campaign of the Southern Ocean Global Ocean Ecosystems Dynamics Study (SO-GLOBEC). Salps were found at 31% of all RMT-8 and Bongo stations. Their densities in the RMT-8 samples were low and did not exceed 4.8 ind/m**2 and 7.4 mg C/m**2. However, maximum salp densities sampled with the Bongo net reached 56 ind/m**2 and 341 mg C/m**2. A bimodal salp length frequency distribution was recorded over the shelf, and suggested two recent budding events. This was also confirmed by the developmental stage composition of solitary forms. Ingestion rates of aggregate forms increased from 2.8 to 13.9 µg (pig)/ind/day or from 0.25 to 2.38 mg C/ind/day in salps from 10 to 40 mm oral-atrial length, accounting for 25-75% of body carbon per day. Faecal pellet production rates were on average 0.08 pellet/ind/h with a pronounced diel pattern. Daily individual egestion rates in 13 and 30 mm aggregates ranged from 0.6 to 4.8 µg (pig)/day or from 164 to 239 µg C/day. Assimilation efficiency ranged from 73 to 90% and from 65 to 76% in 13 and 30 mm aggregates, respectively. S. thompsoni exhibited similar ingestion and egestion rates previously estimated for low Antarctic (~50°S) habitats. It has been suggested that the salp population was able to develop in the Eastern Bellingshausen Sea due to an intrusion into the area of the warm Upper Circumpolar Deep Water

Coastal retreat at the northern Baltic Sea between Flensburg and Travemünde

Long-term surveys of the coast bordering the western Baltic Sea in Schleswig-Holstein yielded extensive information over the retreat and condition of active cliffs. 181 cliffs with a total length of 148 km are present along the 55 km coastline including Fehmarn lsland and the Schlei Fjord. Depending on their temporal and spatial evolution, and geomorphological stability, the cliffs are subdivided in three separate classes - actively retreating escarpments, cliff Segments with potential for retreat and stable cliffs. 85 sections of the coastline with a total length of 59 km are classified as ,,active cliffs" that are undergoing retreat through natural erosion, collapse, and disintegration.

Swath sonar bathymetry during POLARSTERN cruise ANT-XXVI/3 (PS75) with links to multibeam raw data files

Multibeam data were collected during R/V Polarstern cruise ANT-XXVI/3 along track lines of about 10,400 NM total length along transits, survey profiles and during stationary work. Departing in New Zealand the ship passed Pacific Antarctic Ridge heading to Ross Sea. Main working area was the Amundsen Sea and Bellingshausen Sea. Recorded bathymetry is supplementing existing tracks e.g. of R.V. James Clark Ross and R.V. Nathaniel B. Palmer. The refraction correction was achieved utilizing CTD profiles or by the system's own cross fan calibration. The quality of data might be reduced during bad weather periods or adverse sea ice conditions. The dataset contains raw data that are not processed and thus may contain errors and blunders in depth and position.

Body sizes and dive characteristics of narwhals (Monodon monoceros) from Kakiak Point and Melville Bay (2005-2007)

We report on wintertime data collected from Baffin Bay and northern Davis Strait, a major gateway linking the Arctic with the subpolar North Atlantic, using narwhals (Monodon monoceros) as an oceanographic sampling platform. Fourteen narwhals were instrumented with satellite-linked time-depth-temperature recorders between 2005 and 2007. Transmitters collected and transmitted water column temperature profiles from each dive between December and April, where >90% of maximum daily dive depths reached the bottom. Temperature measurements were combined with 15 helicopter-based conductivity-temperature-depth (CTD) casts taken in April 2007 across central Baffin Bay and compared with hydrographic climatology values used for the region in Arctic climate models. Winter temperature maxima for whale and CTD data were in good agreement, ranging between 4.0°C and 4.6°C in inshore and offshore Baffin Bay and in Davis Strait. The warm Irminger Water was identified between 57°W and 59°W (at 68°N) between 200 and 400 m depths. Whale data correlated well with climatological temperature maxima; however, they were on average 0.9°C warmer ±0.6°C (P < 0.001). Furthermore, climatology data overestimated the winter surface isothermal layer thickness by 50-80 m. Our results suggest the previously documented warming in Baffin Bay has continued through 2007 and is associated with a warmer West Greenland Current in both of its constituent water masses. This research demonstrates the feasibility of using narwhals as ocean observation platforms in inaccessible Arctic areas where dense sea ice prevents regular oceanographic measurements and where innate site fidelity, affinity for winter pack ice, and multiple daily dives to >1700 m offer a useful opportunity to sample the area.

Swath sonar bathymetry during POLARSTERN cruise ANT-XVI/4 (PS53) with links to multibeam raw data files

Multibeam data were collected without operator supervision on R/V Polarstern cruise ANT-XVI/4 along track lines of 6385 NM total length. Data were achieved during transits and stationary work on the route from Cape Town to Bremerhaven via the Cape Verde Islands and the Canary Islands. The multibeam sonar system Hydrosweep DS-2 was operated using 59 beams and 90° aperture angle. The quality of data might be reduced during bad weather periods or adverse sea ice conditions. The dataset contains raw data that are not processed and thus may contain errors and blunders in depth and position.