Sven Adler

Effects of pile-driving on harbour porpoises (Phocoena phocoena) at the first offshore wind farm in Germany

The first offshore wind farm ‘alpha ventus’ in the German North Sea was constructed north east of Borkum Reef Ground approximately 45 km north off the German coast in 2008 and 2009 using percussive piling for the foundations of 12 wind turbines. Visual monitoring of harbour porpoises was conducted prior to as well as during construction and operation by means of 15 aerial line transect distance sampling surveys, from 2008 to 2010. Static acoustic monitoring (SAM) with echolocation click loggers at 12 positions was performed additionally from 2008 to 2011. SAM devices were deployed between 1 and 50 km from the centre of the wind farm. During aerial surveys, 18 600 km of transect lines were covered in two survey areas (10 934 and 11 824 km 2 ) and 1392 harbour porpoise sightings were recorded. Lowest densities were documented during the construction period in 2009. The spatial distribution pattern recorded on two aerial surveys three weeks before and exactly during pile-driving points towards a strong avoidance response within 20 km distance of the noise source. Generalized additive modelling of SAM data showed a negative impact of pile-driving on relative porpoise detection rates at eight positions at distances less than 10.8 km. Increased detection rates were found at two positions at 25 and 50 km distance suggesting that porpoises were displaced towards these positions. A pile-driving related behavioural reaction could thus be detected using SAM at a much larger distance than a pure avoidance radius would suggest. The first waiting time (interval between porpoise detections of at least 10 min), after piling started, increased with longer piling durations. A gradient in avoidance, a gradual fading of the avoidance reaction with increasing distance from the piling site, is hence most probably a product of an incomplete displacement during shorter piling events.

Terrestrial and Marine Foraging Strategies of an Opportunistic Seabird Species Breeding in the Wadden Sea

Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10–19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5–26.4 h (mean 8.7 h), and ranges varied from 3.0–79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5–333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period.

A comparison of relative abundance versus class data in diatom-based quantitative reconstructions

Relative species abundances are the most frequently applied data type used for modern or paleolimnological diatom studies. In contrast, plant ecologists save time by commonly using ordinal scale data (class data), where the abundance of a species is estimated using dominance classes, instead of relative abundance data. This study compares the performance of models based on ordinal diatom species class data (class 1: sporadic (<0-1%) up to class 6: dominant (>60%)) with similar model types based on relative abundance data for different regional training sets and sediment cores. First, relative diatom abundances were converted into ordinal classes. Species response to total phosphorous (TP) was modelled using both types of data - relative abundance and ordinal class data. Secondly, TP was reconstructed for six sediment cores from North-East Germany, Switzerland, and Denmark using WA and WA-PLS based on both types of data. Thirdly, 20 lake sediment surface samples with known relative diatom abundances and known water TP concentrations were recounted using an ordinal data scale to create an independent test set. No significant differences were found between relative abundance and class data for (1) explained species variance, (2) reconstructed TP values, and (3) inferred TP values of the 20 recounted samples. This approach demonstrates that past TP concentrations may also be reliably reconstructed using class data instead of relative diatom abundances. Thus, by using class data lake managers may not only obtain more long-term records past water quality, but this approach is also quicker and therefore more cost effective. Moreover, the findings of this study may also advance the use of automatic diatom identification with digital image recognition, as we demonstrate that not every damaged diatom valve needs to be identified.

Marine mammals and windfarms: Effects of alpha ventus on harbour porpoises

Offshore windfarms have the potential to affect marine mammal populations. For harbour porpoises, the threat considered most important is the influence of noise during the construction phase. Effects of the operational period that need to be considered can be either noise effects or effects due to alteration to the habitat where foundations were erected. Visual surveys and stationary acoustic monitoring showed a strong avoidance reaction during pile-driving while during the operational period results were inconclusive. In future, these impacts must be seen in a larger framework to predict the biological significance of cumulative effects.

Analysis of blood gases, serum fat and serum protein: a new approach to estimate survival chances of stranded Harbor seal (Phoca vitulina) pups from the German North Sea

BackgroundFacing numerous challenges, such as illness, storms or human disturbance, some harbor seal (Phoca vitulina) pups lose contact to their dams and are found abandoned along the North Sea coast. In Schleswig-Holstein, pups with the prospect of surviving rehabilitation are admitted to the Seal Center Friedrichskoog. Despite elaborate clinical health assessments on admission, including differential hematology, in 2010, 17% of 108 admitted pups did not survive the first 20 days. The death rate during the years 2006 and 2009 varied between 9 and 19%. To broaden the spectrum of variables which could be predictive for survival, blood gas and serum analyses were performed for 99 pups using venous blood. Variables included total CO2, pH, partial CO2, HCO3–, base excess and anion gap as well as glucose, urea nitrogen, sodium, potassium and chloride. Moreover, total serum protein and fat (triglyceride) concentrations were measured for all pups on admission.ResultsRepeated measurements of 12 randomly selected individuals revealed a significant (p = 0.002) positive influence of time in rehabilitation on triglyceride concentrations. This trend probably shows the improvement of the pups’ nutritional status as a consequence of the shift from milk replacer formula to fish. No such positive influence was detected for total protein concentrations though. Hematologic values, including blood gases, were not predictive for survival.ConclusionsFor the first time blood gas values are reported in this study for a large sample size (N = 99) of seal pups (regardless of their health status). The ranges and medians calculated from the data can serve as a stepping stone towards the establishment of reference values for neonate harbor seals. However, future investigations on the development of blood gases in harbor seals with different health conditions and ages over time are necessary to allow for a better understanding of acid–base regulation in harbor seals.

Effects of counting variances on water quality assessments: implications from four benthic diatom samples, each counted by 40 diatomists

The European Water Framework Directive (EU WFD) aims to improve and maintain the water quality of lakes and rivers. Diatoms play an important role for implementing the EU WFD as they are widely used to assess water quality. To asses and use diatom-based evaluations in practice, it is essential to know and to minimize the analyst-dependent variability of the primary diatom results. We compare the counting results of benthic diatoms from two river and two lake samples as identified by 40 participants of the first German benthic diatom intercalibration exercise. Differences among participants and auditors are calculated with the Bray-Curtis distance, and similarities are graphically displayed by detrended correspondence analyses. Additionally, this study identifies the effects of counting variances on the ecological water assessment with the German PHYLIB method for implementing the EU WFD using the above dataset. Counting result differences among participants may have a significant impact on the assessed water quality. Some taxonomically problematic taxa do not have indicator values (no impact), sometimes, several taxonomic mistakes counterbalance each other during assessment (no or minor impact), and sometimes, taxonomic differences greatly influence the assessment due to highly deviating taxon abundances and/or strongly differing indicator values between mistaken taxa. Intercalibration exercises promote discussion about taxonomy, identify problematic taxa, and harmonize taxonomic concepts among diatomists. Thus, the shown analyst-induced variability of diatom counts may be reduced with an intercalibration exercise, thereby further refining the accuracy of water quality assessments.

Organochlorine Burdens in Harbour Seals from the German Wadden Sea Collected During Two Phocine Distemper Epizootics and Ringed Seals from West Greenland Waters

Blubber and liver of harbour seals from the German Bight collected between 2001 and 2002 and ringed seals from West Greenland waters were investigated for hexachlorocyclohexane (α-, β- and γ-HCH), hexachlorobenzene (HCB), dichlorodiphenyltrichlorethane and its metabolites (DDT, DDE and DDD), and polychlorinated biphenyls (PCBs). In blubber and liver of both species PCBs 138 and 153 showed the highest concentrations, followed by PCBs 187, 180 and 170. With the exception of PCB 52, the PCB burden in liver and blubber of harbour seals was higher than in ringed seals but not always statistically significant. Compared to levels found in harbour seals from the first seal epidemic in 1988, individuals collected in 2002 showed a decrease in concentrations of organochlorines. These data show that ringed seals from arctic waters are exposed to as large a variety of organochlorines as harbour seals from the North Sea.

Evaluating the effects of offshore pile driving on Phocoena phocoena (harbor porpoises) by using passive acoustic monitoring.

The German offshore wind energy production will be largely expanded in the next years. As a test. the first offshore wind turbines in German waters were installed in 2009 at the “alpha ventus” wind farm site off the island of Borkum in the southern German Bight. The whole process is accompanied by environmental impact assessments (EIAs) covering all marine taxa and other relevant aspects such as noise emissions. A regulatory framework for conducting these investigations, the so-called StUK 3 (Bundesamt fur Seeschifffahrt und Hydrographie [BSH] 2007), is set by the permitting agency (BSH [Federal Maritime and Hydrographic Agency]). To evaluate whether these requirements are appropriate and lead to scientifically robust results, a comprehensive research study was conducted simultaneously at a larger scale and by using methods additional to the ones of the EIA studies. The aim of these investigations was to validate the existing requirements or improve methodologies and the scope of their use wherever appropriate.

Assessment of contaminant levels and trophic relations at a World Heritage Site by measurements in a characteristic shorebird species

The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, β-, γ-HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polybrominated diphenyl ethers (PBDEs) in blood and feathers from Eurasian oystercatchers (Haematopus ostralegus; n = 28) at the Elbe and compared it with a non-riverine site about 90 km further north. (1) Mean levels of all contaminants in feathers and serum were significantly higher at the river (∑PCBs: 27.6 ng/g feather, 37.0 ng/ml serum; ∑DDTs: 5.3 ng/g feather, 4.4 ng/ml serum) compared with the non-riverine site (∑PCBs: 6.5 ng/g feather, 1.2 ng/ml serum; ∑DDTs: 1.4 ng/g feather, 0.5 ng/ml serum). Mean ∑HCH and HCB levels were <1.8 ng/g in feather and < 1.8 ng/ml in serum at both sites. (2) Levels of most detectable compounds in serum and feathers were significantly related, but levels were not consistently higher in either tissue. (3) There was no significant relationship between trophic level in individual oystercatchers (expressed as δ15N) or the degree of terrestrial feeding (expressed as δ13C) and contaminant loads. (4) PBDEs were not detected in significant amounts at either site. The results of this study indicate that the outflow from one of Europes largest river systems is associated with significant historical contamination, reflected by the accumulation of contaminants in body tissues in a coastal benthivore predator.