A new approach for ecological quality assessment of macrophytes under WFD guidelines at the island of Helgoland (North Sea): integration of the British RSL- Index with additional quantitative parameters.

According to the EC Water Framework Directive (WFD), the quality of the coastal water type N5 at Helgoland (German Bight, North Sea) was assessed based on several years of quantitative monitoring and revision of historical qualitative data. The British Reduced Species List (RSL)-Index originally introduced by Emma Wells in 2007 was adapted to the local situation and extended by three quantitative parameters linked to water quality: (1) the sublittoral depth limit of selected macroalgae, (2) the spatial extension of dense Fucus beds and (3) the abundance of Ulva lactuca in a selected area. As a completely new approach, we propose to implement a sigmoid population model, describing the temporal development of a population, as the basis for setting boundaries within the classification matrix calculating the ecological quality ratio (EQR). Species richness, the basic ecological parameter in the RSL, was measured once during the main growingseason in 2006 and 2007. Calculation of the RSL-index and the EQR was adapted to the situation at Helgoland by using a local species list derived from historical references and by classifying macroalgae into the required ecological status groups (ESGs) and their state of opportunism proposing clear definitions for these categories. Results indicate a prominent deviation from the historical reference situation. The three additional parameters represent different trends in the reaction pattern to water quality: (1) Thesublittoral depth limits of Laminaria hyperborea and associated red algae increased between 1970 and 2007 and thereby mirrored the increase in water clarity since the period of intensive eutrophication in the 1970s. (2) As a major structuring part of the intertidal, the spatial extent of the main Fucus cover represents an important indicator but it is susceptible to perturbation. (3) Ephemeral algae like Ulva are typical nutrient indicators, but also appear as early successioners. The consistent appearance of tubular Ulva species (Enteromorpha) in areas with regular physical disturbance was thus notregarded as an indicator and omitted from the index. Abundance of Ulva lactuca, however, was incorporated, but has no quantitative historical reference. In the course of the final calculations, the metric EQRs of each parameter were weighted according to their relevance in sufficiently detecting changes in water quality. The median of all parameter-EQRs represented the final EQR for WFD purposes

Influence of physical perturbation on Fucus cover and restoration in the rocky intertidal of Helgoland (North Sea) and its significance for montitoring under the water framework directive (WFD).

Since the extent and abundance of the main Fucus cover is used as an indicator of water quality in the WFD at Helgoland and elsewhere, it is necessary to know the influence of seasonal changes in abundance and the possible restoration time after physical disturbances. The ongoing monitoring campaign started in autumn 2003 using 140 georeferenced sampling points in the northern part of the island where percentage cover of all macroalgal species is quantified in 50 x 50 cm plots revisited at each sampling date. In January 2007, a very intensive north-westerly storm most likely destroyed large parts of the Fucus serratus cover. After two years of rather consistent summer values in abundance and extent of the dense Fucus serratus beds, the mean percentage cover dropped from 100% to about 37% in February 2007, much lower than ever observed due to seasonal variation. Subsequent analysis in summer 2007 and in 2008 revealed a significant regrowth of Fucus serratus which is, however, still far from complete regeneration. Very important is the observation that understorey algae like Cladophorarupestris were not affected by the sudden removal of the top-layer and species richness remained the same. As it is the requirement of the WFD to detect changes in water quality which are not due to episodic events, continued observation of the restoration of the disturbed Fucus beds will generate the needed data. As the WFD demands values over time periods of six years, we recommend to only using the highest value observed over a six year period, thereby avoiding the strong variation due to episodic events like deleterious storms. This approach should be applied in all cases where perturbation byunusual episodic events is assumed for WFD parameters

Seasonal and diurnal variations in ultraviolet-B and ultraviolet-A irradiances at and below the sea surface at Helgoland (North Sea) over a 6-year period

UV radiation at 4 wavelengths (305, 320, 340 and 380 nm) and PAR were measured from May 1994 to October 1999 using Biospherical UV-radiometers. A surface reference sensor located on the roof of the Marine Station at Helgoland recorded values every 5 min, and an equivalent profiling underwater sensor was used for measurements in the sea at approximately monthly intervals. The ratio of 305 nm radiation to PAR varied seasonally, with a 14-fold increase from winter to summer. A much weaker seasonal trend (c. 1.5-fold) was apparent in the ratio of 320 nm radiation to PAR, but there was no seasonal trend in the ratios of 340 or 380 nm radiation to PAR. The year-to-year variations in 305 nm radiation were also much greater relative to PAR than for the other UV wavelengths, but there was no evidence of a change in the 305:PAR ratio over the study period. The ratios of both 305 and 320 nm radiation to PAR increased from dawn to midday, but those of 340 and 380 nm radiation were almost constant through the day, except shortly before sunrise and after sunset when the proportions of 340 and 380 nm radiation increased. Underwater measurements of PAR and UV suggest that the 1% depth for 305 nm radiation was little more than 1 m, but this estimate is valid only for summer and autumn because, in other seasons, few reliable readings for 305 nm radiation could be obtained underwater, and no attenuation coefficient could be calculated. The 1% depths recorded for the other UV wavelengths in the middle 6 months of the year were 2.0 m for 320 nm, 2.6 m for 340 nm and 4.6 m for 380 nm, compared with 12 m for PAR, but the attenuation of all wavebands increased sharply in October and remained higher until March. An analysis of the influence of sun angle, total column ozone concentration, the proportion of skylight, and cloud cover on the ratio of UV-wavelengths to PAR in surface irradiance demonstrated that solar angle has a greater influence than ozone concentration on the irradiance at 305 nm, and that the typical occurrence of ozone "holes" in spring may not result in higher UV-B irradiances than occur under higher ozone concentrations in summer. The implications of the data for attempts to model the biological effects of natural UV-radiation on marine organisms are considered