Description: Die Felseninsel Helgoland stellt innerhalb der südlichen Nordsee ein einzigartiges Habitat für Bodenorganismen dar. Die Makroalgenflora bildet Unterwasserwälder, die einer Vielzahl von tierischen und pflanzlichen Arten Schutz, Kinderstube, Nahrung und Substrat bieten. Ein Verlust oder größere Veränderungen dieser Wälder werden Konsequenzen für das ganze Ökosystem haben. Um Veränderungen registrieren zu können, müssen die Bestände räumlich, zeitlich und in ihrer Diversität erfasst werden. Das über 100 Jahre alte Herbarium an der Biologischen Anstalt Helgoland bietet die Möglichkeit, qualitative Veränderungen der Algenflora nachzuvollziehen (siehe auch www.gbif.org). Trotz des Verlustes und der Neuzugänge von Arten und Habitaten (Bartsch & Kuhlenkamp 2000), waren die meisten Biotope über die letzten 100 Jahre immer vorhanden (Bartsch & Tittley 2004). In den letzten beiden Jahrzehnten haben jedoch invasive Arten manche Bereiche drastisch verändert. In den letzten beiden Jahren wurden zwei Neuzugänge von Makroalgen-Arten aus südlicheren Gegenden registriert. Die Algentiefengrenzen haben sich im Unterwasserwald zwischen 1970 und 2005 auf Grund verbesserter Lichtbedingungen nach unten verschoben, was positiv zu bewerten ist. Eine wichtige Art des Unterwasserwaldes, der Brauntang Saccharina latissima, hat seine Bestände jedoch verringert, wobei die Ursachen dafür unbekannt sind. Raum-zeitliche Analysen des Gezeitenbereichs seit 2005 zeigen erstmals die saisonale und interannuelle Dynamik. Vermutlich Sturmereignisse im Winter 2006/07 haben die Deckschicht langjähriger Braunalgen von 100 auf ca. 20% dezimiert. Die Folgen für das System werden momentan analysiert. Im Vortrag werden die Entwicklungen beispielhaft aufgezeigt.

Description: 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.

Description: 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.