Michael L. Zettler

Status of Biodiversity in the Baltic Sea

The brackish Baltic Sea hosts species of various origins and environmental tolerances. These immigrated to the sea 10,000 to 15,000 years ago or have been introduced to the area over the relatively recent history of the system. The Baltic Sea has only one known endemic species. While information on some abiotic parameters extends back as long as five centuries and first quantitative snapshot data on biota (on exploited fish populations) originate generally from the same time, international coordination of research began in the early twentieth century. Continuous, annual Baltic Sea-wide long-term datasets on several organism groups (plankton, benthos, fish) are generally available since the mid-1950s. Based on a variety of available data sources (published papers, reports, grey literature, unpublished data), the Baltic Sea, incl. Kattegat, hosts altogether at least 6,065 species, including at least 1,700 phytoplankton, 442 phytobenthos, at least 1,199 zooplankton, at least 569 meiozoobenthos, 1,476 macrozoobenthos, at least 380 vertebrate parasites, about 200 fish, 3 seal, and 83 bird species. In general, but not in all organism groups, high sub-regional total species richness is associated with elevated salinity. Although in comparison with fully marine areas the Baltic Sea supports fewer species, several facets of the systems diversity remain underexplored to this day, such as micro-organisms, foraminiferans, meiobenthos and parasites. In the future, climate change and its interactions with multiple anthropogenic forcings are likely to have major impacts on the Baltic biodiversity.

INVASION OF THE NORTH AMERICAN AMPHIPOD (GAMMARUS TIGRINUS SEXTON, 1939) INTO THE CURONIAN LAGOON, SOUTH-EASTERN BALTIC SEA

The North American amphipod (Gammarus tigrinus Sexton, 1939) was found in the Lithuanian part of the Curonian Lagoon in September 2004. In the littoral part, the distribution of the species was restricted to the area of seawater inflows, within a distance of up to 23 km upstream from the sea. The species was present in all types of the habitats sampled (reeds, mixed and soft bottoms) and its distribution showed a continuous rather than fragmented pattern. In most cases, the species was absent in enclosed depositional environments with mixed substrates and the presence of mud. Obessogammarus crassus (G. O. Sars) was the only crustacean species always found in the presence of the new invader G. tigrinus, whereas other species showed a higher degree of habitat discrimination within the stations. Along with the other two introduced crustaceans O. crassus and Pontogammarus robustoides (G. O. Sars), G. tigrinus showed the highest occurrence (79%) in the salinity range of its recent distribution in the lagoon. A...

On the Myths of Indicator Species : Issues and Further Consideration in the Use of Static Concepts for Ecological Applications

The use of static indicator species, in which species are expected to have a similar sensitivity or tolerance to either natural or human-induced stressors, does not account for possible shifts in tolerance along natural environmental gradients and between biogeographic regions. Their indicative value may therefore be considered at least questionable. In this paper we demonstrate how species responses (i.e. abundance) to changes in sediment grain size and organic matter (OM) alter along a salinity gradient and conclude with a plea for prudency when interpreting static indicator-based quality indices. Six model species (three polychaetes, one amphipod and two bivalves) from the North Sea, Baltic Sea and the Mediterranean Sea region were selected. Our study demonstrated that there were no generic relationships between environment and biota and half of the studied species showed different responses in different seas. Consequently, the following points have to be carefully considered when applying static indicator-based quality indices: (1) species tolerances and preferences may change along environmental gradients and between different biogeographic regions, (2) as environment modifies species autecology, there is a need to adjust indicator species lists along major environmental gradients and (3) there is a risk of including sibling or cryptic species in calculating the index value of a species.

Biodiversity gradient in the Baltic Sea: a comprehensive inventory of macrozoobenthos data

Abstract In the Helsinki Commission Red List project 2009–2012, taxonomic and distributional data of benthic (macro) invertebrates were compiled by the present authors in a comprehensive checklist of the Baltic Sea fauna. Based on the most recent and comprehensive data, this paper presents the diversity patterns observed among benthic invertebrates in the Baltic Sea. As expected, the total number of species per sub-region generally declined along the salinity gradient from the Danish Straits to the northern Baltic Sea. This relationship is well known from the Baltic Sea and has resulted in a general assumption of an exponentially positive relationship between species richness and salinity for marine species, and a negative relationship for freshwater species. In 1934, Remane produced a diagram to describe the hypothetical distribution of benthic invertebrate diversity along a marine–freshwater salinity gradient. Our results clearly indicated the validity of this theory for the macrozoobenthic diversity pattern within the Baltic Sea. Categorisation of sub-regions according to species composition showed both separation and grouping of some sub-regions and a strong alignment of similarity patterns of zoobenthic species composition along the salinity gradient.

History and Success of an Invasion into the Baltic Sea: The Polychaete Marenzelleria cf. Viridis, Development and Strategies

In the mid 1980s, a new polychaete appeared in coastal waters of the Baltic Sea and rapidly became an important faunistic element. The identification of this spionid as Marenzelleria cf. viridis indicated North America as the most likely area of origin. The history of invasion into the Baltic Sea is outlined. Sound taxonomic experience and competence was and is necessary to elucidate the background when dealing with bioinvasions. A review of taxonomic problems of the genus Marenzelleria is given. Based on long time series we could draw a picture on the species strategy in stressed habitats. Three coastal areas were selected to demonstrate the role of environmental factors facilitating Marenzelleria invasion in the Baltic Sea in the last decade. This review deals with the expansion and niching of an allochthonous species and its influence on the indigenous macrozoobenthos. Both the life history and physiology of Marenzelleria make it well adapted to life in brackish water conditions, occupying a niche in an environment with low species diversity.

Variation in the reproductive status, larval occurrence and recruitment in an estuarine population ofMarenzelleria viridis(Polychaeta: Spionidae)

Since its immigration in 1985, the spionid polychaete Marenzelleria viridis (Verrill, 1873) has become a major element of the fauna in the Darss-Zingst Bodden Chain, a tideless estuary-like coastal...

Biotope map of the German Baltic Sea

Full-coverage maps on the distribution of marine biotopes are a necessary basis for Nature Conservation and Marine Spatial Planning. Yet biotope maps do not exist in many regions. We are generating the first full-coverage biotope map for the German Baltic Sea according to the HELCOM Underwater biotope and habitat classification system (HUB). Species distribution modelling is applied to create full-coverage spatial information of biological features. The results of biomass modelling of twelve target taxa and presence/absence modelling of three target taxa enabled the identification of biological levels up to HUB level 6. Environmental data on bathymetry, light penetration depth and substrate are used to identify habitat levels. HUB biotope levels were combined with HUB habitat levels to create a biotope map. Altogether, 68 HUB biotopes are identified in the German Baltic Sea. The new biotope map combining substrate characteristics and biological communities will facilitate marine management in the area.

Macrozoobenthic biodiversity patterns in the northern province of the Benguela upwelling system

This paper describes macrozoobenthos diversity in the vicinity of the Angola–Benguela Frontal Zone between 15° and 23° S in offshore waters of the Namib biogeographic province in a comprehensive zoogeographical context. At 38 selected stations, about 500 different macrozoobenthic taxa could be identified, including 209 bivalve, gastropod and peracarid species. These 209 taxa were reduced to 85 species by statistical procedures, to ensure the database was reliable in terms of statistics and taxonomy for community analysis. The evaluation of macrobenthic distribution patterns revealed three distinct biodiversity clusters, which are probably the result of different adaptation strategies to the diverse environmental conditions within the Benguela upwelling ecosystem. The dominating driver for benthic diversity is the extent of the oxygen minimum zone (OMZ). Temporal and spatial stability of the OMZ is, however, not fixed. Therefore, only the particular spatial pattern in total community structure during the cruises can be described in this study. Perennial temporal variability in the extent of OMZs can, however, be assessed by the distribution of longer-living molluscs’ shells. The assignment of macrofauna communities to recent patterns of frontal systems, upwelling cores and oxygen supply makes the hard-shell fraction of the communities a potential indicator of historic changes in these external conditions.

The Impact of Wind Engine Constructions on Benthic Growth Patterns in the Western Baltic

Global-scale environmental degradation and its association with nonrenewable fossil fuels have led to an increasing interest in generation of electricity by renewable energy resources (Gill 2005). Since the planning of large offshore wind energy facilities in the German Bight and the Baltic Sea was initiated, concerns about the ecological compatibility of these structures have been expressed. Apart from direct impacts of disturbance during construction, operational sounds and rotating parts, which might primarily affect birds, bats, marine mammals and fish, the potential long term effects on the benthic environment have been discussed. These concerns are mainly focused on the questions, whether and how the natural benthic habitat in the vicinity of the constructions is modified by changes in bottom currents and turbulence, and whether the effects of the installations as artificial settling substrates are properly assessed. The ecologically relevant effects of offshore wind parks include e.g., increased habitat heterogeneity, and changes in hydrodynamic conditions and in sediment transport patterns. The potential ecological response of the macrozoobenthos could involve long-term changes in diversity, abundance, biomass, community structure and such functional properties as nutrient regeneration or bio-turbation. These problems have been in the focus of a project in the western Baltic which that was part of a national combination of projects called BeoFINO.1 This effort has addressed the overall ecological risks of offshore wind-power facilities in the North and Baltic Seas. Such questions are most often viewed in the primary context of the effects on the biodiversity of the benthic community. In the Baltic Sea however, the specific hydrographical conditions emphasizes a problem which also involves the absolute biomass accumulation rates of epifauna

Verifying a biotope classification using benthic communities – An analysis towards the implementation of the European Marine Strategy Framework Directive

The HELCOM Red List biotopes project proposed a Baltic Sea wide classification consisting of six levels: The HELCOM Underwater biotopes/habitats classification system (HELCOM HUB). We present a case study from the south-western Baltic Sea where we tested the applicability of this system. More than 500 sampling stations were analyzed regarding macrozoobenthic communities and their linkage to environmental parameters. Based on the analyses of biotic and abiotic data, 21 groups were assigned to 13 biotopes of the classification. For some biotopes varying states of communities were recognized. Even though not all abiotic parameters are considered directly in the hierarchy of the classification in general, all soft-bottom communities could be allocated to a corresponding biotope. The application of the HELCOM HUB for the south-western Baltic Sea is feasible, in regard to the implementation of the European Marine Strategy Framework Directive as well as the Baltic Sea Action Plan.