m@rble ELectronic conference on MARine Biodiversity in Europe

Summary of day 2

Activity continued to increase with a larger number of new players in the discussion, as well as some progress towards the development of consensus. However, most of the activity was on topic #1, Large-scale patterns of marine biodiversity, which may reflect the fact that this is the first topic the participants encounter on the list.

1. Large-scale patterns of marine biodiversity

What are the large-scale patterns of marine biodiversity in Europe?

• The investigation of the relevant sample sizes to establish the species-area curves of marine organisms require samples ranging from cm¹s to hundreds of kilometers. There are few ­ if any ­ data sets that conform to the required spectrum of sample sizes, which is a main bottleneck to address the scale-dependence of marine biodiversity. At least one exploratory analysis of the scale-dependence of marine biodiversity, across the broadest possible range of scales, is necessary as a support to plan and interpret further research.
• In addition to other proxies, rendering the examination of large-scale marine biodiversity patterns opperational, the use of Functional groups may prove convenient. The relationship between species richness and the functional diversity of communities need be examined, as also stressed elsewhere in the discussion.
• Another link is to the discussion on the role of biodivesity under stationary - the scenario most commonly assumed in tests - and changing environmental conditions: To what extent do apparently redundant species may contribute to the resistence and resilience of ecosystem functions to change and disturbance? There are questions on this topic that can be addessed using planktonic organisms, such as shifts in the relative abundance of silicifiers versus calcifiers in ecological and geological time scales. Diatoms are large, tough, highly diverse and well suited to (physical) disturbance (mixing); coccolithophores are, on the other hand, small, and only outnumber diatoms in conditions of stability (stratified waters). Also, these organisms are available in the geological record (silicate/calcium carbonate sediments seem to be associated with glacial/interglacial periods). In this sense, we may argue that these may be good model organisms to elucidate questions such as (1) why are some marine (phytoplakton) groups more diverse than others in the modern oceans; and (2) how can we explain the lower degree of (genetic) diversity in freshwater ecosystems compared to marine ecosystems (diatom scenario)?

Global pattern and european patterns:

• Some global patterns on species diversity have been already elucidated, such as clear cline of increasing species richness from Arctic to ca 20oN, and the fact that tropics are NOT necessarily richest (see Roy & Jablonski's and Crame's data). The pattern in the southern hemisphere is far less clear as we have relatively little data. There is also little doubt that Indonesia has the highest species richness with radial declines from there, but there are "hot-spots" of high richness that occur elsewhere and need explanation. Yet, we are lacking comparable patterns within basins or sub-basins. The reason for that is that the differences are not as great as those present globally, requiring, therefore, high precission data to resolve them.
• Taxonomic distinctness may be difficult to compare across taxonomically heterogeneous groups. These limitations can be circunvented if we use a consistent taxonomy in each case.
• Beta diversity should be taken into account in addition to alpha and gamma diversity when measuring biodiversity over large spatial scales. Beta diversity may be measured as differences in faunal composition between sites or areas, and can be related to spatial distance and environmental variability. The difficulty lies in deciding what indices of beta diversity should we use?
• The concerted action BIOMARE has proposed a pragmatic approach towards the elucidation of large scale patterns in European marine biodiversity that may inspire additional efforts elsewhere. A set of Primary Reference sites throughout Europe has been proposed to establish comprehensive All Taxon Biodiversity Inventories (ATBIs), which might enable us to calibrate the relationship between overall biodiversity and the diversity of key taxa or biodiversity indicators. Using these biodiversity 'surrogates' or 'indicators', we may then be able to establish patterns of biodiversity on a finer spatial scale at a larger number of reference sites. This initiative is an important step forward to render a complex question opperational: by selecting protected areas as the target there may be hope to separate the "background" large scale patterns of large scale biodiversity from effects derived from local anthropogenic forcing. Once the "pristine" (i.e. as pristine as possible) conditions have been described we may investigate how these may have been affected by "point source" anthropogenic effects.

2. Biogeochemical cycling and ecosystem functioning

What is the function of biodiversity in biogeochemical cycling and ecosystem functioning?

• The large number of parasitic species itself indicates their important role in the aquatic and terrestrial communities. The place and role of parasitic system in the concrete ecosystem depends on its structure. The parasite system can carry out the regulatory, protective and stabilizing functions, function of energy transmission in ecosystems.