Laurent Godet

Considering the functional value of common marine species as a conservation stake: the case of sandmason worm Lanice conchilega (Pallas 1766) (Annelida, Polychaeta) beds.

Abstract Conservation of the marine environment mainly focuses on threatened elements and more precisely on vulnerable and endangered species like birds and mammals. When dealing with the conservation of marine habitats, the scientific community is mainly interested in hot spots of diversity, like seagrass beds in Europe, or hot spots of endemism, like coral reefs in tropical areas. Nevertheless, using the example of a common and widespread marine invertebrate, the sandmason worm (Lanice conchilega, Polychaeta, Terebellidae), we show that vulnerability and rarity are not the only criteria to take into account in order to select the best natural element for conservation. This species can form dense beds that increase biodiversity, are attractive feeding grounds for birds and fishes, and have a high socioeconomic value. In consequence, they have a high functional value that should be considered as an important conservation stake. Through the example of the Chausey archipelago and the Bay of the Mont Saint-Michel (France), we propose a synthetic interdisciplinary approach to evaluate the conservation needs of these beds. The issue is even more pressing when one considers that these natural elements and many similar ones still do not benefit from any legal protection in Europe despite their high heritage value.

Clam farmers and Oystercatchers: effects of the degradation of Lanice conchilega beds by shellfish farming on the spatial distribution of shorebirds.

The Manila clam Ruditapes philippinarum cultivation is an original shellfish farming activity strongly mechanized. In the Chausey archipelago (France) this activity settles on the Lanice conchilega beds, habitat known to host a rich and diversified benthic macrofauna and which is an attractive feeding ground for birds. A first study highlighted that this activity had strong negative effects on the L. conchilega beds and their associated benthic macrofauna. Here we assess the impacts of such an activity on the Eurasian Oystercatcher Haematopus ostralegus for which Chausey is one of the most important national breeding sites and which is also a common species in winter, spring and autumn migrations. We found that Oystercatchers significantly selected the L. conchilega beds to feed and that their spatial distribution was significantly modified after the creation of new clam concessions. In a context of a growing disappearance of pristine coastal ecosystems for the benefit of anthropo-ecosystems, we discuss the problem of the degradation of such benthic habitats with a low resilience which may loose their high functional value.

Waders in winter: long-term changes of migratory bird assemblages facing climate change.

Effects of climate change on species occupying distinct areas during their life cycle are still unclear. Moreover, although effects of climate change have widely been studied at the species level, less is known about community responses. Here, we test whether and how the composition of wader (Charadrii) assemblages, breeding in high latitude and wintering from Europe to Africa, is affected by climate change over 33 years. We calculated the temporal trend in the community temperature index (CTI), which measures the balance between cold and hot dwellers present in species assemblages. We found a steep increase in the CTI, which reflects a profound change in assemblage composition in response to recent climate change. This study provides, to our knowledge, the first evidence of a strong community response of migratory species to climate change in their wintering areas.

Does Manila clam cultivation affect habitats of the engineer species Lanice conchilega (Pallas, 1766)?

The major French site of Manila clam Ruditapes philippinarum (Adams and Reeves, 1850) cultivation is located in the Chausey Archipelago where the associated practices are highly mechanized: every steps of production are made with tractor-driven machinery. The Manila clam concessions are concentrated on Lanice conchilega (Pallas, 1766) bioherms, which are known to increase alpha-diversity and to locally modify sediment dynamics. This study focus on the impacts of Manila clam cultivation on (i) the natural populations of L. conchilega and on (ii) the structure of the associated benthic assemblages during the different steps of the farming production cycle. We found that the L. conchilega populations are significantly affected within the concessions where their total abundances drastically decrease, their spatial patterns are modified and the associated benthic assemblages are significantly altered. Our results are discussed in a context of a sustainable management of the Manila clam cultivation in coastal areas.

Ephemeral Bio-engineers or Reef-building Polychaetes: How Stable are Aggregations of the Tube Worm Lanice conchilega (Pallas, 1766)?

Dense aggregations of tube-worms can stabilize sediments and generate oases for benthic communities that are different and often more diverse and abundant than those of the surroundings. If these features are to qualify as biogenic reefs under nature-conservation legislation such as the EC Habitats Directive, a level of stability and longevity is desirable aside from physical and biological attributes. Lanice conchilega (Pallas, 1766) is widely distributed around the European coast and aggregations of this tube-dwelling polychaete are known to have a positive effect on the biodiversity of associated species in inter- and sub-tidal areas. This increases the value of L. conchilega-rich habitats for higher trophic levels such as birds and fish. However, L. conchilega is currently not recognized as a reef builder primarily due to uncertainty about the stability of their aggregations. We carried out three studies on different spatial and temporal scales to explore a number of properties relating to stability: (1) Individual aggregations of L. conchilega of ∼1 m(2) were monitored for up to 1 year, (2) records of L. conchilega from a 258-ha area over a 35-year period were analyzed, (3) the recovery of a population of L. conchilega subjected to disturbances by cultivation of Manila clams (Ruditapes philippinarum) was followed over 3 years. The studies provided evidence about the longevity of L. conchilega aggregations, their resistance to disturbance, their resilience in recovering from negative impact and their large-scale persistence. The results showed that populations of L. conchilega were prone to considerable fluctuation and the stability of aggregations depended on environmental factors and on recruitment. The tube-worms proved to be susceptible to disturbance by cultivation of Manila clams but demonstrated the potential to recover from that impact. The long-term monitoring of a large L. conchilega population in the Bay of Mont Saint Michel (France) indicated that aggregations can persist over many decades with a constant, densely populated core area and an expanding and contracting more thinly populated fringe zone. The stability of aggregations of L. conchilega and the structures they form do not unequivocally fit the currently accepted definition of a reef. However, given L. conchilegas accepted reef-like potential to influence diversity and abundance in benthic communities, we suggest clarifying and expanding the definition of reefs so that species with records of significant persistence in particular areas and which otherwise meet expectations of reefs are included within the definition.

Estimating relative population size included within protected areas

We propose and test a method to determine the proportion of specific animal national populations included in a network of protected areas. The proposed method further allows identifying the best potential new sites to be included in the network, to reach target population sizes and so to test whether a network extension is realistic or not. We used data from the French Breeding Bird Survey (BBS) and spatial interpolation models known as kriging to predict the relative abundance of species at a national scale. We applied the proposed methodology to Special Protection Areas (SPAs) and a sample of 20 bird species concerned by the Directive of the Council of the European Community on the Conservation of Wild Birds. We estimated which relative part of the national population is included within the boundaries of all national SPAs. Our results suggest that the current SPA network is probably not efficient to ensure favorable national conservation status for the most widespread species, but allows reaching a 5% target value for more localized ones. Consequently, we discuss the limit of such a protected area network to ensure the global conservation of widespread species, and therefore the need for other large-scale conservation measures.

Latitudinal Patterns in European Seagrass Carbon Reserves: Influence of Seasonal Fluctuations versus Short-Term Stress and Disturbance Events

Seagrass meadows form highly productive and valuable ecosystems in the marine environment. Throughout the year, seagrass meadows are exposed to abiotic and biotic variations linked to (i) seasonal fluctuations, (ii) short-term stress events such as, e.g., local nutrient enrichment, and (iii) small-scale disturbances such as, e.g., biomass removal by grazing. We hypothesized that short-term stress events and small-scale disturbances may affect seagrass chance for survival in temperate latitudes. To test this hypothesis we focused on seagrass carbon reserves in the form of starch stored seasonally in rhizomes, as these have been defined as a good indicator for winter survival. Twelve Zostera noltei meadows were monitored along a latitudinal gradient in Western Europe to firstly assess the seasonal change of their rhizomal starch content. Secondly, we tested the effects of nutrient enrichment and/or biomass removal on the corresponding starch content by using a short-term manipulative field experiment at a single latitude in the Netherlands. At the end of the growing season, we observed a weak but significant linear increase of starch content along the latitudinal gradient from south to north. This agrees with the contention that such reserves are essential for regrowth after winter, which is more severe in the north. In addition, we also observed a weak but significant positive relationship between starch content at the beginning of the growing season and past winter temperatures. This implies a lower regrowth potential after severe winters, due to diminished starch content at the beginning of the growing season. Short-term stress and disturbances may intensify these patterns, because our manipulative experiments show that when nutrient enrichment and biomass loss co-occurred at the end of the growing season, Z. noltei starch content declined. In temperate zones, the capacity of seagrasses to accumulate carbon reserves is expected to determine carbon-based regrowth after winter. Therefore, processes affecting those reserves might affect seagrass resilience. With increasing human pressure on coastal systems, short- and small-scale stress events are expected to become more frequent, threatening the resilience of seagrass ecosystems, particularly at higher latitudes, where populations tend to have an annual cycle highly dependent on their storage capacity.

The influence of salina landscape structures on terrestrial bird distribution in the Guérande basin (Northwestern France)

Capsule The salinas of the Guérande basin show highly fragmented landscapes that significantly structure the distribution of terrestrial birds. Aim To test the potential influence of landscape structures of a fragmented landscape on the distribution of terrestrial birds. Methods The salinas were mapped using a Geographical Information System and landscape metrics were calculated to quantify landscape structures. Birds were surveyed with a point count method. Multivariate analyses and multiple linear regressions were used to test for potential links between landscape metrics and bird distribution. Results The landscape structures of the salinas influenced bird assemblages significantly. The core of the salinas, with more-fragmented and less-diverse landscapes, contained the lowest abundance, richness and diversity of birds, but this assemblage tended to be homogeneous and distinct. Bird abundance, richness and diversity mainly increased with landscape richness and diversity, the terrestrial area available and the proximity to the continental domain. Conclusion This study is the first to demonstrate and quantify the influence of salina landscape structures on terrestrial bird assemblages.

Old and unmowed saltmarsh patches provide attractive habitats for breeding passerines

Although the conservation stakes of saltmarshes are widely documented, these areas are still subjected to strong anthropic pressures, including land reclamation, leading to their conversion into arable lands, and agricultural exploitation (mainly cattle grazing and mowing), which modifies their floral and faunal composition. Through the example of one of the largest French saltmarshes, we first assessed how the age of the saltmarsh patches and the mowing intensity determined the spatial distribution of the different saltmarsh habitats. We then tested how the five commonest breeding passerines were distributed in accordance with the mowing activity and the distribution of these habitats. We found that the oldest and the unmowed patches promote the development of habitats dominated by Elymus pungens and Atriplex portulacoides, and also host the highest abundance of four of the five bird species studied. In the current context of an intense artificialization of the littoral area, this study highlights the importance of maintaining the oldest and the least human-impacted patches of natural habitats to conserve their associated biodiversity.

Extreme Landscapes Decrease Taxonomic and Functional Bird Diversity but Promote the Presence of Rare Species

Abstract. Human activities may generate geometrical landscape (i.e. composed of rectilinear and repetitive landscape units) structures that can significantly influence the spatial distribution of birds. While bird distribution in various landscape types has been extensively studied, the role played by landscape configuration and composition in different facets of bird diversity remains unclear. Here, these two main components of landscape characteristics (i.e. configuration and composition) are disentangled and their relative influence on three different facets of bird assemblages: taxonomic and functional characteristics, and the presence of rare species, is tested. We chose four large coastal salinas of Western France as a relevant model of geometrical and human-dominated landscapes where each landscape unit can be easily identified and mapped. The landscape characteristics of these sites were mapped and quantified. Then, terrestrial breeding birds were sampled in 172 point-counts using a standardized protocol. 69 diurnal terrestrial bird species were detected and considered in analyses (waterbirds and owls excluded). Landscape composition was found to have a higher influence on bird communities than landscape configuration, which fits with the “landscape composition hypothesis”. More specifically, the most “extreme” landscapes — those with low terrestrial surface areas, low landscape richness and diversity, low cohesion, and very patchy landscapes with complex geometrical shapes — host the lowest bird taxonomic abundance, richness and diversity and functional richness, but are characterized by the presence of rare species (mainly wetland specialist species, e.g. Reed Bunting Emberiza schoeniclus and species with restricted ranges e.g. Bluethroat Luscinia svecica namnetum). Our results suggest that conservation plans in such geometrical and human-dominated habitats should not only focus on one aspect of landscape characteristics or one aspect of biological diversity but also consider the adverse effects of landscape characteristics on these different facets.