Challenges and difficulties in assessing the Environmental Status under the requirements of the Ecosystem Approach in North-African countries, illustrated by eutrophication assessment

Marine ecosystems provide many ecosystem goods and services. However, these ecosystems and the benefits they create for humans are subject to competing uses and increasing pressures. As a consequence of the increasing threats to the marine environment, several regulations require applying an ecosystem-based approach for managing the marine environment. Within the Mediterranean Sea, in 2008, the Contracting Parties of the Mediterranean Action Plan decided to progressively apply the Ecosystem Approach (EcAp) with the objective of achieving Good Environmental Status (GES) for 2018. To assess the Environmental Status, the EcAp proposes 11 Ecological Objectives, each of which requires a set of relevant indicators to be integrated. Progress towards the EcAp entails a gradual and important challenge for North-African countries, and efforts have to be initiated to propose and discuss methods. Accordingly, to enhance the capacity of North-African countries to implement EcAp and particularly to propose and discuss indicators and methods to assess GES, the aim of this manuscript is to identify the practical problems and gaps found at each stage of the Environmental Status assessment process. For this purpose, a stepwise method has been proposed to assess the Environmental Status using Ecologic Objective 5-Eutrophication as example.

Challenges and difficulties in assessing the Environmental Status under the requirements of the Ecosystem Approach in North-African countries, illustrated by eutrophication assessment

Marine ecosystems provide many ecosystem goods and services. However, these ecosystems and the benefits they create for humans are subject to competing uses and increasing pressures. As a consequence of the increasing threats to the marine environment, several regulations require applying an ecosystem-based approach for managing the marine environment. Within the Mediterranean Sea, in 2008, the Contracting Parties of the Mediterranean Action Plan decided to progressively apply the Ecosystem Approach (EcAp) with the objective of achieving Good Environmental Status (GES) for 2018. To assess the Environmental Status, the EcAp proposes 11 Ecological Objectives, each of which requires a set of relevant indicators to be integrated. Progress towards the EcAp entails a gradual and important challenge for North-African countries, and efforts have to be initiated to propose and discuss methods. Accordingly, to enhance the capacity of North-African countries to implement EcAp and particularly to propose and discuss indicators and methods to assess GES, the aim of this manuscript is to identify the practical problems and gaps found at each stage of the Environmental Status assessment process. For this purpose, a stepwise method has been proposed to assess the Environmental Status using Ecologic Objective 5-Eutrophication as example.

Long-term variability and environmental preferences of calycophoran siphonophores in the Bay of Villefranche (North-Western Mediterranean)

Long-term variability of the main calycophoran siphonophores was investigated between 1974 and 1999 in a coastal station in the north-western Mediterranean. The data were collected at weekly frequency using a macroplankton net (680 μm mesh size) adapted to quantitatively sample delicate gelatinous plankton. A 3-year collection (1967–1969) of siphonophores from offshore waters using the same methodology showed that the patterns of variability observed inshore were representative of siphonophores’ changes at a regional scale. The aims of the study were: (i) to investigate the patterns of variability that characterised the dominant calycophoran species and assemblages; (ii) to identify the environmental optima that were associated with a significant increase in the dominant siphonophore species and (iii) to verify the influence of hydroclimatic variability on long-term changes of siphonophores. Our results showed that during nearly 3 decades the standing stock of calycophoran siphonophores did not show any significant change, with the annual maximum usually recorded in spring as a result of high densities of the dominant species Lensia subtilis, Muggiaea kochi and Muggiaea atlantica. Nevertheless, major changes in community composition occurred within the calycophoran population. Since the middle 1980s, M. kochi, once the most dominant species, started to decrease allowing other species, the congeneric M. atlantica and Chelophyes appendiculata, to increasingly dominate in spring and summer–autumn, respectively. The comparison of environmental and biotic long-term trends suggests that the decrease of M. kochi was triggered by hydrological changes that occurred in the north-western Mediterranean under the forcing of large-scale climate oscillations. Salinity, water stratification and water temperature were the main hydroclimatic factors associated with a significant increase of siphonophores, different species showing different environmental preferences.

The effect of pressure on leucine and thymidine incorporation by free-living bacteria and by bacteria attached to sinking oceanic particles

The effect of pressure on upper ocean free-living bacteria and bacteria attached to rapidly sinking particles was investigated through studying their ability to synthesize DNA and protein by measuring their rate of 3H-thymidine and 3H-leucine incorporation. Studies were carried out on samples from the NE Atlantic under the range of pressures (1–430 atm) encountered by sinking aggregates during their journey to the deep-sea bed. Thymidine and leucine incorporation rates per bacterium attached to sinking particles from 200 m were about six and ten times higher, respectively, than the free-living bacterial assemblage. The ratio of leucine incorporation rate per cell to thymidine incorporation rate per cell was significantly different between the larger attached (18.9:1) and smaller free-living (10.4:1) assemblages. The rates of leucine and thymidine incorporation decreased exponentially with increasing pressure for the free-living and linearly for attached bacteria, while there was no significant influence of pressure on cell numbers. At 100 atm leucine and thymidine incorporation rate per free-living bacterium was reduced to 73 and 20%, respectively, relative to that measured at 1 atm. Pressure of 100 atm reduced leucine and thymidine incorporation per attached bacterium to 94 and 70%, and at 200 atm these rates were reduced to 34 and 51%, respectively, relative to those measured at 1 atm. There was no significant uncoupling of thymidine and leucine incorporation for either the free-living or attached bacterial assemblages with increasing pressure, indicating that the processess of DNA and protein synthesis may be equally affected by increasing pressure. It is therefore unlikely that bacteria, originating from surface waters, attached to rapidly sinking particles play a role in particle remineralization below approximately 1000–2000 m. These results may help to explain the occurrence of relatively fresh aggregates on the deep-sea bed that still contain sufficient organic carbon to fuel the rapid growth of benthic micro-organisms; they also indicate that the effect of pressure on microbial processes may be important in oceanic biogeochemical cycles.